C10

Question 1

What is homeostasis?

Answer 1

The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes.

Question 2

What is homeostasis important for ?

Answer 2

Homeostasis is important for maintaining optimal conditions for enzyme action and all cell functions.

Question 3

What does homeostasis control?

Answer 3

In the human body, homeostasis controls the blood glucose concentration, body temperature and water levels.

Question 4

Control systems

Answer 4

The automatic control systems include nervous responses in your nervous system and chemical responses in your hormone system.

Question 5

Receptors

Answer 5

cells that detect changes in the internal or external environment, known as stimuli.

Question 6

Coordination centres

Answer 6

Areas that receive and process the information from the receptors. They send signals and coordinate the response of the body. They include the brain, spinal cord and the pancreas.

Question 7

Effectors

Answer 7

Muscles or glands that respond to the stimulus that’s been received. These responses restore conditions in the body to the optimum levels.

Question 8

Nervous system

Answer 8

The nervous system uses electrical impulses to enable you to react quickly to your surroundings and coordinate your behaviour.

Question 9

Impulses

Answer 9

Impulses from receptors pass along sensory neurons to the brain or spinal cord. The brain coordinates a response and impulses are sent along motor neurons from the brain to the effector organs.

Question 10

Effector functions

Answer 10

Your muscles respond to the arrival of impulses by contracting. Your glands respond by releasing chemical substances.
E.g - salivary glands produce and release extra saliva when you smell food
- Pancreas releases insulin when your blood sugar levels go up after a meal.

Question 11

Nervous system order

Answer 11

stimulus
receptor
coordinator
effector

Question 12

What are reflexes for ?

Answer 12

They help you avoid danger or harm because they happen so fast. Reflexes are automatic and rapid - they do not involve the conscious part of your brain.

Question 13

Neurones

Answer 13

Simple reflex actions involve three types of neurone.
- sensory neurones
- motor neurones
- relay neurones: these connect a sensory neurone and a motor neurone.

Question 14

How do reflexes work?

Answer 14

An electrical impulse passes from the receptor along the sensory neurone to the CNS. It then passes along a relay neurone and straight back to the motor neurone. From there the impulse arrives at the effector organ.

Question 15

How do synapses work?

Answer 15

Your neurones are not joined up directly to each other. There are junctions between them called synapses which form gaps between the neurones. The electrical impulse has to cross this. The diffusion of the chemical across the synapse is slower than the electrical impulse in the neurones, so its possible to cross the gap.

Question 16

The structure of the brain

Answer 16

cerebral cortex - is concerned with consciousness, intelligence, memory and language.
cerebellum - is concerned with coordinating muscular activity and balance.
medulla - is concerned with unconscious activities, such as controlling the heartbeat, the movements of the gut and breathing

Question 17

MIR

Answer 17

Scientists map regions of the brain to their functions by studying patients with brain damage, by electrically stimulating different areas of the brain.

Question 18

cornea

Answer 18

where light refracts into the eye

Question 19

lens

Answer 19

focuses light rays onto the retina

Question 20

pupil

Answer 20

hole in the centre of the iris that allows light to pass through

Question 21

iris

Answer 21

has sets of muscles that control the size of the pupil and the amount of light reaching the retina

Question 22

retina

Answer 22

where light sensitive receptor cells are found

Question 23

optic nerve

Answer 23

carries impulses from the retina to the brain

Question 24

ciliary body

Answer 24

secretes fluid that supports the front of the eye

Question 25

suspensory ligaments

Answer 25

change the shape of the lens to focus light rays on the retina

Question 26

ciliary muscle

Answer 26

changes the shape of the lens to focus light rays on the retina

Question 27

colour blindness

Answer 27

a defect that affects the cones

Question 28

cones

Answer 28

receptor cells in the retina that perceive colour

Question 29

rods

Answer 29

receptor cells in the retina that perceive black and white and allow us to see in the dark

Question 30

energy conversion by receptor cells

Answer 30

receptor cells convert light energy into the electrical energy of a nerve impulses

Question 31

seeing in the dark

Answer 31

the radial muscles contract and the pupil becomes larger to allow more light in

Question 32

seeing in light

Answer 32

the circular muscles contract and the pupil becomes smaller to allow less light in

Question 33

refraction

Answer 33

the bending of light rays as they travel from one medium to another

Question 34

focusing an image

Answer 34

first the cornea refracts light rays towards the lens then the lens refracts the light ray even more then an image is focused on the retina and the optic nerve carries impulses from the retina to the brain

Question 35

focusing long distance objects

Answer 35

the light rays are almost parallel so the lens doesn’t have to do much

Question 36

focusing short distance objects

Answer 36

because the light rays diverge the lens changes shape and becomes thicker

Question 37

accommodation

Answer 37

the ability of the eye to change shape

Question 38

accommodation of near objects

Answer 38

first the ciliary muscles contract then the suspensory ligaments loosen the lens gets thicker and the light rays are refracted strongly

Question 39

accommodation of distant objects

Answer 39

first the ciliary muscles relax then the suspensory ligaments contract the lens gets thinner and the light rays are refracted less strongly

Question 40

short-sightedness (myopia)

Answer 40

when a person can see objects at short distances but not at long distances because either the eyeball is too long for the strength of the lens or the cornea is too sharply curved. this can be fixed by a concave lens

Question 41

long-sightedness (hyperopia)

Answer 41

when a person can see objects at long distances but not at short distances because either the eyeball is too short or the cornea is not curved enough. this can be fixed by a convex lens

Question 42

eye technologies

Answer 42

contact lens correct refractive error. they are permeable to allow oxygen to reach the cornea

laser eye surgery corrects the shape of the cornea