Organization of the ns, synaptic transmission Flashcards
what is part of the central nervous sys
encephalon (brain, brainstem, cerebellum), spinal cord
what is part of the peripheral nervous sys
peripheral n. (sensory and motor)
what is the function of the autonomic nervous sys
controls autonomic functions (HR, respiratory rate, digestion, urination, …)
what increases and what decreases the activity of autonomic functions
sympathetic increases
parasympathetic decreases
where does the ANS signals originate from
from the brainstem
what is called the process when a signal doesnt need to reach the brain to provoke a motor action
reflex
what are the 3 major levels of the cns
cortical, subcortical and spinal cord
what does the spinal cord contain (4)
-walking circuits (central pattern generators)
-circuit for reflexes that control mvt,
-circuits for body support agains gravity
-circuits for reflexes that control organ functions (e.g blood vessels, gastrointestinal, urination,…)
___ is more than just a conduit for signals from periphery of body to brain and vis-versa
spinal cord
what muscles are used for the stance and swing in walking
stance: extensors
swing: flexors
what is part of the subcortical level (lower brain) bbchmt
brainstem (medulla and pons), mesencephalon, hypothalamus, thalamus, cerebellum and basal ganglia
what level controls subconscious body activities
subcortical level
what kind of activities are controlled by the subconscious level (7) abefhrw
-arterial pressure,
-respiration,
-equilibrium,
-feeding reflexes,
-body temperature,
-wakefulness and sleep,
-hormone regulation
what is called the superficial layer of the grey matter that is where the most complicated and sophisticated functions of the ns
cortical level (higher brain)
t/f cortex always functions alone, it never needs lower centers
false, cortex never functions alone, always in association with lower centers
what are the functions of the cortical level (4) timd
-info processing
-memory storage
-decision making
-thought processes (jugement)
vagal shock is produced by stimulation of what ns
parasympathetic ns
cerebral cortex is made of what matter
grey
what transmission of what info is done by the somatosensory sys
transmission of somatic info from receptors to cns
the info from the somatosensory sys is transmitted to what (5) cctrs
-spinal cord,
-reticular substance (brainstem and mesencephalon)
-cerebellum
-thalamus
-cerebral cortex
more than ___ % of all ____ info is discarded by the brain as irrelevant or unimportant
99 sensory
what body activities does the motor sys control
-skeletal m. cnt,
-smooth m. cnt (internal organs)
-the activity of exocrine and endocrine glands
what is the basic functional unit of the central nervous sys
the neuron
what is the soma
main body of the neuron
signal processing
what are dendrites
projections of the soma
signal output
what is the axon
extends from soma to the terminal
signal output
what is a unipolar neuron
one process (dendrite and axon on the same side)
photoreceptors in retina (rods and cones)
what is a multipolar neuron
several dendrites and one axon
most common cell type (e.g motorneuron, purkinje cell)
what is a pseudo-unipolar neuron
one process (develops from bipolar)
sensory neuron in the sc
what is a bipolar neuron
one main dendrite and one axon
found in retina, inner ear and olfactory
how is info transmitted within the neuron
by action potentials (electrical signals)
the ap starts where and propagates where after
starts at the axon hillock and propagates along n. fiber until it comes to the fiber’s end
how is info communicated btw neurons
by synapses (chemical signal)
what is the role of Ca++
Ca++ enters cell and causes neurotransmitters to be released from vesicles
what is the amount of neurotransmitters released in direct relation to
the number of Ca++ ions that enter
what is a neurotransmitter
is a chemical substance synthesized in presynaptic terminal and released in the synapse by the arrival of the AP. By diffusing across the synapse, the NT causes the transfer of the AP to another n. or a m. fiber
what are the types of NT based on
based on the action on the postsynaptic neuron
what types of NT are excitatory (excites postsynaptic neuron)
glutamate, dopamine, norepinephrine, acetylcholine, serotonin
describe glutamate
used in every part of the brain and sc
describe dopamine mep
motor behavior + pleasures + emotional arousal
describe norepinephrine saf
sleep patterns + focus + alertness
describe acethylcholine
activates skeletal muscles
describe serotonin slamm
mood+appetite+sleep+memory+learning
what types of NT are inhibitory (inhibits postsynaptic neuron)
GABA
describe GABA
used in every part of the brain (balance in our sys), many sedative/tranquilizing drugs act by enhancing the effects of GABA
what are the 4 steps of the mechanism of neurotransmitter release in synaptic transmission
1- AP arrives at the presynaptic terminal
2- Local depolarization opens voltage-gated Ca2+ channels and Ca2+ ions flow into terminal
3- Ca2+ ions trigger the fusion of synaptic vessicles with the presynaptic membrane
4- Release of the transmitter into the synaptic cleft (exocytosis)
the ___ membrane contains ___ that bind the ____ released from the presynaptic terminal
postsynaptic
receptors
neurotransmitters
