CO-ORDINATION AND CONTROL - responding to change
Hormones secreted by special glands are chemicals that help and control and co-ordinate processes in your body
The nervous system uses electrical impulses to enable you to react to your surroundings and co-ordinate what you do
Cells called receptors detect stimuli (changes in the environment)
Impulses from receptors pass along sensory neurones to the brain
Impulses are sent from the brain to the effector organs along motor neurones
Impulses travel between 1 and 120 metres per second
Hormones are chemical substances
Special glands make and secrete hormones
Glands making hormones :- pituitary (FSH and Oestrogen), Thyroid, Adrenal (adrenaline) Pancreas, Ovaries (Oestrogen and LH), Testes
Hormones are carried to where they are needed in the blood stream
The nervous system - the body is very sensitive to changes around us - these changes known as stimuli are picked up by cells in the body called receptors
stimuli to receptor to sensory neurone to CNS to motor neurone to effector organs
effector organs are muscles which contract or glands which secrete chemical substances.
This is summed up in this picture
Carried by nerve cells Carried in the blood stream
Very fast Not so fast
Short term effects Long term effects
Co-ordinates reactions to surroundings Internal body processes
Hormone reaction can target a number of different organs at the same time
Nerve fibres only travel to one effector organ. Of course, the brain can stimulate a number of effector organs at the same time
Some responses happen so fast that they happen before you can think. These automatic reactions are known as reflexes
Reflexes - help avoid danger, take care of basic bodily functions such as breathing or moving food through the gut
Reflex actions involve three types of neurones
- Sensory neurones
- Motor neurones
- Relay neurones - these connect sensory neurones to motor neurones and are found in the CNS
The receiving of stimuli through to the impulse being delivered to an effector organ is known as the reflex arc.
There are junctions between neurones. These are called synapses.
To pass an electrical impulse across the synapse the first neurone creates a chemical which is sent across the synapse and received in receptor cells of the next neurone and used to create the electrical impulse in this neurone
Stimulus to Sensory Receptor to Sensory Neurone across Synapse to Relay Neurone across Synapse to Motor Neurone to Effector Organ.
- Some response to stimuli are automatic and rapid and are called reflex actions
- Reflex actions run everyday bodily functions and help people avoid danger.
THE MENSTRUAL CYCLE
Hormones control the menstrual cycle
These hormones are in the brain and the ovaries
Average length 28 days - womb thickens to support developing baby - egg starts maturing in ovary - if egg is not fertilised lining of womb and egg ares shed in monthly period
All these changes are hormones…