Muscles

Question 1

Define Muscle

Answer 1

Muscle is soft tissue which cells are rich of protein filaments actin and myosin that slide past one another, producing contraction

Question 2

Functions of muscle (3)

Answer 2

• maintaining and changing of posture
• locomotion
• movement of the internal organs (contraction of heart, movement of food, breathing through diaphragm)

Question 3

3 types of muscles:

Answer 3

skeletal

smooth

cardiac

Question 4

Morphology of skeletal muscles:

Answer 4

Cells called myosites

Single cells organised into long fibres (myofibrils)

Multi nuclear cells

Question 5

Morphology of cardiac muscle tissue:

Answer 5

Cells called cardiomyosites

Branching structure

Uni or mononuclear cells

Question 6

Morphology of smooth muscle tissue:

Answer 6

Uni or mononuclear cells

No sarcomeres

Question 7

Syncytium

Answer 7

Refer to multinucleate cells that can result from multiple cell fusions of uninuclear cells

May also refer to cells interconnected by specialised membrane with gap junctions

Question 8

Structural syncytium example

Answer 8

Skeletal

Question 9

Functional syncytium

Answer 9

Cardiac and smooth muscles

Question 10

Skeletal myofibrils characteristics

Answer 10

most attached to bones by tendons

multinucleate

myofibrils are striated (repeating functional units)

fibres are surrounded and bundled by connective tissue

Question 11

Cardiomyocyte

Answer 11

abundant reserve of myoglobin

each cell is in contact with adjacent cells at specialised sites - intercalated discs

plenty of mitochondria

Question 12

What are intercalated discs?

Answer 12

Specialized intercellular attachment of cardiac muscle cells compromising gap junctions

Question 13

What are intercalated discs made up from?

Answer 13

Gap junctions - allow for direct communication between cells through diffusion of small molecules and ions

Desmosomes - fasteners through the plasma membrane of adjacent cells by intermediate filaments composed of keratin/desmin to form a dense plaque.

• provide strong adhesion

Question 14

What is a sarcomere?

Answer 14

A repeating functional unit of a myofibril or cardiomyocyte.

about 10,000 of them per myofibril.

Question 15

Length of sarcomere?

Answer 15

2-2.2 micrometres long

Maximum is 2.6
Very stable length

Question 16

What bands is a sarcomere made up from? (2)

Answer 16

• A band (dark band) thick myosin filaments

- I band (light band) thin filaments with NO thick.

Question 17

What is the M line in a sarcomere?

Answer 17

The protein to which the thick filaments attach; centre of sarcomere.

Question 18

What is the H zone in a sarcomere?

Answer 18

Thick filaments with NO thin.

Question 19

What is the Z disk in the sarcomere?

Answer 19

Filamentous network of protein, attaches actin myofilaments.

Question 20

What are the Titin filaments in a sarcomere?

Answer 20

Accessory proteins that keep thick and thin filaments aligned.

elastic chains of polypeptides.

Question 21

What are thick filaments made of?

Answer 21

Myosin fibrillar protein

Question 22

What are thin filaments made of?

Answer 22

Actin globular protein

Question 23

What is an actomyosin complex?

Answer 23

Protein complex composed of actin and myosin.

Question 24

Types of skeletal muscles:

Answer 24

• red muscle (high mitochondrial content)
• mixed muscle (medium amount)
• white muscle (low mitochondria content)

Question 25

Red muscle (skeletal) facts: (4)

Answer 25

• aerobic energy release
• high density of capillaries /mitochondria / myoglobin
• slow, lasts for long with little fatigue
• their fuel are fats or carbohydrates

Question 26

White muscle facts

Answer 26

• anaerobic energy release
• fuel are carbohydrates
• low density of capillaries / mitochondria / myoglobin
• fast, fatigue develops quickly

Question 27

Give an example of a slow twitch fibre and a fast twitch:

Answer 27

Slow twitch = red fibres

Fast twitch = white fibres