Introduction to Muscle

Question 1

Syncytium

Answer 1

Multinucleate cell

Question 2

What forms myobfibrils

Answer 2

Myofibrils are formed by thousands of sarcomeres lined up at their Z lines

Question 3

Why is SkM Striated

Answer 3

The regular arrangement of thick myosin, thin actin and Z-lines

Question 4

Describe the Length-Tension relationship of skeletal muscle

Answer 4

An inverted U relationship between sarcomere length and tension

If the sarcomere is shortened too much, there will be no tension as the myosin heads are far from the ends of actin which bind to the heads, and if it is too extended, the distance between myosin heads and actin is too far. There is an ideal optimal resting length where the tension is maximised as the myosin heads fit well into the actin

Question 5

Label this cross section of a SkM fibre

Answer 5

**Fat is needed to be burnt for energy

Question 6

What is the name of heart muscle cells

Answer 6

Cardiomyocytes

Question 7

Why are muscles in the heart wall arranged in spiral like structures

Answer 7

The wringing motion empties out the chambers more effectively, similarly to drying a dish cloth

Question 8

How are cardiac muscle cells arranged

Answer 8

Single mono or di-nucleated cells with limb like extensions that connect to neighbouring cells and form fibre-like networks that produce force in a certain direction

**Like members of a human puramid

Question 9

Are cardiomyocytes mono-nucleate or syncytial

Answer 9

Mono-nucleate

**Can bi bi-nucleate but generally not considered syncytial

Question 10

What is the role of intercalated disks

Answer 10

Connecting neighbouring cardiomyocytes

Question 11

Discuss the cross-striative properties of cardiomyocytes

Answer 11

They have centrally located nuclei and extensions which serve to connect them to neighbouring cells via intercalated disks

Question 12

Does a cross section of the ventricular wall show longitudinal or cross sectioned cells?

Answer 12

Both lol get bamboozled

Question 13

Does the heart have fibres?

Answer 13

It does not have fibres, instead the cells are linked to one another

Question 14

Cardiac Muscle

Answer 14

Question 15

Discuss the relationship of cardiomyocytes to basement membranes

Answer 15

Each cardiac muscle cell

has a basement membrane

Question 16

How is information transmitted through intercalated disks

Answer 16

Gap junctions which allow the transfer of action potentials along cardiomyocytes

Question 17

Role of Desmosomes on Intercalated disks in cardiomyocytes

Answer 17

Desmosomes allow longitudinal force transfer by creating strong adherence between cells

Question 18

Why are intercalated disks very bumpy

Answer 18

Expanded surface area

Question 19

Compare the length of cardiomyocytes to skeletal muscle fibres

Answer 19

Cardiomyocytes are much shorter

Question 20

Do Cardiomyocytes have myofibrils and where are the nuclei

Answer 20

Cardiomyocytes are filled with shorter myofibrils that have nuclei in the middle of the cells

Question 21

Discuss the amount of mitochondria and degree of capillarisation in Heart Cells

Answer 21

Heart cells have more mitochondria than smooth muscle cells or skeletal muscle fibres and are better capillarised

Question 22

How are myosin heads arranged in smooth muscle

Answer 22

They are arranged in an antiparallel manner at opposite sides of the filament in smooth muscle

Question 23

Describe the alternative of sarcomeres used in smooth muscles

Answer 23

3D networks of Actin filaments linked to myosin, held together by dense bodies that are attached to other actomyosin groups and also intermediate filaments

Question 24

Effect of SM contraction on length and diameter

Answer 24

SM contraction shortens the cell to a fraction of its relaxed length while extending its diameter

Question 25

Answer 25

Question 26

Compare contraction in smooth muscle to that in skeletal/cardiac muscle

Answer 26

Much greater contraction in smooth (around 5x) compared to skeletal/cardiac (around 2-2.5x)

Question 27

Where are the nuclei placed in a smooth muscle cell and where are the mitochondria in relation to them

Answer 27

Nuclei tend to be in the middle, often surrounded by mitochondria

Question 28

What is in between smooth muscle cells

Answer 28

Collagen fibres

Question 29

Qualitatively compare the thickness of smooth and skeletal muscle fibres

Answer 29

Skeletal muscle fibres are much thicker

Question 30

Compare the shape of the 3 types of muscle cells

Answer 30

Skeletal muscle is made of individual long multinucleated fibres, cardiac is made of a network of interconnected cells and smooth muscle is made of bundles of spindle shaped cells

Question 31

How do the different muscle types extend

Answer 31

SkM: Antagonistic muscles or generally gravity
Cardiac: Blood pressure
Smooth muscle: Pressure in the tube

Question 32

Which muscle type has the highest power

Answer 32

Skeletal Muscle

Question 33

Antagonists of SkM, Cardiac Muscle and SM

Answer 33

Skeletal Muscles: Mostly antagonist muscles, in some cases gravity
Cardiac Muscle: Blood pressure, atrium for ventricle
Smooth Muscle: Tube pressure