Muscle Tissue, Growth, and atrophy

Question 1

what stimuli can cause a change in tissue?

Answer 1

changes in physical demand

change in metabolic demand

change in endocrine demand

Question 2

what is hypertrophy?

Answer 2

increase in cell size

Question 3

what is hyperplasia?

Answer 3

increase in cell number

Question 4

when does hypertrophy occur without hyperplasia?

Answer 4

in skeletal muscle with extra work

The adult skeletal muscle cannot produce new muscle cells (no hypertrophy

Question 5

how can skeletal muscle cells under go hypertrophy?

Answer 5

sarcomere expansion (increase in number of myofibrils)

More sarcoplasmic reticulum

More nuclei

*often all things will occur at the same time

Question 6

how do skeletal muscles develop?

Answer 6

Myoblasts are precursors of muscle cells that proliferate during development

These fuse to form muscle cells

genes can influence degree of proliferation

Myostatin slows myoblast proliferation

Question 7

what is a myoblast?

Answer 7

precursor muscle cells that proliferate during development that fuse to form muscle cells

Question 8

what is myostatin?

Answer 8

slows myoblast proliferation

Question 9

what happens when myostatin expression is affected?

Answer 9

Mutated myostatin gene leads to more skeletal muscle fibres being produced during development

Question 10

what is an example of cardiac hypertrophy?

Answer 10

Mice that swim have bigger hearts

Mice with aortic restriction also have bigger hearts

Question 11

what is the pathology of myocardium hypertrophy?

Answer 11

Large, often polyploid nuclei

Thickened ventricular wall reduces outflow and impairs relaxation phase.

Question 12

what can cause hypertrophy of smooth muscle?

Answer 12

obstruction of the bladder or intestine leads to hypertrophy of smooth muscle

Question 13

when does hyperplasia with hypertrophy occur together?

Answer 13

cells in pregnant uterus are enlarged and have larger nuceli reflecting their increased protein synthesis. The number of cells also increases

Question 14

what is involution?

Answer 14

when the uterus returns to normal size by physiological atrophy

Question 15

what is cell atrophy?

Answer 15

reduced cell size

Question 16

what is involution of tissue?

Answer 16

reduced cell number

Question 17

what are some examples of cell atrophy?

Answer 17

1. disuse atrophy occurs from a lack of physical exercise (reversible)
2. Severe types of muscle atrophy is neurogenic atrophy. Occurs when there is injury or disease to a nerve. Tends to occur more suddenly than disuse

Question 18

what reduction in anabolic hormones can cause muscle atrophy?

Answer 18

Testosterone
Growth hormone
IGF1

Question 19

does aging cause muscle atrophy?

Answer 19

yes

Question 20

what mechanisms underlye atrophy and involution?

Answer 20

Autophagy in cell atrophy

Apoptosis- programmed cell death

Question 21

what is macroautophagy?

Answer 21

cellular component identified

creates autophagosome

Fuses with lysosome, where enzymes cause degradation

Question 22

what mediates apoptosis?

Answer 22

mediated by caspases which exist in all cells as inactive procaspases. Activated by cleavage by other caspases.

Question 23

what activates apoptosis?

Answer 23

initiated by extracellular or intracellular death signals

Question 24

what is apoptosis?

Answer 24

Apoptosis is an important mechanism in developing and adult tissues for eliminating cells that are no longer needed

Question 25

what are some examples of apoptosis?

Answer 25

Elimination of cells after hormonal growth stimulus (oestrogen sensitive tissues) Elimination of cells in tissues with a high cell turnover (lining epithelia in the gut) Removal of excess cells in embryogenesis (fingers, gut lumen)

Question 26

what is the function of protease during apoptosis?

Answer 26

cell shrinkage Loss of surface specialisations Condensed chromatin

Question 27

what is the degradation phase of apoptosis?

Answer 27

The cell splits up into smaller fragments called apoptotic bodies The nucleus also fragments Each fragment contains viable mitochondria and intact organelles

Question 28

what is the phagocytic phase of apoptosis?

Answer 28

Apoptotic fragments are regognised and phagocytosed by adjacent cells where they are destroyed Some fragments degenerate extracellularly Some fragments are ingested by phagocytic cells

Question 29

what is an example of physiological muscle hypertrophy?

Answer 29

skeletal muscle changes with exercise

Question 30

what is an example of pathological muscle hypertrophy?

Answer 30

cardiac muscle hypertrophy

Question 31

what is an example of hyperplasia and hypertrophy?

Answer 31

increased size of the myometrium during pregnancywhat do

Question 31

what is an example of hyperplasia and hypertrophy?

Answer 31

increased size of the myometrium during pregnancy

Question 32

what is an example of hyperplasia and hypertrophy?

Answer 32

increased size of the myometrium during pregnancy

Question 32

what is an example of hyperplasia and hypertrophy?

Answer 32

increased size of the myometrium during pregnancywhat do

Question 33

what is an example of hyperplasia and hypertrophy?

Answer 33

increased size of the myometrium during pregnancywhat do

Question 33

what is an example of hyperplasia and hypertrophy?

Answer 33

increased size of the myometrium during pregnancy