WikiVet English - User contributions [en]

Nasal Cavity - Anatomy & Physiology

2008-10-01T13:29:58Z

Rmacharia: /* Introduction */

{{review}}

{{toplink
|backcolour = D1EEEE
|linkpage =Cardiorespiratory System - Anatomy & Physiology
|linktext =CARDIORESPIRATORY SYSTEM
|maplink = Cardiorespiratory System (Content Map) - Anatomy & Physiology
|pagetype =Anatomy
}}
 
[[Image:Nasal Cavities.jpg|thumb|right|300px|Nasal Cavities - Copyright David Bainbridge]]
==Introduction==

The respiratory tract begins with the ''nose'' which includes the external nose, internal nasal cavities and [[Paranasal sinuses - Anatomy & Physiology|paranasal sinuses]].
As well as being vital for transport of gases to the [[Cardiorespiratory System - Anatomy & Physiology#Lower Respiratory Tract|lower respiratory tract]], the nasal cavity is also the site for one of the special senses - [[Special Senses - Olfactory - Anatomy & Physiology|''Olfaction'']].

==Structure==

*The nose consists of the external nares with nasal [[Bones and Cartilage - Anatomy & Physiology#Structure and Function of Cartilage|cartilages]], the nasal cavity (including the nasal meatus and conchae), and the [[Paranasal sinuses - Anatomy & Physiology|paranasal sinuses]].

*The nasal cavity is essentially a tube with a wall established by several [[Skull and Facial Muscles - Anatomy & Physiology#Bones of the Skull|bones of the skull]]. The borders of the nasal cavity are as follows:

- ''Caudal'': cribrifrom plate of the [[Skull and Facial Muscles - Anatomy & Physiology#Ethmoid Bone (os ethmoidale)|ethmoid bone]]

- ''Ventral'': continuous with the nasopharynx

- ''Dorsal'': the maxilla and the palatine processes of the [[Skull and Facial Muscles - Anatomy & Physiology#Incisive Bone (os incisivium)|incisive bone]]

*Rostrally, the median septum is a continuation of the [[Skull and Facial Muscles - Anatomy & Physiology#Ethmoid Bone (os ethmoidale)|ethmoid bone]]. The median septum is made up of [[Bones and Cartilage - Anatomy & Physiology#Hyaline Cartilage|hyaline cartilage]], and divides the nasal cavity into left and right halves.

[[Image:DogHeadDissection.jpg|right|thumb|200px|The nasal cavity can be seen filled with conchae in this photograph of a canine head. ©Nottingham 2008]]

*The nasal cavity is occupied to a large extent by '''''Nasal conchae'''''. These are turbinate bones which project into the nasal cavity with the purpose of supporting the [[Special Senses - Olfactory - Anatomy & Physiology|olfactory]] mucus membranes and increasing the respiratory surface area, creating turbulence within the passing air. This helps to filter, warm or cool the air that passes through.

*The Conchae are [[Bones and Cartilage - Anatomy & Physiology#Types of Cartilage|cartilage]]nous or ossified scrolls which arise from the [[Skull and Facial Muscles - Anatomy & Physiology#Ethmoid Bone (os ethmoidale|''ethmoid bone'']]. They are covered with mucous membrane, under which is a layer of anastomosing blood vessels.
The nasal conchae are more complex in animals with a better sense of smell, as they increase the surface area of the [[Special Senses - Olfactory - Anatomy & Physiology|Olfactory]] region, further.

*There are dorsal and ventral conchae, the dorsal concha originating from the [[Skull and Facial Muscles - Anatomy & Physiology#Ethmoid Bone (os ethmoidale)|ethmoid bone]] and attaching to the maxilla, and the vental conchae originating from the [[Skull and Facial Muscles - Anatomy & Physiology#Maxilla|maxilla]] and extending further into the nasal cavity.

*The conchae divide the nasal cavity into nasal ducts or ''meatuses'', which branch out from a common nasal meatus which is adjacent to the nasal septum. There are three nasal meatuses which branch from the common nasal meatus: dorsal, middle and ventral:

- '''Dorsal nasal meatus''': the passage between the roof of the nasal cavity and the dorsal nasal concha

- '''Middle nasal meatus''': between the dorsal and ventral conchae, and communicates with the [[Paranasal sinuses - Anatomy & Physiology|paranasal sinuses]].

- '''Ventral nasal meatus''': the main pathway for airflow leading to the pharynx, and is positioned between the ventral nasal concha and the floor of the nasal cavity.

- '''Common nasal meatus''': the longitudinal space on either side of the nasal septum.

*The [[Paranasal sinuses - Anatomy & Physiology|Paranasal Sinuses]] are extensions of the nasal cavity.

==Function==

*In addition to [[Special Senses - Olfactory - Anatomy & Physiology|Olfaction,]] the function of the nasal cavity is to modify the incoming air before is is transported further down the respiratory tract.
*Air is warmed as it passes over the highly vascularised mucosal surfaces of the conchae, humidified by the evaporation from nasal secretion and cleaned as it contacts the secretion from mucus glands within the nasal cavity. The mucus secreted from the glands traps particles and cilia transport them down to the pharynx for swallowing, this process is known as the [[Respiratory Epithelium - Anatomy & Physiology#Mucociliary Escalator|Mucociliary Escalator]].
*The nasal cavity offers further protection via the Sneezing reflex .

==Species Differences==

*The nasal cavity in the '''sheep''' is highly vascularised, with any damage to the epithelium resulting in severe [[General Pathology - Haemorrhage|haemorrhage]].
*'''Cattle''' have a smaller nasal cavity compared to the horse.
*There are many variations to the entire [[Avian Respiration - Anatomy & Physiology|'''Avian''' respiratory tract]].
*The [[Respiration in Non-Homeotherms - Anatomy & Physiology|Respiratory Systems of non-Homeotherms]] are also very different to that of mammals.

