Difference between revisions of "Forebrain - Anatomy & Physiology"

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Also known as: '''''Proencephalon'''''
 
  
 
==Introduction==
 
==Introduction==
The ''forebrain (proencephalon)'' is the largest part of the brain, most of which is ''cerebrum''. Other important structures found in the forebrain include the ''thalamus'' , the ''hypothalamus'' and the ''limbic system''. The cerebrum is divided into two cerebral hemispheres connected by a mass of white matter  known as the ''corpus callosum''. Each hemisphere is split into four lobes; the ''frontal'', ''parietal'', ''occipital''  and ''temporal'' lobes. The surface of each hemisphere is made up of grey matter known as the ''cerebral cortex'' and is folded to increase the surface area available within the skull. The cortex has roles within perception, memory and all higher thought processes. Inside the cortex is the ''white matter'', within which are a number of nuclei (grey matter), known as the ''basal nuclei''. The basal nuclei receive information from the cortex to regulate skeletal movement and other higher motor functions.
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The ''forebrain (proencephalon)'' is the largest part of the brain, most of which is ''[[#Cerebrum|cerebrum]]''. Other important structures found in the forebrain include the ''[[Forebrain - Anatomy & Physiology#thalamus|thalamus]]'' , the ''[[Forebrain - Anatomy & Physiology#hypothalamus|hypothalamus]]'' and the ''[[#Limbic System|limbic system]]''. The cerebrum is divided into two cerebral hemispheres connected by a mass of white matter  known as the ''corpus callosum''. Each hemisphere is split into four lobes; the ''frontal'', ''parietal'', ''occipital''  and ''temporal'' lobes. The surface of each hemisphere is made up of grey matter known as the ''cerebral cortex'' and is folded to increase the surface area available within the skull. The cortex has roles within perception, memory and all higher thought processes. Inside the cortex is the ''white matter'', within which are a number of nuclei (grey matter), known as the ''basal nuclei''. The basal nuclei receive information from the cortex to regulate skeletal movement and other higher motor functions.
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The [[Forebrain - Anatomy & Physiology#thalamus|thalamus]] functions to relay sensory information to the [[Forebrain - Anatomy & Physiology#Cerebral Cortex|cerebral cortex]] and the [[Forebrain - Anatomy & Physiology#Hypothalamus|hypothalamus]], regulating visceral functions including temperature, reproductive functions, eating, sleeping and the display of emotion. The limbic system describes a collection of structures within the forebrain, including the ''amygdala  hippocampus'', also known as the 'emotional brain', the limbic system is important in the formation of memories and in making decisions and learning.
  
The thalamus functions to relay sensory information to the cerebral cortex and the hypothalamus, regulating visceral functions including temperature, reproductive functions, eating, sleeping and the display of emotion. The limbic system describes a collection of structures within the forebrain, including the ''amygdala'' and ''  hippocampus'', also known as the 'emotional brain'. It is important in the formation of memories and in making decisions and learning.
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==Structure and Function==
  
==Forebrain Structure and Function==
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{| style="width:75%; height:200px" border="1"
  
{| style="width:75%; height:200px" border="1"
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!
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!'''Structures present'''
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!'''Function'''
  
!Brain Region
 
!Structure
 
!Function
 
 
|-  
 
|-  
| Diencephalon
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| '''[[Forebrain - Anatomy & Physiology|Forebrain (Proencephalon)]]'''
| Thalamus
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| '''Diencephalon''' - [[Forebrain - Anatomy & Physiology#Thalamus|Thalamus]], [[Forebrain - Anatomy & Physiology#Hypothalamus|Hypothalamus]], [[Forebrain - Anatomy & Physiology#Pituitary|Pituitary]]
| Organising sensory information
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'''Telencephalon''' - [[Forebrain - Anatomy & Physiology#Cerebral Cortex|Cerebral Cortex]]
|-  
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| Diencephalon
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'''[[Forebrain - Anatomy & Physiology#Limbic System|Limbic System]]'''
| Hypothalamus
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| Endocrine System, Thermoregulation
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'''[[Forebrain - Anatomy & Physiology#Olfactory Bulb|Olfactory bulb]]'''
|-
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|'''[[Forebrain - Anatomy & Physiology#Thalamus|Thalamus]]''' - Organising sensory information
| Diencephalon
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'''[[Forebrain - Anatomy & Physiology#Hypothalamus|Hypothalamus]]''' - Endocrine System, Thermoregulation
| Pituitary
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| Endocrine System
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'''[[Forebrain - Anatomy & Physiology#Cerebral Cortex|Cerebral Cortex]]''' - Conciousness, language etc
|-  
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| Telencephalon
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'''[[Forebrain - Anatomy & Physiology#Limbic System|Limbic System]]''' - Memory, motivation, emotion
| Cerebral Cortex
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| Conciousness, language etc
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'''[[Forebrain - Anatomy & Physiology#Olfactory Bulb|Olfactory bulb]]''' - Smell
|-  
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|
| Telencephalon
 
