CIE IGCSE Biology Unit 14: Coordination and response

nerve impulse

an electrical signal that passes along nerve cells called neurones

human nervous system

Central nervous system: made up of two organs, spinal cord and brain

Peripheral nervous system: connected to the limbs, linked with central nervous system

voluntary actions

Requires decision making from the brain, is slower compared to involuntary action as it requires impulse to travel to brain

involuntary actions (reflex)

Does not require decision making, is fast as impulse does not require to travel to brain

Sensor, relay, and motor neurons

Sensory neurone detects stimuli and transfer impulse through sensory neurone and relay neurone in brain transfers signal to motor neurone that sends the impulse to the effector in which a response is made

simple reflex arc

receptor, sensory neurone, relay neurone,

motor neurones and effector

synapse

a junction between two neurones

How impulses travels

an impulse triggers the release of a neurotransmitter from vesicles into the synaptic gap, the neurotransmitter diffuses across to bind with receptor molecules, in the membrane of the neurone after the synaptic gap, causing the impulse to

continue

Sense organs

groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals

Eye structures

- cornea - refracts light

- iris - controls how much light enters pupil

- lens - focuses light onto retina

- retina - contains light receptors, some sensitive to light of different colours

- optic nerve - carries impulses to the brain

Blind spot

The exit point to the optic nerve with no light sensitive cells

Bright light

Circular muscle contracts

Radial muscles relax

To allow less refraction to reach the retina

pupil reflex

light intensity and antagonistic action of circular and radial muscles in the iris

accommodation to view near objects

suspensory ligaments slacken

Ciliary muscle contracts

function of rods

More conc at edge

Detects low intensity

B&w kmage

function of cones

more conc at fovea

Detect high light intensity

Provides detailed colored vision

3 types of cones

Hormones

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

endocrine glands and secretion

adrenal glands- adrenaline

pancreas-insulin

testes-testosterone

ovaries-oestrogen

adrenaline

the hormone secreted in 'fight or flight' situations and its effects, limited to increased breathing and pulse rate and widened pupils, produced by the adrenal gland above the kidney

role of the hormone adrenaline in the chemical control of metabolic activity

increasing the blood glucose concentration and pulse rate

nervous and hormonal control systems in terms of speed and longevity of action

Is slow and long lasting

homeostasis

the maintenance of a constant internal environment by the control of internal conditions within set limits

Constant body temp

Constant metabolic rate

For optimum temperature for enzymatic activity

Avoid denature of enzymes by higher temperature above optimum

Higher temperature denature of other protein molecules such as carrier protein

High temp

Skin receptors detect

Sends electric impulses thru sensory neurone

to relay neurone in brain

To motor neurone to effector

1 sweat glands - decrease sweat production so no water evaporates

2 hair erector muscle

Contracts

Hair erects

Allowing better insulation

3 skin arteriole

Arteriole constricts

Shunt vessel dilates

Decreasing blood supply to capillaries near skin to allow less heat loss by radiation

High Blood glucose

Change is detected by pancreas

Pancreas secretes insulin

Chemical message in blood

To liver, insulin stimulates to breakdown glucose to glycogen

Phototropism

To reach light for more absorption

Reach Co2 for more photosynthesis

Reach O2 for more photosynthesis

Flower accessible to pollinators

Gravitropism

To absorb water n minerals from soil

Anchor plant in soil

Shoot light

Auxin

accumulates more in shaded side

Causes cells there to absorb more water by osmosis

More cell elongation and growth

Shoot grows and bends towards the light

Positive phototropism

Root gravity

Auxin accumulates more at lower side

Cells there absorb less water by osmosis

Less cell elongation and growth

Root grows towards gravity

Positive gravitropism