1. Cardiovascular System: The Heart

2. Functions of the cardiovascular System

3. Transports O2, nutrients, CO2, cell wastes, etc. to and from body cells
Maintaining body temperature
Homeostatic relationships with all body systems
With the urinary system, regulation of blood volume and pressure

4. Location of the heart

5. Thoracic cavity between two lungs ~2/3 to left of midline
Surrounded by pericardium:
Fibrous pericardium -
Inelastic; anchors heart in place
Inside is serous pericardium - double layer around heart
Parietal layer fused to fibrous pericardium
Inner visceral layer adheres tightly to heart
Filled with pericardial fluid - reduces friction during beat.

7. Heart anatomy

8. The Heart Wall Epicardium - outer layer Myocardium - cardiac muscle
Two separate networks via gap junctions in intercalated discs - atrial & ventricular
Networks- contract as a unit
Endocardium - Squamous epithelium
lines inside of myocardium

9. The Heart Wall

10. The Heart Wall

11. The Heart Wall

12. Heart Chambers 4 chambers: 2 upper chambers = Atria
Between is inter-atrial septum
Contains fossa ovalis - remnant of foramen ovalis
2 lower chambers = ventricles
Between is interventricular septum
Wall thickness depends on work load
Atria thinnest
Right ventricle pumps to lungs & thinner than left

13. External Anatomy

14. External Anatomy

15. Internal Anatomy

16. Great Vessels of the Heart
Superior & inferior Vena Cavae
Delivers O2 depleted blood to R. atrium from body
Coronary sinus drains heart muscle veins
R. Atrium  R. Ventricle
Pumps through Pulmonary Trunk
R & L Pulmonary Arteries
 lungs

17. Great Vessels of the Heart
Pulmonary Veins from lungs
O2 rich blood
L. atrium Left ventricle
ascending aorta body
Between pulmonary trunk & aortic arch is the ligamentum arteriosum
fetal ductus arteriosum remnant

19. Heart Valves
Designed to prevent back flow in response to pressure changes
Atrio-ventricular (AV) valves are found between the atria and ventricles
Right AV valve = tricuspid valve (has three flaps, or cusps)
Prevent backflow of blood into the right atrium

20. Heart Valves Left AV valve = bicuspid, or mitral valve
Prevents backflow of blood into left atrium
Semilunar Valves are found at the base of aorta and pulmonary trunk
Prevent backflow of blood into the ventricles

21. Heart Valves Chordae Tendinae:
Tiny white cords that anchor the AV valve cusps to the wall of the ventricle
Help to anchor the flaps to prevent a prolapse

24. Coronary Circulation
Blood flow through vessels in myocardium = coronary circulation
Left & right coronary arteries
branch from aorta to carry blood throughout muscle
O2 - depleted blood collected by coronary sinus (posterior)
Empties into right atrium

25. Coronary Circulation

26. Heart physiology

27. Conduction System
1% of cardiac muscle generate action potentials = Pacemaker & Conduction system
Normally begins at sinoatrial (SA) node
Atria & atria contract
AV node – slows the signal, then travels along:
AV bundle (Bundle of His)
bundle branches Purkinje fibers
 apex and up- then ventricles contract

28. Frontal plane
SINOATRIAL (SA) NODE
ATRIOVENTRICULAR
(AV) NODE
Left atrium
Left ventricle
Anterior view of frontal section
ATRIOVENTRICULAR (AV)
BUNDLE (BUNDLE OF HIS)
RIGHT AND LEFT
BUNDLE BRANCHES
PURKINJE FIBERS 1 2 3 4 5
Right atrium
Right ventricle

29. Electrocardiogram
Recording of currents from cardiac conduction on skin = electrocardiogram (EKG or ECG)
P wave = atrial depolarization
Contraction begins right after peak
Repolarization is masked in QRS
QRS complex = Ventricular depolarization
Contraction of ventricle
T-wave = ventricular repolarization
Just after ventricles relax

31. Cardiac Cycle After T-wave ventricular diastole
Ventricular pressure drops below atrial pressure & AV valves open  ventricular filling occurs
After P-wave atrial systole
Finishes filling ventricle (about 25% of total)

32. Cardiac Cycle After QRS ventricular systole
Pressure pushes AV valves closed
Pushes semilunar valves open and ejection occurs
Ejection until ventricle relaxes enough for arterial pressure to close semilunar valves
Cardiac Cycle Animations

33. Cardiac Cycle: Flow Terms
Cardiac Output (CO) = liters/min pumped
Heart Rate (HR) = beats/minute (bpm)
Stroke volume (SV) = volume/beat
CO = HR x SV
Average:

34. Cardiac Cycle: Control of Stroke Volume
Degree of stretch = Frank-Starling law
Increase diastolic volume (stretch) increases strength of contraction increased S.V.
Increased venous return  increased S.V.
Increased sympathetic activity
High back pressure in artery  decreased S.V.
Slows semilunar valve opening
Slow heart rate  increased S.V.

