Lecture 8 - Skeletal Muscle

Question 1

4 Functions of Skeletal Muscle

Answer 1

Movement
Posture
Storage/Movement of Substances
Heat Generation

Question 2

Gross Muscle Anatomy (3 points)

Answer 2

Force produced by muscle
Force transmitted to skeleton via tendon
Movement occurs/joint stabilizes

Question 3

Sarcomere Definition

Answer 3

Moving Parts of Muscle

Question 4

Epimysium Definition

Answer 4

Outer Connective Tissue
Holds Fascicals in place

Question 5

Endomysium Definition

Answer 5

Connective Tissue holding muscle fibres together

Question 6

Perimysium Definition

Answer 6

Inner Connective Tissue holding fascicals in place

Question 7

6 Components of a Muscle Fibres

Answer 7

Multiple Nuclei
Light I Band
Dark A Band
Myofibril
Sarcolemma
Mitochondria

Question 8

Number of Sarcomeres in a Myofibril

Answer 8

Thousands joined in series/parallel to one another

Question 9

Components of Sarcomere

Answer 9

Z Line
H Zone
M Line
Light I Band
Dark A Band

Question 10

2 types of Myofilaments

Answer 10

Thick Myosin Filament
Thin Actin Filament

Question 11

2 Features of Actin Filaments

Answer 11

Double Helical Structure
Tropomyosin covers binding sites on Actin units

Question 12

Features of Myosin Filaments

Answer 12

300 Myosin Units long
Two subunits - S1/S2

Question 13

2 Subunits in Myosin Filaments

Answer 13

S1 - Globular Head
S2 - Flexible Region and Tail

Question 14

Why are binding sites in thin filament covered?

Answer 14

Stops unwanted contraction

Question 15

3 Structural Proteins in Sarcomere

Answer 15

Titin
Nebulin
Desmin

Question 16

Titin Function

Answer 16

Springlike protein responsible for returning sarcomere to original structure

Question 17

Nebulin Function

Answer 17

Maintaining Overall Structure

Question 18

Desmin Function

Answer 18

Maintains Z Line

Question 19

Sliding Filament Mechanism (5 points)

Answer 19

During Contraction:
H Zone decreases in length
I Band decreases in length
A Band stays the same
Overall change in muscle length

Question 20

Sarcoplasmic Reticulum Definition

Answer 20

Interconnecting tubules surrounding myofibrils

Question 21

2 Functions of Sarcoplasmic Reticulum

Answer 21

Regulates intracellular levels of Ca2+
Stores Ca2+ and releases on stimulation to allow contraction

Question 22

Cross Bridge Cycle (7 points)

Answer 22

Action Potential Arrives
Ca2+ binds to Troponin
Causes conformational change in Tropomyosin
Exposes binding site of actin
Myosin Globular head binds to actin binding site using ATP
Pi released from Myosin Globular Head
ATP used to break Actin/Myosin Bond

Question 23

Length/Tension Relationship in Muscle (3 points)

Answer 23

When filaments overlapped, no tension
As muscle stretches, tension increases as Z Line is not there
Once actin and myosin aren’t overlapped, tension decreases

Question 24

Force/Velocity Relationship in Muscle (3 points)

Answer 24

Force during shortening < isometric force
Faster the movement, less time myosin heads have to attach to binding site
Force during lengthening > isometric force

Question 25

3 types of Muscle Fibres

Answer 25

Type I Type IIA Type IIX

Question 26

Features of Type I Fibres

Answer 26

Small Cross Sectional Area Red High Endurance Capacity Low Max Force

Question 27

Features of Type IIA Fibres

Answer 27

Medium Cross Sectional Area Pink Intermediate Endurance Capacity Intermediate Max Force

Question 28

Features of Type IIX Fibres

Answer 28

Large Cross Sectional Area White Low Endurance Capacity High Max Force

Question 29

6 Parts to Motor Neuron

Answer 29

Cell Body Myelin Sheath Axon Dendrites Node of Ranvier Axon Terminal

Question 30

Node of Ranvier Definition

Answer 30

Gap in Myelin Sheath where axon is exposed

Question 31

Components of Node of Ranvier

Answer 31

Sodium and Potassium Channels in Membrane

Question 32

Neuromuscular Junction Definition

Answer 32

Where motor neuron meets muscle fibre

Question 33

Muscle Spindle Function

Answer 33

Prevents Overstretching of Muscles due to changes in muscle length

Question 34

Mechanism of Overstretch Prevention

Answer 34

Afferent Neuron wraps around muscle spindle Efferent Neuron causes muscle spindle to contrat