Essential Terminologies and Concepts of CVS

Essential Terminology and Concepts of CVS

Systole- each period of contraction

Diastole – each period of relaxation

Heart rate/Pulse rate (HR) - the number of times the heart contracts/beats per minute (Av.-75 at rest)

Stroke volume (SV) - the amount of volume ejected by each ventricle (equal for both ventricles- 70ml at rest)

Cardiac output (CO) - total volume each ventricle ejects per minute (= HR*SV) i.e. at rest CO= 70/min * 70ml= 4900ml/min or approximately 5l/min

Venous returns- amount of blood that returns from the veins to the heart per minute. Under normal circumstances = CO.

Hydrostatic pressure – the pressure exerted by the blood onto the walls of blood vessels. We have systolic and diastolic pressure.

Vascular resistance- the resistance of the blood vessels to blood flow.

–        Total Peripheral resistance (TPR) –The resistance of all blood vessels down stream to the Aorta.

–        Pulmonary vascular resistance (PVR) - The resistance of all blood vessels down stream to the Pulmonary artery.

        TPR is 7 times more than PVR. This is because the pulmonary blood vessels are shorter and wider than the systemic, and this is why the walls of the left ventricle are thicker and more muscular than the right. to over come the resistance.

Blood pressure- in the arteries average- 90-120mmHg, in the veins 1-2mmHg.

Þ    describe CCF, Aneurysm

Anatomical distribution of the CO- The distribution depends on the resistance of the arterioles in the region. Tissues with low vascular resistance receive a higher proportion of the CO. The resistance depends mainly on the diameter of the vessels. In certain circumstances these can be changed e.g. during exercise, the arterioles in the skeletal muscle dilate while those to the GIT constrict, thus allowing more blood to go to the skeletal muscle at the expense of the supply the GIT.

Þ    List the distribution of the CO in the body systems and the blood volume in the vascular system. (The veins keep 60% of the blood)

Þ    Why are the veins referred to as blood reservoirs? Why do women have less blood than males?

Þ    Define the term Haematocrit and state its significance to the blood flow.

Þ    Discuss the Mechanical events of the cardiac cycle and relate them with the electrical events in the following format:

1. Ventricular filling
2. Isovolumic ventricular contraction
3. Ejection
4. Isovolumic ventricular relaxation

Þ    Explain the origin of the heart sounds viz lubb, dup and murmurs

Þ    Differentiate the parasympathetic innervation of the heart from the sympathetic, in terms of their location and effects.

Þ    Define inotropic and chronotropic properties, tachycardia and bradycardia.

Þ    Explain why the heart rate will increase to about 100 beats/min, if you block both the sympathetic and parasympathetic flow to the heart.

Þ    Describe the structure of the various blood and lymph vessels.

The Blood

It is a tissue composed of:

-          a solid phase of formed elements- Cells and part of cells and

-          Liquid phase-plasma.

Lymph is formed from blood by filtration at the capillaries due to hydrostatic pressure. It's low in protein content as compared to the blood. It is returned to the venous circulation via the lymphatic vessels at the thoracic duct. The lymphatic vessels have one way valves. Along the way the fluid passes through Lymph nodes where it is inspected for foreign substances e.g. bacteria and they are filtered.

Blood constituents

1. RBC- carries and protects Haemoglobin.

Describe the structure of RBCs

Define the terms; red cell count, mean corpuscular volume, erythrocyte sedimentation rate and their significance.

2. WBCs (Leucocytes)

List the various types and their functions

3. Megakaryocytes and Platelets

-Platelets have no nucleus

-contain Golgi apparatus, ER, Enzymes, Microtubules and filaments.

-Functions- Haemostasis, Phagocytosis, storage and transport of 5-HT and Histamine.

4. List the constituents and functions of Plasma.

Functions of Blood

1.       Ionic and Osmotic balance- the blood proteins i.e. Albumins and Globulins are the ones that maintain osmotic pressure in the capillaries. (They do not cross the capillary walls due their size) this is called Oncotic pressure.

2.       Nutrition and excretion- transports nutrients, hormones, waste products, drugs and their metabolites.

3.       Blood gases

4.       Buffering

5.       Protection

6.       temperature control

7.       Turgor- controls tone of the skin, turgidity of the organs and provides the hydraulic pressure for the erection of the penis.

Created by: Musango 26/3/11