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Spinal Cord - Anatomy & Physiology (view source)
Revision as of 14:26, 14 August 2009
, 14:26, 14 August 2009New page: {{unfinished}} {{toplink |linkpage =Nervous and Special Senses - Anatomy & Physiology |linktext =Nervous and Special Senses |maplink = Nervous System and Special Senses (Content Map) - Ana...
{{unfinished}}
{{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==
* The spinal cord can be divided to several regions: <BR><BR>
<center>
{| border="3" cellpadding="8"
!width="150"|'''<u>Region</u>'''
!width="300"|'''<u>Segments</u>'''
|-
|Cervical
|C1-C6
|-
|Cervicothoracic
|C7-T2
|-
|Thoracolumbar
|T3-L3
|-
|Lumbosacral
|L3-S2
|-
|Sacral
|S3 onwards
|}
</center><BR>
* Nerves originating from the spinal cord and the segmental spinal nerves innervate the limbs.
** Forelimb nerves include:
*** Suprascapular (C5-6)
*** Musculocutaneous (C5-7)
*** Ulna/median
**** Originates from the brachial plexus, which is formed from C5-T1.
*** Radial (C5-T1)
** Hindlimb nerves include:
*** Obturator (L2-4)
*** Femoral (L2-4)
*** Sciatic (L4-S3)
**** Branches to the tibial nerve and the peroneal nerve.
==Structure and Function==
{| style="width:75%; height:200px" border="1"
!
!'''Structures Present'''
!'''Function'''
|-
| '''Spinal Cord'''
| '''[[Spinal Cord - Anatomy & Physiology#Marginal layer|Marginal layer]]''' - Axons, white matter
'''[[Spinal Cord - Anatomy & Physiology#Mantle|Mantle]]''' - Cell bodies, grey matter
'''[[Spinal Cord - Anatomy & Physiology#Spinal Canal|Spinal canal]]'''
| Conducts sensory information from the peripheral nervous system (both somatic and autonomic) to the brain, conducts motor information from the brain to various effectors and acts as a minor reflex center.
|
|}
====Marginal Layer====
====Mantle====
====Spinal Canal====
==Function==
*==Basic Concepts==
[[Image:cerebrumbrainstemcerebellum.jpg|thumb|right|150px|Cerebrum, brain stem and cerebellum. Image courtesy of BioMed Archive]]
===<u>Components</u>===
* The central nervous system consists of:
** The brain
*** Prefix = "encephalo"
** The spinal cord
*** Prefix = "myelo"
===<u>Function</U>===
# Sensory neurons from both the internal and external environment relay information to the CNS.
# The CNS processes sensory information and intitiates motor outputs.
# Effector and motor neurons from the CNS relay the appropriate outputs to effector organs.
====The Autonomic Nervous System====
* The autonomic nervous system relays sensory information from, and motor information to, the '''internal environment'''.
** It therefore plays an important role in the maintenance of homeostasis.
====The Somatosensory Nervous System====
* The somatosensory nervous system relays sensory information from, and motor information to, the '''external environment'''.
===<u>White and Grey Matter</u>===
====White Matter====
* White matter consists of accumulations of myelinated axons.
** Myelinated axons are wrapped in '''myelin'''
*** Myelin is compsed of lipid and protein in an 80:20 ratio.
*** It insulates axons to give efficient action potential conduction.
*** Myelin is provided by:
**** [[Microscopic Anatomy of the CNS#Oligodendrocytes|Oligodendrocytes]] in the CNS
***** Myelinate several neurons at once.
***** Respond poorly in injury. [[Image:Braincosssection.jpg|thumb|right|150px|White and grey matter. Image courtesy of BioMed Archive]]
**** Schwann cells in the PNS
***** Myelinate one axon only.
* A "funiculus" is a large region of white matter in the spinal cord.
====Grey Matter====
* The outer portions of the cerebral cortex and the inner portions of the spinal cord are composed of grey matter.
** Grey matter is also found in coloumns and scattered in brainstem nuclei.
* Composed of neuronal cell bodies, plus glial cells.
===<u>Upper and Lower Motor Neurons</u>===
====Lower Motor Neuron (LMN)====
* LMNs are efferent neurons which connect the CNS to smooth or skeletal muscle.
** Autonomic LMNs connect to smooth muscle.
** Somatic LMNs connect to skeletal muscle.
*** Those innervating the muscles of the axial and peripheral skeleton have their cells bodies in the ventral horn of the spinal cord.
* Injury causes LMN weakness.
** This is characterised by:
*** Depressed reflexes
*** Decreased tone
*** Neurogenic muscle atrophy
====Upper Motor Neuron (UMN)====
* The upper motor neuron comprises the motor system of the CNS. This is responsible for:
** Initiating voluntary movement.
** Maintenance of tone and posture.
* In man, direct connections exist between neurons in the motor cortex and LMNs in the spinal cord.
** This is known as the "pyramidal system".
* In animals, there are scattered groups of interconnected neurons in the cortex and brainstem, which ultimately synapse with LMNs in the brainstem and spinal cord.
** The "extrapyramidal system".
* UMN injury results in:
*# Increased extensor tone, giving:
*#* Stiffness
*#* Spasticity
*# Delay in the onset of protraction, and a longer stride
*# Disinhibition of the LMN relfex ability.
*#* This causes increased reflexes.
