Spinal Cord and Spinal Nerves

thin strand of pia mater at the end

Filum terminale

nerve roots that project inferiorly from the spinal cord

Cauda equina

terminal spinal cord at L1, stops at age 4

Conus medullaris

above the dura

Spinal Cord Meninges - Epidural space

below epidural space

Spinal Cord Meninges - dura matter

potential space between dura mater and arachnoid mater

Spinal Cord Meninges - Subdural space:

middle membrane, delicate/web-like extension

Spinal Cord Meninges - Arachnoid mater

(contains cerebral fluid CSF)

Subarachnoid space

innermost layer, inseparable from spinal cord/brain

Pia mater

centrally located, and its shape resembles a letter H or a butterfly

gray matter

• contains axons of sensory neurons

• cell bodies (nuclei) of interneuron

gray matter - posterior horns

posterior horns - Aferent or Eferent?

aferent (sensory)

posterior horns - Structural classification of neuron

• somatic sensory

  • pain & pressure

• visceral sensory

  • smooth muscle & ligands

• posterior root ganglion

  • collection of cell bodies of sensory neurons

posterior horns inntervates

• pain

• pressure

  • other sensory inputs

gray matter - anterior horns

somatic motor neurons that innervate skeletal muscles

Eferent

Anterior Horn - Aferent or Eferent?

Motor

Anterior Horn - Sensory or Motor?

Anterior Horn - Contains cell bodies, axons, both or neither?

• cell bodies of somatic motor neurons -

  • innervate skeletal muscle

Somatic motor neurons

Anterior Horn - Structural classifcaton of neuron

• innervates skeletal muscle

Anterior Horn - Innervates

• contains cell bodies of autonomic (visceral) motor neurons

  • innervate smooth muscle, cardiac muscle, glands (unaware)

gray matter - lateral horns

Eferent

lateral horns - Aferent or Eferent?

Motor

lateral horns - Sensory or Motor?

lateral horns - Contains cell bodies, axons, both or neither?

cell bodies of autonomic (visceral) motor neurons

• smooth muscle

• cardiac muscle

• glands

lateral horns - Innervates

autonomic visceral motor neurons

lateral horn - Structural classifcaton of neuron

collection of cell bodies of sensory neurons

Posterior Horn –Posterior root ganglion

• Innervate the muscles of the neck - C1–C4t

  • Phrenic nerve: extends down, diaphragm

Cervical Plexus

Supply upper limbs

Brachial Plexus

1. axillary nerve

2. median nerve

3. musculocutaneous nerve

4. radial nerve

5. ulnar nerve

Brachial Plexus - fivevmajor terminal branches

• Innervate the abdomen, some external genitalia, anterior & medial thigh

Lumbar Plexus

Sacral Plexus

• Innervate

  • Pelvis

  • Posterior thigh

  • Leg

  • Foot

• main nerve: sciatic nerve

• largest & longest nerve in the body

• No thoracic pletus

Intercostal nerve

Reflexes - Characteristcs:

1. stimulus

2. Rapid

3. automatic

4. involuntary

1. Receptor responds

2. Sensory neuron to spinal cord Integration –sometimes by

3. integration - Interneuron (monosynaptic & polysynaptic)

4. Motor neuron to effector

5. Effector responds

Five Steps in a Simple Reflex

receptor and effector on same side

Ipsilateral–

receptor & efector on opposite sides

Contralateral

does not involve interneuron

• Ex. Knee-jerk (stretch reflex)

monosynaptic

involve interneurons Ex. With drawl reflex

polysynaptic –

Motor innervation: Deltoid & teres minor

Action: Arm Abduction

sensory innervation: superolateral arm (shoulder)

Axillary Nerve

Motor innervation: anterior forearm muscle, thumb, lumbricals

Action: wrist, digit flexors

sensory innervation: palmer aspect, lateral 3 ½ digits (thumb, index, middle, & ½ ring finger)

median nerve

• Motor innervation: anterior arm muscles - Iflex humerus, flex elbow joint, supinate forearm)

  • coracobrachialis

  • bicep brachii

  • brachialis

• Action: forearm flexors

• sensory innervation: later region of forearm

Musculocutaneous Nerve

• Motor innervation:

  • posterior arm muscle

  • posterior forearm muscle

  • brachioradialis

• Action: forearm, wrist, digit, extensor

• sensory innervation: arm, forearm, dorsal aspect of lateral 3 digits (except distal tips)

Radial Nerve

• Motor innervation:

  • anterior forarm muscle

  • intrinsic hand muscle

• Action: wrist, digit flexors

• sensory innervation: dorsal and palmar aspects of medial 1 ½ digits (little finger, medial aspect of ring finger)

ulnar nerve