psl 250 exam 5- heart, cardiac output

what is the pericardium?

the pericardium is a double-walled sac enclosing the heart and the roots of the great vessels.

what are the layers of the pericardium?

fibrous and serous

what is the fibrous pericardium?

outer layer- tough, dense connective tissue that anchors the heart to the diaphragm and sternum and prevents overfilling

what is the serous pericardium?

inner layer- thin, double-layered membrane

what are the layers of the serous pericardium?

parietal and visceral

what is the parietal layer of the serous pericardium?

superficial- lines the inner surface of the fibrous pericardium.

what is the visceral layer of the pericardium?

deep- adheres directly to the heart surface

what lies between the parietal and visceral layers of the serous pericardium?

pericardial cavity- contains serous fluid 

what is the function of the pericardium?

• Protects the heart from trauma, infection, and overexpansion.

• Anchors the heart in the mediastinum.

• Provides a frictionless environment through pericardial fluid.

• Maintains the heart’s position and prevents displacement during body movement.

what are the heart wall?

epicardium, myocardium, endocardium

(superficial to deep)

what is the function of the epicardium?

outer layer

• Visceral layer of serous pericardium.

• Contains blood vessels, nerves, and fat.

• Provides lubrication and protection.

what is the function of myocardium layer?

middle layer

• Composed of cardiac muscle tissue.

• Responsible for contraction and generation of pumping force.

what is function of the endocardium?

inner layer

• Smooth endothelial lining inside chambers and valves.

• Reduces friction and prevents blood clot formation.

what are the major cell types of the heart?

contractile cardiac myocytes

autorhythmic (pacemaker) cells 

endothelia and connective tissue cells 

what are contractile cardiac myocytes?

99% of heart muscle; generate mechanical force.

what are autorhythmic (pacemaker) cells?

1%; initiate and conduct electrical impulses (e.g., SA and AV nodal cells)

what are endothelial and connective tissue cells?

provide structural and metabolic support.

what is the general structure of cardiac myocytes?

Short, branched, striated cells with a single central nucleus.

how are cardiac myocytes connected to eachother?

intercalated discs containing desmosomes and gap junctions

what do desmosomes do?

mechanically link cells to resist tearing during contraction.

what do gap junctions do?

 allow ion flow for electrical coupling.

Why do cardiac myocytes contain abundant mitochondria?

For continuous aerobic energy production.

Where are T-tubules located in cardiac muscle, and what do they do?

They are large, located at the Z-lines, and help regulate Ca²⁺ entry.

What does it mean that the heart functions as a “functional syncytium”?

Cardiac cells contract as a coordinated unit.

How is the heart controlled by the autonomic nervous system (ANS)?

The ANS modifies heart rate and contractility via sympathetic and parasympathetic inputs.

What are the sympathetic effects on the heart?

↑ HR, ↑ contractility, ↑ conduction velocity (positive chrono-, ino-, and dromotropy).

What are the sympathetic origins, neurotransmitter, and receptors?

Origin: thoracic spinal nerves; NT: norepinephrine; Receptors: β₁-adrenergic.

What are the parasympathetic effects on the heart?

↓ HR, ↓ conduction speed, minimal effect on contractility.

What are the parasympathetic origins, neurotransmitter, and receptors?

Origin: vagus nerve; NT: acetylcholine; Receptors: M₂ muscarinic.

What are the components of the heart's electrical conduction system?

SA node → AV node → Bundle of His → R/L bundle branches → Purkinje fibers.

What is the function of the SA node?

Natural pacemaker (~70–80 bpm).

What is the function of the AV node?

Delays impulse ~0.1 s to allow atrial emptying

What is an ectopic beat?

A premature/abnormal beat originating outside the SA node; often benign.

What can cause ectopic beats?

Caffeine, stress, electrolyte imbalance, ischemia, myocardial disease.

What is the relationship between blood pressure and blood flow?

Flow = ΔP / R; BP = CO × TPR; Flow ↑ with pressure difference and ↓ with resistance.

What is vascular resistance and what determines it?

Opposition to flow; determined by radius, length, viscosity (R ∝ 1/r⁴).

How does resistance affect flow and pressure?

↑ R → ↓ flow (if ΔP constant); ↑ R → ↑ BP (if flow constant).

What is vascular compliance?

Ability of a vessel to stretch (C = ΔV/ΔP).

How does compliance affect blood pressure?

High compliance lowers pulse pressure; low compliance raises systolic/pulse pressure.

What is the cardiac cycle?

One heartbeat (~0.8 s): systole (contraction) + diastole (relaxation).

What happens during systole?

Ventricular pressure ↑, AV valves close (S1), semilunar valves open → ejection.

What happens during diastole?

Ventricular pressure ↓, semilunar valves close (S2), AV valves open → filling.

Define stroke volume (SV), heart rate (HR), and cardiac output (CO).

SV: blood ejected per beat; HR: beats/min; CO = HR × SV (~5 L/min at rest)

What is preload?

Ventricular stretch at end-diastole (EDV); ↑ preload → ↑ contraction (Frank-Starling).

What is afterload?

Resistance ventricles must overcome (arterial pressure); ↑ afterload → ↓ SV.

What are the three primary determinants of stroke volume?

Preload, contractility, afterload.

How does preload influence stroke volume?

↑ EDV → optimal sarcomere stretch → ↑ force → ↑ SV.

