Topic.5.TheNeuron.powerpoint.5.2.Neuronal.Functioning Flashcards
What increases the conduction potential of AP, aka speed neurons transmit signals?
Having a larger diameter
Nerve fiber
axon and dendrite of a nerve cell
List the the four types of nerve fibers from lease to greatest conduction potential of
c-nerve fiber, A-delta nerve fiber, A-beta nerve fiber, A-alpha nerve fiber
A-alpha nerve fibers carry
information related to
muscle sense(proprioception)
A-beta nerve fibers carry
information related to
touch
A-delta nerve fibers carry
information related to
pain and
temperature
C-nerve fibers carry information
related to
pain, temperature and
itch
Another contribution besides diameter that contribute to C-nerve fiber’s extremely low speed in transmitting neurons is…
not myelinated
What two creatures have a large diameter axons? Why?
Squids and earthworms; fast conduction=fast response aka muscle contraction for escape response
using a large-diameter water hose. Fill in :
Larger diameter – lower___faster
____
lower internal resistance, faster
conduction
Cable theory is used to understand ___ by calculating the flow of ___
conduction velocity, electric currents along an axon
In the Cable theory, what two things are taken into account in order to calculate conduction velocity?
-capacitances
-resistance
Capacitance refers to___
stored electrical charge
What causes capacitance in the cable theory?
electrostatic forces that
act through the phospholipid
bilayer
What causes resistance(longitudinal or membrane resistance) in the cable theory?
resistance is due to the
cytosol’s significant resistance
to movement of electric charge
Ex: organelle
Explain what this teaches us:
2λ, it will be 37% of the size it was at 1 λ,
λ (length constant), a measure of
how far the voltage travels down the axon before it decays to 37% of its size(1/3)
if you apply a voltage of 90mV at a specific spot on the axon, at the distance of 1 λ, the voltage would be ____
At a distance of 2λ, the voltage would be about ____
~30mV;10mV.
if you have a length constant of 1 mm, that means at____ away from the cell body in an axon, ___% of
the voltage magnitude remains.
1 mm;37%
How does have a larger length constant relate conduction velocity? Why?
A larger length constant gives greater conduction velocity.
-Can reach threshold further down axon each time the AP is generated.
-AP doesn’t have to be regenerated as many times
What is the equation that shows lambda is dependent on resistance?
λ= sqrt(rm)/(rl)
rm = resistance of
membrane
rl = longitudinal
resistance/cytosol resitance
Using the lambda equation, how can I increase the amount of current that will remain inside the cytosol to travel longitudinally along the neuron
Asking about how to increase lambda, you will increase the membrane resistance(rm)
How does myelin relate to conduction velocity?
Myelin increases rm and speeds conduction velocity. Ions can’t leave the axon in areas covered by myelin, so those ions with travel to regenerate the action potential at the next nodes of Ranvier.
Chemical synapses:
Allow neurons to receive inputs from
numerous axon terminals at the same time.
neurotransmitters:
small signal molecules secreted by
the presynaptic nerve cell to relay the signal to the postsynaptic nerve cell.
What are the two types of neurotransmission at the chemical synapse?
Direct and indirect
What is the difference between a direct and indirect neurotransmission
1.Direct neurotransmission:
-Neurotransmitter binds directly to a ligand-gated ion channel
-Quick (0.2msec)
-Ionotropic receptors form an ion channel pore
2. Indirect Neurotransmission
-Neurotransmitter first binds to G-protein coupled receptors on postsynaptic membrane to activate a second messenger pathway
-Slower (100msec)
-metabotropic receptors: indirectly linked with ion channels on the cell plasma membrane through signal transduction mechanisms, often G proteins
In neurotransmission, information at the post-synaptic end is ___ resulting in a ___ or ___ effect
integrate, inhibitory effect ,stimulatory effect
What is the acronym to remember all the direct neurotransmitters?
A Gray Grumpy Gorilla Named Dave Sings.