| Limbic System
 
| Memory, motivation, emotion
 
|-  
 
| Telencephalon
 
| Olfactory Bulb
 
| Smell
 
|-
 
 
|}
 
|}
  
===Thalamus===
 
The thalamus has many functions including processing and relaying sensory information selectively to various parts of the cerebral cortex, translating signals to the cerebral cortex from lower centres including auditory, somatic, visceral, gustatory and visual systems and also regulating states of sleep and wakefulness. The thalamus plays a major role in regulating arousal, levels of consciousness and levels of activity.
 
  
===Hypothalamus===
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====Thalamus====
The function of the hypothalamus is mainly related to the overall regulation of the [[:Category:Endocrine System - Anatomy & Physiology|Endocrine System]]. The hypothalamus is closely related to the [[Pituitary Gland - Anatomy & Physiology|pituitary gland]], controlling a large proportion of the activity going to it. For a more detailed analysis of the function of this part of the brain, please use the link: [[Hypothalamus - Anatomy & Physiology|Hypothalamus Anatomy and Physiology]].
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The thalamus has many functions:
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*'''Processes and relays''' sensory information selectively to various parts of the '''cerebral cortex'''.
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*'''Translates''' signals to the cerebral cortex from lower centres including auditory, somatic, visceral, gustatory and visual systems.
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*'''Regulates''' states of '''sleep''' and '''wakefulness'''.
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*The thalamus plays a major role in regulating '''arousal''', the level of '''conciousness''', and '''activity'''.
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====Hypothalamus====
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The function of the hypothalamus is mainly endocrine.
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See [[Hypothalamus - Anatomy & Physiology|Hypothalamus]].
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====Pituitary====
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The function of the hypothalamus is mainly endocrine.
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See [[Pituitary Gland - Anatomy & Physiology|Pituitary]].
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====Cerebral Cortex====
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*Essential for '''memory''', '''attention''', '''awareness''', '''thought''', '''language''', and '''consciousness'''.
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*Outer layer of the cerebrum is grey matter.
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*Grey matter is formed by neurons and their unmyelinated fibres, (white matter below the grey matter of the cortex is formed predominantly by myelinated axons as myelin is white in appearance).
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*The surface of the cerebral cortex is folded in mammals; more than two thirds of the surface is within the grooves or "sulci".
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*The cerebral cortex is connected to structures such as the '''thalamus''' and the '''basal ganglia''', sending information to them along '''efferent''' connections and receiving information from them via '''afferent''' connections.
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*Most sensory information is routed to the cerebral cortex via the '''thalamus'''.
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The '''cortex''' is commonly described as comprising three parts: '''sensory''', '''motor''', and '''association areas''':
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'''Sensory areas'''
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*The sensory areas are the areas that receive and process information from the senses; INSERT HERE.
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*Inputs from the thalamus are called '''primary sensory areas'''.
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*Vision, hearing, and touch are processed by the primary visual cortex, primary auditory cortex and primary somatosensory cortex.
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*The two hemispheres receive information from the opposite (contralateral) side of the body.
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*Areas with lots of sensory innervation, such as the fingertips and the lips, require more cortical area to process finer sensation.
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'''Association areas'''
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*Association areas function is to produce a perception of the world, so an animal can interact effectively.
  
===Pituitary===
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*The '''parietal''', '''temporal''', and '''occipital lobe''' - all located in the '''posterior''' part of the cortex - organize sensory information.  
The function of the pituitary is mainly related to the production of hormones as part of the Endocrine System. For further information on the pituitary gland please use this link: [[Pituitary Gland - Anatomy & Physiology|Pituitary Gland Anatomy and Physiology]].
 