==Links==

*[[Nasal Cavity - Pathology]]

Cardiorespiratory System Overview - Anatomy & Physiology

2008-10-01T13:25:22Z

Rmacharia: /* Introduction */

{{review}}
{{toplink
|thispagenormal = Cardiorespiratory System - Anatomy & Physiology
|thispagemap = Cardiorespiratory System (Content Map) - Anatomy & Physiology
|pagetype =Anatomy
}}
 
==Introduction==
[[Image:Routeofairthroughrespiratorysystem.jpg|right|thumb|200px|'''Schematic Diagram showing the route air takes through the respiratory system''']]

The mammalian cardiovascular and respiratory systems have evolved primarily to provide the tissues of the body with oxygen and to remove carbon dioxide. The cardiorespiratory system also has metabolic and heat exchange roles.

===Respiratory System===

Air is [[Ventilation - Anatomy & Physiology|inhaled]] and passes through the upper respiratory tract (nares, [[Nasal cavity - Anatomy & Physiology|nasal cavity]], [[Nasopharynx - Anatomy & Physiology|nasopharynx]], [[Larynx - Anatomy & Physiology|larynx]], [[Trachea - Anatomy & Physiology|trachea]]) where it is heated and moistened. It then passes to the lower respiratory tract ([[Bronchi and bronchioles - Anatomy & Physiology|bronchi, bronchioles]], [[Lungs - Anatomy & Physiology|alveoli]]) where oxygen diffuses across the alveolar wall and into the blood, forming oxyhaemoglobin.

===Cardiovascular System===

Blood, which has been oxygenated by the [[Lungs - Anatomy & Physiology|lungs]], flows through the pulmonary vein to the left atrium of the heart and subsequently to the left ventricle from which it is ejected by the heart during ventricular systole. Oxygenated blood is then distributed to the different parts of the body via the aorta. The distribution of blood is controlled by vascular tone which dictates the degree of perfusion of capillary beds and therefore the amount of oxygen available to the various tissues. Carbon dioxide produced from cellular respiration is removed from the tissues and transported either attached to proteins, in solution or as bicarbonate via the venous system to the vena cavae and ultimately to the right atrium. The passage of venous blood is a product of blood flow, vascular valves and muscular and respiratory function. Carbon dioxide rich blood enters the right ventricle and is then pumped to the lungs via the pulmonary artery.

===Integration===

The function of the cardiac and respiratory systems are tightly linked and regulated to maintain blood pressure, tissue oxygen delivery and carbon dioxide removal. Cardiac function is controlled by baroreceptors (pressure receptors) which result in changes to the heartrate, contractility and vascular tone. Respiratory function is controlled centrally by chemoreceptors to maintain rate and both centrally and locally to maintain bronchiolar tone.

==Upper Respiratory Tract==

[[Nasal cavity - Anatomy & Physiology|Nasal Cavity]]

[[Paranasal sinuses - Anatomy & Physiology|Paranasal Sinuses]]

[[Pharynx - Anatomy & Physiology|Pharynx]]

[[Guttural pouches - Anatomy & Physiology|Guttural Pouches]]

[[Larynx - Anatomy & Physiology|Larynx]]

[[Trachea - Anatomy & Physiology|Trachea]]

==Lower Respiratory Tract==

[[Bronchi and bronchioles - Anatomy & Physiology|Bronchi & Bronchioles]]

[[Lungs - Anatomy & Physiology|Anatomy of the Lungs]]

[[Ventilation - Anatomy & Physiology|Ventilation]]

[[Gas Exchange - Anatomy & Physiology|Gas Exchange]]

[[Pleural cavity and membranes - Anatomy & Physiology|Pleural Cavity & Membranes]]

==Cardiovascular System==

[[Heart - Anatomy & Physiology|Heart]]

[[Vascular System - Anatomy & Physiology|Vascular System]]

==Acknowledgements and Reference Material==
*[[References for the Cardiorespiratory system - Anatomy & Physiology| References]]
*'''Creators:'''
**[[Jo Hinsley]]
**[[Carolyn Harvey-Myers]]

Cardiorespiratory System Overview - Anatomy & Physiology

2008-10-01T13:24:10Z

Rmacharia: /* Introduction */

{{review}}
{{toplink
|thispagenormal = Cardiorespiratory System - Anatomy & Physiology
|thispagemap = Cardiorespiratory System (Content Map) - Anatomy & Physiology
|pagetype =Anatomy
}}
 
==Introduction==
[[Image:Route of air through respiratory system.jpg|right|thumb|200px|'''Schematic Diagram showing the route air takes through the respiratory system''']]

The mammalian cardiovascular and respiratory systems have evolved primarily to provide the tissues of the body with oxygen and to remove carbon dioxide. The cardiorespiratory system also has metabolic and heat exchange roles.

===Respiratory System===

Air is [[Ventilation - Anatomy & Physiology|inhaled]] and passes through the upper respiratory tract (nares, [[Nasal cavity - Anatomy & Physiology|nasal cavity]], [[Nasopharynx - Anatomy & Physiology|nasopharynx]], [[Larynx - Anatomy & Physiology|larynx]], [[Trachea - Anatomy & Physiology|trachea]]) where it is heated and moistened. It then passes to the lower respiratory tract ([[Bronchi and bronchioles - Anatomy & Physiology|bronchi, bronchioles]], [[Lungs - Anatomy & Physiology|alveoli]]) where oxygen diffuses across the alveolar wall and into the blood, forming oxyhaemoglobin.

===Cardiovascular System===

Blood, which has been oxygenated by the [[Lungs - Anatomy & Physiology|lungs]], flows through the pulmonary vein to the left atrium of the heart and subsequently to the left ventricle from which it is ejected by the heart during ventricular systole. Oxygenated blood is then distributed to the different parts of the body via the aorta. The distribution of blood is controlled by vascular tone which dictates the degree of perfusion of capillary beds and therefore the amount of oxygen available to the various tissues. Carbon dioxide produced from cellular respiration is removed from the tissues and transported either attached to proteins, in solution or as bicarbonate via the venous system to the vena cavae and ultimately to the right atrium. The passage of venous blood is a product of blood flow, vascular valves and muscular and respiratory function. Carbon dioxide rich blood enters the right ventricle and is then pumped to the lungs via the pulmonary artery.

===Integration===

The function of the cardiac and respiratory systems are tightly linked and regulated to maintain blood pressure, tissue oxygen delivery and carbon dioxide removal. Cardiac function is controlled by baroreceptors (pressure receptors) which result in changes to the heartrate, contractility and vascular tone. Respiratory function is controlled centrally by chemoreceptors to maintain rate and both centrally and locally to maintain bronchiolar tone.

