Muscle Tissue

Question 1

What are muscle tissues?

Answer 1

Soft tissue specialised for conversion of chemical energy into mechanical energy (specialised for contraction)

Question 2

What are the functions of skeletal muscle?

Answer 2

• Voluntary movement of skeleton
• Movement of eye/tongue
• Sub-conscious movement to maintain posture and balance

Question 3

What is the structure (main features) of skeletal muscle?

Answer 3

• Un-branched cylindrical cells (muscle fibres)
• Multiple peripherally located nuclei
• Striated appearance

Question 4

What is the striated appearance in skeletal muscle caused by?

Answer 4

The arrangement of contractile proteins (myofibrils)

Question 5

Where is endomysium located in skeletal muscles?

Answer 5

• Around individual muscle fibres

Question 6

What are fasciculi in skeletal cells?

Answer 6

Groups of muscle fibres that are grouped together

Question 7

Where is perimysium located in skeletal muscles?

Answer 7

• Around each fasciculi

Question 8

Where is epimysium locates in skeletal muscles?

Answer 8

• Around entire muscle cell

Question 9

What spreads through the connective tissues of skeletal muscle?

Answer 9

• Blood vessels and nerves

Question 10

What is skeletal muscle cell structure highly specialised for?

Answer 10

Contraction/relaxation

Question 11

What is each myofibril in skeletal muscle separated from each other by?

Answer 11

Sarcoplasm

Question 12

What is the specialised plasma membrane called in skeletal muscle?

Answer 12

Sarcolemma

Question 13

What is a myofibril?

Answer 13

Any of the elongated contractile threads found in striated muscle cells

Question 14

Why are numerous mitochondria found between myofibrils in skeletal muscle?

Answer 14

• As muscle requires a lot of energy to contract

Question 15

What is the name for the repeating units myofibrils are composed of?

Answer 15

Myofilaments

Question 16

What are thick myofilaments composed of in skeletal muscle and what colour are they?

Answer 16

• Composed of myosin

- Appear dark in colour

Question 17

What are thin myofilaments composed of in skeletal muscle and what colour are they?

Answer 17

• Composed of actin

- Appear light in colour

Question 18

What are the light bands in skeletal muscle bisected by?

Answer 18

Z lines

- Z lines divide each myofibril into contractile units called sarcomeres (functional contractile units of muscle)

Question 19

What mechanism do sarcomeres contract by?

Answer 19

Sliding filament mechanism

Question 20

What is the sliding filament mechanism?

Answer 20

• ATP energy allows myosin to bind to actin

- A conformational change causes the filaments to slide over each other causing the sarcomere to shorten (contract)

Question 21

What innervates skeletal muscle?

Answer 21

Somatic motor neurones

- Individual motor neurones innervate several muscle fibres

Question 22

What is a ‘motor unit’?

Answer 22

A single motor neurone together with all the muscle fibres it innervates

Question 23

How are membranous T tubules formed in skeletal muscle?

Answer 23

Sarcolemma invaginates into sarcoplasm

- Continuous with extracellular space

Question 24

What is sarcoplasmic reticulum?

Answer 24

• Network of tubules associated with T tubules and wrapped around myofibrils
• Ca2+ concentrated with SR (specialised for storage of calcium)

Question 25

What are the functions of cardiac muscle?

Answer 25

- Only found in the heart - Specialised for continuous autonomous contractions - Pump blood through the CVS

Question 26

What is the structure of cardiac muscle?

Answer 26

- Elongated, branched cylindrical cells - 1 or 2 centrally located nuclei - Similar arrangement of contractile proteins as in skeletal muscles causes striated appearance

Question 27

What are the 3 layers of the heart wall?

Answer 27

- Pericardium - Myocardium - Endocardium

Question 28

What is the pericardium?

Answer 28

- Outer supporting tissue layer

Question 29

What is the myocardium?

Answer 29

- Cardiac muscle tissue

Question 30

What is the endocardium?

Answer 30

- Single layer of endothelial cells

Question 31

What are the specialised intercellular junctions that anchor adjacent cardiac cells together?

Answer 31

Intercalated disks

Question 32

What are the 5 similarities between skeletal tissue and cardiac tissue?

Answer 32

- Identical arrangement of sarcomeres - Contain T tubules and sarcoplasmic reticulum - Numerous mitochondria - Glycogen and lipid granules - Contraction by sliding filament mechanism

Question 33

What are the 5 differences between skeletal muscle and cardiac muscle?

Answer 33

- Cardiac muscles uses autonomous (involuntary contraction) compared to skeletal which is voluntary - Cardiac muscles SR slowly leaks Ca2+ - Cardiac muscle has intercalated disks - Modified cardiac muscle cells are known as the conducting system - Modulated by external autonomic/hormonal stimuli e.g. in times of stress

Question 34

Is cardiac muscle under voluntary or involuntary control?

Answer 34

involuntary

Question 35

What controls the rate of heartbeat in heart?

Answer 35

- Sinoatrial node (pacemaker cells)

Question 36

What is the process of the conducting system of the heart?

Answer 36

- Initiated by SA node - L and R atria contact - AV node - AV bundle (bundle of His) - Purkinje fibres - Cardiac muscle fibres

Question 37

What do modified cardiac muscles consist of?

Answer 37

- Fewer myofibrils | - No T tubules, no intercalated discs

Question 38

What is the involuntary contraction of cardiac muscle caused by?

Answer 38

- Intrinsic/spontaneous contractile ability * Pacemaker cells (SA node) * Slow release of Ca2+ from SR

Question 39

What is the rate of inherent rhythm in cardiac muscle modulated by?

Answer 39

- Autonomic nervous stimulation | - Hormonal stimulation

Question 40

What are the functions of smooth muscle?

Answer 40

- Found lining hollow organs - Specialised for continuous contractions - Typically to proper lumen contents - peristalsis

Question 41

What is the structure of smooth muscle?

Answer 41

- Spindle-shaped cells with tapered ends - Single centrally located nuclei - No sarcomeres hence no striations

Question 42

What is peristalsis?

Answer 42

Movement of food through GI tract

Question 43

What are the 2 layers of smooth muscle in the GIT?

Answer 43

- Inner circular | - Outer longitudinal

Question 44

What does the inner circular layer of smooth muscle do?

Answer 44

- Constricts lumen diameter

Question 45

What does he outer longitudinal layer of smooth muscle do?

Answer 45

- Shortens length

Question 46

What modulates the intensity of peristalsis?

Answer 46

Parasympathetic NS

Question 47

Does smooth muscle contain sarcomeres?

Answer 47

No

Question 48

Does smooth muscle contain actin and myosin filaments?

Answer 48

Yes

Question 49

In what way are actin and myosin arranged in smooth muscle?

Answer 49

- In a criss-cross lattice

Question 50

What is actin and myosin anchored to cytoplasm and the cell membrane via in smooth muscle?

Answer 50

Focal densities

Question 51

Explain the relaxed and contracted state of smooth muscle cells?

Answer 51

- In the relaxed state the cell is elongated - With contraction actin and myosin interact by filament sliding - Muscle cell becomes shortened and globular

Question 52

What is contractility in smooth muscle and what is it initiated and modulated by?

Answer 52

- Intrinsic property of smooth muscle - Initiated by stretch - Modulated by autonomic nervous system and/or hormonal stimulation

Question 53

What are peristalsis pacemaker cells called?

Answer 53

Interstitial cells of Cajal