Nerve, Muscle, Synapse Flashcards
true or false - the withdrawal reflex is an autonomic behavior
true
what are the structures of the central nervous system
cerebral cortex, cerebellum, brainstem and spinal cord
what is the difference between the efferent and afferent neurons
afferent neurons - carry information from the outside to the spinal cords via the DORSAL roots
efferent neurons - carry information from the spinal cord to the outside via the VENTRAL roots
what are the name of the cells that are the most in number of the central nervous system
glia cells
what are the four functions of the different types of glia cells
- satellite cells provide structure/support neurons
- produce myelin
- radial glia guide neurons and development of axon’s outgrowth
- astrocytes form blood brain barrier
what are the cells in the PNS and CNS that make myelin
oligodendrocytes in CNS; Schwann cells in PNS
describe the stretch reflex
- patellar tendon is tapped
- makes the quadricep muscle stretch
- activates the afferent neuron
- then interneurons inhibit the efferent neuron
true or false - the synaptic terminals is the start/initial segment of the neuron
false - it is the axon hillock
what are the three different types of neurons
bipolar, pseudo-unipolar and multipolar
a motor neuron is
a) afferent
b) efferent
efferent
where is the bipolar neuron usually found
in the visual system (retina)
what is an example of a electrogenic transporter
Na/K pump
___ Na molecules move ___ of cell and ___ K meolcules move ___ cell
3, out, 2, in
is there a net positive or negative charge inside the cell
negative
true or false - leak channels are not always open
false they are always open
briefly describe leak channels
- they passively allow ions in and out but they are very selective in which each ion has its own leak channel
- two forces involved ; chemical and electrical gradient
what is the equilibrium potential for K and Na
K is -90mV
Na is +60mV
if there are both Na and K present in nerve cells, what happens to the resting membrane potential
the ion that has the most permeability to the membrane will impact the EM the most
if the RMP was +75, would there be more Na or k leak channels and why
there would be a lot more Na channels because its RMP on its own is about +60 so it is close to +75, therefore there is greater permeability to Na
choose the factors that do not play a role in setting RMP
Na, Cl-, K, and anions
Cl- and anions do not play a role because
1. Cl’s equilibrium potential = RMP
2. anions are too big
true or false - the cell can sometimes be at rest/quiet
false it is never quiet because either one of the ions is never happy until it has reached its preferable EP and when the cell is at -70mV, neither of the ions are happy
what is the definition of action potential
a change in membrane potential from -70mV to +30mV and then back to rest
at rest, the voltage gated channels are open/closed
closed
what is the difference between absolute and refractory period
absolute - not able to generate another AP
refractory - possibly able to generate another AP
what is a major factor in keeping the signal flow in one direction
refractory period
what is the steps of an action potential being generated in terms of channels and gates
activated stimulus -> increase in permeability to Na ions -> Na flows in -> Na gate deactivates and K opens -> K rushes in -> so much rushes out that the membrane potential reaches below resting potential -> back to rest
which of the ions are associated with depolarizing and repolarizing phases
Na - depolarizing
K - repolarizing
what is the term given to the spread of current inside an axon
electric conduction
what are the three types of neurons
inter/afferent/efferent neurons
true or false - afferent and efferent neurons can be inhibitory
false - only excitatory
what is myelin made of
80% lipid and 20% protein
complete the following scenarios
if myelin is there….
if myelin is not there
if myelin is there, there is no need for regeneration of AP and so it is one smooth current
if myelin is not there, the AP would leak out the nerve fibres
true or false - oligodendrocytes are found in the PNS
false - they are found in the CNS
what is the only place in the neuron that has myelin
axon
why is the myelin not continuous
because of nodes of ranvier
true or false - one oligodendrocytes ensheath many axons
true
many schwann cells ensheath many/1 axon
1 axon
does saltatory conduction occur with or without myelin
only when there is myelinated fibre
what happens with multiple sclerosis
the myelinated nerve fibres become degenerated therefore, the pattern of node ranvier and axons are abnormal -> AP is not generated at the speed its supposed to so there is inappropriate pain responses
define proprioceptor
occurs in muscle and allows us to know where our muscles are in space without looking
order the fibre types from lowest AP frequency to highest
Group 4, group 3, group 2, group 1
what are the associated sensory receptors with the fibre types
group 1 - skeletal muscle and proprioceptor
group 2 - skin mechanoreceptor
group 3 - pain and temperature
group 4 - pain, itch and temperature
what is the direction of the AP
it arrives at the axon from left to right
true or false - synaptic transmission is only electrical
false - it is electrical or chemical
what is the significance of electrical synapses
it is fast and bidirectional
what is an important structure of electrical synapses
connexons - work to fuse two cells together
how does directly gated chemical synapses work
transmitter binds -> channel opens -> excitatory ions pass through (K and/or Na) -> for inhibition, Cl- or K will pass through
how does indirectly gated chemical synapses work
transmitter binds -> activation of 2nd messenger system -> causes cAMP to activate protein kinases to phosphorylate channels -> channels open/close -> ions flow in/out
