Chapter 10 11

Question 1

What is Myology? How many muscles are in human body?

Answer 1

Myology is the study of structure, function
& Diseases of muscles.
640 muscles in human body

Question 2

What are the functions of muscles?

Answer 2

• Movement
  – Stability
  – Protection
  – Control of passageways, blood flow
  – Heat production
  – Glycemic control

Question 3

What are the structural and functional differences between the three types of muscles (skeletal, smooth
and cardiac)?

Question 4

What are fascia, epimysium, fascicle, perimysium, and endomysium?

Answer 4

Fascia- sheet of connective
tissue that separates muscles
Epimysium – dense regular
connective tissue that surrounds
the entire muscle
Perimysium – fibrous
connective tissue that surrounds
a fascicle
Endomysium – fine sheath of
reticular fibers surrounding each
muscle fiber

Question 5

What are the different types of muscle fascicles and muscle shapes and how do they influence the strength
of a muscle?

Answer 5

Slide 4
strength of a muscle and the direction of its pull is
determined partly by the orientation of its fascicles

Question 6

What are tendons, aponeurosis, and retinaculum?

Answer 6

Tendons – a fibrous band
- Biceps brachii, Achilles tendon
Aponeurosis— broad, flat sheet
of tendon (palmar aponeurosis)
Retinaculum— band of
connective tissue under which
tendons from different muscles
pass

Question 7

What are the functional groups of muscles based on their action?

Answer 7

Prime mover (agonist): muscle that produces most of the force during a particular joint (in flexing elbow the prime mover is the brachialis
Synergist: a muscle that aids the prime mover
Antagonist: opposes the prime mover
Fixator: muscle that prevents movement of bone

Question 8

What is compartment syndrome (Know the cause, symptoms and treatment)?

Answer 8

Compartment syndrome is muscle necrosis, myoglobinuria,
Treatment is fasciotomy

Question 9

What are the universal properties of muscles?

Answer 9

Excitability
Contractility
Extensibility
Elasticity

Question 10

What are intrinsic and extrinsic muscles?

Answer 10

Intrinsic muscles are entirely contained within
a particular region, having both its origin &
insertion there.
Extrinsic muscle acts upon a designated region
but has its origin elsewhere.

Question 11

What are the innervations of a muscle?

Answer 11

Innervation of a muscle—nerve that stimulates it

Question 12

How much blood supply is received by the muscles during rest and during exercise?

Answer 12

1.24 L/min of blood/min at rest, during heavy
exercise 11.6 L/min

Question 13

What are the structural components of a skeletal muscle fiber?

Answer 13

See slide 12
Sarcolemma
* Sarcoplasm
* Myofibrils—long protein cords that
occupy the main portion of the
sarcoplasm
* Mitochondria
* SR
* Terminal cisternae
* Triad

Question 14

What are different types of myofilaments? Which ones are the contractile and regulatory myofilaments?

Answer 14

Thick, Thin, and Elastic
Contractile proteins—myosin and actin do the work
* Regulatory proteins—tropomyosin and troponin

Question 15

What is the role of elastic filaments and accessory proteins?

Answer 15

Elastic Filaments Flank each thick filament and anchor it to the Z disc and M
line
Accessory proteins anchor the myofilaments, regulate the length of myofilaments, keep
alignment for optimal contractile effectiveness
– Genetic defects in dystrophin produce disabling disease muscular
dystrophy

Question 16

What is the cause for muscular dystrophy?

Answer 16

genetic effects in the dystrophin is the cause

Question 17

What is a sarcomere? What are A band, I band, H band, M line, Z disc? What is the sliding theory for
muscle contraction?

Answer 17

See diagram on slide
Sarcomere— Functional contractile unit of muscle fiber
A band: dark; A stands for anisotropic
I Band light due to thin filament and no overlap; I stands for
isotropic
H band: middle of A band; thick filaments only; no overlap
M line: middle of H band; darker due to the presence of the protein
desmin
Z disc: provides anchorage for thin filaments and elastic filaments, Z
discs are pulled closer as the thin filaments slide over thick filaments
Sliding theory for muscle contraction is that thin filaments slide over the thick one

Question 18

What are the sequential events that occur during muscle contraction?

Answer 18

See Slide 20
1. Myosin cross-bridge attaches to the actin myofilament
2. Working Stroke- the myosin head pivots and bends as it pulls on the actin filament sliding it towards the M line
3. As new ATP attaches to the myosin head, the cross bridge detaches
4. As ATP is split into ADP and Pi, cocking of the myosin head occurs

Question 19

What is a motor unit? What is the effect of a small and a large motor unit?

