What are nerves?
Outside the CNS, neurons are grouped together into bundles of hundreds and thousands. These bundles are called nerves.
Describe the 3 main types of neurons.
Sensory neurons carry impulses from receptors to the CNS.
Relay neurons pass messages between neurons in the CNS.
Motor neurons carry impulses from the CNS to effector organs (muscles and glands).
What is a receptor, where are they found and what do they respond to?
The nervous system has receptors to detect stimuli.
Receptors are found in sense organs; the eye, ear, nose, tongue and skin.
Stimuli include light, sounds, chemicals, temperature changes, touch and pain.
What is the central nervous system and what does it do?
The CNS is the brain and spinal chord. It allows humans to react to their surroundings and coordinates behaviour. The brain coordinates responses.
Describe a synapse.
The junction between two neurons is a synapse. Chemical neurotransmitters diffuse the impulse across the gap.
State the main steps involved in reflex actions.
1. A receptor detects a stimulus.
2. A sensory neuron transmits the impulse to the CNS.
3. A relay neuron passes the impulse on.
4. A motor neuron is stimulated and passes impulse to effector.
5. Muscle/glands contract.
What is a reflex, why is it useful and give some examples of reflexes?
All reflexes are fast, automatic responses to stimuli. Reflexes protect us from damage.
Examples of reflexes include the knee jerk, pupil reflex, accommodation, ducking and withdrawing the hand from a hot object.
How long is the menstrual cycle?
The menstrual cycle takes 28 days, with ovulation taking place about 14 days into the cycle.
What does FSH do and where is it produced?
FSH is made by the pituitary gland and causes the egg to mature and oestrogen to be produced.
How do progesterone and oestrogen levels vary during the menstrual cycle and why?
Oestrogen levels are high in the first half of the cycle. Oestrogen prepares the wall of the uterus.
Progesterone is high in the second half of the cycle. Progesterone stops the uterus wall from breaking down.
What does the contraceptive pill contain and how does it work?
The contraceptive pill may contain oestrogen and progesterone. Some pills contain only progesterone and have less side effects.
Both prevent the production of FSH so no eggs mature.
What does oestrogen do and where is it produced?
Oestrogen is produced by the ovaries and inhibits the further production of FSH.
It stimulates the production of LH and also stimulates the womb lining to develop to receive the fertilised egg.
What does LH do and where is it produced?
LH is made by the pituitary gland and stimulates the matured egg to be released from the ovary.
What is 'fertility treatment'?
If a woman cannot produce mature eggs FSH and LH can be given.
FSH causes eggs to mature and LH stimulates ovulation.
How is water content kept the same?
Most regulation of water content is done by the kidneys, which alters the volume and concentration of urine- any excess water is lost in urine.
How is ion content controlled?
We lose ions in our sweat and urine.
How is body temperature kept the same?
The body must be kept at about 37°C otherwise enzymes would stop working properly.
We sweat and send more blood to skin to cool down.
We shiver, sweat less and send less blood to the skin to conserve heat.
How are blood sugar levels kept the same?
The level of sugar in our blood is controlled by the pancreas- insulin is released when glucose levels are too high.
How can hormones be used with plants?
Weed killers are used to kill unwanted plants.
Hormones are used to encourage roots to grow before cuttings are planted.
Some hormones encourage fruit to ripen.
Define a neuron.
A neuron is a single specialised cell that is adapted to pass electrical impulses.
What are auxins?
Auxins are plant hormones which change the rate of elongation.
Auxins are mostly made in the shoots and roots.
Auxins makes cells in shoots grow more, and cells in the roots grow less.
What is phototropism and how do different parts of a plant respond to it?
Growth in response to light.
Shoots= Positive phototropism.
Roots= Negative phototropism.
What is geotropism and how do different parts of a plant respond to it?
Growth in response to the direction of gravity.
Shoots= Negative geotropism.
Roots= Positive geotropism.
Why do some women need IVF to get pregnant and how does it work?
For some women, the Fallopian tubes are blocked so the sperm cannot get to the egg.
The solution is the give artificial FSH and LH to make eggs mature, remove the eggs and fertilise with sperm in a petri dish; the cells divide to form an embryo which is put back into the woman's uterus.
This is called In Vitro Fertilisation.
Evaluate the pro and cons of the contraceptive pill.
Pro- stops women getting pregnant, gives women a choice.
Pro- helps control population growth.
Pro- helps people in undeveloped countries from going into poverty due to high costs of children.
Con- religious objection.
Con- has to be taken regularly.
Con- mild side effects like headaches.
What is a hormone?
Chemical produced by a gland.
Chemical which controls bodily functions.
How are hormones transported to their target organs?
In the blood.
A maximum of 24% of IVF treatments result in multiple births. IVF clinics have been set a target to reduce multiple births, suggest one reason why.
Possible harm to mother/ foetus.
What is hydrotropism?
Growth in response to water: Roots grow towards moisture.
Describe the function of receptors in the skin.
Receptors respond to stimuli from the environment around us e.g: light, temperature change (1). Receptors send impulses (signals) to sensory neurons (1).