35. Cardiac Cycle: Control of Heart Rate
Pacemaker adjusted by nerves
Cardiovascular Center in Medulla
Parasympathetic - ACh slows HR via Vagus nerve
Sympathetic - norepinephrine speeds HR
Sensory input for control:
Baroreceptors (aortic arch & carotid sinus)- B.P.
Chemoreceptors- O2, CO2, pH

36. Cardiac Cycle: Other Controls
Hormones:
Epinephrine & norepinephrine increase H.R.
Thyroid hormones stimulate H.R.
Called tachycardia (opposite: bradycardia)
Ions
Increased Na+ or K+ decrease H.R. & contraction force
Increased Ca2+ increases H.R. & contraction force

37. Exercise
Aerobic exercise (longer than 20 min) strengthens cardiovascular system
Well trained athlete doubles maximum C.O.
Resting C.O. about the same but resting H.R. decreased

38. Blood vessels and circulation

39. Blood Vessels Arteries: carry blood away from heart Elastic
Muscular: Their smooth muscle helps regulate blood pressure, directs flow
Arterioles: branches of main arteries; distribution to capillaries

40. Blood Vessels Capillaries: thin-walled for diffusion
Veins: carry blood back to heart
Venules: collect blood from capillaries
Veins from tissues  vena cavae  heart

41. Blood Vessel Structure: Arteries, Veins
Three Layers:
Tunica externa: connective tissue
Tunica media: smooth muscle
Tunica interna (intima): endothelial tissue

42. Blood Vessel Structure: Arteries, Veins
Arteries: thicker tunica media
Elastic tissue and/or muscle
Arterioles
Arterioles: control blood pressure, blood flow
Veins
Larger lumen, thinner walls
Contain valves to prevent backflow
Venules
Venules: very thin, no valves

43. Blood Vessel Structure: Arteries, Veins

44. Blood Vessel Functions
Muscular arteries, arterioles regulate flow
Sympathetic activity to smooth muscle  vasoconstriction (narrowing)
Decreased sympathetic activity causes relaxation (dilation)
Arterioles adjust flow into capillaries
Capillaries: sites of gas exchange
Systemic venules and veins serve as blood reservoirs (hold ~64% total blood volume)

45. Venous Return Blood enters veins at very low pressure
Inadequate to overcome gravity and return blood to heart
Skeletal muscle contractions
Contracting skeletal muscles (especially in lower limbs) squeeze veins emptying them
Because of venous valves, flow is  heart

46. Venous Return Respiratory pump has similar action
Inhalation decreases thoracic pressure and increases abdominal pressure  blood to heart
Exhalation allows refilling of abdominal veins

47. Venous Return

48. Blood Flow Through Vessels
Blood flow follows a pressure gradient
Greater gradient  greater flow
BP is highest in aorta: 110/70 mm Hg
BP declines as flows through more vessels
Capillary beds ~35-16 mm Hg
16 mm Hg at venules  0 at right atrium

49. Factors Regulating Blood Flow
Blood volume and ventricular contraction  cardiac output
Vascular resistance: opposition to flow (depends on lumen diameter, vessel length, and blood viscosity)
Smaller lumen (vasoconstriction)  greater resistance
Greater vessel length (with weight gain)  greater resistance
Higher viscosity (as with high hematocrit)  greater resistance

50. Cardiovascular Center
Located in medulla
Helps regulate
Heart rate
Stroke volume
Blood pressure
Blood flow to specific tissues
Mechanisms
By neural mechanisms
By hormonal mechanisms

51. Cardiovascular Center Input
To inform brain that BP should be altered:
Input from different parts of brain
Cerebral cortex: thoughts, decisions
Limbic system: emotions
Hypothalamus: changes in temperature or blood volume
Input from sensory receptors and nerves
Proprioceptors, baroreceptors, chemoreceptors

52. Cardiovascular Center Input
Proprioceptors: monitor movements of joints and muscles
Cause  heart rate as exercise begins   cardiac output (CO)   BP
Baroreceptors in aorta and carotid: if BP 
 sympathetic stimulation   CO   BP
 parasympathetic   CO   BP
Chemoreceptors in aorta and carotid bodies
If low O2, high CO2, or high H+ (acidity)   resistance by  vasoconstriction   BP

53. Cardiovascular Center Input

54. Output Effects ANS nerves to heart Vasomotor (sympathetic nerves)
 Sympathetic  HR and force of contraction   cardiac output (CO)   BP
 Parasympathetic   HR  CO   BP
Vasomotor (sympathetic nerves)
To arterioles contract smooth muscle   vascular resistance   BP
To veins contract smooth muscle  move blood to heart   BP

56. Circulatory Routes
Pulmonary Circulation: from the right side of the heart to the lungs and back to the left side of the heart
Systemic Circulation: from the left side of the heart to the tissues and cells of the body and back to the right side of the heart
Cardiac Circulation: from the left side of the heart through the coronary arteries and back to the right side of the heart

57. Circulatory Routes