Lecture 7

Question 1

What is the primary function of the Endoplasmic Reticulum in skeletal muscle cells?

Answer 1

Abundant for calcium storage

Question 2

What are Myofibrils?

Answer 2

Large tubes that are the contractile elements inside the muscle cell

Question 3

What characteristics define skeletal muscle cells?

Answer 3

Multinucleated with many mitochondria for efficient energy production

Question 4

What is the Neuromuscular Junction?

Answer 4

An important connection point between nerves and muscles

Question 5

What role do muscles play in body function?

Answer 5

Crucial for normal body function, including maintaining core temperature

Question 6

What are ligaments?

Answer 6

Connect bone to bone, examples include Patellar ligament, ACL, MCL

Question 7

What is the primary function of tendons?

Answer 7

Typically connect muscle to bone, fastening skeletal muscle to a bone

Question 8

What happens to the Achilles tendon if it is cut?

Answer 8

The attached muscle recoils and ‘balls up’ due to loss of optimal length

Question 9

What is the top-down organization of muscle?

Answer 9

Overall Muscle, Fasciculi, Individual Muscle Fibers, Myofibrils, sacromeres

Question 10

What are the components of Myofibrils?

Answer 10

Primarily made of actin and myosin, located beneath the cell wall

Question 11

What gives muscles a striated appearance?

Answer 11

The alternating structural setup of thin (actin) and thick (myosin) filaments

Question 12

What are A bands?

Answer 12

Heavy bands primarily composed of myosin

Dark

Composed of 2 heavy chains , 4 lights chains (2 essential and 2 regulatory)

Question 13

What are I bands?

Answer 13

White bands composed of actin

Light

Composed of 2 f actin, and 2 tropomyocin

Question 14

What is a sarcomere?

Answer 14

The functional unit of a skeletal muscle, consisting of myofibrils lined up end to end

Z-disk to z-disk

Z disk- titin- actin- myosin- actin- titin- z-disk

Question 15

Describe the structure of thick filaments.

Answer 15

Formed by many myosin molecules wrapped/twisted together

Question 16

What are the two types of chains in a myosin molecule?

Answer 16

Two Heavy Chains and four Light Chains

Question 17

What is the function of the Essential Light Chain?

Answer 17

Contains ATPase activity for cycling ATP to move the myosin head

Question 18

What is the role of the Regulatory Light Chain?

Answer 18

Determines the activity level and speed of the myosin head

Question 19

What is a cross-bridge?

Answer 19

The interaction/connection between myosin heads and thin (actin) filaments

Question 20

How do smooth and skeletal muscle differ in myosin head regulation?

Answer 20

Smooth muscle can extensively regulate its myosin heads; skeletal muscle has minimal external manipulation

Question 21

What is the composition of thin filaments?

Answer 21

Consist of four strands including 2 F-actin and 2 tropomyosin

Question 22

What is the function of tropomyosin in muscle contraction?

Answer 22

Covers active sites on F-actin when the muscle is at rest

Question 23

What is the role of the troponin complex?

Answer 23

Unwinds tropomyocin once bound to calcium

Responsible for ‘unhiding’ the active sites on actin

Tropomyosin I,C,T

Question 24

What is the function of Troponin C?

Answer 24

Has a binding site for calcium that causes conformational change to expose active sites

Question 25

What happens during the 'binding' phase of cross-bridge cycling?

Answer 25

Cocked myosin head binds to an exposed active site on actin

Question 26

What occurs during the 'power stroke' phase?

Answer 26

The myosin head changes orientation, pulling the actin filament

Question 27

What is rigor mortis?

Answer 27

Occurs after death due to lack of ATP, causing myosin heads to bind to actin without detaching

Question 28

What is the H zone?

Answer 28

An area within the A band where there is only myosin

Question 29

What is the function of Z discs in muscle structure?

Answer 29

Anchoring points for neighboring myofibrils, connecting adjacent myofibrils

Question 30

What is the role of titin in muscle structure?

Answer 30

Anchors myosin to the Z disk, providing elasticity and preventing sarcomeres from falling apart

Question 31

What happens to cardiac sarcomeres when the heart is at rest?

Answer 31

Typically under-stretched due to low pressure or inadequate filling

Question 32

What is the Frank-Starling law?

Answer 32

Stroke volume increases in response to increased volume of blood filling the ventricles

Question 33

What are anchoring points for neighboring myofibrils?

Answer 33

Z disks ## Footnote Z disks connect adjacent myofibrils and help contain the force or shortening that occurs.

Question 34

What is the H-zone in muscle anatomy?

Answer 34

Area with only A bands. M line is right in middle. A singular unit with an M line, can be referred to as both zone and band.

Question 35

What happens to myofibrils when muscles are exercised?

Answer 35

Increase in the size of myofibrils.

Question 36

How quickly do skeletal muscles regenerate or duplicate?

Answer 36

Very slowly.

Question 37

What is the effect of disuse on myofibrils?

Answer 37

Loss of myofibrils can occur after a few days of inactivity.

Question 38

What happens to skeletal muscle cells during paralysis?

Answer 38

Loss of myofibrils and eventually loss of skeletal muscle cells.

Question 39

What is the primary characteristic of Type 1 skeletal muscle?

Answer 39

Redder, darker muscle with lots of myoglobin.

Question 40

What is myoglobin?

Answer 40

An oxygen transfer protein found inside Type 1 muscle cells.

Question 41

What distinguishes Type 2 skeletal muscle?

Answer 41

Faster twitch muscles, lighter color, less myoglobin.

Question 42

What is an example of Type 2 muscle in poultry?

Answer 42

Chicken breast.

Question 43

What is the main function of the soleus muscle?

Answer 43

Supports weight for long periods of time.

Question 44

What is the sarcolemma?

Answer 44

The wall of skeletal muscle.

Question 45

What is the role of T-tubules in muscle cells?

Answer 45

Allow action potential to move to deep parts of muscle cells.

Question 46

What is stored in the endoplasmic reticulum of muscle cells?

Answer 46

Calcium.

Question 47

What happens during muscle contraction when calcium is released?

Answer 47

Calcium binds to troponin C, unraveling thin filaments and revealing active sites.

Question 48

What is the function of the SERCA pump?

Answer 48

Pumps calcium back into the sarcoplasmic reticulum.

Question 49

What initiates the action potential in skeletal muscle?

Answer 49

Acetylcholine (ACh) release from the motor neuron.

Question 50

What is the end plate potential?

Answer 50

Local depolarization at the neuromuscular junction.

Question 51

True or False: The end plate potential always generates an action potential.

Answer 51

True.

Question 52

What is the role of acetylcholinesterase in muscle contraction?

Answer 52

Degrades acetylcholine to terminate the signal.

Question 53

What happens when calcium binds to calsequestrin?

Answer 53

It decreases the concentration of calcium within the cell.

Question 54

What is the length-tension relationship in muscle physiology?

Answer 54

Tension developed varies based on sarcomere orientation. Optimal stretch gives optimal force Under/over stretch = minimal to no contraction

Question 55

What occurs when a sarcomere is overstretched?

Answer 55

No force can be generated.

Question 56

What is the optimal sarcomere orientation for force generation?

Answer 56

Position C, where tension developed is 100%.