GCSE P2 HOMEOSTASIS

Question 1

what is homeostasis?

Answer 1

maintaining a stable internal environment

Question 2

describe negative feedback cycle

Answer 2

1. receptor detects stimulus (e.g too high)
2. coordination centre receives + processes info and brings about a response
3. effector produces response which counteracts the change (level decreases)

Question 3

what does the CNS consist of?

Answer 3

the brain and spinal cord

Question 4

what are sensory neurones

Answer 4

carry electrical impulses from receptors to the CNS

Question 5

what are motor neurones

Answer 5

carry electrical impulses from the CNS to effectors

Question 6

what is an effector?

Answer 6

muscle (contracts) or a gland (secretes a hormone)

Question 7

what are synapses?

Answer 7

connection between two neurones. nerve signal transferred by chemicals which diffuse across gap - set off new electrical signal in next neurone

Question 8

what are reflexes?

Answer 8

rapid automatic responses (doesn’t involve conscious part of the brain)

Question 9

what would happen if you were stung by a bee?

Answer 9

stimulation of pain receptor
sensory neurone
relay neurone
motor neurone
muscle contracts

Question 10

what is the front part of the brain called? whats its function

Answer 10

cerebral cortex

consciousness, memory, intelligence and language

Question 11

what is the back part of the brain called?

Answer 11

cerebellum

muscle co-ordination

Question 12

what is the part of the brain called near the spinal cord?

Answer 12

medulla

unconscious activities - breathing and HR

Question 13

what is the sclera

Answer 13

tough supporting wall of the eye

Question 14

what is the cornea

Answer 14

transparent outer layer (refracts light into eye)

Question 15

what is the iris

Answer 15

contains muscles that allow it to control the diameter of the pupil

Question 16

what is the lens

Answer 16

focuses the light onto the retina

Question 17

what is the optic nerve

Answer 17

carries impulses from receptors (on retina) to the brain

Question 18

what happens when there is too much light

Answer 18

light receptors detect bright light
circular muscles contract
radial muscles relax
reduces amount of light that can enter the eye

Question 19

what happens when you look at a near object?

Answer 19

ciliary muscles contract
suspensory ligaments slacken
lens becomes more fat and curved
increases amount of light refracted

Question 20

what is changing the shape of the lens called?

Answer 20

accommodation

Question 21

what happens when you look at a far away object?

Answer 21

ciliary muscles relax
suspensory ligaments are pulled tight
lens becomes more thin and less curved
refracts light by a smaller amount

Question 22

what is long-sightedness called?

Answer 22

hyperopia (convex lens)

Question 23

what is short-sightedness called?

Answer 23

myopia (concave lens)

Question 24

contact lenses

Answer 24

lightweight + almost invisible

soft lenses could cause eye infection

Question 25

laser eye surgery

Answer 25

will correct vision | infection/eye could react badly and vision could become worse

Question 26

replacement lens surgery

Answer 26

could possibly damage the retina --> loss of sight

Question 27

what detects body temperature

Answer 27

thermoregulatory centre in the brain | receptors in the skin

Question 28

what happens when you're too hot

Answer 28

sweat produced (evaporates --> energy transferred to environment) vasodilation (blood vessels dilate moving towards surface of the skin) hair erector muscle relaxed

Question 29

what happens when you're too cold

Answer 29

hairs stand up (trap insulating layer of air) no sweat produced vasoconstriction (blood vessels constrict to close off skin's blood supply) muscles contract --> shivering --> needs respiration (transfers energy to warm body)

Question 30

what are hormones

Answer 30

chemical messengers that are sent in the blood which act on a target organ (long lasting effects)

Question 31

pituitary gland

Answer 31

master gland --> produces many hormones

Question 32

thyroid

Answer 32

thyroxine (regulates metabolism, HR and temp)

Question 33

ovaries

Answer 33

estrogen

Question 34

adrenal gland

Answer 34

adrenaline --> fight or flight

Question 35

testes

Answer 35

testosterone

Question 36

pancreas

Answer 36

insulin

Question 37

nerves

Answer 37

fast action act for short time act on precise area

Question 38

hormones

Answer 38

slower action act for long time act in a general way

Question 39

what happens when blood glucose levels are too high?

Answer 39

insulin secreted by pancreas glucose moves from blood -->liver and muscle cells insulin turns glucose to glycogen blood glucose reduced

Question 40

what happens when blood glucose levels are too low?

Answer 40

pancreas releases glucagon glucagon makes the liver turn glycogen into glucose glucose released into blood by liver blood glucose increased

Question 41

type 1 diabetes

Answer 41

pancreas produces little/no insulin

Question 42

type 2 diabetes

Answer 42

body cells don't respond to insulin

Question 43

what happens when water content is too high?

Answer 43

receptor in brain detects level is too high pituitary gland releases less ADH less water is reabsorbed from kidney tubules increased volume of urine