Fewell - Cardiac & Skeletal Muscle 2021

Question 1

Muscle types

Answer 1

• skeletal
• smooth
• cardiac

Question 2

how do the different types of muscles vary?

Answer 2

differ in:

• appearance
• function
• NS control

Question 3

skeletal muscle males vs females

Answer 3

-males 42%
-females 38%
(of body mass)

Question 4

how does the skeletal muscle act on the skeleton?

Answer 4

tendons

Question 5

specialized function of skeletal muscle

Answer 5

• movement
• posture
• heat production
• catabolism

Question 6

cardiac muscle specialized function

Answer 6

biomechanical pump powering the delivery of blood to lungs and tissues

Question 7

cardiac muscle found in

Answer 7

only the heart

Question 8

skeletal muscles appearance

Answer 8

• striated

- fibers (long & cylindrical)

Question 9

skeletal muscles # of nuclei

Answer 9

multiple

Question 10

skeletal muscles function dependent on ___

Answer 10

NS and voluntary with exceptions

Question 11

cardiac muscle apperaence

Answer 11

• striated

- fibers (short, branched and interconnected end-to-end)

Question 12

cardiac muscle # of nuclei

Answer 12

single

Question 13

cardiac muscles function depends on __

Answer 13

NOT NS, involuntary actions

Question 14

cardiac muscles are attached to __

Answer 14

heart skeleton or other muscle fibers

Question 15

what is a neuromuscular junction

Answer 15

the synapse formed between a somatic motor neuron and a skeletal muscle fiber

Question 16

final common pathway

Answer 16

• All movement is initiated through
activation of Lower Motor Neurons
whose cell body lies in the anterior
horn of the spinal cord. This has
been termed the final common
pathway (Sherrington, 1857-1952;
Nobel Prize in Physiology or
Medicine 1932).
• Motor neuron action potentials lead
to muscle contraction.
• A motor unit is one motor neuron
and all the muscle fibers it
innervates.

Question 17

Signal transmission at the neuromuscular junction
>receptor
>location of receptor
>neurotransmitter

Answer 17

Binding of ACh to nicotinic ACh receptors on the motor end-plate causes an
end-plate potential which in turn leads to a muscle action potential

Question 18

Excitation-contraction coupling What is it?

Answer 18

The process by which
electrical “excitation”
of the muscle surface
membrane triggers
muscle contraction

Question 19

role of calcium in cardiac and skeletal muscles

Answer 19

Intracellular Ca++ triggers and sustains contraction in
both skeletal and cardiac muscle but they differ in
mechanism by which depolarization of the sarcolemma
results in a rise in

Question 20

Skeletal Muscle muscle fascicle

Answer 20

Skeletal muscle is composed of bundles of ~20 to 80 muscle fibers called a muscle fascicle

Question 21

Skeletal Muscle muscle fiber

Answer 21

an individual, multinucleated muscle cell which is narrow (10-80 μm) but can
be up to 25 cm in length

Question 22

Skeletal Muscle myofibrils

Answer 22

Each muscle fiber contain ~20-40 bundles of filaments,

called myofibrils running along the axis of the cell

Question 23

Skeletal Muscle striations of myofibrils

Answer 23

e due to the arrangement

of thick and thin filaments of myosin and actin, respectively

Question 24

Skeletal Muscle sarcomeres occur between ____

Answer 24

segment that occurs between two dark lines (z-lines)

Question 25

Skeletal Muscle sarcomere

Answer 25

the basic unit of striated muscle tissue (causes contraction)

Question 26

Cardiac Muscle myocyte

Answer 26

e shorter, branched and interconnected from end to end by structures called Intercalated Disks

Question 27

Cardiac Muscle Intercalated Disks

Answer 27

Contain • Desmosomes (mechanical link) | • Gap Junctions (electrical link)

Question 28

Myofibril kinds of proteins

Answer 28

- contractile - regulatory - structural

Question 29

contractile proteins

Answer 29

(Actin & Myosin) – which generate force | during contraction

Question 30

Regulatory Proteins

Answer 30

(Troponin & Tropomyosin) – which help switch | the contraction process on and off

Question 31

Structural Proteins

Answer 31

which keep the thick & thin filaments in proper alignment; give the myofibril extensibility/elasticity, and; link the myofibrils to the sarcolemma and extracellular matrix

Question 32

thin filament

Answer 32

-made of actin arranged in helical formation (F action strands) have sites for myosin heads to bind

Question 33

myosin heads binding sites

Answer 33

- actin-binding | - ATP binding

Question 34

Contraction Cycle Step 1

Answer 34

Myosin head hydrolyzes ATP and becomes energized and oriented >ATP -> ADP

Question 35

Contraction Cycle Step 2

Answer 35

Myosin head binds to actin, forming a crossbridge | >phosphate leaves

Question 36

Contraction Cycle Step 3

Answer 36

Myosin crossbridge pivots, pulling the thin filament past the tick filament towards center of the sarcomere (power stroke) >ADP leaves

Question 37

Contraction Cycle Step 4

Answer 37

As myosin head binds ATP , the crossbridge detaches from actin

Question 38

sliding filament hypothesis

Answer 38

the mechanism of muscle contraction | > contraction cycle (power stroke)

Question 39

skeletal muscle force of contraction in a single fiber increase with ___

Answer 39

-increased with increasing motor neuron firing rate

Question 40

skeletal muscle force of contraction in a whole msucle increased by ___

Answer 40

-increased by recruiting additional motor units

Question 41

``` cardiac muscle force of contraction >___ contractions >no >all muscle ___ >CANNOT use _ ```

Answer 41

- graded contractions - no recruitment of fibers - all muscles in syncytium contract at once (when increased Ca2+ intracellular levels) - CANNOT use skeletal muscle strategy