Muscular System Part 2: structure of a skeletal muscle fiber

Question 1

plasma membane

Answer 1

sarcolemma

Question 2

= tunnel-like extensions of the sacrolemma

Answer 2

transverse tubules

Question 3

cytoplasm

Answer 3

sarcoplasm

Question 4

a cytoplasmic protein that binds oxygen

Answer 4

myoglobin

Question 5

a polymer of glucose

Answer 5

glycogen

Question 6

a network of membranous sacs around the myofibrils, stores calcium ions.

Answer 6

Sarcoplasmic Reticulum

Question 7

Contracts organelle

Answer 7

myofibrils

Question 8

Membranous sacs encircling each myofibril
Loaded with Ca++
Release of Ca++ triggers myofibril contraction

Answer 8

Sarcoplasmic Reticulum

Question 9

Generate force during contraction

Answer 9

Contractile proteins

Question 10

Switch the contraction process on and off

Answer 10

regulatory proteins

Question 11

Align the thick and thin filaments properly
Provide elasticity and extensibility
Link the myofibrils to the sarcolemma

Answer 11

structural proteins

Question 12

Thick filaments
Functions as a motor protein which can achieve motion
Convert ATP to energy of motion
Projections of each molecule protrude outward (___)

Answer 12

Myosin (Myosin Head)

Question 13

Thin filaments
molecules provide a site where a myosin head can attach
Tropomyosin and troponin are also part of the thin filament
In relaxed muscle
Myosin is blocked from binding to it
Strands of tropomyosin cover the myosin-binding sites
Calcium ion binding to troponin moves tropomyosin away from myosin-binding sites
Allows muscle contraction to begin as myosin binds to it

Answer 13

Actin

Question 14

Stabilize the position of myosin
accounts for much of the elasticity and extensibility of myofibrils
Extends from Z disc to M line

Answer 14

Titin

Question 15

Links thin filaments to the sarcolemma
links actin in outermost myofilaments to transmembrane proteins and eventually to fibrous endomysium surrounding the entire muscle cell
transfers forces of muscle contraction to connective tissue around muscle cell
genetic defects in this produce disabling disease muscular dystrophy

Answer 15

Dystrophin

Question 16

Covers myosin-binding sites, keeps myosin from engaging actin

Answer 16

tropomyocin

Question 17

Bind to tropomyocin
In the presence of Ca++, causes tropomyosin to uncover myosin binding sites, allowing contraction to begin.

Answer 17

Troponin

Question 18

The presence of Calcium ++ causes:

Answer 18

Myosin heads attach to and “walk” along the thin filaments at both ends of a sarcomere
Progressively pulling the thin filaments toward the center of the sarcomere
Leading to shortening of the entire muscle

Question 19

Hardening of muscles and stiffening of the body, beginning 3-4 hours after death
peaks 12 hours after death and then diminishes over the next 48 to 60 hours

Answer 19

rigor mortis

Question 20

Release of acetylcholine
Nerve impulse arriving at the synaptic end bulbs causes many synaptic vesicles to release ACh into the synaptic cleft

Answer 20

Step 1 of muscle contraction

Question 21

Activation of ACh receptors
Binding of ACh to the receptor on the motor end plate opens an ion channel
Allows flow of Na+ to the inside of the muscle cell

Answer 21

Step 2 of muscle contraction

Question 22

Production of muscle action potential
The inflow of Na+ makes the inside of the muscle fiber more positively charged triggering a muscle action potential
The muscle action potential then propagates to the SR to release its stored Ca++

Answer 22

Step 3 of muscle contraction

Question 23

Termination of ACh activity
Ach effects last only briefly because it is rapidly broken down by acetylcholinesterase (AChE)

Answer 23

Step 4 of muscle contraction

Question 24

Interface of the motor neuron and muscle fiber

Answer 24

neuromuscular jusnction

Question 25

Gap that separates the two cells

Answer 25

synaptic cleft

Question 26

Chemical released by the initial cell communicating with the second cell

Answer 26

Neurotransmitter

Question 27

Sacs suspended within the synaptic end bulb containing molecules of the neurotransmitter acetylcholine (Ach)

Answer 27

Synaptic vessels

Question 28

The region of the muscle cell membrane opposite the synaptic end bulbs
Contain acetylcholine receptors

Answer 28

motor end plate

Question 29

Blocks release of ACh from synaptic vesicles
No signal, no contraction….
May be found in improperly canned foods
A tiny amount can cause death by paralyzing respiratory muscles
used as a medicine as well

Answer 29

Botulinum toxin

Question 30

A plant poison used by South American Indians on arrows and blowgun darts
Causes muscle paralysis by blocking ACh receptors inhibiting Na+ ion channels
Derivatives are used during surgery to relax skeletal muscles

Answer 30

Curare

Question 31

Slow actions of acetylcholinesterase and removal of ACh
Can strengthen weak muscle contractions
Ex: Neostigmine
Treatment for myasthenia gravis
Antidote for curare poisoning
Terminate the effects of curare after surgery

Answer 31

Anticholinesterase