nervous system

motor neurone

cns → effector

synapse

• physical gap between 2 neurones

• electronic impulse converted to chemical neurotransmitter

• diffuses across and binds to next neurone

  • slows down

stimulus

a change in environment

receptor

detects stimulus and converts info to impulse

effector

muscle/gland = contract/secrete hormone

response

response to stimulus

reflex arc

REACTION = AUTOMATIC/INVOLUNTARY

• protects person from damage

• doesn’t go to brain

• stimulus → receptor →sensory neurone → relay neurone → motor neurone → effector → response

order of nervous system

stimulus → receptor →sensory neurone → CNS→ motor neurone → effector → response

relay neurones in brain

neurone differentiation

fatty myelin sheath - insulation

long - dendrons/dendrites

cerebellum

muscle movement/coordination

cerebral cortex

consciousness, intelligence, memory and language

medulla

unconcious activity - breathing + heartbeat

hypothalmus

temperature regulation

location of cerebral cortex, medulla and cerebellum

3 ways to study brain

• mri scans (magnetic resonance imaging) - detailed picture

• electrically stimulating brain - sees what part of brain controls what

• studying patients with brain damage

why is studying brain risky

brain is complex and delicate

can lead to damage

eye in dim light

• pupil dilates

• circular muscles relax

• radial muscles contract

• more light enters eye

what is the eye

a sense organ containing receptors sensitive to light intensity + colour

what is accomodation

changing the shape of the lens to focus on near or distant objects

optic nerve

• sensory neurones that send impulses to brain

• transmits visual information from eye to brain as electrical impulses

retina

• contains light sensitive cells that send neural impulses to the brain when stimulated by light.

• thin layer of tissue that lines the back of the eye

focusing on distant objects

• ciliary muscles relax = larger diameter

• suspensory ligaments pulled tight

• lens pulled thinner = slightly refracts/less convergent

• Light focused on retina

focusing on near objects

• ciliary muscles contract = smaller diameter

• suspensory ligament loosen

• lens = thick, strongly refracts/more convergent

• light focused on retina

blind spot

• unaware of this - brain fills gap

  • point where the optic nerve leaves the eye - no retina

eye in bright light

• pupil constrics

• circular muscles contract

• radial muscles relax

• less light enters eye

pupil

• hole through which light enters the eye

• controls the amount of light that enters the eye

ciliary muscles

• controls the shape of the lens

• contract and relax to change the shape of the lens

• allows accomodation

sclera

• white outer layer

• tough + strong so the eyeball is not easily damaged

myopia

short sightedness

• close = clear

• distant = blurred

• light focused in front of retina = blurry

• concave lens

hyperopia

long sightedness

• distant = clear

• close = blurry

• light focused behind retina = blurry

• convex lens

cornea

• transparent part of sclera at from of eyeball

• lets into eye

• curved surface refracts light rays, focused on retina

iris

• circular + radial muscles that contract and relax to change the size of the pupil

• controls size of puil

• controls amount of light reaching retina

suspensory ligament

• holds lens in place

• attach the lens to ciliary muscles (helps accomodation)

corrective technology

• spectacles/contact lenses

• laser eye surgery (aters shape of cornea)

• replacement lens

lens

• clear disc held in place by suspensory ligament + ciliary muscles

• fine tunes the focusing of light rays, changing their direction to produce a clear image on retina

a - suspensory ligament

b - cornea

c - iris

d - pupil

e - sclera

f - lens

g - optic nerve

h - ciliary muscle

i - retina