how does the 2nd messenger system become activated
via G proteins - GTP activates adenylyl cyclase which then converts ATP to cAMP
what is the name of the 2nd messenger system
cAMP
true or false - receptor and effector(ion channel) are different molecules in indirectly gated chemical synaptic transmission
true
provide the differences between electrical and chemical synapses
chemical - flexibility, inhibition, plastic, complex
electrical - inflexible, difficult to change, great for stereotypical behaviors
what is the course of events for synaptic transmission
- action potential starts at the pre synaptic terminal
- depolarization of pre synaptic terminal
- Ca voltage gated channels open and influx of Ca
- this influx of calcium allows the synaptic vessicles to fuse with the presynaptic membrane
- transmitter is released by exocytosis and binds to ligan gated ion channels
- ions flow across membrane by their concentration gradient
- the postsynaptic cell can either be hyperpolarized or depolarized
- once the channel closes, the transmitter is then recycled
how can a presynaptic neuron be excitatory
it can release the excitatory neurotransmitter glutamate
- glutamate binds and opens the Na ligand gated channels
- Na enters and causes depolarization aka EPSPs
how can a presynaptic neuron be inhibitory
it can release glycine or GABA
- inhibitory transmitter binds and opens ligand gated Cl channels
- Cl enters and causes hyperpolarization aka IPSPs
- no more generation of APs
true or false - the synpatic potentials travel away from cell body
true
true or false - as the synpatic potentials travel, it gets stronger and stronger
false - it decays with distance
describe temporal summation
PSPs from a single presynaptic axon will overlap in time and add together
- this happens when EPSPs are too small on their own so they are able to sum together to get to threshold and trigger an AP
describe spatial summation
PSPs in different regions of the postsynaptic neuron are added together
- this happens when EPSPs from different areas on their own are too small on their own so they are able to sum together to get to threshold and trigger an AP
a neuron sits at -70mV and has a threshold of -50mV, it then receives 10 IPSPs of 0.5mV each and 20 EPSPs of 1mV each. does the cell fire an AP
first, the cell needs 20mV to fire an AP (50-70)
- 10IPSPs x 0.5mV = -5 because it is hyperpolarized
- 20 EPSPs x 1mV = +20
in total that is +15mV which is less than what it needed, therefore no AP is generated
compare PSP and AP in areas of amplitude, duration, location, conduction and function
PSP
amplitude - depolarization or hyperpolarization
duration - long
location - dendrites and soma
conduction - short distances
function - moves the postsynaptic neuron closer to or further from threshold
AP
amplitude - all or none
duration - short
location - start at axon hillock to terminal
conduction - long distances
function - AP is conducted to the terminal where it causes a PSP in the post synaptic neuron
name the three types of muscle
smooth, cardiac and skeletal
of the three types of muscles, which are involuntary and voluntary
cardiac and smooth are involuntary
skeletal is voluntary
where is smooth muscle found and what is its function
it is found in hollow organs
functions :
1. regulates blood flow in arteries
2. moves food through GI tract
3. expels urine
4. regulates flow of air in lungs
what is the main function of cardiac muscle
found in the heart walls where it propels blood into the heart and through the circulatory system
true or false - skeletal muscle is non striated
false - it is striated
name 2 differences between synaptic transmission at a central synapse and a neuromuscular junction
- one action potential in a motorneuron initiates one AP in a muscle cell
- there are no inhibitory neurotransmitters that are released to stop the activity
how is muscle action stopped if there are no inhibitory neurotransmitters
lack of neurotransmitter, which means lack of activity = inhibition
how is acetycholine released and what happens when it is
it is contained in vesicles and it is released through exocytosis and into the synaptic cleft
- when this happens, calcium ions are pumped out
what is a major role of calcium
it triggers contraction of muscles
what part of the sarcomere does not change during contraction and relaxation
the H zone
what are the steps of cross bridge cycling
- influx of calcium allows the binding of site on actin to be available
- myosin binds to actin
- power stroke of cross bridge allows the sliding of the thin filaments
- the cross bridge disconnects when ATP is bound to it
- the cross bridge will reposition itself once ATP goes through hydrolysis
- calcium ions travel back to the. sarcoplasmic reticulum
explain the three roles of ATP in muscle cells
- energized the power stroke
- disconnects the myosin cross bridge from actin binding site
- helps transport Ca back into the sarcoplasmic reticulum
what are the two types of muscle fibres
red and white
list the features of red muscle fibres
- shorter than white fibres
- lots of myoglobin so very red
- lots of mitochondria
- low glycogen content
list the features of white muscle fibres
- larger than red fibres
- not so much myoglobin so light in color
- few mitochondria
- high glycogen content
how do white muscle fibres synthesize ATP
through glycolysis because they have a high glyocgen content
how do red muscle fibres synthesize ATP
using Krebs cycle and oxidative phosphorylation
what is another name for white muscle fibres
fast twitch glycolytic fibres
true or false - white muscle fibres are suited for activities requiring power and speed for a long period of time
false - it is only suitable for a short amount of time
true or false - red muscle fibres are fatigue resistant and have high endurance
true
