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Sensory Pathways - Anatomy & Physiology (view source)
Revision as of 14:33, 14 August 2009
, 14:33, 14 August 2009New page: {{review}} {{toplink |linkpage =Nervous and Special Senses - Anatomy & Physiology |linktext =Nervous and Special Senses |maplink = Nervous System and Special Senses (Content Map) - Anatom...
{{review}}
{{toplink
|linkpage =Nervous and Special Senses - Anatomy & Physiology
|linktext =Nervous and Special Senses
|maplink = Nervous System and Special Senses (Content Map) - Anatomy & Physiology
|pagetype =Anatomy
}}
<br>
==Introduction==
Sensory information at our peripheries ascends through the [[Spinal Cord - Anatomy & Physiology|spinal cord]] and enters the higher levels of the brain. There are numerous pathways which allow different types of information to be passed to the brain. Types of general somatic sensation include:
# Pain
# Touch
# Temperature
# Kinaesthesia (conscious proprioception)
Sensory information is sent to one of two destinations:
*The '''[[Forebrain - Anatomy & Physiology#Cerebral Cortex|cerebral cortex]]'''
**Information first passes via the [[Forebrain - Anatomy & Physiology#Thalamus|thalamus]].
**The signal may be relayed one or more times by the [[Forebrain - Anatomy & Physiology#Thalamus|thalamus]] en route to the [[Forebrain - Anatomy & Physiology#Cerebral Cortex|cortex]].
**The information reaches consciousness.
*The '''[[Hindbrain - Anatomy & Physiology#Cerebellum|cerebellum]]'''
**The [[Hindbrain - Anatomy & Physiology#Cerebellum|cerebellum]] is involved in co-ordination.
**The information does not reach consciousness.
==Pathways==
===Ascending Pathways===
[[Image:The Ascending Pathways.jpg|thumb|right|150px|Ascending Pathways - © Sarah Hamilton 2008]]
*Sensory information enters the [[Spinal Cord - Anatomy & Physiology|spinal cord]] on the same side of the body as the stimulus.
*Ascending tracts cross over the midline of the body to the contralateral side of the [[Forebrain - Anatomy & Physiology#Thalamus|thalamus]].
*The [[Forebrain - Anatomy & Physiology#Thalamus|thalamus]] directs the signal to the [[Forebrain - Anatomy & Physiology#Cerebral Cortex|cerebral cortex]] for conscious perception.
**The pathway is direct, with very few [[Nervous System - PNS - Anatomy & Physiology#Nerve Fibre|neurones]] involved.
====1. Dorsal Columns====
*Transmits information from touch and kinaesthesia, i.e low threshold information.
*There are two major dorsal columns:
** '''The gracile fasiculus'''
*** Situated medially.
*** Conveys information from the hindlimbs and caudal trunk.
** '''The cuneate fasciculus'''
*** Situated more laterally.
*** Conveys information from the forelimbs and cranial trunk.
====2. Spinothalamic Tracts====
*Transmits information from temperature and "pin prick" pain.
*Fast, intial pain sensation
*Compare with [[Nervous System - Sensory Pathways - Anatomy & Physiology#Ascending Reticular Formation|ascending reticular formation]]
====3. Spinocervicothalamic Tracts====
*Transmits information from touch and kinaesthesia.
*Absent in man
===Spinocerebellar Tracts===
[[Image:TheSpinocerebellarTract.jpg|thumb|right|150px|Spinocerebellar Tract - © Sarah Hamilton 2008]]
*Transmits information from proprioception receptors, including information from muscle receptors, joint receptors and golgi tendon organs.
*Most sensory information enters the [[Spinal Cord - Anatomy & Physiology|spinal cord]] on the ipsilateral side to the stimulus, some crosses to the contralateral side of the body.
**Contralateral signals pass back to the ipsilateral side of the body in the brain.
*Information is processed in the [[Hindbrain - Anatomy & Physiology#Cerebellum|cerebellum]] and is therefore processed unconsciously.
*The '''dorsal spinocerebellar tract''' relays muscle spindle and Golgi tendon organ information from the hindlimbs to the [[Hindbrain - Anatomy & Physiology#Cerebellum|cerebellum]].
* The '''cuneo-cerebellar tract''' serves the same purpose for the forelimbs, but is much smaller.
* The '''ventral spinocerebellar tract''' is similar to the dorsal spinocerebellar tract but it takes a less direct route to the [[Hindbrain - Anatomy & Physiology#Cerebellum|cerebellum]].
** The forelimb equivalent is called the '''rostral spinocerebellar tract'''.
===Ascending Reticular Formation (Spinoreticular Tract)===
[[Image:AscendingReticularFormation.jpg|thumb|right|150px|Ascending Reticular Formation - © Sarah Hamilton 2008]]
*True pain sensation; pain lasts longer.
*Sensory information enters the [[Spinal Column - Anatomy & Physiology|spinal cord]] on the ipsilateral side of the stimulus. Some signals cross to the contralateral side of the body.
*The tract consists of '''several''' [[Nervous System - PNS - Anatomy & Physiology#Nerve Fibre|short neurones]].
