3.3. The Cells of the Nervous System and Neurotransmitters at Synapses Flashcards
What are the cells in the nervous system called?
Neurons.
What do all neurons have?
Dendrites, a dendron, a cell body with a nucleus and a branched axon.
What are the three main types of neuron?
Sensory neurons, inter neurons and motor neurons.
In what direction does a nervous impulse go through a neuron?
From the dendrites to the axon.
Where are myelin sheathes found and what do they do?
They are found around the longest fibres of a neuron and they contain fatty material that insulates the fibre inside it. This helps the nervous impulse travel faster.
Give some examples of functions of glial cells.
- Provide physical support to the neuron.
- Produce myelin sheathes.
- Maintain homeostasis.
- Remove debris through phagocytosis.
What are synapses?
These are tiny gaps between neurons. Neurotransmitters travel through synapses between neurons to carry nervous impulses.
What is the process of neurotransmitters carrying a nervous impulse through a synapse?
The impulse travels down the pre-synaptic axon. Vesicles containing neurotransmitters are triggered to move towards and fuse with the pre-synaptic membrane. Neurotransmitters are then secreted from the vesicles into the synaptic cleft. Receptors found in the post-synaptic membrane recognise the neurotransmitters and the nervous impulse continues along the dendron of the new neuron.
What determines what effect a nervous impulse has?
The type of receptor determines whether a signal is excitatory or inhibitory. The strength of these excitatory and inhibitory signals determine what effect the signal has overall.
What would happen if neurotransmitters were not removed from the synaptic cleft straight after the impulse is passed on?
There would be continuous stimulation of the post-synaptic membrane and new signals would not be received.
What are the two ways of removing neurotransmitters?
Enzyme degradation- when enzymes break them down.
Re-Uptake- when they are taken back by the pre-synaptic membrane.
What effect do weak stimuli have on responses?
No effect, they are too weak to bring about a response.
What is summation?
When many weak stimuli combine to create enough strength to pass the impulse on.
What is a converging neural pathway?
When stimuli from multiply neurons converge into one neuron.
What is a diverging neural pathway?
When stimuli from one neuron divides into many neurons.
