Cardio-vascular system. Outline 1- Overview 2- Path of blood through the heart and vasculature 3-...
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Cardio-vascular system
Outline
• 1- Overview
• 2- Path of blood through the heart and vasculature
• 3- Anatomy of the heart
• 4- Electrical activity of the heart
• 5- The cardiac cycle
• 6- Cardiac output and its control
Outline
• 1- Overview
• 2- Path of blood through the heart and vasculature
• 3- Anatomy of the heart
• 4- Electrical activity of the heart
• 5- The cardiac cycle
• 6- Cardiac output and its control
Overview
• Roles:
- Pumps blood throughout the body vasculature
- Endocrine function • Components
- Heart
- Blood vessels
- Blood
Outline
• 1- Overview
• 2- Path of blood through the heart and vasculature
• 3- Anatomy of the heart
• 4- Electrical activity of the heart
• 5- The cardiac cycle
• 6- Cardiac output and its control
Figure 13.3
Circulation
• Parallel flow of blood to various organs
-- allows for fully oxygenated blood to reach each organ
-- allows for independent regulation
• Exception: portal circulation (1 capillary bed to another)
-- hypothalamus-pituitary gland portal system
-- hepatic portal system
Applications• What is the consequence of the blood clot (a thrombus) located in
the right saphenous vein becoming loose ( an embolus)?
• What is the consequence of the blood clot (a thrombus) located in the right atrium becoming loose ( an embolus)?
• What is the consequence of the blood clot (a thrombus) located in the left atrium becoming loose ( an embolus)?
• What is the consequence of the blood clot (a thrombus) located in the left saphenous vein becoming loose ( an embolus)?
• What is the consequence of the blood clot (a thrombus) located in the right femoral artery becoming loose ( an embolus)?
The heart
• Located in mediastinum• Surrounded by the pericardium
- outer fibrous pericardium - inner serous pericardium: - parietal pericardium - visceral pericardium - in between: pericardial cavity small amount of
pericardial fluid (prevent friction)
Application: cardiac tamponade
Outline
• 1- Overview
• 2- Path of blood through the heart and vasculature
• 3- Anatomy of the heart
• 4- Electrical activity of the heart
• 5- The cardiac cycle
• 6- Cardiac output and its control
Figure 13.1
The heart: review
Figure 13.6
Blood flow in the heart
Figure 13.4
Coronary circulation
• What is angina?
• What is a myocardial infarction?
Outline
• 1- Overview
• 2- Path of blood through the heart and vasculature
• 3- Anatomy of the heart
• 4- Electrical activity of the heart
• 5- The cardiac cycle
• 6- Cardiac output and its control
Figure 13.10
Conduction system of the heart
• Two types of fibers:
- contractile fibers (cardiac muscle fibers)
- self-depolarizing fibers in the sino-atrial (S/A) node (pace-maker fibers autorhythmicity)
Electrocardiogram
• Recording of the electrical activity of the heart by electrodes applied on the skin
• ECG wave patterns vary with the location of the electrodes
ECG• P wave: S/A node is firing • P-Q interval: time it takes for the
electrical impulse to travel from the S/A node to the atrio/ventricular (A/V) node
• QRS wave: the electrical impulses spread through the bundle of His, bundle branches and Purkinje fibers in the ventricles
• T wave: ventricular repolarization• Q-T interval: corresponds to
ventricular contraction (=systole)• T-Q interval: ventricular diastole• R-R interval: time between
heartbeats
Other properties of the conduction system
• S/A node: 60-100 beats/min (sinus rhythm = normal rhythm)
• If S/A node is non functional: the A/V node takes over 40-60 beats/min
• If both S/A and A/V nodes are shot, ventricular electrical activity takes over > 40 beats/min
Applications
• What is atrial fibrillation?• “ “ ventricular fibrillation?
• What is the difference between tetanus and fibrillation?
• Atrial and ventricular fibrillations: consequences from each type of abnormal rhythms
Outline
• 1- Overview
• 2- Path of blood through the heart and vasculature
• 3- Anatomy of the heart
• 4- Electrical activity of the heart
• 5- The cardiac cycle
• 6- Cardiac output and its control
Figure 13.18
Cardiac cycle
Cardiac cycle• Systole: contraction of heart
chambers but mostly ventricles• Diastole: ventricular relaxation
(atria have a minimal effects) • Ventricular filling: during diastole,
P wave • Ventricular contraction: at first,
semi-lunar valves are closed blood cannot flow out and pressure increase in ventricle isovolumetric contraction
• Ventricular ejection: The pressure against the valves is strong enough to open them the blood flows out
• When the ventricles stop contracting, the pressure falls isovolumetric relaxation pressure falls even more semi-lunar valves close and A/V valves open
Cardiac cycle
• End-diastolic volume = EDV = volume of blood present at the end of diastole in the ventricles
• End-systolic volume = ESV = volume of blood present at the end of systole
• Stroke volume = SV: amount of blood ejected by the ventricles = EDV-ESV
• Ejection fraction = EF = SV/EDV
• Note: EF gives a measure of cardiac muscle efficiency
• What can cause a low ejection fraction?
