Circulatory system

bio II

List the three main components of the CVS, the main function of the CVS and what gets transported by the CVS

Main components:

1. Heart: provides the force to move blood

2. Arteries: carry blood AWAY from heart

3. Veins: carry blood TO heart

4. Blood

Main function and what gets transported:

• Transportation of…

  • O₂ + CO₂

  • Wastes

  • Nutrients

  • Hormones

Describe the layers of the heart tissue and the protective layers that surround the heart

Pericardium:

• Double membrane sac

  • Visceral pericardium: inner layer

  • Parietal pericardium: outer layer (w/ fibrous layer around it)

Protective layers:

• Epicardium: outermost layer of the heart

• Myocardium: middle layer of the heart

• Endocardium: innermost layer of the heart

Describe the flow of blood (both oxygenated and deoxygenated blood) through the heart including the major vessels attached to the heart

Deoxygenated blood (right side):

• Superior + inferior vena cava → right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary artery

Oxygenated blood (left side):

• Pulmonary veins → left atrium → mitral (bicuspid) valve → left ventricle → aortic valve → aorta

Identify the major valves of the heart

• Tricuspid valve

• Pulmonary valve

• Mitral valve

• Aortic valve

Describe the general physiology of the heart including the two systems that control the heartbeat in the path of electrical impulse through the intrinsic conduction system of the heart

General physiology of the heart:

• the heart is a muscular pump that moves blood through the body. It works by:

  • Contracting (systole) → pushes blood out

  • Relaxing (diastole) → fills with blood

Two systems that control heartbeat:

1. Intrinsic control (internal system)

• the heart can beat on its own without brain input

• This is due to special cells that create electrical signals

• Called the intrinsic conduction system

2. Extrinsic control (external nervous system) - controlled by the autonomic nervous system:

• sympathetic nervous system

  • Increases heart rate (“fight or flight”)

• Parasympathletic nervous system

  • Decreases heart rate (“rest and digest”)

Path of electrical impulse through the heart:

1. SA Node

• located in the right atrium

• Called the natural pacemaker

• Starts the heartbeat

2. AV Node

• Receives the signal from the SA node

• Delays the signal briefly so atria can fully contract

3. Bundle of His

• conducts the signal into the ventricles

4. Right and Left Bundle Branches

• carry the signal down each side of the heart

5. Purkinje Fibers

• spread the signal through venricles

• Cause ventricles to contract and pump blood

Describe why nodal tissue is different than any other tissue in the body (esp. the Sinoatrial node)

It can create its own electrical signals without input from the nervous sustem.

In the SA node, cells slowly build up electrical charge and automatically fire at a regular rate, make it the heart’s natural pacemaker

Unlike other heart cells, nodal cells are designed for signal generation, not strong contraction

describe how heart rate is measured and understand the factors that can influence heart rate

Measured by:

• taking a pulse (feeling arterial blood flow), at the wrist (radial artery) or neck (carotid artery)

• Counting beats for 15 seconds and multiplying by 4

• Using devices like a heart rate monitor, smartwatch, or ECG

Factors that influence:

• exercise

• Stress or emotions

• Autonomic nervous system

• Body temperature

• Hormones

• Fitness level

• Age

• Medications/stimulants

Describe impulse and calcium disorders

Happen when the heart’s electrical conduction system doesn’t work correctly, causing abnormal heart rhythms.

• Too fast heartbeat (tachycardia)

• Too slow heartbeat (bradycardia)

• Irregular rhythm (atrial fibrillation)

Describe the stages of the cardiac cycle and how the stages relate to the contraction and relaxation of both the atria and ventricles

1. Atrial systole (atria contract)

• atria contract

• Ventricles are relaxed

• Blood is pushed from atria into ventricles

2. Ventricular systole (ventricles contract)

• ventricles contract

• Atria relax

• Blood is forced out:

  • Right ventricle → lungs

  • Left ventricle → body

• AV valves close to prevent backflow

3. Diastole (full relaxation phase)

• atria and ventricles both relax

• Blood flows into atria from veins

• AV valves open and ventricles begin filling passively

How it all works together:

• atria contract first → fill ventricles

• Ventricles contract second → pump blood out

• Both relax → heart refills

Explain the connection between the intrinsic conduction system and the cardiac cycle

• the conduction system creates and spreads the electrical impulse

• The cardiac cycle is the mechanical response (contraction/relaxation) to that impulse

Explain the role of the heart valves in the cardiac cycle including sounds make by valves, the definition of iso-volumetric state and where blood flows when each valve opens

Role of heart valves in the cardiac cycle:

• heart valves make sure blood flows one direction only through the heart and prevent backflow during contraction and relaxation

Valves sounds:

• “Lub”

  • Caused by AV valves closing

  • Happens when ventricles start contracting

  • AV valves: mitral + tricuspid close

• “Dub”

  • Caused by semilunar valves closing

  • Happens when ventricles relax

  • Semilunar valves: aortic + pulmonary close

Isovolumetric state:

When the ventricles are contracting or relaxing, but no blood is moving in or out because all valves are closed

• isovolumetric contraction: ventricles build pressure semilunar valves open

• Isovolumetric relaxation: ventricles relax before AV valves open

Where blood flows when valves open

• AV valves (tricuspid + mitral) open

  • Blood flows atria → ventricles

• Semilunar valves (pulmonary +aortic) open

  • Blood flows:

    • Right ventricle → pulmonary artery → lungs

    • Left ventricle → aorta → body

Describe the general cycle of blood through the body including pulmonary, systemic, and micro circulation through the capillaries as well as the flow of blood through the heart

1. From body to heart (deoxygenated):

Body → vena cava → right atrium → tricuspid valve → right ventricle

2. Pulmonary circulation (to lungs):

Right ventricle → pulmonary artery → lungs (get O₂, drop CO₂) → pulmonary veins → left atrium

3. Back through heart to body (oxygenated):

Left atrium → mitral valve → left ventricle → aorta → body

4. Microcirculation (capillaries):

In capillaries, oxygen / nutrients go to cells, wastes enter blood

Describe the microscopic structure of a blood vessel, including the three tunics

1. Tunica intima (innermost)

• made of endothelium (thin, smooth cells)

• Reduces friction so blood flows easily

2. Tunica media (middle)

• made of smooth muscle + elastic fibers

• Controls vasoconstriction (narrowing) and vasodilation (widening)

• Helps regulate blood pressure and flow

3. Tunica externa (outer layer)

• made of connective tissue (collagen)

• Protects and anchors the vessel to surrounding tissues

Discuss the major differences in the structure of veins, arteries, and capillaries

arteries:

• thick walls, esp the tunica media