neuronal communication

Question 1

what is a stimuli?

Answer 1

a change detected in environment

Question 2

what are sensory neurons?

Answer 2

cells/sensory nerve endings that respond to a stimulus in the internal external environment of an organism and create action potential. They detect changes in our environment(stimuli).

Question 3

what are transducers

Answer 3

a cell that converts one form of energy to another -in this case to an electrical impulse.

Question 4

Types of sensory receptors

Answer 4

• mechanoreceptors
• chemoreceptors
• thermoreceptors
• photoreceptors

Question 5

what are Pacinian corpuscles

Answer 5

This is a pressure sensor that detects changes in pressure on the skin.

Question 6

describe the structure?

Answer 6

oval-shaped structure that consists of a series of concentric rings of connective tissues wrapped around a nerve cell.

Question 7

use of dendrite

Answer 7

carry nerve impulses from a receptor or from another neurone towards the cell body

Question 8

use of axon

Answer 8

carry nerve impulses away from the cell body towards another neurone or a muscle or gland.

Question 9

how do Pacinian corpuscles respond to stimulus

Answer 9

pressure deforms causing stretch mediated na+ ions channels to open.
an influx of na+ raises membrane threshold potential, a generator potential is produced
action potential is transmitted along axon of sensory neurons

Question 10

describe sensory neurons and state function

Answer 10

unipolar

transmits nerve impulse from sensory receptors to CNS

Question 11

describe relay neuron and state function

Answer 11

bipolar

connects motor neuron and sensory neuron

Question 12

what is resting potential

Answer 12

the potential difference across the membrane while the neuron is at rest.

Question 13

what is the resting potential value?

Answer 13

-60mV

Question 14

how is resting potential maintained?

Answer 14

by the action of the sodium-potassium pumps which actively transports 3 Na+ out of the cell of every 2 K+ transported in.
• Note that all voltage-gated Na+ channels and most K+ channels are closed.
• Leakage of potassium ions by facilitated diffusion through potassium ion channels because the membrane is more permeable to potassium ions.

Question 15

how do we generate A.P ?

Answer 15

1. The membrane starts in its resting states with a potential difference of -60mV. there is a higher concentration of sodium ions outside than inside and a higher concentration of potassium ions inside than outside.
2. Sodium ion channels open and some sodium ions diffuse into the cell.
3. The membrane depolarises under which is a threshold value of -50mV.
4. Positive feedback causes nearby voltage-gated sodium ion channels to open and many sodium ions float in. as more sodium ions entering the cell becomes positively charged inside compared with outside.
5. The potential difference across the plasma membrane is +40mV. The inside of the cell is positive compared with the outside.
6. The sodium ion channels close on potassium channels open.
7. Potassium ions diffuse out of the cell bringing the potential difference back to the negative inside compared with the outside -this is called repolarization.
8. The potential difference overshoots slightly making the cell hyperpolarized.
9. The original potential difference is restored so that the cell returns to its resting state.

Question 16

why can’t an action potential be generated immediately after one action potential?

Answer 16

still in refractory period.

• the cell membrane has not reached the resting potential yet.
• the sodium and potassium ions are in the wrong place.