receptors

Question 1

receptors are specific, what does this mean

Answer 1

they only detect one p articular stimulus, e.g. light, pressure or glucose concentration.

Question 2

There are many different types of receptor that each detect _______

Answer 2

a different type of stimulus

Question 3

what type of receptor is a photoreceptor

Answer 3

cells

Question 4

what are the three types of receptors

Answer 4

cells, proteins, cell surface membranes

Question 5

what are photoreceptors

Answer 5

photoreceptors are receptor cells that connect to the nervous system.

Question 6

what are glucose receptors

Answer 6

glucose receptors are proteins

found in the cell membranes of some pancreatic cells.

Question 7

what happens when a nervous system receptor is in its resting state

Answer 7

When a nervous system receptor is in its resting state (not being stimulated), there’s a difference in charge
between the inside and the outside of the cell — this is generated by ion pumps and ion channels
This means that there’s a voltage across the membrane. Voltage is also known as potential difference

Question 8

what is the potential difference when the cell is at rest

Answer 8

its resting potential. When a stimulus
is detected, the cell membrane is excited and becomes more permeable, allowing more ions
to move in and out of the cell — altering the potential difference. The change in
potential difference due to a stimulus is called the generator potential.

Question 9

what does a bigger stimulus do

Answer 9

A bigger stimulus excites the membrane more, causing a bigger movement of ions and a
bigger change in potential difference — so a bigger generator potential is produced

Question 10

if a generator potential is big enough what will it trigger

Answer 10

If the generator potential is big enough it’ll trigger an action potential

Question 11

what is an action potential

Answer 11

an electrical impulse along a

neurone

Question 12

if the stimulus is too weak what will happen

Answer 12

If the stimulus is too weak the generator potential won’t re ach the threshold, so there’s no action potential.

Question 13

what is the threshold level

Answer 13

the level the generator potential must meet to trigger an action potential

(the number of action potentials triggered during a certain time period)

Question 14

why is the strength of stimulus measured by frequency of action potentials

Answer 14

Action potentials are all one size

Question 15

what are pacinian corpuscles

Answer 15

Pressure Receptors in Your Skin

Question 16

what type of receptors are pacinias corpuscles

Answer 16

Pacinian corpuscles are mechanoreceptors — they
detect mechanical stimuli, e.g. pressure and vibrations
They’re found in your skin

Question 17

what do pacinian receptors contain

Answer 17

Pacinian corpuscles contain the end of a sensory
neurone, imaginatively called a sensory nerve ending.
The sensory nerve ending is wrapped in loads of layers
of connective tissue called lamellae.

Question 18

what happens when a pacinians corpuscle is stimulated

Answer 18

W hen a Pacinian corpuscle is stimulated,
e.g. by a tap on the arm, the lamellae are
deformed and press on the sensory nerve ending.

Question 19

what do the lamellae becoming deformed and pressing on the sensory nerve ending

Answer 19

This causes the sensory neurone’s cell membrane to
stretch, deforming the stretch-mediated sodium ion
channels. The channels open and sodium ions diffuse
into the cell, creating a generator potential.

Question 20

what happens when the generator potential reaches the threshold

Answer 20

he generator potential reaches the threshold,

it triggers an action potential.

Question 21

what are photo receptors

Answer 21

Photoreceptors are Light Receptors in Your Eye

Question 22

how does light enter the eye

Answer 22

Light enters the eye through the pupil.

The amount of light that enters is controlled by the muscles of the iris

Question 23

what are light rays focused by

Answer 23

Light rays are focused by the lens onto the retina, which lines the inside
of the eye. The retina contains photoreceptor cells — these detect light.

Question 24

what is the fovea

Answer 24

The fovea is an area of the retina where there are lots of photoreceptors

Question 25

how do nerve impulses reach the brain

Answer 25

Nerve impulses from the photoreceptor cells are carried from the retina
to the brain by the op tic nerve, which is a bundle of neurones.
W here the optic nerve leaves the eye is called the blind spot —
there aren’t any photoreceptor cells, so it’s not sensitive to light.

Question 26

what are all the part of the eye

Answer 26

lens, pupil, iris, retina, fovea, blind spot, optic nerve.