Topic 3 Flashcards
What is the structure of an axon?
surrounded by a myelin sheath
What is the function of the myelin sheath?
insulates the axon and increases the speed of impulse conduction from node to node.
What is the difference in myelin sheath in the first 2 years of life?
As a result responses to stimuli in the first two years of life are not as rapid or coordinated as those of an older child or adult.
What is an axon?
neural fibre that conducts impulses away from the cell body.
What is a dendrite?
neural fibre that conducts impulses from from the cell body.
What is the direction of flow of a neuron?
dendrite, cell body and axon
What is a sensory neuron?
a neuron that carries impulses into the CNS from a sense organ.
What is an inter neuron?
conducts impulses within the CNS, linking sensory and motor neurons
What is a motor neuron?
carries impulses from the CNS to muscles or glands.
What are glial cells?
Physically support neurons and produce the myelin sheath. They also maintain a homeostatic environment around the neurons
and remove debris by phagocytosis.
What is a neurotransmitter?
a chemical released into a synaptic cleft to transmit impulses to the next cell.
What do neurons connect with?
Neurons connect with other neurons,
muscle fibres and endocrine at a synaptic
clef
What is the synaptic cleft?
gap between neurons at a synapse.
What is the receptors?
protein found in the post synaptic membrane that binds neurotransmitter
What is the postsynaptic membrane?
the membrane of the neuron that contains receptors for neurotransmitters
What is the presynaptic membrane?
the membrane of the neuron that releases neurotransmitters
Why do neurotransmitters have to be removed?
The need for removal of neurotransmitters by enzymes or reuptake to prevent continuous stimulation of post-synaptic neurons.
How do neurotransmitters diffuse across the synapse?
Neurotransmitters are stored in vesicles and released into the cleft on arrival of an impulse. They diffuse across the cleft and bind to receptors on nerve endings.
What is a excitatory signal?
signal that affects a receptor and which can be passed on
What is an inhibitory signal?
signal that affects a synaptic receptor but is not passed on.
How are weak stimuli filtered out?
Synapses can filter out weak stimuli arising from insufficient secretion of neurotransmitters
What is summation?
Summation of a series of weak stimuli can trigger enough neurotransmitter to fire an impulse.
What is a converging pathway?
Converging neural pathways increase the
sensitivity to excitatory or inhibitory signals.
What is a diverging pathway?
Diverging neural pathways influence several
neurons at the same time.
What is a reverberating pathway?
Reverberating pathway neurons later in the pathway synapse with earlier ones sending the impulse back through the circuit.
What is plasticity of response?
is created when new neural pathways are developed to create new responses, bypass areas of brain damage, to suppress reflexes or responses to sensory impulses
What are endorphin’s?
Endorphins are neurotransmitters that stimulate neurons involved in reducing the intensity of pain.
What is dopamine?
Dopamine induces the feeling of pleasure and reinforces particular behaviour in the reward pathway.
What are increased levels of endorphin’s linked to?
Increased levels are also connected with euphoric feelings, appetite modulation and release of sex hormones.
When is endorphin release increased?
Endorphin production increases in response
to severe injury, prolonged and continuous
exercise, stress and certain foods.
When will the reward pathway be activated?
The reward pathway is activated on engagement of
beneficial behaviours, eg eating when
hungry.
What is the reward pathway?
The reward pathway involves neurons which secrete or respond to the neurotransmitter dopamine.
How do agonist drugs work?
Agonists bind to and stimulate receptors mimicking the neurotransmitter
How do antagonistic drugs work?
Antagonists bind to specific receptors blocking the action
of the neurotransmitter
Are drugs used to treat neurotransmitter related disorders similar or different to neurotransmitters?
similar
How do inhibitor drugs work?
Other drugs inhibit the enzymes which degrade
neurotransmitters or inhibit re-uptake.
What 4 actions can recreational drugs have?
Recreational drugs may stimulate the release of neurotransmitters, imitate their action (agonists), block their binding (antagonists), and/or inhibit their reuptake/enzymatic
degradation.
What part of the neural pathways does recreational drugs affect?
Many recreational drugs affect neurotransmission in the reward circuit of the brain.
What can changes in neurochemistry alter?
mood, cognition, perception and behaviour
What is sensitization?
Sensitisation is an increase in the number and sensitivity of neurotransmitter receptors as a result of exposure to drugs that are antagonists and leads to addiction
What is desensitization?
Desensitisation is a decrease in the number and sensitivity of receptors as a result of exposure to drugs that are agonists and leads to drug tolerance
Does sensitization or desensitization lead to drug addiction?
sensitization
