Synaptic Transmission

Question 1

Direct transfer of molecules and ions from the cytoplasm of one cell into that of another

Answer 1

electrical synapse (is the interface) (Gap junctions mediate this transfer)

Question 2

The release of a chemical from one cell that diffuses to and acts upon another cell

Answer 2

secretion is the process, chemical synapse is the interface

Question 3

Connexons

Answer 3

Part of gap junctions, with one end in the presynaptic cell and the other in the postsynaptic cell, form a channel between the cytoplasm.
Each is made up of six protein molecules

Question 4

Approximate size of pores in gap junctions

Answer 4

1.5 nm (ions can pass through, cAMP)

Question 5

Reasons that a gap junction might close

Answer 5

lowered cytoplasmic pH, elevation of calcium

Question 6

Locations of gap junctions

Answer 6

hypothalamus (release hormones at same time in a flood), heart, smooth muscle cells, connect successive layers of myelin

Question 7

Charcot-Marie-Tooth

Answer 7

X-chromosome linked disease where Schwann cell connexin fails to properly form and peripheral nerves demyelinate

Question 8

The internal concentration of calcium (in a neuron specifically)

Answer 8

0.0002 mM

Question 9

What causes the release of neurotransmitters?

Answer 9

The action potential causes voltage gated calcium channels in the active zone to open. Calcium enters as long as the channels are open. The rise in internal calcium causes the neurotransmitters to be released.

Question 10

What is NSF?

Answer 10

NEM-sensitive fusion protein is a protein involved in the exocytosis of a neurotransmitter (primes synaptic vesicles for fusion to the cell membrane). Regulate the assembly of SNAREs

Question 11

What is SNAPs?

Answer 11

soluble NSF-attachment proteins are involved in priming synaptic vesicles for fusion (to the cell membrane). They regulate the assembly of SNAREs

Question 12

What are SNAREs?

Answer 12

They are SNAP receptors that bind the vesicle to the membrane
Synaptobrevin is in the membrane of the synaptic vessicles. Syntaxin and SNAP-25 are on the plasma membrane

Question 13

What is synaptotagmin?

Answer 13

It is a protein found in the synaptic vesicle that is responsible for calcium regulation of neurotransmitter release. When the calcium concentration rises, this protein binds to proteins in the cell membrane and the vesicle and cell membrane fuse and the neurotransmitters are released into the synaptic cleft.

Question 14

What is curare?

Answer 14

It is a pharmacological agent that blocks postsynaptic acetylcholine receptors

Question 15

Miniature end plate potentials

Answer 15

spontaneously occurring depolarizations of the muscle cell membrane similar to end plate potentials

Question 16

The effect of increasing calcium concentration surrounding the neuromuscular junction

Answer 16

It DOES NOT change the amplitude of the unit synaptic potential, but the number of failed responses decreases and the number of higher-amplitude responses increases.
It doesn’t affect quantal size, but it affects release probability

Question 17

About how much acetylcholine is required to initiate a spontaneous MEPP?

Answer 17

7,000 molecules

Question 18

What happens to acetylcholine after it is released from the synaptic vesicle?

Answer 18

It binds to ligand-gated channels on the post-synaptic membrane for about 1 millisecond, then it is broken down to choline (and acetate) by acetylcholinesterase in the synaptic cleft. Choline is taken up by sodium coupled choline transport in the presynaptic membrane and converted to acetylcholine by choline acetyltransferase. (Acetyl-CoA and choline are combined)

Question 19

Action potentials are usually generated at the ___.

Answer 19

Axon hillock (because sodium and potassium channels are concentrated there)

Question 20

Excitatory neurotransmitters

Answer 20

acetylcholine, glutamate

increase sodium permeability in the postsynaptic membrane

Question 21

Voltage where sodium and potassium membrane permeabilities are equal

Answer 21

-11.5 mV (Above this, more potassium leaves the cell than sodium enters. Below, more sodium enters the cell than potassium leaves)

Question 22

Inhibitory neurotransmitters

Answer 22

GABA

Increase chloride permeability

Question 23

Information (in relation to intensity) is coded by ___.

Answer 23

frequency and frequency modulation (not amplitude)

Question 24

What is myasthenia gravis?

Answer 24

It occurs when antibodies bind to post-synaptic receptors and is associated with weakness of skeletal muscle. It can be treated with 10 mg of edrophonium, which is an anticholinesterase. If that does not work, IV IgG given to lower production of all antibodies OR give immunosuppressant like prednisone OR plasmapheresis

Question 25

What is an EEG?

Answer 25

An electroencephalogram (measures electrical activity in the brain)

Question 26

What are some associations with seizure disorders?

Answer 26

They may be the result of a channelopathy (membrane channels have a defect). Paroxysmal depolarization shits occur due to defective sodium channels. It is more widespread if inhibitory interneurons are depleted. It can be treated with drugs that build membrane integrity or increase inhibitory signaling

Question 27

What does a generalized spike wave dysrhythmia look like?

Answer 27

Spikes, then slow waves that start and stop abruptly