B8 The Nervous System

Question 1

Which 3 main internal conditions require regulation?

Answer 1

• Blood glucose content
• Water content
• Temperature

Question 2

Which neurones can be found in the CNS?

Answer 2

Relay neurones

Question 3

What differs a reflex action from other nervous responses?

Answer 3

The signal bypasses the brain, so the response is faster.

Question 4

How is information transmitted to and from the CNS?

Answer 4

Stimulus → Receptors → Sensory neurone → CNS → Relay neurone → Motor neurone → Effector

Question 5

What does the myelin sheath do?

Answer 5

Enables electrical impulses to travel quickly and efficiently

Question 6

What structures connect two neurones?

Answer 6

Synapses

Question 7

How do electrical impulses travel across the synapse?

Answer 7

Via neurotransmitter chemicals which diffuse across the gap and trigger impulses in the next neurone.

Question 8

Name one role of a reflex response:

Answer 8

To reduce the chance of harm/injury

Question 9

Where is the cerebral cortex?

Answer 9

On the outer layer of the brain

Question 10

What functions are controlled by the cerebral cortex?

Answer 10

Consciousness, intelligence, memory and language

Question 11

What is the cerebellum responsible for?

Answer 11

Muscle co-ordination

Question 12

List and explain 3 ways in which neuroscientists study the brain:

Answer 12

• Studying patients with brain damage
• Electrically stimulating the brain
• MRI scans

Question 13

Via which part of the eye are nervous impulses carried?

Answer 13

Optic nerve

Question 14

What is the role of the iris?

Answer 14

Controls the diameter of the pupil

Question 15

What is the name of the tough outer wall of the eye?

Answer 15

Sclera

Question 16

What is the iris reflex and why is it necessary?

Answer 16

The unconscious contraction of muscles in your iris to let more or less light into the pupil, preventing damage to the eye.

Question 17

Describe what happens in the eye in dim light:

Answer 17

The radial muscles contract and the circular muscles relax, causing the pupil to dilate.

Question 18

Explain how the eye focuses on a nearby object:

Answer 18

-Ciliary muscles contract and decrease diameter
-Thus the suspensory ligaments slacken
-Lens becomes more thick and round
-Light is refracted more
-Light focussed onto the retina.

Question 19

What 2 things are the receptor cells in the retina sensitive to?

Answer 19

Colour and light intensity

Question 20

What may cause hyperopia?

Answer 20

A misshapen lens or a shortened eyeball

Question 21

What kind of lens is used to treat myopia?

Answer 21

Concave lens

Question 22

What is a disadvantage of soft contact lenses over hard ones?

Answer 22

They carry a higher risk of infection.

Question 23

What does laser eye surgery do?

Answer 23

Change the shape of the cornea by vaporising tissue to correct vision

Question 24

What complications does laser eye surgery carry?

Answer 24

Worsened vision and infection

Question 25

What is a risk of replacement lens surgery?

Answer 25

Retinal damage

Question 26

What part of your brain receives information about body temperature?

Answer 26

Thermoregulatory centre

Question 27

Where does it receive the information from?

Answer 27

- Receptors in the TRC that detect blood temperature in the brain - Receptors in the skin that transmit information about skin temperature

Question 28

What kind of feedback system controls temperature?

Answer 28

Negative feedback system

Question 29

Explain 3 mechanisms that reduce core body temperature:

Answer 29

- Hairs on the skin lie flat- less air trapped near skin, so less insulation, meaning heat can be transferred to the environment more easily - Sweat produced- transfers energy to the environment when it evaporates - Vasodilation- skin capillaries widen- blood flow closer to skin, so energy can be transferred to the environment more easily

Question 30

How does shivering lead to an increase in body temperature?

Answer 30

Your muscles contract more, requiring more respiration which transfers energy that warms the body.

Question 31

How can glasses help correct myopia?

Answer 31

The concave lens refracts the light, so that once it passes through the lens, it can be focused on the retina instead of in front of the eye.

Question 32

Define homeostasis

Answer 32

Regulation of conditions to maintain a constant internal environment

Question 33

Define stimulus

Answer 33

Change in external environment, usually one that triggers a biological response

Question 34

Define reflex

Answer 34

Rapid, unconscious response to stimuli

Question 35

Define accommodation

Answer 35

The reflex action during which the lens changes shape to focus on near and distant objects.

Question 36

Why does body temperature increase when an organism wakes up from hibernation?

Answer 36

The increase in activity increases the rate of respiration, which in turn transfers thermal energy