Muscle Tissue

Question 1

What are the 3 types of muscle tissue?

Answer 1

1. Skeletal
2. Smooth
3. Cardiac

Question 2

Features of cardiac muscle

Answer 2

Striated and under involuntary control
Elongated, branched cylindrical cells
One or two centrally located nuclei

Question 3

Features of skeletal muscle

Answer 3

Striated and under voluntary control
Elongated cylindrical cells
Multiple, peripherally located nuclei

Question 4

Features of smooth muscle

Answer 4

Non-striated and under involuntary control
Small, elongated spindle-shaped cells with tapered ends
Single centrally located nuclei
No sarcomeres hence no striations

Question 5

What do tendons do?

Answer 5

Transfers force from muscles to bone to facilitate movement

Question 6

What is the endomysium?

Answer 6

Innermost layer of connective tissue that surrounds a muscle cell

Question 7

What is a bundle of muscle cells called?

Answer 7

A fascicle

Question 8

What is the perimysium?

Answer 8

Loose connective tissue that surrounds fascicles

Question 9

What is the epimysium?

Answer 9

Dense connective tissue that surrounds the whole muscle

Question 10

What is the function of skeletal muscle?

Answer 10

Specialised for contraction and relaxation

Question 11

Why do muscle cells have a striated appearance?

Answer 11

This is due to the arrangement of myofibrils

Question 12

What are myofibrils composed of?

Answer 12

Myofilaments - 2 types
Dark bands composed of myosin (A band)
Light bands composed of actin (I band)

Question 13

What are Z lines in myofilaments?

Answer 13

Z lines divide myofibrils into contractile units called sarcomeres. Z lines bisect light bands (actin)

Question 14

What is a sarcomere?

Answer 14

Contractile units of skeletal muscle
They contract by the sliding filament mechanism
Conformational change causes sarcomeres to slide over each other, resulting in sarcomere shortening

Question 15

What is a motor unit?

Answer 15

A nerve cell and all the muscle fibres it interacts with. An individual nerve cell can stimulate multiple muscle fibres

Question 16

What neurotransmitter is released at the NMJ?

Answer 16

Acetylcholine

Question 17

What is the sarcoplasm?

Answer 17

Specialised cytoplasm found only in muscle cells

Question 18

What is the sarcolemma?

Answer 18

Specialised plasma membrane of muscle cells. Invaginates the sarcoplasm forming T tubules.

Question 19

What is the sarcoplasmic reticulum?

Answer 19

A modified form of smooth endoplasmic reticulum. Contains Ca2+. The sarcoplasmic reticulum wraps around myofibrils in muscle cells.

Question 20

What happens when acetylcholine is released at the NMJ?

Answer 20

Signal enters through T tubules and delivered to sarcoplasmic reticulum causing it to release internal Ca2+ stores. This leads to muscle contraction.

Question 21

What is cardiac muscle (i.e. myocardium) specialised for?

Answer 21

Continuous autonomic contractions. Pumps blood through the CVS.

Question 22

What are the 3 layers of the heart wall?

Answer 22

Pericardium - outer supporting layer
Myocardium - thicker layer (muscle tissue)
Endocardium - single layer of endothelial cells

Question 23

What type of specialised intercellular junctions anchor adjacent cardiac cells together?

Answer 23

Intercalated discs

Question 24

What are the similarities between cardiac and skeletal muscle?

Answer 24

Striated appearance
Identical arrangement of sarcomeres
Contain T tubules and sarcoplasmic reticulum
Contraction by sliding filament mechanism

Question 25

What are some features in cardiac muscle that are not present in skeletal muscle?

Answer 25

Autonomous (involuntary) contraction
Sarcoplasmic reticulum slowly leaks Ca2+
Intercalated discs
Modified cardiac muscle cells known as the conducting system
Modulated by autonomic/hormonal stimuli

Question 26

Where would you find smooth muscle?

Answer 26

Lining hollow organs and blood vessels

Question 27

What is smooth muscle specialised for?

Answer 27

Continuous contractions

Typically to propel lumen contents - peristalsis

Question 28

Describe the smooth muscle arrangement in the gut and how this arrangement promotes peristalsis

Answer 28

Inner circular layer and outer longitudinal layer
Inner layer restricts the lumen diameter and outer layer restricts the length of the lumen
This squeezes food through the G.I tract

Question 29

What is peristalsis modulated by?

Answer 29

Parasympathetic nervous system

Question 30

Describe contraction in smooth muscle

Answer 30

No sarcomeres - actin and myosin arranged in a criss-cross lattice
Actin and myosin anchored to cytoplasm and cell membrane via focal densities
In a relaxed state, the cell is elongated
Muscle cell becomes shortened and globular during contraction