==Upper Respiratory Tract==

[[Nasal cavity - Anatomy & Physiology|Nasal Cavity]]

[[Paranasal sinuses - Anatomy & Physiology|Paranasal Sinuses]]

[[Pharynx - Anatomy & Physiology|Pharynx]]

[[Guttural pouches - Anatomy & Physiology|Guttural Pouches]]

[[Larynx - Anatomy & Physiology|Larynx]]

[[Trachea - Anatomy & Physiology|Trachea]]

==Lower Respiratory Tract==

[[Bronchi and bronchioles - Anatomy & Physiology|Bronchi & Bronchioles]]

[[Lungs - Anatomy & Physiology|Anatomy of the Lungs]]

[[Ventilation - Anatomy & Physiology|Ventilation]]

[[Gas Exchange - Anatomy & Physiology|Gas Exchange]]

[[Pleural cavity and membranes - Anatomy & Physiology|Pleural Cavity & Membranes]]

==Cardiovascular System==

[[Heart - Anatomy & Physiology|Heart]]

[[Vascular System - Anatomy & Physiology|Vascular System]]

==Acknowledgements and Reference Material==
*[[References for the Cardiorespiratory system - Anatomy & Physiology| References]]
*'''Creators:'''
**[[Jo Hinsley]]
**[[Carolyn Harvey-Myers]]

Control of Feeding - Anatomy & Physiology

2008-10-01T13:15:58Z

Rmacharia: /* The Vomit Reflex */

{{toplink
|backcolour =BCED91
|linkpage =Alimentary - Anatomy & Physiology
|linktext =Alimentary System
|maplink = Alimentary (Concept Map)- Anatomy & Physiology
|pagetype =Anatomy
}}
 

==Introduction==

Different hormones, neurotransmitters and reflexes are involved in the complicated process of feeding in animals. Secretions and motility of the gastrointestinal tract are stimulated and carefully regulated by numerous factors, including environmental stimuli and the presence of food in different parts of the gastrointestinal tract from the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]] right through to the intestines.

When a harmful substance is ingested the body acts to eliminate it in different ways to prevent the animal becoming ill, for example, through [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomiting]] and [[Intestine Diarrhoea - Pathology|diarrhoea]].

If one or more of the pathways in controlling feeding is damaged or inhibited, then problems such as obesity occurs.

==Feeding Methods==

*Absorption over body surface

*Filter feeding

*Mucous trapping

*Fluid feeding
**Piercing and sucking
**Cutting and biting

*Seizing prey
**Jaws, [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|teeth]], [[The Integument of Exotic Species#The Beak|beak]]
**Toxins

*Herbivores and grazing
**Invertebrates
**Vertebrates- bony plates or [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|teeth]]

==Functions of the GIT==

The main function of the GIT is to efficently breakdown feed to the essential nutrients that can then be absorbed. The GIT then acts to propell the waste fed material out of the body. The following functions constitute this main function;

*Secretion of enzymes and co-factors for digestion including water, ions and mucous

*Motility for forward propulsion, mechanical breakdown, mixing of ingesta and sphincter tone
**Migrating myoelectric complex to prevent debris accumulation
**Peristalsis
**Haustration
**Segmental motility

*Blood flow to muscles, submucosa and epithelial surfaces to sustain secretion, motility and the uptake of products of digestion

*Growth and repair

==Control of the GIT==

*Endocrine hormones released into the circulation by cells within the GIT or an accessory organ

*Paracrine mediators released by cells within the tract and diffuse locally to act on neighbouring target cells

*Neurotransmitters from nerves and other cells

*Autonomic nervous system superimposed over the local control

==Control of Motility==

*Intrinsic
**Muscle pacemaker cells (Cajal cells)
**Set a basic electric rhythm (BER) of 3-20 per minute
**Passes through gap junctions
**Action potential created producing a slow wave of contraction
**Likelihood of an action potential is increased through the stretch of food in the lumen and chemical food stimulation

*Endocrine, paracrine or neural enter the enteric nervous system via sensory neurones

*Neurons interact with plexuses in the GIT wall
**Myenteric plexus controls muscle movement
**Submucosa plexus controls secretion and blood flow
**2 plexuses connected by interneurones to co-ordinate control
**Autonomic nervous system superimposed

*Excitatory neurotransmitters are parasympathomimetic
**ACh (muscarinic M1 and M2)
**Serotonin
**Substance P

*Inhibitory neurotransmitters are sympathomimetic
**Vasoactive intestinal polypeptide (VIP)
**Nitric oxide (NO)
**ATP
**Enkephalins

*Extrinsic - Autonomic nervous system (ANS)
**Sympathetic via norepinephrine (A1 and B2)
***Thoraco-lumbar innervation
**Parasympathetic via ACh (M1 and M2)
***Cranio-sacral innervation

==Control of GIT Secretions==

*Presence of food in the GIT is detected by open chemoreceptors

*Signals to the endocrine cells or via the ANS releases gastrointestinal peptide hormones

*These hormones act to promote secretion, provide negative feedback or affect motility

*Closed mechanoreceptors also act to alter secretions

*Conditioned (associative) and unconditioned responses act via the ANS

{| style="width:50%; height:200px" border="1"

!'''Control Method'''
!'''Neural'''
!'''Endocrine'''
|-
| '''Saliva'''
| Yes
| No
|-
| '''Stomach'''
| Yes
| Yes
|-
| '''Small Intestine'''
| No
| Yes
|-
|}

==Phases of Gastric Secretion==

===Cephalic===
[[Image:Cephalic phase of secretion diagram.jpg|thumb|right|150px|Cephalic phase of secretion - Copyright RVC 2008]]
*Unconditioned reflex

*Sight, smell, taste of food

*Vagus nerve ([[Nervous System - CNS - Anatomy & Physiology#Innervation - Cranial Nerves|CN X]])
**Parasympathetic fibres
**Synapse in submucosal plexus

*[[Endocrine System - Gut - Anatomy & Physiology|Gastrin]] secreted from endocrine cells in pyloric mucosa

