Topic 23- Circulation

What are the three basic components of any circulatory system?

Fluid, interconnecting vessels, and a pump.

What is the key difference between an open and a closed circulatory system?

Open systems bathe tissues directly with hemolymph; closed systems keep blood confined to vessels.

What type of circulatory system do vertebrates have?

Closed circulatory system, also called the cardiovascular system.

What are the three types of blood vessels in vertebrate circulation?

Arteries (away from heart), capillaries (exchange), veins (toward heart).

What distinguishes arteries and veins?

Direction of blood flow — not oxygen content.

What is the sequence of blood flow in the cardiovascular system?

Arteries → Arterioles → Capillaries → Venules → Veins.

What kind of heart and circulation do fish have?

Two-chambered heart; single circulation: heart → gills → body → heart.

What are key features of amphibian circulation?

Three-chambered heart, double circulation, pulmocutaneous circuit for skin gas exchange.

How is mammalian and bird circulation adapted for high metabolism?

Four-chambered heart with completely separate pulmonary and systemic circuits.

What is cardiac output?

The volume of blood pumped per minute by the left ventricle (heart rate × stroke volume).

What causes the "lub" and "dub" sounds of the heart?

"Lub" = AV valves closing; "Dub" = Semilunar valves closing.

What is the function of the SA node?

Acts as the heart’s pacemaker, initiating electrical impulses for contraction.

What is the role of the AV node in the heartbeat?

Delays the impulse so the atria can fully contract before ventricles.

How is heart rate regulated by the nervous system?

Sympathetic nerves speed it up; parasympathetic nerves slow it down.

How does the endocrine system affect heart rate?

Hormones like epinephrine increase heart rate during stress.

What are the three layers of arteries and veins (from inner to outer)?

Endothelium → Smooth muscle → Connective tissue.

How do capillaries differ from arteries and veins?

Capillaries have only a thin endothelium and basal lamina, allowing gas exchange.

What forces control fluid movement in capillaries?

Blood pressure (pushes fluid out) and osmotic pressure (draws fluid in).

Why is the lymphatic system necessary?

It returns leaked interstitial fluid to the blood, absorbs dietary lipids, and aids immune defense.

What is lymph made of?

White blood cells, filtered fluid, and sometimes pathogens.

What happens if lymphatic drainage is blocked?

Edema (swelling due to fluid buildup).

How does the lymphatic system differ from the blood circulatory system?

Lymph moves one-way, under low pressure without a central pump (uses skeletal muscle and valves).

What sequence does lymph follow to return to the bloodstream?

"Crazy Little Nuns Dance Viciously Happy."

• Crazy → Lymph Capillaries

• Little → Larger Lymph Vessels

• Nuns → Lymph Nodes (filtering)

• Dance → Lymph Ducts

• Viciously → Major Veins

• Happy → Heart

What happens at the capillary arterial end vs. venous end?

Arterial end: Blood pressure > osmotic pressure → fluid exits. Venous end: Osmotic pressure > blood pressure → fluid reenters.

ABOE and VOBR

Organizer 1: Sequence Types of Circulatory Systems

(Evolutionary progression of circulation types)

1. No circulatory system (small/simple animals → diffusion only).

2. Open circulatory system:

   • Hemolymph bathes tissues directly.

3. Closed circulatory system:

   • Blood confined to vessels.

   • More efficient delivery of oxygen/nutrients.

Organizer 2: Compare and Contrast Circulatory Systems [Fluid, Containment, Pressure, Efficiency, Examples]

Feature	Open Circulatory System	Closed Circulatory System
Fluid	Hemolymph	Blood
Containment	Bathes tissues directly	Confined to vessels
Pressure	Low	High
Efficiency	Lower	Higher
Examples	Insects, mollusks	Vertebrates, annelids

Organizer 3: Sequence Human Heart Function

(Pathway of electrical and mechanical heart activity)

1. SA Node generates impulse (pacemaker).

2. Atria contract simultaneously.

3. Signal delayed at AV Node.

4. Impulse moves through Bundle branches.

5. Signal spreads via Purkinje fibers.

6. Ventricles contract (blood pumped to lungs and body).

7. Valves (AV and Semilunar) open/close to prevent backflow.

Organizer 4: Hypothesize and Diagnose the Impact of Variability on Human Heart Function [SA node damage, Sympathetic nervous activation, Parasympathetic Activation, Valve Malfunction, Fever or Increased Body Temperature]

Variable Change	Hypothesis/Diagnosis
SA node damage	Slower or irregular heart rate (need pacemaker)
Sympathetic nervous activation	Increased heart rate and force of contraction (stress/exercise)
Parasympathetic activation	Decreased heart rate (rest/digestion)
Valve malfunction	Heart murmur; potential backflow; decreased cardiac efficiency
Fever or increased body temperature	Increased heart rate

Organizer 5: Compare and Contrast Types of Blood Vessels [Direction, Wall Structure, Pressure, Special Features]

Feature	Arteries	Capillaries	Veins
Direction	Away from heart	Connect arteries to veins	Toward heart
Wall Structure	Thick, muscular, elastic	Single endothelial layer	Thin, some muscle, valves present
Pressure	High	Medium to low	Low
Special Features	Stretch to handle pressure	Site of exchange	Valves prevent backflow

Organizer 6: Sequence Human Blood Flow

Path of blood through the body)

1. Right atrium (receives deoxygenated blood).

2. Right ventricle (pumps to lungs via pulmonary artery).

3. Lungs (oxygenates blood).

4. Left atrium (receives oxygenated blood).

5. Left ventricle (pumps to body via aorta).

6. Arteries → arterioles → capillaries (gas/nutrient exchange).

7. Venules → veins → vena cava → right atrium (cycle repeats).

Organizer 7: Sequence the Function of the Lymphatic System

(How lymph moves and functions)

1. Blood plasma leaks into tissues → forms interstitial fluid.

2. Lymphatic capillaries absorb interstitial fluid → now called lymph.

3. Lymph moves through lymphatic vessels.

4. Lymph passes through lymph nodes (filtered for pathogens).

5. Lymph re-enters bloodstream via lymph ducts into major veins.

Organizer 8: Hypothesize and Diagnose the Impact of Variability on the Lymphatic System [Lymph Node Blockage, Reduced Lymph Movement, Overactive Lymph System, Malfunctioning Valves in Lymph Vessels]

Variable Change	Hypothesis/Diagnosis
Lymph node blockage	Localized swelling (edema), possible infection risk
Reduced lymph movement (e.g., inactivity)	Edema, poor immune surveillance
Overactive lymph system (autoimmune disease)	Inappropriate immune responses
Malfunctioning valves in lymph vessels	Poor lymph drainage and systemic swelling

Organizer 9: Compare and Contrast Lymphatic and Blood Systems [Fluid Name, Function, Pressure, Pump, Fluid Path, Components]

Feature	Lymphatic System	Blood Circulatory System
Fluid Name	Lymph	Blood
Function	Returns fluid, immune defense, absorbs fats	Distributes oxygen, nutrients, removes wastes
Pressure	Low pressure	High pressure
Pump	Skeletal muscle contraction, valves	Heart
Fluid Path	One-way (toward heart)	Closed loop (heart → body → heart)
Components	Lymph vessels, nodes	Arteries, veins, capillaries