synapses Flashcards
1
Q
where do neurons communicate?
A
- synapses
2
Q
electrical synapses
A
– Pass electrical signals through gap junctions
- gap junctions = close communications
– Signal can be bi-directional
– Synchronizes the activity of a network of cells
3
Q
chemical synapses
A
– Use neurotransmitters that cross synaptic clefts
4
Q
neurocrines
A
– Neurotransmitters: messenger (ach, epi)
- neuromodulators: dopamine. reward system
- neurohormones: oxytocin, ADH, epi
5
Q
what are ionotropic receptors also called?
A
- receptor channels
6
Q
what are metabotropic receptors?
A
- G protein-coupled receptors for neuromodulators
7
Q
what do neurotransmitters bind to?
A
- specific receptors except NO
8
Q
nicotinic receptor
A
think skeletal muscles, autonomic neurons, CNS
9
Q
muscarinic receptor
A
- smooth and cardiac muscle endocrine and exocrine glands, CNS
10
Q
acetylcholine –> synthesis
A
- From choline (from membrane phospholipids) and acetyl CoA (from citric
acid cycle) - In axon terminals
11
Q
acetylcholine –> binds cholingeric receptors
A
- Nicotinic receptors
- On skeletal muscles and in autonomic division of PNS and CNS
- Monovalent cation channels: Na+ and K+
12
Q
acetylcholine –> muscarinic receptors
A
- In CNS and on target cells for autonomic parasympathetic division of PNS
- G protein–coupled receptors
13
Q
amines
A
- Active in the CNS
- Derived from single amino acid
– Serotonin from tryptophan
– Histamine from histidine
– Dopamine, norepinephrine & epinephrine from tyrosine
*Adrenergic/noradrenergic neurons secrete norepinephrine - Adrenergic receptors bind norepinephrine & epinephrine
– G protein–coupled receptors- alpha and beta classes
14
Q
glutamate
A
- excitatory –> CNS
- AMPA and NMDA receptors
15
Q
aspartate
A
- excitatory –> brain
- depolarizes target cells
16
Q
gamma-aminobutyric acid (GABA)
A
- inhibitory –> brain
- hyperpolarizes target cells by opening Cl- gates
17
Q
glycine and D-serine
A
- enhance the excitatory effect of glutamate
18
Q
peptides
A
- Substance P and opioid peptides (enkephalins & endorphins)
- Function as neurotransmitters, neuromodulators, neurohormones
- Cholystokinin, vasopressin, atrial natriuretic peptide
- Function as neurotransmitters and neurohormones
19
Q
purines
A
- Adenosine, AMP and ATP bind to purinergic receptors (GPCRs)
20
Q
gases diffuse in the cells
A
- NO, CO, H2S
21
Q
lipids
A
- Eicosanoids, endogenous ligands for cannabinoid receptors
22
Q
neurotransmitter release: classical model pathway
A
- Action Potential arrives at the axon terminal
- Voltage gated Ca2+ channels open in response to depolarization
- Ca2+ binds regulatory proteins and initiates exocytosis
- Neurotransmitter diffuses across synaptic cleft
- Neurotransmitter binds receptor on post-synaptic cell initiating a response
23
Q
neurotransmitter release: kiss-and-run pathway
A
- Vesicles fuse with presynaptic membrane to form fusion pore
- Neurotransmitters pass through a channel
24
Q
termination of neurotransmitter activity
A
- Diffusion away from the synaptic cleft
- Enzymatic breakdown
– Acetylcholinesterase (AChE) - Uptake into cells
– Presynaptic axon terminal
– Glial cells
25
single action potential
- results in the release of a constant amount of neurotransmitter
26
Action potentials code duration and magnitude in the frequency of action potentials produced
– Tonic activity: goes in one direction
– Burst activity: get the conduction going in all directions
27
chemical synapse
- the axon terminal contains mitochondria and synaptic vesicles filled with neurotransmitter
- the postsynaptic membrane has receptor for neurotransmitter that diffuses across the synaptic cleft
28
divergence
▪ One presynaptic neuron branches to affect a larger number of postsynaptic neurons
29
convergence
▪ Many presynaptic neurons provide input to influence a smaller number of postsynaptic neurons
30
synaptic plasticity
– A change of activity at the synapses
– Occurs primarily in CNS
– May be short-term or long-term
– May be enhance or reduce synaptic activity
31
slow synaptic potentials
- involve G-protein coupled receptors and second messengers.
– Think neuromodulators
32
fast synaptic potentials
- involve opening of ion channels.
– An excitatory postsynaptic potential (EPSP) is depolarizing. (Na+)
– An inhibitory postsynaptic potential (IPSP) is hyperpolarizing. (K+)
33
spatial summation
– Two or more neurons simultaneously fire and have an additive effect
– Postsynaptic inhibition
▪ Release of neurotransmitter is inhibitory instead of excitatory
- inhibiting movement
- based on action potential
- 2 neurons firing at the same time and they cancel each other out
34
temporal summation
- based on graded potential
– Summation occurring when graded potentials overlap in time and having an additive effect
35
synaptic activity can be modified
– Modulatory neuron terminates on the presynaptic cell and modulates the release of neurotransmitter
– Presynaptic facilitation favors the release of neurotransmitter
– Presynaptic inhibition prevents the release of neurotransmitter
36
what is glutamate a key element in?
- potentiation
- AMPA receptors and NMDA receptors
37
long term potentiation is responsible for what?
acquired behavior
38
activity at a synapse induces sustained changes in quality or quantity of connections
– Potentiation similar to facilitation
– Depression similar to inhibition
39
* Disorders of synaptic transmission are responsible for many diseases
– Parkinson’s disease, schizophrenia, and some depressions
