CHP 14 new

What is stroke volume (SV)?

Stroke volume is the amount of blood ejected by one ventricle per beat. SV = EDV − ESV (end-diastolic volume minus end-systolic volume). Example: During exercise, SV increases to deliver more oxygen; in heart failure, SV decreases causing fatigue.

What is cardiac output (CO) and what influences it?

Cardiac output is the amount of blood pumped per minute. CO = HR × SV. It is influenced by heart rate and stroke volume. Example: Exercise increases both HR and SV, raising CO to meet oxygen demand.

What are positive vs negative chronotropes?

Chronotropes affect heart rate. Positive chronotropes increase HR (sympathetic stimulation, epinephrine, caffeine). Negative chronotropes decrease HR (parasympathetic activity, beta-blockers). Example: Coffee increases HR; beta-blockers lower HR in hypertension.

What are positive vs negative inotropes?

Inotropes affect contractility (force of contraction). Positive inotropes ⬆ sv & increase force (epinephrine, calcium, digitalis). Negative inotropes ⬇ sv &decrease force (beta-blockers, calcium channel blockers). Mechanism: they change Ca²⁺ availability in cardiac cells. Example: Positive inotropes are used in heart failure.

What is the atrial reflex (Bainbridge reflex)?

Increased venous return stretches atrial walls → baroreceptors in atria fire → stimulate sympathetic activity → increase HR to prevent overfilling. Example: IV fluids increase HR.

What is venous return?

Venous return is the amount of blood returning to the heart. It determines EDV (end-diastolic volume) and directly affects stroke volume. Example: Exercise increases venous return, increasing SV.

What is pulse pressure?

Pulse pressure = systolic − diastolic pressure. It reflects arterial elasticity and stroke volume. Example: 120/80 → PP = 40. High PP may indicate stiff arteries.

What is the Frank-Starling Law?

As EDV (preload) increases, ventricular muscle stretches more → stronger contraction → increased SV. Mechanism: optimal overlap of actin and myosin. Example: Increased venous return during exercise increases SV.

What is cardiac reserve?

Cardiac reserve is the ability to increase CO above resting level. Healthy individuals can increase CO 4–7×. Example: Athletes have high reserve; heart disease reduces it.

What affects heart rate vs stroke volume?

Heart rate is affected by autonomic nervous system, hormones, and reflexes. Stroke volume is affected by preload (EDV), contractility (inotropes), and afterload. Example: Dehydration lowers SV; stress increases HR.

What is preload vs afterload?

Preload = EDV (volume of blood in ventricle before contraction, determines stretch). Afterload = pressure the ventricle must overcome to eject blood (related to arterial pressure and resistance). Example: High BP increases afterload, making the heart work harder.

What is perfusion?

Perfusion is the delivery of blood (oxygen and nutrients) to tissues. It depends on blood pressure and flow (MAP). Example: Poor perfusion causes dizziness or organ failure.

What is hydrostatic pressure?

Hydrostatic pressure is the force exerted by fluid pushing outward (blood pressure in capillaries). It promotes filtration (movement of fluid out of capillaries). Example: High BP increases fluid leakage into tissues.

What is oncotic (colloid osmotic) pressure?

Oncotic pressure is the pulling force exerted by plasma proteins (especially albumin) that draws water into capillaries. It promotes reabsorption. Example: Low albumin causes edema.

What is net filtration pressure (NFP) and bulk flow?

NFP = (HPb − HPif) − (COPb − COPif). It determines fluid movement across capillaries. Filtration occurs at the arterial end; reabsorption occurs at the venous end. Example: If NFP favors filtration too much, edema occurs.

What is the role of albumin and the lymphatic system?

Albumin maintains oncotic pressure to pull fluid into blood. The lymphatic system returns excess fluid (10–15%) not reabsorbed back to circulation. Example: Blocked lymphatics cause swelling.

What is blood pressure (BP)?

Blood pressure is the force of blood against vessel walls. BP ∝ CO × total peripheral resistance (TPR). Example: Increased resistance raises BP.

What is the blood pressure gradient?

It is the difference in pressure that drives blood flow (from arteries to veins). Example: Blood flows from ~93 mmHg in arteries to ~0 mmHg in vena cava.

What is systolic vs diastolic pressure?

Systolic pressure is the pressure during ventricular contraction (highest). Diastolic pressure is during relaxation (lowest). Example: 120/80 → systolic = 120, diastolic = 80.

What is mean arterial pressure (MAP)?

MAP = diastolic pressure + 1/3 pulse pressure. It represents average pressure driving perfusion. Example: MAP < 60 mmHg leads to inadequate organ perfusion.

What affects venous return?

Venous return depends on pressure gradient, skeletal muscle pump, and respiratory pump. Example: Standing still reduces venous return, causing blood pooling.

What is the respiratory pump?

Breathing changes thoracic and abdominal pressures to help move blood toward the heart. Inhalation pulls blood upward; exhalation pushes it toward the heart. Example: Deep breathing improves circulation.

What is vascular resistance and what affects it?

Vascular resistance is opposition to blood flow. It depends on viscosity (thickness), vessel length, and vessel radius (most important, radius⁴ relationship). Example: Vasoconstriction greatly increases resistance and BP.

What controls blood pressure short-term?

The nervous system via baroreceptors and chemoreceptors provides rapid control. Example: When standing up quickly, these reflexes prevent fainting.

What influence does sympathetic input have on heart and vessels?

Sympathetic stimulation increases heart rate (positive chronotropy), contractility (positive inotropy), and causes vasoconstriction → increases CO and BP. Example: Stress increases HR and BP.

What are baroreceptors?

Baroreceptors are stretch-sensitive receptors in the aortic arch and carotid sinuses. Increased BP → increased firing → decrease sympathetic output. Decreased BP → decreased firing → increase sympathetic output. Example: Helps stabilize BP quickly.

What is the function of atrial natriuretic peptide (ANP)?

ANP is released when atria are stretched. It lowers BP by causing vasodilation and increasing excretion of sodium and water (decreasing blood volume). Example: Helps reduce high blood volume.

What are important clinical conditions to know?

Hypertension (high BP), hypotension (low BP), edema (fluid imbalance), heart failure (low CO), atherosclerosis (increased resistance). Example: Atherosclerosis narrows vessels, increasing BP and workload on the heart

What is hypotension and orthostatic hypotension?

Hypotension is chronically low blood pressure.

• Hypotension:
  

  • Chronic low blood pressure

  • Systolic < 90 mmHg and/or diastolic < 60 mmHg

  • Symptoms: fatigue, dizziness, fainting

• Orthostatic hypotension:
  

  • Sudden drop in blood pressure when standing up quickly

  • Symptoms: dizziness, light-headedness, fainting

  • Cause: blood pressure regulation (baroreflex) is too slow to ad

What is hypertension and what are the normal and stage ranges?

Hypertension (high blood pressure) is a condition of elevated arterial pressure.

• Normal: < 120/80 mmHg

• Stage 1 hypertension: 130–139 systolic OR 80–89 diastolic

• Stage 2 hypertension: ≥ 140 systolic OR ≥ 90 diastolic

Quick memory tip:

👉 “120 is normal, 130 is warning, 140 is high risk”

hypertension key risks?

Over time, the constant high pressure damages blood vessels, the heart, and other organs.

Key Risks include: Heart. disease and MI, Stroke, Kidney damage/failure, Vision Loss, Cognitive decline/Dementia and more.