Anatomy and function of spinal cord | Neuromuscular system

Primary function of spinal cord

Acts a relay pathway between peripheral system and brain
- Provides sensory information regarding the environment to the brain
- Manages motor commands to the peripheral system in reaction to environment
- Coordinates simple reflexes that do not have to go to brain such as withdrawal from pain, patellar reflex, etc

Cervical spine
- Eight (8) nerves that provide innervation to neck and upper extremity
Thoracic spine
- Twelve (12) nerves that provide innervation to upper chest, chest, abdomen, upper back
Lumbar spine
- Five (5) nerves that provide innervation to legs and feet
Sacral spine
- Five (5) nerves that provide innervation to sacrum and pelvis
Cocxygeal spine
- One (1) nerve that provides innervation to the perineal area

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Dura mater
- Outermost protective layer
- Space between dura and bony vertebral body referred to as epidural space which contains adipose tissue and blood vessels
Arachnoid
- Middle layer with web-like appearance
- Space between dura and arachnoid referred to as subarachnoid space and contains cerebrospinal fluid
Pia mater
- innermost layer that is in direct contact with spinal cord

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Definitions

Dorsal root: Sensory nerve that carries information from spinal cord to brain
Ventral root: Motor nerve that carries information from brain to spinal cord
Spinal nerve: Pathway for sensory and motor information to move between peripheral system and spinal cord
Denticulate ligament: Ligament that provides stabilization of the spinal cord
Posterior (dorsal) gray horn: Nerve fibers containing sensory information from the body
Lateral gray horn: Nerve fibers containing sympathetic nervous system information only found in thoracic, upper lumbar, and sacral regions of spinal cord
Anterior (ventral) gray horn: Nerve fibers containing motor neurons that control skeletal muscles
Posterior (dorsal) white column:: Nerve fibers containing sensory information from the body such as two point discrimination, fine touch, vibration, and proprioception
Lateral white column: Nerve fibers that contain sensory information such as pain, temperature, and crude touch
Anterior (ventral) white column: Nerve fibers containing sensory and motor nerve fibers that provide information to the contralateral brain
Sympathetic nervous system: Network of nerves that are enacted to aid in the response to physical activity, stress, or danger (fight or flight response)
Parasympathetic nervous system: Network of nerves that provide relaxation after the body has responded to stressful or dangerous situation (rest and digest response)

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Ascending tracts
- Carry sensory information such as touch, pain, and temperature from peripheral system to brain
- Names of tracts/pathways:
  - Dorsal column-medial lemniscal: transmit light touch, deep pressure, two-point discrimination, and vibratory information to cerebrum via the thalamus- crosses in the medulla to the contralateral side
  - Anterior and lateral spinothalamic: transmit pain, crude touch, and temperature information to cerebrum via the thalamus- crosses in the medulla to the contralateral side
  - Spinocerebellar: transmit proprioceptive information to the cerebellar- does not cross; stays on same side

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Descending tracts
- Carry motor information from brain to peripheral system to give voluntary commands of movement of axial and skeletal muscles
- Names of tracts/pathway:
  - Anterior and lateral corticospinal: transmit commands to move axial and/or skeletal muscles

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Two (2) primary arteries of spinal cord
- Anterior spinal artery
  - Supplies blood to the anterior two-thirds of the spinal cord with the exception of dorsal column
- Posterior spinal artery
  - Provides blood supply to posterior spinal cord via two (2) branches that supply the dorsal sensory column, dorsal grey matter, and posterior columns