*Postganglionic fibres activate chief, parietal, mucous and G cells

*Histamine secreted from paracrine action

*Increase [[Forestomach - Anatomy & Physiology|stomach]] motility by release of hydrochloric acid and pepsinogen

*Short phase

*Overlaps with gastric phase of secretion

*Inhibited by stress, increased by aggression
[[Image:gastric control of secretion diagram.jpg|thumb|right|150px|Gastric control of secretion - Copyright RVC 2008]]
===Gastric===

*Chemical and mechanical receptors in [[Forestomach - Anatomy & Physiology|stomach]] respond to stretch and chemical stimulation

*Increase in pH of gastric contents

*Response to undigested materials, especially proteins

*Histamine and [[Endocrine System - Gut - Anatomy & Physiology|gastrin]] released

*Negative feedback loop by sympathomimetic somatostatin released by paracrine method to inhibit [[Endocrine System - Gut - Anatomy & Physiology|gastrin]] secretion (when pH falls below 3)

*Submucosal and myenteric plexuses activated in vagus reflex arcs

*Postganglionic release of ACh at parietal cells

*Neural response and presence of peptides in chyme stimulate gastrin release

*Parietal and chief cells stimulate via gastrin acting in the bloodstream

*Long response
[[Image:Intestinal control of secretion diagram.jpg|thumb|right|150px|Intestinal control of secretion - Copyright RVC 2008]]
===Intestinal===

*Chyme in the [[Duodenum - Anatomy & Physiology|duodenum]] inhibits acid secretion and motility by decreasing the [[Forestomach - Anatomy & Physiology|stomach]] distension and increasing the stretch of the [[Duodenum - Anatomy & Physiology|duodenum]] leading to the enterogastric reflex

*A drop in pH below 4.5 causes release of secretin which inhibits parietal and chief cells and stimulate buffer release from the [[Pancreas - Anatomy & Physiology|pancreas]]

*Chyme causes release of secretin, [[Endocrine System - Gut - Anatomy & Physiology|GIP]] and [[Endocrine System - Gut - Anatomy & Physiology|CCK]] decreasing gastric sectreions and motility
[[Image:Pancreatic control of secretion diagram.jpg|thumb|right|150px|Pancretic control of secretion - Copyright RVC 2008]]
===Pancreatic===

*[[Endocrine System - Gut - Anatomy & Physiology|CCK]], secretin and [[Endocrine System - Gut - Anatomy & Physiology|Gastrin]]

*Parasympathetic stimulation during cephalic and gastric phases

*Negative feedback from paracrine sympathomimetics (somatostatin and enkephalins)

===Biliary===

*[[Endocrine System - Gut - Anatomy & Physiology|CCK]] empties [[Gall Bladder - Anatomy & Physiology|gall bladder]]

*Secretin stimulates hydrogencarbonate ions from bile duct

===Small Intestinal===

*Succus entericus

*Secretin, [[Endocrine System - Gut - Anatomy & Physiology|GIP]] and [[Endocrine System - Gut - Anatomy & Physiology|Gastrin]]

*Vagal tone and parasympathomimetic reflex

==Neuroendocrine Regulation of Feeding==

*[[Hypothalamus - Anatomy & Physiology|Hypothalamus]] is the critical region of feeding control

*Major hypothalamic nuclei involved:
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate]]
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Ventromedial hypothalamus]]
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Dorsomedial hypothalamus]]
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Lateral hypothalamus]]
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Paraventricular hypothalamus]]

===Gut Peptides===

{| style="width:75%; height:300px" border="1"

!'''Peptide'''
!'''Site of Release'''
!'''Effect on Feeding'''
|-
| '''CCK'''
| [[Duodenum - Anatomy & Physiology|Duodenum]]
| Reduces food intake
|-
| '''Ghrelin'''
| Gastric fundus
| Increases food intake
|-
| '''GLP-2'''
| Intestine
| Reduces food intake
|-
| '''Motilin'''
| [[Small Intestine - Anatomy & Physiology|Small intestine]]
| Indirectly inhibits food intake
|-
| '''Oxyntomodulin'''
| [[Large Intestine - Anatomy & Physiology|large intestine]]
| Inhibits food intake
|-
| '''Pancreatic Polypeptide'''
| [[Pancreas - Anatomy & Physiology|Pancreas]]
| Inhibits food intake
|-
| '''PYY3-36'''
| Intestine
| Inhibits food intake
|-
| '''Somatostatin'''
| [[Pancreas - Anatomy & Physiology|Pancreas]]
| Inhibits food intake
|-
|}

===Other Peptides===

{| style="width:75%; height:200px" border="1"

!'''Peptide'''
!'''Site of Release'''
!'''Effect on Feeding'''
|-
| '''Leptin'''
| Adipocyte
| Reduces food intake
|-
| '''NPY'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate nucleus]]
| Increases food intake
|-
| '''Agrp'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate nucleus]]
| Increases food intake
|-
| '''MCH'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Lateral hypothalamus]]
| Increases food intake
|-
| '''Orexins'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Lateral hypothalamus]]
| Increases food intake
|-
| '''CART'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate nucleus]]
| Inhibits food intake
|-
| '''α MSH'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate nucleus]]
| Inhibits food intake
|-
| '''Bdnf'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Ventromedial nucleus]]
| Inhibits food intake
|-
| '''Serotonin'''
| Brainstem
| Inhibits food intake
|-
| '''Cannabinoids'''
| [[Nervous System - CNS - Anatomy & Physiology|CNS]]
| Increases food intake
|-
|}

==The Vomit Reflex==
[[Image:The Vomit Reflex Pathway.jpg|right|thumb|150px|The Vomit Reflex - Copyright nabrown RVC]]
*Emesis is the process of vomiting

*Persistent vomiting can be exhausting and can lead to metabolic alkalosis, dehydration and electrolyte inbalances which may require fluid therapy

*Extreme cases of persistent vomiting can lead to shock

*Retching involves the abdominal and chest walls contracting

*Vomiting includes retching and the action of the diaphragm

*Diaphragm moves caudal to open the cardia

*Gastrointestinal tract have protective stimuli to recognise harmful products ingested. The mechanoreceptors and chemoreceptors respond using viscerent afferent pathways.

