The nervous system and hormones enable us to respond to external changes. They also help us to control conditions inside out bodies. THe menstual cycle is controlled by hormones.
- The nervous system enables humans to react to their surroundings and coordinate their behaviour.
- Receptors detect stimuli which include light, sound, changes in position, chemicals, touch, pressure, pain and temperature.
- Information from receptors passes along cells (neurons) in nerves to the brain. The brain coordinates the response - but not in reflex response.
- Reflex actions are automatic and rapid. THy often involve sensory, relay and motor reurons.
Internal conditions which are controlled include:
-The water content of the body -water leaves the body via the lungs when we breathe out, via the skin when we sweat, and excess water is lost via the kidneys in urine.
-The ion content of the body - Ions are lost via the skin when we sweat and excess ions are lost via the kidneys in the urine.
-Temperature - to maintain the temperature at which enzymes work best
-Blood sugar levels - to provide the cells with a constant supply of energy.
Reflex action. such as: blinking, sneezing, pupil dilation, knee jerk.
Stimulus > Sensory Neuron > Relay neuron > Motor Neuron
Between each neuron there is a gap, a synapse, neuro-transmitter passes this gap via active transport. The more frequent the stimulus, the more frequent the electrical signal and greater neuro-transmitter.
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