5.3 neuronal communication

Question 1

What is negative resting potential?

Answer 1

When there is a difference in electrical charges in a resting neuron, this means that it is more positive on the outside and negative on the inside.

Question 2

How is negative resting potential created?

Answer 2

3 sodium are pumped to the outside of the nerve cell whilst two potassium are pumped into the inside via a sodium potassium pump. This creates an electrochemical gradient as it is more positive on the outside and negative on the inside. The potassium then diffuses out due to concentration gradient through the channel protein, which is only permeable to potassium. This makes the outside of the membrane more positive so the electrochemical gradient is steeper.

Question 3

What are the four types of sensory receptor

Answer 3

• Mechanoreceptor - chemoreceptor
• thermoreceptor
• photoreceptor.

Question 4

What stimulus does a mechanoreceptor respond to?

Answer 4

Pressure or movement.

Question 5

What stimulus does a chemoreceptor respond to?

Answer 5

Chemicals.

Question 6

What stimulus does a thermoreceptor respond to?

Answer 6

Heat.

Question 7

What stimulus does a photoreceptor respond to?

Answer 7

Light.

Question 8

How is action potential reached?

Answer 8

Stimulus causes the movement of sodium ions into the axon. If the threshold potential of -55 mV is reached the voltage gated sodium channels open, causing sodium ions to flood into the neuron. This causes the voltage to reach
+30mV. At +30mV the voltage gated sodium channels close and the voltage gated potassium channels open. This causes the potassium ions to flood out So -80mV is reached inside.

Question 9

What is depolarisation

Answer 9

The flooding of sodium ions into the axon to reach action potential.

Question 10

What is repolarisation?

Answer 10

The movement of potassium ions out of the axon.

Question 11

What is the refractory period

Answer 11

The time between action potential and reaching resting potential

Question 12

What is hyperpolarization?

Answer 12

Where too many potassium ions move out of the axon so it reaches -80mV. The sodium potassium pump brings the axon back to resting potential.

Question 13

What is threshold potential

Answer 13

-55mV
It is the potential required for depolarisation took her.

Question 14

How does the nerve impulse travel along the axon?

Answer 14

The sodium ions diffuse along the axon, which causes a local current.

Question 15

Why is there refractory. important?

Answer 15

It ensures a delay between action potentials and ensures that the impulses can only pass in one direction along the axon.

Question 16

What is for all or nothing principle?

Answer 16

The idea that there is no action potential if threshold potential is not reached.
When action potential is reached a more. intense stimulus would result in more frequent action potentials.

Question 17

What is the passenger corpuscle an example of?

Answer 17

mechanoreceptor.

Question 18

How does the pacinian corpuscle trigger a nerve impulse?

Answer 18

When pressure is applied, the layers are distorted, causing the stretch mediated sodium channels to open. This causes for sodium ions to enter the axon, creating action potential. Then the generator potential is where an influx of ions changes the potential of the axon, causing depolarization. This means action potential is established and a nerve impulse moods along the axon

Question 19

What are the features of sensory receptor?

Answer 19

They are specific to a single type of stimulant and act as a transducer.

Question 20

Why are sensory receptors transducers

Answer 20

They convert he stimulus into a nerve impulse.

Question 21

What are the three types of neuron

Answer 21

• motor
• sensory
• relay

Question 22

What are the features of a motor neuron?

Answer 22

• cell body in the CNS
• short dendrons
• long axon

Question 23

What are the features of sensory neuron?

Answer 23

• cell body
• long dendrons
• short axon

Question 24

What were the features of a relay neurone?

Answer 24

• cell body
• short dendron
• short axon

Question 25

What does the relay neuron do?

Answer 25

It connects the sensory and motor neurons.

Question 26

What is the difference between a dendron and an axon?

Answer 26

A dendron will transmit electrical impulses towards the cell body, whereas an axon will transmit electrical impulses away from the cell body.

Question 27

What is the myelin sheath made up of?

Answer 27

Schwann cells which wrap around the axon tightly, preventing ions from passing through.

Question 28

What is the benefit of having myelin sheath around a neuron?

Answer 28

It speeds up the transmission of the nerve impulse from 2 m/s to 200 m/s

Question 29

How does a myelinated neuron speed up the transmission of a nerve impulse?

Answer 29

The myelin prevents sodium ions passing into the axon from the voltage gated sodium channels surrounded by myeling which creates a longer local current. Instead, the sodium ions move into the axon from the nodes of ranvier.

Question 30

What is local current

Answer 30

The diffusion of sodium ions along the axon.