4. Receptors

Question 1

How are receptors specific?

Answer 1

Only decent one particular stimulus.
Light
Glucose conc
Pressure

Question 2

What can receptors be ?

Answer 2

Cells - photoreceptors

Proteins - cell surface membrane glucose on pancreatic membrane

Question 3

Who do receptors in nervous system convert energy of stimulus into ?

Answer 3

Electrical energy used by neurones.

Question 4

Name 3 stages of how receptors work ?

Answer 4

Resting potential.
Generator potential.
Action potential.

Question 5

When a nervous system receptor is in return state, what’s the charge like ?

Answer 5

There’s a difference in charge of inside and outside of cell.
Inside - negatively charged relative to outside.

Question 6

Because there’s a difference in charges across membrane , what does it mean ?

Answer 6

There’s a voltage across membrane.

Potential difference.

Question 7

What is voltage also known as?

Answer 7

Resting potential .

Question 8

How is the resting potential generated ?

Answer 8

By ion pumps and ion channels.

Question 9

What happens when stimulus is detected ?

Answer 9

Cell membrane is excited and becomes more permeable.
Allowing more ions to move in and out of cell.
This alters the potential difference.

Question 10

So the stimulus causes a change in what?

Answer 10

Potential difference.

Question 11

The change in potential difference due to stimulus is called what?

Answer 11

Generator potential.

Question 12

What does a bigger stimulus do ?

Answer 12

Excites membrane even more.

Causing bigger movement of ions and bigger change in potential difference -so bigger generator potential.

Question 13

What is potential difference across membrane measured in?

Answer 13

Millivolts.

Question 14

What happens if the generator potential is big enough ?

Answer 14

It will trigger an action potential - electric impulse along neurone.

Question 15

However, when can an action potential only be reached?

Answer 15

When generator potential reaches threshold level.

Question 16

How is the strength of action potentials measured ?

Answer 16

The frequency as the action potentials are all one size.

Question 17

What happens if stimulus is too weak ?

Answer 17

Generator potential won’t reach threshold - no action potential.

Question 18

What are pacinian corpuscles examples of ?

Answer 18

Mechanoreceptors
Decent mechanical stimuli
Pressure
Vibrations

Question 19

Where are pacinian corpuscles found ?

Answer 19

Skin

Question 20

What do pacinian corpuscles contain ?

Answer 20

End of sensory neurone , sensory nerve ending.

Question 21

What is the sensory nerve ending wrapped around?

Answer 21

Lots of layers of connective tissue - lamellae

Question 22

What happens when a pacinian corpuscle is stimulated ?

Answer 22

The lamellae become deformed and press the sensory nerve ending.
Sensory neurones cell membrane stretches, deforming stretch meditated
sodium ion channels.
Channels opens
Sodium ions diffuse into cell generating generator potential.

Question 23

How did stretch mediated sodium ions get their name?

Answer 23

Because they only open and let sodium ions pass through they’re stretched.

Question 24

When the stimulus is applied, which sodium ions open?

Answer 24

They open where the stimulus is being applied so sodium ions diffuse into cell.
Sodium ions however remain closed where stimulus is not present. So no diffusion here

Question 25

The bigger the stimulus…

Answer 25

More pressure applied 
More sodium channels opens 
Creates bigger generator potential
More likely to reach threshold 
More like to crest action potential