Muscle Tissue

Question 1

Classification of muscles?

Answer 1

Morphological -striated (sarcomeres) & non-striated (smooth)

Functional - voluntary & involuntary

Question 2

Types of muscle?

Answer 2

Skeletal - striated & voluntary
Cardiac - striated & involuntary
Smooth - non-striated & involuntary

Question 3

Function of skeletal muscle?

Answer 3

Human locomotion, posture, support viscera, guard entrance & exits, maintain body temperature, store nutrients

Question 4

What are the name of skeletal muscle cells & what do they look like?

Answer 4

Muscle fibres
Striated - elongated, multinucleated cells (multiple copies of genes - a lot of protein & enzymes needed for muscle contraction) - 100s-1000s surrounded by connective tissue to make muscle - nuclei located just inside sarcolemma

Question 5

What controls movement of skeletal muscle?

Answer 5

CNS

Question 6

What makes up a muscle

Answer 6

Muscle=organ - various types of tissue - skeletal muscle fibres, connective tissue (mysia), nerve tissue, blood vessels

Question 7

What are the layers of connective tissue in skeletal muscle called?

Answer 7

Mysia - epimysium, perimysium, endomysium

Question 8

What are the functions of mysia?

Answer 8

Support, structure, compartmentalisation

Question 9

Describe the epimysium?

Answer 9

Surround muscle - dense irregular collagenous tissue - structural integrity - separates muscles from other tissue - project inwards to sperate muscle fibres into groups called fasciculi

Question 10

What is a fasciculus?

Answer 10

pl: fasciculi - group of muscle fibres surrounded by perimysium

Question 11

Describe the perimysium?

Answer 11

Loose collagenous tissue around fasciculi - allows nervous system to excite specific part of muscle - limbs

Question 12

Describe the endomysium?

Answer 12

Collagen & reticular fibres - surrounding muscle fibres - EC fluid & nutrients supporting muscle fibres

Question 13

Explain vasculature & innervation of muscles?

Answer 13

Rich supply - nutrients, gas exchange, waste
Supplied by axon branch of somatic motor neuron

Question 14

Where does the word “sarco” come from?

Answer 14

Greek - Sark = flesh

Question 15

Definition: Myocyte/Muscle fibre

Answer 15

Muscle cell

Question 16

Definition: Sarcolemma

Answer 16

Plasma membrane

Question 17

Definition: Sarcoplasm

Answer 17

Cytoplasm

Question 18

Definition: Sarcoplasmic reticulum

Answer 18

Endoplasmic reticulum - stores, releases, & retrieves Ca2+ ions

Question 19

Definition: Sarcosome

Answer 19

Mitochondria

Question 20

Definition: Sarcomere

Answer 20

Functional unit (between 2 z-discs)

Question 21

Explain parts of a sarcomere?

Answer 21

2μm
A band (dark - anisotropic with polarised light -thick filaments)
I band (light - isotropic with polarised light - thin filaments only)
H-band (pale area in centre of A band - thick filaments only)
M-line (bisects H-band - anchor thick filaments)
Z-disc (bisects I band - anchor thin filaments - 2 sarcomeres meet)

Question 22

What makes up sarcomeres?

Answer 22

Myofilaments (actin (thin) & myosin (thick)) & regulatory proteins (troponin & tropomyosin) (thin filaments)

Question 23

Difference between contracted & relaxed sarcomere?

Answer 23

Relaxed - thin filaments don’t reach middle, thick filament don’t reach end
Contracted - filaments don’t shorten- z-discs closer together h-band & I-band shorten but A-band remains the same

Question 24

Explain Huxley’s Sliding Filament Theory

Answer 24

Myosin - ATP activated side projections(head) - cross-bridges form to actin - change in protein configuration generates movement triggered by energy from hydrolysis of ATP - another ATP molecule binds to myosin & releases actin - head group converted to original shape

Question 25

Explain smooth muscle function?

Answer 25

Continuous low-fare contraction - diffuse movement of entire muscle - independent of innervation

Question 26

Where is smooth muscle found?

Answer 26

Cardiovascular system, respiratory tract, GI Tract, urinary system, reproductive system

Question 27

Explain smooth muscle cells?

Answer 27

Spindle-shaped cells - no striations - single elongated central nucleus in widest part of cell (can be spiraled) - 30-200μm - bifurcated ends - eosinophilic cytoplasm

Question 28

Explain smooth muscle fibres?

Answer 28

Irregular branching fasciculi - functional contractile unit - fibres roughly parallel (thick part of 1 cell near thin part of another)

Question 29

What is between smooth muscle fasciculi and tissue fibres?

Answer 29

Network of collagenous tissue

Question 30

Explain smooth muscles?

Answer 30

Layers at right angle to each other (circular & longitudinal) - allows waves of contraction to propel substances through lumen (peristalsis) - outer longitudinal layer separated from inner circular layer by minimal supportive tissue (collagen, cells with large pale nuclei = parasympathetic ganglion)

Question 31

What modulates intensity of peristalsis?

Answer 31

Parasympathetic nervous system

Question 32

How does smooth muscle contract?

Answer 32

Actin & myosin filaments criss-cross tissue & are anchored to focal densities (fastened to sarcolemma) - cross-bridges regulated to calmodulin proteins - Ca2+ ions bind to calmodulin - this complex activates enzyme myosin kinase activates myosin head via phosphorylation - pull thin filaments which pulls dense bodies which pull intermediate filament in the sarcoplasm - end of fibres pulled inwards & midsection bulges

Question 33

Name of the protein that regulates smooth muscle contraction?

Answer 33

Calmodium proteins

Question 34

Explain the shapes of relaxed & contracted muscle cells?

Answer 34

Relaxed - elongates Contracted - globular

Question 35

Where is Cardiac muscle found?

Answer 35

Heart - pump blood in circulatory system

Question 36

What is another name for cardiac muscle?

Answer 36

Myocardium

Question 37

Explain the structure of cardiac muscle?

Answer 37

Striated & contain sarcomeres (same banding as skeletal muscle) - short fibres (1-2 central nuclei) - branched network - cells separated by intercalated discs (gap junctions & desmosomes - allow contraction simultaneously & part of sarcolemma)

Question 38

What is the functional unit of cardiac muscle called?

Answer 38

Syncytium

Question 39

Explain importance of gap junction?

Answer 39

Polarising current caused by cations passing from cell to cell - electrical coupling - quick transmissions of action potential & coordinated contraction of heart - forms syncytium

Question 40

Explain the importance of desmosomes?

Answer 40

Anchor cells together