Lecture 5: Muscles

Question 1

Describe a skeletal muscle

Answer 1

Bundles of long, cylindrical multinucleated cells with cross-striations

Question 2

Describe cardiac muscle

Answer 2

Elongated branched individual cells with cross-striations that are parallel to one another

Question 3

Describe a smooth muscle

Answer 3

Collection of fusiform cells without cross-straiations

Question 4

Skeletal muscles form from a fusion of what kind of cells?

Answer 4

Myoblasts

Question 5

What are intrafusal fibers innervated by?

Answer 5

Sensory: Ia, II
Motor: (y)

Question 6

What are extrafusal fibers innervated by?

Answer 6

Motor: alpha- motor neurons

Question 7

What do intrafusal fibers do

Answer 7

They are the proprioceptive fibers of muscle spindles

Question 8

What do extrafusal fibers do?

Answer 8

They produce tension

Question 9

What are the three types of skeletal musclefibers?

Answer 9

1. slow fibers, red (type I)
2. fast glycolytic fibers, white (type II-b)
3. fast oxidative fibers (type II-a)

Question 10

What muscle fibers are specialized for long-term contraction w/ mitochondrial performance and oxidative?

Answer 10

Type I

Question 11

What muscle fibers contract fast, produce tension, and fatigue the fastest (ATP use)?

Answer 11

Type II-b

Question 12

What muscle fibers fatigue the fastest?

Answer 12

Type II-a

Question 13

Compare the velocities of type I and II muscle fibers

Answer 13

I: slow
II: fast

Question 14

What is the tension generated by muscle fibers proportional to?

Answer 14

the cross-sectional area

Question 15

Golgi tendon organs are what kind of nerve fibers? Muscle Spindles?

Answer 15

Group 1b afferent

Group Ia afferent

Question 16

Describe the tendon reflex

Answer 16

It inhibits the muscle from contracting too strongly so it doesnt tear a tendon or pull loose from muscle or bone

Question 17

Name the breakdown from muscle to filaments.

Answer 17

Muscle
Fasicle (made up of group of muscle fibers)
Fiber (made up of myofibrils)
Myofibrils (composed of sarcomeres)
Sarcomeres (basic unit of contraction)

Question 18

What is the ratio of troponin-tropomyosin complexes to actin molecules?

Answer 18

1:7

Question 19

What are the components of thick filaments?

Answer 19

2 heavy chains, 4 light chains

Question 20

What anchors thin filaments to Z-line?

Answer 20

alpha actin

Question 21

What anchors thick filaments to Z line?

Answer 21

Titin

Question 22

What is the molecular ruler for thin filaments?

Answer 22

Nebulin

Question 23

What are two proteins that keep thick filaments in register?

Answer 23

myomesin and C-protein

Question 24

What is the actin capping protein responsible for regulating the length of thin filaments

Answer 24

Tropomodulin

Question 25

What keeps myofibrils in registter during contraction?

Answer 25

Desmin

Question 26

Where does calcium bind to cause dissociation of Troponin I from actin?

Answer 26

Troponin C

Question 27

Muscle contraction is a result of?

Answer 27

thin filaments sliding over thick filaments, pulling Z lines closer

Question 28

What is rigor?

Answer 28

absence of ATP which causes the myosin heads to remain bound to actin

Question 29

What part of the protein complex anchors thin filaments in a muscle fiber to the sarcolemme and basal lamina?

Answer 29

Dystrophin

Question 30

What pathology results from no dystrophin being synthesized? What is a characteristic sign?

Answer 30

Duchenne Muscular Dystrophy – Gower’s sign (using arms to help stand)

Question 31

What pathology results from partially functional or reduced amounts of dystrophin being synthesized?

Answer 31

Becker’s Muscular Dystrophy

Question 32

What protein suppresses muscle growth and can be used as potential theraphy for DMD or BMD?

Answer 32

Myostatin

Question 33

This hormone is produced and secreted by atrial myocytes. It inhibits renin and aldosterone secretion and relaxes vascular SM.

Answer 33

Atrial Natriuretic Factor (ANP)

Question 34

What is released from ventricles in response to left ventricular defect?

Answer 34

Brain natriuretic factor

Question 35

Corkscrew nuclei is characteristic of what tissue?

Answer 35

Smooth muscle

Question 36

In smooth muscle, what does Ca+ bind to, to in itiate contraction?

Answer 36

calmodulin –> myosin light chain kinase

Question 37

What are three characteristics of a cardiac muscle under a microscope?

Answer 37

1. myonuclei
2. fibroblasts
3. intercalated disks (communition)