Anatomy Exam 3

Isometric contraction (Static) (Eg. Plank)

Muscle tension without any joint movement or change in muscle length

Isotonic contraction (Dynamic) (Squat, Bicep curls)

Muscle tension changes length against a constant load, shortnening phase

Ecccentric Contraction (lengthening) (lowering phase of bicep curl)

Muscle elongates while under tension. Acts as a “brake”

Which type of muscle contraction produces most force?

Eccentric

Joints can also be known as?

Levers

Bone is the

Lever

Joint is the

fulcrum

Muscle is the

effort

In which lever class system is the fulcrum placed directly between the effort and load arm?

First Class

In which lever class system is the effort arm longer than the load arm (fulcrum closee to load arm)?

Second class

In which lever system is the load arm longer than effort arm?

Third Class

Which class system provides greatest mechanical advantage (effort arm exceeds load arm)?

2nd class

Why does a longer effort arm result in greater mechanical advantage?

Less effort/force is needed to move greater loads

If your effort arm is 8, and your load arm is 2, what is your MA?

4

What class lever is most common in body?

3rd class (longer load arm, shorter effort)

A longer load arm than effort arm would mean?

Decreases MA (less than 1)

Most levers in body have a MA of?

<1

What is the primary heat source in the body?

Muscles through thermogenesis (shivering)

Muscles are both excitable and?

Conductive

Excitability means it can respond to?

membrane potential change

Conductivity means?

Signal can be propagated

Muscles must have three abilities of movement.

Contractility, flexibility, extensibility

Contractility means the muscle..

Can shorten and generate force (sliding filament theory)

Contractility is an “blank” process?

Active

Extensibility means…

permitting muscle stretch beyond resting length without a tear

Elasticity means….

Fiber returning to resting length after deformation (Titin)

What would be an example of loss of excitability?

K+ contionously depolarizes sarcolemma, Na+ channels inactive (Hyperklemia)

What would be an example of loss of contractibility?

Loss of ATP, myosin (thick) cannot unbind to actin (thin), RIGOR MORTIS

Muscle is an

Organ

Muscle is composed of

Four Tissue types (muscle, CT, blood vessels, nerves)

Muscle descends from an Organ to a?

Molecule

Muscle descending from?

Whole muscle, fascicle, muscle fiber, myofibril, myofilament

Muscle itself is composed of how many layers?

3

Outermost layer, surrounded by dense irregular CT (protects muscle from force and friction)

Epimysium

Middle muscle layer, Surrounds each fascicle (bundle of muscle), and carries blood vessels, still dense CT

Perimysium

Innermost muscle layer, One muscle fiber Surrounded by areolar CT, contains capillaries, ensuring oxygen delivery, also contains satellite cells.

Endomysium

Epi and Perimysium are surrounded by dense irregular CT because they?

Protect against friction, protect muscle

Cord-like elastic, built for pure force transmission.

Tendons

Flat sheets where muscles attach. Distribute force over a large area, prevents stress concentration.

Aponeureses

Why do tendons heal very slowly?

Poor vascularity

Blood supply and Motor innervation scale with

Muscle demand

How many capillaries are there per muscle fiber?

One

Motor neurons from the CNS control every?

Voluntary contraction

Cardiac and smooth muscle require what systems input?

SNS (somatic)

Muscle fibers are?

Largest cells in body by length (30cm long)

Skeletal Muscle cells are “blank”, meaning they have hundreds of nuclei per fiber

Multinucleate

Myofibers are made up of hundreds to thousands of these, taking up 80% of it.

Myofilaments (contractile proteins)

How are muscle fibers formed?

Myoblast fusion (embryonic precursor spells), each nucleus retains its own DNA

Where is the signal entry point for every contraction in a muscle fiber?

Sarcolemma

What can the sarcolemma be equated to for muscle cell?

Plasma membrane

Sarcolemma is specialized for?