what are the 2 types of receptors on the post synaptic membrane in synaptic transmission (describe each)
ionotropic receptors: fast acting, ion channel, lets ions flow inside
metabotropic receptors: slow acting, second messenger activator
can both receptors be used depending on the needs
we might use one or both receptors depending on needs
what receptors have ion channel as an integrated part of them
ionotropic receptors
what are the 2 types of ion channels
cation and anion channels
describe cation channels (what do they allow to pass, what do they excite, give an example)
-they allow cations (Na+, Ca2+) to pass
-these channels excite (depolarize) the postsynaptic neuron
-Glutamate receptor
describe anion channels (what do they allow to pass, what do they inhibit, give an example)
-anion channels allow anions (Cl-) to pass
-these channels inhibit (hyperpolarize) the postsynaptic neuron
-GABA receptors
describe fast synaptic transmission
ion channels open and close rapidly (< sec) providing a very rapid control of postsynaptic neurons
what receptor is a protein structure that causes prolongued changes in the neurons
metabotropic receptor (second messenger activator)
how do metabotropic receptors cause prolongued changes in the neurons
by activating substances inside the postsynaptic neuron, slow synaptic transmission
what does one of the most common types of 2nd messenger system use
G-protein
what is the G protein complex attached to
to the inferior portion of the receptor protein
what activates the G-protein and what does it initiate
-the binding of the transmitter on the receptor activates the G-protein
-it initiates a cascade of events leading to alterations in the cellular activity
why do we need the metabotropic receptor sys
for memory and learning
what happens upon the activation of the G-protein
the alpha sub-unit detaches from the complex and activates multiple functions inside the cell
what does the binding of the neurotransmitter on the receptor open
ions channels and increases the permeability of ions
what does the post synaptic potential do to the postsynaptic mem
it causes the postsynaptic mem pot to change from the resting state
describe excitatory post-synaptic pot (what do the values of the mem pot move towards, what happens to the permeability, what is it caused by)
-the mem pot moves towards less negative values ( > Vm, depolarization)
-increased permeability to Na+ and/or Ca2+ (more positivity inside)
-caused by the activation of excitatory receptors
describe inhibitory post-synaptic pot (what do the values of the mem pot move towards, what happens to the permeability, what is it caused by)
-the mem pot moves towards more negative values ( < Vm, hyperpolarization)
-increased permeability to Cl- and/or K+ (more negativity inside)
-caused by the activation of inhibitory receptors
describe a neuron in an excited state
a less negative mem pot (caused by Na+ influx), getting depolarized
describe a neuron in an inhibited state
a more negative mem pot (caused by K+ efflux, Cl- ion influx, or both), getting hyperpolarized
what are characteristics of postsynaptic potentials of electrical events
- sub-treshold potentials (below treshold of AP)
- summation of different PSPs (spatial and temporal)
- EPSPs increase the likelihood of AP (signal transmission)
- IPSPs decrease the likelihood of AP (no signal transmission)
what is spatial summation
excitation of post-synaptic neuron by a single presynaptic terminal will almost never induce an AP
when will ESPSs summate and may exceed the threshold to generate an AP
when many presynaptic terminals stimulate the postsynaptic neuron and their respective ESPSs will summate
what is temporal summation
successive discharges from the same single presynaptic terminal, if they occur rapidly enough, can add to one another; that is, they can “summate” to reach the threshold for firing AP
t/f: APs begin near the synapses (soma and dendrites)
false they begin at the initial segment of the axon called axon hillock
soma and dendrites have few ____ (necessary for the generation of AP)
voltage-gated Na+ channels
where does the electrical signals propagate from and to and by what (give an ie)
electrical signals propagate from dendrites and soma to axon hillock by electrotonic conduction (propagation in the fluids w/o generation of AP)
what is synaptic plasticity (in response to what)
synaptic plasticity is the ability of a synapse to strengthen or weaken over time, in response to increases or decreases in its activity
what does synaptic plasticity result from (for the same stimulus)
-change in the qty of neurotransmitters released
-change in the nb of postsynaptic receptors
-change in the response of the postsynaptic neuron to transmitter (greater postsynaptic pot)
what are the types of synaptic plasticity
-synaptic enhancement (potential): increase in the efficacy of the synapse
-synaptic depression: decrease in the efficacy of the synapse
-short term plasticity: lasts from few millisecs to min
-long term plasticity: lasts from hours to months
what do the selective serotonin reuptake inhibitors do
antidepressant drugs:
-are believed to increase the extracellular level of serotonin by limiting its reabsorption into the presynaptic cell, increasing the level of serotonin in the synaptic cleft available to bind to the postsynaptic receptor
