1.05 - Muscle

Question 1

What are the three types of muscle?

Answer 1

Skeletal
Smooth
Cardiac

Question 2

Group the three types of muscles based on voluntary/involuntary action

Answer 2

Involuntary:
- Cardiac
- Smooth
Voluntary:
- Skeletal

Question 3

Group the three muscle types based on presence or absence of striations

Answer 3

Striated:
- Skeletal
- Cardiac
Non-striated:
- Smooth

Question 4

What is the sarcolemma?

Answer 4

The Plasma Membrane of skeletal muscle

Question 5

What is the Sarcoplasm?

Answer 5

The cytoplasm of skeletal muscle

Question 6

What is the sarcoplasmic reticulum?

Answer 6

Endoplasmic reticulum of skeletal musce

Question 7

What is the skeletal muscle belly surrounded by?

Answer 7

Epimysium

Question 8

What are fascicles and what are they surrounded by?

Answer 8

A fascicle is a bundle of skeletal muscle fibres and is surrounded by perimysium, a type of connective tissue.

Question 9

What are muscle fibres and what are they surrounded by?

Answer 9

Muscle fibres are the individual muscle cells and are surrounded by endomysium
Each muscle fibre is contractile.
Contains myofibrils which are made up of contractile filaments

Question 10

What are some distinctive features of skeletal muscle cells?

Answer 10

Extremely elongated
Multinucleated (peripherally located nuclei)
Basic 5 sided structure

Question 11

What are the two types of Skeletal Muscle?

Answer 11

Type 1: Slow Contraction

Type 2: Fast Contraction

Question 12

Describe Type 1 Skeletal Muscle

Answer 12

Slow contraction
Aerobic, using oxidative phosphorylation
Contain many mitochondria
Cell contain large amount of myoglobin (O2 storage)
 - Red in colour
Many capillaries

Question 13

Describe Type 2 Skeletal Muscle

Answer 13

Fast contraction
Anaerobic, using glycolysis
Therefore rich in glycogen
White in colour

Question 14

Describe the Myofibrils

Answer 14

Muscle fibres contain myofibrils
They are elongated cylindrical structures made up of contractile proteins
Cross striations of striated muscle is due to the ordered arrangement of these proteins

Question 15

List and describe the bands in the myofibrils

Answer 15

I Band: Light. Made up of thin actin filaments
A Band: Dark. Made up of thick myosin filaments
Z Band = Black. Z-Band to Z-Band outlines the sarcomere, anchor points of the actin filaments, and represents the contractile unit.

Question 16

Describe the Innervation of Skeletal Muscle

Answer 16

Voluntary Muscles

• Motor innervation
• Sensory innervation: maintain posture, coordinates voluntary movement
• Sympathetic innervation: regulate blood flow via effect on vascular smooth muscle

Question 17

What is a motor unit?

Answer 17

The combination of a motor neuron and the muscle fibres it supplies.
The nerve and all supplied muscle fibres fire as a unit

Question 18

Describe the transmission of signals to Skeletal Muscle

Answer 18

Neuron action potential causes release of acetylcholine at the neuromuscular junction. ACh binds to receptor and results in an action potential at the motor end plate –> spread of depolarisation throughout the sarcolemma

Question 19

Describe the structure of Skeletal muscle as it relates to function

Answer 19

T - Tubules - extensions of the sarcolemma allow depolarisation to enter the cell.
Sarcoplasmic reticulum - modified endoplasmic reticulum releases Ca2+ ions –> this activates contraction of myofibrils

Question 20

Describe a pathological condition associated with Skeletal Muscle

Answer 20

Duchenne’s Muscular Dystrophy
X-linked recessive
Abnormalities in the gene encoding dystrophin protein. it normally concentrates at the plasma membrane over Z bands where it links to cytoplasmic actin

Question 21

Describe Smooth Muscle

Answer 21

Not striated
Involuntary
Autonomic and Hormonal control
Visceral structures
Enables continual contractions of low force

Question 22

Describe Smooth Muscle Cells

Answer 22

Spindle shaped
Have a single central oval nucleus
Cells form irregular branching fascicle, which are the functional contractile units
Do not have myofibrils as in skeletal muscle and therefore no striations
But have filaments made of myosin and actin

Question 23

Instead of Z-Bands what do smooth muscle cells have?

