homeostasis 🧠

what does the human nervous system consist of

1. central nervous system

2. peripheral nervous system

what is the central nervous system

the brain and spinal chord

what is the peripheral nervous system consist of

all the nerves in the body

what does the nervous system enable

humans to react to their surroundings and to coordinate their behaviours

what is a bundle of neurones known as

a nerve

adaptions of the nervous system

1. neurones have a cell body

2. some have axons over a metre

3. axons insulated by fatty myelin sheath with small uninsulated sections

what does the receptor detect

stimuli in the environment

what is the order of the pathway through the nervous system

stimulus - receptor - coordinator - effector - response

describe the nervous system

1. very fast

2. precise electrical impulses through nerves

3. responds quickly

4. faster

describe the endocrine system

1. relies on hormones

2. travel throughout entire body

3. only affects certain cells

4. longer lasting

5. more generalised

what is negative feedback

whenever the levels of something get too high they’re brought back down, and vice verse

what does an involuntary response not involve

the conscious part of the brain as the coordinator of the reaction

the process for reflexes

1. stimulus is detected by a receptor

2. sensory neurone sends electrical impulses to the spinal cord

3. passed to a relay neurone in the spinal chord

4. a relay neurone synapses with a motor neurone

5. a motor neurone carries an impulse to a muscle

6. muscle will contract

what are the three main types of neurones in a reflex arc

1. sensory

2. relay

3. motor

what do sensory neurons do

carry impulses from sense organs to the cns

what do relay neurones do

found inside the CNS and connect sensory and motor neurones

what do motor neurones do

carry impulses from the CNS to effectors

describe a sensory neurone

1. long

2. have a cell body branching off the middle of an axon

describe a relay neurone

1. short

2. have a small cell body at one end with many dendrites

describe a motor neurone

1. long

2. have a large cell body at one end

3. long dendrites branching off it

what are neurones separated by

synapses

how small are synaptic junctions

10nm in size

what chemicals are released into the synaptic cleft and diffuse across it

neurotransmitters

what is reaction time

time taken to respond to a stimulus

what can reaction time be affected by

1. age

2. stress

3. drugs

describe the cerebral cortex

• the outer layer of the brain

• divided into two hemispheres

• highly folded

what is the cerebral cortex responsible for

1. intelligence

2. memory

3. consciousness

4. personality

describe the cerebellum

underneath the cerebral cortex

what is the cerebellum responsible for

balance, muscle coordination and movement

describe the medulla

region that controls unconscious activities such as heart rate and breathing

describe the eye

• s a sense organ containing receptors

• sensitive to light intensity and colour

purpose of the eye

1. receive light and focus it onto the retina

2. adaption to bright or dim light

3. accommodation to focus on objects

function of the retina

controls the light receptor cells that detect light intensity and colour of light

function of the optic nerve

sensory neurone that carries electrical impulses from the eye to the brain

function of the sclera

the white layer of the eye that covers the eyeball

function of the cornea

transparent covering of the front of the eye that refracts light

function of the iris

controls how much light enters the pupils

function of the ciliary muscles

ring of muscles around the lens which relaxes and contracts to change the shape of the lens

function of the suspensory ligaments

work with the ciliary muscles to change the shape of the lens

function of the lens

transparent disc that changes shape to focus light onto the retina

what does the eye do when dim light

pupil dilates so more light can enter

what does the eye do when bright light

pupil constricts so less light enters