Chapter 13 - Spinal cord and Reflexes

Central Nervous System

brain and spinal cord, processing centers

Peripheral Nervous System

cranial nerves (12 pairs) and spinal nerves (31 pairs), sensory input and motor response pathways

reflexes

quick, autonomic nerve responses triggered by specific stimuli

spinal reflexes

controlled by spinal cord alone without input from brain

spinal cord

carry sensory and motor information between brain and most other parts of body

conus medullaris

tapred, conical end of cord below lumbar enlargement

cauda equina

nerve roots extending below conus medullaris

filum terminale

thin thread of fibrous tissue at end of conus medullaris

branches that form spinal nerves

Anterior root, posterior root

anterior root (ventral root)

motor neurons

posterior root (dorsal root)

sensory neurons

spinal ganglia ((dorsal root ganglia)

contain cell bodies of sensory neurons that form the posterior root

posterior ramus

supplies skin / muscles of back

anterior ramus

supplies most of body wall, skin, limbs

epidural space

between vertabrae and dura mater (above dura mater)

subdural space

space between dura mater and arachnoid mater (below dura mater)

subarachnoid space

space with arachnoid trabeculae between arachnoid mater and pia mater

carry CSF

gray matter horns

posterior horns, anterior horns, lateral horns

posterior horns

somatic and visceral sensory nuclei (incoming information from receptors)

anterior horns

somatic motor nuclei (outgoing information to effectors)

lateral horns

thoracic and lumbar segements; visceral motor nuclei

connective tissue layers of spinal nerves

epineurium, perineurium, endoneurium

dermatome

specific bilateral region of skin supplied by a single pair of spinal nerves

peripheral neuropathies

regional losses of neural function that affect dermatomes

nerve plexuses

complex interwoven network of nerve fibers

cervical plexus

anterior rami of spinal nerves C1-C5

innervate scalp behind ear, neck and diaphragm

phrenic nerve

major cervical plexus nerve from C3-C5 that controls diaphragm

brachial plexus

innervates pectoral girdle, upper back, upper limb

anterior rami of C5-T1

lumbar plexus

anterior rami of T12-L4

sacral plexus

anterior rami of L4-S4

neuronal pools

group of interconnected nerve cells that work together to perform a specific function

innate reflexes

basic neural reflexes formed before birth

acquired reflexes

rapid, automatic learned motor patterns

somatic reflexes

control skeletal muscle contractions

superficial reflexes, stretch or deep tendon reflexes, immediate reflexes

superficial reflexes

stimuli in skin / mucous membranes

stretch / deep tendon reflexes

'knee jerk reflex

immediate

important in emergencies

visceral reflexes

autonomic reflexes

control other effectors - smooth muscle, cardiac muscle, glands

tendon reflex

prevents skeletal muscles from developing too much tension and tearing or breaking tendons

withdrawal reflexes

move body part away from stimulus (pain or pressure)

reciprocal inhibition

stretch reflex of antagonistic (extensor) muscles must be inhibited by interneurons for flexor reflexes to work