The Circulatory System: The Heart

Main function of the heart.

Provide pressure for movement of blood through blood vessels by alternatively contracting (systole) and relaxing (diastole)

Location of the heart

-Within the pericardial cavity in Mediastinum of the thoracic cavity

-directly posterior to the sternum, 2/3 lies left of midline

Coverings of heart

1. Fibrous pericardium: Outermost layer of pericardial sac

2. Serous Pericardium: Parietal layer (outer) and visceral layer (stuck to organ) that surround liquid cavity.

3. Pericardial Cavity: fluid-filled cavity between the pericardial layers

-decreases friction during heart movement

-Very Small

Layers of the heart wall

1. Epicardium: Visceral pericardium

-serous membrane

-most superficial layer

2. Myocardium: Middle layer of cardiac muscle

-muscles arranged in spiral or circular bundles

-fibrous skeleton supports and anchors cardiac muscle

3. Endocardium: deepest layer

-simple squamous epithelium

-one row of flat cells

Base and Apex

Base: Top of Heart

-where blood vessels are

Apex: Bottom of heart

-formed by left ventricle

Heart Chambers

1. Right Atrium

2. Right Ventricle

3. Left Atrium

4. Left Ventricle

Right Atrium

-Receives blood from Vena Cava (vein)

-Pumps blood the to right ventricle -Preloads Right Ventricle

Left Atrium

-Receives blood from Pulmonary Veins

-Pumps blood to Left Ventricle

-Preloads Left Ventricle

-Passively fills with blood returning from the lungs

Right Ventricle

-Pumps blood to Pulmonary Trunk -Dysfunction of this chamber causes Systemic Edema

Left Ventricle

-Pumps Blood to Aorta

-Dysfunction of this chamber leads to Pulmonary Edema

-The strongest chamber

-Greatest contributor to systemic BP

Chamber Walls

Coronary sulcus: Atrioventricular groove

that separates the atria above from the ventricles below.

Interatrial Septum: Wall between Atria

Interventricular septum:

Cardiac Ridges

Pectinate muscles: internal ridges on the Right Atrium

Tendinae cordae: internal ridges on both Ventricles

Great Vessels of the Heart

Vessels: conduits for blood movement

-Arteries: Pulmonary Artery and Aorta, carry blood away from heart

-Veins: Pulmonary Vein, Vena Cava, and Coronary Sinus, carry blood to heart

Pulmonary Artery

caries deoxygenated blood away from heart to lungs (Pulmonary Circuit)

Aorta

carries oxygenated blood away from heart to rest of body (Systemic Circuit)

auricles

expanded areas of atria that can fill with blood from vena cava

Superior and Inferior Vena Cava

-Major Vein of Heart

-Largest vein in body

-carries deoxygenated blood from body to heart

Pulmonary Veins

carry oxygenated blood from lungs to heart

Fossa Ovalis

-remant of foramen ovale

-circle that encloses when born

-leaves only a dent

Heart Valves

Atriventricular valves: allow blood to flow from atria to ventricles when latter relaxing; prevent backflow from ventricles to atria when they contract

1.Tricuspid Valve: Right AV valve

btwn Right Atria and Ventricle

2.Bicuspid (mitral) Valve: Left AV

valve btwb Left Atria and Ventricle

Semilunar valves: allow blood to flow from ventricles to arteries when ventricles contract

3.Pulmonary Semilunar valve: Right

valve btwn Right Ventricle and

Pulmonary Artery

4.Aortic Semilunar Valve: Left Valve

btwn Left Ventricle and Aorta

papillary muscles

Responsible for pulling the atrioventricular valves closed by means of the chordae tendineae,

-small bunches of cardiac muscle.

Tendinous cords

Tighten to prevent AV from turning inside out

-prevent back flow

Flow of Blood through Valves - Pressure Gradient

1. Atrial Pressure rises above Ventricular Pressure, Atrium is in systole so AV valve opens.

2. Ventricular pressure rises above Atrial pressure, Atrium is in Diastole so papillary muscles pull and tighten tendinous cords to close AV valve, preventing backflow

3. Ventricular pressure rises above arterial pressure, Ventricles are in Systole so SL valves open

4. Ventricular pressure drops bellow arterial pressure, Ventricles are in Diastole so SL Valves close

Flow of Blood in Pulmonary and Systemic Circuits

1. Superior Vena Cava

2. Right Atrium

3. Tricuspid Valve

4. Right Ventricle

Pulmonary Circuit - to and from capillary beds associated with alveoli of Lungs where gas exchange of blood takes place

5. Pulmonary valve

6. Pulmonary Trunk

7. Pulmonary Artery

8. Lungs

9. Pulmonary Vein

10. Left Atrium

11. Bicuspid (Mitral) Valve

12. Left Ventricle

Systemic Circuit- to and from capillary beds of the rest of the body - gas exchange btwn blood and tissues

