lec6- Animal nervous system part 2

Question 1

why do action potentials not get smaller over time?

Answer 1

Action potentials propagate down the axon without getting smaller, because new action potentials are continuously generated along the axon membrane

Question 2

what are the three steps to action potential propagation?

Answer 2

1. Na+ enters the axon attracting negative charges and repelling positive charges
2. Positive charges spread downstream, so the membrane downstream depolarizes
3. More Na+ channels open in response to depolarization when the adjacent membrane reaches threshold, resulting in new action potential

Question 3

why are action potentials unidirectional?

Answer 3

Action potentials are unidirectional due to the relative refractory period where hyperpolarization is making the membrane more negative than the resting potential meaning a stronger stimulus is required to raise membrane potential, and the absolute refractory period has inactivated Na+ channels that wont open for a while again, hence why action potentials can only go in one direction

Question 4

how is information in the nervous system encoded?

Answer 4

by the frequency of action potentials

Question 5

why do large diameter neurons transmit action potentials more frequently?

Answer 5

because they experience less resistance

Question 6

what is wrapped around neurons in the peripheral nervous system?

Answer 6

schwann cells

Question 7

what is wrapped around neurons in the central nervous system?

Answer 7

oligodendrocytes

Question 8

what do the cells that wrap around neurons form?

Answer 8

myelin sheaths

Question 9

what do myelin sheaths do?

Answer 9

act as insulation, preventing ion leaks

Question 10

what are the Nodes of Ranvier?

Answer 10

the gap between the myelination that has a cluster of sodium and potassium channels

Question 11

how does distance affect the amplitude of depolarization?

Answer 11

the longer the distance, the more the amplitude of depolarization decreases

Question 12

are action potentials regenerated at each node?

Answer 12

Yes

Question 13

what is saltatory action potential conduction?

Answer 13

action potentials being able to jump node to node due to the myelinated axons

Question 14

why are action potentials quicker in myelinated axons?

Answer 14

1. The myelination prevents ion leaks
2. Action potentials regenerate at the next node of ranvier
3. Signals continue to jump this way which is faster than an unmyelinated axon

Question 15

what is multiple sclerosis (MS)?

Answer 15

it is a disease that destroys the oligodendrocytes that make myelin sheaths in the CNS, resulting in slow electrical signals

Question 16

what is the synaptic cleft?

Answer 16

The gap between the Axon terminals and the dendrites

Question 17

what do synaptic vesicles contain?

Answer 17

neurotransmitters

Question 18

what is the presynaptic neuron?

Answer 18

The presynaptic neuron is the neuron with the axon terminal at the synapse

Question 19

what is a postsynaptic neuron?

Answer 19

The postsynaptic neuron is the neuron on the other side of the synaptic cleft, has the dendrites

Question 20

why are neural signals from neurotransmitters so fast?

Answer 20

because the neurotransmitters have to travel a short distance from presynaptic neuron to postsynaptic neuron

Question 21

how is information transferred at the synapse?

Answer 21

1. Action potential arrives at the end of the axon
2. Depolarization causes voltage gated calcium channels to open
3. In response to influx of calcium, vesicles fuse to presynaptic membrane and release neurotransmitters into synaptic cleft
4. Neurotransmitters bind to receptors on postsynaptic membrane causing change in membrane and chance for triggering action potential
5. Response ends when all neurotransmitters in synaptic cleft are either diffused away, digested, or taken up by presynaptic cell

Question 22

what do neurotransmitters bind to?

Answer 22

ligand-gated ion channels or G-protein coupled receptors

Question 23

what is EPSP (Excitatory postsynaptic potential)?

Answer 23

when the postsynaptic membrane is depolarized

Question 24

what is IPSP (inhibitory postsynaptic potential)?

Answer 24

when the postsynaptic membrane is hyperpolarized

Question 25

what do EPSP, IPSP, and both at the same time do?

Answer 25

EPSP make action potential likely, IPSP make action potential less likely, and both at the same time cancel out

Question 26

what does SSRI drug do?

Answer 26

SSRI is an antidepressant drug that inhibits serotonin (neurotransmitter) reuptake to make it last longer in the synaptic cleft and have more activity

Question 27

how are EPSPs and IPSPs graded?

Answer 27

in magnitude

Question 28

what happens when multiple EPSPs occur close together?

Answer 28

higher chance for action potential

Question 29

what is it called when EPSPs occur closely?

Answer 29

summation

Question 30

how do neurons integrate information from many synapses?

Answer 30

via the axon hillock that receives IPSPs and EPSPs allowing integration from a wide array