Chapter 6 Flashcards
Nervous System characteristics
-Fast acting
-Electrical impulses
(As opposed to endocrine system)
-Derived from Neural (plate) Ectoderm, or Neural Crest Ectoderm
Two types of Nervous Syste,
CNS, PNS
CNS
Central Nervous System (CNS) = brain and spinal cord (dorsal hollow nerve cord)
neural plate ectoderm
PNS
Peripheral Nervous System = all nerves that exit or enter the CNS (always paired, right and left)
neural crest ectoderm
crainal nerves,
Functional Division
Somatic vs. Visceral
somatic afferent
carry sensory impulses to the CNS from skeletal muscle, from skeletal muscle to the brain
somatic efferent (ex)
motor output from CNS to Skeletal Muscles (Voluntary) push them away from you
visceral afferent
carry sensory impulses to the CNS from blood vessels or internal organs, from organs to the brain
visceral efferent
involves a preganglionic and postganglionic neuron and travels to smooth muscle, cardiac muscle and glands, autonomic motor output to internal organs and glands
somatic (concious) nervous system
Sensory (afferent) nerves receive input from:
- Body wall (skin, musculature)
- Appendages
- Motor nerves (efferent) send messages to musculature of body wall (somatopleure-made of ecto and meso)
visceral (unconcious) nervous system
Visceral Sensory:
Receive signals from organs of splanchnopleure(from meso-endo) also a bit of an ectoderm from this nervous system (hunger, discomfort, full bladder, some taste, some smell) unconcious signal to brain to you
Visceral Motor - automatic nervous system (8 lecture)
organization of the nervous system
Somatic nervous system also splits into two
- Somatic afferent
- Somatic efferent
Basic facts about Neurons
- They have ability to respond to stimuli. (change in cell membrane, they can take that change and create a signal)
- They have ability to CONDUCT AN ELECTRICAL SIGNAL.
SIGNAL PATHWAYS
Something causes change in property of neuron cell membrane.
This causes an electrical signal to enter cell, usually via dendrite(s). on or near cell body.
Travel along cell.
Usually leave via axon. SIGNAL DEGRADATION(lost of strength) IS REPRESSED DUE TO INSULATION BY MYELIN.
INSULATION OF NEURONS
To prevent electrical charge and current from “leaking out”, axons are insulated by a special type of material called MYELIN. electerial and physical border
-preventing electerical charge for leaking out
SCHWANN CELLS.
In PNS, myelin is produced by neuroGLIAL cells called
only happens in specific sports
OLIGODENDROCYTES.
In CNS, myelin is produced by neuroGLIAL cells called
only happens in specific spots
can cover
neurofibral NODES
Layers of myelin are wrapped around most of axon. Unlike that of an electrical cord, the covering is not continuous. These brief interruptions are called neurofibral nodes
at node, you can access the axolemma, ions can move
GANGLION (plural = ganglia)
(Frequently) cell bodies are concentrated in a spot along a nerve, forming a swelling called a
NUCLEUS
In the CNS, a collection of cell bodies is called a
What is said to be POLARIZED
The plasma membrane (cell membrane)
Nervous System divides
into CNS PNS
CNS
brain/spinal cord
PNS
somatic, visceral
Somatic/Visceral
somatic: somatic afferent/somatic efferent
visceral: visceral afferent/ visceral efferent or ANS autonomic nervous system
ANS (visceral efferent)
parasympathic/sympathetic
basic anatomy of a neuron
- cell body-nucleus
- off of cell body, processes, dendrites where you recieve a stimulus
- long process, axon, covered with cell membrane: axolemma
- axon divides into telodendria
- axon communicates and synapses
different neural morphologies
sensory: pseudounipolar(unipolar)
cell body is off set of the axon
stimilus dendrites, pass cell body, to terminals
multi:cell body located at one end of the axon, singal generates down
important concept of a neuron
communicates on or near the cell body, for motor neurons
what is the different between Schwann cells in the PNS and OLIGODENDROCYTES in the CNS is?
one Schwann cell will only cover one portion of a single axon
oligodendenrocytes, several processes that can cover multiple segments of multiple axons
but still perform same function
When you have many axons (neurons ) gathered together in the PNS is called?
Nerve
when you have many axons (neurons)gathered together in the CNS is called?
