Lecture Exam 3 Review Ch 12 Flashcards
central nervous system
brain and spinal cord
peripheral nervous system
nerves and sensory receptors
nerve
a bundle of hundreds to thousands of axons plus associated connective tissue and blood vessels that lies outside the brain and spinal cord
cranial nerves
12 pairs; emerge from the brain
spinal nerves
31 pairs; emerge from the spinal cord
sensory receptor
a structure of the nervous system that monitors changes in the external or internal environment
sensory/afferent division of the PNS
conveys input into the CNS from sensory receptors in the body; provides the CNS with sensory information about the somatic senses (tactile, thermal, pain, and proprioceptive sensations) and special senses (smell, taste, vision, hearing, and equilibrium)
motor/efferent division of the PNS
conveys output from the CNS to effectors (muscles and glands); further divided into the somatic and autonomic nervous systems
somatic nervous system
conveys output from the CNS to skeletal muscles only; voluntary
autonomic nervous system
conveys output from the CNS to smooth muscle, cardiac muscle, and glands; involuntary; sympathetic and parasympathetic divisions
enteric plexus
branch of the ANS; extensive network of over 100 million neurons confined to the wall of the digestive canal; helps regulate the activity of the smooth muscle and glands of the digestive canal; can function independently but communicate with and are regulated by the other branches of the ANS
functions of the nervous system
sensory function, integrative function, motor function
sensory function
sensory receptors detect internal stimuli, such as an increase in blood pressure, or external stimuli, such as a raindrop landing on your arm; this sensory information is then carried into the brain and spinal cord through cranial and spinal nerves
integrative function
the nervous system processes sensory information by analyzing it and making decisions for appropriate responses- an activity known as integration
motor function
once sensory information is integrated, the nervous system may elicit an appropriate motor response by activating effectors through cranial and spinal nerves; stimulation of the effectors causes muscles to contract and glands to secrete
stimulus
any change in the environment that is strong enough to initiate a nerve impulse
nerve impulse/action potential
an electrical signals that propagates along the surface of the membrane of a neuron
neuronal cell body
perikaryon/soma; contains a nucleus surrounded by cytoplasm that includes typical cellular organelles and free ribosomes and prominent clusters of rough ER
Nissl bodies
prominent clusters of rough ER
neurofibrils
bundles of intermediate filaments that provide the cell shape and support
microtubules
assist in moving materials between the cell body and axon
lipofuscin
a pigment in aging neurons that occurs as clumps of yellowish-brown granules in the cytoplasm
somatic spines
small projections of the plasma membrane that are receptor sites that band chemical messengers from other neurons
ganglion
collection of neuron cell bodies outside the CNS
nerve fiber
general term for any neuronal process that emerges from the cell body of a neuron
dendrites
receiving or input portions of a neuron
dendritic spines
receptor sites for binding chemical messengers from other neurons
axon
propagates nerve impulses toward another neuron, a muscle fiber, or a gland cell
axon hillock
cone-shaped elevation of the cell body that joins the axon
initial segment/trigger zone
part of the axon closest to the axon hillock where the nerve impulses arise
axoplasm
cytoplasm of an axon
axolemma
plasma membrane of an axon
axon collaterals
side branches of axon
axon terminals
axon and its collaterals end by dividing into many fine processes
synapse
site of communication between two neurons or between a neuron and an effector cell
synaptic end bulbs
the tips of some axon terminals that swell into bulb shaped structures
varicosites
another string of swollen bumps that may be at the tips of axon terminals
synaptic vesicles
membrane-enclosed sacs that store neurotransmitters
neurotransmitter
a molecule released from a synaptic vesicle that excites or inhibits another neuron, muscle fiber, or gland cell
multipolar neurons
several dendrites and one axon
bipolar neurons
one main dendrite and one axon
unipolar
dendrites and one axon that are fused together to form a continuous process that emerges from the cell body
sensory neurons
either contain sensory receptors at their distal ends or are located just after sensory receptors that are separate cells; once an appropriate stimulus activates a sensory receptor, the sensory neuron forms a nerve impulse in its axon and the nerve impulse is conveyed into the CNS through cranial or spinal nerves
motor neurons
convey nerve impulses away from the CNS to effectors in the PNS through cranial or spinal nerves
interneurons
mainly located within the CNS between sensory and motor neurons; integrate incoming sensory information from sensory neurons and then elicit a motor response by activating the appropriate motor neurons
astrocytes
star shaped cells with many processes that form the blood-brain barrier and maintain the neuronal chemical environment
oligodendrocytes
form and maintain the myelin sheath in the CNS
myelin sheath
multilayered lipid and protein covering around some axons that insulates them and increases the speed of nerve impulse conduction
microglial cells
function as phagocytes
ependymal cells
cuboidal to columnar cells arranged in a single layer that possess microvilli and cilia; line the ventricles of the brain and central canal of the spinal cord and produce and circulate CSF
Schwann cells
form myelin sheath in the PNS
satellite cells
regulate the exchanges of materials between neuronal cell bodies and interstitial fluid
neurolemma
outer nucleated cytoplasmic layer of the Schwann cell that encloses the myelin sheath
myelin sheath gaps
node of Ranvier
nucleus
cluster of neuronal cell bodies located in the CNS
tract
bundle of axons that is located in the CNS
white matter
composed primarily of myelinated axons
gray matter
contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia
graded potentials
short distance communication only; a small deviation from the resting membrane potential that makes the membrane either more polarized (inside more negative) or less polarized (inside less negative)
action potentials
allow communication over long distances; a sequence of rapidly occurring events that decrease and reverse the membrane potential and then eventually restore it to the resting state
membrane potential
an electrical potential difference (voltage) across the membrane
resting membrane potential
membrane potential in excitable cells
leak channels
gates randomly alternate between open and closed positions
ligand-gated channels
open and close in response to the binding of a ligand/chemical stimulus
mechanically gated channels
open or close in response to mechanical stimulation in the form of vibration, touch, pressure, or tissue stretching
voltage-gated channels
open in response to a change in membrane potential
hyperpolarizing graded potential
response makes the membrane more polarized (inside more negative)
depolarizing graded potential
response makes the membrane less polarized (inside less negative)
threshold
