Redo Ch 13

afferent

moving toward (the central nervous system)

anterior corticospinal tract

division of the corticospinal pathway that travels through the ventral (anterior) column of the spinal cord and controls axial musculature through the medial motor neurons in the ventral (anterior) horn

anterior (ventral) horn

gray matter of the spinal cord containing multipolar lower motor neurons

arachnoid mater

middle layer of the meninges named for the spider-web–like trabeculae that extend between it and the pia mater

autonomic reflex

reflex carried by autonomic nerves with effectors consisting of smooth muscle

axillary nerve

systemic nerve of the arm that arises from the brachial plexus

Babinski sign

abduction and dorsiflexion of the toes in response to testing of the plantar reflex

brachial plexus

nerve plexus associated with the lower cervical spinal nerves and first thoracic spinal nerve

brachial plexus avulsion

trauma that results in partial or complete tearing of part of the brachial plexus

Brown-Sequard hemisection

injury in which one half (left or right) of the spinal cord is severed

bulbous (Ruffini) corpuscles

encapsulated nerve endings that detect skin stretch

capsaicin

molecule that activates nociceptors by interacting with a temperature-sensitive ion channel and is the basis for “hot” sensations in spicy food

cauda equina

bundle of spinal nerve roots that descend from the lower spinal cord below the first lumbar vertebra and lie within the vertebral cavity; has the appearance of a horse’s tail

central nervous system (CNS)

anatomical division of the nervous system located within the cranial and vertebral cavities

cerebrospinal fluid (CSF)

circulatory medium within the CNS that is produced by ependymal cells in the choroid plexus filtering the blood

cervical enlargement

region of the ventral (anterior) horn of the spinal cord that has a larger population of motor neurons for the greater number of and finer control of muscles of the upper limb

cervical plexus

nerve plexus associated with the upper cervical spinal nerves

chemoreceptor

sensory receptor cell that is sensitive to chemical stimuli

communicating rami

the autonomic branches of a spinal nerve consisting of either preganglionic or postganglionic sympathetic neurons

contralateral

word meaning “on the opposite side”

contralateral reflex

reflex in which receptor and effector are on opposite sides of the body

conus medullaris

the end of the spinal cord that tapers into a point

corticobulbar tract

connection between the cortex and the brain stem responsible for generating movement

corticospinal tract

connection between the cortex and the spinal cord responsible for generating movement

cranial nerve

one of twelve nerves connected to the brain that are responsible for sensory or motor functions of the head and neck

cranial reflex

reflex carried by cranial nerves with an integration center within the brain

crossed extensor reflex

reflex that causes limb extension and occurs simultaneous and contralateral to the withdrawal reflex

cutaneous reflex

reflex elicited by stimulating receptors located in the skin

decussate

to cross the midline

deep tendon reflexes

clinical procedure used to test the stretch reflex in various muscles by tapping on the muscle tendon to stretch the muscle

denticulate ligaments

lateral extensions of the pia mater that stabilize the spinal cord in the vertebral canal

direct pathways

the corticospinal and corticobulbar tracts that give conscious control over movement consisting of upper motor neuron originating in the primary motor cortex and lower motor neuron located in the ventral horn or brainstem

dorsal column

white matter tracts carrying touch and proprioception sensory information and located between the dorsal horns of the spinal cord

dorsal column-medial lemniscus tract

ascending tract of the spinal cord associated with fine touch and proprioceptive sensations

dorsal ramus

the dorsal branch of a spinal nerve consisting of both sensory and motor neurons

dorsal (posterior) root

axons entering the posterior horn of the spinal cord

dorsal (posterior) root ganglion

sensory ganglion attached to the posterior nerve root of a spinal nerve

dura mater

tough protective outer layer of the meninges that also extends to cover spinal nerves

effector

the structure (skeletal muscle

efferent

moving away from (the central nervous system)

encapsulated ending

configuration of a sensory receptor neuron with dendrites surrounded by specialized structures to aid in transduction of a particular type of sensation

endoneurium

innermost layer of connective tissue that surrounds individual axons within a nerve

epidural space

space above the dura mater of the meninges

epineurium

outermost layer of connective tissue that surrounds an entire nerve

exteroceptor

sensory receptor that is positioned to interpret stimuli from the external environment

fascicle

small bundles of nerve or muscle fibers enclosed by connective tissue

fasciculus cuneatus

lateral division of the dorsal column system composed of fibers from sensory neurons in the upper body

fasciculus gracilis

medial division of the dorsal column system composed of fibers from sensory neurons in the lower body

