Nerve muscle

Question 1

What are excitable tissues?

Answer 1

Tissues that respond to stimuli by generating action potentials (e.g., nerves and muscles).

Guyton 4th SA Ed.

Question 2

What is the resting membrane potential (RMP) of a neuron?

Answer 2

Around -70 mV, maintained by Na+/K+ ATPase.

Guyton 4th SA Ed.

Question 3

What is the RMP of skeletal muscle?

Answer 3

Approximately -90 mV, more negative than neurons.

Guyton 4th SA Ed.

Question 4

What are the phases of an action potential?

Answer 4

Depolarization (Na+ influx), Repolarization (K+ efflux), Hyperpolarization.

Guyton 4th SA Ed.

Question 5

What is the all-or-none principle?

Answer 5

An action potential occurs fully or not at all when threshold is reached.

Guyton 4th SA Ed.

Question 6

What is saltatory conduction?

Answer 6

Rapid impulse transmission in myelinated fibers via nodes of Ranvier.

Guyton 4th SA Ed.

Question 7

What is the role of myelin?

Answer 7

Increases conduction velocity and reduces energy consumption.

Guyton 4th SA Ed.

Question 8

What is a synapse?

Answer 8

A junction between two neurons or a neuron and muscle fiber for signal transmission.

Guyton 4th SA Ed.

Question 9

What is the role of calcium in neurotransmitter release?

Answer 9

Ca²⁺ influx triggers vesicle fusion and neurotransmitter release.

Guyton 4th SA Ed.

Question 10

What is the function of acetylcholinesterase?

Answer 10

Breaks down acetylcholine (ACh) to terminate synaptic transmission.

Guyton 4th SA Ed.

Question 11

What is the neurotransmitter at the NMJ?

Answer 11

Acetylcholine (ACh).

Guyton 4th SA Ed.

Question 12

What is an end-plate potential (EPP)?

Answer 12

Depolarization at the NMJ leading to muscle action potential.

Guyton 4th SA Ed.

Question 13

What is Myasthenia Gravis?

Answer 13

An autoimmune disorder causing NMJ dysfunction due to ACh receptor antibodies.

LPR Fundamentals 9th Ed.

Question 14

What is Botulinum toxin’s effect on NMJ?

Answer 14

Blocks ACh release, causing flaccid paralysis.

LPR Fundamentals 9th Ed.

Question 16

What is the sliding filament theory?

Answer 16

Actin and myosin filaments slide past each other for contraction.

Guyton 4th SA Ed.

Question 17

What is the role of calcium in muscle contraction?

Answer 17

Binds to troponin, allowing actin-myosin interaction.

Guyton 4th SA Ed.

Question 18

What is rigor mortis?

Answer 18

Postmortem muscle stiffness due to ATP depletion.

LPR Fundamentals 9th Ed.

Question 19

What are the types of muscle contraction?

Answer 19

Isometric (no shortening), Isotonic (shortening).

Guyton 4th SA Ed.

Question 20

What are the types of skeletal muscle fibers?

Answer 20

Type I (slow-twitch), Type II (fast-twitch).

Guyton 4th SA Ed.

Question 21

What is the difference between Type I and Type II fibers?

Answer 21

Type I: endurance, aerobic. Type II: power, anaerobic.

Guyton 4th SA Ed.

Question 22

What is the major difference between skeletal and smooth muscle contraction?

Answer 22

Smooth muscle lacks troponin and uses calmodulin.

Guyton 4th SA Ed.

Question 23

What is the function of myosin light chain kinase (MLCK)?

Answer 23

Phosphorylates myosin, enabling contraction in smooth muscle.

Guyton 4th SA Ed.

Question 24

What is latch-bridge mechanism in smooth muscle?

Answer 24

Maintains contraction with minimal ATP use.

Guyton 4th SA Ed.

Question 25

What is Duchenne Muscular Dystrophy?

Answer 25

X-linked disorder causing dystrophin deficiency and muscle wasting. ## Footnote LPR Fundamentals 9th Ed.

Question 26

What is Lambert-Eaton syndrome?

Answer 26

Autoimmune attack on presynaptic Ca²⁺ channels, reducing ACh release. ## Footnote LPR Fundamentals 9th Ed.

Question 27

What is tetanus toxin's effect?

Answer 27

Blocks inhibitory neurotransmitters, causing spastic paralysis. ## Footnote LPR Fundamentals 9th Ed.

Question 28

What is hypokalemic periodic paralysis?

