Unit 3- Nervous System And Synapses Flashcards
What does a neuron consist of?
Dendrite, cell body, axon, myelin sheath, axon ending.
Describe the function of the myelin sheath.
Insulates the axon and increases the speed of the impulse conduction.
What is myelination?
Myelination is the development of myelin round axon fibres. It’s not complete at birth and so nervous control increase over the first 2 years.
What does myelination being incomplete cause?
Stimuli are not as rapid or coordinated.
What’s the function of glial cells?
To physically support neurons and produce the myelin sheath.
Neurons at a synapse are separated at what?
The synaptic cleft.
What stores neurotransmitters?
Vesicles.
What are examples of neurotransmitters?
Acetylcholine, noradrenaline.
Describe how an impulse affects the synapse.
Impulse causes vesicles to fuse with the presynaptic neurons membrane and release neurotransmitters into the synaptic cleft.
They diffuse across the cleft and bind to receptors on the postsynaptic membrane.
What is needed to trigger the new impulse on the postsynaptic membrane?
A minimum number of neurotransmitter molecules attached to receptors in order to reach the threshold.
How are weak stimuli filtered out?
Not enough neurotransmitter molecules reach the postsynaptic neuron.
Describe summation.
When a series of weak stimuli can release enough neurotransmitter to trigger an impulse.
What are the types of signals?
Excitatory, inhibitory.
What does an excitatory signal cause.
Contraction in muscle.
What does an inhibitory signal cause?
Reduces the rate and strength of heart muscle contraction.
How are neurotransmitters removed?
Enzyme (acetylcholine) or re-uptake (noradrenaline).
What are endorphins?
Endorphins are neurotransmitters that stimulate neurons involved in reducing the intensity of pain.
What causes increased levels of endorphins?
Eating, Sex, prolonged exercise.
What causes increased levels of endorphins production?
Severe injury, prolonged and continuous exercise, stress, certain foods.
What neurotransmitter involves the reward pathway?
Dopamine.
What does dopamine do?
Induces feelings of pleasure and rewards particular behaviour.
What are the 3 types of drug?
Agonist, antagonist, inhibitor.
What is the role of agonists?
Agonists bind to and stimulate receptors mimicking the neurotransmitter.
What is the role of antagonists?
Antagonists bind to specific receptors blocking the action of the neurotransmitter.
Describe sensitisation (drug addiction).
Caused by the repeated use of drugs that act as antagonists. This blocks specific receptors causing the nervous system to increase the number and sensitivity of these receptors. Leading to addiction.
Describe desensitisation (drug tolerance).
Drug tolerance is caused by repeated use of drugs that act as agonists. This causes the nervous system to decrease the number and sensitivity of these receptors. Leading to drug tolerance.
