Lec 4 Muscle tissue

Question 1

What are the 3 types of muscle tissue

Answer 1

Skeletal/Striated voluntary
Cardiac/Striated involuntary
Smooth/non striated involuntary

Question 2

What tissue is skeletal muscle surrounded by

What is skeletal muscle composed of (struc)

Answer 2

Skeletal muscle surrounded by epimysium

Composed of many muscle fascicles

Question 3

What are muscle fascicles surrounded by

What is it composed of

Answer 3

Muscle fascicles are surrounded by perimysium

Composed of muscle cells - muscle fibres

Question 4

What are muscle fibres surrounded by

What does it contain

Answer 4

Muscle fibres surrounded by endomysium

Composed of filamentous proteins, myofibrils

Question 5

How is muscle bound to tendon

Answer 5

Collagen fibres in epi/peri/endomysium connect to tendon

Question 6

How tendon-bone attach

Answer 6

Collagen fibres in tendon interwoven with periosteum

Then cemented in matrix as perforating/sharpey’s fibres

Question 7

How muscles get nerve and blood

Answer 7

BV and nerves form neurovascular bundle that branch in CT to reach individual fibres

Question 8

How do muscle cells form

Answer 8

Muscle cells develop from the fusion of myoblasts (mesodermal cells)
Skeletal muscle cells are multinucleate
Some myoblasts remain unfused to become satellite cells to provide some repair potential
- but usually dmg muscle replaced by fibrous tissue

Question 9

How are muscle cells bound and why is it impt

Answer 9

Muscle fibers bound by endomysium and is not in direct contact with adjacent cells
But since is bound all by endomysium and CT, force is transferred so whole muscle contracts

Question 10

Explain components of thin filament

Answer 10

Composed of actin
G-actin (globular): active site and binds myosin heads
F-actin: filamentous polymer of 300-400 G actin
Tropomyosin: covers actin active site
Troponin: Holds the tropomyosin in place

Question 11

Explain components of thick filament

Answer 11

Composed of 2 elongated proteins - has a head and tail
500 of these bundled to form a thick filament
myosin heads spiral around

Question 12

How are the myofilaments arranged in a sarcomere

Answer 12

Each thick filament is surrounded by 6 thin filaments

Adjacent thick filaments can share thin filaments as one of their 6

Question 13

Sarcomere nomenclature

Answer 13

Z line: attachment for thin filaments, the midd line
M line: attachment for thick filamnets, the mid line
Zone of overlap: thick and thin filament parts
H zone: Thick filaments only
I band: Thin filaments only
A band: length of thick filament

Question 14

Parts of the NMJ

How does signal pass

Answer 14

Synaptic terminal, Synaptic cleft, motor end plate
Synaptic vesicles in the terminal has ACh and is released onto the motor end plate binding AChRs (ligand gated ion ch) - depol sarcolemma
AChE clears ACh

Question 15

Explain muscle contraction

Answer 15

Cells actively maintain low Ca levels
ACh release, AP goes down sarcolemma and t-tubes to get close and stim SR release of Ca.
Incr in cyto Ca binds troponin and tropomyosin slides off active sites for myosin heads to bind (crossbridging)
Myosin heads cock back and contracts muscle

Question 16

Explain muscle relaxation and why is it passive

Answer 16

Ca will be pumped when signal dies
- back into SR and ECF
Troponin unbinds Ca and tropomyosin slides back on
Muscular relaxation is passive from elasticity of tissue, antagonist muscles, gravity

Question 17

How many NMJ in a muscle fibre

What is a motor unit

Answer 17

ONE NMJ in each muscle fibre
A motor unit is a single motor neuron and ALL the muscle fibre it innervates
- # of muscle fibre/unit varies: small motor in eyes, for
small movements OR large motor units in antigravity
muscles (thighs)
- Force proportional to # of motor units

Question 18

Explain muscle tone and how it functions

Answer 18

Resting tension in muscle - active motor units generate tension but not enough to shorten muscle
Avoids fatigues by rotating motor unit activation
Antigravity muscles for posture and balance

Question 19

Give characteristics of Slow twitch muscle
Capillary supply, myoglobin content, color, mitochondria, glycolytic enzymes, Cross sec diameter, tension, fatigue resistance, substrate for atp

Answer 19

Capillary supply: High supply
Myoglobin content: High 
Color: Red
Mitochondria: lots 
Glycolytic enzymes: Low []
Cross sec diameter: Small
Tension: Less
Fatigue resistance: High
Substrate for atp: Carbs, Lipids, Protein

Question 20

Give characteristics of Fast twitch muscle
Capillary supply, myoglobin content, color, mitochondria, glycolytic enzymes, Cross sec diameter, tension, fatigue resistance, substrate for atp

Answer 20

Capillary supply: Low supply
Myoglobin content: Low 
Color: Paler
Mitochondria: Fewer
Glycolytic enzymes: High []
Cross sec diameter: Large 
Tension: Greater
Fatigue resistance: Low
Substrate for atp: Glycogen

Question 21

Explain what occurs from muscle hypertrophy

Answer 21

Increases: mito, glycogen reserve, [] of glycolytic enzymes, myofibrils and myofilaments
increases ATP capacity
Not more cells, cells get bigger

Question 22

Cardiac muscle characteristics

Answer 22

Only in heart - striated involuntary muscle
Mononuclear, smaller than skeletal muscle
Cardiocytes form branching networks, joined at intercalated discs

Question 23

Intercalated junc charcteristics

Answer 23

Has fingerlike projections: incr SA for better attachment
Gap juncs for intercellular comm - contact SIDE TO SIDE of muscle cells
FASCIA Adherens for anchorage of actin filaments and terminal sarcomeres
Desmosomes for connection of IFs of cytoskeleton
Pacemaker cells set rate - controlled by ANS

Question 24

Cardiomyocytes characteristics

Answer 24

Aerobic metabolism - myoglobin, mito, cap network

Cannot regenerate

Question 25

Smooth muscle tissue characteristics

Answer 25

Small spindle shaped 
non striated, involuntary -  modulated by ANS
Signal spread by gap juncs
Can regen
Elongated nuclei centrally placed