Answer 28

Episodic muscle weakness due to low potassium levels. ## Footnote LPR Fundamentals 9th Ed.

Question 29

What are the sources of ATP in muscle contraction?

Answer 29

Phosphocreatine, Glycolysis, Oxidative phosphorylation. ## Footnote (Guyton 4th SA Ed.)

Question 30

What is oxygen debt?

Answer 30

Extra oxygen needed post-exercise to restore ATP levels. ## Footnote (Guyton 4th SA Ed.)

Question 31

What is the role of lactic acid in muscle fatigue?

Answer 31

Lowers pH, inhibiting enzyme activity and contraction. ## Footnote (Guyton 4th SA Ed.)

Question 32

What is a reflex arc?

Answer 32

Involuntary response pathway involving sensory and motor neurons. ## Footnote (Guyton 4th SA Ed.)

Question 33

What is the function of muscle spindles?

Answer 33

Detect muscle stretch and mediate stretch reflex. ## Footnote (Guyton 4th SA Ed.)

Question 34

What is the Golgi tendon reflex?

Answer 34

Inhibits muscle contraction to prevent excessive tension. ## Footnote (Guyton 4th SA Ed.)

Question 35

What is spasticity?

Answer 35

Increased muscle tone due to upper motor neuron lesion. ## Footnote (LPR Fundamentals 9th Ed.)

Question 36

What is flaccid paralysis?

Answer 36

Loss of muscle tone due to lower motor neuron damage. ## Footnote (LPR Fundamentals 9th Ed.)

Question 37

What maintains the resting membrane potential?

Answer 37

Na+/K+ ATPase (pumps 3 Na⁺ out, 2 K⁺ in), K⁺ leak channels.

Question 38

What is the threshold potential

Answer 38

The voltage at which voltage-gated Na⁺ channels open (~ -55 mV in neurons)

Question 39

What is hyperpolarization

Answer 39

Membrane potential becomes more negative than RMP due to prolonged K⁺ efflux.

Question 40

What is the absolute refractory period

Answer 40

No new action potential can be generated as Na⁺ channels are inactivated.

Question 41

What is the relative refractory period

Answer 41

A stronger-than-normal stimulus can trigger an action potential.

Question 42

What are the types of synapses

Answer 42

Chemical (neurotransmitter-mediated) & Electrical (gap junctions)

Question 43

What is synaptic delay

Answer 43

Time (~0.5 ms) for neurotransmitter release, diffusion, and receptor binding.

Question 44

What is temporal summation

Answer 44

Multiple signals from one neuron add up over time to trigger an action potential.

Question 45

What is spatial summation

Answer 45

Inputs from multiple neurons add together to reach threshold.

Question 46

What is an excitatory postsynaptic potential (EPSP)

Answer 46

Depolarization caused by Na⁺ or Ca²⁺ influx.

Question 47

What is an inhibitory postsynaptic potential (IPSP)

Answer 47

Hyperpolarization caused by Cl⁻ influx or K⁺ efflux

Question 48

What is the effect of curare on NMJ

Answer 48

Blocks ACh receptors, causing paralysis

Question 49

How does organophosphate poisoning affect NMJ

Answer 49

Inhibits acetylcholinesterase, leading to excessive ACh and muscle spasms

Question 50

What is the treatment for Myasthenia Gravis

Answer 50

Acetylcholinesterase inhibitors (e.g., pyridostigmine) to prolong ACh action.

Question 51

How does succinylcholine act as a neuromuscular blocker

Answer 51

Causes sustained depolarization, leading to flaccid paralysis

Question 52

What is the length-tension relationship

Answer 52

Optimal sarcomere length (~2.2 µm) generates maximal force.

Question 53

What is motor unit recruitment

Answer 53

Increasing the number of motor units to generate more force.

Question 54

What is tetanus in muscle contraction

Answer 54

Sustained contraction due to high-frequency stimulation

Question 55

What is the staircase effect (Treppe phenomenon)

Answer 55

Gradual increase in contraction strength with repeated stimulation.

Question 56

What is muscle fatigue

Answer 56

Reduced contraction force due to ATP depletion and metabolite buildup

Question 57

What are the two types of smooth muscle

Answer 57

Multi-unit (independent fibers, e.g., iris) & Single-unit (gap junctions, e.g., intestines).

Question 58

How does smooth muscle contract without troponin

Answer 58

Uses calmodulin to activate myosin light chain kinase (MLCK).

Question 59

What is the latch mechanism in smooth muscle

Answer 59

Sustains contraction with minimal ATP use by reducing myosin detachment.