Cells of the nervous system and neurotransmitters at synapses Flashcards
What is a neuron?
a specialised cell that is designed to transmit information to other nerve cells, muscle, or gland cells
What are neurons made up of?
Dendrites, the cell body and axons
What does the myelin sheath do?
it insulates the axons and increases the speed of impulse conduction.
What do glial cells do?
They produce the myelin sheath and support neurons
Describe myelination
The myelination process is vitally important to the central nervous system functioning. It continues from birth to adolescence.
How can the myelin sheath be damaged?
Some diseases destroy the myelin sheath and this causes loss of coordination.
Name an example of a disease that can do this
Multiple sclerosis
What do neurotransmitters do?
They relay impulses across the synaptic cleft
Where are neurotransmitters stored?
They are stored in vesicles in the axon endings of the pre-synaptic neuron.
Describe how neurotransmitters work
They are released into the cleft on arrival of an impulse. They diffuse across the cleft and bind to receptors on the membrane of the postsynaptic neuron.
What happens to the impulse as it goes across the synaptic cleft?
The electrical impulse changes to a chemical impulse.
What do receptors do?
They will determine whether a signal is excitatory or inhibitory.
What is an example of a receptor?
It promotes an action/production of a substance or prevents a response/inhibit production of a substance.
What can be done to prevent continuous stimulation of postsynaptic neurons?
quickly remove the neurotransmitters by enzymes or reuptake the neurotransmitters.
How do you filter the weak stimuli?
A minimum number of neurotransmitter molecules must attach to receptors in order to reach the threshold on the postsynaptic membrane to transmit the impulse. This mechanism prevents the generation of impulses from weak/harmless stimuli.
How does a series of weak stimuli trigger an impulse?
A series of weak stimuli can release enough neurotransmitter to trigger an impulse. Convergent neural pathways can release enough neurotransmitter molecules to reach threshold and trigger an impulse.
What are endorphins?
Endorphins are neurotransmitters that stimulate neurons involved in reducing the intensity of pain.
What activities increase the levels of endorphins that are linked with feelings of pleasure?
- eating
- sex
- prolonged exercise
what else increases endorphin production?
- severe injury
- prolonged and continuous exercise
- stress
- certain foods
What is dopamine?
Dopamine is a neurotransmitter that induces feelings of pleasure and reinforces particular behaviour bye activating the reward pathway of the brain.
What is involved in the reward pathway?
It involves neurons which secrete or respond to dopamine.
What are agonists?
These are chemicals that bind to and stimulate specific receptors mimicking the action of a neurotransmitter at a synapse
An example of an agonist
morphine action leading to pain relief
What are antagonists?
These are chemicals that bind to specific receptors blocking the action of a neurotransmitter at a synapse
An example of antagonists
Strychnine poisining
What do other drugs do?
They inhibit the enzymes which degrade neurotransmitters or inhibit re-uptake
An example of a drug that does this
Cocaine
