6000 Exam 1 - Anat/Physio

What is the primary function of the heart?

It is the primary pump that circulates blood through the entire vascular system

What forms the base of the heart?

The superior portion of the heart formed primarily by the two atria

What is the apex of the heart?

The tip of the left ventricle; it is also called the point of maximum impulse (PMI)

What are the three tissue layers associated with the heart?

• Pericardium

• Myocardium

• Endocardium

What are the two layers of the pericardium?

• Parietal

• Visceral (epicardium)

What is the myocardium?

The muscular layer of the heart responsible for cardiac contraction

What is the endocardium?

The inner lining of the heart

What are the four chambers of the heart?

• Right atrium

• Right ventricle

• Left atrium

• Left ventricle

Which chamber receives systemic venous blood?

Right atrium

Which chamber pumps blood toward the lungs?

Right ventricle

Which chamber receives oxygenated blood from the lungs?

Left atrium

Which chamber pumps oxygenated blood into systemic circulation?

Left ventricle

What is the "atrial kick"?

The simultaneous contraction of both atrium to assist with ventricular filling

Why is blood flow through the heart dependent on chamber pressures?

Blood flows down a pressure gradient—from areas of higher pressure to areas of lower pressure

What are the four heart valves?

• Tricuspid

• Mitral/bicuspid

• Pulmonic

• Aortic

Which valve is between the right atrium and right ventricle?

Tricuspid valve

Which valve is between the left atrium and left ventricle?

Mitral/bicuspid valve

Which valves are the semilunar valves?

Pulmonic and aortic valves

What is the primary function of the heart valves?

To ensure one-way blood flow through the heart

What causes a heart valve to open?

A pressure gradient across the valve that favors forward blood flow

What causes a heart valve to close?

A reversal of the pressure gradient, which prevents backward blood flow

What are the major great vessels associated with the heart?

• Aorta

• Pulmonary artery

• Pulmonary veins

• Superior vena cava

• Inferior vena cava

What vessel carries blood from the left ventricle into systemic circulation?

Aorta

What vessel carries blood from the right ventricle toward the lungs?

Pulmonary artery

What vessels return blood from the lungs to the left atrium?

Pulmonary veins

What vessels return systemic venous blood to the right atrium?

Superior and inferior vena cava

What is the purpose of the coronary arteries?

To provide blood supply to the heart muscle/myocardium

What are the two major coronary arteries?

• Right coronary artery (RCA)

• Left coronary artery (LCA/left main)

What are the major branches of the right coronary artery?

• Right acute marginal artery

• Posterior descending artery

What are the major branches of the left coronary artery?

• Left anterior descending (LAD)

• Diagonals

• Circumflex

• Left acute marginal artery

What happens to coronary blood flow during exercise?

Increases because sympathetic activation produces coronary vasodilation, while HR and contractility also increase

What is the SA node?

The primary pacemaker of the heart

What are the three internodal tracts?

• Bachman (anterior)

• Wenckebach (middle)

• Thorel (posterior)

What is the primary function of the AV node?

To slow conduction, allowing time for the atria to contribute to ventricular filling

What structure follows the AV node?

Bundle of His

What structures does the Bundle of His divide into?

Right and left bundle branches

What structures distribute the electrical impulse throughout the ventricles?

Purkinje fibers

What is the sequence of electrical conduction through the heart?

SA node → internodal tracts → AV node → Bundle of His → right/left bundle branches → Purkinje fibers

Why can an alteration in the conduction pathway reduce cardiac output?

Because altered electrical conduction can disrupt the mechanical activity and coordinated contraction of the heart

What nervous system controls the heart's autonomic innervation?

Autonomic nervous system (ANS) through the cardiac plexus

Where is the cardiac plexus located?

Anterior to the tracheal bifurcation

What is the effect of sympathetic stimulation on the heart?

It is excitatory, increasing cardiac activity

What neurotransmitters/hormones are associated with sympathetic cardiac stimulation?

Catecholamines, including epinephrine and norepinephrine

What is the effect of parasympathetic stimulation on the heart?

It is inhibitory, decreasing cardiac activity

What neurotransmitter is associated with parasympathetic stimulation?

Acetylcholine

Are both cardiac and skeletal muscle striated?

Yes

Is cardiac muscle voluntary or involuntary?

Involuntary

Is skeletal muscle voluntary or involuntary?

Voluntary

What controls cardiac muscle?

Primarily the autonomic nervous system

What controls skeletal muscle?

Central nervous system

Which muscle type is more fatigue resistant?

Cardiac muscle

How does capillary density differ between cardiac and skeletal muscle?

• Cardiac muscle has approximately 2,500–4,000 capillaries/cm³, compared with approximately 300–400 capillaries/cm³ in skeletal muscle

• Makes cardiac muscle less prone to fatigue

What oxygen-binding protein is identified in both muscle types?