*Medulla co-ordinates process

*Chemoreceptive trigger zone in the 4th ventricle responds to blood and CSF

*Inputs also from inner ear and higher centres

*Emetic agents can be used in cases of gastric obstruction and to remove non-corrosive poisons from the stomach (for corrosive poisons charcoal can be used which will help adsorb the substance and decrease its absorbtion into the GIT)

===Emetic agents===
*Drugs cause emesis by irritating the gastric mucosa
**Histamine
**ACh
**Dopamine
**Catecholamines
**5-hydroxytryptamine
**Substance P
**Enkephalins
**NK1 receptor agonists

===Anti-emetic agents===
*Anti-emetic agents can be used to treat motion sickness and to treat or prevent vomiting
**Dopamine (D2) receptor antagonists
**5-hydroxytryptamine antagonists
**NK1 receptor antagonists
**Muscarinic receptor antagonists
**Histamine (H1) receptor antagonists
**Gastroprotective agents

==Species Differences==

===Equine===
*The horse cannot vomit

Control of Feeding - Anatomy & Physiology

2008-10-01T13:04:29Z

Rmacharia: /* Control of Motility */

{{toplink
|backcolour =BCED91
|linkpage =Alimentary - Anatomy & Physiology
|linktext =Alimentary System
|maplink = Alimentary (Concept Map)- Anatomy & Physiology
|pagetype =Anatomy
}}
 

==Introduction==

Different hormones, neurotransmitters and reflexes are involved in the complicated process of feeding in animals. Secretions and motility of the gastrointestinal tract are stimulated and carefully regulated by numerous factors, including environmental stimuli and the presence of food in different parts of the gastrointestinal tract from the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]] right through to the intestines.

When a harmful substance is ingested the body acts to eliminate it in different ways to prevent the animal becoming ill, for example, through [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomiting]] and [[Intestine Diarrhoea - Pathology|diarrhoea]].

If one or more of the pathways in controlling feeding is damaged or inhibited, then problems such as obesity occurs.

==Feeding Methods==

*Absorption over body surface

*Filter feeding

*Mucous trapping

*Fluid feeding
**Piercing and sucking
**Cutting and biting

*Seizing prey
**Jaws, [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|teeth]], [[The Integument of Exotic Species#The Beak|beak]]
**Toxins

*Herbivores and grazing
**Invertebrates
**Vertebrates- bony plates or [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|teeth]]

==Functions of the GIT==

The main function of the GIT is to efficently breakdown feed to the essential nutrients that can then be absorbed. The GIT then acts to propell the waste fed material out of the body. The following functions constitute this main function;

*Secretion of enzymes and co-factors for digestion including water, ions and mucous

*Motility for forward propulsion, mechanical breakdown, mixing of ingesta and sphincter tone
**Migrating myoelectric complex to prevent debris accumulation
**Peristalsis
**Haustration
**Segmental motility

*Blood flow to muscles, submucosa and epithelial surfaces to sustain secretion, motility and the uptake of products of digestion

*Growth and repair

==Control of the GIT==

*Endocrine hormones released into the circulation by cells within the GIT or an accessory organ

*Paracrine mediators released by cells within the tract and diffuse locally to act on neighbouring target cells

*Neurotransmitters from nerves and other cells

*Autonomic nervous system superimposed over the local control

==Control of Motility==

*Intrinsic
**Muscle pacemaker cells (Cajal cells)
**Set a basic electric rhythm (BER) of 3-20 per minute
**Passes through gap junctions
**Action potential created producing a slow wave of contraction
**Likelihood of an action potential is increased through the stretch of food in the lumen and chemical food stimulation

*Endocrine, paracrine or neural enter the enteric nervous system via sensory neurones

*Neurons interact with plexuses in the GIT wall
**Myenteric plexus controls muscle movement
**Submucosa plexus controls secretion and blood flow
**2 plexuses connected by interneurones to co-ordinate control
**Autonomic nervous system superimposed

*Excitatory neurotransmitters are parasympathomimetic
**ACh (muscarinic M1 and M2)
**Serotonin
**Substance P

*Inhibitory neurotransmitters are sympathomimetic
**Vasoactive intestinal polypeptide (VIP)
**Nitric oxide (NO)
**ATP
**Enkephalins

*Extrinsic - Autonomic nervous system (ANS)
**Sympathetic via norepinephrine (A1 and B2)
***Thoraco-lumbar innervation
**Parasympathetic via ACh (M1 and M2)
***Cranio-sacral innervation

==Control of GIT Secretions==

*Presence of food in the GIT is detected by open chemoreceptors

*Signals to the endocrine cells or via the ANS releases gastrointestinal peptide hormones

*These hormones act to promote secretion, provide negative feedback or affect motility

*Closed mechanoreceptors also act to alter secretions

*Conditioned (associative) and unconditioned responses act via the ANS

{| style="width:50%; height:200px" border="1"

!'''Control Method'''
!'''Neural'''
!'''Endocrine'''
|-
| '''Saliva'''
| Yes
| No
|-
| '''Stomach'''
| Yes
| Yes
|-
| '''Small Intestine'''
| No
| Yes
|-
|}

==Phases of Gastric Secretion==

===Cephalic===
[[Image:Cephalic phase of secretion diagram.jpg|thumb|right|150px|Cephalic phase of secretion - Copyright RVC 2008]]
*Unconditioned reflex

*Sight, smell, taste of food

*Vagus nerve ([[Nervous System - CNS - Anatomy & Physiology#Innervation - Cranial Nerves|CN X]])
**Parasympathetic fibres
**Synapse in submucosal plexus

*[[Endocrine System - Gut - Anatomy & Physiology|Gastrin]] secreted from endocrine cells in pyloric mucosa

*Postganglionic fibres activate chief, parietal, mucous and G cells

*Histamine secreted from paracrine action

*Increase [[Forestomach - Anatomy & Physiology|stomach]] motility by release of hydrochloric acid and pepsinogen

*Short phase

*Overlaps with gastric phase of secretion

*Inhibited by stress, increased by aggression
[[Image:gastric control of secretion diagram.jpg|thumb|right|150px|Gastric control of secretion - Copyright RVC 2008]]
===Gastric===

*Chemical and mechanical receptors in [[Forestomach - Anatomy & Physiology|stomach]] respond to stretch and chemical stimulation