femoral nerve

systemic nerve of the anterior leg that arises from the lumbar plexus

filum terminale

thin extension of the pia mater from the caudal end of the spinal cord that helps to stabilize the spinal cord in the vertebral canal

flaccid paralysis

paralysis resulting from lower motor neuron damage in which muscles are completely relaxed

free nerve ending

configuration of a sensory receptor neuron with dendrites in the connective tissue of the organ

general sense

any sensory system that is distributed throughout the body and incorporated into organs of multiple other systems

gray matter

regions of the nervous system containing cell bodies of neurons with few or no myelinated axons; actually may be more pink or tan in color

hair root plexus

nerve endings that are wrapped around hair follicles to detect hair movement

hemiplegia

paralysis of one side of the body

hyperreflexia

exaggeration of reflexes often due to upper motor neuron damage

hyporeflexia

decreased reflexes often due to lower motor neuron damage

indirect pathways

several complex circuits that innervate lower motor neurons and are involved in subconscious control over movement

integration (reflex) center

gray matter of the spinal cord or brain that integrates incoming sensory and other information in the control of a reflex

interoceptor

sensory receptor that is positioned to interpret stimuli from internal organs

ipsilateral

word meaning on the same side

ipsilateral reflex

reflex in which receptor and effector are on the same side of the body

kinesthesia

sense of body movement based on sensations in skeletal muscles

lamellated (Pacinian) corpuscles

encapsulated nerve endings located in the deep dermis or subcutaneous layer that detect deep pressure or vibration

lateral column

white matter of the spinal cord between the posterior horn on one side and the axons from the anterior horn on the same side; composed of many different groups of axons

lateral corticospinal tract

division of the corticospinal pathway that travels through the lateral column of the spinal cord and controls appendicular musculature through the lateral motor neurons in the ventral (anterior) horn

lateral horn

region of the spinal cord gray matter in the thoracic and upper lumbar regions that is the central component of the sympathetic division of the autonomic nervous system

lower motor neuron

second neuron in the motor command pathway that is directly connected to the skeletal muscle

lumbar enlargement

region of the ventral (anterior) horn of the spinal cord that has a larger population of motor neurons for the greater number of muscles of the lower limb

lumbar plexus

nerve plexus associated with the lumbar spinal nerves

lumbar puncture

procedure used to withdraw CSF from the lower lumbar region of the vertebral column that avoids the risk of damaging CNS tissue because the spinal cord ends at the upper lumbar vertebrae

mechanoreceptor

receptor cell that transduces mechanical stimuli into an electrochemical signal

medial lemniscus

fiber tract of the dorsal column system that extends from the nuclei gracilis and cuneatus to the thalamus

median nerve

systemic nerve of the arm

meninges

protective outer coverings of the CNS composed of connective tissue

monosynaptic reflex

rapid reflex arc where the incoming sensory neuron synapses directly on the lower motor neuron minimizing synaptic delay

muscle spindle

specialized intrafusal muscle fiber that detects stretch of a muscle

nerve plexus

network of nerves without neuronal cell bodies included formed from the ventral rami of spinal nerves

nociception

the detection of painful stimuli

nociceptor

receptor cell that senses pain stimuli

nucleus cuneatus

medullary nucleus at which first-order neurons of the dorsal column system synapse specifically from the upper body and arms

nucleus gracilis

medullary nucleus at which first-order neurons of the dorsal column system synapse specifically from the lower body and legs

obturator nerve

peripheral nerve that carries sensory information from the medial thigh and motor innervation of most adductor muscles

osmoreceptor

receptor cell that senses differences in the concentrations of bodily fluids on the basis of osmotic pressure

paraplegia

paralysis of the lower extremities

paresis

partial paralysis or weakness of a limb

patellar reflex

stretch reflex of the quadriceps muscle elicited by tapping the patellar ligament

perception

becoming aware of a stimulus

perineurium

layer of connective tissue surrounding fascicles within a nerve

peripheral nerve

nerve in the periphery distal to a nerve plexus or spinal nerve

peripheral neuropathy

damage to a peripheral nerve

peripheral nervous system (PNS)

anatomical division of the nervous system that is largely outside the cranial and vertebral cavities

phantom limb pain

erroneous perception of pain as originating from an amputated limb

phantom limb sensation

erroneous perception of stimuli as originating from an amputated limb

phasic sensory receptor

sensory receptors that adapt rapidly and more completely

photoreceptor

receptor cell specialized to respond to light stimuli

phrenic nerve

systemic nerve from the cervical plexus that innervates the diaphragm

pia mater

thin delicate inner layer of the meninges directly covering the spinal cord

plantar reflex

cutaneous reflex elicited by scraping the plantar surface of the foot from heel to toe