Difference between revisions of "Spinal Cord - Anatomy & Physiology"
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− | {{ | + | {{unfinished}} |
− | == Introduction == | + | ==Introduction== |
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− | + | The spinal cord can be divided to several regions: <BR><BR> | |
− | < | ||
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− | + | <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. | |
− | The ''' | + | The '''forelimb nerves''' include: |
− | == | + | *Suprascapular (C5-6) |
− | [[ | + | *Musculocutaneous (C5-7) |
− | The spinal cord | + | *Ulna/median (Originates from the brachial plexus, which is formed from C5-T1) |
− | + | *Radial (C5-T1) | |
+ | |||
+ | |||
+ | The '''hindlimb nerves''' include: | ||
+ | |||
+ | *Obturator (L2-4) | ||
+ | *Femoral (L2-4) | ||
+ | *Sciatic (L4-S3) | ||
+ | |||
+ | The sciatic nerve 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: | ||
+ | **** [[Neurons - Anatomy & Physiology#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== | ==Vasculature== | ||
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− | + | * | |
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− | === | + | ==Innervation== |
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− | + | * | |
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==Lymphatics== | ==Lymphatics== | ||
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+ | * | ||
==Histology== | ==Histology== | ||
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− | + | * | |
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− | + | ==Species Differences== | |
− | + | * | |
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+ | ==Links== | ||
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− | + | [[Category:Nervous System - Anatomy & Physiology]] | |
− | [[Category: | + | [[Category:To Do - A&P]] |
− | [[Category:A&P |
Revision as of 20:35, 26 December 2010
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This article is still under construction. |
Introduction
The spinal cord can be divided to several regions:
Region | Segments |
---|---|
Cervical | C1-C6 |
Cervicothoracic | C7-T2 |
Thoracolumbar | T3-L3 |
Lumbosacral | L3-S2 |
Sacral | S3 onwards |
Nerves originating from the spinal cord and the segmental spinal nerves innervate the limbs.
The 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)
The hindlimb nerves include:
- Obturator (L2-4)
- Femoral (L2-4)
- Sciatic (L4-S3)
The sciatic nerve branches to the tibial nerve and the peroneal nerve.
Structure and Function
Structures Present | Function | ||
---|---|---|---|
Spinal Cord | Marginal layer - Axons, white matter
Mantle - Cell bodies, grey matter |
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==
Components
- The central nervous system consists of:
- The brain
- Prefix = "encephalo"
- The spinal cord
- Prefix = "myelo"
- The brain
Function
- 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.
White and Grey Matter
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:
- Oligodendrocytes in the CNS
- Myelinate several neurons at once.
- Respond poorly in injury.
- Schwann cells in the PNS
- Myelinate one axon only.
- Oligodendrocytes in the CNS
- Myelinated axons are wrapped in myelin
- 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.
Upper and Lower Motor Neurons
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
- This is characterised by:
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.
- Increased extensor tone, giving: