Cardiovascular System Overview

Cardiovascular System Lecture Notes

• Veins carry blood to the heart, but they have a wider diameter and low pressure, requiring assistance from skeletal and respiratory pumps.
• The heart is a muscular pump that supplies blood across the body. It has 4 chambers connected to various blood vessels with valves that regulate blood flow.
• The heart pumps blood through two simultaneous circuits: the systemic and pulmonary circuits.
• Blood flows through the heart twice—deoxygenated through the right side and oxygenated through the left side.

Lecture Outcomes (Cardiovascular System)

• Learn about the cardiac cycle.
• Understand how the cardiac conduction system coordinates contraction.
• Link learned concepts to disease.

Cardiac Cycle

• Atrial Systole:
  • Atria contract, sending blood to the ventricles.
  • Blood flows from the pulmonary artery and aorta.
• Ventricular Systole:
  • Ventricles contract, pushing blood to the pulmonary artery and aorta.
  • AV valves close, semilunar valves open.
• Diastole:
  • The entire heart relaxes.
  • Blood passively flows into the heart.
  • AV valves open, semilunar valves close.

Cardiac Cycle (3 Steps)

• Atrial Systole: Both atria contract, opening AV valves, blood fills ventricles. Semilunar valves are closed.
• Ventricular Systole: Both ventricles contract, closing AV valves, opening semilunar valves, blood pushed into pulmonary artery and aorta.
• Diastole: Atria and ventricles relax, ventricle pressure falls-> semilunar valves close, AV valves open, passive inflow of blood.

Blood Flow

• Blood enters arteries during systole, expanding artery walls.
• Blood leaves through the arteries into capillaries, and passively recoils.
• This pulse can be felt in the wrist.

Link to Disease: Hypertension

• Blood pressure is the force blood exerts on vessel walls, measured by a sphygmomanometer.
• Normal blood pressure is 90-120 systolic and 60-80 diastolic.
• Hypertension (high blood pressure) puts pressure on the cardiovascular system.
• Factors associated with hypertension are age, smoking, and lifestyle.

Heart Sounds

• "Lub": Sound of the two atrioventricular valves closing (ventricular systole).
• "Dub": Sound of the aortic and pulmonary semilunar valves closing (ventricular diastole).
• "Lub Dub" represents a complete cardiac cycle.

Cardiac Conduction System

• Coordinates the cardiac cycle.
• Initiated and distributed by specialized cardiac muscle cells (pacemaker cells)
• Sinoatrial (SA) node is the pacemaker. It spontaneously and rhythmically initiates electrical signals for atrial contraction.
• Signals travel to both atria via conducting muscle fibers.
• Atrioventricular (AV) node delays signal for adequate atrial emptying prior to ventricular contraction.
• AV bundle carries the signals to the ventricles.
• Purkinje fibres carry the impulse to the myocardial cells, enabling ventricular contraction.

Link to Disease: Artificial Pacemaker

• Heartbeat problems (arrhythmias) can be caused by issues with the transmission of electrical impulses.
• Congenital heart defects and heart failure can lead to an abnormal heartbeat.
• An artificial pacemaker sets a regular heartbeat for effectively pumping blood.

Link to Disease: Heart Attack

• A heart attack occurs when a region of the heart is starved of oxygen due to inadequate blood flow.
• Symptoms of a heart attack include chest tightness /pressure, pain down the left arm, and difficulty breathing.
• Heart attacks cause permanent damage to the heart tissue.
• Treatments include reopening blocked blood vessels, using clot-busting drugs, and heart transplants.

Video Review

• Refer to video on D2L for further information.

Question Break 1 (Matching)

• Match the following terms relating to heart function.

Question Break 2 (Matching)

• Match the following urinary system structures with their corresponding functions. (e.g Kidney: urine formation)

Urinary System Lecture Notes

• Function: The primary function of the urinary system is to excrete waste products and maintain fluid homeostasis.
• Components:
  • Kidneys: Produce urine.
  • Ureters: Transport urine from kidneys to bladder.
  • Bladder: Stores urine temporarily.
  • Urethra: Transports urine out of the body.
• Flow: Urine is produced in the kidneys, travels down the ureters to the bladder, where it is stored. The bladder then excretes urine out of the body through the urethra.
• Fluid Homeostasis: The urinary system regulates blood composition, volume, and pressure.

Urinary Incontinence

• Conscious control over urination is maintained by the brain's control of the urinary sphincter.
• Lack of voluntary control over urination is called urinary incontinence.
• Urinary incontinence is common in infants because of undeveloped nervous connections.
• Pregnancy can also cause temporary urinary incontinence due to the expanding uterus putting pressure on the sphincter.

Practice Questions

• Answers to practice questions about cardiac and urinary system functions.