biology - coordination and response

What do receptors do?

Detect stimuli

What are the 3 main types of neurones?

Sensory, relay, motor

What do effectors do?

Bring about a response to the stimuli

What is in the central nervous system?

The brain and spinal cord.

What happens when receptors detect a stimulus?

They send electrical impulses along the sensory neurone to the central nervous system.

Once the electrical impulses have reached the cns, what happens?

The cns sends electrical impulses to an effector along a motor neurone. This effector then responds accordingly.

Why does the nervous system bring very rapid responses?

Because the neurones transmit information using high speed electrical impulses.

The is the connection between two neurones called?

A synapse

What is a reflex?

Reflexes are automatic responses to certain stimuli

What is the job of the central nervous system?

To coordinate the response.

How do receptors communicate with effectors?

By the cns

What is needed to coordinate a response?

A stimuli, a receptor, an effector

What does the conjunctiva do?

Lubricates and protects the surface of the eye.

What is the function of the sclera?

Tough outer layer that protects the eye.

What is the role of the cornea?

Refracts (bends) light into the eye; it’s transparent and has no blood vessels.

What does the iris do?

Controls the diameter of the pupil and the amount of light entering the eye.

How does the lens help in vision?

Focuses light onto the retina.

What is the retina?

Light-sensitive layer containing rods and cones.

Light-sensitive layer containing rods and cones.

Rods: Sensitive in dim light; can’t see colour.

Cones: Detect colour; not effective in dim light.

What is the fovea?

Area of the retina with lots of cones; sharpest vision.

What is the optic nerve for?

Carries impulses from the retina to the brain.

What happens to the pupil in bright light?

Circular muscles contract, radial muscles relax → pupil gets smaller.

What happens to the pupil in dim light?

Radial muscles contract, circular muscles relax → pupil gets bigger.

What happens when looking at distant objects?

Ciliary muscle relaxes

Suspensory ligaments tighten

Lens becomes thin → refracts light less

What happens when looking at near objects?

Ciliary muscle contracts

Suspensory ligaments loosen

Lens becomes fat → refracts light more

What causes short-sightedness (myopia)?

Cornea/lens bends light too much or eyeball is too long → image focuses in front of the retina.

What causes long-sightedness (hyperopia)?

Cornea/lens doesn’t bend light enough or eyeball is too short → image focuses behind the retina.

What is being short sited?

Unable to focus on distant object

What is being long sited?

Unable to focus on near objects.

What is the effect of adrenaline?

Increases heart rate, blood flow to muscles and blood sugar levels.

Where is insulin made and what is its role?

Pancreas, helps control blood sugar levels.

What is the effect of insulin?

Stimulates the liver to turn glucose into glycogen for storage.

What is the role and effect of testosterone?

Main male sex hormone, promotes male secondary characteristics.

What is the role and effect of proestrogen?

Supports pregnancy, maintains the lining of the uterus.

What is the role and effect of oestrogen?

Main female sex hormone, controls menstrual cycle and promotes female secondary characteristics.

What is ADH made and what is it’s role?

Pituitary gland, controls water content.

What is the effect of ADH?

Increases permeability of the kidney tubes to water.

Where is FSH made and what is it’s role?

Pituitary gland, female sex hormone.

What is the effect of FSH?

Causes egg to mature in the ovary and stimulates ovary to produce oestrogen.

Where is LH made and what is it’s role?

Pituitary gland, female sex hormone.

What is the effect of LH?

Stimulates the release of an egg from the ovary.

What are the differences between nerves and hormones?

Nerves: fast message, act for a short time, act on a precise area.

Hormones: slower message, act for a long time, act in a more general way.

What is homeostasis?

The maintenance of a constant internal environment.

What is the optimum temperature for enzymes in the body?

37°C

What happens when you get too hot?

• Lots of sweat is produced, when it evaporates it transfers energy from your skin to the environment, cooling you down.

• Blood vessels close to the surface of the skin widen, vasodilation, this allows more blood to flow near the surface so more energy can be transferred to the surroundings.

• Hairs lie flat.

What happens when you get too cold?

• Very little sweat is produced.

• Blood vessels near the surface of the skin constrict, vasoconstriction, so less blood flows near to the surface and less energy is transferred to surroundings.

• Shiver, increases rate if respiration which transfers more energy to warm the body.

• Hard stand up on end to trap an insulating layer of air to keep you warm.

Why do larger organisms cool down quicker?

They have a larger surface area to volume ratio so they can gain or loose heat faster as there is more area for heat to transfer across.

Why do plants respond to stimuli?

To increase their chance of survival.

What 3 stimuli do plants respond to?

Light, predators, abiotic stress

What are auxins?

Plant hormones that control growth at the tips of shoots and roots. They move through the plant in solution.