The Cells of the Nervous System and Neurotransmitters at Synapses Flashcards Preview

Higher Human Biology - Unit 3 > The Cells of the Nervous System and Neurotransmitters at Synapses > Flashcards

Flashcards in The Cells of the Nervous System and Neurotransmitters at Synapses Deck (26)
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What are the 3 types of neurons?

Sensory, Inter and Motor


What is the basic structure of a neuron?

Cells body, Axon and Dendrites


What does the cell body do?

It is the control centre as it contains a nucleus


What does the axon's do?

Its a single nerve fibre that carry's nerve impulses away from the cell body


What does dendrites do?

It passes impulses towards the cell body


What is the function of the myelin sheath?

It surrounds the axons with a layer of fatty material that insulates the axon, it greatly increases the speed of impulse conduction


What is myelination?

This is the development of myelin and continuous from birth to adolescence

*Responses to stimuli in the first 2 years of life are not as rapid or coordinated as those of an older child or adult


What do certain diseases do in relation to the myelin sheath?

They destroy it which causes a loss in coordination


What is the function of glial cells?

To produce myelin sheath and support neurons


What is the region of functional contraction?

This is between the axon ending of one neuron (pre-synaptic neuron) and a dendrite of another (postsynaptic neuron) is called a synapse with a tiny gap between them known as the synaptic cleft


How are messages relayed across the synaptic cleft?

This is done by neurotransmitters stored in vesicles on the presynaptic neuron only, such as acetylcholine and noradrenaline


What happens when an impulse passes through the presynaptic neuron?

It stimulates several vesicles to move to the synapse, fuse with the membrane and discharge the neurotransmitters which diffuse across the synaptic cleft and bind to receptors on the membrane of the synaptic neuron


To ensure precise control and prevent continuous stimulation, what has to happen?

The postsynaptic neuron must remain excited fir only a brief moment to pass on the impulse, so removal of neurotransmitters by enzyme degeneration (enzyme breaks down neurotransmitters which is then reabsorbed and synthesised into new neurotransmitter) or by reabsorption directly (to be stored in vesicles)


The receptors present on the postsynaptic neuron determine what?

Whether the signal is excitatory and inhibitory


In order for an impulse to be transmitted, what has to happen?

A certain threshold of neurotransmitter molecules must attach to receptors otherwise they are filtered out due to being weak

However, if a postsynaptic neuron were to receive information via several synapses (convergent pathway), this collective of weak stimuli could be enough to fire an impulse known as summation


What are endorphins?

They are neurotransmitters that stimulate neurons involved in reducing intensity of pain by combining with receptors synapses and blocking the transmission of the pain signal


Endorphins are produced by what?

The hypothalamus and increases levels are produced in the response to:

Severe injury
Prolonged and continuous exercise
Physical and emotional stress
Certain foods (e.g. chocolate)

Increased levels are linked with feelings of pleasure obtained from activities, such as:

Prolonged exercise


What is dopamine?

It is a neurotransmitter that induces feelings of pleasure by stimulating the reward pathway which reinforces certain behaviour to satisfy a need that is beneficial such as hunger or thirst


What is an Agonist?

It binds to and stimulates specific receptors on postsynaptic neuron mimicking action of naturally occurring neurotransmitters triggering normal cellular response


What is an Antagonist?

It binds to specific receptors om postsynaptic neuron and blocking the action of the neurotransmitter inhibiting normal cellular response


What do other drugs do (inhibitors)?

They act by preventing the removal of the neurotransmitter (by degrading the enzymes or preventing re-uptake) causing an enhanced effect


Recreational drugs act like what?

Agonists and Antagonists


What do recreational drugs do?

They affect transmission at synapses in the brain altering an individuals:

-Mood (feels happier, more confident, more aggressive)
-Cognition (cant carry out complex mental tasks such as problem solving and decision making)
-Perception (misinterpretation of stimuli)
-Behaviour (stay awake for longer, talk endlessly about themselves)


Many recreational drugs effect what?

The neurotransmitters in the reward circuit of the brain causing them to be overstimulated


What is drug addiction caused by?

Repeated use of drugs that act as antagonists. Antagonists block specific receptors causing the nervous system to compensate by increasing both the number and sensitivity of these receptors

This sensitisation leads to addiction where the individual craves more of the drug


What is drug tolerance caused by?

Repeated use of drugs that act as agonists. Agonists stimulate specific receptors causing the nervous system to compensate by decreasing both the number and sensitivity of these receptors

This desensitisation leads to drug tolerance where the individual must take more of the drug to get an effect