Neurobiology and Immunology: The Cells of the Nervous System and Neurotransmitters at Synapses
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Neurons are what?
Nerve cells
Neurons have what?
A cell body and fibres called dendrites and axons
Axons are surrounded by what? What does this do?
Myelin Sheath. It insulates the axon and increases the speed of impulse conduction.
Myelination continues from when to when?
Birth to adolescence
Response to stimuli in the first two years of life are what?
Not as rapid or coordinated as those of an older child or adult
Certain diseases can do what?
Destroy the myelin sheath causing a loss of coordination
Glial cells produce and do what?
Myelin sheath. Physically support Neurons.
Synapses are what?
Gaps between neurons
Neurons connect with other neurons or muscle fibres where?
At a synapse
Neurotransmitters relay impulses across what?
The synaptic cleft
Where are neurotransmitters stored?
In synaptic vesicles in the axon endings of the pre-synaptic neuron
Neurotransmitters do what on arrival of an electrical impulse?
Are released into the synaptic cleft
Neurotransmitters do what next?
Diffuse across the synaptic cleft and bind to receptors on the membrane of the post-synaptic neuron
What happens to neurotransmitters after diffusion?
They are removed by enzymes or reuptake to prevent continuous stimulation of post-synaptic neurons
Receptors do what?
Determine whether the signal is excitatory or inhibitory
Synapses can do what?
Filter out weak stimuli arising from insufficient secretion of neurotransmitters
A minimum number of neurotransmitter molecules must attach to receptors in order to reach the threshold on the post-synaptic membrane in order for what to happen?
An impulse to be transmitted
What can release enough neurotransmitter to trigger an impulse?
Summation of a series of weak stimuli
Converging neural pathways can do what?
Release enough neurotransmitter molecules to reach threshold and trigger an impulse
What are endorphins?
Neurotransmitters that stimulate neurons involved in reducing the intensity of pain
Endorphins production increases in response to what?
Severe injury, prolonged and continuous exercise, stress and certain foods
Increased levels of endorphins are also linked to what?
The feelings of pleasure obtained from activities such as eating, sex and prolonged exercise
What is dopamine?
It is a neurotransmitter that induces feelings of pleasure and reinforces particular behaviour by activating the reward pathway in the brain
What does the reward pathway involve?
Neurons which secrete or respond to dopamine