Chapter 17: Impulse Conduction In The Synapse Flashcards
What is the synapse
The presynaptic and prosynaptic membrane together with synaptic cleft form the synapse
What is the synaptic cleft
It’s the gap between the presynaptic membrane of the axon terminal and the post synaptic membrane of dendrite.
What happens when a neuron fires an action potential
The action potential moves towards the axon terminals which cause the vesicle containing neurotransmitter to move closer towards and attach themselves to presynaptic membrane
At point of attachment the membrane opens releasing neurotransmitter into the synaptic cleft.
The neurotransmitter mixes with the fluid outside of cell and combine with the receptors of the postsynaptic membrane
What causes a postsynaptic potential
Neurons releasing neurotransmitter that stimulates it to fire an impulse causing the next neuron to produce an action potential which is then term an postsynaptic potential.
What may occur after a neurotransmitter excites or inhibit a receptor in the receiving neuron
It may be reabsorbed by axon through re uptake.
It could diffuse away or be broken down by enzymes
It could move around in the synaptic cleft and then return to postsynaptic receptor.
When does spatial summation occur
It occurs when a postsynaptic potential is reinforced by action potential from the terminal of several axons reaching the same synapse at relatively the same time.
When does temporal summation occur
Occurs when the same axon discharges repeatedly causing the release and accumulation of move of the neurotransmitter in synaptic cleft
What is the result of spatial and temporal summation
They increase the chances of a neuron firing in the case of excitatory postsynaptic potential and reduce chances of neurons firing in the case of inhibitory postsynaptic potential
What determines whether a neurotransmitter will have an excititory or inhibitory effect
Nature of neurotransmitter
Place it acts
Quantity of neurotransmitter in relation to enzyme that destroy it
The amount of inhibitory neurotransmitter in relation to amount of excititory neurotransmitter at a certain synapse.
What are neurotransmitter and their characteristics
They are chemicals that are present or synthesised by neurons
When neuron is active a chemical is released and produces a response in a target cell.
Has a mechanism for removing the neurotransmitter from synaptic cleft once work is done
What are the functions of Acetylcholine ACh
Released by cells in the brain and spinal cord as well as parasympathetic nerves
It causes skeletal muscles to contact
Is believed to be related to memory and support normal wakeful behaviour and mental alertness.
An insufficiency of ACh in some brain areas of patients with Alzheimer’s may explain the progressive decline in cognitive functioning
What are the functions of adrenalin ( epinephrine)
Released by sympathetic nerves and adrenal glands.
Increase the heart rate and contraction of blood vessels, skeletal muscles and cardiac muscle.
Speeds up metabolism and release of glucose into blood stream.
What are the functions of noradrenalin NA known to as norepinephrine NE
Released by brain cells and sympathetic nerves and adrenal gland
It has an excititory effect
A lack of NA is associated with depression and an excess with Mania
What are the functions of dopamine DA
Associated with good mental health
An excess of DA associated with schizophrenia a mental disorder characterized by loss of contact with reality
DA is involved in control of motor behaviour. Too little can result in muscle rigidity and tremor.
An insufficiency of DA in brain contribute to Parkinson disease a form of mental disorders characterized by disturbance of movement and dementia.
What are the functions of serotonin
Found in the brain digestive tract and blood
Helps to regulate the sleep wake cycle and temperature
Associated with seasonal depression a mood disorders that occurs in autumn and winter
