Muscle

Question 1

How is force produced

Answer 1

Produced by movement of actin fibres over myosin fibres

With aid of a number of accessory proteins

Question 2

What are the four muscle cell types

Answer 2

Skeletal/voluntary 
Cardiac 
Smooth invol
Myoepthelial 
Myofibroblasts
Pericytes

Question 3

What are the non contractile cells in muscle

Answer 3

Myofibroblasts
Myoepthelial
Pericytes

Question 4

What is myoepthelial

Answer 4

Found associated with the secretory units of some exocrine glands
They are flattened cells and hve contractile protein arrangement similar to smooth muscle

Question 5

What are myofibroblasts

Answer 5

Characteristic of both fibroblasts (secrete collagen) and smooth muscle cells
Normally few in number and inconspicuous they enlarge and prolif in injury
Collagen for scaffold for repair they contract the wound

Question 6

What are pericytes

Answer 6

Inconspicuous cells found in around capillaries and venules

Act as stem cells but also contractile

Question 7

What is skeletal muscle

Answer 7

Skeletal
Voluntary
Straited

Question 8

What is muscle tissue

Answer 8

Formed from muscle cells and associated connective tissue and forms nulk of muscles

Question 9

What are the features of skeletal muscle

Answer 9

Striated 
Unbranched 
Multinucleate 
Fibres long cyclinders 
Nuclei at periphery sarcolemma

Question 10

What are fascicles

Answer 10

Muscle fibres are grouped into bundles called fascicles

Question 11

What are the different types of connective tissue associated with skeletal muscle organisation

Answer 11

Ct around muscle as a whole - epimysium
Ct around single fascicle - perimysium
Ct around single muscle fibre - endomysium

Question 12

What are sarcomeres

Answer 12

Unit of contraction of muscle cell smallest contractile element
Hundreds arranged end to end form myofibril

Question 13

What does striated mean

Answer 13

Fibres have a regular pattern bands running across

True for cardiac muscle

Question 14

What is a motor unit

Answer 14

Motor neurone and all the muscle fibres that it innervates

Question 15

What does a motor neurone end in

Answer 15

A motor end plate

Question 16

What happens at the motor end plate

Answer 16

Neuromuscular junction where there is a synapse where the action of acetylcholine occurs and initiates an action potentioa in the sarcolemma

Question 17

What are T-tubules

Answer 17

Within muscle fo the cell network of tubules

Extend from sarcolemma into cell surrounding myofibril

Question 18

What is the sarcoplasmic reticulum

Answer 18

Muscle cell contains labyrinth of specialised cells sarcoplasmic reticulum
Contains very high conc of calcium

Question 19

What is a triad

Answer 19

T tubule with sarcoplasmic reticulum form triad

Question 20

What is the stimulus leading to contraction

Answer 20

Action potential arrives at neuromuscular junction acetylcholine released results in action potential in muscle cell
Muscle action potential travels along sarcolemma and invades t tubules at triads release calcium lead to action on myosin fibres shortening sarcomeres and contraction

Question 21

What are the three types of skeletal muscle fibre

Answer 21

Type 1 - relatively slow contracting fibres that depend on oxidative metabolism, abundant mitochondria resist fatigue and produce relatively less force red fibres

Type 2A - intermediate between other two and these fibres relatively uncommon

Type 2B - relatively fast connecting fibres that depend on anaerobic metabolism, few mitochondria, fatigue easily and produced greater force called white fibres

Question 22

What su the myotendinous junction

Answer 22

Specialised junction where collagen fibres of tendon attaches to end of muscle fibres
Here muscle fibres tightly anchored to collagen by complex interdigitations

Question 23

How is feedback referred

Answer 23

Muscle has special sense organs
Muscle spindle contain special muscle fibres referred to as intrafusal fibres
Normal contractile muscle fibres termed as extrafusal fibres

Question 24

What su smooth muscle

Answer 24

Involuntary or visceral

No striations

Question 25

What is focal densities

Answer 25

Actin and myosin fibres do not go instant ions or organised like so but do converge on focal densities T periphery of cell

Question 26

What is cardiac muscle

Answer 26

Forms major part of walls of heart etc 
Skeletal muscle, cardiac muscle has striations less prominent 
Fibres much shorter 
Single nucleus near centre of fibre
Intercalated discs

Question 27

What is a dyad

Answer 27

In cardiac muscle t tubule and sarcoplasmic reticulum

Question 28

What are cardiac myocytes

Answer 28

Intrinsic rhythmic contraction
Gap junctions in intercalated discs allow for synchronisation of contraction between cells and allow wave of excitation to sweep through tissue
Rhythm independant of autonomic nervous system but modulated by it

Question 29

What are satellite cells

Answer 29

Skeletal muscle retains population of myoblasts which are satellite cells
Small quiescent cells pressed to sides of sarcolemma under nasal lamina
Form new muscle fibres

Question 30

How are cells specialised for contractile force

Answer 30

All cells contain contractile fibres in cytoskeleton

In muscle cells the cytoplasm packed with such fibres and cells highly specialised for contraction force