Chapter 4: Calcium & Power Stroke

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How many sarcomeres are in a muscle?

zillions of sarcomere

There are 2 kinds of myosin cross bridges, what are they?

1) Cocked 2) Uncocked

In a sarcomere there are two myofilaments(proteins), what are they?

1) Myosin 2)Actin

When a sarcomere is contracted, how long it is?

2 mircometer

How long is a sarcomere when its relaxed?

2.5 mircometers

What is the purpose of a calcium pump?

The purpose is to take Calcium back up

If cocked myosin crossbridge interacts with actin , and what occurs?

A power stroke occurs

(ATP/ADP) is required to cock the myosin cross bridge.

ATP

What is always present in a muscle?

ATP is always present in a muscle

How is energy produced?

ATP-ADP +P=energy

Why are the cocked myosin crossbridges not allowed to interact with Myosin?

Because of Troponin

What is the function of the T- Tubule?

Brings action potential down to SR

What does calcium interacts with for muscle contraction?

Calcium interacts with Actin & Myosin Filaments

Describe the action of calcium in muscle contraction.

Calcium levels go up in a cell; increase of intracellular calcium causes muscle contraction

What stops tropomyosin and how does it stop?

Calcium stops tropomyosin and it moves it out of the way

What happens if you bring action potential down to the sarcoplasmic reticulum?

Calcium will release

Myosin crossbridges are (cocked/uncocked) in an uncontracting muscle

Cocked

T or F: Both the myofilaments, Actin and myosin shorten when contracted.

False

What does the uncocked myosin crossbridge do?

It binds and splits ATP and then becomes cocked

Describe the myofilament; Myosin

Large Filament

Who has T- Tubules?

Only skeletal muscles

Describe a cocked myosin crossbridge

Responsible for the sliding of filaments Connects to Actin and pushes it along

Where is calcium stored?

Sarcoplasmic Reticulum

Describe the myofilament; Actin

Smaller Filament

What is the boundary of every sarcomere called?

The boundary of every sarcomere is called z- lines

What happens when the muscle contracts?

The myofilaments do not contract but they slide "sliding filament mechanism, causing a degree of overlap increases

What is the functional unit of the muscle and what does it have the ability to do?

The sarcomere is the functional unit of the muscle and it has the ability to contract

If the Myofilaments in a sarcomere don't shorten when contracted, then what does?

The sarcomere itself.

What is the chemical inhibitor that stop contraction?

Tropomyosin

Describe the H-Zone in a sarcomere

no overlap (relax) overlaps (contracted)

Define Sarcomere

part of muscle that is responsible for muscle contraction; distance in a muscle between two z-lines.

What is Rigor Mortis?

state of stiffness; stops making ATP. YOU DEAD!

What is a power stroke?

when actin moves a little and then sliding of filaments (uncocks)


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