Co-ordination & response

what is homestasis?

the maintenance of a constant internal environment

give two examples of homeostasis

body water content and body temperature

what is the order of a co-ordinated response?

stimulus —> receptor —> sensory neurone —> CNS —> motor neurone—> effector (muscle/glands) —> response

what is a stimulus?

a change in the external or internal environment

what is a receptor?

specialised cells or sense organs that detect the change or stimulus

what does the central nervous system consist of?

brain and spinal cord

what is the peripheral nervous system?

nerves that branch out from central nervous system to connect to rest of body

where are receptors found?

in sense organs

what is the benefit of homestasis?

ensures optimal conditions for enzymes and cell function

what is body temperature monitored and controlled by?

the thermoregulatory centre in the brain

what controls the body water content?

the kidneys

what is a coordination centre?

receives and processes infromation from receptors

what is an effector?

brings about responses to restore optimum levels

how is information sent through the nervous system?

through electrical impulses

what is the nervous system made up of?

nerves

how do messages travel in the nervous system?

along neurones

what is the type of effect in the nervous system?

specific (on cells)

what is the endocrine system made up of?

glands

what the type of messages in endocrine system?

chemical hormone

how do messages travel in the endocrine system?

through the bloodstream

what is the speed of the action in the endocrine system?

slower

what is a nerve made up of?

a bundle of neurones

what is the tiny gap between two neurones called?

a synapse

describe how an electrical impulse travels along two neurones

electrical impulse arrives at end of first neurone.

release neurotransmitter into synapse

diffuses across gap.

binds to receptor molecules on membrane of next neurone.

triggers a new electrical impulse in second neurone

neurotransmitter is broken down/reabsorbed

what is a reflex response?

a response that does not involve the conscious part of the brain as the coordinator

why are reflex responses automatic and rapid?

minimise damage to body and aids survival

what is a reflex arc?

a pathway taken by electrical impulses during a reflex action

A- Sclera

B-Conjunctiva

C-Iris

D-Pupil

E-Cornea

F-Lens

G-Suspensory ligaments

H-Ciliary muscle

I-Blind spot

J-Optic nerve

K-Retina

what is the cornea’s function?

transparent front layer- refracts most light onto retina

what is the function of the iris?

coloured ring of muscle - controls how much light enters by changing pupil size

what is the function of the pupil?

hole in the middle of iris where light enters

what is the function of the lens?

transparent and flexible; focuses light onto the retina

what is the function of the retina?

light sensitive layer containing rods and cones (receptors)

what is the function of the optic nerve?

carries impulses from retina to brain

what is the function of the ciliary muscles

ring of muscle that changes shape of lens

what is the function of the suspensory ligaments?

fibres that connect ciliary muscle to the lens and hold it in place

what is the function of the sclera?

tough white outer coat; protects the eye and maintains its shape

what do rods in the eyes do?

work in dim light; detect black and white only and found at edges of retina

what is the function of the cones in the eye?

work in bright light, detect colour and are concentrated in fovea

what is the order of light into the eye?

cornea—> pupil—> lens—> retina—> optic nerve

describe the lens shape on a near object

ciliary muscles contract

suspensory ligaments slacken

lens becomes thicker and curved

light is refracted more

describe the lens shape on a distant object

ciliary muscles relax

suspensory ligaments tighten

lens is pulled into a thinner, flatter shape

light is refracted less

what happens to the skin when its too hot?

sweat glands release sweat onto skin surface

water evaporates which takes heat energy from skin so body cools down

arterioles widen

more blood flows near the surface- more heat is lost by radiation

what happens to the skin when its too cold?

arterioles in skin capillaries narrow

less blood flows near surface- less heat is lost

sweating stops

shivering

where is adrenaline made?

adrenal glands

what is the function of adrenaline?

prepares body for fight or flight

where is the source of insulin?

pancreas

what is the function of insulin?

lowers blood glucose

where is testosterone made?

testes

what is the function of testosterone?

male secondary sexual characteristics and sperm production

where is oestrogen made?

ovaries

what is the function of oestrogen?

female secondary sexual characteristics, builds up uterine lining

where is progesterone made?

ovaries

what is the function of progesterone

maintains uterus lining

when is adrenaline released?

when you’re scared, stressed or excited

what is the effect of adrenaline on the body?

increases heart rate

more oxygen and glucose reach muscles for respiration

when is insulin released?

when blood glucose is too high

what is the effect of insulin?

causes liver to convert glucose into glycogen for storage

causes body cells to take up more glucose

blood glucose falls

A- Receptor cell

B- Dendron

C- Myelin sheath

D- Cell body

E- Axon

A- Dendrite

B- Cell body

C- Axon

A- Cell body

B- Nodes of ranvier

C- Schwann cells

D- Axon

why do impulses travel in one direction only?

Neurotransmitter is released only from first neurone

receptors are only on second neurone

what is a hormone?

chemical substance, produced by a gland, carried in the blood, which alters the activity of one or more specific target organs.

what happens to the eye in a bright room?

circular muscles contract

radial muscles relax

pupil gets smaller

less light enters

protect retina from damage

what happens to the eye in a dark room?

circular muscles relax

radial muscles contract

pupil gets bigger

more light enters