33: Synaptic Transmission And Excitation-Contraction Coupling

Question 1

Two types of synapses and which is common in humans

Answer 1

Electrical, chemical (common in humans)

Question 2

Best example of human electrical synapse

Answer 2

Cardiac myocytes

Question 3

Chemical synapse

Answer 3

Neurotransmitter used to diffuse across synaptic cleft -> receptor

Question 4

Specificity of general chemical synapse pre- and post-synaptic cells

Answer 4

Pre-synaptic: can signal 1 or many post-synaptic

Post-synaptic: can receive signals from 1 or many pre-synaptic

Question 5

Specificity of NMJ pre- and post-synaptic cells

Answer 5

Pre-synaptic: innervates 1 or many muscle cells

Post-synaptic: receives signal from only one pre-synaptic axon

Question 6

Motor end plate

Answer 6

Specialized synaptic region in NMJ

Question 7

What happens when an AP reaches a muscle cell?

Answer 7

Activates DHP receptors -> physically alter ryanodine receptors -> Ca channels in SR open -> Ca into sarcoplasm

Question 8

How does Ca get removed from muscle cell at the end of an AP?

Answer 8

Ca/ATPase pump sequesters Ca back into SR

Question 9

Peripheral vs central fatigue

Answer 9

Peripheral: depletion of ATP
Central: feeling of fatigue due to increased levels of byproducts (H ions, lactic acid)

Question 10

Three ways muscle cells can get ATP

Answer 10

Phosphocreatine, glycolysis, oxphos

Question 11

Three types of skeletal muscle fibers

Answer 11

1. Slow twitch oxidative
2. Fast twitch glycolytic
3. Fast twitch oxidative

Question 12

Slow twitch oxidative muscle fibers

Answer 12

Red (myoglobin and mito present), small, fatigue resistant

Question 13

Fast twitch glycolytic muscle fibers

Answer 13

White, large diameter

Question 14

Preferred energy use for slow twitch vs fast twitch fibers

Answer 14

Slow twitch: O2

Fast twitch: phosphocreatine, glucose

Question 15

Four things that alter the force of muscle contraction

Answer 15

1. Starting length of sarcomere
2. How rapidly fiber is stimulated by nerve
3. Innervation type
4. Muscle type

Question 16

What happens if sarcomere is too short or too long?

Answer 16

Short: myosin cant pull actin v far before it hits Z line + cross sectional area increases so actin and myosin are farther apart
Long: many myosin heads not in line with actin anymore

Question 17

Tetanus

Answer 17

Overlap of twitches such that complete relaxation is not achieved

Question 18

Recruitment

Answer 18

Activating more motor neurons -> motor units generate greater force