Histology Of Muscle

Question 1

What non-muscle cell is present in muscle connective tissue?

Answer 1

Fibroblasts

Question 2

What non-muscle cell is present in myoepithelia?

Answer 2

Exocrine epithelia

Question 3

Name one place where myoepithelia may be found

Answer 3

Salivary glands

Mammary glands

Question 4

What are the precursor cells of muscle cells?

Answer 4

Myoblasts

Question 5

What are the origins of myogenic precursors?

Answer 5

Somite

Mesenchyme of pharangeal arches

Question 6

What are the two lips of the dermamyotome, where do they migrate and what do they form? (Development)

Answer 6

Dorsal-medial lip cells migrate ventrolaterally to form myotome muscles/epaxial deep back muscles

Ventral-lateral lip cells migrate to limbs, hypaxial myotome and ventral body wall muscles

Question 7

Name the connective tissues in muscle in ascending density

Answer 7

Endomysium

Perimysium

Epimysium

Question 8

Where does the muscle connective tissue merge with the tendon?

Answer 8

Myotendinous junction

Question 9

What are myofibres grouped into? Describe the connective tissue involved in this structure

Answer 9

Fascicles - myofibres individually wrapped in endomysium and the fascicle is surrounded by perimysium

Question 10

Where are the nuclei in skeletal muscle cells?

Answer 10

Periphery of cell

Question 11

What does the A band consist of?

Answer 11

Thick myosin filaments overlapping actin

Question 12

What does the I band consist of?

Answer 12

Thin actin filaments

Question 13

What does the H zone consist of?

Answer 13

Thick myosin filaments (no overlap)

Question 14

What does the M line consist of?

Answer 14

Myosin cross-linking proteins

Question 15

What does the Z line consist of?

Answer 15

Actin cross-linking proteins

Question 16

What part of the sarcomeres demarcate a single sarcomere?

Answer 16

Z lines

Question 17

What do costameres do?

Answer 17

Link myofibrils to sarcolemma at Z lines

Question 18

What links adjacent myofibrils together?

Answer 18

Desmin (intermediate filament) with plectin at Z lines

Question 19

What is the motor end plate?

Answer 19

Specialised area on muscle fibre membrane where a nerve axon contacts to form a synapse

Question 20

What is a motor unit?

Answer 20

One motor neuron and all the muscle fibres it innervates

Question 21

Where are the motor units smaller?

Answer 21

Hand muscles

Eye muscles

Question 22

Where are fast myosin isoforms found?

Answer 22

White muscle fibres

Question 23

How much myoglobin do fast myosin isoforms have?

Answer 23

Small amount

Question 24

Describe the activity of fast myosin isoforms

Answer 24

Contract rapidly but quickly become fatigued

Question 25

Where are slow myosin isoforms found?

Answer 25

Red muscle fibres

Question 26

How much myoglobin do slow myosin isoforms have?

Answer 26

Lots

Question 27

Describe the function of slow myosin isoforms

Answer 27

Contract slowly but keep going for a long time (endurance)

Question 28

Are most muscles just one type of myosin fibre?

Answer 28

No, often mixtures of different types

Question 29

What type of myosin isoform do posture muscles in your back consist of?

Answer 29

Slow

Question 30

What type of myosin isoform do the muscles in your eyes consist of?

Answer 30

Fast

Question 31

Why do we have a tubular system in muscles?

Answer 31

Allows propagation of action potential throughout the muscle

Question 32

What do triads consist of?

Answer 32

2 outer = sarcoplasmic reticulum (terminal cisternae) Inner = T-tubule

Question 33

What does the sarcoplasmic reticulum have in its membrane (activated during depolarisation)?

Answer 33

Voltage-gated calcium ion channels

Question 34

Where are the triads located?

Answer 34

Each sarcomere has a pair of triads at the A-I borders

Question 35

What are muscle satellite cells?

Answer 35

Resident adult muscle stem cells

Question 36

What do muscle satellite cells become when activated?

Answer 36

Myoblasts

Question 37

What can satellite cells do for the muscle?

Answer 37

Produce new myonuclei for existing myofibres Fuse together to form new myofibres

Question 38

Where does cardiac muscle develop from?

Answer 38

Front end of embryo - cardiogenic mesoderm

Question 39

What are heart muscle cells called?

Answer 39

Cardio myocytes

Question 40

Where is the nucleus in a cardiac muscle cell?

Answer 40

Central

Question 41

What types of muscle are striated?

Answer 41

Skeletal and cardiac

Question 42

How are cardiac muscle cells connected?

Answer 42

Intercalated discs

Question 43

What are intercalated discs and what do they do?

Answer 43

Modified Z-lines Form a functional syncytium

Question 44

What are intercalated discs comprised of and why?

Answer 44

Desmosomes - hold cells together (intermediate filaments) Gap junctions - allows Ca2+ flow between cells Fascia adherens - hold cells together (actin)

Question 45

Why can the heart not regenerate after injury?

Answer 45

No satellite cells

Question 46

How does the heart contract? Where do the contractions originate from?

Answer 46

Atria - top-down Ventricles - bottom-up SAN

Question 47

How big are smooth muscle cells?

Answer 47

~5 microns/micrometres dia. 20-500 microns/micrometres in length

Question 48

What is the shape of a smooth muscle cell?

Answer 48

Spindle-shaped

Question 49

How are the actin and myosin filaments arranged in a smooth muscle cell?

Answer 49

Actin and myosin mesh work fills cytoplasm Actin tethered to cell surface by junctional complexes

Question 50

How do smooth muscle cells contract?

Answer 50

Twist and shorten like wringing out a flannel

Question 51

What are gap junctions for?

Answer 51

Allow electrical excitation to spread from cell to cell

Question 52

What are smooth muscle cells controlled by?

Answer 52

Hormones Sympathetic/parasympathetic innervation Histamines (allergic reactions)