Synapses

Question 1

Synapse Types

Answer 1

1. Gray’s Type I - round, clear vesicles, usually excitatory
2. Gray’s Type II - flattened, clear vesicles - usually inhibitory
3. Specialized synapses

Question 2

Synaptic Vesicles

Electron-Lucent Vesicles

Answer 2

1. Small spherical - Gray’s Type I; acetylcholine, amino acids
2. Small flattened - Gray’s Type II; GABA, glycine
3. Coated, pinocytotic

Question 3

Synaptic Vesicles

Electron-Dense Vesicles

Answer 3

1. Small and medium - catecholamines; often seen in sympathetic nerve endings
2. Large - peptides (ADH, oxytocin)
3. Very large - enzymes (perioxosomes, secretory enzymes, etc.)

Question 4

Basic mechanism of a chemical synapse

Answer 4

1. Action potential arrives at presynaptic terminal - depolarization
2. Calcium channels open - calcium ions enter and activate vesicle binding to presynaptic membrane
3. Neurotransmitter is released and diffuses across synaptic cleft
4. Neurotransmitter binds to postsynaptic receptor
5. Ion channels open/close
6. Membrane potential of postsynaptic neuron changes - depolarization/hyperpolarization

Question 5

EPSP

Answer 5

• Postsynaptic receptor opens ion channels for sodium
• Sodium ions enter cell - depolarization

Doesn’t always produce an action potential - has to reach threshold first

Question 6

IPSP

Answer 6

• Postsynaptic receptor opens ion channels for chloride/potassium
• Chloride moves in/Potassium moves out - hyperpolarization

Question 7

Spatial summation

Answer 7

• Increased number of synapses of the same type (excitatory/inhibitory) activate simultaneously

Visual: Multiple plugs for one outlet sending electricity to it

Question 8

Temporal summation

Answer 8

• Repeated activation of the same synapse within a brief time (up to 100/second)

Visual: One plug sending multiple electricity bouts to one outlet

Question 9

Fast transport

(Orthograde)

• What it moves
• Rate

Answer 9

• Moves large particulate and non-soluble materials
• Packaged into vesicles
• 400 mm/day

Question 10

Slow transport

• What it moves
• Rate

Answer 10

• Moves dissolved substances
• Don’t need to be packaged into vesicles
• 1 mm/day

Question 11

Retrograde transport

• What it moves
• Rate

Answer 11

• Recycles materials
• Carries chemicals at 200 mm/day