Tract
Swelling in a nerve, a collection of cell bodies in the PNS is called a
ganglia, ganglion
swelling, a collection of cell bodies in the CNS is called a
nucleus
PHYSIOLOGY OF NEURONAL IMPULSES
Neurons “maintain a resting electrical charge” to them, charge is centered around the cell membrane -resting membrane potential when cell isn’t doing anything
The plasma membrane (cell membrane) is said to be?
Polarized, because one side is a different charge than the other
what is the charge of a neuron of it’s resting potential?
negative 70 millivolts (-70 mv)
why is the resting potential of a neuron at -70 mv?
the difference in charge between the outside of the cell and the inside of the cell.
the outside is 70 mv more positive than the outside or the inside of the cell is 70 mv more negative than the outside
the charge difference is due too?
charge difference is due to the differential distribution of charged ions on either side of the membrane ,
what are the primary ions involved in the -70 mv resting electrical charge are?
potassium (K+) and sodium (Na+)
-both positive
is energy required to keep the neuron’s charge difference the same?
yes
how do you maintian the -70 mv electrical different
through active transport, Sodium ions are actively pumped out of the cell
how does the charge difference across the membrane works? ____-___pump?
the more sodium outside, more postivie outside the cell, outside is more positive becomes -70 mv more than the cell
sodium out, potassium in
sodium potassium pump
what is the job of the sodium potassium pump?
pump functions CONTINUOUSLY to maintain the charged membrane , powered by ATP
- two potassium pumped in
- three sodium pumped out makes the different -70
purpose of leak channels
achieve equilibrium
relief channel, pumping sodium out, sodium leak channels allow back into the cell, pumping some postive out, can come back in and can come back to -70, potassium leak channel, can leak out
electrochemical gradient for potassium
-90mV potassium naturally wants to leave the cell
electrochemical gradient for sodium
+66mV sodium naturally wants to go into the cell, completely reverses the membrane potential
where is sodium concentration higher? inside or outside
outside, higher sodium concentration
what direction does the electro chemical gradient of sodium flow?
inside the cell
-sodium is postive, electrical gradient inside the cell and concentration getting sodium inside VERY strong gradient
both of them causing sodium to go inside the cell
in order to trasmit an electorical signal you have to?
have a change in that membrane potential
-generate impulse
what triggers an impulse?
A CHANGE IN THE ELECTRICAL POTENTIAL (the –70 mV charge) across the cell membrane
This CHANGE IN THE ELECTRICAL POTENTIAL is usually cased by a change in
the PERMEABILITY OF THE CELL MEMBRANE to those particular ions, allows ions to flow more easily, makes the charge difference across the membrane
What does a stimulus do?
it causes the change of the plasma membrane
a stimulus could be?
a signal from a neighboring neuron
or a receptor cell that changes it’s shape that will change the permeability of a membrane
what does the perm. change allow?
ions to move across membrane.
chemically gated channels
AcH binds, and channel open, binds of receptor site, memebrane is more permerable to those ions
voltage gated channel
-70 gate is closed, -60 the channel is opened,proper voltage, ions can flow through, you can not only open one of the gates, +30 channel inactivated, changes permertability of ions
electronic lock
mechnically gated channel
for hearing, mechinically change, or pressure when something lands on you, is a mechnical even that causes this channel to open,
If a stimulus is strong enough (or if enough stimuli combine) to trigger an impulse, it is referred to as a
threshold stimulus
you can have a ______ than can change the membrane potential but it might not generate an _______ ______
stimulus
electrical signal
what happens when theshold stimulus is reached?
permeability of the membrane changes enough to allow Na+ ions to flood in , this thres. stimulus is an electrical value,
** for voltage gated, open up voltage gated for sodium-> sodium goes into cell
graded potential (look at lecture 6 slide 27)
Tiny stimulus-not much sodium entering, membrane potential wont get much higher
Strong stimulus, lot of channels, more sodium to enter, membrane potential, go away from -70 become more postive
goes from -60, -65, eventually to 70
Stimulus, changes permability
Permeability Change allows ions to move across the membrane when
-the inside is more negative
-if there is more positive Na+ outside, they will tend to flood in
-this makes the distribution of ions relative to the cell membrane
-
what is depolarization?
Changing the “polarized” condition of the membrane
what is an action potential?
when depolarization initiates along an axon
how does an action potential work?
once a small region of an axon is depolarized, it can stimulate an adjacent area,
stimulates the next area, so on and so on
action potention
sodium, high to low
describe loca
saltory propagation
decreases the difference, starts at -70, causing it to enter and travel, reaches thereshold, that second node can depolrize, sodium comes in, another local current and exact same thing happens
- movement of sodium, flooding it in and creating current, signal jump nodes to nodes
important functions of myelin
Insulates axon so that it is easier to maintain differential resting potential.
