Cardio-vascular system

1
Cardio-vascular system
2
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

3
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

4
Overview

• Roles
• - Pumps blood throughout the body vasculature
• - Endocrine function
• Components
• - Heart
• - Blood vessels
• - Blood

5
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

6
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

Figure 13.3
7
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)?

8
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

9
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

10
The heart review
Figure 13.1
11
Blood flow in the heart
Figure 13.6
12
Coronary circulation

• What is angina?
• What is a myocardial infarction?

Figure 13.4
13
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

14
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)

Figure 13.10
15
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

16
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

17
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 ? gt 40 beats/min

18
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

19
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

20
Cardiac cycle
Figure 13.18
21
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

22
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

23

• What can cause a low ejection fraction?
• What are the consequences of a low ejection
  fraction?

24
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

25
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

26
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

27
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

28
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?

29
Control of the stroke volume

• Extrinsic control
• Neural control
• -- the sympathetic NS has axonal extension
  over the entire ventricles ? ß 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

30
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

31
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)

32
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)

33
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?

34
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?