Myoglobin

Can both cardiac and skeletal muscle hypertrophy and atrophy?

Yes

What are the two major types of cells in the myocardium?

Myocytes and conductive cells

What structures connect cardiac muscle cells?

Intercalated discs

What three characteristics of cardiac muscle are emphasized?

Automaticity, rhythmicity, and conductivity

What is the cardiac cycle?

The sequence of events occurring from the beginning of one heartbeat to the beginning of the next

What are the two major periods of the cardiac cycle?

Diastole and systole

What occurs to the heart during systole?

It contracts

What occurs to the heart during systole?

It relaxes and fills

What does the P wave represent?

Atrial depolarization

What is the PR interval?

The interval associated with conduction from the atria toward the ventricles

What does the QRS complex represent?

Ventricular depolarization

What is the ST interval associated with?

The period following ventricular depolarization before ventricular repolarization

Why do valves open and close during the cardiac cycle?

Changes in chamber pressures create pressure gradients that determine whether valves open or close

How does the ANS affect heart rate?

It alters the heart's intrinsic pacing rate through the net effect of sympathetic and parasympathetic influences

What is a chronotropic effect?

An effect on heart rate

What is an inotropic effect?

An effect on contractility

What type of receptors are important in regulating HR?

β-adrenergic receptors

What hormones can influence HR?

Catecholamines, thyroid hormones, steroids, natriuretic peptides, angiotensin, and neurokinin.

What do baroreceptors detect?

Stretch associated with blood pressure

Where are the major baroreceptors located?

The aortic arch and left/right internal carotid arteries

What is the primary purpose of baroreceptors?

To help maintain mean arterial blood pressure and end-organ perfusion

What do chemoreceptors detect?

Changes in the chemical composition of blood.

What variables do chemoreceptors monitor?

pH, PO₂, and PCO₂

What happens to baroreceptor stretch when blood pressure decreases?

Blood pressure decreases → less blood/stretch → decreased baroreceptor stimulation

What happens to the SNS and PNS activity when blood pressure falls?

• PNS activity decrease

• SNS activity increase

What happens to HR when blood pressure falls?

Increases

What happens to BP when the baroreceptor reflex responds to a decrease in BP?

BP increases toward normal.

What happens when someone suddenly stands up?

Blood pressure initially decreases due to redistribution of blood, decreasing baroreceptor stretch. The brain responds by decreasing PNS activity and increasing SNS activity, increasing HR and BP

What system provides long-term hormonal control of BP?

The Renin-Angiotensin-Aldosterone System (RAAS)

What is venous return?

The return of blood through the veins toward the heart

What is the overall purpose of RAAS?

Long-term regulation/homeostasis of blood pressure through hormonal mechanisms

What is normal venous pressure according to the lecture?

Approximately 0–10 mmHg

What factors influence venous return?

Venous pressure, the muscular pump, sympathetic nervous system activity, thoracic pressure, and positioning

How can positioning influence venous return?

Positioning such as Trendelenburg or lower-extremity elevation can influence venous return

When does coronary blood flow primarily occur?

Diastole

What happens to coronary blood flow with sympathetic activation?

Coronary vasodilation → increased coronary blood flow, along with increased HR and contractility.

What happens to coronary blood flow with parasympathetic activation?

Coronary vasoconstriction → decreased coronary blood flow, along with decreased HR

How does blood flow to skeletal muscle change between rest and exercise?

Blood flow changes substantially with activity and is regulated partly through shunting

What happens to peripheral blood vessels during sympathetic activation?

They undergo vasoconstriction, helping redirect blood toward working tissues

What neurotransmitter stimulates α-receptors in blood vessels of organs?

Norepinephrine

What is the effect of norepinephrine on these vessels?

Vasoconstriction, which helps shunt blood toward working muscles.

What hormone stimulates β-receptors in skeletal muscle blood vessels?

Epinephrine

What is the effect of epinephrine on skeletal muscle blood vessels?

Vasodilation, increasing blood flow to skeletal muscle.

A patient takes a β-blocker. Why might their HR response to exercise be blunted?

β-blockers interfere with β-adrenergic effects, limiting the increase in HR and contractility that normally occurs with sympathetic stimulation

During exercise, why does blood flow to skeletal muscle increase?

Sympathetic activity causes peripheral vasoconstriction in some vascular beds while epinephrine stimulates β-receptors in skeletal muscle vessels, producing vasodilation and increased muscle blood flow

Why does coronary blood flow increase during exercise despite sympathetic activation?

Sympathetic activation produces coronary vasodilation, increasing coronary blood flow to meet the increased metabolic demands of the heart

A patient has an abnormal cardiac conduction pathway. Why could cardiac output decrease?

Altered conduction can disrupt coordinated mechanical activity of the heart, reducing effective cardiac contraction and therefore cardiac output.