How does contractility influence stroke volume?

↑ Ca²⁺ influx (sympathetic/epinephrine) → ↑ SV; decreased contractility → ↓ SV.

How does afterload influence stroke volume?

↑ afterload → ↓ SV & ↑ ESV; ↓ afterload → ↑ SV

What are the two subcellular mechanisms of the Frank-Starling law?

Optimized actin–myosin overlap; increased Ca²⁺ sensitivity.

How do skeletal muscle and respiratory pumps increase venous return?

Muscle contraction compresses veins; inspiration ↓ thoracic pressure → both ↑ preload & CO.

What is pulsatile flow?

Flow fluctuating with heartbeat; occurs in arteries.

What is steady flow?

Continuous, non-pulsing flow in capillaries/veins.

What is laminar flow?

Smooth, layered flow; fastest in center; normal and efficient.

What is turbulent flow?

Chaotic flow with vortices; occurs at high velocity or narrowing; causes murmurs/bruits.

How do pulsatile, steady, laminar, and turbulent flow relate physiologically?

Pulsatile in arteries, steady in microcirculation, laminar is normal, turbulent signals pathology/high stress

What causes the heart sound S1?

Closure of the AV valves (mitral & tricuspid) at the start of ventricular systole.

What causes the heart sound S2?

Closure of the semilunar valves (aortic & pulmonary) at the start of diastole.

What is systolic blood pressure and its typical value?

Pressure during ventricular contraction; ~120 mmHg.

What is diastolic blood pressure and its typical value?

Pressure during ventricular relaxation; ~80 mmHg.

What is mean arterial pressure (MAP) and its typical value?

Average arterial pressure over the cardiac cycle; ~93 mmHg (MAP ≈ DBP + 1/3 PP).

What are the main anatomical features of arteries and their significance?

Thick, elastic, muscular walls → withstand high pressure and maintain flow.

What are the main features of arterioles and their significance?

Smooth muscle–rich; primary resistance vessels → regulate BP & flow distribution.

What are the main features of capillaries and their significance?

One-cell-thick endothelium → optimal for exchange

What are the main features of veins and their significance?

Thin walls, large lumen, valves → low-pressure return & volume reservoir.

What is the relationship between a vessel’s cross-sectional area (CSA) and blood velocity?

Velocity is inversely proportional to total CSA; capillaries (largest CSA) have slowest flow.

How does blood flow through arteries?

Pulsatile, high-pressure flow.

How does blood flow through veins?

Low-pressure, steady flow aided by valves and muscle/respiratory pumps.

What is laminar flow?

Smooth, layered flow with fastest velocity in center.

What is turbulent flow?

Chaotic, noisy flow occurring with high velocity or vessel narrowing.

How is blood pressure measured?

Using a sphygmomanometer with cuff inflation and auscultation.

What produces Korotkoff sounds?

Turbulent blood flow through a partially compressed artery.

Why does blood pressure change along the vascular network?

Pressure drops due to resistance; highest in arteries, lowest in veins.

What are the key equations for pressure, resistance, and flow?

• Flow: Q = ΔP / R

• Resistance: R ∝ 1/r⁴

• MAP = CO × TPR

Why are these equations important for regulating BP?

They show that BP can be adjusted by altering resistance, flow, radius, CO, or TPR.

What happens to blood distribution when moving from lying to standing?

Blood pools in legs → ↓ venous return → ↓ SV → ↓ BP temporarily.

What happens when moving from standing to lying?

Increased venous return → ↑ SV → ↑ BP briefly.

How does the body alter CO and MAP to maintain BP?

Adjusts HR, SV, vessel radius (TPR), and venous return via ANS and hormonal control.

How does the body respond to an acute BP drop?

↑ sympathetic activity → ↑ HR, ↑ contractility, vasoconstriction → restores BP.

How does the body respond to an acute BP increase?

↑ parasympathetic and ↓ sympathetic tone → ↓ HR, vasodilation → lower BP.

How does increased pressure/stretch affect baroreceptor firing?

Increased stretch → increased frequency of action potentials.

What are the main functions of the respiratory system?

Gas exchange (O₂ in, CO₂ out), pH regulation, voice production, olfaction, and protection (filtering, warming, humidifying air).

Where are the lungs located?

In the thoracic cavity, on either side of the mediastinum.

What is the general structure of the lungs?

Spongy, cone-shaped organs with lobes (3 right, 2 left), surrounded by pleura, containing branching airways ending in alveoli.

What is the structural organization of the respiratory system?

Upper respiratory tract (nose, nasal cavity, pharynx) and lower respiratory tract (larynx, trachea, bronchi, lungs).

What is the functional organization of the respiratory system?

Conducting zone (air passageways) and respiratory zone (gas exchange: respiratory bronchioles → alveolar ducts → alveoli).

What is the pathway of air from entry to the alveolus?

Nose → nasal cavity → pharynx → larynx → trachea → bronchi → bronchioles → terminal bronchioles → respiratory bronchioles → alveolar ducts → alveoli.

What is the common term for the pharynx?

Throat.

What is the common term for the larynx?

voice box

What is the common term for the trachea?

windpipe

What are the main anatomical features of the nasal cavity?

External nares, nasal septum, conchae/turbinates, meatuses, mucosa, olfactory region.

What are the functions of the nasal cavity?

Warm, humidify, filter incoming air; house olfactory receptors; resonance for speech.