lecture 17 - muscle histology

Question 1

What are the 3 types of muscle?

Answer 1

skeletal, cardiac, smooth

Question 2

What are the 2 types of striated muscle?

Answer 2

skeletal, cardiac

Question 3

What are the 2 types of involuntary muscles?

Answer 3

cardiac, smooth

Question 4

What are the units within a skeletal muscle, from biggest to smallest?

Answer 4

muscle, fascicle, muscle cell/fibre, myofibril, myofilaments

Question 5

Are skeletal muscle fibres branched or unbranched?

Answer 5

unbranched

Question 6

What is the shape and orientation of muscle cell nuclei?

Answer 6

oval, periphery, multiple nuclei

Question 7

What is the term for the cytoplasm of a muscle cell?

Answer 7

sarcoplasm

Question 8

What is the term for the plasma membrane of a skeletal muscle cell?

Answer 8

sarcolemma

Question 9

What is the outer layer of a muscle cell?

Answer 9

basal lamina

Question 10

What is the basil lamina of a muscle cell?

Answer 10

A connective tissue/collagen covering on top of hte sarcolemma

Question 11

What is a skeletal muscle triad?

Answer 11

A group of 3 vessels that goes deep into the muscle fibre from the surface, made up of a T-tubule and 2 terminal cisternae of the sarcoplasmic reticulum

Question 12

What are the components of a skeletal muscle triad?

Answer 12

1 T-tubule, 2 terminal cisternae

Question 13

What are skeletal muscle T-tubules?

Answer 13

Invaginations of the sarcolemma that penetrate between the myofibrils in a transverse plane

Question 14

What are skeletal muscle terminal cisternae?

Answer 14

Expanded sacs of sarcoplasmic reticulum that penetrate in between the myofibrils

Question 15

Which sarcolemma band is a T-triad located at in skeletal muscle?

Answer 15

the A band

Question 16

What is the boundary of a sarcomere at each end?

Answer 16

Z line

Question 17

What is a sarcomere?

Answer 17

A single contractile unit of a myofibril

Question 18

What proteins make up myofibrils?

Answer 18

Actin (20%), myosin (60%), other proteins (20%)

Question 19

What is the I band of a sarcomere?

Answer 19

Isotropic band - The part of either side of a Z disc formed by non-overlapping parts of actin/thin filaments

Question 20

What is the A band of a sarcomere?

Answer 20

Anisotropic band - band with thick filaments plus the overlapping ends of thin filaments, including the H zone in the middle which just contains non-overlapping thick filaments.

Question 21

What is the H zone of a sarcomere?

Answer 21

The central non-overlapping zone of thick filaments in the middle of a sarcomere

Question 22

What is the line that marks the centre of a sarcomere?

Answer 22

M line

Question 23

How many neurones can innervate a single muscle cell?

Answer 23

Only 1

Question 24

What is the name for motor terminals of motor neurones on muscles?

Answer 24

Motor end plate

Question 25

What is the process of muscle contraction, from action potential to cross bridge cycling?

Answer 25

1.) action potential at neuromuscular junction / motor end plate 2.) depolarisation of sarcolemma 3.) propagation of depolarisation down T-tubules 4.) Ca2+ release from terminal cisternae 5.) Ca2+ binding to troponon, displacing tropomyosin and exposing myosin binding sites 6.) cross bridge cycle

Question 26

What happens to the length of the I band during contraction?

Answer 26

Shortens

Question 27

What happens to the length of the A band during contraction?

Answer 27

remains the same

Question 28

What happens to the length of the H band during contraction?

Answer 28

shortens

Question 29

What protein anchors actin to the outer basal lamina in a myofibril?

Answer 29

Dystrophin

Question 30

What protein is absent in Duchenne’s muscular dystrophy?

Answer 30

Dystrophin

Question 31

What are the 5 layers of connective tissue coverings of the layers within a muscle?

Answer 31

Outer to inner: Fascia, epimysium, perimysium, endomysium, basal lamina

Question 32

What type of collagen is found in the epimysium?

Answer 32

Collagen Type I

Question 33

What connective tissue layer contains muscle spindles?

Answer 33

Perimysium

Question 34

What connective tissue layer contains capillaries and nerve fibres?

Answer 34

Endomysium

Question 35

What connective tissue layer is the site of metabolic exchange?

Answer 35

The endomysium

Question 36

What is the function of muscle spindles?

Answer 36

They are mechanoreceptors essential for proprioception - sensitive to stretch

Question 37

Where are muscle spindles located?

Answer 37

In between muscle fascicles

Question 38

What connective tissue layer covers a muscle spindle?

Answer 38

A capsule, which is an extension of the perimysium

Question 39

What are the small muscle fibres within the fuse/spindle of a muscle spindle?

Answer 39

IFF - intrafusal fibres

Question 40

What are extrafusal fibres of a muscle spindle?

Answer 40

The normal muscle fibres found outside the capsule of a muscle spindle

Question 41

What is the process of muscle spindle activation?

Answer 41

muscle stretch causes change in muscle length, force converted to capsule, afferent nerve stimulation, transmission to spinal cord, extrafusal muscle activation and contraction

Question 42

What cells are found on the periphery of muscle fibres and aid in repair?

Answer 42

Satellite cells

Question 43

Where are muscle satellite cells located?

Answer 43

Periphery of muscle fibres, between sarcolemma and basal lamina

Question 44

Why are muscle satellite cells normally inactive?

Answer 44

They are involved in muscle repair, but only in early postnatal life or in acute injuries.

Question 45

What tissue makes up tendons?

Answer 45

Regular dense fibrous connective tissue

Question 46

What cells produce tendon matrix?

Answer 46

Tenocytes

Question 47

Where is the tendon blood/nutrient supply derived from?

Answer 47

The external connective or synovial tissue

Question 48

What is a myotendinous junction?

Answer 48

A place where muscle fibres and tendons interlock/attach

Question 49

How are muscles fibres and tendons attached at myotendinous junctions?

Answer 49

Specialised proteins connect actin of last sarcomere to sarcolemma, basal lamina and then tendon collagen

Question 50

What is an osteotendinous junction?

Answer 50

The point where tendons and bones are connected

Question 51

What allows bone and tendons to interlock at an osteotendinous junction?

Answer 51

Fibrous or fibrocartilaginous insertions