Answer 23

Dense Bodies (focal densities): which act as anchor points in the cytoplasm
Attachment junctions: Act as anchor points on the cell membrane

Question 24

Describe the contraction of Smooth Muscle Cells

Answer 24

During contraction, due to the crisscross arrangement of contractile proteins, the cell shortens and becomes ‘plump’

Question 25

What are the two types of Smooth Muscle?

Answer 25

Single Unit | Multi-unit

Question 26

Describe Single Unit Type Smooth Muscle

Answer 26

Smooth muscles cells have extensive communications via gap junctions with adjacent cells so that the cells contract as a single unit Found in the GIT and uterus

Question 27

Describe Multiunit Type Smooth Muscle

Answer 27

Each smooth muscle cell acts independently from its neighbour. Thus type of muscle behaves like multiple independent cells or groups of cells. Capable of finer control. Found in the ciliary muscle of the eye, piloerector muscles of the skin

Question 28

What is the classification system for Smooth Muscle and what are the subtypes?

Answer 28

By activity pattern: Phasic Tonic

Question 29

Describe Phasic Smooth Muscle

Answer 29

Smooth muscle exhibiting rhythmic or intermittent activity. Often single unit type GIT or Urogenital

Question 30

Describe Tonic Smooth Muscle

Answer 30

Continuously active, maintaining a level of "tone" Often multiunit type Blood vessels

Question 31

Describe a pathological condition that affects smooth muscle

Answer 31

Familial Visceral Myopathy Common cause of chronic primary intestinal pseudo-obstruction Segmental dilation of the digestive tract and urinary bladder Degenerating muscle cells Smooth muscle fibrosis

Question 32

Describe the basic features of Cardiac Muscle

Answer 32

Cardiac myocytes have features similar to both skeletal and smooth muscle. Striated Involuntary Strong and continual contractions

Question 33

Describe the structure of cardiac myocytes

Answer 33

Elongated cells Central nuclei Branching fibres with intercalated discs Contractile proteins arranged similarly to skeletal muscle. Cross striations Contractile units: sarcomeres made of myosin and actin but also contain troponin and tropomyosin T-Tubules and Sarcoplasmic reticulum similar to that of skeletal muscle

Question 34

What are intercalated discs?

Answer 34

Specialised junctions Permit rapid spread of contractile stimuli due to areas of low electrical resistance --> fibres contract almost simultaneously Coincide with Z lines

Question 35

What are the three types of membrane contact that Intercalated discs are made up of?

Answer 35

``` Fascia Adherens (site of actin insertion) Desmosomes (anchorage for intermediate filaments) Gap junctions (pores with low electrical resistance, enabling ion and molecule transfer between the cells --> coordinated contraction) ```

Question 36

Describe a pathological condition that affects cardiac muscle

Answer 36

``` Cardiomyopathies Myocardial dysfunction due to disease of myocardial muscle. - Dilated cardiomyopathy - Hyperthrophic cardiomyopathy - Restrictive cardiomyopathy ```

Question 37

Compare the location of the three muscle types

Answer 37

Skeletal: skeleton, tongue, eye Smooth: Vessels, Organs Cardiac: Heart

Question 38

Compare the presence of striations in the three muscle types

Answer 38

Skeletal: Yes Smooth: No Cardiac: Yes

Question 39

Compare the features of the nucleus in the three muscle types

Answer 39

Skeletal: Multiple and peripheral Smooth: Single and central Cardiac: Single and central

Question 40

Compare the Cell-To-Cell communication in the three muscle types

Answer 40

Skeletal: None Smooth: Gap Junctions Cardiac: Intercalated Discs

Question 41

Compare the Innervation of the three muscle types

Answer 41

Skeletal: Voluntary Smooth: Involuntary Cardiac: Involuntary