Muscle Tissue

Question 1

What is the Sliding Filament Hypothesis and 3 main features

Answer 1

Sarcomere shortens and becomes thicker-myofilaments remain the same
1. **A band **remains constant
2. HI goes BYE (H and I bands)
3. Z lines are drawn closer to the ends of the A bands

Question 2

What are the five stages of the contraction cycle?

Answer 2

1. Attachment
2. Release
3. Bending
4. Force Generation
5. Reattachment

Question 3

Actin filaments things to know (4)

Answer 3

1. Covered in tropomyosin in a resting state
2. Plus end is bound to the Z-line by alpha-actin and nebulin
3. Minus end towards M line-protected by tropomodulin (actin capping protein)
4. G-actin polymerizes to form F-actin

Question 4

Myosin II (thick filament) things to know

Answer 4

1. Binds to actin subunits to produce movement
2. Has a head and tail region
3. 2 Globular heads (1 for ATP, 1 for actin)
4. “Bare zone” has no globular heads and is in the middle

Question 5

Important of the Sarcoplasmic Reticulum (SER)?

Answer 5

1. Forms a network around myofibrils
2. Extends from A-I junction to the next A-I junction in the same sarcomere* (T-tubules are invaginations at this same location)*
3. Houses Ca2+ ions

Question 6

What is/does Dystrophin do in Skeletal muscles?

Answer 6

1. Rod-shaped cytoskeletal protein
2. Links muscle fiber to ECM protein laminin
3. Forms a complex with Dystroglycans/Sarcoglycans (Transmembrane proteins)

Question 7

Type 1 skeletal muscle

Answer 7

Also known as slow oxidative, red
1. Small
2. Many mitochondria
3. Lots of myoglobin, Fe2+
4. Aerobic respiration, slow twitch/fatigue resistant
5. Used in marathon runners
Location: limb muscles

Question 8

Type II A skeletal muscles

Answer 8

Fast oxidative glycolytic/intermediate
1. High myoglobin and glycogen content
2. Anaerobic glycolysis
3. Fast twitch, fatigue resistant
4. Common in 400-800m sprinters

Question 9

Type 2 B skeletal muscles

Answer 9

Fast glycolytic
1. Large
2. Less mitochondria
3. Low level of oxidative enzymes-fatigue easy (lactic acid)
4. Large glycogen stores
Location: extraocular muscles, digits

Question 10

Sensory Innervation: Muscle Splindle

Answer 10

Senses changes in muscle length/stretch
Located: in the muscle belly

Question 11

Sensory Innervation: Golgi tendon organ

Answer 11

Senses tension in the muscle
Location: near the tendon

Question 12

What is the purporse and structure of intercalated discs?

Answer 12

Found in cardiac muscle
1. Transverse component (T):
-Fascia adherens (adhering junctions): serves as attachment site for thin filaments in terminal sarcomeres.
-Maculae adherens (desmosomes): bind to individual muscle cells. Reinforce fascia adherens and found in both T and L parts
2. Lateral component (L)
-Gap junctions

Question 13

Purkinje Fibers

Answer 13

1. Special modified cell found in cardiac tissue
2. Conduct impulses of the A-V bundle and allow synchonization of ventricular contraction
3. Abundant in mitochondria
4. Pale staining-large amt of glycogen

Question 14

In a relaxed state of Smooth Muscle Contraction where is calcium ions sequestered?

Answer 14

Sarcoplasmic Reticulum

Question 15

Outline nerve stimulation for smooth muscle contraction

Answer 15

1. Free calcium released from SR
2. Binds to calmodulin (MLCK complex)
3. Phosphoylates myosin
4. Myosin binds to actin
5. Contraction of muscle

Question 16

Trompomysin

Considered a regulatory protein

Answer 16

Covers the myosin binding site on the actin filament in the resting muscle

Question 17

Tropomodulin

Answer 17

Capping protein on actin

Question 18

Troponin complex (C, T, I)

Answer 18

C: binds to Calcium
T: binds to Tropomyosin
I: Inhibits actin-myosin interaction

Question 19

Nebulin

Answer 19

Stabilizes actin filaments

Question 20

Smallest to largest muscle naming

Answer 20

1.Myofilament
2. Myofibril
3. Myofiber
4. Fascile

Question 21

Types of Striated Muscle: Skeletal

Answer 21

1. Under voluntary control
2. Multinucleated with nuclei just beneath sarcolemma
3. Uniform in length

Question 22

Epi/Peri/Endomysium

Answer 22

Epi: dense connective tissue encasing multiple fasicles. Contains major BV/nerves
Peri: Around each fasicle. Also contains BV/nerves
Endo: around each myocyte-small BV and neuronal branches

Question 23

Types of Striated Muscle: Cardiac

Answer 23

1. Involuntary control
2. Branched
3. Single-centrally located nuclei (some bi-nucleated)
4. Arranged end-to-end (held in place by intercalated discs)
5. Numerous and large mitochondria/glycogen stores

Question 24

Smooth Muscle

Answer 24

1. Central nucleus
2. Elongated fusiform cells with tapered ends
3. Sarcoplasm: pinocytotic vesicles, Dense bodies which form attachment sites for thin and intermediate filaments (desmin/vimentin)

Question 25

What do Smooth Muscles secrete?

Answer 25

1. Connective tissue matrix 2. Synthesize both **Type III/IV** collagen 3. Vascular/Uterine secrete **Type 1 collagen/elastin**

Question 26

Calponin | Smooth Muscle

Answer 26

Block myosin binding sites

Question 27

Caldesmon | Smooth Muscle

Answer 27

Block myosin binding sites

Question 28

Caveolae

Answer 28

Invaginations in the sarcolemma of Smooth muscle -resembles T-Tubules of striated muscle

Question 29

Skeletal Muscle Response to Injury

Answer 29

Limited capacity of regeneration No regen capacity for cardiac tissue

Question 30

Smooth Muscle response to injury

Answer 30

Lots of differentiation and divinding from mesenchymal stem cells