Receptors

Question 1

What does the Pacinian corpulse respond to?

Answer 1

Changes in mechanical pressure

Question 2

What type of neurone is Pacinian corpulse?

Answer 2

A sensory neurone

Question 3

Properties of Pacinian corpulse ( similar to all sensory neurones)

Answer 3

• specific to single type of stimlus
• Produces a generator potential by acting as a transducer

Question 4

How does Pacinan corpulse specific to a single type of stimulus?

Answer 4

It will only respond to mechanical pressure

It will not respond to other stimuli such as heat,light or sound

Question 5

How does sensory neurone produces a generator potential by acting as a transducer?

Answer 5

All stimuli involve change in some form of energy

It is a role of transducer to covert the change in form of energy by the stimulus into form - nerve impulses (can be understood by body)

Stimulus always involve change in some form of energy e.g light,sound or mechanical energy

The nerve impulse is another form of energy

Receptors convert/transudce one form of energy to another

Generator potential

Question 6

What is a generator potentail?

Answer 6

Receptors in nervous system who convert the energy of stimulus into nerve impulse is a generator potential

Question 7

How does Pacinian corpulse produce a generator potential by acting as a transducer?

Answer 7

Transduce the mechanical energy of stimulus into generator potential

Question 8

What is an example of a mechanical stimuli that Pacinian corpulse respond to?

Answer 8

Pressure

Question 9

Where does pressure occur in body?

Answer 9

Occur deep within the skin

Most abundant in fingers, soles of feet anf external gentalia

Occur in joints , liagments, tendons - enable the organism to know which joints are changing direction

Question 10

Where is the sensory neurone located in Pacninan corpulse?

Answer 10

At the centre of layers of tissue - each separated by a gel

(giving an appearence of onion when cutting it)

Question 11

What is a stretch-mediated sodium channel?

Answer 11

The sensory neurone ending at the Pacinian corpulse has a special type of sodium channel in its plasma membrane

It is called stretch-mediated sodium channel

Question 12

Why are the names of the sodium channels of Pacninan corpulse weird?

Answer 12

Their permeability to sodium changes when they are deformed

e.g stretching

Question 13

What happens to Pacninan corpulse when it is at resting state?

Answer 13

Stretch-mediated sodium channels of the membrane around the neurone of a Pacinina corpulse are too narrow to let sodium ions to pass along them

In this state of the neurone of Pacinian corpulse has a resting potential

Question 14

What happens when pressure is applied to Pacinian corpulse?

Answer 14

• It is deformed of the membrane around its neurone becomes stretched
• Stretching widens the sodium channels in the membrane and sodium ions diffuse into the neurone
• The influx of sodium ion changes the potential of the membrane (i.e. becomes depolarised) thereby, producing generator potential
• Generator potential in turn creates an active potential (nerve impulse) that passes along the neurone via other neurones in CNS

Question 15

Diagram of Pacinian corpulse

Answer 15

Question 16

Where are the light receptor of the mammalian eye found in the intermost layer?

Answer 16

The retina

Question 17

What are the two types of light receptor cells found in the rectina?

Answer 17

1. Rod cells
2. Cone cells

Question 18

What do cone and rod cells act as?

Answer 18

Transducer

Conserving light energy into electrical energy of a nerve impulse

Question 19

Why can rod cells can only been seen in black and white?

Answer 19

They cannot distinguish different wavelengths of light

Question 20

How many rod cells are there?

Answer 20

More than cone cells

120 millions in each eye

Question 21

How are rod cells able to see in low light intensity (e.g night)?

Answer 21

• Many rod cells connected to a single sensory neurone in optic nerve
• A certain threshold has to be exceeded before generator potential is created in bipolar cells in whcih they are connected
• As a number of rod cells are connected to a single bipolar cell (retina convergence)
• Greater chance that threshold value will be exceeded than if only single rod cell were connected to each bipolar cell

Question 23

How do rods cell give low visual acuity?

Answer 23

• Consequence of many rod cells linked to a single bipolar cell is light recieved by rod cells share the same neurone only able to generate a single impulse travelling to the brain regardless of how many neurones stimulated
• Brain cannot distinguish between different sources of light that stimulated them
• Two dots close together cannot be resolved - single blob

Question 24

How do cone cells perceive in full colour?

Answer 24

Cone cells are of three different types

each responding to a different range of wavelength of light

depending on proportion of each type stimulated percieve images in full colour

Question 25

How many cone cells they are in the human eye?

Answer 25

6 million

less than rod cells

Question 26

How do cone cells respond to high light intensity and not low light intensity?

Answer 26

Cone cells have their own separate bipolar cell connected to the sensory neurone in optic nerve

stimulation of number of cone cells cannot be combined to help exceed the threshold value and so create generator potential

Question 27

How are cone cells sensitive to different specific ranges of wavelengths?

Answer 27

1. Cone cells contain different types of pigment from that found in rod cells
2. Pgiment in cone cells e.g idopsin requirre a higher light intensity for its breakdown
3. Only light of high light intensity will proviide energy to break down and create generator potential
4. Three types of pigment of cone cells each containing specific type of iodpsin

Question 28

How do cone cells have good visual acuity?

Answer 28

• Each cone cell has its own connection to bipolar cell
• If two adjacent cone cells