Tissue Mechanics | Exam 2

what are the three muscle tissues

1. skeletal muscle tissue

2. cardiac muscle tissue

3. smooth muscle tissue

what does the skeletal muscle tissue do

• moves body by pulling on bones of the skeleton

what does the cardiac muscle tissue do

• contractions move blood through the blood vessels

• most enduring

what does the smooth muscle tissue do

• contractions move fluids and solids along digestive tract

• regulates the diameters of small arteries

skeletal/striated muscle fibers

• moves bones/limbs

• occur in muscles which are attached to the skeleton

• striated

• VOLUNTARY CONTROL

smooth muscle fibers

• in walls of hollow visceral organs, except the heart

• appear spindle shaped

• INVOLUNTARY CONTROL

• non-striated

cardiac muscle cells:

• form the walls of the heart

• INVOLUNTARY CONTROL

• striated

what are skeletal muscles composed of

• muscle fibers

• myofibrils

What does it mean that skeletal muscles are viscoelastic

• elastic: when a muscle is stretched and released it goes back to it’s original non-stretched size

• Viscous: internal resistance to motion

what are the 3 types of muscle contraction

1. concentric contraction

2. static contraction

3. eccentric contraction

what is concentric contraction

occurs as the length of muscle decreases

• flexing bicep

what is static contraction

occurs when muscle length remains constant

• bicep is flexed and held without any movement

what is eccentric contraction

occurs when length of muscle is increased

• bicep is extended

what is an agonist muscle and antagonist muscle

(provide an example)

agonist - the muscle that does concentric movement

antagonist - the muscle that does eccentric movement

example: bicep when flexed = agonist, tricep = antagonist

what is skeletal muscle attached to 

at least 2 bones via aponeuroses/tendons

what is a unique ability of muscle tissue

contraction

is it possible for muscle contraction to occur without muscle length changing

yes

• it occurs when a muscle attempts to move an immovable object

• the producing force equals the opposing force

what is the result of a muscle contraction

tension

a muscle can only exert a ___ but it can’t exert a ____.

pull, push

describe tendons

• attaches muscle to bone

• are tough pale colored

• is made of cords and formed from many parallel bundles of collagen fibers

• are flexible and they can bend around other tissues, changing position as they move

what is a tendon sheath

• a tubular double layered sac that’s lined with synovial membrane and contains synovial fluid

• only on some tendons

what is the function of tendon sheaths

• minimizes friction

• facilitates movement of the joint

what is epimysium

• a fibrous elastic tissue that surrounds a total group of muscle

what is perimysium

• a fibrous sheath that surrounds and protects bundles of muscle fibers

• it looks like thin pale grey lines in the cross-section of skeletal muscle

what is a fascicle

a bundle of muscle fibers or nerves

what is endomysium

connective tissue sheath that surrounds each individual muscle fiber

what are muscle fibers

• also known as muscle cells

• cells that are able to contract thus cause movement

draw a structure of skeletal muscle (page 7, slide 2)

draw a sarcomere (page 9, slide 1) ADD THE Z LINE

what do the thick filaments in a sarcomere produce

a dark A band

what do the thin filaments in a sarcomere produce

the light I band

what is the H zone

the portion of the A band where the thick and thin filaments don’t overlap

what portion is the sarcomere

the array of thick and thin filaments between the Z lines

what does shortening of sarcomeres in a myofibril produce

shortening of the myofibril

what happens in a sarcomere when a muscle contracts

• the z lines move closer together

• the width of the I bands decreases

• the width of the H zones decreases

what happens in a sarcomere when a muscle is stretched

• the width of the I bands and H zones increases

what is the striated appearance of the muscle fiber created by

a pattern of alternating dark A bands and light I bands

The A bands are bisected by the _____

H zone

the I bands are bisected by the ____

Z line

What is each myofibril made of

arrays of parallel filaments

what is the diameter of the thick filaments

15nm

what are the thick filaments composed of

protein myosin

what is the thin filament’s diameter

5nm

what are thin filaments composed of

the protein actin along with smaller amounts of the proteins troponin and tropomyosin

what does a motor unit do (draw it)

nerve impulses passing down a single motor neuron will trigger contraction in all the muscle fibers at which the branches of that neuron terminate

how many fibers does a single motor neuron trigger in the muscles controlling the eye movements

fewer than 10 fibers

How small are the motor units of the muscles controlling the larynx

2-3 fibers per motor neuron

True or False

The response of a motor units is all-or-none

true

the strength of the response of the entire muscle is determined by _______

the number of motor units activated

What is the state called where our skeletal muscles are in partial contraction, even at rest

tonus

what is Tonus maintained by

the activation of a few motor units at all times even in resting muscle

what is the immediate source of energy for muscle contraction

ATP

what are the three sources of high-energy phosphate to keep the ATP pool filled

1. Creatine phosphate

2. Glycogen

3. Cellular respiration In the mitochondria of the fibers

What kind of bond attaches the phosphate group in creatine phosphate

high energy

Creatine phosphate derives it’s high-energy phosphate phosphate from _____ and can donate it back to ____ to form _____

ATP, ADP, ATP

Creatine phosphate + ADP =

creatine + ATP

how many times larger is the pool of creatine phosphate in the fiber compared to ATP

10 times

Can creatine phosphate serve as a modest reservoir of ATP?

yes

how much glycogen do skeletal muscles contain?

1%

what degrades glycogen and through what process

muscle fiber, glycogenolysis

what does glycogenolysis produce

glucose-1-phosphate

Glucose-1-phosphate enters the _______ pathway to yield _______

glycolytic, two molecules of ATP for each pair of lactic acid molecules produced

Is glycogen a good source for ATP?

no, because it’s limited and eventually the muscle must depend on cellular respiration

What does cellular respiration do to breathing

make it deeper and more rapid

What is cellular respiration required for

• to meet the ATP needs of a muscle engaged in prolonged activity

• Enables the body to resynthesize glycogen from the lactic acid produced earlier

What is oxygen debt

when the demand for oxygen is greater than the supply

what happens during oxygen debt

• the body is working hard, and breathing in a lot of oxygen but the lung cannot absorb enough to cope with the level of activity

  • The body is mainly utilizing the anaerobic energy system and as a result, lactic acid builds up

What are 5 types of muscle fibers

1. Parallel or fusion

2. Convergent

3. Pennate

4. Circular

describe parallel or fusion muscle fibers

• run parallel to each other

• Contract over a great distance

• Have a good endurance

  • Are not strong

describe convergent muscle fibers

• coverage on the insertion to maximize the force of muscle contraction

Describe pennate muscle fibers

they are strong but tie quickly

what are the 3 types of ornate muscle fibers

1. Unipennate

2. Bipennate

3. Multipennate

Describe circular muscle fibers

the muscle fibers surrounded openings to act as a sphincter

What are the 2 types of muscle contractions

1. Isotonic

2. Isokinetic

What is an isotonic contraction

• the force remains constant

• Example: hold dumbbell and don’t move

What is an isokinetic contraction

• muscle contracts at a constant speed regardless of the resistance force

What remains constant during an isokinetic contraction

the angular velocity

Isotonic vs isometric contraction

(draw chart on pg 17, slide 2)

What is cardiac muscle

an involuntary, striated muscle that’s found in the walls of the heart

What is myocardial infarction (MI) or acute myocardial infarction (AMI)

A hear attack

When do heart attacks occur

when a branch of blood vessel stops supplying blood to a part of the heart causing damage to the heart muscle

symptoms of heart attacks

chest pain, discomfort traveling into the shoulder, arm, back, neck, or jaw