13. Aortic Valve

14. Ascending Aorta

15. Coronary arteries

16. Left subclavian artery

17. Systemic capillaries

Types of Cardiac Muscle Cells (Cardiocytes)

1. Autrorhythmic :

-Spontaneously Repolarize

-SA node, AV node, AV bundle,

Purkinje Fibers

2. Contractile:

-Action Potential leads to contraction

-responsible for altering contraction

and relaxation that creates BP

-Ventricle and Atria

Cardiac muscle v. Skeletal muscle

Skeletal muscle

-applies to motor units

-only contracts in response to stimulation by neuron neurotransmitter ACh

Cardiac Muscle

-applies to entire organ

-certain cells are self-excitatory, depolarize spontaneously (Autorhythmic)

-Also autonomic stimulation (Parasympathetic and Sympathetic NS)

Purkinje Fibers

distribute(s) the electrical excitation to the cardiocytes of the ventricles.

Atrioventricular (AV) Node

-Located near the right AV valve at the lower end of the interatrial septum

-Acts as an electrical gateway to the ventricles.

Atrioventricular (AV) Bundle

-a pathway

-signals leave the AV node

-enter the interventricular septum -descend toward the apex.

Sinoatrial (SA) Node

-A patch of modified cardiocytes in the right atrium

-the pacemaker that initiates each heartbeat and determines the heart rate.

Heart's intrinsic conduction system.

1. SA node fires

2. Excitation spreads through Atrial myocardium

3. AV node fires

4. Excitation spreads down AV Bundle

5. Purkinje Fibers distribute excitation through Ventricular myocardium

Coronary circulation: Arteries

The arteries of the heart wall

-left coronary artery (LCA) divides into

-anterior interventricular branch

-circumflex branch gives off a

-left marginal branch

-Right coronary artery (RCA) divides into

-right marginal branch

-posterior interventricular branch

Coronary Circulation: Veins

The veins of the heart wall

-Great Cardiac Vein

-Posterior interventricular (middle cardiac) vein

-Left marginal vein

-Coronary Sinus

Occlusion

Common coronary circulation disorder

-clogging/blockage of an artery

-tissue downstream is deprived of nutrients

-may cause Ischemia

Ischemia

Common coronary circulation disorder

-inadequate blood supply to organ or part of body

-leads to changes in cell structure or function

-can be caused by Occlusion and may cause Infarction

Infarction

Common coronary circulation disorder

-Area of dead tissue (necrotic)

-leads to disruption of arterial circulation

-can be caused by Ischemia

The Nervous System and Heart Beat.

Explain the relationship between

Preload

The precontraction pressure in the heart as the volume of blood builds up.

-Volume Ventricles must eject

afterload

resistance ventricles contract against

Diastole

Relaxation of Heart (Repolarization)

Systole

Contraction of Heart (Depolarization)

Depolarization

Chamber is about to contract (Systole)

-related to P-wave and QRS complex

Repolarization

Chamber goes back to relaxation (Diastole)

-Related to T-wave

The principal deflections that are observed in a normal ECG

and explain what is happening in the heart during each of these events

"electrocardiogram" (ECG).

-pattern of electrical activity recorded at the body surface

-Composed of P- and T-wave and QRS complex

QRS Complex

Ventrical Depolarization (Ventricles go into systome- they are about to contract)

T-wave

ventricle repolarization

P-wave

Atrial Depolarization (atria go into systole- they are about to contract)

cardiac cycle

and be able to discuss sequential and concurrent changes in blood pressure (atria, ventricles, aorta), blood volume (ventricles), heart sounds, the ECG and mechanical events. You should study and be able to reproduce Figure 19.20.

Ventricular Filling

Isovolumetric Contraction

Ventricular Ejection

Isovolumetric Relaxation

"cardiac output".

CO = HR X SV.

you can see that there are only two ways to change it: change the heart rate or change the stroke volume.

Stroke Volume

The amount of blood ejected from the heart in one contraction.

SV = EDV - ESV.

Factors that influence stroke volume.

Heart Rate

Factors that influence heart rate.

Factors ) that influence Contractility.

How the brain regulates cardiac output.

How cardiac output can vary within and between individuals.

congestive heart failure.

The difference between left and right heart failure.

Explain how you can tell

Place the labels in order denoting the sequence of events of the cardiac cycle beginning with passive ventricular filling.

1. The entire heart exhibits resting

membrane potential

2. Cells of the SA node reach autorhythmic threshold

3. Voltage-regulated, fast-calcium and and sodium channels open in the SA node

4. Cations flow from the SA node to the adjacent cardiocytes through gap junctions

5. The P-wave appears on an EKG

6. AV node depolarization occurs and transmits the signal to the bundle branches

7. The downward deflection (Q) is seen on the EKG tracing

8. End diastolic volume is achieved

9. The AV valves close

10. The semilunar valves open

11. Blood exits the ventricles

12. Voltage-regulated potassium channels open in the myocytes of the ventricles

13. The T-wave appears on the EKG tracing

14. End systolic volume is achieved as the heart enters relaxation