Week 4&5 (Cardiovascular System 1&2) Flashcards
(43 cards)
Main function of the Cardiovascular System
The cardiovascular system transports blood, oxygen, nutrients, hormones, and other vital substances to tissues and organs throughout the body while simultaneously removing carbon dioxide and waste products.
The major components of the Cardiovascular System
Heart: The pump that propels blood through the body.
Blood Vessels: Serve as the network of tubes that carry blood to and from various tissues.
arteries (distributing system)
capillaries (exchange system)
veins (collecting system)
Blood: The transport medium that delivers essential materials and removes waste.
Double Circulation Loop
The cardiovascular system consists of two main circuits:
Pulmonary Circuit: Carries blood between the heart and lungs for gas exchange. Blood releases carbon dioxide and picks up oxygen.
Systemic Circuit: Delivers oxygenated blood from the heart to all body tissues and returns deoxygenated blood back to the heart.
Anatomy of the Heart
The heart is a muscular organ roughly the size of a fist
located in the mediastinum (the central compartment of the thoracic cavity).
2/3rds of the heart lies to the left of the body’s midline.
Heart Structure
Myocardium: Middle layer composed of cardiac muscle responsible for contraction.
Four Chambers: 2 atria & 2 ventricles
Atria (Right and Left): Receive blood from veins and act as the heart’s “receiving chambers.”
Ventricles (Right and Left): Pump blood out of the heart; known as “pumping chambers.”
Septum: A muscular wall separating the right and left sides of the heart, preventing mixing of oxygenated and deoxygenated blood.
Valves: Ensure unidirectional blood flow.
Atrioventricular (AV) Valves: Tricuspid (right) and Mitral/Bicuspid (left).
Semilunar Valves: Pulmonary (right) and Aortic (left).
Comparison Between Ventricles
Right Ventricle: Pumps blood into the pulmonary circuit at lower pressure since it only needs to reach the lungs.
Left Ventricle: Thicker wall (3x thicker) and more powerful, as it pumps blood into the systemic circuit at higher pressures to deliver blood throughout the body.
Atrioventricular Valves (AV)
Open when atrial pressure exceeds ventricular pressure to allow blood to flow into the ventricles.
Close when ventricular pressure surpasses atrial pressure at the beginning of ventricular contraction (systole), creating the first heart sound (“lub”). This sound is generated by vibrations of blood and the ventricular wall.
Semilunar Valves
Open when ventricular pressure exceeds the pressure in the aorta and pulmonary trunk, allowing blood to flow out of the heart.
Close when aortic and pulmonary pressure surpasses ventricular pressure during ventricular relaxation (diastole), producing the second heart sound (“dub”).
Pathway of Blood Through the Heart
Inferior or Superior vena cava
Right atrium
Tricuspid valve
Right ventricle
Pulmonary semilunar valve
Pulmonary arteries
Lungs
Pulmonary veins (right & left)
Left atrium
Bicuspid valve
Left ventricle
Aortic semilunar valve
Aorta
Arteries
Capillaries
Veins
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Vascular System
The vascular system consists of a closed network of blood vessels that circulate blood throughout the body.
Types of Blood Vessels
Arteries: Carry oxygenated blood away from the heart (except pulmonary arteries, which carry deoxygenated blood to the lungs). Arteries have thick walls to withstand high pressure.
Capillaries: The smallest blood vessels, responsible for the exchange of oxygen, nutrients, and waste products between blood and tissues. Capillaries have thin walls, only one cell layer thick, allowing for efficient exchange.
Veins: Return deoxygenated blood to the heart (except pulmonary veins, which carry oxygenated blood from the lungs). Veins have thinner walls and operate under lower pressure compared to arteries. They have valves to prevent the backflow of blood, aided by skeletal muscle contractions.
Cardiac Muscle
Cardiac muscle tissue is specialized to ensure that the heart contracts rhythmically and efficiently.
Structure and Histological Properties
Cardiac Muscle Cells: Short, branched, and striated, containing a single central nucleus.
Intercalated Discs: Specialized connections between cells that contain:
* Gap Junctions: Allow electrical impulses to spread quickly between cells.
* Desmosomes: Provide mechanical strength by anchoring cells together.
Functional Characteristics
Syncytium: Cardiac muscle acts as a single functional unit.
Involuntary Control: Contractions occur without conscious control.
Spontaneous Depolarization: Can generate electrical impulses without external stimulation.
Types of Cardiac Muscle Cells
Contractile Muscle Fibers (99%): Generate the force needed for pumping blood.
Specialized Conducting Cells (1%): Facilitate rapid transmission of electrical impulses.
* Key components: Sinoatrial (SA) node, Atrioventricular (AV) node, Bundle of His, Purkinje Fibers.
Coronary Circulation
The heart receives blood through the coronary arteries, which arise from the base of the aorta.
Venous blood from the heart muscle drains into the right atrium.
During exercise, blood flow to the heart increases up to nine times the resting level to meet increased oxygen demand.
Electrocardiogram (ECG)
An ECG records the heart’s electrical activity using electrodes placed on the skin.
Components of a Normal ECG
P Wave: Atrial depolarization
QRS Complex: Ventricular depolarization (and simultaneous atrial repolarization)
T Wave: Ventricular repolarization
PR Interval: Time taken for the impulse to travel through the AV node and bundle branches
ST Segment: Represents the time when the ventricles are contracting and emptying
Normal heart rate
60-100 beats/min
Sinus bradycardia
slower than normal heart rate slower than 60 beats/minute
Sinus tachycardia
faster than normal heart rate faster than 100 beats/minute
Extra Cardiovascular Facts
-The normal pacemaker of the heart is the sinoatrial (SA) node.
-Contraction of cardiac muscle is called systole.
-Relaxation of cardiac muscle is called diastole.
-The 1st heart sound is caused by the closing of the atrioventricular (AV) valves (mitral and tricuspid valves).
-The 2nd heart sound is caused by the closing of the semilunar valves (aortic and pulmonary valves).
-Veins hold the greatest volume of blood
-The normal blood pressure is less than 120/80 mmHg.
Cardiac Cycle
The sequence of cardiac events in a single heartbeat
* both mechanical and electrical events.
Each cardiac cycle begins with an action potential generated in the sinoatrial (SA) node.
Phases:
* Systole (Contraction)
* Diastole (Relaxation)
Associated with:
Pressure & volume changes in the heart
Opening & closing of heart valves
Electrocardiogram ECG) changes
Duration of Cardiac Cycle
of heart beats in one (1) minute normal value: 60 beats/minute - 100 beats/minute
Formula: Normal Duration of the Cardiac Cycle Time= 60 / heart rate beats/min
heart rate: # of heart beats in one (1) minute normal value: 60 beats/minute - 100 beats/minute
at normal resting heart rate of 75 beats/min, cardiac cycle time is- 60 / 75 beats/min = 0.8s
