8. Types of synapses and neurotransmitter released by presynaptic neuron Flashcards
What is a synapse
Site where information is transmitted from one cell to another
Can be electrically or chemically
What are electrical synapses
Allows current to flow through GAP JUNCTIONS - connexons- composed of 6 connexins
Transmission is bidirectional
Ions, sucrose, cAMP, low molecular peptides
Found in cardiac muscle and smooth muscle
Very fast as direct flow of ions
What is the adv of electrical synapses compared to chemical synapse
Rapid cell to cell conduction
Synaptic delay in chemical synapses
buttt chemical is needed for more slower conduction otherwise everything in ur body will be stimulated for no reason
What are chemical synapses
Located in CNS
In these synapses there is a gap called synaptic cleft between the presynaptic neuron and postsynaotic neuron
Neurotransmitters transmit the info across cleft
The change in the membrane potential on the postsynaptic neuron can be either….?
Excitatory- neurotransmitter causes depolarization
Inhibitory- neurotransmitter causes hyperpolarization
Whats the difference between direction of transmission of the synapses
Chemical synapses are unidirectional
What is an example of a chemical synapse
Neuromuscular junction
Ca2+ causes the release of Acetylcholine (quantal release)
Diffuses across the synaptic cleft to the postsynaptic membrane. This specialized region of the muscle fiber is called the motor end plate, which
contains nicotinic receptors for ACh. (LIGAND GATED ION CHANNEL)
Causes Na+/K+ channels to open and cause depolarization
What are some excitatory neurotransmitters
ACh, dopamine, epinephrine?( technically hormone) norepinephrine, glutamate, seratonin
What are some inhibitory neurotransmitters
γ-aminobutyric
acid (GABA) and glycine.
Presynaptic information can arrive at a synapse in 2 ways. What are they
Spatial summation: two or more presynaptic inputs arrive at a postsynaptic cell simultaneously.
Temporal summation: 2 synaptic inputs arrive sequentially- bc they overlap, they summate
What is the criteria to be known as a neurotransmitter
- mUst be synthesized in presynaptic cell
- Muat be released on stimulation
- If its applied exogenously to postsynaptic membrane it must mimic the response
Neurotransmitter groups
ACh, biogenic amines, amino
acids, and neuropeptides
Why is acetylcholine important
Only neurotransmitter used at neuromuscular junction
Choline acetyltransferase joins acetyl and CoA together
Acetylcholinesterase degrades it and the choline cane be used again at presynaptic terminal
How are the biogenic amine neurotransmitters made
Tyrosine converted to L-DOPA by tyrosine hydoxyase
L-DOPA converted to dopamine by dopa carboxylase
dopamine β-hydroxylase converts dopamine to noepinephrine
phenylethanolamine-N-methyl transferase
(PNMT) is present (with S-adenosylmethionine as the
methyl donor), then norepinephrine is methylated to form epinephrine.
Seratonin and histamnie are synthesized from what and what do they do
- From tryptophan, serves as a precursor to melatoninn
- From histidine, in mast cells and neurons in hypothalmus
