Nervous System Flashcards
non-excitable cells that provide structural support or that serve important functions in the nervous system
support cells
glial cells
aka support cells
atom with a positive or negative charge
ion
brain and spinal cord
central nervous system
nervous system that lies outside the brain and spinal cord
peripheral nervous system
excitable and can communicate with muscle and glands, receive and integrate signals at 1 location and transmit action potential at another, basic functional unit of the nervous system
neurons
cell that receives signal from a neuron or hormone, can be another neuron, muscle or gland
target cell
cell body, receptive portion, transmitting portion
3 neuron characteristics
located centrally, main nutritional and metabolic region, receives signal and sends toward axon
cell body/soma/perikaryon
extend from soma, branching processes, receive signal (afferent), may serve as sensory receptors
dendrites
thin and extend from soma, generates action potential/nerve impulse and conducts (efferent) it to the next cell, varies in length
axons
long distance regenerative electrical signal transmitted along an axon
action potential
junctions between a neuron and its target cell
synapses
each neuron has a signal which arises from the cell body, 1st portion of the axon
axon hillock
a branch of an axon
axon terminal
insulation surrounding axons, formed by support cells that wrap repeatedly around an axon forming a thick layer of cell membrane
myelin sheath
1 type of support cell in the nervous system, found in PNS, form myelin sheath around axons
schwann cells
tiny areas of bare axons between neighboring segments of myelin sheath, in a myelinated axon, charge forms across the membrane only at the nodes so the action potential appears to jump along the axon
nodes of ranvier
selective, passive or active, regionally located, control movement of ions across the neuronal membrane, these tiny structures make neurons excitable
ion channels
proteins that are embedded in the lipid bilayer of the cell membrane
integral proteins
depends on charge of ion, how much water the ion attracts and holds around it
channel selectivity
ion channels that can be opened or closed by gates
active channels
always open, resting membrane potential, located in the cell membrane, cell body, and axon
passive channels
gates are opened or closed by changes in the membrane voltage, located on axon hillock, myelinated and unmyelinated sheaths, and nodes of ranvier, action potential
voltage gated channels
the electrical potential or voltage across a cell membrane that results from the separation of charged particles across the membrane
membrane potential
a chemical released at a synapse, GABA or ACH
neurotransmiter
gates that open or close when a neurotransmitter binds to them, located in dendrites, and cell body, responsible for synaptic response
chemically gated channels
a short distance electrical signal that can vary in amplitude
synaptic potential
sensory functions, integrating functions, motor functions
3 main activities
conduct impulses toward CNS, also called sensory nerves, located in the dorsal horns
afferent nerve fibers
conduct impulses away from CNS, also called motor nerves, located in ventral horns
efferent nerve fibers
nerves may contain both kinds of nerve fibers
PNS mixed nerves
coordination of automatic body functions (ie stimulation of digestive juices in response to ingestion of a meal)
autonomic nervous system
conscious or voluntary control of skeletal muscles
somatic nervous system
specialized molecule to help maintain cell resting state
Na pumped out
K pumped in
Na K pump
difference in electrical charge across a neuron’s membrane, a net negative charge
resting membrane potential
neuron is not being stimulated, Na has been pumped out of cell, K has been pumped in, net negative charge inside the cell
resting state
neuron receives external stimulus, Na channel opens on neuron cell membrane, Na neurons flow into cell by passive diffusion, charge now positive inside cell
depolarization
switching of electrical charge from negative to a positive
action potential
Na channels are closing, K channels are opening, K ions flow out of cell, net charge is returning to negative
beginning of repolarization
sufficient outflow of K ions restored to net negative charge inside the cell
Na and K ions are on opposite sides of cell membrane from where they started
ion distribution is reversed
repolarization
electric charges flip across cell membrane (depolarization) following by unflipping of the electric charges (repolarization)
an area is depolarized, an adjacent area is stimulated, spreading a wave of depolarization
nerve impulse
stimulus is strong enough to cause complete depolarization and to generate a nerve impulse
threshold stimulus
very brief time period when a neuron is insensitive to additional stimuli
refractory period
during Na influx and early K outflow
absolute refractory period
during end of repolarization period, possible to stimulate another depolarization if stimulus is very large
relative refractory period
gap between 2 adjacent neurons or between a neuron and a target cell
synaptic cleft
brings depolarization to the synapse and releases neurotransmitter
presynaptic neuron
contains receptors for the neurotransmitter released by the presynaptic neuron
postsynaptic neuron
perpetuation of the nerve impulse from one neuron to the next cell
depolarization wave triggers Ca influx into synaptic knob membrane
Ca causes vesicles to dump neurotransmitter into synaptic cleft
synaptic transmission
usually cause influx of Na so postsynaptic membrane moves toward threshold, beginning a new impulse
excitatory neurotransmitters
make inside of cell more negative, moving the charge within the postsynaptic cell father away from the threshold
