Heart Anatomy and Physiology

Heart Medication and Introductory Remarks

• Mention of medication and a dangerous lightning-like feeling in the face, which the speaker finds concerning.

• A nurse who had surgery to cut a nerve.

Course Logistics and Announcements

• Beginning of Unit 3, focusing on the heart and blood vessels.

• Chapter 20 is the starting point for the heart.

• Unit 2 exam opens Friday and is due Sunday.

• Practice exam is available (opened early that morning) with a one-time access limit.

• Review on Wednesday; potential topics include endocrine glands, hormones, and their targets.

• Homework 2 is due Wednesday night; early submission allows for earlier grading.

• Homework and pop quizzes combined are equivalent to an exam grade.

  • Aim to maximize points as they significantly impact the overall grade.

Early Alerts and Encouragement

• Early alerts sent out to students to indicate academic standing and need for help.

• Both positive and constructive messages are sent.

• Students are encouraged to seek help to improve grades before midterms.

Heart Drawing Activity

• Students will draw the basic structure of the interior of the heart.

• Emphasis on understanding, not artistic skill.

• Heart has four chambers or spaces.

  • Two on top (atria) and two on the bottom (ventricles).

Drawing the Heart

• Instructor demonstrates drawing two upper and two lower chambers on the board.

Atria

• Upper chambers are called atria (atrium is singular).

• Atria are receiving chambers, meaning blood flows into them from veins.

Ventricles

• Lower chambers are called ventricles.

• Ventricles are discharging chambers; they pump or send blood out.

Blood Vessels and Circulation

• Veins return blood to the heart, regardless of oxygen content.

  • Superior and inferior vena cava return blood to the right atrium.

  • Coronary sinus also returns blood to the right atrium during coronary circulation (covered in lab).

• Pulmonary veins return blood to the left atrium.

  • Carry oxygen-rich blood from lungs

  • Blood sent to lungs for diffusion of gases (CO2 out, oxygen in).

Valves

• Valves allow for one-way flow of blood from atria to ventricles.

• Tricuspid valve: Located between the right atrium and right ventricle; has three cusps.

• Mitral or bicuspid valve: Located between the left atrium and left ventricle; has two cusps.

• Blood passively moves from atria to ventricles when valves are open.

• Atrial contraction pushes remaining blood into ventricles.

Arteries

• Arteries carry blood away from the ventricles.

• Pulmonary trunk

  • Carries blood away from the right ventricle.

  • Branches into pulmonary arteries that go to the lungs.

• Aorta

  • Carries blood away from the left ventricle.

  • Arches and descends.

Semilunar Valves

• Pulmonary semilunar valve:

  • Located between the right ventricle and the pulmonary trunk.

• Aortic semilunar valve:

  • Located between the left ventricle and the aorta.

• Semilunar valves prevent backflow of blood from receiving vessels into ventricles.

Circulation Through the Lungs

• Right lung and left lung shown in the drawing to illustrate pulmonary circulation

• Oxygen-poor blood goes to lungs, gives up CO_2, picks up oxygen, returns via pulmonary veins

Complete Blood Flow

• Oxygen-poor blood

  • Enters right atrium via vena cava (inferior and superior)

  • Passes through the tricuspid valve into the right ventricle

  • Goes through the pulmonary semilunar valve into the pulmonary trunk

  • Splits into pulmonary arteries, goes to pulmonary capillaries in lungs.

• Oxygen-rich blood returns via pulmonary veins into left atrium

  • Goes through bicuspid (mitral) valve into left ventricle

  • Forces open the aortic semilunar valve

  • Blood goes into aorta and then through systemic capillaries

  • Oxygen to the cells of the tissues

  • Carbon dioxide pick-up, return to right atrium = cycle repeats.

Heart as a Two-Sided Muscular Pump

• The heart functions as a two-sided pump, with the right and left sides working simultaneously. Both circuits (pulmonary and systemic) are integrated.

Student Drawings and Key Structures

• Checking student drawings and noting correct depictions of the interventricular wall.

  • Discussing the possibility of adding details like papillary muscles and chordae tendineae later.

• Highlighting the importance of knowing the flow of blood and the basic differences between the atria and ventricles for the upcoming exam.

Additional Valves

• Pulmonary semilunar valve between the right ventricle and pulmonary trunk.

• Aortic semilunar valve between the left ventricle and the aorta.

Muscular Pump and Pressure Gradients

• The movement of blood relies on a pressure gradient.

• Increase pressure in the ventricles to eject blood.

• Decrease pressure to open AV valves.

• Pressure differences between arteries, capillaries, and veins facilitate blood movement.

Cardiac Muscle Tissue Characteristics

• Cardiac muscle tissue typically has a single nucleus per cell.

• Striations are present, similar to skeletal muscle tissue.

• Branching pattern of cardiac muscle tissue.

• Intercalated discs are darkly stained regions that allow for fast transmission of information in the form of ions.

  • Gap junctions facilitate quick communication between cells.

  • Desmosomes help resist stretching and keep cells together during contraction.

Involuntary Control and Intercalated Discs

• Cardiac muscle tissue is under involuntary control.

