Section 6 - coordination and response

What is homeostasis and examples

The maintenance of a constant internal environment Examples: body water content and body tempreature

How does the CNS control responses

• when receptors in the sense organs detect a stimulus, they send electrical impulses along sensory neurone to the CNS

• the CNS sends electrical impulses to an effector along motor neurone and effector responds

• neurones transmit information using high speed electrical impulses

How does the hormonal system control responses

• hormones are chemicals released into the blood

• they are carried in the blood plasma to other parts of the body and affect particular cells (target cells)

• hormones are produced in glands and have long lasting effects

Difference between hormonal and nervous system

Nerves - very fast, act for a short time and on a precise area Hormones - slow message, act for a long time and in a general way

What does the CNS consist of

brain and spinal cord

Role of neurotransmitters at synapses

• when nerve impulse reaches the end of neurone neurotransmitters are released which diffuse across the gap

• these chemicals set off a new electrical signal in the next neurone

Structure of reflex arc

stimulus, receptor, sensory neurone, relay neurone, motor neurone, effector, response

Function of reflex arc when you touch a hot object

• impulses sent from receptors in hand along sensory neurone to CNS

• in CNS, sensory neurone passes message to relay neurone

• relay neurone relays impulse to motor neurone

• the impulse travels along motor neurone to effector (muscle)

• the effector (muscle) contracts

Function of eye focusing on near objects

• ciliary muscles contract

• suspenseful ligaments slacken

• lens becomes fat

• increases amount by which it refracts light

Function of eye focusing on distant objects

• ciliary muscles relax

• suspensory ligaments stretch

• lens goes thin

• so it refracts light by smaller amounts

What does the eye do responding to changes in light intensity

Bright light - circular muscles contract, pupil becomes smaller to let in less light so retina wont get damaged Dim light - radial muscles contract, pupils become larger to let in more light

What does the skin do when your too hot

• lots of sweat produced transfers to energy when it evaporates

• blood vessels close to surface widen called vasodilation

• hairs lie flat

What does the skin do when your too cold

• little sweat produced

• blood vessels near surface constrict (vasoconstriction)

• you shiver increasing rate of respiration which transfers energy to warm the body

• hairs stand up

Source, role and effect of adrenaline and insulin

Adrenaline - adrenal glands, readies body for 'fight or flight' response, increases heart rate, blood flow to muscles and blood sugar levels Insulin - pancreas, helps control blood sugar levels, stimulates liver to turn glucose into glycogen for storage

Source role effect of testosterone, progesterone and oestrogen

Testosterone - testes, main male sex hormone, promotes male secondary characteristics Progesterone - ovaries, supports pregnancy, maintains lining of uterus Oestrogen - ovaries, main female sex hormone, controls menstrual cycle and promotes secondary characteristics

Source role and effect of ADH

pituitary gland, Controls water content, Increases permeability of kidney tubules to water

Source, role and effect of FSH

Pituitary Gland, female sex hormone, Causes an egg to mature in an ovary

Source, role and effect of LH

Pituitary Gland, female sex hormone, stimulates release of an egg from an ovary

What happens to shoots in positive phototropic

• when shoot tip is exposed to light it gets more auxin on the side in the shade

• this makes cells grow faster on the shaded side so shoot bends towards the light

What happens to shoots in negative geotropic

• when a shoot grows sideways, gravity produces unequal distribution of auxin in tip with more auxin on the lower side

• causing lower side to grow faster bending shoot upwards

What happens to roots in positive geotropic

• root growing sideways has more auxin in lower side

• the extra auxin inhibits growth so cells on top elongate faster and root bends downwards

What happens to roots in negative phototropic

• if root becomes exposed to some light, more auxin accumulates on more shaded side

• the auxin inhibits cell elongation on shaded side so root bends downwards