muscle physiology 1.0

Question 1

properties of muscle

Answer 1

electrical excitability : electrical impulses along a tissue

contractility : cause force and make movement

extensibility : extend tissues without damaging them

elasticity : ability to return to original shape without damage after being extended

Question 2

types of muscle

Answer 2

skeletal

cardiac

smooth

Question 3

skeletal muscle

Answer 3

-elongated shape

-multiple nuclei thus referred to as muscle fiber

• large diameter (10-100um)
• length of up to 20cm

maintain function of large cells by retention of the nuclei from the original myoblasts

if damaged satelite cells will repair them. located b/w plasma membrane and basement membrane along length of muscle fibres

Question 4

muscle

Answer 4

number of skeletal muscle fibers bound together by connective tissue

Question 5

tendon

Answer 5

connective tissue consisting of collagen fibers. attach muscles to bones

Question 6

connective tissue components

Answer 6

superficial fascia : seperates skin from muscle

deep fascia : holds similar muscles together

Question 7

connective tissue components

Answer 7

Endomysium : inner cell -cover each muscle fibre or cell and seperate them from each other

Perimysium : wraps around group of muscle fibres (fascicles) -

Epimysium - goes all around, covers entire muscle

ALL FORM TENDON ** come together when they attach to the bone

Question 8

connective tissue components

Answer 8

tendon

aponeurosis : flat extension of the tendon, have it under abdominal muscles as well as back of head

Question 9

hierarchical structure in muscle

Answer 9

skeletal muscle→ fascicle→ muscle fibers (cells) → myofibrils : are the contractile unit of our muscles

Question 10

myofibrils consist of

Answer 10

filaments

length are the same

thick filaments = 16nm diameter

thin filaments : 8nm diameter

Question 11

thick filament

Answer 11

composed of protein myosin

• has 2 large polypeptide heavy changes and 4 small light changes
• they form 2 globular heads (cross bridges) and a long tail

-2 binding sites (actin and ATP)

Question 12

cross bridges (2 golublar heads)

Answer 12

• have actin (thin) binding sites and atp binding sites
• make contact with the thin filaments and exert force during muscle contraction

Question 13

thin filament

Answer 13

• mainly composed of protein actin. also protein nebulin, troponin and tropomyosin
• 1 binding site
• actin is a single polypeptide that polymerizes with other actin polypeptide

Question 14

actin

Answer 14

• helical arrangment
• binding site for myosin

bunch of molecules bound together

Question 15

nebulin

Answer 15

assembles thin filaments

Question 16

tropomyosin

at rest

Answer 16

blocks myosin-binding site on actin (at rest)

-long cord like thing

we cant contract when myosin binding site is covered

Question 17

troponin

Answer 17

has 3 binding sites

• actin (I, inhibitory)
• tropomyosin (T)
• Calcium (C) : when calcium present, troponin binds to it and allows tropomyosin to move off of myosin binding site allowing cross bidge?*

helps anchor tropomyosin

Question 18

sarcomere structure

Answer 18

• 1 unit of thick and thin filament pattern is a sarcomere
• includes 2 sets of thin filaments
• z line to z line

→ 1 A band + ½ I-band on each side

Question 19

m line

Answer 19

narrow dark band in centre of H zone,

protein that link together the central region of adjacent THICK FILAMENTS

Question 20

z line

Answer 20

network of interconnecting proteins

-anchors THIN FILAMENTS

Question 21

titin

Answer 21

elastic protein extends from z line to m line

-linked to the thick filaments

Question 22

A band

Answer 22

where the thick filaments are located

located in the middle of a sarcomere

has dark view because of thick filaments

Question 23

i band

Answer 23

light band between the ends if the A bands

-contains the portions of the thin filaments that do not overlap the thick filaments. bisected by z line

Question 24

h zone

Answer 24

narrow, light band in the centre of the A band where there is only thick filaments

Question 25

zone of overlap

Answer 25

overlap of thin and thick filaments M line runs right in the middle of it

Question 26

thick filaments

Answer 26

each one has **6 thin filaments** surrounding it making a _hexigonal shape_

Question 27

thick filaments

Answer 27

each one has 6 thin filaments surrounding it making a hexigonal hape

Question 28

around thin filaments

Answer 28

**triangle of thick filaments**

Question 29

sarcoplasmic reticulum

Answer 29

- main function of the SR is to **store calcium ions (Ca2+)** through the terminal cisternae (lateral sacs) endings of the SR - homologous (similar in structure) to the endoplasmic reticulum found in most cells. Forms a _sleeve-like series of segments around each myofibril_

Question 30

terminal cisternae

Answer 30

**enlarged regions of SR** - located at the _end of each segment of sarcoplamic reticulum_ - Each lateral sac contains calsequestrin which is a protein that **store and release calcium** when an AP course down the transverse tubules **-"lateral sacs"**

Question 31

calsequestrin

Answer 31

- _Ca2+ binding protein_ in the **terminal cisternae** - allows _storage_ of a large quantity of _Ca2+_ without having to transport it against a large concentration gradient - "calcium buffer"

Question 32

t-tubules (transverse tubules)

Answer 32

_-lie directly between the terminal cisternae of adjacent segments of the sarcoplasmic reticulum_ - continuous with the plasma membrane (called sarcolemma in muscle cells) - **AP's propagate** along surface membrane and also **travel throughout** the interior of the muscle fiber by way of the **t-tubules**

Question 33

t-tubules and terminal cisternae

Answer 33

**surround the myofibrils** at the region of the sarcomere where the **A bands and I bands meet**