smooth and cardiac muscle

How are smooth and skeletal muscle similar?

-Both function using actin filaments that slide past stationary myosin filaments.

-Both powered by Ca++

Both use ATP as energy for cross bridging

What are the main differences between smooth and skeletal muscle?

-Different structure and organization. 

-Different methods of excitation

-Contraction Reponses different

Where is smooth muscle found?

-The walls of hollow organs.

What is the shape of smooth muscle and how many nuclei do they have?

Spindle shaped. One

What is the size of a smooth muscle cell compared to a skeletal muscle cell?

Spindle shaped and small. Does not run the length of the muscle.

How are smooth muscle cells arranged?

In sheets

What is the contraction of smooth muscle cells like?

Slow and sustained.

Smooth muscle cells are more permeable to Ca++, which causes?

Spontaneous depolarization

Calcium for smooth muscle is stored in?

Smooth endoplasmic reticulum

What are the three filaments found in smooth muscle?

Thick, thin, and intermediate.

What three structure are missing in smooth muscle?

Z-lines, t-tubules, and sarcomeres.

Describe the SR in smooth muscle?

Underdeveloped

What are the 6 steps of contraction in smooth muscle?

-Caldesmon covers actin binding sites

-Ca++ binds to Calmodulin and activates in.

-Calmodulin activates myosin kinase

-Myosin kinase splits ATP and phosphorylates myosin

-Myosin forms cross bridges

-Ca++ removal leads to relaxation

What are the two types of smooth muscle?

Single unit and multi-unit.

Single unit smooth muscle is found in?

Visceral (involuntary) muscle.

Single unit smooth muscle contracts how?

As a unit

Single unit smooth muscle is electronically coupled and has?

Pacemakers

Single unit smooth muscle is arranged how?

In sheets

Multi-unit smooth muscle is found in?

Large tubes such as arteries.

Multi-unit smooth muscle has what kind of fibers?

Independent 

Multi-unit smooth muscle has what kind of contractions?

Graded contractions

How does smooth muscle respond to stretch?

Stretch activates single units

what is the length tension relationship of smooth muscle?

Smooth muscle can generate force over a much broader length.

What makes smooth muscle fatigue resistant?

Slower cross bridge cycles and minimal ATP use.

what is hyperplasia in smooth muscle?

An increase in the number of muscle cells

What are the layers of the heart?

-Epicardium (outermost)

-Myocardium

-Endocardium (Innermost)

What is the arrangement of cardiac muscle like?

Spiral

What is the flow of blood in the heart?

RA>Tricuspid valve>RV>Pulmonary valve>Pulmonary artery>lungs>Pulmonary vein>LA>Mitral (Bicuspid) valve>LV>Aortic valve>Aorta tissue>Venae cavae>RA

How many Chambers does the human heart have?

4

What are the valves of the human heart?

Tricuspid, pulmonary, bicuspid (mitral), aortic

What are the major arteries of the heart?

Pulmonary, aorta, and coronary.

What are the major veins of the heart?

Vena cava and pulmonary

Is cardiac muscle striated or smooth? 

Striated

How does cardiac muscle differ from skeletal muscle?

-Loosely innervated

-One nucleus

-Intercalated disks (Gap junctions and desmosomes for electrical connection and support)

-Pacemaker

-All or nothing action potential

-Refractory period

What is a neurogenic pacemaker and what type of circulatory system uses it?

Rhythmic beat originates from CNS. Cardiac ganglion with unstable resting potential. Found in open circulatory systems.

What is the myogenic pacemaker and what type of circulatory system is it found in?

Rhythmic beat originates from heart cells. Myocytes with unstable resting potential. Found in closed circulatory systems.

What is the pacemaker of the heart?

The sinoatrial node. 

What is the size of the SA?

2-8mm

Where is the SA found?

Where the superior vena cava meets the right atrium

What are the ectopic foci?

Regions of the heart other than the SA that are capable of initiating beats.

What is the sequence of electrical activity in the heart?

-SA

-Atrioventricular node

-Atrioventricular bundle

-Bundle branches

-Purkinjie fibers

What causes the P wave?

Atrial depolarization

What causes the QRS wave?

Ventricular depolarization

What causes the T wave?

Ventricular repolarization

Why is atrial repolarization not visible on ECG?

It’s hidden by the QRS wave

What happens in phase 1 on an ECG?

P wave. Ventricular filling and atrial contraction. AV valves are open and aortic and pulmonary valves are closed.

What happens in phase 2a on an ECG?

QRS wave. Isometric contraction phase. AV valves are closed and aortic and pulmonary valves are open.

What happens in phase 2b on an ECG?

Post QRS wave to T wave. Ventricular ejection phase. AV valves are closed and aortic and pulmonary valves are open.

What happens in phase 3 on an ECG?

Directly post T wave. Isovolumetric relaxation. AV valves are closed and aortic and pulmonary valves are open.

What controls the SA node?

-Sympathetic nervous system increases heartrate

-Parasympathetic nervous system decreases heart rate

What is cardiac output?

CO=Heart rate X Stroke volume

What is stroke volume?

End diastolic volume-end systolic volume

How is heart mass related to body mass?

They rise proportionally on a log-log scale

Fish heart body mass %?

0.2%

Mammal heart body mass %?

0.6%

Bird heart body mass %?

0.8%

With exercise metabolism may increase by?

15X

With exercise cardiac output may increase by?

5X

With exercise stroke volume may increase by?

2X

With exercise heart rate may increase by?

3X

With exercise O2 consumption may increase by?

3X

What are the intrinsic factors that regulate cardiac output?

Its contractile properties

What are the extrinsic factors that regulate cardiac output?

Nervous system and hormonal signals

What is the Frank Starling law of the heart?

An increase in the amount of blood in the ventricles before contraction leads to increased contraction force and higher stroke volume.

What is an inotropic effect?

The ability of a substance to increase the contractile force of the heart.