• Intercalated discs are a combination of desmosomes and gap junctions.

  • Desmosomes anchor adjacent cells together.

  • Gap junctions allow for movement of ions and molecules between cells, allowing cardiac muscle tissue to function as one big mass (functional syncytium).

Close Review of Intercalated Discs

• Intercalated discs are composed of desmosomes (anchoring cells) and gap junctions (allowing ion movement).

• Cells are acting mechanically, chemically, and electrically as close to one unit as possible.

Heart Location

• Roughly the size of a fist.

• Located slightly left of center.

• Apex points inferiorly and laterally.

• Contained within the pericardial sac (fibrous pericardium), which protects and keeps the heart in place.

  • Attached to the diaphragm via fibrous network.

Fibrous Pericardium

• Outermost portion protecting and stabilizing the heart.

• Attaches heart to the diaphragm.

Serous Membrane

• Parietal portion lines the cavity.

• Visceral portion covers the organ

• Space in between them is filled with fluid (Pericardial Fluid).

Pericardium

• Composed of two portions: parietal and visceral.

• Parietal portion lines the pericardial cavity.

• Visceral portion (epicardium) is on the surface of the heart.

• Pericardial fluid fills the space between the parietal and visceral layers.

• Epicardium is the visceral portion of the serous membrane (a layer of the heart wall).

Pericardial Fluid and Pericarditis

• Pericardial fluid, is a serous fluid, decreases friction.

• Pericarditis:

  • Inflammation of the pericardium.

  • Leads to swollen surfaces rubbing against each other.

  • Can lead to Cardiac Tamponade.

  • Restricted movement of the heart because of fluid accumulation.

  • Inability of ventricles to expand properly.

  • Reduced blood pumping.

  • Less blood going to tissues.

  • Caused by injuries to pericardium or chest wall, or acute pericarditis.

Coronary Circulation Overview

• Coronary arteries deliver nutrients to the cardiac tissue.

• Cardiac veins return blood via the coronary sinus to the right atrium.

• The pulmonary trunk has been removed for viewing purposes.

  • We can typically see the inter-ventricular septum through a cut view.

  • Left ventricle delivers blood through the aortic semilunar valve into the aorta.

Coronary Blood Flow

• Coronary arteries branch off aorta early, ensuring heart gets blood first.

• Anterior view: Right coronary artery goes to the right side and posterior surface; left coronary artery branches off into circumflex artery and anterior interventricular artery aka left anterior descending artery (LAD).

• Little bit of backflow of blood occurs when ventricles relax shooting into coronary arteries, so heart gets its share first.

Chart of Blood Vessels

• Circulatory System

• Aorta branches:

  • Right Coronary Artery

  • Right Marginal Artery

  • Posterior Intraventricular Artery

  • Left Coronary Artery

  • Circumflex Artery

  • Anterior Inter-ventricular Artery (LAD)

Vein Routes

• Riding alongside the anterior inter-ventricular artery:

  • Great Cardiac Vein, directs blood back to coronary sinus that gets blood back into right atrium

• Posterior side:

  • Middle Cardiac Vein runs right alongside your posterior interventricular artery, delivers back to Coronary Sinus

• Multiple Small Cardiac Veins

  • Delivering blood directly to right atrium, some emptying into the coronary sinus

Mini-Practical in Lab

• Posterior side is flatter compared to the dipped and more deeply sulcus'd anterior surface

Standard Blood Flow Circuit

• Review: Oxygen-poor blood moves into the right atrium, through the tricuspid valve to the right ventricle, passes the pulmonary semilunar valve to the main pulmonary trunk, it splits, gets de-oxygenated and carbon dioxide-rid in the pulmonary capillaries.

• Red blood cells live approximately 120 days.

• Right side and left side circuits happen simultaneously. If not, it is typically edema that may occur.

Key Structures

• Fibrous Pericardium (via the diaphragm), Trabecular Carinae, Interventricular Septum (wall between ventricles).

• Epicardium is your visceral serous pericardium, the myocardium comes next, then the inner-chamber-lining endocardium.

Differences in ventricles

• Pumping blood from the left ventricle is further than pumping blood from the right ventricle.

• The blood of the left ventricle goes away further than when pumping of the right ventricle.

• Right Ventricle: Pulmonary

• Left Ventricle: Vessels of systemic circulation

• Thicker Ventricular wall gives more circular opening for the right ventricular wall (vs like a cresecent-moon).

Pressure Volume Review

• Cardiac & Chamber contraction yields greater inner chamber pressure & potential decrease in chamber size.

• Ventricular chamber dilation yields ventricular relaxation.

• Greater Ventricular relaxation = larger potential chamber size.

Blood Paths & Valves

• During Ventricular relaxation:

  • The semilunar valves remain closed.

  • The AV valves remain open.

• Once in Ventricular diastole:

  • The semilunar valves are closed.

  • The AV valves are open.

  • The Ventricles are dilated and stretched, filling up readily with blood.

Cardiac Skeleton Insulation

• A fibrous connective tissue present between the valves of the atria as well as between the semilunar valves. It serves to electrically insulate the atria from the ventricles.

