homeostasis

Question 1

what is a stimulus

Answer 1

change in an animals surroundings

Question 2

what is a receptor

Answer 2

the organ which detects the change

Question 3

what is an effector

Answer 3

muscles are the effectors and they contract

Question 4

what is the CNS

Answer 4

the central nervous system- consists of the brain and the spinal cord and it coordinates all the nervous responses such as moving or reflexes

Question 5

what are the three types of neurones

Answer 5

sensory, relay and motor

Question 6

what is the order of events of an impulse sent from a receptor to the effector

Answer 6

• impulses from the receptor are sent along the sensory neurone
• sent to the CNS
  impulse is passed to relay neurones in the CNS
• impulse is then passed along the effector via the motor neurone

Question 7

what is the dendrite

Answer 7

tree like projections which connect to different neurones

Question 8

what is the axon

Answer 8

long section, electrical impulses travel long distances through this axon

Question 9

myelin sheath

Answer 9

insulates axon and speeds up the transmission of impulse

Question 10

what is a reflex

Answer 10

automated actions which do not involve the brain, fast actions which involve the three neurones

Question 11

what is a synapse

Answer 11

a gap between two neurones where the electrical impulse diffuses across

Question 12

what is the cornea

Answer 12

a curved transparent disc at the front of the eye and does most of the focusing

Question 13

what is the pupil

Answer 13

a circular opening whose size is controlled by the iris

Question 14

what is the iris

Answer 14

a ring of muscle with a hole in the middle. The iris controls how much light enters the eye

Question 15

what is the lens

Answer 15

soft flexible and transparent. shape can be changed to fine tune the focusing of light onto the retina

Question 16

what are the ciliary muscles

Answer 16

a ring of muscle at the edge of the eye which circles the lens. when it contracts the lens gets fatter. when it relaxes the lens gets thinner

Question 17

what are the suspensory ligaments

Answer 17

strong fibres which attach the lens to the ciliary muscles

Question 18

what is the retina

Answer 18

contains light sensitive cells called rods and cones

Question 19

what is the optic nerve

Answer 19

consists of many neurones which carry impulses from the retina to the brain

Question 20

what is the fovea

Answer 20

the region of the retina with the greatest number of cones

Question 21

what is the conjuntiva

Answer 21

a mucous membrane that covers the eye to prevent infection

Question 22

describe what happens when you look into bright light

Answer 22

• circular muscles contract
• radial muscles relax
• iris becomes wider
• pupil constricts

Question 23

describe what happens when you look into dim light

Answer 23

• radial muscles contract
• circular muscles relax
• iris becomes wider
• pupil dilates

Question 24

describe what happens when you focus on a far away object

Answer 24

• ciliary muscles relax
• suspensory ligaments are pulled tight
• lens is pulled thin and has a less convex shape
• less refraction of light

Question 25

describe what happens when you focus on a nearby object

Answer 25

- ciliary muscles contract - suspensory ligaments relax - lens is not stretched - more refraction of light

Question 26

how does hair standing on end help when you are cold

Answer 26

hair traps layer of air which provides insulation for conduction for heat

Question 27

how does less sweating help when you are cold

Answer 27

less sweat is released therefore less heat loss via evaporation

Question 28

how does constricting the capillaries help when you are cold

Answer 28

arterioles supplying the capillaries near the surface of the skin get narrower. Less blood will flow through capillaries near the surface of the skin therefore less heat will be lost by radiation

Question 29

how does hair lying flat help when you are too hot

Answer 29

hair lying flat makes sure an insulating layer of air is not formed

Question 30

how does sweating help when you are too hot ( vasoconstriction )

Answer 30

when sweat is evaporated heat energy is taken away from the skin as evaporation of water requires energy

Question 31

how does widening the arterioles help when you are too hot ( vasodilation)

Answer 31

arterioles supplying the capillaries near the surface of the skin get wider. More blood will through capillaries near the surface of skin therefore more heat will be lost by radiation

Question 32

what is osmoregulation

Answer 32

the regulation of water levels within the body to keep rising or falling too much

Question 33

what happens when your water levels are low

Answer 33

- water levels are detected by the hypothalamus in the brain - more ADH is sent from the pituitary gland - ADH makes the collecting duct in the nephron more permeable - more water is reabsorbed back into the body

Question 34

what is positive phototropism

Answer 34

growth towards the light

Question 35

negative phototropism

Answer 35

growth away from the light

Question 36

positive geotropism

Answer 36

growth downwards with gravity

Question 37

negative geotropism

Answer 37

growth upwards against gravity

Question 38

what happens when light is shone on the plant from one side

Answer 38

- auxins are produced in the tip of the plant - auxins diffuse to the shady side of the plant so they don’t get destroyed - the auxins cause the cells on the shady side of the plant to elongate more - this results in the plant to grow and bend towards the light

Question 39

what is a hormone

Answer 39

a chemical messanger that are made in the glands

Question 40

How are hormones transported

Answer 40

in the bloodstream in the plasma

Question 41

What is ADH

Answer 41

increases permeability of collecting duct in the nephron so more water reabsorption into the blood

Question 42

Where is ADH released from

Answer 42

pituitary gland

Question 43

what is the ADH target organ

Answer 43

Kidney

Question 44

What is Insulin

Answer 44

convert glucose to glycogen lowers blood sugar levels

Question 45

Where is Insulin released from

Answer 45

the pancreas

Question 46

What is the target organ for insulin

Answer 46

Liver

Question 47

What is Adrenaline

Answer 47

triggers fight or flight response by making heart beat faster

Question 48

Where is Adrenaline released from

Answer 48

adrenal gland

Question 49

What is the target organ for adrenaline

Answer 49

heart / liver

Question 50

Descriptions of the endocrine ( hormone ) system - speed - length of response - how it travels - signal made of - target

Answer 50

- slow - long term response - in the blood plasma - chemical - all around the body

Question 51

descriptions of the nervous system - speed - length of response - how it travels - signal made of - target

Answer 51

- fast - short term response - diffusion, along neurones - electrical impulse - specific area

Question 52

What is an Auxin

Answer 52

plant growth substance

Question 53

How do auxins work

Answer 53

- diffuse to other parts of roots or shoots - change the rate of elongation in plant cells

Question 54

How does the plant growth change when light is being shone on one side of it

Answer 54

- sunlight destroys auxins so they diffuse away from the light - auxins cause elongation on the shady side of the plant causing shoot to bend towards the light

Question 55

what is positive phototropism

Answer 55

shoot grows towards light source

Question 56

what is negative phototropism

Answer 56

shoot grows away from light source

Question 57

what is positive geotropism

Answer 57

roots grow towards gravity

Question 58

what is negative geotropism

Answer 58

roots grow away from gravity

Question 59

how does geotropisms ( auxins in the roots ) work

Answer 59

- auxins inhibit cell growth - auxins gather at the bottom of the root because of gravity - slows cell growth so root bends down