Chapter 12: Nervous System Flashcards
3 nervous system functions
sensory receptors monitor changes inside and outside the body; processes and interprets sensory input; dictates a response by activating effector organs
Central Nervous System (CNS)
brain and spinal cord; integration and command center
Peripheral Nervous System (PNS)
nerves extending from brain and spinal cord; link all regions of body to CNS
sensory
afferent signals picked up by sensory receptors; carried by nerve fibers of PNS to CNS
motor
efferent signals carried away from the CNS; innervate muscles and glands
somatic sensory
dectect touch, pain, pressure, hearing balance and proprioceptive senses (detect stretch in tendons and muscles)
visceral sensory
stretch, pain, hunger, taste, and smell
somatic motor
contraction of skeletal muscles; voluntary control
visceral motor
regulates contraction of smooth and cardiac muscle; involuntary control
neurons
excitable cell that transmits electrical signals
neuroglia
nonexcitable support cells; surround and wrap neurons
ganglia
clusters of cell bodies; lie along nerves in PNS
special charcteristics of neuron
longevity(live and function for a lifetime); do not divide; high metabolic rate(require abundant oxygen and glucose
dendrites
extensive branching from cell body; receptive sites
axons
one per neuron; impulse generators and conductors; transmit impulses away from cell body
neurotransmitters
excite or inhibit neurons; released from axon terminals
presynaptic neuron
conducts signal toward a synapse
postsynaptic neuron
transmits electrical activity away from a synapse
multipolar
possess more than 2 processes
bipolar
possess two processes
unipolar
pseudounipolar; possess one short, single process
astrocytes
most abundant glial cell type; extract blood sugar from capillaries; take up and release ions to control environment and neurons
microglia
smallest and least abundant glial cell; phagocytes(macrophages of the CNS); derive from blood cells called monocytes
ependymal cells
lines the central cavity of the spinal cord and brain
oligodendrocytes
have fewer branches; wrap their cell processes around axons in CNS
satellite cells
surround neuron cell bodies within ganglia
schwann cells
neurolemmocytes; surround axons in the PNS
oligodendrocytes
form the myelin sheaths in the brain and spinal cord (CNS)
nerves
cablelike organs in the PNS
endoneurium
layer of delicate loose connective tissues surrounding the axon
perineurium
connective tissue wrapping that surround nerve fascicles
nerve fascicles
groups of axons bound into bundles
epineurium
whole nerve is surrounded by tough fibrous sheath
neuron
nerve cell
nerve fiber
long axon
nerve
collection of axons in the PNS
gray matter
gray-colored zone that surrounds hollow central cavities of the CNS; forms butterfly-shaped region in spinal cord; where synapses occur; contains cluster of neuron cell bodies
white matter
external to gray matter; contains no neuron cell bodies; contains axons and neuroglia
tracts
bundles of axons traveling to similar destinations
reflex arcs
simple chains of neurons; determine structural plan of nervous system; responsible for reflexes
5 components of reflex arc
receptor, sensory neuron, integration center, motor neuron, and effector
monosynaptic reflex
simplest and fastest reflex; one synapse
polysynaptic reflex
more common type of reflex; one or more interneurons involved; ex: withdrawal reflexes
neuronal circuits
how interneurons of the CNS are interconnected in multiple ways
diverging circuit
one presynaptic neuron synapses with several neurons
ex: stretch reflex
converging circuit
many neurons synapse on a single postsynaptic neuron
reverberating circuit
one neuron in the circuit receives feedback from another neuron in the same circuit
