Nervous System ( Synapse) Flashcards
What happens at the Synapse of the neuron?
- where signals molecules are secreted by neurons
- is the target cell receptors for signal molecules
- is the anatomical connection between neurons and their targets
What are the 2 parts of a synapse?
1) presynaptic neuron
2) postsynaptic neuron
What are the types of Neurotransmitters? (5)
1) acetylcholine (ACh)
2) Serotonin (5-HT)
3) Dopamine
4) Norepinephrine (NE)
5) epinephrine (E)
What is acetylcholine synthesized from?
- choline (found in the membrane phospholipids)
- Acetyl Coenzyme A/ acetyl CoA (metabolic intermediate that links glycolysis to the citric acid cycle)
Neurons that secrete acetylcholine and receptors that bind to ACh are described as?
Cholinergic
Cholinergic receptors are divided into what 2 main subtypes?
1) Cholinergic Nicotinic receptors
2) Cholinergic muscarinic receptors
Where are Cholinergic nicotinic receptors found?
- skeletal muscles
- ANS
- CNS
Where are Cholinergic Muscarinic receptors found?
- smooth and cardiac muscles
- endocrine and exocrine glands
- CNS
Which neurotransmitters are amine acid derived?
- serotonin
- dopamine
- norepinephrine/epinephrine
Serotonin is derived from what amino acid?
Tryptophan
Where is serotonin found?
and what are the neurons that secrete serotonin called?
- CNS
- serotonergic receptors
Dopamine is derived from what amino acid?
Tyrosine
Neurons that secrete dopamine are called?
Dopamine receptors
Norepinephrine (NE)/Epinephine (E) is derived from what amino acid?
-tyrosine
Neurons that secrete norepinephrine and epinephrine are called?
-adrenergic (alpha,beta)
Where are adrenergic (epinephrine,norepinephrine) receptors found?
- smooth and cardiac muscles
- CNS
- exocrine and endocrine glands
Summarize the release of neurotransimitters to the synaptic cleft
-neurotransimitters in the axon terminal are stored in vesicles, so their release in the synaptic cleft takes place by exocytosis
Explain the release steps of neurotransmitters into the postsynaptic cleft in detail (5 steps)
1) action potential depolarizes the axon terminal
2) the depolarization opens the Ca2+ channels and Ca2+ enters the cell
3) Calcium entry triggers exocytosis of synaptic vesicle contents
4) Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cleft
5) Neurotransmitter binding initiates response in the postsynaptic cleft
Summarize the neurotransmitter termination process
1) Neurotransmitters can be returned to axon terminals for reuse or transported into glial cells
2) Enzymes inactivated neurotransmitters (degradation)
3) Neurotransmitters can diffuse out of the synaptic cleft
Summarize the degradation process of neurotransmitters
-neurotransmitters that didn’t diffuse away from the synapse are inactivated by enzymes in the synaptic cleft
Describe the step by step degradation process of Acetylcholine (ACh)
1) acetylcholine is made of choline and acetyl CoA
2) In the synaptic cleft, ACh is rapidly broken down by the enzyme acetylcholinesterase
3) Choline is transported back into the axon terminal by cotransport with Na+
4) Recycled choline is used to make more ACh
What are the 2 post synaptic responses
1) excitatory postsynaptic potential
2) inhibitory postsynaptic potential
What happens to the postsynaptic cell when it receives an Excitatory postsynaptic potential (EPSP)?
-depolarizes the postsynaptic cell
What happens to the postsynaptic cell when it receives an Inhibitory postsynaptic potential (IPSP)?
-hyperpolarizes postsynaptic cell
Describe Spatial Summation
-summation of several subthreshold signals results in an action potential
Summarize the process of Synaptic Inhibition
-One inhibitory postsynaptic potential (IPSP) sums with two excitatory postsynaptic potentials (EPSPs) to prevent an action potential in the postsynaptic cell
Steps of a synaptic inhibition
1) One inhibitory and two excitatory neurons fire
2) The summed potentials are below threshold, so no action potential is generatede
Summarize a global presynaptic inhibition
-all targets of the postsynaptic neuron are inhibited equally
What are the steps of global presynaptic inhibition
1) Excitatory and inhibitory presynaptic neurons fire
2) Summed signal in postsynaptic neuron is below threshold
3) No action potential initiated at trigger zone
4) No response occurs in any target cell
Describe temporal summation
-occurs when two graded potentials from one presynaptic neuron occur close together in time
In a temporal summation, describe what happens when their is no summation
-two subthreshold graded potentials will not initiate an action potential if there are far apart in time
In a temporal summation, describe what happens during a summation that causes an action potential
-two subthreshold potentials arrive at the trigger zone within a shower period of time, they may sum and initiate an action potential
