Review

Question 1

Depolarization of the nerve cell membrane occurs when there is a rapid inflow of

Answer 1

Sodium ions

Question 2

When does an action potential occur

Answer 2

When the local potential reaches the threshold level

Question 3

Continuous conduction of an action potential means that

Answer 3

One action potential stimulates the production of a new action potential at the adjacent site

Question 4

Which of the following occurs in electrically excitable cells

Answer 4

Depolarization causes voltage gated sodium on channels to open

Question 5

A specialized junction through which impulses pass from one neuron to another via chemical messengers ( neurotransmitters).

Answer 5

Synapse

Question 6

Synaptic transmission sequence

Answer 6

1. Ap causes release of neurotransmitter
2. Neurotransmitters diffuse across the synaptic cleft
3. Neurotransmitter binds with receptors on the post synaptic cell
4. Membrane permeability to sodium ions on post synaptic cell increases
5. Then sodium ion diffuse into the cell and cause a local potential.

Question 7

A sensory neuron

Answer 7

Always release a neurotransmitter that excites the neurons

Question 8

Neurons controlling muscles reflexes transmit AP quickly where as those controlling digestive secretions are slower.
Which neurons likely have myelinated axons and what type of AP conduction do they perform

Answer 8

Neurons controlling muscle reflexes
Saltatory conduction

Question 9

Axons may be myelinated or unmyelinated

Answer 9

True

Question 10

AP move along unmyelinated axons by

Answer 10

Continuous conduction

Question 11

Voltage gates open and close sequentially along the entire length of the axon

Answer 11

True

Question 12

AP travel down myelinated axons quickly by

Answer 12

Saltatory conduction

Question 13

Ap potential are generated only at the nodes of ranvier, giving the appearance of an AP jumping from node to node

Answer 13

True

Question 14

On a graph of an action potential the repolarization phase appears as a ……downward trend in the membrane potential, meaning it is quickly becoming more……

Answer 14

Steep
Negative

Question 15

Repolarization is the second phase of an action potential

Answer 15

True

Question 16

Repolarization involves a negative change in membrane potential because:

Answer 16

Sodium voltage gates close preventing further depolarization
Potassium voltage gates open fully allowing potassium to leave the cell
The exit of potassium returns the membrane toward-70 mV

Question 17

On a graph of an action potential, the depolarization phase appears as a …… upward trend in the membrane potential, meaning it is quickly becoming more……

Answer 17

Steep
Positive

Question 18

Action potential true statements

Answer 18

Sodium entered the cell as it diffused down its concentration gradient.
Entry of sodium through one channel stimulates the next channel to open.
The membrane potential depolarizes from-70 to +30 mV.

Question 19

Why is the PSP from synapse 3 the only one to trigger an action potential? Assume the PSPs from all synapses are EPSPs of identical strengths

Answer 19

Signals from synapses 1 and 2 lose too much strength because they have farther to travel.

Question 20

True statements about temporal summation

Answer 20

Individual EPSPs are too weak so multiple signals are needed to reach threshold.

The strength of each EPSP fades with time, so signals Mia occur in a quick succession.

Question 21

True statements to generate IPSP

Answer 21

Cl- enters the cell, making the membrane potential more negative

K+ exit the cell, making the membrane potential more negative.

Question 22

To generate an EPSP

Answer 22

Sodium enters the cell making the membrane potential more positive

Question 23

Neurotransmitters bind to ligand gated channels causing them to open

Answer 23

True

Question 24

The nervous system is the major communication and control center of the body

Answer 24

True

Question 25

Nervous tissues contain neurons aka nerve cells that communicate with other body cells through electrical signals called

Answer 25

Action potential ( nerve impulses) and chemicals called neurotransmitters.

Question 26

Multipolar neurons are the most common structural type of neuron have 100 of dendrites that receive incoming signals that are transferred toward the cell body.

Answer 26

A single axon transmits the nerve impulse or action potential

Question 27

Two types of graded post synaptic potentials

Answer 27

EPSP excitatory which occurs in response to the opening of specific ligand gated ion channels in the membrane resulting in a increase of sodium into the cell causing depolarization

Second type is inhibitory IPSP which occurs when either ligand gated potassium or chloride channels open, depending on the specific neurotransmitter. This allows for influx of potassium or chloride resulting in hyperpolarization of the membrane.

Question 28

Multiple grades pSP are received at the dendrites and cell body.

Answer 28

They determine the resulting response of the neuron

Question 29

Threshold is -55 mV

Answer 29

If threshold is met then an action potential is generated

Question 30

Temporal summation

Answer 30

Occurs as multiple signals are sent from the same presynaptic terminal in a rapid fire fashion

Question 31

Spatial summation

Answer 31

R/t the proximity of the multiple postsynPtic potentials to each other and their relative distance to the axon hillock.

Question 32

Once threshold has been reached, voltage gated sodium channels within the trigger zone opens, allowing sodium to enter the cell causing depolarization and begin the propagation of the action potential 

Answer 32

Depolarization

Question 33

Voltage gated potassium channels open slowly during the rise of the AP, allowing an efflux of potassium. The combination of closing voltage gated sodium channels and opening potassium voltage gated channels results in

Answer 33

Replorization of the membrane towards -70mV

Question 34

Towards the end of repolarization the voltage gated potassium channels starts to close slowly causing and overshoot making the membrane more negative

Answer 34

Hyperpolarization
RMP is re established through the redistribution of ions by the sodium potassium pump and leakage channels

Question 35

Time period when the voltage gated sodium channels are inactivated and no new AP can occur

Answer 35

Absolute refractory period