8. Types of synapses and neurotransmitter released by presynaptic neuron

Question 1

What is a synapse

Answer 1

Site where information is transmitted from one cell to another
Can be electrically or chemically

Question 2

What are electrical synapses

Answer 2

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

Question 3

What is the adv of electrical synapses compared to chemical synapse

Answer 3

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

Question 4

What are chemical synapses

Answer 4

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

Question 5

The change in the membrane potential on the postsynaptic neuron can be either….?

Answer 5

Excitatory- neurotransmitter causes depolarization

Inhibitory- neurotransmitter causes hyperpolarization

Question 6

Whats the difference between direction of transmission of the synapses

Answer 6

Chemical synapses are unidirectional

Question 7

What is an example of a chemical synapse

Answer 7

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

Question 8

What are some excitatory neurotransmitters

Answer 8

ACh, dopamine, epinephrine?( technically hormone) norepinephrine, glutamate, seratonin

Question 9

What are some inhibitory neurotransmitters

Answer 9

γ-aminobutyric
acid (GABA) and glycine.

Question 10

Presynaptic information can arrive at a synapse in 2 ways. What are they

Answer 10

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

Question 11

What is the criteria to be known as a neurotransmitter

Answer 11

• mUst be synthesized in presynaptic cell
• Muat be released on stimulation
• If its applied exogenously to postsynaptic membrane it must mimic the response

Question 12

Neurotransmitter groups

Answer 12

ACh, biogenic amines, amino
acids, and neuropeptides

Question 13

Why is acetylcholine important

Answer 13

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

Question 14

How are the biogenic amine neurotransmitters made

Answer 14

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.

Question 15

Seratonin and histamnie are synthesized from what and what do they do

Answer 15

• From tryptophan, serves as a precursor to melatoninn
• From histidine, in mast cells and neurons in hypothalmus

Question 17

What exactly is the pre synaptic part of neuron

Answer 17

Covers the final extension of the axon (axons end)

Axonal end has vesicles filled with mediator and mitochondria

Cholingeric synapses- Ach
Adrenergic synapses- norepinephrine

Question 18

During opening/closing of which channels are generated EPSP

Answer 18

• opening Na+ channels
• closing K+
• opening non selective Na/k+ or Na/k/ca channels

Question 19

During opening of which channels are generated IPSP

Answer 19

• opening of Cl-
• opening of K+

Question 20

Why can postsynaptic potentials be summated

Answer 20

Because multiple presynaotic nerve endings terminate and release mediators on the dentrites/cell body of one postsynaptic neuron

Question 21

What are the differences between PSP and AP

Answer 21

PSP are slower than AP
(15-20 ms while AP 0.5-1 ms)

Amplitude if PSP directly proportional to amount of mediator released