Artery Flow Blockage

• Coronary Artery Disease (CAD) is complete or partial artery blockage yielding eventual lack of muscle tissue perfusion, ultimately producing Coronary Ischemia.

Atherosclerosis Disease

• Atherosclerosis disease is hardened artery walls caused by fatty plaque building, eventually reducing flow, causing an Embolus. Necrosis is the eventual tissue death, producing Infarct. Repair possible through stenting.

Cardiac Cycle Rhythm

• Contraction-is-Systole, and Relaxation-is-Diastole

• Systolic pressure occurs when chambers are contracting (higher reading), where Diastolic pressure occurs during resting as chambers are filling (lower reading when two-number-measurement noted).

Conduction and Action Potentials

• The signal to transmit electrical impulses:

  • The Conduction System: Made of PaceMaker & Conducting Cells

  • The Contractile Cells: Specialized areas that directly relate action potential to heart activity

• Pacemaker- & Conducting-Cells release unstable resting membrane potentials:

  • Slowly Depolarizing

  • First node the SA Node ( sinoatrial node ), followed eventually by the AV Node ( atrioventricular node ), with the SA Node setting initial pace (where undamaged).

Auto Rhythmicity and The Heart

• Auto Rhythmicity yields AutoMaticity

• Pacemaker Cells independently reach threshold - without an outside stimulus, whether nervous nor endocrine system initiated. So, action-potential still occurs for contractile cell contraction.

• ANS and endocrine system have ultimate influence on pace settings.

• Normal resting-Heart-Rate is slower than SA-Node due to Parasympathetic Division influence.

SA Node Paths & Pathways

• SA Node ( sinoatrial node ): Embedded in the posterior wall of the right atrium, releases SA electrical impulse that is distributed throughout the pathways.

  • Internodal Pathways connect between the nodes.

• SA Node: Pace typically and normally set by SA-node, sending signals via internodal pathways to the AV-Node, and throughout atrial walls.

• AV Node: Between the junction between the atria and ventricles.

  • At a slower individual pacing, however it maintains rate potential given a damaged SA Node.

• From the AV-Node, the signal sent along conducting pathway along the AV-Bundle & inter-ventricular septum to bundle branches.

• Inter-ventricular Septum location curves around outside ventricular walls to end at purkinje fibers, triggering ventricular contraction.

Conduction System Breakdown

• SA Node: Releases Node impulses on posterior side of the Right Atrium

• Internodal Pathways direct signal down to AV Node

• AV Node with delay allowing atrial contraction time/completion.

• Down along the Inter-ventricular Septum with the A-V bundle and bundle branches

• Inter Ventricular Septum location curves around outside ventricular walls to end: Purkinje Fibers.

The EKG & ECG

• Abnormal rhythm detection and nodal functionality is determined with electrocardiograms, a measurement to check performance activity of heart components.

• Millivolts on the y-axis determine electrical potential. As the scale on ECG increases, it's approaching positivity (depolarization).

• P Wave: Atrial Depolarization, which leads into Atrial Systole.

• QRS Complex: Ventricular Depolarization, leading to Ventricular Systole. Masks eventual Late Atrial Repolarization.

• T Wave: Ventricular Repolarization.
  Note: Depolarization yields movement. Repolarization readies & sets potential.
  In between ECGs is potential drifting.

Cardiac Arrhythmias Abnormalities

• This rhythm is abnormal and, an abnormality example that can be traced.

• Atrial Fibrillation: Atrial contraction abnormal through high impulses (Example 500 beats per min). The atria eventually quiver as normal functions break-down

• Single PVC: Rare abnormality is not dangerous, but frequent occurrences due to certain drugs can be life-threatening.

• An ectopic pacemaker from stimulants produce contractions before original SA Nodes release, stimulating PVC.

Action Potentials & Contraction Cells

• Electrical Activity versus Wall Behavior in Atrial and Ventricular Activities

• Action Potential precedes Plateau, followed with Cardiac Contractile Cell Relaxation potential, before ever achieving Repolarization. Thus, Heart cannot achieve full tentany, due to said necessary functions breaking-down during the chain.

• 3 muscle tissue stages: Rapid Repolarization, Plateau, Then Repolarization.

• Rapid Depolarization: Release fast SODIUM Ion Channels for sudden rush, then slow Calcium Channels to open as sodium gates close. Calcium ion entry is delayed as the rapid-sodium-ion channel closes. Once enough charge builds-up the potassium channels come to bare.

• Three stages of Action Potential:

  • Depolarization:

  • opening of fast voltage-gated sodium ion channels

  • Na+ influx gets electrical balance back/level

  • fast sodium channels close

  • Plateau:

  • Ca++ voltage-gated channel opens slowly/calcium channels open

  • Ca++ influx delays repolarization

  • Potassium gates open slowly

  • Repolarization:

  • Ca++ Channels close, Potassium channels open

  • K (potassium) rushes out to achieve resting state.

Relaxation & Ion Recap

• Electrical Activity yields action potential for muscle movement