Synapses Flashcards
(24 cards)
What are the two types of synapses?
Electrical where there’s direct physical touch
Chemical where signals are transmitted through a gap by chemical neurotransmitters
What are electrical synapses?
These synapses are locked together by gap junctions(connexons)
And allow a continuous flow of local current and action potential propagation
Found in areas of brain,eye and cillary ganglia
Allow ions to pass in between cells
What are chemical synapses?
They are synapses between neurons and neurons and other cells
Cells don’t directly touch
Impulses may or may not be propagated to the postsynaptic cells depending on the amount of neurotransmitter released abd sensitivity of the postsynaptic cell
What are the two classes of neurotransmitters?
Excitory and Inhibitory Neurotransmitters
What is the excitory neurotransmitter?
Causes depolarization of the postsynaptic membranes and promotes action potentials
What is the inhibitory neurotransmitter?
It causes hyperpolarisation of the postsynaptic membrane and suppresses the action potential
What is Cholinergic synapses?
All synapses that release Acetylcholine
All neuron to neurons synapses in the PNS
All neurograndular and neuromuscular junctions of the ANS of the parasympathetic division
All synapses with muscle skeletal fibers
What happens at Cholingeric synapse?
The Action potential arrives at the synaptic knob and now calcium ions enter the knob and trigger exocytosis causing Ach to then bind to the receptor and depolarization of the postsynaptic membrane happens Achase then breaks down Acetylcholine into Acetate and Cholinr
What is synaptic delay?
Where the delay is between 0.2-0.5 msec the delay is due to the arrival of the action potential at the synaptic knob and the effect on the postsynaptic membrane
The fewer the synapses the faster the response and it only takes 1 synapse for a reflex
What is synaptic fatigue?
This is where the synapse cannot recycle to meet the fast demands of the intense stimuli and synapse is inactive until Acetylcholine finishes
What are other important neurotransmitters other than Ach?
Norepinephrine
Gamma aminobutyric acid
Dopamine
Seratonin
What is norepinephrine?
It is a neurotransmitter found in the brain and portions of the ANs
Also has an excitory or inhibitory effect and released by the adrenergic synapse
Fight or flight NT
Also known as noradereline increases heart rate,blood sugar
What is dopamine?
It is a neurotransmitter that has an excitory or inhibitory effect
It is found in Parkinsons disease cocaine use and is a cns neurotransmitter
It increases alertness and happiness
What is gamma acidicbutyric acid
Memory impairment,sleep and muscle rekaxation it is a primary inhibitory neurotransmitter
What are neuromodulators ?
Similar to neurotransmitters
Slower to respond
Can be released into both the presynaptic or postsynaptic membrane
Effects are long term
Can be released alone or with a neurotransmitter
What are neuropeptides?
They are neuromodulators that bind to receptors and activate enzymes
What are opioid?
They are neuromodulators that bind to the same receptor as opium or morphine and relieves pain
What happens with EPSPs?
NT binds to and opens up the chemically voltage gates
Where Na and K simultaneously flow in the opposite direction
Na influx is greater that K efflux therefore net depolarization occurs
Epsps trigger the action potential and if the epsp is of threshold strength abd opens the voltage channels
What happens with the EPSP?
The neurotransmitter binds to and opens the chemically voltage gates causing a simultaneous flow of Na and K in opposite directions then the Na influx is more than the K efflux thus causing Epsp triggers the Action potential and if epsp is of threshold strength and the voltage gate opens
What happens in the IPSP?
Neurotransmitter binds and opens gates for Cl and K
Then hyperpolarisation occurs where the inside becomes more negative reduces the postsynaptic membrane to produce an action potential
What is summation?
THE presynaptic membrane recieves many neurons which can be a mixture of EPSP AND IPSP and the process of summation is adding up all the postsynaptic potentials to respond to its effects
What is temporal summation?
When a single EPSP is not enough to produce an action potential so 2 EPSP are involved in rapid succession
It’s very much time dependent
What is spatial summation?
Occurs in a divergent synapse
And it’s generated through adding two EPSP simultaneously together
Very space dependent
Why can’t epsp and ipsp summation temporally together?
Only a single synapse is involved so therefore either an inhibitory or excitory response is involved and never both