*Therfore the ascending reticular formation is ''bilateral'' and ''multineuronal''.
*This pain pathway is more primitive than the [[Nervous System - Sensory Pathways - Anatomy & Physiology#Spinothalamic Tract|spinothalmic tract]].
**In '''man''', the ascending reticular formation is superceeded by the [[Nervous System - Sensory Pathways - Anatomy & Physiology#Spinothalamic Tract|spinothalamic tract]]. In '''animals''', the ascending reticular formation is the '''main pathway''' for pain to reach the [[Forebrain - Anatomy & Physiology#Cerebral Cortex|cerebral cortex]].
==Pain==
*"Painful stimuli" can range from itches, to nausea, to being in agony.
*Painful stimuli may be transmitted to the brain by one of two pathways:
::[[Nervous System - Sensory Pathways - Anatomy & Physiology#Spinothalamic Tract|Spinothalamic Tract]]
::[[Nervous System - Sensory Pathways - Anatomy & Physiology#Ascending Reticular Formation|Ascending Reticular Formation]]
'''Spinothalamic Tract'''
*Fast, initial pinprick is detected by free [[Nervous System - PNS - Anatomy & Physiology#Nerve Fibres|nerve]] endings
*Causes an impulse along large, myelinated fibres
*Pain sensation is localised, and ends quickly
'''Ascending Reticular Formation'''
*A painful sensation is detected by free [[Nervous System - PNS - Anatomy & Physiology#Nerve Fibres|nerve]] endings
*Causes an impulse along small, unmyelinated fibres
*A delayed sensation of pain is percieved, that is less localised, persistent.
'''Clinical Relevance'''
*In trauma, the small unmyelinated fibres are the last fibres to fail as they are close to the [[Spinal Cord - Anatomy & Physiology|spinal cord]].
**If deep pain sensation is lost in a case of trauma, then the prognosis is poor.
*''Hyperalgesia'' is an increased pain sensation. Occurs when tissue is damaged because chemicals are released which increase the sensitivity of nociceptors, so that even light pressure can cause pain.
**May have evolved to aid the healing of injuries.
===Visceral Pain===
*This refers to pain of the internal organs.
*Pain may be extreme, especially with distension, but the body's ability to localise the pain is poor.
**Skeletal muscle spasms may be observed.
*Commonly, the pain is referred to a different part of the body that is unharmed. This is because the areas are served by the same part of the [[Spinal Cord - Anatomy & Physiology|spinal cord]] e.g. in angina (pain in the heart), pain can be felt in the inner left arm or jaw.
**This is called '''referred pain'''.
==Links==
*[[Nervous System - Pathology|Pathology of the Nervous System]]
*[[Nervous System - Pathways - Anatomy & Physiology - Flashcards|Pathways Revision Flashcards]]
{{toplink
|linkpage =Nervous and Special Senses - Anatomy & Physiology
|linktext =Nervous and Special Senses
|maplink = Nervous System and Special Senses (Content Map) - Anatomy & Physiology
|pagetype =Anatomy
}}
<br>
==Introduction==
Sensory information at our peripheries ascends through the [[Spinal Cord - Anatomy & Physiology|spinal cord]] and enters the higher levels of the brain. There are numerous pathways which allow different types of information to be passed to the brain. Types of general somatic sensation include:
# Pain
# Touch
# Temperature
# Kinaesthesia (conscious proprioception)
Sensory information is sent to one of two destinations:
*The '''[[Forebrain - Anatomy & Physiology#Cerebral Cortex|cerebral cortex]]'''
**Information first passes via the [[Forebrain - Anatomy & Physiology#Thalamus|thalamus]].
**The signal may be relayed one or more times by the [[Forebrain - Anatomy & Physiology#Thalamus|thalamus]] en route to the [[Forebrain - Anatomy & Physiology#Cerebral Cortex|cortex]].
**The information reaches consciousness.
*The '''[[Hindbrain - Anatomy & Physiology#Cerebellum|cerebellum]]'''
**The [[Hindbrain - Anatomy & Physiology#Cerebellum|cerebellum]] is involved in co-ordination.
**The information does not reach consciousness.
==Pathways==
===Ascending Pathways===
[[Image:The Ascending Pathways.jpg|thumb|right|150px|Ascending Pathways - © Sarah Hamilton 2008]]
*Sensory information enters the [[Spinal Cord - Anatomy & Physiology|spinal cord]] on the same side of the body as the stimulus.
*Ascending tracts cross over the midline of the body to the contralateral side of the [[Forebrain - Anatomy & Physiology#Thalamus|thalamus]].
*The [[Forebrain - Anatomy & Physiology#Thalamus|thalamus]] directs the signal to the [[Forebrain - Anatomy & Physiology#Cerebral Cortex|cerebral cortex]] for conscious perception.
**The pathway is direct, with very few [[Nervous System - PNS - Anatomy & Physiology#Nerve Fibre|neurones]] involved.
====1. Dorsal Columns====
*Transmits information from touch and kinaesthesia, i.e low threshold information.
