1. Biological Foundations of Behaviour Flashcards
(93 cards)
T or f, action potentials may also move backward through axons in retrograde transmission.
true!
what is the difference between a bipolar and multipolar neuron?
bipolar –> has one dendrite
multipolar –> has more than one dendrite
both only have one axon
what is anterograde movement?
movement from soma (cell body) towards the axon terminus
What is the resting membrane potential? What is responsible for it?
-70mV
the inside of the cell is negative compared to the outside.
maintained by the Na/K ATPase and potassium leak channels
what does the Na/K ATPase do?
it pumps out 3 sodium ions and pumps in 2 potassium ions by hydrolyzing ATP. (primary active transport)
What is an action potential? What is depolarization?
the resting membrane potential is -70mV indicating that the cell is polarized (i.e. there is a difference in charge on either side of the membrane)
An action potential is a wave of depolarization in which this membrane potential is removed by the influx of positive ions (sodium ions).
t or f, the action potential is an electrical impulse
false, it is an electrochemical impulse, since it uses ions and not simply electrons.
Explain what causes depolarization down an axon, briefly.
voltage-gated sodium channels reach a threshold membrane potential of -50mV. They fully open allowing sodium to influx the cell down its concentration gradient. Sodium comes in bringing the MP to around +35mV. a little bit of sodium moves down the axon and slightly depolarizes the next section, bringing the nearby voltage-gated channels to -50mV. This propagates down the axon.
true or false, some of the voltage-gated sodium channels are partly open if the MP is at -60mV.
FALSE - they only open (and fully open) at their threshold of ~ -50mV. This is because an action potential is an ALL or NONE response (no such thing as half-assing it)
quickly after Na+ channels open they inactivate. What happens if another action potential comes?
They do NOT open. they are inactivated until the MP reaches normal again.
What channels help repolarize the membrane?
voltage-gated potassium channels which open at around +35mV an allow K+ to flow out of the cell
What are Schwann cells, what are oligodendrocytes?
Both are myelin-producing cells.
Schwann cells –> PNS
oligodendrocytes –> CNS
Explain saltatory conduction.
myelin sheath has no voltage-gated channels and no depolarization. However, intermittent gaps in myelin called nodes of Ranvier have both these things. membrane depolarization skips myelin sections allowing the action potential to propagate faster.
are all axons myelinated?
no
CNS Glial cells…explain
- astrocytes
- microglia
- Ependymal cells
- astrocytes –> guide neuron development and regulate neurotransmitters
- microglia –> remove dead cells and debris (like an immune cell)
- Ependymal cells –> produce CSF
What is the equilibrium potential?
This is the MP at which a given ion would have no flow based its gradients. (concentration gradient pulls it in, electrical gradient pushes it out)
sodiums is +50mV, potassiums is -90mV.
What is the Nernst equation?
An equation that allows you to find the equilibrium potential for any given ion.
Explain the absolute and relative refractory periods.
absolute RP –> a neuron will NOT fire as the sodium channels are inactivated (not the same as closed). these will become active once the MP is repolarized.
relative RP –> due to hyperpolarization, an AP will only occur if a strong depolarization occurs.
Explain the 7 step process of synaptic transmission at a chemical synapse.
- AP reaches the end of the pre-synaptic axon
- depolarization causes voltage gated calcium channels to open
- calcium influxes the cell and causes exocytosis of nt vesicles.
- nts diffuse into the synaptic cleft
- nts binds ligand-gated channels on post-synaptic neuron
- IF post-synaptic MP reaches threshold, VG-sodium channels open and an AP starts
- nts are degraded, removed, or taken back up.
what is a well known chemical synapse used in muscle?
Neuromuscular junction where acetylcholine is released.
what determines the effect on the post-synaptic cell, the neurotransmitter or the receptor?
The receptor determines the effect on the post-synaptic cell. therefore, a neurotransmitter can act as excitatory and inhibitory
What is an EPSP and IPSP?
These are excitatory and inhibitory post-synaptic potentials. most neurons have multiple axons providing stimuli. The summation of all this stimuli (all the EPSPs and IPSPs) determines whether the post-synaptic neuron will fire.
what are the forms of synaptic summation?
temporal - continuous stimuli adds up
spatial - multiple stimuli at a given point of time
how can a pre-synaptic neuron increase the intensity of its signal to the post-synaptic neuron?
temporal summation (increased AP frequency)
cannot change AP speed or strength, but can increase how often (limited by the absolute refractory period though)