Chapter 12 Nervous Tissue Flashcards
2 systems for maintaining internal communication
endocrine system & nervous system
Function of the endocrine system
releases hormones into the blood -
target cells respond
Function of the nervous system
immediate messages from cell to cell -
by way of electrical impulses and chemical transmitters
2 main parts of the nervous system
central nervous system & peripheral nervous system
CNS contains:
brain & spinal cord
PNS contains:
nerves & ganglia (outside CNS)
bundle of fibers (axons) wrapped in fibrous connective tissue
nerve
knot-like swelling in a nerve where cell bodies are concentrated
ganglion
PNS divisions:
sensory & motor
carries signals from various receptors
PNS sensory division
carries signals from the CNS mainly to gland and muscle
PNS motor division
carries signals from receptors in the skin, muscles, bones, and joints
somatic sensory (PNS)
carries signals from receptors in the viscera of the thoracic cavity & abdominopelvic cavity
visceral sensory (PNS)
carries signals to skeletal muscle
movements are voluntary
somatic motor (PNS)
carries signals to glands, heart, & smooth muscle
actions are involuntary
visceral motor (PNS)
ANS
autonomic nervous system
PNS
peripheral nervous system
visceral reflexes
responses of the ANS
ANS is divided into:
sympathetic & parasympathetic
example of response triggered by the sympathetic nervous system
increasing heart rate & respiratory airflow
example of responses triggered by the parasympathetic nervous system
reduced heart rate
actions tend to arouse the body for action
sympathetic ANS
tends to have calming effect
parasympathetic ANS
nerve cells are called:
neurons
properties of neurons
excitability, conductivity, & secretion
functional classes of neurons
sensory, interneurons, & motor
type of neuron that is specialized to detect stimuli; light, sound, heat, pressure, & chemicals
sensory neuron
when triggered, transmits impulses to the CNS
sensory neuron
type of neuron that is within the CNS, receives impulses from other neurons and integrates them, directs outgoing impulses to specific ares
interneurons
type of neuron that sends signals to efferent organs, away from the CNS
motor neuron
center of the neuron
Neurosoma
also: soma, cell body, perikaryon
neurons cannot divide or progress through the cell cycle because the lack:
centrioles
branches from the soma, site for receiving signals from other neurons, receive and transmit to the soma,
dendrites
begins at axon hilock, tubular, unbranched, axon collateral at distal end
axon
fine branches at the end of the axon
terminal arborization
cytoplasm equivalent in the axon
axoplasm
cell membrane equivalent of the axon
axolemma
multipolar neurons have:
multiple dendrites, one axon
most brain & spinal cord neurons are:
multipolar
bipolar neurons have:
one axon, one dendrite
neurons of the olfactory system and retina (light transmission) are:
bipolar
unipolar neurons have:
one process away from the soma (T shaped)
describe material transport in regard to the axon
materials must be transported to and away from the soma
movement toward (down) the axon terminal
anterograde transport
movement toward the soma
retrograde transport
nervous tissue cells that support neurons
neuroglia (glial cells)
cover entire surface of cell not involved in impulse propagation or synaptic transmission
glial cells
6 types of supportive nervous tissue cells
oligodendrocytes ependymal cells microglia astrocytes Schwann cells satellite cells
support cells only in the PNS
Schwann cells & satellite cells
projections of flat membrane sheet wrap around axons
oligodendrocytes
line internal cavities of the CNS, produce CSF
ependymal cells
small macrophages, aid in CNS immune function, indicate tissue injury
microglia
most abundant glial cell, covers brain surface, perivascular feet, contact blood vessels, converts glucose to lactate, regulates blood vessel diameter, regulates electrolyte concentrations
astrocytes
scar tissue formed by astrocytes
astrocytes (sclerosis)
wrap axons of peripheral nerves, create myelin sheaths in the PNS
Schwann cells
surround soma in ganglia, provide electrical insulation, regulate chemical environment of ganglionic neurons
satellite cells
spiral layer of insulation around a nerve fiber
myelin
production of myelin
myelination
centrifugal myelination
process in PNS
centripetal myelination
process in CNS
myelin sheath gaps
nodes of Ranvier
the axon segment continuous with the soma
trigger zone
2 factors that determine conduction speed
diameter & presence or absence of myelin
large fibers with ______ axolemma surface area conduct impulses _______
more - faster
small fibers with ______ axolemma surface area conduct impulses _______
less - slower
unmyelinated axons transmit impulses ________
faster or slower
faster
myelinated axons transmit impulses ________
faster or slower
slower
meaningful patterns of action potential
neural coding
receptors that recognized a specific stimulus all lead to neurons in a specific part of the brain
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