*# Inability to stimulate LMN.
*#* UMN weakness results.
==Vasculature==
*
==Innervation==
*
==Lymphatics==
*
==Histology==
*
==Species Differences==
*
==Links==
{{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==
* The spinal cord can be divided to several regions: <BR><BR>
<center>
{| border="3" cellpadding="8"
!width="150"|'''<u>Region</u>'''
!width="300"|'''<u>Segments</u>'''
|-
|Cervical
|C1-C6
|-
|Cervicothoracic
|C7-T2
|-
|Thoracolumbar
|T3-L3
|-
|Lumbosacral
|L3-S2
|-
|Sacral
|S3 onwards
|}
</center><BR>
* Nerves originating from the spinal cord and the segmental spinal nerves innervate the limbs.
** Forelimb nerves include:
*** Suprascapular (C5-6)
*** Musculocutaneous (C5-7)
*** Ulna/median
**** Originates from the brachial plexus, which is formed from C5-T1.
*** Radial (C5-T1)
** Hindlimb nerves include:
*** Obturator (L2-4)
*** Femoral (L2-4)
*** Sciatic (L4-S3)
**** Branches to the tibial nerve and the peroneal nerve.
==Structure and Function==
{| style="width:75%; height:200px" border="1"
!
!'''Structures Present'''
!'''Function'''
|-
| '''Spinal Cord'''
| '''[[Spinal Cord - Anatomy & Physiology#Marginal layer|Marginal layer]]''' - Axons, white matter
'''[[Spinal Cord - Anatomy & Physiology#Mantle|Mantle]]''' - Cell bodies, grey matter
'''[[Spinal Cord - Anatomy & Physiology#Spinal Canal|Spinal canal]]'''
| Conducts sensory information from the peripheral nervous system (both somatic and autonomic) to the brain, conducts motor information from the brain to various effectors and acts as a minor reflex center.
|
|}
====Marginal Layer====
====Mantle====
====Spinal Canal====
==Function==
*==Basic Concepts==
[[Image:cerebrumbrainstemcerebellum.jpg|thumb|right|150px|Cerebrum, brain stem and cerebellum. Image courtesy of BioMed Archive]]
===<u>Components</u>===
* The central nervous system consists of:
** The brain
*** Prefix = "encephalo"
** The spinal cord
*** Prefix = "myelo"
===<u>Function</U>===
# Sensory neurons from both the internal and external environment relay information to the CNS.
# The CNS processes sensory information and intitiates motor outputs.
# Effector and motor neurons from the CNS relay the appropriate outputs to effector organs.
====The Autonomic Nervous System====
* The autonomic nervous system relays sensory information from, and motor information to, the '''internal environment'''.
** It therefore plays an important role in the maintenance of homeostasis.
====The Somatosensory Nervous System====
* The somatosensory nervous system relays sensory information from, and motor information to, the '''external environment'''.
===<u>White and Grey Matter</u>===
====White Matter====
* White matter consists of accumulations of myelinated axons.
** Myelinated axons are wrapped in '''myelin'''
*** Myelin is compsed of lipid and protein in an 80:20 ratio.
*** It insulates axons to give efficient action potential conduction.
*** Myelin is provided by:
**** [[Microscopic Anatomy of the CNS#Oligodendrocytes|Oligodendrocytes]] in the CNS
***** Myelinate several neurons at once.
***** Respond poorly in injury. [[Image:Braincosssection.jpg|thumb|right|150px|White and grey matter. Image courtesy of BioMed Archive]]
**** Schwann cells in the PNS
***** Myelinate one axon only.
* A "funiculus" is a large region of white matter in the spinal cord.
====Grey Matter====
* The outer portions of the cerebral cortex and the inner portions of the spinal cord are composed of grey matter.
** Grey matter is also found in coloumns and scattered in brainstem nuclei.
* Composed of neuronal cell bodies, plus glial cells.
===<u>Upper and Lower Motor Neurons</u>===
====Lower Motor Neuron (LMN)====
* LMNs are efferent neurons which connect the CNS to smooth or skeletal muscle.
** Autonomic LMNs connect to smooth muscle.
** Somatic LMNs connect to skeletal muscle.
*** Those innervating the muscles of the axial and peripheral skeleton have their cells bodies in the ventral horn of the spinal cord.
* Injury causes LMN weakness.
** This is characterised by:
*** Depressed reflexes
*** Decreased tone
*** Neurogenic muscle atrophy
====Upper Motor Neuron (UMN)====
* The upper motor neuron comprises the motor system of the CNS. This is responsible for:
** Initiating voluntary movement.
** Maintenance of tone and posture.
* In man, direct connections exist between neurons in the motor cortex and LMNs in the spinal cord.
** This is known as the "pyramidal system".
* In animals, there are scattered groups of interconnected neurons in the cortex and brainstem, which ultimately synapse with LMNs in the brainstem and spinal cord.
** The "extrapyramidal system".
* UMN injury results in:
*# Increased extensor tone, giving:
*#* Stiffness
*#* Spasticity
*# Delay in the onset of protraction, and a longer stride
*# Disinhibition of the LMN relfex ability.
*#* This causes increased reflexes.
*# Inability to stimulate LMN.
*#* UMN weakness results.
==Vasculature==
*
==Innervation==
*
==Lymphatics==
*
==Histology==
*
==Species Differences==
*
==Links==