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Peripheral Nervous System
Vocabulary covering Ch. 13
28
Physiology
Undergraduate 1
11/30/2008

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Term
medial lemniscus
Definition
An ascending axonal tract in the brainstem that carries tactile and proprioceptive information from the dorsal column nuclei to the thalamus.
Term
proprioception
Definition
Knowing where the parts of your body are.
Term
stimuli
Definition
Changes in the environment.
Term
general sensory receptors
Definition
Involved in tactile sensation provided by proprioceptors. Anatomically divided into unecapsulated (naked) or ecapsulated nerve endings.
Term
unencapsulated (naked) nerve endings
Definition
Present nearly everywhere in the body with abundance in epithelia and connective tissues. Most of the sensory fibers are unmyelinated and the distal endings have small, knob-like swellings. Examples: Merkel (tactile) discs & hair follicle receptors.
Term
Merkel (tactile) discs
Definition
Lie in the deeper layers of the epidermis and function as light touch receptors.
Term
encapsulated dendritic endings
Definition
Sensory neuron fiber terminals enclosed in a connective tissue capsule. Virtually all are mechanoreceptors that vary greatly in size, shape and distribution in the body. Example: Meissner's & Pacinian corpuscles.
Term
somatosensory system
Definition
Part of the sensory system serving the body wall and limbs.
Term
transduction
Definition
The conversion of energy from a stimulus into an electrical event.
Term
phasic receptors
Definition
FAST adapting receptors giving BURSTS of impulses at the beginning and end of the stimulus. Example: Pacinian & Meissner's corpuscles.
Term
tonic receptors
Definition
Receptors providing a SUSTAINED response with little or NO adaptation. Example: Nociceptors & most proprioceptors.
Term
ganglia
Definition
Collections of neuron cell bodies associated with nerves in the PNS.
Term
dorsal root ganglia
Definition
Ganglia associated with afferent nerves.
Term
tract
Definition
Group of nerve fibers running in a specific direction.
Term
spinal nerves (Total #, # of pairs in each vertebral region)
Definition
31 total pairs of mixed nerves. 8 pairs of cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal.
Term
ventral roots
Definition
Motor fibers that innervate skeletal muscles.
Term
dorsal roots
Definition
Sensory fibers that arise from sensory neurons in the dorsal root ganglia.
Term
nerve plexuses
Definition
Formed by only ventral rami which criss-cross each other so that each limb receives it's nerve supply from more then one spinal nerve. The ventral rami join one another lateral to the vertebral column to form nerve plexuses.
Term
sciatic nerve
Definition
The thickest and longest nerve in the body supplying the entire lower limb.
Term
dermatome
Definition
The are of skin innervated by the cutaneous branches of a single spinal nerve.
Term
innervation
Definition
Supply of nerves to a body part.
Term
cutaneous
Definition
Pertaining to the skin.
Term
motor endings
Definition
The PNS elements that activate effectors by releasing neurotransmitters.
Term
varicosities
Definition
A series of knob-like swellings containing mitochondria and synaptic vesicles at an axon ending serving smooth muscle or a gland.
Term
basal nuclei
Definition
Specific gray matter areas located deep within the white matter of the cerebral hemispheres. *see notes for functions*
Term
reflex arcs
Definition
Highly specific neural paths with five essential components: receptor, sensory neuron, integration center, motor neuron, effector.
Term
somatic reflexes
Definition
Involves skeletal muscle.
Term
visceral reflexes
Definition
Activates smooth/cardiac muscle or glands.
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