• What are the consequences of a low ejection fraction?
Outline
• 1- Overview
• 2- Path of blood through the heart and vasculature
• 3- Anatomy of the heart
• 4- Electrical activity of the heart
• 5- The cardiac cycle
• 6- Cardiac output and its control
Cardiac output = CO• Cardiac output = volume of blood pumped out by the
heart per minute
• CO = SV x HR (CO must adapt to body needs)
• Control of CO: ** control of SV:
- Intrinsic control - Extrinsic control
** control of HR: - Extrinsic control
-- Autonomic input-- Hormonal control
Control of the stroke volume
• SV: a function of- 1. Ventricular contractility: a
function ventricular health and stretch
- 2. EDV: ventricular refill is a function of the blood pressure in the central veins (central venous pressure) end- diastolic pressure = preload
- 3. ESV: a function of afterload = pressure against blood flow out of the heart – determined by aortic blood pressure
Cardiac output = CO• Cardiac output = volume of blood pumped out by the
heart per minute
• CO = SV x HR (CO must adapt to body needs)
• Control of CO: ** control of SV:
- Intrinsic control - Extrinsic control
** control of HR: - Extrinsic control
-- Autonomic input-- Hormonal control
Control of the stroke volume
• Intrinsic control
- Starling law of the heart: The heart automatically adjust its output to match its input
- Property of the cardiac muscle: the more it is stretched, the stronger it contracts (up to a limit)
(in other word, what ever comes in, goes out)
What would happen if this law is not respected?
Control of the stroke volume
• Extrinsic control- Neural control: -- the sympathetic NS has
axonal extension over the entire ventricles β receptors binding to NE stronger contraction
-- no parasympathetic axonal extension no direct action on ventricular wall
- Hormonal control -- Epinephrine from adrenal
medulla has the same effect as NE from sympathetic nerve endings increased force of contraction
Cardiac output = CO• Cardiac output = volume of blood pumped out by the
heart per minute
• CO = SV x HR (CO must adapt to body needs)
• Control of CO: ** control of SV:
- Intrinsic control - Extrinsic control
** control of HR: - Extrinsic control
-- Autonomic input-- Hormonal control
Control of heart rate (HR)
• S/A node fires automatically 60-100/times per minute. Its activity is modulated by the following factors:
• Extrinsic control only -- Autonomic NS * action on the S/A node
mainly * NE increases HR * Ach decreases HR
-- Hormonal control * Epinephrine from the adrenal
gland increases HR
-- drugs and ions (K+, Ca++, digoxin and others)
Factors influencing HR• The cardiac center in the
medulla oblongata controls the HR (or S/A node).
• It receives information from the body through various receptors
• Aortic and carotid bodies monitor blood O2 and send the info. to the cardiac center (↓O2↑HR)
• CO2 and pH receptors in the hypothalamus also send info. to the cardiac center (under normal conditions, they have more influence on HR then O2 receptors (↑CO2 or ↓pH ↑HR)
• Body temperature (↑Temp ↑HR)
Applications• Jimmy has an abnormal HR at 144b/min. He has been admitted
and is on medication so his HR reverts to a sinus rhythm (when the S/A node is in control). The next day, his HR is unchanged.
• Roger also has an abnormal HR at 131b/min. He has been admitted and is on medication so his HR reverts to a sinus rhythm (when the S/A node is in control). The next day, his HR is unchanged.
• Marian has been admitted during the night. She has a sinus rhythm (driven by S/A node) at 125 b/min.
• Carlie has an abnormal HR at 55 b/min. He has been admitted and is on medication so his HR reverts to a sinus rhythm (when the S/A node is in control). The next day, his HR is unchanged.
• Which of these 4 patients would you go see first? Why?
• Hint: how is the HR regulated?
Applications
• Jimmy has been on medication for an abnormal HR at 144 b/min. On a cardiac monitor, you see his heart rate jumping to 190 b/min. Which consequences do you expect?