U3: 20- Cells Of The Nervous System And Neurotransmitters At Synapses Flashcards
Name the two types of cell that make up the nervous system.
- nerve cells (neurons)
* glial cells
Name the three types of neuron in the body.
- sensory
- inter
- motor
What are the 3 basic parts to the neurons?
- dendrite
- cell body
- axon
What is the function of the dendrite?
Recieve nerve impulse and pass them towards the cell body
What two parts are found in the cell body of the neuron?
- cytoplasm
* nucleus
What is the function of the axon?
A single nerve fibre that carries nerve impulses away from the cell body
What name is given to the layer of fatty material that surrounds an axon?
Myelin sheath
What process lays down the myelin sheath from before birth to adolescence?
Myelination
What name is given to a nerve fibre that is lacking a myelin sheath?
Unmyelinated fibre
What is the purpose of the myelin sheath?
To greatly increase the speed at which nerve impulses pass
Name an autoimmune disease that breaks down the myelin sheath.
Multiple sclerosis
Why is a baby unable to regulate their own body temperature until they are about 6 months old?
The hypothalamus that controls temperature is not fully myelinated yet
Why are infants not able to control their full lower body until about 2 years old?
The neurons that lead to the lower body are not fully myelinated yet
What is the purpose of glial cells in the nervous system?
- physically support the neurons
* carry out myelination
What name is given to the tiny space between the axon ending of one nerve and the dendrite of the next nerve?
Synapse or synaptic cleft
What name is given to the neuron before a synapse?
Presynaptic neuron
What name is given to the neuron after a synapse?
Postsynaptic neuron
Name the type of chemical messenger relayed across the synapse from neuron to neuron.
Neurotransmitter
Name 3 neurotransmitters.
Acetylcholine, noradrenaline/norepinephrine, dopamine
What structures are found in each synaptic terminal (axon ending) that contain neurotransmitters?
Vesicles
As soon as a neurotransmitter is released from the vesicles of the axon ending in the presynaptic neuron where is it passed to?
The dendrite of the post synaptic neuron
What must happen to a neurotransmitter as soon as it is received by the postsynaptic neuron’s dendrite?
It can either be broken down by an enzyme or reabsorbed by the presynaptic neuron and stored in the vesicle for reuse
Which organelles present in the axon endings provide the energy (ATP) for the process of nerve transmission?
Mitochondria
What name is given to the critical number of neurotransmitter molecules that must be released in order for a nerve impulse to fire?
Threshold
If the critical minimum number of neurotransmitter molecules are not reached what do we call this and what happens?
Subthreshold and the nerve impulse is lost
Give an example of when subthreshold might happen.
If there is continuous low-level hum of machinery in the background it fails to evoke a response because it is a weak stimuli that does not release enough neurotransmitter. The person ignores the noise.
If one presynaptic neuron fires only a little neurotransmitter then threshold might not be reached and the nerve impulse is not transmitted. If, however, several presynaptic neurons all fire a little neurotransmitter each then the cumulative effect of all of them allow threshold to be reached and the impulse to fire along one postsynaptic neuron. What name is given to the cumulative effect of a series of neurons all bringing about an impulse?
Summation
What name is given to a complex neural pathway where several presynaptic neurons feed into one postsynaptic neuron?
Converging neural pathway
What name is given to a complex neural pathway where one presynaptic neuron feeds into several postsynaptic neurons?
Diverging neural pathway
Give an example of where a converging neural pathway is found in the body.
Rods and cones feeding into one optic nerve in the eyes
Give an example of where a diverging neural pathway is found in the body.
Fine motor control in hand when operating several fingers at once when using a pen.
Temperature control where several parts of the body are sent messages from one presynaptic nerve in the hypothalamus.
What name is given to a complex neural pathway where the axon branch from a neuron later in the pathway joins with a neuron earlier in the pathway and allows a nerve impulse to be recycled and repeatedly stimulate the presynaptic neurons?
Reverberating pathway
Name a chemical released by the brain that acts as natural painkiller and blocks the pain receptors stopping the transmission of pain signals.
Endorphins
Under what circumstances would endorphins be released?
In response to physical and emotional stress, severe injury, lengthy periods of exercise, certain foodstuffs such as chocolate
Which neurotransmitter is associated with the brain’s reward pathway and induces a pleasurable feeling?
Dopamine
What type of drug is used to treat neurotransmitter disorders where this drug mimics the action of a naturally occurring neurotransmitter?
Agonist
What type of drug is used to treat neurotransmitter disorders where this drug blocks the receptor sites on the postsynaptic neuron and prevents normal transmission of the nerve impulse?
Antagonist
What name is given to drugs that prevent the reuptake of neurotransmitter by the presynaptic neuron so they spend longer in the synapse and the persistence of this neurotransmitter causes the effect to be continued or enhanced?
Inhibitor
If Prozac (a drug for treating depression) is a drug that prevents the reuptake of the neurotransmitter serotonin and keeps it in the synapse for longer and prolongs it’s effect, what type of drug is it?
An inhibitor
Name another drug apart from Prozac that stops serotonin reuptake and acts as an inhibitor.
Ecstasy (MDMA)
What neurotransmitter is prevented from being reabsorbed by the presynaptic neuron when cocaine is used therefore enhancing it’s effect on the postsynaptic neuron?
Dopamine
What causes drug addiction where a person compulsively seeks out the drug and is incapable of resisting the urge to take it?
Repeated use of an antagonistic drug
If an antagonistic drug is repeatedly used what happens to the number of receptors on the postsynaptic neuron?
They increase in number and become more sensitive
What name is given to the process involving an increase in number and sensitivity of receptors as a result of repeated exposure to an antagonistic drug?
Sensitisation
What is a drug user said to have built up when their reaction to an addictive drug is found to have decreased in intensity with previous times even though the concentration of the drug is still the same?
Drug tolerance
What drug when overused leads to drug tolerance?
Repeated use of agonist drug
Repeated use of an agonistic drug has an effect on the receptors of a postsynaptic neuron. What effect does it cause?
The number of receptors decrease and they become less sensitive
Why do the receptors on the postsynaptic neuron being less sensitive lead to drug tolerance?
A larger dose is now needed to stimulate the reduced number of less sensitive receptors
What name is given to the process involving a decrease in number and sensitivity of receptors as a result of repeated exposure to an agonistic drug?
Desensitisation