*There are two major dorsal columns:
** '''The gracile fasiculus'''
*** Situated medially.
*** Conveys information from the hindlimbs and caudal trunk.
** '''The cuneate fasciculus'''
*** Situated more laterally.
*** Conveys information from the forelimbs and cranial trunk.
====2. Spinothalamic Tracts====
*Transmits information from temperature and "pin prick" pain.
*Fast, intial pain sensation
*Compare with [[Nervous System - Sensory Pathways - Anatomy & Physiology#Ascending Reticular Formation|ascending reticular formation]]
====3. Spinocervicothalamic Tracts====
*Transmits information from touch and kinaesthesia.
*Absent in man
===Spinocerebellar Tracts===
[[Image:TheSpinocerebellarTract.jpg|thumb|right|150px|Spinocerebellar Tract - © Sarah Hamilton 2008]]
*Transmits information from proprioception receptors, including information from muscle receptors, joint receptors and golgi tendon organs.
*Most sensory information enters the [[Spinal Cord - Anatomy & Physiology|spinal cord]] on the ipsilateral side to the stimulus, some crosses to the contralateral side of the body.
**Contralateral signals pass back to the ipsilateral side of the body in the brain.
*Information is processed in the [[Hindbrain - Anatomy & Physiology#Cerebellum|cerebellum]] and is therefore processed unconsciously.
*The '''dorsal spinocerebellar tract''' relays muscle spindle and Golgi tendon organ information from the hindlimbs to the [[Hindbrain - Anatomy & Physiology#Cerebellum|cerebellum]].
* The '''cuneo-cerebellar tract''' serves the same purpose for the forelimbs, but is much smaller.
* The '''ventral spinocerebellar tract''' is similar to the dorsal spinocerebellar tract but it takes a less direct route to the [[Hindbrain - Anatomy & Physiology#Cerebellum|cerebellum]].
** The forelimb equivalent is called the '''rostral spinocerebellar tract'''.
===Ascending Reticular Formation (Spinoreticular Tract)===
[[Image:AscendingReticularFormation.jpg|thumb|right|150px|Ascending Reticular Formation - © Sarah Hamilton 2008]]
*True pain sensation; pain lasts longer.
*Sensory information enters the [[Spinal Column - Anatomy & Physiology|spinal cord]] on the ipsilateral side of the stimulus. Some signals cross to the contralateral side of the body.
*The tract consists of '''several''' [[Nervous System - PNS - Anatomy & Physiology#Nerve Fibre|short neurones]].
*Therfore the ascending reticular formation is ''bilateral'' and ''multineuronal''.
*This pain pathway is more primitive than the [[Nervous System - Sensory Pathways - Anatomy & Physiology#Spinothalamic Tract|spinothalmic tract]].
**In '''man''', the ascending reticular formation is superceeded by the [[Nervous System - Sensory Pathways - Anatomy & Physiology#Spinothalamic Tract|spinothalamic tract]]. In '''animals''', the ascending reticular formation is the '''main pathway''' for pain to reach the [[Forebrain - Anatomy & Physiology#Cerebral Cortex|cerebral cortex]].
==Pain==
*"Painful stimuli" can range from itches, to nausea, to being in agony.
*Painful stimuli may be transmitted to the brain by one of two pathways:
::[[Nervous System - Sensory Pathways - Anatomy & Physiology#Spinothalamic Tract|Spinothalamic Tract]]
::[[Nervous System - Sensory Pathways - Anatomy & Physiology#Ascending Reticular Formation|Ascending Reticular Formation]]
'''Spinothalamic Tract'''
*Fast, initial pinprick is detected by free [[Nervous System - PNS - Anatomy & Physiology#Nerve Fibres|nerve]] endings
*Causes an impulse along large, myelinated fibres
*Pain sensation is localised, and ends quickly
'''Ascending Reticular Formation'''
*A painful sensation is detected by free [[Nervous System - PNS - Anatomy & Physiology#Nerve Fibres|nerve]] endings
*Causes an impulse along small, unmyelinated fibres
*A delayed sensation of pain is percieved, that is less localised, persistent.
'''Clinical Relevance'''
*In trauma, the small unmyelinated fibres are the last fibres to fail as they are close to the [[Spinal Cord - Anatomy & Physiology|spinal cord]].
**If deep pain sensation is lost in a case of trauma, then the prognosis is poor.
*''Hyperalgesia'' is an increased pain sensation. Occurs when tissue is damaged because chemicals are released which increase the sensitivity of nociceptors, so that even light pressure can cause pain.
**May have evolved to aid the healing of injuries.
===Visceral Pain===
*This refers to pain of the internal organs.
*Pain may be extreme, especially with distension, but the body's ability to localise the pain is poor.
**Skeletal muscle spasms may be observed.
*Commonly, the pain is referred to a different part of the body that is unharmed. This is because the areas are served by the same part of the [[Spinal Cord - Anatomy & Physiology|spinal cord]] e.g. in angina (pain in the heart), pain can be felt in the inner left arm or jaw.
**This is called '''referred pain'''.
==Links==
*[[Nervous System - Pathology|Pathology of the Nervous System]]
*[[Nervous System - Pathways - Anatomy & Physiology - Flashcards|Pathways Revision Flashcards]]