1. Cardiac Muscle Found only in heart Striated
Each cell usually has one nucleus
Has intercalated disks and gap junctions
Autorhythmic cells
Action potentials of longer duration and longer refractory period
Ca2+ regulates contraction

2. Cardiac Muscle
Elongated, branching cells containing 1-2 centrally located nuclei
Contains actin and myosin myofilaments
Intercalated disks: Specialized cell-cell contacts
Desmosomes hold cells together and gap junctions allow action potentials
Electrically, cardiac muscle behaves as single unit

4. Cardiac myocyte action potential:

5. Refractory Period
Absolute: Cardiac muscle cell completely insensitive to further stimulation
Relative: Cell exhibits reduced sensitivity to additional stimulation
Long refractory period prevents tetanic contractions

6. AP-contraction relationship:
AP in skeletal muscle is very short-lived
AP is basically over before an increase in muscle tension can be measured.
AP in cardiac muscle is very long-lived
AP has an extra component, which extends the duration.
The contraction is almost over before the action potential has finished.

7. Functions of the Heart Generating blood pressure Routing blood
Heart separates pulmonary and systemic circulations
Ensuring one-way blood flow
Heart valves ensure one-way flow
Regulating blood supply
Changes in contraction rate and force match blood delivery to changing metabolic needs

9. Orientation of cardiac muscle fibres:
Unlike skeletal muscles, cardiac muscles have to contract in more than one direction.
Cardiac muscle cells are striated, meaning they will only contract along their long axis.
In order to get contraction in two axis, the fibres wrap around.

10. Circulation circuits:

14. Heart Wall Three layers of tissue
Epicardium: This serous membrane of smooth outer surface of heart
Myocardium: Middle layer composed of cardiac muscle cell and responsibility for heart contracting
Endocardium: Smooth inner surface of heart chambers

19. Valve function:

22. Coronary circulation:

23. Cardiac conducting system:

24. Pacemaker potential:

27. EKG:

28. Heart sounds:

29. Heart Sounds First heart sound or “lubb” Second heart sound or “dupp”
Atrioventricular valves and surrounding fluid vibrations as valves close at beginning of ventricular systole
Second heart sound or “dupp”
Results from closure of aortic and pulmonary semilunar valves at beginning of ventricular diastole, lasts longer
Third heart sound (occasional)
Caused by turbulent blood flow into ventricles and detected near end of first one-third of diastole

30. Cardiac Arrhythmias Tachycardia: Heart rate in excess of 100bpm
Bradycardia: Heart rate less than 60 bpm
Sinus arrhythmia: Heart rate varies 5% during respiratory cycle and up to 30% during deep respiration
Premature atrial contractions: Occasional shortened intervals between one contraction and succeeding, frequently occurs in healthy people

31. Cardiac Cycle
Heart is two pumps that work together, right and left half
Repetitive contraction (systole) and relaxation (diastole) of heart chambers
Blood moves through circulatory system from areas of higher to lower pressure.
Contraction of heart produces the pressure

34. Pressure relationships:

35. Mean Arterial Pressure (MAP)
Average blood pressure in aorta
MAP=CO x PR
CO is amount of blood pumped by heart per minute
CO=SV x HR
SV: Stroke volume of blood pumped during each heart beat
HR: Heart rate or number of times heart beats per minute
Cardiac reserve: Difference between CO at rest and maximum CO
PR is total resistance against which blood must be pumped

36. Factors Affecting MAP

37. Regulation of the Heart
Intrinsic regulation: Results from normal functional characteristics, not on neural or hormonal regulation
Starling’s law of the heart
Extrinsic regulation: Involves neural and hormonal control
Parasympathetic stimulation
Supplied by vagus nerve, decreases heart rate, acetylcholine secreted
Sympathetic stimulation
Supplied by cardiac nerves, increases heart rate and force of contraction, epinephrine and norepinephrine released

38. Heart Homeostasis Effect of blood pressure
Baroreceptors monitor blood pressure
Effect of pH, carbon dioxide, oxygen
Chemoreceptors monitor
Effect of extracellular ion concentration
Increase or decrease in extracellular K+ decreases heart rate
Effect of body temperature
Heart rate increases when body temperature increases, heart rate decreases when body temperature decreases

39. Baroreceptor and Chemoreceptor Reflexes

42. Cardian innervation:

43. Pacemaker regulation:
Once the pacemaker cells reach threshold, the magnitude and duration of the AP is always the same.
In order to change the frequency, the time between APs must vary.
The interval can only be changed in two ways.
The rate of depolarization can be changed
The amount of depolarization required to reach threshold can be changed.

