Physio: Ch 12 Muscle

name the 3 types of msucles

-cardiac
-smooth
-skeletal

Describe the characteristics of skeletal muscle

- Attached to the bone by tendons
-striated
-voluntary (somatic)
-multi-nucleated

What causes the straitation on skeletal muscle?

it is based on the arrangement of filaments in the muscle cell cytoplasm (sarcoplasm)

Name some characteristics of smooth muscle

-not striated
-involuntary (autonomic: blood vessels, organs)

Name some characteristics of cardiac muscles

-only found in heart
-striated
-involuntary
-mono nucleated

What is a skeletal muscle cell called?

a muscle fiber

[bc they are long and thin]

Name some muscle fiber characteristics

- usually short but can be as long as the entire muscle
-multi-nucleated (due to fused muscle cells)

what is a muscle?

multiple skeletal muscle fibers bound together with connective tissue

Bundles of connective tissues are called....

tendons

how is muscle attached to bones?

through tendons

what does a muscle contraction result in?

increased muscle *tension*

Name the components of muscles from smallest largest

Myofilament --> myofibrils --> muscle fibers --> muscle fasicles --> skeletal muscle

[ --> = make up ]

a group of muscle fibers is called what?

muscle *fascicle*

a group of myofibrils is called what?

a muscle fiber (aka muscle cell)

what do myofibrils contain?

myofilaments

[think.. myoFILs up]

what are the dark lines called in skeletal muscle?

A bands = dark lines

what are the light bands in skeletal muscle called?

I bands

What is a neuromuscular junction?

The junction where muscle fibers and motor neurons meet

what type of neurons innervate skeletal muscle fibers?

motor neurons

If a motor neuron is stimulated, what happens?

the motor neurons causes action potential (AP) in muscle fibers

What happens when motor neurons release AP?

Acetylcholine releases into the neuromuscular junction

What happens when ACh is released in the neuromuscular junction?

Acetylcholine binds to nicotinic ACh receptors in the muscle fibers causing more action potential which then causes a contraction

describe 'motor unit'

when *one* motor neuron innervates *many* muscle fibers

what is special about smaller motor units?

they allow a finer muscle control

[fewer fibers per neuron]

Describe recruitment

bringing muscle fibers into a response, causing more motor units to activate, thus creating more tension

activation of more motor neurons/motor units lead to what?

increase in muscle tension

Describe summation

stimulation of more and more motor units at different times, causing stronger tension

[ex. holding up one book then slowly adding more]

[think.. summ = adding]

what is a bundle of myofilaments called?

myofibrils

what are sections of myofibrils called?

a sarcomere

a collection thick and thin myofilaments cause what?

striations on myofibrils

Name characteristics of THICK filaments

- is also known as myosin
-has two globular heads that form cross bridges with actin during muscle contraction
-is the dark lines in striations

Name characteristics of THIN filaments

-is also known as actin
-has regulatory proteins (troponin and tropomyosin)
-are the light lines

Describe is troponin

a regulatory protein in actin that binds different chemicals based on the name

[ex. Troponin C binds calcium, Troponin T binds tropomyosin, I binds actin]

Describe Tropomyosin

a regulatory protein that blocks myosin from binding with actin (inhibits a contraction)

what divides myofibrils into sarcomeres?

Z lines are attached to each end dividing the myofibrils

how is thick mysoin anchored in place?

it anchored by titin.

why is the I band appear lighter?

I bands are thin filaments, because they are thinner, they are less compacted and lighter in color

Where are the thin filaments anchored to?

z lines

connection between myosin and actin during muscle contraction is called...

a cross bridge

describe contraction

an activation of the force-generating sites in muscle fibers
(ex. cross bridges in myosin)

what is a sliding filament mechanism?

the overlapping of thick and thin filaments, in a sarcomere, move past each other to contract muscle fiber

How does the sliding filament mechanism start?

myosin MUST binds to actin for it to slides it, pulling the two Z lines closer together

when actin is blocked by tropomyosin, the muscle is in a ____ state.

relaxed

what holds tropomyosin in a blocking position?

troponin

After muscle fibers depolarizes, what happens?

Action potentials (AP) travels down the transverse tubules in the fiber and releases Ca2+

Where is Ca2+ stored?

in the sarcoplasmic reticulum

What happens when tropomyosin is moved out of it's blocking position?

Myosin can bind to actin, which causes a contraction

after the cross bridge forms, Pi is released to cause what?

a power stroke to move the actin filament

Where is Ca2+ released?

[hint: where is it stored?]

into the sarcoplasm

(like cytoplasm but for muscle cells)

What is a latent period?

a period between action potential (AP) and contraction

tbh idk just study this

...

what state is tropomyosin at during *relaxation?*

tropomyosin is in it's blocking state

what happens after contraction?

the muscle cell membrane repolarizes abd calcium moves back into the sarcoplasmic reticulum

define tension

force exerted on an object by contracting muscle

[opposite of load]

define load

force exerted on muscle by an object

[opposite of tension]

define twitch

a *single* contraction of a muscle fiber to a SINGLE action potential

define recruitment

basically, for more tension (strength), more motor units are activated

describe tetanus/tetany

sustained maximal contraction due to repetitive stimulation

[gripping on to something for a longtime and trying to maintain the same % of strength]

[think.. TeT = tt= same/constant ]

describe unfused/incomplete tetanus:

Partial dissipation of tension between stimuli

described fused/complete tetanus:

no time for latency period between rapid occurring stimuli

what is isotonic contraction

a contraction where tension remains the same but the muscle length changes (ex. bicep curls, bicep will change length)


[think... nic - changes (like ur lungs)]

what is isometric contraction

a contraction with the same tension, but the muscle doesn't change length.

[ex. planking]

Short sarcomeres produce ____ tension because they ____ room to slide

little // lack

optimal-length sarcomeres make ___ tension because they __

maximum // overlap

long sarcomeres make ___ tension because they __

little // do not overlap

t/f tension gets greater the closer it gets to resting percentage

False

Characteristics of slow twitches (Type I)

- slow to reach maximum tension
-small diameter
-smlow to fatigue
-respond well to repetitive stimulation without becoming fatigues

Characteristics of fast twitches (Type II)

- reaches maximum tension quickly
-large diameter
-fatigues quickly

Characteristics of Type IIX twitches (fastest)

-used for quick burst of strong activation

(think of sprints)

Type IIA (intermediate) twitches

respond quickly to repetitive stimulation within intermediate time to fatigue

(think long distance walking)

Type I fibers are also called..

slow twitch fibers

Type II fibers are also called...

slow twitch

Type IIX are known as...

the fastest fibers

Type IIA fibers are known as...

intermediate fibers

describe muscle fatiuge

decease muscle tension over time due to repeated stimulation

what ___
and ___ depolarizes cardiac muscle contraction

Na+ and Ca2+

increase of calcium in cardiac muscle causes the sarcoplasmic recticulm to ____ release of calcium

Increase!

[this is a positive feedback]

how is smooth muscle arranged?

in layers!

where can we find smooth muscle?

in hollow organs that change in volume

[bladder, lungs, blood vessels etc]

what controls cross bridge activity in smooth muscle?

calcium

what controls cross bridge activity in cardiac muscle?

calcium

____ binds to troponin C

calcium

when troponin C binds with calcium, this causes what to react?

Troponin T

what does troponin T do?

Helps move tropomyosin out of blocking position