phase 1 week 6

Question 1

What are the general functions of muscles?

Answer 1

movement
heat production
posture

Question 2

What are muscle fibres coated with?

Answer 2

endomysium

Question 3

What are fascicles?

Answer 3

groups of muscle fibres

Question 4

What are fascicles bound by?

Answer 4

perimysium

Question 5

What are muscles covered by?

Answer 5

epimysium

Question 6

Describe skeletal muscles

Answer 6

long cylindrical cells
many nuclei
striated
voluntary
rapid contractions

Question 7

Describe cardiac muscle

Answer 7

branching cells
1 or 2 nuclei
striated 
involuntary
medium speed contractions

Question 8

Describe smooth muscle

Answer 8

fusiform cells
1 nucleus
non-striated
involuntary
slow, wave-like movement

Question 9

What are some defining features of skeletal muscle?

Answer 9

plasma membrane = sarcolemma
cytoplasm = sarcoplasm
Smooth ER = sarcoplasmic reticulum
many more mitochondria
several nuclei
transverse (T) tubules - inward extensions of the sarcolemma
myofibrils made up from microfilaments

Question 10

What is a sarcomere?

Answer 10

from Z line to Z line

Question 11

What is the A band?

Answer 11

The length of the myosin filament

Question 12

What is the I band?

Answer 12

The regions with no myosin

Question 13

What is the H zone?

Answer 13

The central region where there is no actin filaments

Question 14

What connects myosin to the Z band?

Answer 14

titan

Question 15

Give a summary of muscle excitation and contraction

Answer 15

Nerve impulses reach neuromuscular junction
Acetylcholine is released from the motor neuron
Acetylcholine binds with receptors of the muscle membrane and allow Na+ entry
Na+ influx will generate an action potential in the sarcolemma
Action potential travels down the T-tubule
Sarcoplasmic reticulum releases Ca2+
Ca2+ binds with troponin and moves the troponin-tropomyosin complex
Binding sites on the actin filament are exposed
Myosin heads attach to binding sites and create a power stroke
ATP detaches myosin heads and energises them for another contraction
When action potentials cease the muscles stop contracting

Question 16

What is a motor unit?

Answer 16

All the muscle cells that are controlled by one nerve cell

Question 17

Give examples of some motor unit ratios

Answer 17

back muscles 1:100
finger muscles 1:10
eye muscles 1:1

Question 18

What is muscle tonus?

Answer 18

tightness of a muscle

some fibres always contracted

Question 19

What is tetany?

Answer 19

sustained contraction of a muscle

result of rapid succession of nerve impulses

Question 20

What is the refractory period?

Answer 20

brief period of time in which muscle cells will not respond to stimulus

Question 21

What is muscle atrophy?

Answer 21

weakening and shrinking of a muscle

may be caused by immobilisation or loss of neural stimulation

Question 22

What is muscle hypertrophy?

Answer 22

enlargement of a muscle
more capillaries
more mitochondria
caused by strenuous exercise and steroid hormones

Question 23

What is isometric contraction?

Answer 23

produces no movement

used in sitting, standing, posture

Question 24

What is isotonic contraction?

Answer 24

produces movement

used in walking, moving any part of the body

Question 25

Describe electrochemical gradient

Answer 25

the input of energy to transport ions across a membrane has created an electrical gradient The active transport of positive ions out of a cell has created a chemical gradient the combination of an electrical and chemical gradient is called an electrochemical gradient However, the cells remain in osmotic equilibrium The negative ion will try to move down the electrochemical gradient and follow the positive ion out of the cell, but the membrane inhibits its flow

Question 26

What is resting membrane potential?

Answer 26

The electrical gradient across the cell membrane

Question 27

What is the resting membrane potential in nerve and muscle cells?

Answer 27

between -40 to -90mV

Question 28

Describe how K+ ions contribute to resting membrane potential

Answer 28

The membrane is more permeable to K+ ions K+ leaks out of the cell down its concentration gradient Excess negative charge build up inside as Pr- cannot cross the plasma membrane An electrical gradient is formed The negative charges attract K+ ions back into the cell down the electrical gradient net movement of K+ stops at the equilibrium potential (E)

Question 29

What is equilibrium potential?

Answer 29

the point at which the electrical gradient opposes the chemical gradient

Question 30

What is the E of K+?

Answer 30

-90mV

Question 31

How do Na+ ions contribute to resting membrane potential?

Answer 31

membrane permeable to Na+ only | same principles hold as in K+ movement

Question 32

What is the equilibrium potential of Na+?

Answer 32

+60mV

Question 33

Describe the resting membrane potential in real cells

Answer 33

most cells are 40 times more permeable to K+ than Na+ The resting potential is closer to -70mV because a small amount of Na+ leaks into the cell The 3Na+ ions are pumped out and 2K+ ions are pumped in by Na+/K+-ATPase This is also known as an electrogenic pump because it helps maintain an electrical gradient

Question 34

What types of collagen are found in tendon?

Answer 34

mainly type I | small amounts of types III and IV

Question 35

What are tendon fascicles held together by?

Answer 35

endotenon

Question 36

what surrounds some tendons?

Answer 36

paratenon

Question 37

What is synovium that surrounds tendons called?

Answer 37

tenosynovium

Question 38

what surrounds endotenon?

Answer 38

epitenon

Question 39

what is endotenon continuous with?

Answer 39

the periosteum at the tendon-bone interface where collagen fibres enter the bone as Sharpey fibres

Question 40

What is the function of paratenon?

Answer 40

an elastic sheath allowing free gliding of the tendon against surrounding tissues

Question 41

which tendons are vascular?

Answer 41

those surrounded by paratenon

Question 42

which tendons are avascular?

Answer 42

those surrounded by synovial sheaths

Question 43

what is the key property of tendons?

Answer 43

high tensile strength

Question 44

what are the functions of tendons?

Answer 44

either generate joint motion during concentric contractions or resist joint motion during eccentric contractions

Question 45

What are satellite cells?

Answer 45

myoblasts that remain unfused after embryonic development

Question 46

why can satellite cells aid in the minor regeneration if damaged muscle?

Answer 46

they can still undergo mitosis

Question 47

What are the three stages of muscle regeneration?

Answer 47

Inflammatory response activation, differentiation and fusion of satellite cells maturation and remodelling of newly formed myocytes