  
===Cerebral Cortex===
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*The '''frontal lobe''' or prefrontal association complex is involved in planning actions and movement.
The cerebral cortex is essential for memory, attention, awareness, thought, language and consciousness. The outer layers of the cerebrum are made up of grey matter. Grey matter is formed by neurons and their unmyelinated fibres. The white matter below the grey matter of the cortex is formed predominantly by myelinated axons (myelin is white in appearance). The surface of the cerebral cortex is folded in mammals; more than two thirds of the surface is within the grooves or ''"sulci"''. The cerebral cortex is connected to structures such as the thalamus and the basal ganglia, sending information to them along ''efferent'' connections and receiving information from them via ''afferent'' connections. Most sensory information is routed to the cerebral cortex via the thalamus. The cortex is commonly described as comprising three parts; sensory, motor and association areas.
 
  
====Sensory Areas====
 
[[Image:Homunculus.png|thumb|right|150px|''Homonculus'' (Human), btarski, 2006, WikiMedia Commons]]
 
The sensory areas are the areas that receive and process information from the senses. Inputs from the thalamus are called ''primary sensory areas''. Vision, hearing, and touch are processed by the primary visual cortex, primary auditory cortex and primary somatosensory cortex. The two hemispheres of the cerebral cortex receive information from the opposite (contralateral) side of the body. Areas with lots of sensory innervation, such as the fingertips and the lips, require more cortical area to process finer sensation. The ''association areas'' of the brain function to produce a perception of the world enabling an animal to interact with their environment effectively.
 
  
There are a number of anatomical areas of the brain responsible for organising this sensory information. The ''parietal lobe'' is located within the dorsocaudal aspect of the cortex. The ''temporal lobes'' are located laterally and the ''occipital lobes'' are located in the caudal most aspect of the cortex. The ''frontal lobe'' or ''prefrontal association complex'' is involved in planning actions and movement.
 
  
===Motor Cortex===
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'''Motor areas'''
The ''motor cortex'' areas of the brain are located in both hemispheres of the cortex and are shaped like a pair of headphones stretching from ear to ear. The motor areas are related to controlling voluntary movements, especially fine movements. There are two main types of connection between the motor cortex and motor neurones found in the ventral horn of the spinal cord; the ''Pyramidal tracts'' and the ''Extrapyramidal tracts''.  
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*The motor areas are located in '''both hemispheres''' of the cortex.  
  
'''Pyramidal tract''' connections are direct with no synapses in the brain stem. Axons pass through the ventral aspect of the medulla oblongata. The '''extrapyramidal tracts''' pass through the medulla oblongata outside the ventral pyramidal tracts and have synapses within the brain stem nuclei. These synapses make it possible for signals travelling down the extrapyramidal horns to be influenced by other areas of the brain including the cerebrum.  
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*They are shaped like a pair of headphones stretching from ear to ear.  
  
The pyramidal tracts are responsible for aspects of fine motor skills that require a degree of conscious thought and concentration. The extrapyramidal tracts are generally responsible for activation of larger muscle groups and often work in a coordinated manner to achieve smooth synchronous movements.
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*The motor areas are related to the controlling voluntary movements, especially fine fragmented movements.
  
===Limbic System===
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====Limbic System====
The Limbic system is made up of parts of the brain bordering the corpus collosum. The Limbic system contains areas of ''cerebral cortex'', the ''cingulate gyrus'' (dorsally), the ''parahippocampus gyrus'' (ventrally), the ''amygdala'', parts of the ''hypothalamus'' (mamillary body) and the ''hippocampus''. The Limbic system is principally responsible for emotions and the various types of emotion can affect the activity of the ''[[Autonomic_Nervous_System_-_Anatomy_%26_Physiology|Autonomic Nervous System]]'', facilitated by the hypothalamus. For example, anger can lead to increased heart rate and blood pressure.
 
  
===Olfactory Bulb===
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====Olfactory Bulb====
[[Image:ventral_brain.png|thumb|right|150px|''Ventral Brain with Olfactory bulbs rostral'' (Human), Grays Anatomy, 1918]]
 
The olfactory bulb is responsible for olfaction and the bulb itself is located within the rostral forebrain area, supported by the ''cribiform plate'' and the ''ethmoid bone''. The olfactory nerves are connected directly to the limbic system which is unique among mammalian sensory organs. As a result, olfaction plays a central role and is particularly important in regulating/stimulating sexual behaviour in many species.
 
  
{{Learning|videos = [[Video: Transverse Section of Cerebral Hemispheres|Transverse Section of Cerebral Hemispheres potcast]]<br>[[Video: Canine orbit and sagittal section of the canine head|Canine orbit and sagittal section of the canine head potcast]]<br>[[Video: Lateral surface of the head of the dog potcast 4|Lateral surface of the head of the dog potcast 4]]<br>[[Video: Ventral surface of the brain potcast|Ventral surface of the brain potcast]]}}
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==Species Differences==
  
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* Other than size the brain of most species is fairly consistant.
  
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==Links==
  
{{review}}
 
  
==Webinars==
 
<rss max="10" highlight="none">https://www.thewebinarvet.com/neurology/webinars/feed</rss>
 
  
 
[[Category:Nervous System - Anatomy & Physiology]]
 
[[Category:Nervous System - Anatomy & Physiology]]
[[Category:A&P Done]]
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[[Category:To Do - A&P]]

Revision as of 17:28, 12 March 2011



Introduction

The forebrain (proencephalon) is the largest part of the brain, most of which is cerebrum. Other important structures found in the forebrain include the thalamus , the hypothalamus and the limbic system. The cerebrum is divided into two cerebral hemispheres connected by a mass of white matter known as the corpus callosum. Each hemisphere is split into four lobes; the frontal, parietal, occipital and temporal lobes. The surface of each hemisphere is made up of grey matter known as the cerebral cortex and is folded to increase the surface area available within the skull. The cortex has roles within perception, memory and all higher thought processes. Inside the cortex is the white matter, within which are a number of nuclei (grey matter), known as the basal nuclei. The basal nuclei receive information from the cortex to regulate skeletal movement and other higher motor functions.

The thalamus functions to relay sensory information to the cerebral cortex and the hypothalamus, regulating visceral functions including temperature, reproductive functions, eating, sleeping and the display of emotion. The limbic system describes a collection of structures within the forebrain, including the amygdala hippocampus, also known as the 'emotional brain', the limbic system is important in the formation of memories and in making decisions and learning.

Structure and Function

Structures present Function
Forebrain (Proencephalon) Diencephalon - Thalamus, Hypothalamus, Pituitary

Telencephalon - Cerebral Cortex

Limbic System

Olfactory bulb

Thalamus - Organising sensory information

Hypothalamus - Endocrine System, Thermoregulation

Cerebral Cortex - Conciousness, language etc

Limbic System - Memory, motivation, emotion

Olfactory bulb - Smell


Thalamus

The thalamus has many functions:

  • Processes and relays sensory information selectively to various parts of the cerebral cortex.
  • Translates signals to the cerebral cortex from lower centres including auditory, somatic, visceral, gustatory and visual systems.
  • Regulates states of sleep and wakefulness.
  • The thalamus plays a major role in regulating arousal, the level of conciousness, and activity.

Hypothalamus

The function of the hypothalamus is mainly endocrine.

See Hypothalamus.

Pituitary

The function of the hypothalamus is mainly endocrine.

See Pituitary.

Cerebral Cortex

  • Essential for memory, attention, awareness, thought, language, and consciousness.
  • Outer layer of the cerebrum is grey matter.
  • Grey matter is formed by neurons and their unmyelinated fibres, (white matter below the grey matter of the cortex is formed predominantly by myelinated axons as myelin is white in appearance).
  • The surface of the cerebral cortex is folded in mammals; more than two thirds of the surface is within the grooves or "sulci".
  • The cerebral cortex is connected to structures such as the thalamus and the basal ganglia, sending information to them along efferent connections and receiving information from them via afferent connections.
  • Most sensory information is routed to the cerebral cortex via the thalamus.


The cortex is commonly described as comprising three parts: sensory, motor, and association areas:


Sensory areas

  • The sensory areas are the areas that receive and process information from the senses; INSERT HERE.
  • Inputs from the thalamus are called primary sensory areas.
  • Vision, hearing, and touch are processed by the primary visual cortex, primary auditory cortex and primary somatosensory cortex.
  • The two hemispheres receive information from the opposite (contralateral) side of the body.
  • Areas with lots of sensory innervation, such as the fingertips and the lips, require more cortical area to process finer sensation.


Association areas

  • Association areas function is to produce a perception of the world, so an animal can interact effectively.
  • The parietal, temporal, and occipital lobe - all located in the posterior part of the cortex - organize sensory information.
  • The frontal lobe or prefrontal association complex is involved in planning actions and movement.


Motor areas

  • The motor areas are located in both hemispheres of the cortex.
  • They are shaped like a pair of headphones stretching from ear to ear.
  • The motor areas are related to the controlling voluntary movements, especially fine fragmented movements.

Limbic System

Olfactory Bulb

Species Differences

  • Other than size the brain of most species is fairly consistant.

Links