Chapter 11

Does tetanus This happen in the heart?

No, it does not.

Which organ(s) is cardiac muscle found?

Only in the heart

What is Duchenne muscular dystrophy?

Duchenne muscular dystrophy is a disorder in which little or no dystrophin is present in muscle fibers. Without the reinforcing effect of dystrophin, the sarcolemma tears easily during contraction, causing the muscle fibers to rupture and die. This disorder is sex-linked, affecting boys almost exclusively. Most boys with DMD have difficulty running, jumping, and hopping, and eventually are unable to walk.

Describe the consequences of tetanus in the heart?

During tetanus, the heart would not have a refractory period meaning that he heart would not have a change to fill back up before contraction. This would lead to death.

What is happening in the heart during the refractory period?

During the refractory period the heat is filling up with blood

What is dystrophin?

Dystrophin is a cytoskeletal protein that links thin filaments of the sarcomere to integral membrane proteins of the sarcolemma, which are attached in turn to proteins in the connective tissue extracellular matrix that surrounds muscle fibers. Dystrophin and associated proteins are thought to reinforce the sarcolemma and help transmit the tension generated by the sarcomeres to the tendons.

Define the two types of muscle contractions. Give an example.

Isotonic : Movement is created, muscle changes length Isometric: No movement is created, muscle length does not change

Explain what a functional syncytium is, its function, how many there are in the heart.

It is a coordinated unit of interconnected muscle fibers. It allows the heart to contract as a single unit. There are two: One in the Atria and one in the Ventricles

How are muscle cardiac fibers connected? What function does this connection serve?

They are connected via intercalated disks (which contain desmosomes and gap junctions). They allow action potentials to travel from one cardiac muscle fiber to another.

What is the stress-relaxation response? What type of muscle does this?

This is the capacity for smooth muscle to be able to be stretched and still retain its ability to contract in the future. When smooth muscle fibers are stretched, they contract initially, developing increased tension, and then relax after about a minute. This allows muscles to contract indefinitely.

Define Autorhythmicity

This is the capacity of the heart to generate spontaneous action potentials

Define and differentiate the two major types of smooth muscle? Which is more common?

Two Types: Single unit and Multi-unit Single Unit: These are the most common. They are autorhythmic like cardiac muscle and they behave like functional syncytium. They can also be called visceral smooth muscle because these are found in the walls of the visceral organs such as the stomach, intestines, uterus, urinary bladder, and blood vessels. Multi-Unit: These consist of fibers that act independently of each other. Gap junctions are not so common here. Here, stimulation of a fiber only contracts that one fiber, and not those around it.

What is utrophin?

Utrophin is a protein that is functionally similar to dystrophin.

Describe the role of ATP in muscle

When ATP binds, muscle relaxed; When ADP binds, muscle relaxed

Contractility

Ability of muscle to contract forcefully when adequately stimulated

Extensibility

Ability of muscle to stretch without being damaged

Electrical Excitability

Ability to respond to certain stimuli by producing action potentials

Define agonist and antagonist. Give an example.

Agonist : causes the action Antagonist: opposite action at the same joint Bicep agonist, tricep antagonist

Give an example of the Stress-Relaxation Response

An example of this would be how your urinary bladder contracts after being stretched and is still able to be firm and not distorted.