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Protective structures: Vertebral column and the meninges provide

protect the spinal cord and provide physical stability.

a. Dura mater, b. Arachnoid, c. Pia mater Epidural space, subdural space and

subarachnoid space

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Two enlargements: cervical and lumbar Conus medullaris Filum terminale Cauda equina Posterior (dorsal root) & anterior(ventral) root Posterior (dorsal root) ganglion Spinal nerve

Anterior median fissure Posterior median sulcus Gray and white commissures Central canal Anterior, posterior & lateral gray horns Anterior, posterior & lateral white columns

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31 pairs; mixed nerves. Cervical (C1-C8), thoracic (T1-T12), lumbar

(L1-L5), sacral (S1-S5) and coccygeal. Connective tissue coverings of spinal nerves: Epineurium, perineurium and endoneurium: Fascicles

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Spinal nerves branch and their braches are called rami:

Posterior (dorsal) ramus Anterior (ventral) ramus Plexuses: a network of axons Anterior rami except T2-T12 form plexuses.

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Formed by the anterior

rami of C1-C5. Phrenic nerves-

important nerves from the cervical plexuses.

Formed by the anterior rami of C5-C8 & T1.

Supplies the shoulders and upper limbs.

Roots → trunks → divisions → cords → nerves.

Formed by the anterior rami of L1-L4.

Supplies the anterolateral abdominal wall, external genitals, and part of the lower limbs.

Femoral nerves, obturator nerves.

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Formed by the anterior rami of L4-L5 and S1-S4.

Supplies the buttocks, perineum, and lower limbs.

Gives rise to the largest nerve in the body- the sciatic nerve.

Formed by the anterior rami of S4-S5 and the coccygeal nerves.

Supplies a small area of skin in the coccygeal region.

Dermatome is the area of the skin that provides sensory input to the CNS via one pair of spinal nerves or the trigeminal nerve.

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The name of the tract often indicates its location in the white matter and where it begins and ends.

The white matter contains both sensory and motor tracts.

The pathway followed by nerve impulses that produce a reflex is a reflex arc.

A reflex arc includes: a. sensory receptor b. sensory neuron c. integrating center d. motor neuron e. effector

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Causes contraction of a skeletal muscle in response to stretching of the muscle.

Monosynaptic reflex. Patellar or knee-jerk reflex: Stretching of a

muscle →activation of muscle spindles →sensory neuron →spinal cord→motor neuron → muscle contraction.

Ipsilateral.

Polysynaptic reflex. Control muscle tension by causing muscle

relaxation when muscle tension is great. Sensory receptors- Golgi tendon organs. ↑ Tension applied to the tendon → tendon

organ stimulation → nerve impulse → spinal cord →motor neuron causes muscle relaxation and relieves tension.

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Polysynaptic reflex Ipsilateral. Stepping on a tack (stimulus) → nerve

impulse → activation of the interneuron → activation of the motor neuron →muscle contraction →withdrawal of the leg.

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Polysynaptic reflex. Contralateral reflex. Contraction of muscles that extend joints in the

opposite limb in response to a painful stimulus. Stepping on a tack (stimulus) → nerve impulse →activation of several interneurons → activation of the motor neurons → muscle contraction causing flexion of the leg stepping on a tack & extension on the opposite side.