*Increase in pH of gastric contents

*Response to undigested materials, especially proteins

*Histamine and [[Endocrine System - Gut - Anatomy & Physiology|gastrin]] released

*Negative feedback loop by sympathomimetic somatostatin released by paracrine method to inhibit [[Endocrine System - Gut - Anatomy & Physiology|gastrin]] secretion (when pH falls below 3)

*Submucosal and myenteric plexuses activated in vagus reflex arcs

*Postganglionic release of ACh at parietal cells

*Neural response and presence of peptides in chyme stimulate gastrin release

*Parietal and chief cells stimulate via gastrin acting in the bloodstream

*Long response
[[Image:Intestinal control of secretion diagram.jpg|thumb|right|150px|Intestinal control of secretion - Copyright RVC 2008]]
===Intestinal===

*Chyme in the [[Duodenum - Anatomy & Physiology|duodenum]] inhibits acid secretion and motility by decreasing the [[Forestomach - Anatomy & Physiology|stomach]] distension and increasing the stretch of the [[Duodenum - Anatomy & Physiology|duodenum]] leading to the enterogastric reflex

*A drop in pH below 4.5 causes release of secretin which inhibits parietal and chief cells and stimulate buffer release from the [[Pancreas - Anatomy & Physiology|pancreas]]

*Chyme causes release of secretin, [[Endocrine System - Gut - Anatomy & Physiology|GIP]] and [[Endocrine System - Gut - Anatomy & Physiology|CCK]] decreasing gastric sectreions and motility
[[Image:Pancreatic control of secretion diagram.jpg|thumb|right|150px|Pancretic control of secretion - Copyright RVC 2008]]
===Pancreatic===

*[[Endocrine System - Gut - Anatomy & Physiology|CCK]], secretin and [[Endocrine System - Gut - Anatomy & Physiology|Gastrin]]

*Parasympathetic stimulation during cephalic and gastric phases

*Negative feedback from paracrine sympathomimetics (somatostatin and enkephalins)

===Biliary===

*[[Endocrine System - Gut - Anatomy & Physiology|CCK]] empties [[Gall Bladder - Anatomy & Physiology|gall bladder]]

*Secretin stimulates hydrogencarbonate ions from bile duct

===Small Intestinal===

*Succus entericus

*Secretin, [[Endocrine System - Gut - Anatomy & Physiology|GIP]] and [[Endocrine System - Gut - Anatomy & Physiology|Gastrin]]

*Vagal tone and parasympathomimetic reflex

==Neuroendocrine Regulation of Feeding==

*[[Hypothalamus - Anatomy & Physiology|Hypothalamus]] is the critical region of feeding control

*Major hypothalamic nuclei involved:
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate]]
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Ventromedial hypothalamus]]
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Dorsomedial hypothalamus]]
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Lateral hypothalamus]]
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Paraventricular hypothalamus]]

===Gut Peptides===

{| style="width:75%; height:300px" border="1"

!'''Peptide'''
!'''Site of Release'''
!'''Effect on Feeding'''
|-
| '''CCK'''
| [[Duodenum - Anatomy & Physiology|Duodenum]]
| Reduces food intake
|-
| '''Ghrelin'''
| Gastric fundus
| Increases food intake
|-
| '''GLP-2'''
| Intestine
| Reduces food intake
|-
| '''Motilin'''
| [[Small Intestine - Anatomy & Physiology|Small intestine]]
| Indirectly inhibits food intake
|-
| '''Oxyntomodulin'''
| [[Large Intestine - Anatomy & Physiology|large intestine]]
| Inhibits food intake
|-
| '''Pancreatic Polypeptide'''
| [[Pancreas - Anatomy & Physiology|Pancreas]]
| Inhibits food intake
|-
| '''PYY3-36'''
| Intestine
| Inhibits food intake
|-
| '''Somatostatin'''
| [[Pancreas - Anatomy & Physiology|Pancreas]]
| Inhibits food intake
|-
|}

===Other Peptides===

{| style="width:75%; height:200px" border="1"

!'''Peptide'''
!'''Site of Release'''
!'''Effect on Feeding'''
|-
| '''Leptin'''
| Adipocyte
| Reduces food intake
|-
| '''NPY'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate nucleus]]
| Increases food intake
|-
| '''Agrp'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate nucleus]]
| Increases food intake
|-
| '''MCH'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Lateral hypothalamus]]
| Increases food intake
|-
| '''Orexins'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Lateral hypothalamus]]
| Increases food intake
|-
| '''CART'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate nucleus]]
| Inhibits food intake
|-
| '''α MSH'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate nucleus]]
| Inhibits food intake
|-
| '''Bdnf'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Ventromedial nucleus]]
| Inhibits food intake
|-
| '''Serotonin'''
| Brainstem
| Inhibits food intake
|-
| '''Cannabinoids'''
| [[Nervous System - CNS - Anatomy & Physiology|CNS]]
| Increases food intake
|-
|}

==The Vomit Reflex==
[[Image:The Vomit Reflex Pathway.jpg|right|thumb|150px|The Vomit Reflex - Copyright nabrown RVC]]
*Emesis is the process of vomiting

*Persistant vomiting can be exhausting and can lead to metabolic alkalosis, dehydration and electrolyte inbalances which may require fluid therapy

*Extreme cases of persistant vomiting can lead to shock

*Retching involves the abdominal and chest walls contracting

*Vomiting includes retching and the action of the diaphragm

*Diaphragm moves caudal to open the cardia

*Gastrointestinal tract have protective stimuli to recognise harmful products ingested. The mechanoreceptors and chemoreceptors respond using viscerent afferent pathways.

*Medulla co-ordinates process

*Chemoreceptive trigger zone in the 4th ventricle responds to blood and CSF

*Inputs also from inner ear and higher centres

*Emetic agents can be used in cases of gastric obstruction and to remove non-corrosive poisons from the stomach (for corrosive poisons charcoal can be used which will help adsorb the substance and decrease its absorbtion into the GIT)

===Emetic agents===
*Drugs cause emesis by irritating the gastric mucosa
**Histamine
**ACh
**Dopamine
**Catecholamines
**5-hydroxytryptamine
**Substance P
**Enkephalins
**NK1 receptor agonists

===Anti-emetic agents===
*Anti-emetic agents can be used to treat motion sickness and to treat or prevent vomiting
**Dopamine (D2) receptor antagonists
**5-hydroxytryptamine antagonists
**NK1 receptor antagonists
**Muscarinic receptor antagonists
**Histamine (H1) receptor antagonists
**Gastroprotective agents

==Species Differences==

===Equine===
*The horse cannot vomit

Control of Feeding - Anatomy & Physiology

2008-10-01T13:02:34Z

Rmacharia: /* Control of Motility */

{{toplink
|backcolour =BCED91
|linkpage =Alimentary - Anatomy & Physiology
|linktext =Alimentary System
|maplink = Alimentary (Concept Map)- Anatomy & Physiology
|pagetype =Anatomy
}}
 

==Introduction==

Different hormones, neurotransmitters and reflexes are involved in the complicated process of feeding in animals. Secretions and motility of the gastrointestinal tract are stimulated and carefully regulated by numerous factors, including environmental stimuli and the presence of food in different parts of the gastrointestinal tract from the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]] right through to the intestines.

When a harmful substance is ingested the body acts to eliminate it in different ways to prevent the animal becoming ill, for example, through [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomiting]] and [[Intestine Diarrhoea - Pathology|diarrhoea]].

If one or more of the pathways in controlling feeding is damaged or inhibited, then problems such as obesity occurs.

==Feeding Methods==

*Absorption over body surface

*Filter feeding

*Mucous trapping

*Fluid feeding
**Piercing and sucking
**Cutting and biting

*Seizing prey
**Jaws, [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|teeth]], [[The Integument of Exotic Species#The Beak|beak]]
**Toxins

*Herbivores and grazing
**Invertebrates
**Vertebrates- bony plates or [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|teeth]]

==Functions of the GIT==

The main function of the GIT is to efficently breakdown feed to the essential nutrients that can then be absorbed. The GIT then acts to propell the waste fed material out of the body. The following functions constitute this main function;

*Secretion of enzymes and co-factors for digestion including water, ions and mucous

*Motility for forward propulsion, mechanical breakdown, mixing of ingesta and sphincter tone
**Migrating myoelectric complex to prevent debris accumulation
**Peristalsis
**Haustration
**Segmental motility

*Blood flow to muscles, submucosa and epithelial surfaces to sustain secretion, motility and the uptake of products of digestion

*Growth and repair

==Control of the GIT==

*Endocrine hormones released into the circulation by cells within the GIT or an accessory organ

*Paracrine mediators released by cells within the tract and diffuse locally to act on neighbouring target cells

*Neurotransmitters from nerves and other cells

*Autonomic nervous system superimposed over the local control

==Control of Motility==

*Intrinsic
**Muscle pacemaker cells (Cajal cells)
**Set a basic electric rhythm (BER) of 3-20 per minute
**Passes through gap junctions
**Action potential created producing a slow wave of contraction
**Likelihood of an action potential is increased through the stretch of food in the lumen and chemical food stimulation

*Endocrine, paracrine or neural enter the enteric nervous system via sensory neurones

*Neurons interact with plexuses in the GIT wall
**Myenteric plexus controls muscle movement
**Submucosa plexus controls secretion and blood flow
**2 plexuses connected by interneurones to co-ordinate control
**Autonomic nervous system superimposed

*Excitatory neurotransmitters are parasympathomimetic
**ACh (muscarinic M1 and M2)
**Serotonin
**Substance P

*Inhibitory neurotransmitters are sympathomimetic
**Vasoactive intestinal polypeptide (VIP)
**Nitroc oxide (NO)
**ATP
**Enkephalins

*Extrinsic nervous system (ANS)
**Sympathetic via norepinephrine (A1 and B2)
***Thoraco-lumbar innervation
**Parasympathetic via ACh (M1 and M2)
***Cranio-sacral innervation

==Control of GIT Secretions==

*Presence of food in the GIT is detected by open chemoreceptors

*Signals to the endocrine cells or via the ANS releases gastrointestinal peptide hormones

*These hormones act to promote secretion, provide negative feedback or affect motility

*Closed mechanoreceptors also act to alter secretions

*Conditioned (associative) and unconditioned responses act via the ANS

{| style="width:50%; height:200px" border="1"

!'''Control Method'''
!'''Neural'''
!'''Endocrine'''
|-
| '''Saliva'''
| Yes
| No
|-
| '''Stomach'''
| Yes
| Yes
|-
| '''Small Intestine'''
| No
| Yes
|-
|}

==Phases of Gastric Secretion==

===Cephalic===
[[Image:Cephalic phase of secretion diagram.jpg|thumb|right|150px|Cephalic phase of secretion - Copyright RVC 2008]]
*Unconditioned reflex

*Sight, smell, taste of food

*Vagus nerve ([[Nervous System - CNS - Anatomy & Physiology#Innervation - Cranial Nerves|CN X]])
**Parasympathetic fibres
**Synapse in submucosal plexus

*[[Endocrine System - Gut - Anatomy & Physiology|Gastrin]] secreted from endocrine cells in pyloric mucosa

*Postganglionic fibres activate chief, parietal, mucous and G cells

*Histamine secreted from paracrine action

*Increase [[Forestomach - Anatomy & Physiology|stomach]] motility by release of hydrochloric acid and pepsinogen

*Short phase

*Overlaps with gastric phase of secretion

*Inhibited by stress, increased by aggression
[[Image:gastric control of secretion diagram.jpg|thumb|right|150px|Gastric control of secretion - Copyright RVC 2008]]
===Gastric===

*Chemical and mechanical receptors in [[Forestomach - Anatomy & Physiology|stomach]] respond to stretch and chemical stimulation

*Increase in pH of gastric contents

*Response to undigested materials, especially proteins

*Histamine and [[Endocrine System - Gut - Anatomy & Physiology|gastrin]] released

*Negative feedback loop by sympathomimetic somatostatin released by paracrine method to inhibit [[Endocrine System - Gut - Anatomy & Physiology|gastrin]] secretion (when pH falls below 3)

