Homeostasis

Question 1

What two organs make up the CNS? (central nervous system)

Answer 1

Brain and spinal cord

Question 2

Why are reflex actions important?

Answer 2

For fast reactions to ensure survival

Question 3

Why are reflexes so fast?

Answer 3

• Only 2 synapses (3 neurones)
• Unconscious action

Question 4

What is homeostasis?

Answer 4

Keeping the internal conditions of an organism constant

Question 5

What are three main conditions controlled by the body?

Answer 5

• Blood sugar
• Body temperature
• Water levels

Question 6

Describe the general pathway of a control system

Answer 6

Stimulus –> Receptor –> CNS –> Effector –> Response

Question 7

What is an effector?

Answer 7

Muscles or glands that bring about a response

Question 8

What is a receptor?

Answer 8

Cells that detect stimuli

Question 9

What is the coordination centre?

Answer 9

Areas that receive and process information (usually the CNS)

Question 10

What is a synapse?

Answer 10

A gap between two neurones, allowing impulses to cross

Question 11

What do neurones do?

Answer 11

Carry electrical impulses around the body

Question 12

Describe the structure of a neurone

Answer 12

• Dendrites (carry impulses towards the cell body)
• Axon (carries impulses away from the cell body)
• Myelin sheath (around axon to speed up impulses)

Question 13

Describe the 3 types of neurone

Answer 13

• Motor neurone
• Sensory neurone
• Relay neurone

Question 14

Compare sensory and motor neurones

Answer 14

• Sensory neurones have cell bodies on their sides, whereas motor neurones have cell bodies on the end
• Sensory neurones connect to receptors, whereas motor neurones connect to effectors
• They both have axon
• They both have myelin sheaths, etc.

Question 15

What are nodes of Ranvier?

Answer 15

Gaps along the myelin sheath, aid the transmission of impulses along the axon

Question 16

What is the cornea?

Answer 16

A clear, tough coating on the front of the eye

Question 17

What is the iris?

Answer 17

Circular muscle that controls the size of the pupil

Question 18

What is the pupil?

Answer 18

Allows light into the eye - dilates and constricts

Question 19

What is the lens?

Answer 19

Flexible structure that changes shape to focus light on the retina

Question 20

What is the retina?

Answer 20

Contains millions of rods and cones that send electrical signals when light touches them

Question 21

What is the optic nerve?

Answer 21

Carries signals from the retina to the brain

Question 22

What is the suspensory ligament?

Answer 22

Holds the lens in place

Question 23

What is the ciliary muscle?

Answer 23

Changes the thickness of the lens when focusing

Question 24

What is the sclera?

Answer 24

White outer layer of the eye, tough to protect the eye

Question 25

What does the iris (muscle) do?

Answer 25

Contracts and relaxes

Question 26

What does the pupil do?

Answer 26

Constricts and dilates

Question 27

What is the cerebellum?

Answer 27

Controls muscle activity

Question 28

What is the medulla?

Answer 28

Controls breathing + heart rate

Question 29

What is the cerebral cortex?

Answer 29

Controls conscience

Question 30

Where is the medulla?

Answer 30

Above the spinal cord

Question 31

Where is the cerebral cortex?

Answer 31

Front of brain

Question 32

Where is the cerebellum?

Answer 32

Back of brain

Question 33

How does the eye focus on a near object?

Answer 33

- Ciliary muscles contract - Suspensory ligament has low tension - Lens becomes short + wide

Question 34

How does the eye focus on a distant object?

Answer 34

- Ciliary muscles relax - Suspensory ligament has high tension - Lens becomes long + thin

Question 35

What happens to the eye in dim light?

Answer 35

- Iris relaxes - Pupil dilates

Question 36

What happens to the eye in bright light?

Answer 36

- Iris contracts - Pupil constricts

Question 37

Compare neuronal response and hormonal response

Answer 37

- Neuronal is faster than hormonal - Neuronal uses electrical impulses, hormonal uses chemicals - Impulses carried along neurones, hormones carried in bloodstream - Both help to protect the body - Both use receptors - Both require stimuli

Question 38

Where is insulin produced and what is it's function?

Answer 38

Produced in the pancreas, removes glucose from blood to be used for respiration or stored (fat + glycogen)

Question 39

Where is glucagon produced and what is it's function?

Answer 39

Produced in the pancreas, breaks down glycogen and fat back into glucose

Question 40

What is type 1 diabetes?

Answer 40

Pancreas doesn't produce insulin

Question 41

What is type 2 diabetes?

Answer 41

Body doesn't respond to insulin

Question 42

Write a method for comparing reaction times of dominant vs non-dominant hand

Answer 42

1. Have one person (Person A) hold out their dominant hand with a gap between their index finger and thumb 2. Have another person (Person B) hold a ruler vertically with the zero just above the gap in Person A's hand 3. Person B will drop the ruler and Person A will have to catch it 4. Record the measurement their thumb lands on 5. Repeat this 10 times 6. Repeat investigation using Person A's non-dominant hand

Question 43

Why is thermoregulation important?

Answer 43

So enzymes inside body don't denature

Question 44

How does the body deal with cold temperatures?

Answer 44

- Hairs stand up - Arteries vasoconstrict (move further from skin's surface to conserve heat) - Sweating reduced - Muscles contract and kinetic energy is converted to thermal energy (shivering)

Question 45

How does the body deal with hot temperatures?

Answer 45

- Hairs lie flat - Arteries vasodilate (move closer to skin's surface to lose heat faster) - Sweat released to increase evaporation

Question 46

Name three plant hormones

Answer 46

Auxins Gibberellins Ethene

Question 47

What do gibberellins do?

Answer 47

Initiates germination

Question 48

What do auxins do?

Answer 48

Increase or decrease growth (shoots vs roots)

Question 49

What does ethene do?

Answer 49

Ripens fruit Controls cell division

Question 50

What does FSH do?

Answer 50

Stimulates eggs to mature Stimulates release of oestrogen

Question 51

What does oestrogen do?

Answer 51

Stimulates the uterus lining to regrow after menstruation Stops release of FSH Stimulates release of LH

Question 52

What hormone stimulates the production of oestrogen?

Answer 52

FSH

Question 53

What does LH do?

Answer 53

Stimulates ovulation (Once ovulation has taken place, LH levels fall again)

Question 54

Where does progesterone come from?

Answer 54

The empty egg follicle after ovulation

Question 55

What does progesterone do?

Answer 55

Stops production of LH and FSH Maintains uterus lining

Question 56

What do contraceptive pills contain?

Answer 56

Oestrogen and progesterone

Question 57

How does the contraceptive pill work?

Answer 57

The oestrogen stops FSH production, meaning no eggs mature The progesterone maintains a low uterus lining, preventing implantation

Question 58

What are auxins used for in farming?

Answer 58

Rooting powder Weed killer Tissue culture growth

Question 59

What are gibberellins used for in farming?

Answer 59

Promote flowering Increase fruit size

Question 60

What is ethene used for in farming?

Answer 60

Controls ripening of fruit during transport