Question 1

What is excitatory and inhibitory neurotransmission?

Accepted Answer

Excitatory neurotransmitters excite the post synaptic neurone for periods ranging from a few milliseconds to many seconds, producing depolarisation that may be sufficient to trigger action potentials. Some neurotransmitters have the opposite effect, they inhibit the formation of action potentials in the post synaptic neurone because the membrane potential becomes more negative when the neurotransmitter binds to the post-synaptic membrane. This hyper-polarisation makes it more difficult for the post synaptic neurone to reach the threshold potential and so nerve impulses are inhibited.

Question 2

How does neurotransmission work (6.5)?

Accepted Answer

Neurotransmitter is released into the pre-synaptic neurone when a depolarisation of the pre-synaptic neurone reaches the synapse. The neurotransmitter depolarises the post synaptic neurone by binding to receptors in its membrane.

Question 3

What are inhibitory neurotransmitters?

Accepted Answer

Small molecules that are inactivated by specific enzymes in the membrane of the post synaptic neurone.

Question 4

What is summation?

Accepted Answer

More than one pre-synaptic neurone can form a synapse with the same post-synaptic neurone. Usually a single release of excitatory neurotransmitter from one pre-synaptic neurone is insufficient to trigger an action potential. Either one pre-synaptic neurone must repeatedly release neurotransmitter, or several adjacent pre-synaptic neurones must release neurotransmitter more or less simultaneously. The additive effect from multiple releases of excitatory neurotransmitter is called summation. Some pre-synaptic neurones release an inhibitory rather than an excitatory neurotransmitter. Summation involves combining the effects of excitatory and inhibitory neurotransmitters. Whether or not action potentials form in a post-synaptic neurone depends on the balance between the effects of the synapses that release excitatory and inhibitory neurotransmitters and therefore whether the threshold potential is reached. This integration of signals from many different sources is the basis of decision-making processes in the central nervous system.

Question 5

How do fast acting neurotransmitters work?

Accepted Answer

Neurotransmitters such as acetylcholine or the ones discussed before have all been fast acting neurotransmitters. The neurotransmitter crosses the synapse and binds to the receptors less than a millisecond after an action potential has arrived at the pre-synaptic membrane. The receptors are ion channels which open or close in response to the binding of the neurotransmitter, causing an almost immediate but very brief change in the post-synaptic membrane potential

Question 6

How do slow acting neurotransmitters work?

Accepted Answer

They are either called slow acting neurotransmitters or neuromodulators which take hundreds of milliseconds to have effects on the post synaptic neurone. They may diffuse through the surrounding fluid and effect groups of neurones. Noadrenaline/norepinephrine, dopamine and serotonin are slow acting neurotransmitters. Slow acting neurotransmitters do not affect ion movement across post synaptic membranes directly, but instead cause the release of secondary messengers inside post synaptic neurones which set off sequences of intracellular processes that regulate fast synaptic transmission. Slow acting neurotransmitters can modulate fast synaptic transmission for relatively long periods of time

Question 7

What are some example of slow acting neurotransmitters?

Accepted Answer

Noadrenaline/norepinephrine, dopamine and serotonin are slow acting neurotransmitters.

Question 8

What is the difference between slow acting neurotransmitters and fast acting neurotransmitters?

Accepted Answer

Fast acting neurotransmitters go across the synapse and cause ion channels to open within milliseconds, whereas slow acting neurotransmitters take hundred of milliseconds to have an effect on the post synaptic neurone. Slow acting neurotransmitters also diffuse through the surrounding fluid and effect groups of neurones rather than just one. Fast acting neurotransmitters affect ion movement, but slow acting neurotransmitters do not they cause the release of secondary messengers inside post synaptic neurones which set off sequences of intracellular processes that regulate fast synaptic transmission. Slow acting neurotransmitters can modulate fast synaptic transmission for relatively long periods of time.

Question 9

How are memory and slow acting neurotransmitters linked?

Accepted Answer

Slow acting neurotransmitters have a role in memory and learning. They cause the release of secondary messengers inside post synaptic neurones that can promote synaptic transmission by mechanisms. Such as an increase in the number of receptors in the post synaptic membrane or chemical modification of these receptors to increase the rate of ion movements when neurotransmitter binds. The secondary messengers can persist for days and cause what is known as long-term potentiation (LTP). This may be central to the synaptic plasticity that is necessary for memory and learning. Even longer-term memories may be due to a remodelling of the synaptic connections between neurones. Basically slow acting neurotransmitters release secondary messengers which then promote that pathway. So they might add extra receptors or they might chemically modify the receptors to increase ion movement when something does bind. Therefore by making more things trigger in this pathway it is linked to learning and the plasticity of the brain.

Question 10

What are psychoactive drugs?

Accepted Answer

Psychoactive drugs affect the brain by either increasing or decreasing post synaptic transmission. Some drugs are excitatory because they increase post synaptic transmission and some are inhibitory because they decrease it. Examples of excitatory drugs: - Nicotine, contained in cigarettes. Derived from Nicotiana tabacum. - Cocaine extracted from the leaves of a Peruvian plant Erythroxylon coca. - Amphetamines, which are a group of artificially synthesised compounds. Examples of inhibitory drugs: - Benzodiazepines, a group of compounds including Valium that are synthesised artificially. - Alcohol in the form of ethanol. - Tetrahydrocannabinol (THC) obtained from the leaves of the Cannabis sativa plant.

Question 11

What are endorphins and what are they used for?

Accepted Answer

Endorphins can be used as painkillers. Pain receptors in the skin and other parts of the body detect stimuli such as the chemical substances in a bee's sting, excessive heat or the puncturing of skin. These receptors are the endings of sensory neurones that convey impulses to the CNS. When impulses reach sensory areas of the cerebral cortex we experience the sensation of pain. Endorphins are oligopeptides that are secreted by the pituitary gland and act as natural painkillers, blocking feelings of pain. They bind to receptors in synapses in the pathways used in the perception of pain, inhibiting synaptic transmission and preventing the pain being felt.

Question 12

Where are endorphins secreted?

Accepted Answer

They are secreted by the pituitary gland as natural painkillers, they block the pain receptors on synapses.

Question 13

Give 3 examples of excitatory psychoactive drugs?

Accepted Answer

Examples of excitatory drugs: - Nicotine, contained in cigarettes. Derived from Nicotiana tabacum. - Cocaine extracted from the leaves of a Peruvian plant Erythroxylon coca. - Amphetamines, which are a group of artificially synthesised compounds.

Question 14

Give 3 examples of inhibitory psychoactive drugs?

Accepted Answer

Examples of inhibitory drugs: - Benzodiazepines, a group of compounds including Valium that are synthesised artificially. - Alcohol in the form of ethanol. - Tetrahydrocannabinol (THC) obtained from the leaves of the Cannabis sativa plant.

Question 15

How do anaesthetics work?

Accepted Answer

Anaesthetics act by interfering with neural transmission between areas of sensory perception and the CNS. Anaesthetics cause a reversible loss of sensation in part or all of the body. Local anaesthetics cause an area of the body to become numb, for example the gums and teeth during a dental procedure. Anaesthetics are chemically varied and work in a variety of ways. Many of them affect more than just the sense organs and can also inhibit signals to motor neurones and other parts of the nervous system so they should only be administered by highly trained medical practitioners.

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A5 Neuropharmacology Flashcards

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