GCSE, AQA, Biology Unit 1.

Sense Organs - Eyes, Ears, Nose, Tongue and Skin.
Sensory  Neurones - Nerve cells that carry electrical impulses from receptors in sense organs to the central nervous system
Motor Neurones - Nerve cells, carry signals to the effector(muscles or glands)
Effectors - e.g muscles or glands. Both respond differently. Musvles contract. Glands secrete hormones. 

The Central Nervous System consists of the brain and spinal cord. It sends instructions to the effectors.

A stimulus can be light, sound, touch, pressure, chemical or a change in temperature or position.

Reflexes help prevent injury. 
They are automatic responses to stimuli e.g if a bright light is shined in your eye your pupils instantly get smaller so that less light gets in, therefore less damage.
The passage of info in a reflex is called a REFLEX ARC.

STIMULUS - RECEPTOR - SENSORY NEURONE - RELAY NEURONE - MOTOR NEURONE - EFFECTOR - RESPONSE

The connection between 2 neurones is called a SYNAPSE.
Nerve signal is transferred by chemicals which diffuse across the gap.
They set off a new electrical signal in the next neurone.  

HORMONES ARE CHEMICAL MESSENGERS SENT IN THE BLOOD. 

Pituitary Gland - LH, FSH and ADH (controls water content)
Pancreas - produces INSULIN for the control of BLOOD SUGAR.
Testes - TESTOSTERONE
Ovaries - OESTROGEN (controls menstrual cycle)

Both the ovaries and testes are produce hormones that are part of puberty. 

CONSISTS OF 4 STAGES 

1. Bleeding[period] starts on day 1, uterus lining breaks down.
2. The lining of the womb thickens from day 4-14. Ready to receive fertilised egg.
3. An egg is developed and released at around day 14.
4. The wall is then maintained for about 14 days until day 28. If pregnancy doesn't occur then the cycle restarts again.

FSH - pituitary gland, causes egg to mature, stimulates oestrogen production in ovaries

OESTROGEN - produced in ovaries, causes pituitary to produce LH, stops further FSH production

LH - pituitary gland, stimulates release of an egg around 14 days. 

A BALANCED DIET IS THE BEST WAY FOR A HEALTHY LIFESTYLE.
if it is not you can become malnourished (can be fat or thin), this can lead to deficiency diseases e.g lack of vitamin C causes scurvy.

If you have high proportion of muscle to fat, then you will have a higher metabolic rate and vice versa. 

Men usually have a higher metabolic rate - slightly larger, usually have more muscle

Regular exercise can boost your resting metabolic rate. 

• Is a fatty substance
• Don't want too much of it because a high cholesterol level in the blood can cause diseases like heart disease
• Transported around the body by lipoproteins 
• e.g HDLs or LDLs 
• excess LDLs can clog up arteries so is seen as bad cholesterol
• HDL is seen as good cholesterol
• Having a good balance is of LDLs and HDLs is very important. 
• Should have more HDL than LDL

SATURATED FATS RAISE CHOLESTEROL, should be eaten in moderation.
POLYUNSATURATED FATS LOWER CHOLESTEROL by increasing the removal of it from the body. 
MONOUNSATURATED FATS ARE CONSIDERED NEUTRAL, but can also help lower cholest

TOO MUCH SALT INCREASES BLOOD PRESSURE which increases risk of heart disease