45. Vascular physiology:

46. Peripheral Circulatory System
Systemic vessels
Transport blood through most all body parts from left ventricle and back to right atrium
Pulmonary vessels
Transport blood from right ventricle through lungs and back to left atrium
Blood vessels and heart regulated to ensure blood pressure is high enough for blood flow to meet metabolic needs of tissues

47. Blood Vessel Structure
Arteries
Elastic, muscular, arterioles
Capillaries
Blood flows from arterioles to capillaries
Most of exchange between blood and interstitial spaces occurs across the walls
Blood flows from capillaries to venous system
Veins
Venules, small veins, medium or large veins

48. Structure of Arteries and Veins
Three layers except for capillaries and venules
Tunica intima (interna)
Endothelium
Tunica media
Vasoconstriction
Vasodilation
Tunica adventitia (externa)
Merges with connective tissue surrounding blood vessels
Note mistake on figure

49. Structure of Arteries Elastic or conducting arteries
Largest diameters, pressure high and fluctuates
Muscular or medium arteries
Smooth muscle allows vessels to regulate blood supply by constricting or dilating
Arterioles
Transport blood from small arteries to capillaries

50. Structure of Veins Venules and small veins Medium and large veins
Tubes of endothelium on delicate basement membrane
Medium and large veins
Valves
Allow blood to flow toward heart but not in opposite direction
Atriovenous anastomoses
Allow blood to flow from arterioles to small veins without passing through capillaries

51. Blood Vessel Comparison:

55. Capillaries: Capillary wall consists mostly of endothelial cells
Types classified by diameter/permeability
Continuous
Do not have fenestrae
Fenestrated
Have pores
Sinusoidal
Large diameter with large fenestrae

56. Capillary Network:
Blood flows from arterioles through metarterioles, then through capillary network
Venules drain network
Smooth muscle in arterioles, metarterioles, precapillary sphincters regulates blood flow

57. Muscular contractions aid venous return:

58. Pulmonary Circulation
Moves blood to and from the lungs
Pulmonary trunk
Arises from right ventricle
Pulmonary arteries
Branches of pulmonary trunk which project to lungs
Pulmonary veins
Exit each lung and enter left atrium

59. Systemic Circulation: Arteries
Aorta
From which all arteries are derived either directly or indirectly
Parts
Ascending, descending, thoracic, abdominal
Coronary arteries
Supply the heart

60. Systemic Circulation: Veins
Return blood from body to right atrium
Major veins
Coronary sinus (heart)
Superior vena cava (head, neck, thorax, upper limbs)
Inferior vena cava (abdomen, pelvis, lower limbs)
Types of veins
Superficial, deep, sinuses

61. Dynamics of Blood Circulation
Interrelationships between
Pressure
Flow
Resistance
Control mechanisms that regulate blood pressure
Blood flow through vessels

63. Blood Pressure Measure of force exerted by blood against the wall
Blood moves through vessels because of blood pressure
Measured by listening for Korotkoff sounds produced by turbulent flow in arteries as pressure released from blood pressure cuff

64. Pressure and Resistance
Blood pressure averages 100 mm Hg in aorta and drops to 0 mm Hg in the right atrium
Greatest drop in pressure occurs in arterioles which regulate blood flow through tissues
No large fluctuations in capillaries and veins

65. Blood Pressure Measurement

66. Pulse Pressure Difference between systolic and diastolic pressures
Increases when stroke volume increases or vascular compliance decreases
Pulse pressure can be used to take a pulse to determine heart rate and rhythmicity

67. Blood Flow, Poiseuille’s Law and Viscosity
Amount of blood moving through a vessel in a given time period
Directly proportional to pressure differences, inversely proportional to resistance
Poiseuille’s Law
Flow decreases when resistance increases
Flow resistance decreases when vessel diameter increases
Viscosity
Measure of resistance of liquid to flow
As viscosity increases, pressure required to flow increases