Answer 19

Motor unit—one nerve fiber and all
the muscle fibers innervated by it
small motor unit= used when fine control is needed (small sensitive neurons)
large motor unit= used when strength is more important (larger less sensitive neurons)

Question 20

What are the structural components of a neuromuscular junction?

Answer 20

See slide 23
Motor Nerve fiber, Myelin, Schwann cell, Synaptic knob, basal lamina, synaptic vessels (contains ACh), Sarcolemma Synaptic clef, ACh receptor, junctional folds, mitochondria,

Question 21

What are the phases of contraction and relaxation? Know the physiological events that occur during each phase

Answer 21

Four major phases are Excitation, Excitation-contraction coupling, Contraction, Relaxation

Excitation- Arrival of the nerve signal, Acetylcholine (ACh) release
Excitation-contraction coupling- Action potentials propagated down T tubules, calcium released from terminal cisternae, binding of calcium to troponin, shifting of tropomyosin
Contraction- hydrolysis of ATP to ADP +Pi; activation and cocking of myosin head (recovery stroke), formation of myosin-actin cross-bridge, power stroke (sliding of thin filament over thick filament), binding of new ATP; breaking of cross-bridge
Relaxation- Cessation of nervous stimulation and ACh release, ACh breakdown by acetylcholinesterase (AChE), reabsorption of calcium ions by sarcoplasmic reticulum

Question 22

RMP, depolarization, repolarization, action potential and ATP uses?

Answer 22

RMP= resting membrane potentional
Depolarization- shift in electrical potential across a plasma membrane to a value less negative than the resting membrane potential (happens in excitation of a nerve-muscle)
Repolarization- reattainment of the resting membrane potential after a nerve or muscle cell has depolarized
Action potential- rapid voltage change in which a plasma membrane briefly reverses electrical polarity
ATP in Contraction- Myosin head needs an ATP molecule bound to it to initiate contraction

Question 23

What is spastic paralysis and flaccid paralysis? What is the effect of various neuromuscular toxins-
pesticides, tetanus toxin, curare, botulism?

Answer 23

Spastic paralysis: a state of continual contraction of the muscles; possible
suffocation
Flaccid paralysis—a state in which the muscles are limp and cannot contract
Some pesticides contain cholinesterase inhibitors that prevent Ach degradation
Tetanus toxin blocks glycine release in the spinal cord and causes
overstimulation and spastic paralysis of the muscles
Curare: compete with ACh for receptor sites, but do not stimulate the
muscles
Botulism—type of food poisoning caused by a neuromuscular toxin secreted
by the bacterium Clostridium botulinum

Question 24

What is the relation between muscle length and muscle tone?

Answer 24

slide 33
if a fiber was extremely contracted, thick filaments would be too close to Z disc thus the thick filaments wouldn’t be able to contract much farther until hitting the z discs

If a muscle fiber was extremely stretched there would be little overlap of the thick and thin filaments

Question 25

What are the requirements for the regulation of skeletal muscle contraction?

Answer 25

Requirements for the regulation of skeletal muscle contraction are
ATP, calcium, proximity of actin and myosin head

Question 26

What are isometric and isotonic contractions?

Answer 26

Isometric muscle contraction
– develops tension without changing length
Isotonic muscle contraction
– tension while shortening = concentric
– tension while lengthening = eccentric

Question 27

What are the uses of ATP?

Answer 27

1. Breaking the Old Cross Bridge
2. Energy for the Power stroke
3. Energy for Calcium Pump in Sarcoplasmic
   Reticulum
4. Energy for Na/K ATPase

Question 28

What are the modes of ATP synthesis during immediate, short term and long-term exercise?

Answer 28

immediate- oxygen need is supplied by
myoglobin
short- muscles transition to anaerobic fermentation to generate ATP by glycosis
long- Aerobic respiration
* 36 ATP from glucose

Question 29

What happens during fatigue?

Answer 29

Potassium accumulation- K+ released during
action potential
* ADP/P accumulation- hydrolysis of ATP

Question 30

What happens during myasthenia gravis?

Answer 30

Autoimmune disease - antibodies
attack NMJ and bind ACh receptors
in clusters

Question 31

What is the cause for hernias and what are the main type of hernias?

Answer 31

Hernia—any condition in which the
viscera protrudes through a weak
point in the muscular wall of the
abdominopelvic cavity
inguinal Hernia, Hiatal hernia, Umbilical hernia

Question 32

What are the two main types of smooth muscles and how do they differ?

Answer 32

Single unit and multiunit smooth musles