What homeostasis is and why it matters, receptors coordination centres and effectors, the reflex arc, and the required practical on reaction time.
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1.Define homeostasis.
The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external change.
2.Why does the body need homeostasis?
Enzymes and cells only work properly within a narrow range of conditions, so those conditions must be kept steady.
3.Name three conditions controlled by homeostasis in humans.
Blood glucose concentration, body temperature, and water levels.
4.What are the three components of every control system?
Receptors, a coordination centre, and effectors.
5.What do receptors do?
They detect stimuli, which are changes in the environment.
6.Name three coordination centres.
The brain, the spinal cord, and the pancreas.
7.What do coordination centres do?
They receive and process information from the receptors and decide on the response.
8.What are effectors?
Muscles or glands that carry out the response, by contracting or by secreting a hormone.
9.What is the function of the nervous system?
It lets humans react to their surroundings and coordinate their behaviour.
10.What does the central nervous system consist of?
The brain and the spinal cord.
11.Describe the pathway of a nervous response.
Stimulus, receptor, sensory neurone, coordinator in the central nervous system, motor neurone, effector, response.
12.What is a synapse?
The gap between two neurones.
13.How does a signal cross a synapse?
A chemical is released, diffuses across the gap, and sets off a new electrical impulse in the next neurone.
14.Why do synapses slow the transmission of a signal?
Diffusion of the chemical across the gap is slower than an electrical impulse travelling along a neurone.
15.What is a reflex action?
An automatic and rapid response that does not involve the conscious part of the brain.
16.Why are reflex actions important?
They are fast and automatic, which protects the body from harm before you have time to think.
17.Give two examples of a reflex action.
Pulling your hand away from something hot, and the pupil narrowing in bright light.
18.Describe the reflex arc in order.
Stimulus, receptor, sensory neurone, relay neurone in the spinal cord, motor neurone, effector, response.
19.Which neurone is present in a reflex arc but not a conscious response?
The relay neurone, which allows the signal to bypass the conscious brain.
20.Why is a reflex faster than a conscious action?
The impulse does not travel to the conscious areas of the brain, so the pathway is much shorter.
21.What is the required practical on reaction time?
Dropping a ruler between the open finger and thumb of a partner, and measuring how far it falls before they catch it.
22.How is the distance converted into a reaction time?
Using a conversion table or an equation. The shorter the distance, the shorter the reaction time.
23.Name three control variables in the reaction time practical.
The same hand each time, the ruler always dropped from the same height, and no warning or countdown given.
24.Why should the test be repeated several times?
To calculate a mean, which reduces the effect of random error and any lucky catches.
25.How would you test whether caffeine affects reaction time?
Measure reaction time before and after drinking a caffeinated drink, keeping everything else the same and using the same person.
26.Why is it hard to draw firm conclusions from the caffeine test in a classroom?
The sample is small, people vary a lot, and practice at catching the ruler improves the score regardless of caffeine.
27.What is the difference between a sensory and a motor neurone?
A sensory neurone carries impulses from receptors to the central nervous system. A motor neurone carries impulses from the central nervous system to effectors.
28.Why does the body use both nervous and hormonal coordination?
Nervous responses are very fast and short lived. Hormonal responses are slower but longer lasting and act more widely.
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