3.1 Muscles

Question 1

From largest to smallest, what are the units of muscle?

Answer 1

Skeletal muscle (organ)
Fascicle (bundles)
Muscle fiber (cell)
Myofibril (contractile organelle)
Sarcomere- actin and myosin

Question 2

What are the specialized organelles of a muscle cell?

Answer 2

sarcoplasm: cytoplasm
sarcolemma: cell membrane
mitochondria
sarcoplasmic reticulum: modified ER for calcium storage and release
T-tubules: invagination of cell membrane
terminal cisternae: ends of T-tubules
myofibrils**: specialized contractile organelle

Question 3

What are the 3 sheathes in a muscle?

Answer 3

Epimysium –surrounds the entire muscle, dense irregular CT
Perimysium – surrounds fascicles, dense elastic CT
Endomysium – surrounds individual muscle fibers, reticular CT

Question 4

If joint has stability issues, what is likely the cause?

Answer 4

Ligament issue

Question 5

If a joint has pain with movement, what is likely the cause?

Answer 5

Tendon issue

Question 6

What is a strain?

Answer 6

muscle or tendon is pulled, small blood vessels tear, nerve endings are irritation
muscle spasm, swelling, crepitation (cracking sounds), joint enlargement, tenderness, decreased range of motion, normal deep tendon reflexes

Question 7

What is a sprain?

Answer 7

ligaments are stretched and over extended

sharp pain, tenderness, spasm, decreased, painful range of motion, absence of neurological symptoms numbness or weakness

Question 8

What are the most common sprains? Cause?

Answer 8

ankle sprain: usually inversion of the foot during plantar flexion, recurring and common in athletes and nonathletes.
exclude ankle fracture
cervical strain: “whiplash” common with motor vehicle accidents symptoms within 12-72 hours, also repetitive stress injury, abnormal posture
lumbosacral strain and sprain – common cause of low back pain sudden contraction, torsion, severe blows, forceful extension (ex: heavy lifting)

Question 9

In a muscle, what is the thick fiber? The thin?

Answer 9

Thick- myosin

Thin- Actin

Question 10

What are the Z-lines?

Answer 10

Boundary of the sarcomere

Question 11

What is the I-band?

Answer 11

Thin filaments only

Question 12

What is the H-band?

Answer 12

Thick filaments only (center)

Question 13

What is the A-band?

Answer 13

Where thick/thin fibers overlap

Question 14

What is the M-line?

Answer 14

The center

Question 15

Describe a myosin fiber

Answer 15

Tail with split head, arranged in bundles with heads out

Heads contain ATP binding site and actin binding site

Question 16

Describe an actin filament. What two proteins are notabel?

Answer 16

Contains binding site for myosin heads
Troponin – contains three binding actin binding site, tropomyosin binding site, calcium binding site, holds tropomyosin in place
Tropomyosin –blocks actin’s active site, prevents myosin binding to actin

Question 17

What is ALS?

Answer 17

Amyotropic Lateral Sclerosis (ALS, or “Lou Gherig’s disease)
loss of upper and lower motor neurons that control voluntary muscles, muscle weakness, muscle atrophy and paralysis ultimately to respiratory muscle failure, sensation and cognitive ability intact

Question 18

What is MS?

Answer 18

inflammation and damage to myelin and other CNS cells, remissions (healing) and exacerbations fluctuate, sensory and motor symptoms

Question 19

What is Guilian-Barre?

Answer 19

spinal, cranial and peripheral nerve damage likely by macrophage attack on myelin, axon damage

Question 20

What is myasthenia graves?

Answer 20

loss of acetylcholine receptors at the neuromuscular junction, autoimmune (ach receptor antibodies detected in some cases)

Question 21

What are the 3 phases of muscle twitch?

Answer 21

latent period: delay between action potential stimulus arrival and calcium release from SR

contraction: calcium ions bind to troponin, crossbridges formed between myosin and actin
relaxation: calcium levels decrease as calcium pumped back into SR and crossbridges detach

Question 22

How do you get maximum possible contractile power?

Answer 22

tetany: maximal possible strength of muscle contraction, a long smooth contraction for maximum contractility… How? Fast action potentials