GCSE AQA BIOLOGY B1 REVISION NOTES

Coordination and control

Responding to change:

• The nervous system enables humans to react to their surroundings and coordinate their behaviour,
• Receptors detect stimuli (eg. light, sound, touch, temperature).
• Glands produce hormones.
• Hormones are chemical messangers which are transported in the bloodstream.
• Hormones reach their target organs by being transported in the bloodstream.
• Impulses travel as electrical along neurones (nevrve cells) and chemical across synapses in the nervous system.
• 

Reflex actions:

• Reflex actions are automatic and rapid.
• Often involve sensory,relay and motor neurones.
• The gap between two neurones is called a synapse.
• Chemicals transmit across the synapse.
• Reflex actions do not involve the brain.

Steps in a reflex action:

1. A receptor detects a stimuli.

2. A sensory neurone transmits the impulse to a relay neurone.

3. The relay neurone passes the impulse on to the correct motor neurone.

4. The motor neurone passes the impulse to the effectot (muscle or gland).

5. Action is taken or a response.

The menstrual cycle:

• Cycle lasts around 28 days in most women.
• Controlled by 3 hormones.

1. Follicle Stimulating Hormone (FSH):

• Produced by the pituitary…