68. Critical Closing Pressure, Laplace’s Law and Compliance
Vascular compliance
Tendency for blood vessel volume to increase as blood pressure increases
More easily the vessel wall stretches, the greater its compliance
Venous system has a large compliance and acts as a blood reservoir
Critical closing pressure
Pressure at which a blood vessel collapses and blood flow stops
Laplace’s Law
Force acting on blood vessel wall is proportional to diameter of the vessel times blood pressure

69. Physiology of Systemic Circulation
Determined by
Anatomy of circulatory system
Dynamics of blood flow
Regulatory mechanisms that control heart and blood vessels
Blood volume
Most in the veins
Smaller volumes in arteries and capillaries

71. Cross-Sectional Area
As diameter of vessels decreases, the total cross-sectional area increases and velocity of blood flow decreases
Much like a stream that flows rapidly through a narrow gorge but flows slowly through a broad plane

72. Laminar and Turbulent Flow
Laminar flow
Streamlined
Outermost layer moving slowest and center moving fastest
Turbulent flow
Interrupted
Rate of flow exceeds critical velocity
Fluid passes a constriction, sharp turn, rough surface

73. Aging of the Arteries Arteriosclerosis Atherosclerosis
General term for degeneration changes in arteries making them less elastic
Atherosclerosis
Deposition of plaque on walls

76. Capillary Exchange and Interstitial Fluid Volume Regulation
Blood pressure, capillary permeability, and osmosis affect movement of fluid from capillaries
A net movement of fluid occurs from blood into tissues. Fluid gained by tissues is removed by lymphatic system.

77. Fluid Exchange Across Capillary Walls

78. Vein Characteristics and Effect of Gravity on Blood Pressure
Venous return to heart increases due to increase in blood volume, venous tone, and arteriole dilation
Effect of Gravity
In a standing position, hydrostatic pressure caused by gravity increases blood pressure below the heart and decreases pressure above the heart

79. Control of Blood Flow by Tissues
Local control
In most tissues, blood flow is proportional to metabolic needs of tissues
Nervous System
Responsible for routing blood flow and maintaining blood pressure
Hormonal Control
Sympathetic action potentials stimulate epinephrine and norepinephrine

80. Local Control of Blood Flow by Tissues
Blood flow can increase 7-8 times as a result of vasodilation of metarterioles and precapillary sphincters in response to increased rate of metabolism
Vasodilator substances produced as metabolism increases
Vasomotion is periodic contraction and relaxation of precapillary sphincters

81. Nervous Regulation of Blood Vessels

82. Short-Term Regulation of Blood Pressure
Baroreceptor reflexes
Change peripheral resistance, heart rate, and stroke volume in response to changes in blood pressure
Chemoreceptor reflexes
Sensory receptors sensitive to oxygen, carbon dioxide, and pH levels of blood
Central nervous system ischemic response
Results from high carbon dioxide or low pH levels in medulla and increases peripheral resistance

83. Baroreceptor Reflex Control

85. Local mechanisms affect MAP:

86. Effects of pH and Gases

87. Long-Term Regulation of Blood Pressure
Renin-angiotensin-aldosterone mechanism
Vasopressin (ADH) mechanism
Atrial natriuretic mechanism
Fluid shift mechanism
Stress-relaxation response

88. General control of MAP:

89. Renin-Angiotensin-Aldosterone Mechanism

90. Vasopressin (ADH) Mechanism

91. Long Term Mechanisms Which Lower Blood Volume
Fluid shift
Movement of fluid from interstitial spaces into capillaries in response to decrease in blood pressure to maintain blood volume
Stress-relaxation
Adjustment of blood vessel smooth muscle to respond to change in blood volume
Atrial natriuretic factor
Hormone released from cardiac muscle cells when atrial blood pressure increases, simulating an increase in urinary production, causing a decrease in blood volume and blood pressure

92. Chemoreceptor Reflex Control

94. Shock Inadequate blood flow throughout body Three stages
Compensated: Blood pressure decreases only a moderate amount and mechanisms able to reestablish normal blood pressure and flow
Progressive: Compensatory mechanisms inadequate and positive feedback cycle develops; cycle proceeds to next stage or medical treatment reestablishes adequate blood flow to tissues
Irreversible: Leads to death, regardless of medical treatment

95. Fetal circulation: