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==Introduction==

==Introduction==

A reflex arc represents a mechanism by which a physiological function is automatically managed or regulated. Reflex arcs can be found throughout the body, ranging from [[Muscles_-_Anatomy_%26_Physiology#Skeletal_Muscle|skeletal muscles]] to [[Muscles_-_Anatomy_%26_Physiology#Smooth_Muscle|smooth muscle]] in glands. Reflex arcs are initiated via the excitation or stimulation of specific sensory cells that are directly connected to motor neurons thus enabling [[Spinal_Cord_-_Anatomy_%26_Physiology#Upper_and_Lower_Motor_Neurons|motor nerve]] impulses to be automatically passed on to that particular muscle or gland. Therefore a basic reflex arc consists of sensory cells and their associated nerve fibers, motor nerve fibres and the ultimate muscle or gland. Some reflex arcs can include a coordination centre within the spinal cord or brain prior to stimulation of the motor nerve. Reflex arcs can involve single or mutliple segments up and down the body, although reflex arcs do not require brain input in order to function. However, the brain can act to modulate reflexes. The brain obtains its afferent information via the ascending sensory tracts of the spinal cord. The descending tracts originate from the brain to allow responses to be modulated. These tracts constitute the white matter of the spinal cord.

A reflex arc represents a mechanism by which a physiological function is automatically managed or regulated. Reflex arcs can be found throughout the body, ranging from [[Muscles - Anatomy & Physiology#Skeletal Muscle|skeletal muscles]] to [[Muscles - Anatomy & Physiology#Smooth Muscle|smooth muscle]] in glands. Reflex arcs are initiated via the excitation or stimulation of specific sensory cells that are directly connected to motor neurons thus enabling [[Spinal Cord - Anatomy & Physiology#Upper and Lower Motor Neurons|motor nerve]] impulses to be automatically passed on to that particular muscle or gland. Therefore a basic reflex arc consists of '''sensory cells''' and their associated nerve fibers, '''motor nerve fibres''' and the ultimate '''muscle or gland'''.

 

Some reflex arcs can include a coordination centre within the spinal cord or brain prior to stimulation of the motor nerve. Reflex arcs can involve single or multiple segments up and down the body, although reflex arcs do not require brain input in order to function. However, the brain can act to modulate reflexes. The brain obtains its afferent information via the ascending sensory tracts of the spinal cord. The descending tracts originate from the brain to allow responses to be modulated. These tracts constitute the white matter of the spinal cord.

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A number of different sensory inputs are utilised by reflex arcs, including; skin receptors, muscle spindles, the retina, the [[Ear_-_Anatomy_%26_Physiology#Inner_Ear|Organ of Corti]] and the olfactory mucosa. These sensory aspects of reflex arcs feed into two main types of reflex systems in the body; '''Autonomic''' reflexes and '''Somatic''' reflexes.

A number of different sensory inputs are utilised by reflex arcs, including; skin receptors, muscle spindles, the retina, the [[Ear - Anatomy & Physiology#Inner Ear|organ of Corti]] and the olfactory mucosa. These sensory aspects of reflex arcs feed into two main types of reflex systems in the body; '''autonomic''' reflexes and '''somatic''' reflexes.

==Autonomic Reflexes==

==Autonomic Reflexes==

Autonomic reflexes control and regulate smooth muscle cells, cardiac muscle cells and glands. In general these reflexes contain the same basic components as somatic reflexes but a key difference is that autonomic reflexes have the ability to both stimulate or inhibit the smooth muscle/gland.

Autonomic reflexes control and regulate '''smooth muscle cells, cardiac muscle cells''' and '''glands'''. In general these reflexes contain the same basic components as somatic reflexes but a key difference is that autonomic reflexes have the ability to both stimulate or inhibit the smooth muscle/gland.

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For further information regarding the basic principles of the autonomic reflex arcs and for more detailed information, please see the [[Autonomic_Nervous_System_-_Anatomy_%26_Physiology#Autonomic_Nervous_System:_Basic_Principles|Autonomic Nervous System]].

For further information regarding the basic principles of the autonomic reflex arcs and for more detailed information, please see the [[Autonomic Nervous System - Anatomy & Physiology#Basic Principles|Autonomic Nervous System]].

==Somatic Reflexes==

==Somatic Reflexes==

Somatic reflexes are involved in the reflex control of skeletal muscles and as such there are many different types of somatic reflexes including '''withdrawal reflexes''', '''scratching reflexes''', '''withdrawal reflexes''' and '''stretch reflexes''' and '''tendon reflexes'''. A few of these will be covered in the section below.

Somatic reflexes are involved in the reflex control of '''skeletal muscles''' and as such there are many different types of somatic reflexes including '''scratching reflexes''', '''withdrawal reflexes''' and '''stretch reflexes''' and '''tendon reflexes'''. A few of these will be covered in the section below.

 

===Tendon Reflexes===

===Tendon Reflexes===

[[Muscles_-_Anatomy_%26_Physiology#Tendon|Tendons]] represent the weakest element of the musculoskeletal system and can be broken relatively easily compared to other aspects of the system. In some cases muscle contractions can be so powerful that the tendon either breaks or detaches and trauma can also have a similar effect. Tendon reflexes represent a reflex arc that is designed to prevent tendon damage from occurring.  

[[Muscles - Anatomy & Physiology#Tendon|Tendons]] represent the weakest element of the musculoskeletal system and can be broken relatively easily compared to other aspects of the system. In some cases, muscle contractions can be so powerful that the tendon either breaks or detaches and trauma can also have a similar effect. Tendon reflexes represent a reflex arc that is designed to prevent tendon damage from occurring.  

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[[Sensory_Pathways_-_Anatomy_%26_Physiology#Spinocerebellar_Tracts|Golgi tendon organs]] are the sensory organs located within the tendon adjacent to the junction between the tendon and the muscle. These sensory neurons are interwoven into the collagen fibres within the tendon and are able to depolarise in response to excess changes in shape of the tendon. These golgi tendon organs are connected to inhibitory inter-neurons within the spinal cord which in turn, are connected to motor neurons innervating the muscle connected to the tendon. The result of this reflex arc is that if the sensory neurons detect tendon stretch that is excessive, the muscle will relax to reduce the load on the tendon.

[[Sensory Pathways - Anatomy & Physiology#Spinocerebellar Tracts|Golgi tendon organs]] are the sensory organs located within the tendon adjacent to the junction between the tendon and the muscle. These sensory neurons are interwoven into the collagen fibres within the tendon and are able to depolarise in response to excess changes in shape of the tendon. These golgi tendon organs are connected to inhibitory inter-neurons within the spinal cord which in turn, are connected to motor neurons innervating the muscle connected to the tendon. The result of this reflex arc is that if the sensory neurons detect tendon stretch that is excessive, the muscle will relax to reduce the load on the tendon.

===Withdrawal Reflexes===

===Withdrawal Reflexes===

 

[[Category:Nervous System - Anatomy & Physiology]]

[[Category:Nervous System - Anatomy & Physiology]]

[[Category:To Do - Review]]

[[Category:A&P Done]]