10-page document of notes required to know for GCSE Biology. This resources comes from a grade 9 biology student and contains information including:
- The Human Nervous System
- The Eye
- Myopia
- Hyperopia
- Reaction Time Required Practical
- The Brain
- Homeostasis
- Kidneys
- Maintain...
How does the human nervous system coordinate a response?
Homeostasis consists of the maintaining of certain conditions within the human body and
ensuring these conditions are at an optimum for the work of enzymes as well as all cell
functions. There are many conditions which are required to be controlled, these are things
such as:
Body temperature
Blood glucose levels
Water levels
These conditions are maintained through the CNS, an abbreviation for the central nervous
system. The CNS consists of the brain and the spinal cord. The nervous system also
consists of the peripheral nervous system where nerve cells carry information to or from the
CNS.
The way in which homeostasis is controlled is through an automated control system, all
automated control systems consist of a stimulus, a receptor, a coordination centre, an
effector and a response.
The way in which the control system works is by first, the receptors detect a stimulus and
send electrical impulses down neurones and to the central nervous system.
These neurones are nerve cells. The CNS is the coordination centre, this now sends
electrical impulses down other neurones to the effectors and these effects bring about a
response.
Effectors are usually a muscle which contracts or a gland which secretes a hormone.
A key role of the nervous system is that it enables humans to react to their surroundings and
coordinate their behaviour. One way in which this is done is through the reflex arc.
Example - touching a hot object.
When touching a hot object, first the stimulus is detected by the receptor. The stimulus is
heat and the receptor is in the skin.
Electrical impulses now pass from the receptor along the sensory neurone to the CNS. At
the end of the sensory neurone there is a junction which is called the synapse and here a
chemical is released and this chemical diffuses across to the relay neurone in the CNS
where it triggers an electrical impulse.
The electrical impulse now passes across the relay neurone and reaches another synapse,
and once again a chemical is released. This chemical which is released now triggers an
electrical impulse in a motor neurone. The electrical impulse now travels down the motor
neurone to an effector and in this case the effector is a muscle.
, The muscle now contracts and pulls the hand away from the heat, pulling the hand away
from the heat is called a response.
In most cases the brain makes the decisions about what action to take when we are in a
certain situation. However, this is not always the case and in the case of reflex actions there
is no decision making by the conscious part of the brain, this makes reflexes automatic and
rapid. Due to the fact that they are rapid, reflexes help to protect us from danger.
Required practical: Reaction time.
1. Work with a partner
2. Person one holds out their hand with a gap between their thumb and first finger.
3. Person 2 holds out a ruler at the top of person ones thumb.
4. Person 2 drops the ruler and person 1 attempts to catch the ruler after it has been
dropped as quickly as they possibly can.
5. Record the number on the ruler at the top of person ones thumb and repeat this 10
times
6. Swap with person two, repeat the previous steps and calculate a mean of the lengths
on the ruler to work out who has the quickest reaction time.
7. The person with the lowest mean has the quickest reaction time.
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