cardio-vascular system. outline 1- overview 2- path of blood through the heart and vasculature 3-...

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

Overview

• Roles:

- Pumps blood throughout the body vasculature

- Endocrine function • Components

- Heart

- Blood vessels

- Blood

Outline

• 1- Overview






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






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






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






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






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


heart per minute







• 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?


• 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


heart per minute






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?

cardio-vascular system. outline 1- overview 2- path of blood through the heart and vasculature 3-...

Documents

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cardiac tamponade slide

blood flow

cardiac output