unit 6 Flashcards
topics
nerves
nerve impulses
division of the nervous system?
synapses
Organization of the nervous system
Central nervous system (CNS)
Brain and spinal cord
Peripheral nervous system(PNS)
all nerves
autonomic nervous system(ANS)
types of neurons function
sensory (afferent) neurons = conduct impulses to the spinal cord and brain
motor(efferent) neurons = conduct impulses away from brain and spinal cord to muscle and glands
interneurons = conduct impulse from sensory neurons to motor neurons or among a network of interneurons
also know as central or connecting neurons
cells of the nervous system
NEURONS
neuron structure: consist of 3 parts
cell body: neuron
dendrites: branching projections that conduct impulses to cell body of neuron
axon: elongated projection that conducts impulses away from cell of body neuron
cell of the nervous system
glia (neuroglia) = support cells, bringin the cell of nervous tissue together and structurally and functionally
3 types of glial cells CNS
astrocytes = star shaped cells that anchor small blood vessels to neuron
microglia = small cells that move in inflamed brain tissue carrying on phagocytosis
oligodendrocytes = form myelin sheaths on axon in the cns
schwann cells = form myelin sheaths on axons of the Pns
nerves and tracts
nerve: bundle of peripheral axons
tract = bundle of central axons
white matter = tissue composed primarily of myelinated axons (nerves or tract)
gray matter = tissue composed primarily of cell bodies and unmyelinated fibers
Nerve covering = fibrous connective tissue
endoneurium = surrounds individual fibers within a nerve
perineurium = surrounds a group (fascicle) of nerve fibers
epineurium = surrounds the entire nerve
nerve signals
the synapse = the place where impulses are transmitted from one neuron to another (postsynaptic neuron)
3 structures
synaptic knob
synaptic cleft
plasma membrane
neurotransmitter
bind to specific receptor molecule in the membrane of a postsynaptic neuron, opening ion channels and thereby stimulating impulse conduction by the membrane
reflex arcs
nerve impulses are conducted from receptors
= to effectors over neuron pathway or reflex arcs; conduction by a reflex arcs result in reflex
=The simplest reflex arcs are two-neuron arcs, consisting of sensory neurons synapsing in the spinal cord with motor neurons
=Three-neuron arcs consist of sensory neurons synapsing in the spinal cord with interneurons that synapse with motor neurons
nerve impulse
definition of a nerve impulse
=Self-propagating wave of electrical disturbance that travels along the surface of a neuron membrane (also called action potential)
=Mechanism of a nerve impulse
=At rest, the neuron’s membrane is slightly positive on the outside—polarized—from a slight excess of sodium ions (Na+) on the outside
=A stimulus triggers the opening of Na+ channels in the plasma membrane of the neuron
mechanism of a nerve impulse
=Inward movement of Na+ depolarizes the membrane by making the inside more positive than the outside at the stimulated point; this depolarization is a nerve impulse (action potential)
=The stimulated section of membrane immediately repolarizes, but by that time, the depolarization has already triggered the next section of membrane to depolarize, thus propagating a wave of electrical disturbances (depolarizations) all the way down the membrane
nerve signals
neurotransmitter = chemicals by which neurons communicate
Acetylcholine (ACh)
Catecholamines: Norepinephrine, dopamine, and serotonin
Endorphins
Enkephalins
Nitric oxide (NO)
Other compounds