Neural Communication

Question 1

Examples of internal environment

Answer 1

○ Blood glucose concentration
○ Internal temperature
○ Water potential
○ Cell pH

Question 2

Examples of external environment

Answer 2

○ Humidity
○ External temperature
○ Light intensity
○ New or sudden sound

Question 3

Define transducer

Answer 3

Converts a stimulus into a nerve impulse

Question 4

Examples of transducers

Answer 4

○ Chemoreceptor - chemical energy
○ Osmoreceptor - chemical energy
○ Photoreceptor - light energy
○ Thermoreceptor - heat energy
○ Baroreceptor - Pressure

Question 5

What type of energy does the Pacinian corpuscle convert?

Answer 5

Mechanical pressure -> nerve impulse

Question 6

How does the Pacinian Corpuscle work?

Answer 6

1. When pressure is applied, the shape changes. The neurone’s membrane stretches
2. Sodium ion channels open, sodium ions move through
3. Depolarisation occurs due to the influx of positive ions = generator potential
4. Generator potential cause action potential (electrical impulse) that passes along the sensory neurone

Question 7

Name the 3 neurones

Answer 7

Relay neurone
Sensory neurone
Motor neurone

Question 8

Order of electrical transmission

Answer 8

Receptor -> Sensory neurone -> relay neurone -> CNS -> relay -> Motor -> target tissue

Question 9

How does myelin sheath speed up action potential

Answer 9

Depolarisation can only occur in the nodes of Ranvier, which allows sodium ions to enter.
The sodium ion is attracted to the negative region, which causes that area to become positive, and more depolarosation occurs
The myelin sheath doesn’t allow a change in charge so that region will remain positive, making the charge ‘jump over it’

Question 10

Define resting potential

Answer 10

The potential difference across its membrane when the neuron is not transmitting an impulse

Question 11

How is a resting potential created

Answer 11

○ For every 3 sodium ions that are actively transported out, 2 potassium ions are pumped in (through the sodium-potassium pump)
○ Therefore there are more sodium ions outside the membrane than in the axon cytoplasm
○Sodium ion channels are closed, but the potassium ion channels are open = Potassium conc. is lower on the outside, so they diffuse out of the axon
○ More positively charged ions outside the axon

Question 12

Numerical value of resting potential

Answer 12

-70mV

Question 13

How is action potential generated

Answer 13

○ Stimulus causes sodium ion channels to open
○ Sodium ions flood in (depolarisation)
○ Influx of sodium ions cause more channels to open
○ Depolarisation occurs throughout axon (wave of depolarisation)
○ Repolarisation - previous sodium ion channels close, potassium ion channels open, and potassium ions flood out

Question 14

What happens when the stimulus size increases

Answer 14

The depolarisation size stays the same (-70mV) , but depolarisation happens quicker

Question 15

Define hyperpolarisation

Answer 15

The outside of the axon becomes more negative than when at resting potential