- Speeds up conduction of action potentials.
- Prevents “cross-talk” between different neurons grouped in a single nerve. (remember sensory and motor signals are traveling in different directions).
the nervous system is an
ELECTRICAL SYSTEM
chemicals to communicate between cells?
NEUROTRANSMITTERS.
important neurotransmitters
acetylcholine (ACh
describe neurotransmitter release
when you reach telodenria, calcium ions instead of sodium, waiting at telondria-where neurotransmitters,
what does depolrization happen in a neurotransmitter release?
will release neurotransmitters,
When depolarization of an action potential gets to end of a neuron, it still allows the influx of positively charged ions.
But in this case, the positively charged ion is CALCIUM—Ca2+
what is a synaptic cleft
They are released into the space between neurons,
YNAPTIC CLEFT is very small, so diffusion is nearly instantaneous (less than a millisecond).
They bind with receptors on the next neuron
what does calcium cause in neurotransmitter relrease and what is contained?
Ca2+ causes storage vesicles at end of axon to fuse with plasma membrane.
The vesicles contain neurotransmitters.
what happens after the neurotransmitter release?
what does it change?
what does it cause?
they bind with receptors for chemical gated channels on the next neuron-on the next postsynaptic cell, they change the configuration of the cell membrane of the postsynaptic cell/This causes a temporary, localized change in the permeability of the postsynaptic cell, this is the stimulus for the postsynaptic cell
result of cleft being small
Neurotransmitters are broken down and recycled VERY quickly (MILLISECONDS).
cleft clears out, singal can stop, neurotransmitter no longer in that cleft
neurotransmitter can work?
directly or indirectly
describe direct neurtransmitter
changing ion concentrations across the ions, affects membrane potentinal
describe indirect neurotransmitters
changing the metabolism of the cell, this is very quick, does not last beyond what you do at that one time, changing actual metabolism cell, longer lasting affect/you can affect ion channels through this, usually actually changing the number of channel you have,
direct
involve a receptor that is part of a chemically gated channel, open up ion channel, going to change the ion concentrations, ions out or not, iontropic once its released, effect stops as soon as it is released, quick, stops after that one neurotransmitter
direct effect neurotransmitters
ACh, glycine, aspartate, glutamate, GABA.
binding ACH, some ions can enter, changiong ions directky
indirict
second messeger system-longer term affect in the cell, neurotransmitter bind, form pathways, change metabolism of the cell, cellular process that are occuring, production of channels in plasma membrane, slower
indirect effect neurotransmitters (also direct)
, nitric oxide, carbon monoxide, glutamate, GABA.
effect of neurotransmitter deprends on the receptor but not the neurotransmitter
DEPENDENT ON RECEPTOR
if it binds inderct, indirect
direct, direct
excitation in a postsynaptic response,
Influx of Ca2+; decreased passage of Cl- (wants to enterthe cell, preventing cell from getting more negative) K+(inside of the cell will stay more positive; metabolic changes; change in number of receptors. Reach thereshold easier membrane becomes a little more positive, becomes easier to reach thereshold
-easier to depolirize
inhibitory cell
makes membrane potential more negative, more difficult to reach thereshold
-how relative refactory works
Influx of Cl-; increased passage of K+; metabolic changes; change in number of receptors
describe excitation and inhibition:
Can be excitatory reach thereshold or inhibitory(remove number of doors). Adds greater control and subtlety to nervous function.
or opposite
BUT, if there is insulation in the way, how can ions move due to depolarization?
Remember, the NODES. There are intermittent spots without insulation
how do nodes help in speed?
Sodium channels are concentrated near the NODES, and the depolarization literally skips from node to node, increasing speed of transmission significantly.
simply, what is the refracotry phase?
During this period, that particular region of the axon can’t respond to stimuli.
This is due to the inactivation of the voltage-gated sodium channels.
Shortly after a region is depolarized what does the cell want to do?=
the sodium pump works very hard to re-establish the resting potential.
refactory phase: look at picture slide 34 lecture 6 what are the important implications?
A spot just stimulated can’t be immediately restimulated, so only the next spot can be. In otherwords, a signal can’t double back on itself.
2. Axonal Transmission is thus UNIDIRECTIONAL (look this up)
