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Neurones and Synapses
To communicate between receptors and effectors the body uses two main methods.
These are:
A neurone is a specialised cell that is adapted to pass electrical impulses.
Each neurone has a small diameter so many can fit into one nerve. There are 3 types of neurones
1. Sensory – carry signals from sense organs (receptors) to the brain (CNS: Central Nervous System)
2. Relay – they pass messages between neurones in the CNS.
3. Motor – carry signals from CNS to muscles (effectors)
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Neurones and Synapses
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Neurones and Synapses
Although all neurones have different shapes, they all have certain features in common:
KEY POINT: Exam questions often ask how neurones are adapted for their job.
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Neurones and Synapses
The Structure of a Neurone
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Neurones and Synapses
Sensory Neurone
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Neurones and Synapses
Motor Neurone
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Neurones and Synapses
Synapse
Each neurone does not directly end on another neurone. There is a small gap between the two neurones called a synapse. In order for an impulse to be generated in the next neurone, a chemical transmitter is released. This then diffuses across the small gap.
Many drugs work by interfering with synapses. They may block or copy the action of neurotransmitters in certain neurones.
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Cell Cycle (Life Cycle of the Cell)
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- Cell grow in size
- Increase the number of sub cellular structures such as Mitochondria and Ribosomes.
1. Growth
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1. DNA Replication + Mitosis
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DNA of each chromosome contains a large number of genes. These genes controls the development
of different characteristics such as eye colour.
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Eukaryotic cells such as animals have two copies of each chromosome which we call a pair.
One of these copies is from a mother and one from the father.
Humans have 23 pairs of Chromosomes. In total 46 Chromosomes.
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Right half is the duplicate of the left half.
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All 46 chromosomes
line up at the centre
Fibres from each
half attach to the
chromosomes
Fibres pull the
arms of chromosome
to the opposite side
of the cell called
Poles.
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Cell membrane and Cytoplasm pull apart.
3. Cell Division (Cytokinesis)
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