phase 1 week 6 Flashcards Preview

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Flashcards in phase 1 week 6 Deck (47):
1

What are the general functions of muscles?

movement
heat production
posture

2

What are muscle fibres coated with?

endomysium

3

What are fascicles?

groups of muscle fibres

4

What are fascicles bound by?

perimysium

5

What are muscles covered by?

epimysium

6

Describe skeletal muscles

long cylindrical cells
many nuclei
striated
voluntary
rapid contractions

7

Describe cardiac muscle

branching cells
1 or 2 nuclei
striated
involuntary
medium speed contractions

8

Describe smooth muscle

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

9

What are some defining features of skeletal muscle?

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

10

What is a sarcomere?

from Z line to Z line

11

What is the A band?

The length of the myosin filament

12

What is the I band?

The regions with no myosin

13

What is the H zone?

The central region where there is no actin filaments

14

What connects myosin to the Z band?

titan

15

Give a summary of muscle excitation and contraction

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

16

What is a motor unit?

All the muscle cells that are controlled by one nerve cell

17

Give examples of some motor unit ratios

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

18

What is muscle tonus?

tightness of a muscle
some fibres always contracted

19

What is tetany?

sustained contraction of a muscle
result of rapid succession of nerve impulses

20

What is the refractory period?

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

21

What is muscle atrophy?

weakening and shrinking of a muscle
may be caused by immobilisation or loss of neural stimulation

22

What is muscle hypertrophy?

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

23

What is isometric contraction?

produces no movement
used in sitting, standing, posture

24

What is isotonic contraction?

produces movement
used in walking, moving any part of the body

25

Describe electrochemical gradient

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

26

What is resting membrane potential?

The electrical gradient across the cell membrane

27

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

between -40 to -90mV

28

Describe how K+ ions contribute to resting membrane potential

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)

29

What is equilibrium potential?

the point at which the electrical gradient opposes the chemical gradient

30

What is the E of K+?

-90mV

31

How do Na+ ions contribute to resting membrane potential?

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

32

What is the equilibrium potential of Na+?

+60mV

33

Describe the resting membrane potential in real cells

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

34

What types of collagen are found in tendon?

mainly type I
small amounts of types III and IV

35

What are tendon fascicles held together by?

endotenon

36

what surrounds some tendons?

paratenon

37

What is synovium that surrounds tendons called?

tenosynovium

38

what surrounds endotenon?

epitenon

39

what is endotenon continuous with?

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

40

What is the function of paratenon?

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

41

which tendons are vascular?

those surrounded by paratenon

42

which tendons are avascular?

those surrounded by synovial sheaths

43

what is the key property of tendons?

high tensile strength

44

what are the functions of tendons?

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

45

What are satellite cells?

myoblasts that remain unfused after embryonic development

46

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

they can still undergo mitosis

47

What are the three stages of muscle regeneration?

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