-
What is a synapse?
Functional association of a neuron with another neuron or with effector organs.
-
What are the types of Synapses?
-
What are electrical synapses?
Two neurons linked together by gap junctions, some are between neurons and glial cells.
-
What is the function of electrical synapses?
- Rapid communication
- Bidirectional communication
- Excitation and inhibition at same synapses
-
What are the components of a Synapses
- Presynaptic neuron
- Postsynaptic neuron
- Synaptic cleft
-
What are the different neron-to-neuron synapses?
- Axodendritic
- Axosomatic
- Axoaxonic
-
What are the anatomical parts of a Synapse?
- Axon terminal
- Synaptic vesicles carrying neurotransmitter
- Voltage-gated Ca ion channel
- Synaptic cleft
- Receptor
- Enzyme
- Re-uptake molecule
-
What are the functions (in order) of a synapse?
- 1. Action Potential
- 2. Voltage-gated Ca channels open
- 3. Ca binds to docking proteins and stimulates exocytosis
- 4. NT diffuses and binds to receptor
- 5. Response in cell (terminated by removing neurotransmitter from cleft)
- 6. Degradation
- 7. Re-uptake
- 8. Diffusion
-
What is synaptic delay and what is it caused by?
- 0.5 - 5 msec btwn arrival of AP and change in postsynaptic Vm
- Caused by changes in [Ca] and release of neurotransmitter
-
What are the 2 forms of signal transduction at synapses?
Channel-linked receptors - fast and direct-acting
G-protein-linked receptors - slow acting, require metabolite
-
What is postsynaptic potential (PSP)?
Change in membrane potential in response to receptor-neurotransmitter binding.
- Some excitatory (EPSP)
- Some inhibitory (IPSP)
-
What are the differences between excitatory and inhibitory synapses?
Excitatory - more likely to produce AP, depolarization
Inhibitory - less likely to produce AP, hyperpolarization, membrane stabilization
-
What are the 2 ions associated with IPSP?
K+ and Cl-
-
Why are IPSPs graded potentials?
- Higher frequency of APs
- More NT released
- More NT binds to receptors to opn/close channels
- Greater increase/decrease in ion permeability
- Greater/lesser ion flux
- Greater hyperpolarization
-
What is Neural Integration?
The summing of input from various synapses at the axon hillock of the postsynaptic neuron to determine whether the neuron will generate APs
-
What are some examples of neurotransmitters?
- Acetylcholine
- Biogenic amines
- Amino acid neurotransmitters
- Neuropeptides
- Other NTs
-
What is the most abundant NT in the PNS?
Acetylcholine
-
What is the chemical reactoin of Acetylcholine synthesis? Where does it happen and what enz is involved?
Acetyl CoA + choline --> acetylcholine + CoA
- Synthesized in cytosol of axon terminal
- Enz for synth = choline acetyl transferase (CAT)
-
What is the chemical reaction for Acetylcholine breakdown? Where does it happen and what enz is involved?
Acetylcholine --> acetate + choline
- Degraded in synaptic cleft
- Enz of deg = acetylcholinesterase (AChE)
-
What is a cholinergic synapse?
Synapse utilizing acetylcholine
"-ergic" means bind; cholinergic binds choline
-
What are the 2 types of Cholinergic Receptors?
1. Nicotinic - ionotropic
2. Muscarinic - metabotropic
-
What are biogenic amines derived from and what are some examples?
Amino Acids
- Catecholamines - derived from tyrosine (dopamine, norepinephrine, epinephrine)
- Serotonin - derived from tryptophan
- Histamine - derived from histidine
-
What are the enzymes responsible for degrading biogenic amines?
- Monoamine oxidase (MAO)
- Catechol-o-methyltransferase
-
How are biogenic amines synthesized and where are they released?
Synthesis: cytosol of terminal, packaged into synaptic vesicles, released
Release: Dopamine & Norepinephrine CNS, Norepinephrine also in PNS, Epinephrine from CNS but more commonly released as hormone from adrenal medulla
-
What are the 2 different adrenergic receptors and waht are their subunits?
- Alpha adrenergic receptors
- Alpha1
- Alpha2
- Beta adrenergic receptors
- Beta1
- Beta2
- Beta3
-
Which adrenergic receptor has the greatest affinity for epinephrine? ... norepinephrine?
Beta2
Alpha and Beta 1
-
What is the speed of adrenergic receptor responses?
- Slow
- G-protein coupled
- Linked to second messengers
-
What are the properties of Serotonin?
- CNS NT
- Brainstem
- Regulates sleep
- Emotions
-
What are the properties of Histamine?
- CNS NT
- Hypothalamus
- More commonly known for paracrine actions
-
Which AA NT are at excitatory synapses?
-
Which AA NT are at inhibitory synapses?
-
What are Neuropeptides?
- Short chains of AAs
- Co-located with other NTs
- Modulate response caused by other NT
- Ex. Endogenous opioids (enkephalins, endorphins). TRH, ADH, Oxytocin, Substance P
|
|
