Cells of the Nervous System and Neurotransmitters at Synapses Flashcards
Name three structural components
of a neurone
Dendrites, cell body and axon
State the function of the
dendrite
Receive electrical impulses, either excitatory or inhibitory
State the function of the cell
body
The cell body contains the nucleus
and connects the dendrites and the
axon
State the function of the
axon
An axon carries electrical impulses
away from a cell body towards another dendrite/muscle fiber
State the pathway of an
electrical impulse through a neuron
Dendrite cell body axon
Name the structure surrounding an
axon and explain its function
A myelin sheath insulates the axon and
increases the speed of impulse conduction
Give the name of the cells that
produce the myelin sheath and
support neurons
Glial cells
At what stage does myelination occur in the body?
From birth to adolescence
Explain why responses in the first two years of life are not as rapid or coordinated as those of an older child or
adult
Myelination is incomplete, reducing the
speed of impulse conduction
Suggest an effect of diseases
that destroy the myelin sheath
The individual may experience a loss
of co-ordination
State the name given to the area
where neurons connect with other
neurones or muscle fibres
The synapse/synaptic cleft
Name the chemicals that cross
synapses
Neurotransmitters
State the function of
neurotransmitters
They relay impulses across the synapse
Describe the role of neurotransmitters on the arrival of an impulse
They are released from vesicles into the
a synaptic cleft on the arrival of an impulse
By which process do
neurotransmitters cross a
synapse?
diffusion
State what happens to
neurotransmitters after
crossing a synapse
They bind to receptors on the membrane
of post-synaptic neurons or muscle fibres
State how neurotransmitters are
removed from a synapse
By enzymes or re-uptake
Explain why neurotransmitters
are removed from a synapse
Prevent repeated stimulation of a
neuron
Name the cell structures that
determine whether a signal is
excitatory or inhibitory
Receptors
Describe how synapses can filter out
weak stimuli arising from insufficient
secretion of neurotransmitters
A minimum number of neurotransmitter molecules must attach to receptors
reach the threshold on the postsynaptic membrane
transmit the impulse.
Suggest how weak stimuli may
release enough neurotransmitter
to trigger an impulse
The summation of a series of weak
stimuli may release enough neurotransmitter to reach the threshold
State the neural pathway which
typically utilises summation
Converging
Name the neurotransmitters that
stimulate neurones involved in
reducing the intensity of pain
Endorphins
Describe how endorphin production
changes in response to severe
injury, prolonged and continuous exercise,
stress and certain foods such as chocolate
Increases
Give examples of activities, linked to the feeling of pleasure, that may account for increased levels of endorphin
Eating, sex and prolonged exercise
Name the neurotransmitter that induces feelings of pleasure and reinforces particular behaviours by activating the reward pathway in the
brain
dopamine
Give an example of a beneficial
behaviour which can activate the
reward pathway
Eating
Name the two types of drugs used
to treat neurotransmitter-related
disorders
Agonists and antagonists
Describe the function of an agonist
Bind to and stimulate specific receptors, mimicking the action of a neurotransmitter at a synapse
Describe the function of an
antagonist
Bind to and block specific receptors
therefore blocking the action of a
neurotransmitter at a synapse
Describe how drugs other than agonists or antagonists affect neurotransmitters at the synapse
inhibit enzymes that degrade neurotransmitters
ihibit reuptake of the neurotransmitter at the synapse,
- causing enhanced effect
State 4 ways recreational drugs can
affect an individual
Mood, cognition, perception or behaviour
State which neurotransmitter
pathway in the brain is often
affected by recreational drugs
Reward pathway
State how drug addiction is caused
Repeated use of drugs acting as antagonists,
block specific receptors causing the nervous
system to increase both the number and
sensitivity of the receptors
Explain why sensitisation of
receptors leads to addiction
Individual craves more drugs to bind to
the receptors
State how drug tolerance is caused
Repeated use of drugs that act as agonists stimulate specific receptors causing the nervous system to decrease both the number and sensitivity
of these receptors
Explain why desensitisation of
receptors leads to drug tolerance
An individual must take more drug to get
an effect