inhibitory neurotransmitters
excitatory at somatic motor neurons, inhibitory is PSNS stimulation of the heart, primary neurotransmitter for parasympathetic nervous system
acetycholine
norepinephrine, epinephrine, dopamine neurotransmitters
catecholamines
brain, inhibitory neurotransmitter
GABA
spinal cord, inhibitory neurotransmitter
glycine
somatic nervous system fight or flight
primary neurotransmitter for sympathetic nervous system
norepinephrine
adrenal release, somatic nervous system fight or flight
epinephrine
autonomic fine muscle function
dopamine
the action stimulated depends on the type of neurotransmitter released (excitatory or inhibitory)
CNS post synaptic receptors
contains most of the neuron cell bodies
gray matter
contains most of the myelinated nerve fibers
white matter
functions associated with learning and intelligence
receives and interprets sensory information
regulates conscious behavior
cerebrum
responsible for coordinated movement, balance, posture and complex reflexes
cerebellum
role in temperature regulation, hunger, thirst and rage/anger responses
diencephalon
autonomic, cranial nerves originate here, responsible for maintenance of basic support functions of the body
brain stem
connective tissue layers that surround the brain and spinal cord, supply nutrients and oxygen and provide cushioning
meninges (DAP)
fluid between layers of meninges and in canals and cavities inside brain and spinal cord
cerebrospinal fluid
separates capillaries in the brain from nervous tissue
blood brain barrier
12 pairs of nerves in PNS that originate directly from the brain, each may contain motor, sensory and mixed neurons
cranial nerves
conducts sensory information and motor instructions between brain and rest of the body
spinal cord
sensory or afferent nerve fibers
dorsal nerve roots
motor or efferent nerve fibers
ventral nerve roots
cluster of neuroal bodies outside the CNS
ganglio
neurons in the cell body in the brain or spinal cord
preganglionic neuron
neurons connected to a target organ
postganglionic neuron
part of the autonomic nervous system, fight or flight response, helps the body cope in emergency situations
sympathetic nervous system
part of the autonomic nervous system, rest and restore, brings the body back to resting state, facilitates all body processes to replace resources used during the emergency
parasympathetic nervous system
neurons that release norepinephrine
adrenergic neurons
alpha, beta 1 and beta 2, all stimulated norepinephrine
3 types of receptors affected by sympathetic nervous system
vasoconstriction of skin, GI tract, kidney
alpha
increases heart rate and force of contraction
beta 1
bronchodilation
beta 2
nicotinic and muscarinic receptors
2 types acetylcholine receptors
found on postganglionic neurons of both sympathetic and parasympathetic systems
nicotinic receptors
on tissues supplied by postganglionic neuron of parasympathetic nervous system
muscarinic receptors
rapid, automatic response to stimuli, designed to protect the body and maintain homeostasis
reflexes
somatic, autonomic, contralateral (opposite sides), ipsilateral (same sides)
4 types of reflexes
reflex arc
- sensory receptor detects a change
- then sends action potential along sensory neuron to gray matter of spinal cord or brain stem
- sensory neuron synapses with other neurons
- integrated response is sent out by motor neuron to target organ
types of reflexes
stretch withdrawal crossed extender palpebral pupillary light respons
involves a sensory neuron and a motor neuron, only 1 synapse and no interneurons
stretch reflex
several interneuron synapses in different segments on the same side of the spinal cord, results in contraction or flexing of muscles
withdrawal reflex
afferent sensory impulse synapses with interneurons crosses to other side of spinal cord and stimulates muscles that extend the opposite limb
crossed extender reflex
light tap on medial canthus of eye produces blind of eyelids, cranial nerve 5 and jaw tone
palpebral reflex
normal response to shining light in the eye of an animal is for iris in both eyes to constrict
pupillary light reflex (PLR)
what is another name for nerve fibers?
axons
as opposed to the nervous system, how does the endocrine system work?
it utilizes hormones to cause an effect in tissues
what part of the brain controls temperature regulation and thirst?
diencephalon
turning the head is an example of which nervous system?
somatic nervous system
in a repolarized neuron, where is the sodium and potassium the highest?
potassium is highest outside the cell and sodium is highest inside the cell
what is the name of the period when a neuron that normally generates a nerve impulse can not generate another?
refractory period
what part of the spinal cord carries afferent sensory fibers?
dorsal horn
what gland in the body produces a hormone that complements the action of the hormones produced by the sympathetic nervous system?
adrenal gland
what is the neurotransmitter for the parasympathetic nervous system?
acetylcholine
what are the two receptors of the parasympathetic nervous system?
nictorinic and muscarinic
what are the three receptors for the sympathetic nervous system and where are they found?
alpha - vasoconstriction of the gi tract
beta 1 - heart
beta 2 - bronchioldilation of the lungs
what neurotransmitter stimulates the gi tract?
acetylcholine
when the spinal cord is injured how will the nervous system caudal to the area of the the injury respond?
it will have an increased response so it will be hyper reflexive
what reflex results in both the ipsilateral and contralateral response
crossed extender reflex
what is the term used to convert a mechanical stimulus into an electrical stimulus that travels to the central nervous system?
transduction