Acetylcholine
neurotransmitter between nerves and muscles; found in the brain (memory, attention, learning); and in
the heart
Ex: Alzheimer Disease
GABA (gamma aminobutyric acid)
inhibitor of neurotransmission through increase Cl- influx
Glycine
inhibitor of neurotransmission through increase Cl- influx
Glutamate
involved with learning and memory; generally excitatory
Norepinephrine and epinephrine (adrenaline)
duel roles as hormones and
neurotransmitters; involved in attention and mental focus, can be excitatory or inhibitory
Adhd
Dopamine
Neurotransmitter/neurohormone. Behavior and cognition voluntary movement, motivation and reward, lactation
Ex: Parkinson’s
What 3 neurotransmitters are derived from tyrosine?
Norepinephrine, epinephrine, dopamine
Serotonin
derived from tryptophan, regulates intestinal movements, involved in mood, appetite, sleep
Indirect neurotransmitters are called
Neuropeptides
What is the acronym to remember indirect neurotransmitters?
“Every Evening, Sarah Cooks Noodles
Endorphins: (“endogeneous morphines”)-
released during pleasurable experience, reduce the perception of pain, work on PNS
Enkephalins:
subset of endorphins, work in CNS, modulate
pain response
Substance P:
released by spinal cord, increase the perception
of pain
Dissolved carbon monoxide:
regulates the release of
hormones from the hypothalamus
Dissolved nitric oxide
learning, muscle movement.
Relaxes smooth muscle in the walls of blood vessels,
causes dilation
Synaptic vesicles
store neurotransmitters in cytoplasm of axon terminal
Explain steps of neurotransmission at a chemical synapse
- action potential arrives at the axon terminal of the presynaptic neuron
- Voltage-gated Ca2+ channels open, and influx
- Synaptic vesicles, fuse with the membrane and release neurotransmitters (exocytosis) into synaptic cleft
4.Neurotransmitter binds to post-synaptic receptor and open ligand-ion-gated channels
5.stimulate or inhibit the generation of an
action potential in the post synaptic cell
How does neurotransmission end? Steps?
- stimulus subsides, no action potentials are generated, voltage-gated Ca2+ channels close
2.Ca2+ is pumped outside of the axon terminal, vesicles no longer fuse with the membrane - remaining neurotransmitters in the cleft diffuse away or are broken down
What does it by: neurotransmitters can stimulate the generation of an
action potential in the post synaptic cell?
Na+ channels open, Na+ enters, the cell
membrane depolarizes, action potential threshold is reached
EPSP
excitatory post synaptic potential: change in membrane potential that moves the neuron closer to threshold
What is inhibition in neurotransmission?
K+ exits membrane becomes hyperpolarized, no action potential in the post synaptic cell)
IPSP
inhibitory post synaptic potential: change in
membrane potential that pushes the membrane farther from threshold
EPSPs and IPSPs are ___
EPSPS and IPSPS have no ____
EPSPs and IPSPs are graded potentials
EPSPS and IPSPS have no refractory periods
Graded potential:
is an increase or decrease in
membrane potential that is below threshold, so it does
not trigger an action potential.
Graded potentials can occur in
Graded potentials can occur in a sensory cell when a sensory stimulus excites it, or in a postsynaptic cell when a chemical neurotransmitter binds to it.
EPSPs (Graded potentials) are the precursors
to Action
Potentials.
Information is received
as changes in ___
Information is transferred
over distance by ___
potential: graded potentials; action
potentials
What is reuptake?
When remaining neurotransmitter are broken down, a molecule goes back to the pre-synaptic cell to start making the neurotransmitter again
If a person has early Alzheimer what might we give them?
Aricept:
Acetylcholinesterase
Inhibitor, treat it by keeping acetylcholine in the synapse longer
What are SSRI?
Selective serotonin
reuptake inhibitors
Antidepressants
prevent it from being repackaged
SSNRIs
selective
serotonin-
norepinephrine
reuptake Inhibitors
Anti depressants
graded potential characteristics
-size dependent on stimulus intensity or amount of transmitter
-can be depolarized/hyperpolarized
-decrease with distance
-rise and fall not instantaneous
-responses can sum
Are graded potential different from action potential?
Graded have no all or nothing decreases with distance. Also doesn’t depend on frequency but rather amount of neurotransmitters. Slower not instantaneous and responses are summed
Graded Potentials: what are the two types of responses that can sum?
temporal summation: summation of more than one EPSP produced by
successive firing of a single presynaptic neuron over a short period of time.
Spatial summation: summation of EPSPs produced by the firing of different
presynaptic neurons