Electrical signaling

Every myofibrils sarcolemma contains “blank”, invaginations carrying an action potential.

T-Tubules

How many t tubules are there per sarcomere?

2

What is the triad?

One T tubule, flanked by two terminal cisternae

What is terminal cisternae

Front of sarcoplasmic reticulum

What is the sarcoplasmic reticulum?

Structure containing calcium deposits that is connected to DHP-RyR1 complex

Is DHP-RyR1 action a mechanical or chemical link?

Mechanical

What happens when the DHP senses a voltage?

DHP tugs on RyR1, causing RyR1 to cringe inward and open the SR gate, releasing calcium

What structure is the reservoir of Ca2+

Sarcoplasmic Reticulum

Where does the calcium flood into after being released?

Sarcoplasm

Are calcium reuptake and release active or passive?

Active

Why is calcium reuptake a active process?

Relies of SERCA pump, pumps calcium against its gradient back into SR, uses ATP

What is different with the DHPR complex with cardiac muscle?

Not mechanical, requires Ca2+ channels

Would a calcium channel blocker effect skeletal or cardiac muscle?

Cardiac

Sarcomere is the region between?

Two Z discs

What is the sliding filament theory?

Filaments slide but do NOT SHORTEN

What is the mechanism in simple terms of sliding filament theory?

Myosin head pulls actin towards M line, sarcomeres shorten

What is the optimal sarcomere length?

2.2 Micrometers

What happens if a sarcomere is too short?

Has no where to go, myosin cannot pull actin anywhere, cannot shorten anymore

What happens if sarcomere is too long?

Actin is too far away, myosin can barely pull onto any, muscle cannot fully contract

Z discs anchor for what filament, and are the primary boundary of every sarcomere?

Actin

Contains only thin filaments, and narrows during a contraction.

I band

Contains thick filaments and overlapping thin filaments, stays constant during contraction.

A band

A band is proof of what?

Filaments slide and do not shorten

Center of A band, only thick filament, no thin overlap. Disappears as sarcomere shortens.

H Zone

Anchor of thick filament, center of each sarcomere.

M Line

What is the largest protein in body?

Titin

Titin is the “blank”, from Z disc to M line

Molecular spring,

Titin is a “blank” structure

Passive

Neublin, Dystrophin, etc. Are all what structures

Non passive.

Synapse between motor axon terminal and muscle fiber

Neuromuscular Junction

What is the motor unit?

One motor neuron and all the muslce fibers it innervates

The motor neuron/unit operates on an all or nothing principle, what does this mean?

Once it reaches threshold and the signal is sent, all muscle fibers contract maximally from the signal from the motor unit

Motor unit size varies with “blank” vs “blank” requirements

Precision vs Power

Small motor units required for?

intrinisc hand muscles, fine motor control

Large motor units are used for?

Power production, less precision

Action potentials are driven by what movement?

Na+/K+

At rest, Pumps 3 “blank” out, 2 “blank” in

Sodium, Potassium

What is the resting membrane charge?

-70mv

Explain depolarization

Voltage gated Na+ cells open, Na+ rushes in, drivers it towards a positive charge

What is the Gate threshold for an action potential, meaning once it reaches this charge, it cannot go back?

-55

What happens at +30mv?

Sodium Channels close, Potassium begins getting kicked out, cell membrane is repolarizing

ECC links the AP to

Cross Bridge Cycling

Step 1 of ECC

AP propogates to synaptic knob

Step 2 of ECC

Depolarization opens Ca2+ channels at knobs, releasing Ca2+ into knob

Why does the signal sent through knob release Ca2+ channels?

The calcium channels are voltage gated.

Essential trigger for release of Ach

Calcium entry

Step 3 of ECC

Calcium triggers synaptic Ach vescicle fusion with membrane, Ach released into synaptic cleft

What on the vesicles makes it so the fusion starts occuring?

Synaptotagmin which has a high afffinity to calcium, senses it, and begins the formation with the membrane