A&P Lab 8 - Nerves and Spinal Cord

Dendrites

short branches extending from cell body

Cell Body (Soma)

contains large nucleus and nucleolus

Axon Hillock

where axon attaches to cell body and where action potential gathers before propagating down axon

Myelin sheath (Schwann cell)

forms around axons to insulate axon for rapid propagation of action potentials

Node of Ranvier

areas between schwann cells where action potentials can more rapidly jump

Axon terminal

where a neuron meets up with other neurons to pass action potentials down the chain

Spinal cord

extension of brain into vertebral column where spinal nerves emergge from and pass through intervertebral foramen

Meninges

protective membranes of spinal cord

Conus medullaris

tapered, conical end of cord at L1/L2 (light green)

Cauda equina

nerve roots extend below conus medullaris, “horse tail” (dark green)

Filum terminale

thin threads of fibrous tissue at end of conus medullaris

Dorsal root

axons of sensory neurons (top indication)

Dorsal root ganglion

contain cell bodies of sensory neurons in dorsal root

Ventral root

axons of motor neurons (bottom indication)

Posterior median sulcus

grooves dividing spinal cord left/right

Anterior median fissure

grooves dividing spinal cord left/right

Central canal

middle hole, contains cerebrospinal fluid

White matter parts

anterior, posterior, lateral white columns

Anterior white column

Posterior white column

Lateral white column

Gray matter parts

posterior, anterior, lateral gray horns

Gray commissure

Anterior gray horn

somatic motor nuclei, CNS to skeletal muscles

Posterior gray horn

somatic and visceral sensory nuclei, receptors to CNS

Lateral gray horn

visceral motor nucleus, CNS to other effectors

Epidural space

Dura mater

Arachnoid mater

Subarachnoid space

Pia mater

8 cervical spinal nerves (CSN 1-8)

12 thoracic spinal nerves (TSN 1-12)

5 lumbar spinal nerves (LSN 1-5)

5 sacral spinal nerves (SSN 1-5)

Cervical plexus nerve(s)

phrenic nerve

Phrenic nerve

Brachial Plexus Nerve(s)

axillary, musculocutaneous, radial, median, ulnar

Lateral cord

Musculocutaneous nerve

Median nerve (1/2)

Medial cord

Median nerve (1/2)

Ulnar nerve

Posterior cord

Axillary nerve

Radial nerve

Lumbosacral plexus nerve(s)

obturator, femoral, gluteal, sciatic, tibial, common fibular

Femoral nerve

Obturator nerve

Gluteal nerve

Sciatic nerve

Tibial nerve

Common fibular nerve

Patellar reflex

curling of toes, present in healthy adults

Calcaneal (achilles) reflex

plantar flexion when calcaneus/achilles is hit

Plantar (babinski) reflex

spreading of toes without plantar flexion, normal in infants, pathological in adults

Withdrawl (flexor) reflex

removal of body part away from pain stimulus

Crossed extensor reflex

stimulation of opposite limb to maintain balance away from painful stimulus

Phrenic nerve muscle innervation

diaphragm

Axillary nerve muscle innervation

deltoid

Musculocutaneous nerve muscle innervation

biceps brachii

Radial nerve muscle innervation

all forearm extensors

Median nerve muscle innervation

lateral flexors of forearm

Ulnar nerve muscle innervation

medial flexors of forearm

Obturator nerve muscle innervation

adductors

Femoral nerve muscle innervation

quadriceps

Gluteal nerve muscle innervation

gluteus maximus

Sciatic nerve muscle innervation

hamstrings

Tibial nerve muscle innervation

gastrocnemius (1) and tibialis posterior (2)

Common fibular nerve muscle innervation

tibialis anterior

Plantar reflex characteristics

polysynaptic, ipsilateral

Calcaneal (achilles) reflex characteristics

monosynaptic, ipsilateral

Plantar (babinski) reflex characteristics

polysynaptic, ipsilateral

Withdrawal (flexor) reflex characteristics

polysynaptic, ipsilateral

Crossed extensor reflex characteristics

polysynaptic, contralateral