*Submucosal and myenteric plexuses activated in vagus reflex arcs

*Postganglionic release of ACh at parietal cells

*Neural response and presence of peptides in chyme stimulate gastrin release

*Parietal and chief cells stimulate via gastrin acting in the bloodstream

*Long response
[[Image:Intestinal control of secretion diagram.jpg|thumb|right|150px|Intestinal control of secretion - Copyright RVC 2008]]
===Intestinal===

*Chyme in the [[Duodenum - Anatomy & Physiology|duodenum]] inhibits acid secretion and motility by decreasing the [[Forestomach - Anatomy & Physiology|stomach]] distension and increasing the stretch of the [[Duodenum - Anatomy & Physiology|duodenum]] leading to the enterogastric reflex

*A drop in pH below 4.5 causes release of secretin which inhibits parietal and chief cells and stimulate buffer release from the [[Pancreas - Anatomy & Physiology|pancreas]]

*Chyme causes release of secretin, [[Endocrine System - Gut - Anatomy & Physiology|GIP]] and [[Endocrine System - Gut - Anatomy & Physiology|CCK]] decreasing gastric sectreions and motility
[[Image:Pancreatic control of secretion diagram.jpg|thumb|right|150px|Pancretic control of secretion - Copyright RVC 2008]]
===Pancreatic===

*[[Endocrine System - Gut - Anatomy & Physiology|CCK]], secretin and [[Endocrine System - Gut - Anatomy & Physiology|Gastrin]]

*Parasympathetic stimulation during cephalic and gastric phases

*Negative feedback from paracrine sympathomimetics (somatostatin and enkephalins)

===Biliary===

*[[Endocrine System - Gut - Anatomy & Physiology|CCK]] empties [[Gall Bladder - Anatomy & Physiology|gall bladder]]

*Secretin stimulates hydrogencarbonate ions from bile duct

===Small Intestinal===

*Succus entericus

*Secretin, [[Endocrine System - Gut - Anatomy & Physiology|GIP]] and [[Endocrine System - Gut - Anatomy & Physiology|Gastrin]]

*Vagal tone and parasympathomimetic reflex

==Neuroendocrine Regulation of Feeding==

*[[Hypothalamus - Anatomy & Physiology|Hypothalamus]] is the critical region of feeding control

*Major hypothalamic nuclei involved:
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate]]
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Ventromedial hypothalamus]]
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Dorsomedial hypothalamus]]
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Lateral hypothalamus]]
**[[Hypothalamus - Anatomy & Physiology#Nuclei|Paraventricular hypothalamus]]

===Gut Peptides===

{| style="width:75%; height:300px" border="1"

!'''Peptide'''
!'''Site of Release'''
!'''Effect on Feeding'''
|-
| '''CCK'''
| [[Duodenum - Anatomy & Physiology|Duodenum]]
| Reduces food intake
|-
| '''Ghrelin'''
| Gastric fundus
| Increases food intake
|-
| '''GLP-2'''
| Intestine
| Reduces food intake
|-
| '''Motilin'''
| [[Small Intestine - Anatomy & Physiology|Small intestine]]
| Indirectly inhibits food intake
|-
| '''Oxyntomodulin'''
| [[Large Intestine - Anatomy & Physiology|large intestine]]
| Inhibits food intake
|-
| '''Pancreatic Polypeptide'''
| [[Pancreas - Anatomy & Physiology|Pancreas]]
| Inhibits food intake
|-
| '''PYY3-36'''
| Intestine
| Inhibits food intake
|-
| '''Somatostatin'''
| [[Pancreas - Anatomy & Physiology|Pancreas]]
| Inhibits food intake
|-
|}

===Other Peptides===

{| style="width:75%; height:200px" border="1"

!'''Peptide'''
!'''Site of Release'''
!'''Effect on Feeding'''
|-
| '''Leptin'''
| Adipocyte
| Reduces food intake
|-
| '''NPY'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate nucleus]]
| Increases food intake
|-
| '''Agrp'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate nucleus]]
| Increases food intake
|-
| '''MCH'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Lateral hypothalamus]]
| Increases food intake
|-
| '''Orexins'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Lateral hypothalamus]]
| Increases food intake
|-
| '''CART'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate nucleus]]
| Inhibits food intake
|-
| '''α MSH'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Arcuate nucleus]]
| Inhibits food intake
|-
| '''Bdnf'''
| [[Hypothalamus - Anatomy & Physiology#Nuclei|Ventromedial nucleus]]
| Inhibits food intake
|-
| '''Serotonin'''
| Brainstem
| Inhibits food intake
|-
| '''Cannabinoids'''
| [[Nervous System - CNS - Anatomy & Physiology|CNS]]
| Increases food intake
|-
|}

==The Vomit Reflex==
[[Image:The Vomit Reflex Pathway.jpg|right|thumb|150px|The Vomit Reflex - Copyright nabrown RVC]]
*Emesis is the process of vomiting

*Persistant vomiting can be exhausting and can lead to metabolic alkalosis, dehydration and electrolyte inbalances which may require fluid therapy

*Extreme cases of persistant vomiting can lead to shock

*Retching involves the abdominal and chest walls contracting

*Vomiting includes retching and the action of the diaphragm

*Diaphragm moves caudal to open the cardia

*Gastrointestinal tract have protective stimuli to recognise harmful products ingested. The mechanoreceptors and chemoreceptors respond using viscerent afferent pathways.

*Medulla co-ordinates process

*Chemoreceptive trigger zone in the 4th ventricle responds to blood and CSF

*Inputs also from inner ear and higher centres

*Emetic agents can be used in cases of gastric obstruction and to remove non-corrosive poisons from the stomach (for corrosive poisons charcoal can be used which will help adsorb the substance and decrease its absorbtion into the GIT)

===Emetic agents===
*Drugs cause emesis by irritating the gastric mucosa
**Histamine
**ACh
**Dopamine
**Catecholamines
**5-hydroxytryptamine
**Substance P
**Enkephalins
**NK1 receptor agonists

===Anti-emetic agents===
*Anti-emetic agents can be used to treat motion sickness and to treat or prevent vomiting
**Dopamine (D2) receptor antagonists
**5-hydroxytryptamine antagonists
**NK1 receptor antagonists
**Muscarinic receptor antagonists
**Histamine (H1) receptor antagonists
**Gastroprotective agents

==Species Differences==

===Equine===
*The horse cannot vomit