Topic 6 - A-Level Biology Nervous Communication

Question 1

What is a stimulus?

Answer 1

Any change in the internal or external environment.

Question 2

What are receptors?

Answer 2

Cells or proteins on cell surface membranes that detect different stimuli.

Question 3

What are the three main types of neurones?

Answer 3

Sensory, motor and relay neurones.

Question 4

What do sensory neurones do?

Answer 4

Transmit electrical impulses from receptors to the CNS - the brain and spinal cord.

Question 5

What do motor neurones do?

Answer 5

Transmit electrical impulses from the CNS to effectors.

Question 6

What do relay neurones do?

Answer 6

Transmit electrical impulses between sensory and motor neurones.

Question 7

What occurs after the detection of a stimulus?

Answer 7

A stimulus is detected by receptor cells. An electrical impulse is sent along a sensory neurone.

Question 8

After an impulse is sent along a sensory neurone, what takes place?

Answer 8

The electrical impulse reaches the end of a neurone, where chemicals called neurotransmitters take the information to the next neurone - sending an electrical impulse.

Question 9

What does the CNS do?

Answer 9

The CNS processes the information and sends information along motor neurones to an effector.

Question 10

What is the peripheral nervous system?

Answer 10

A system made up of neurones that connect the CNS to the rest of the body.

Question 11

What are the 2 systems beneath the peripheral nervous system?

Answer 11

The somatic (conscious activities) and the autonomic (unconscious activities) nervous system.

Question 12

What are the 2 systems beneath the autonomic nervous system?

Answer 12

The sympathetic nervous system (fight or flight) and the parasympathetic nervous system (rest and digest).

Question 13

What is a simple reflex?

Answer 13

A response that is rapid and protects against damage to body tissues.

Question 14

What is an example of a simple reflex arc? How is this stimulus detected?

Answer 14

A hand touching a hot surface. Thermoreceptors in the skin detect the heat stimulus.

Question 15

What do the sensory, relay and motor neurone do after thermoreceptors detect the stimulus?

Answer 15

The sensory neurone carries impulses to the relay neurone.

The relay neurone connects to the motor neurone.

The motor neurone sends impulses to the effector (your biceps muscle).

Question 16

What happens when an electrical impulse reaches the end of a neurone?

Question 17

What does a pacinian corpuscle tell us about a receptor?

Answer 17

Receptors only respond to specific stimuli.

Question 18

What does the simulation of a receptor establish?

Answer 18

The simulation of a receptor establishes a generator potential.

Question 19

How is a generator potential established?

Answer 19

1) More sodium ions are outside of the axon than inside of it.
2) Stretch-mediated sodium ion channels open and Na+ enter the axon very quickly.
3) A generator potential is created, causing nerve impulses to pass along the sensory neurone.

Question 20

What is the pigment present in rod cells?

Answer 20

Rhodopsin.

Question 21

What are the properties of rod cells?

Answer 21

• They are sensitive and detect light at low intensities.
• They are more active in dim light.
• Only detect light intensity, not colour.

Question 22

What is the pigment present in cone cells?

Answer 22

Iodopsin.

Question 23

What are the properties of cone cells?

Answer 23

• They work best in bright light, but can detect colour.

Question 24

How many kinds of cone cells are there? What is unique to each one of them?

Answer 24

Three kinds that are sensitive to either red, blue or green wavelengths of light.

Question 25

How are cone cells connected to the optic nerve? What does this mean that the brain can do?

Answer 25

• They are connected individually to ganglion cells and then to the optic nerve.
• The brain can interpret exactly where the stimulus comes from.

Question 26

How are rod cells connected to the optic nerve? What does this mean that the brain can do?

Answer 26

• Many rods share a connection to a single ganglion cell.
• The brain is able to perceive a stimulus but cannot interpret exactly where it came from.

Question 27

What is the visual acuity like for rod and cone cells?

Answer 27

• Rod cells have low visual acuity and cone cells have low visual acuity + are less sensitive.

Question 28

Where does electrical activity start from in the cardiac cycle? What happens after this first step?

Answer 28

• Impulses start at the sinoatrial node in the wall of the right atrium.
• They reach the atrioventricular node where a short time delay happens, allowing the atria to empty completely.

Question 29

After reaching the AVN, what route does electrical activity take?

Answer 29

• The impulses pass down the bundle of His and along the Purkyne fibres, causing ventricular systole.

Question 30

After ventricular systole occurs, what happens to electrical activity?

Answer 30

• A short period of diastole occurs when the heart muscle relaxes and there is no more electrical activity unless another cardiac cycle is stimulated.

Question 31

How does the control of heart rate work?