Roles of sensory receptors

Question 1

Sensory receptors

Answer 1

cells that respond to a stimulus in the internal/ external environment of an organism and can create action potentials.

Question 2

Define a transducer

Answer 2

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

Question 3

What kind of transducer are most sensory receptors

Answer 3

energy transducers.

Question 4

Transducer adaptation

Answer 4

adapted to detect changes in a particular form of energy. e.g changes in light levels, change in pressure on the skin.
each change in the environment is called a stimulus.
Whatever the stimulus, the sensory receptors respond by creating a signal in the form of electrical energy.- nerve impulse

Question 5

Change in light intensity- the sensory receptors and energy change involved.

Answer 5

Light sensitive cells in the retina - light to electrical

Question 6

Change in temperature- the sensory receptor and the energy change involved

Answer 6

Temperature receptors in the skin and hypothalamus- heat to electrical

Question 7

Change in pressure on the skin- sensory receptor and energy change involved

Answer 7

Pacinian corpuscles in the skin- movement to electrical

Question 8

Change in sound- sensory receptor and energy change involved

Answer 8

Vibration receptors in the cochlea of the ear- movement to electrical

Question 9

Movement- sensory receptor and energy change involved

Answer 9

Hair cells in inner ear- movement to electrical

Question 10

Define a Pacinian corpuscle

Answer 10

a pressue sensor that detects change in pressure on the skin.

Question 11

Pacinian corpuscle structure

Answer 11

oval- shaped consists of rings of connective tissue wrapped around the end of the cell. When pressure on the skin changes this deforms the rings of connective tissue, which push agains the nerve ending.

Question 12

What do the Pacinian corpuscle do when the pressure is constant?

Answer 12

They stop responding because as the corpuscle is only sensitive to changes in pressure that deform the rings of connective tissue.

Question 13

What do plasma membranes contain?

Answer 13

proteins.
some are channels- allow the movement of ions acreoss the membrane by facilitated diffusion
others are transport proteins- actively move ions across the membrane against their concentration gradient which requires ATP.

Question 14

What happens if channel proteins are permanently open?

Answer 14

then ions can diffuse across the membrane and will until until their concentrations are in equilibrium.

Question 15

What happens if the channel proteins can be closed?

Answer 15

then the action of the active pumps can create a concentration gradient across the membrane.

Question 16

What are the specialised channel proteins in the nervous system?

Answer 16

Sodium channels are specific to sodium ions.
Potassium channels specific to potassium ions.
These channels possess a gate that can open or close the channel.

Question 17

What do the sodium channels do?

Answer 17

they are sensitive to small movements of the membrane when the membrane is deformed by the changing pressure the sodium channels open.
This allows sodium ions to diffuse into the cell, producing a generator potential.

Question 18

What is the role of sodium/potasssium pumps

Answer 18

they pump sodium ions out of the cell
and pump potassium ions into the cell.

Question 19

What is the ratio of sodium ions being pumped out compared to potassium ions being pumped in?

Answer 19

3Na+ pumped out
2K+ pumped in

Question 20

What do the sodium/ potassium pumps do when the channel proteins are all closed?

Answer 20

they work to create a concentration gradient.
The sodium ions outside the cell increases, while the concentration of potassium ions inside the cell increases.

Question 21

What is the ions that the membrane is more permeable to and what does this mean?

Answer 21

Potassium ions- some of these leak out of the cell.
the membrane is less permeable to sodium ions - few of these able to leak out.

Question 22

What is the result of the ionic movements?

Answer 22

a potential gradient across the membrane.
The cell is negatively charged inside compared to outside.

Question 23

What happens when the cell is inactive?

Answer 23

the cell membrane is polarised.
negatively charged inside compared with outside.

Question 24

How is a nerve impulse created?

Answer 24

by altering the permeability of the nerve cell membrane to sodium ions.
achieved by opening the sodium ion channels, when open, the membrane permeability is increased and sodium ions can move across the membrane down their concentration gradient into the cell.

Question 25

What does the movement of ions across the membrane create?

Answer 25

a change in the potential difference.
the inside of the cell becomes less negative- depolarisation
the change in potential across a receptor membrane called a generator potential.