Here are the key points about the baroreceptor reflex: - Baroreceptors are pressure sensors located in the carotid sinuses and aortic arch. - When blood pressure increases, the baroreceptors are stimulated and send action potentials to the cardioregulatory center in the medulla oblongata. - The cardioregulatory center responds by increasing parasympathetic stimulation and decreasing sympathetic stimulation to the heart. This lowers heart rate and stroke volume. - The end result is a decline in blood pressure, providing a negative feedback loop to maintain normal blood pressure levels. The baroreceptor reflex is an important autonomic mechanism that helps regulate short-term blood pressure through adjustments to

1. 10 -11-12th weeks: Cardiovascular System
Lecturer: Ablaikhanova N.T.
Assistant: Balmaganbet Zarina
Plan:
1. Cardiovascular system
2. Functions of cardiovascular system
3. Circulatory system types
4. Cardiac muscle
5. Heart walls
6. Heart and its functions
7. Blood vessels

2. Cardiovascular
System
• The blood circulatory system
(cardiovascular system) delivers nutrients
and oxygen to all cells in the body. It
consists of the heart and the blood vessels
running through the entire body. The
arteries carry blood away from the heart;
the veins carry it back to the heart.

3. The functions of Cardiovascular System
1. To transport nutrients, gases and waste products around the body:
- Nutrients such as glucose from digested carbohydrate are delivered from the digestive tract to the muscles and organs that
require them for energy.
- Hormones (chemical messengers) from endocrine glands are transported by the cardiovascular system to their target
organs, and waste products are transported to the lungs or urinary system to be expelled from the body.
2. To protect the body from infection and blood loss:
- Blood contains three types of cells as listed below and shown in the adjacent image.
• Red blood cells
• White blood cells
• Platelets
3. To help the body maintain a constant body temperature (‘thermoregulation’):
- As temperatures move further into hypo or hyperthermia they become life threatening. Because of this the body works
continuously to maintain its core temperature within the healthy range. This process of temperature regulation in known as
thermoregulation and the cardiovascular system plays an integral part.
4. To help maintain fluid balance within the body:
- The cardiovascular system works in conjunction with other body systems (nervous and endocrine) to balance the body’s
fluid levels. Fluid balance is essential in order to ensure sufficient and efficient movement of electrolytes, nutrients and
gases through the body’s cells.

4. Humans have a double circulatory system. The heart pumps blood through two circuits:
1. The pulmonary circulation;
2. The systemic circulation.
Circulatory system is divided into two
parts
1. The systemic circulation (Greater circulation with high resistance circuit) passing through the tissues.
The systemic circulation provides the functional blood supply to all body tissue. It carries oxygen and
nutrients to the cells and picks up carbon dioxide and waste products. Systemic circulation carries oxygenated
blood from the left ventricle, through the arteries, to the capillaries in the tissues of the body. From the tissue
capillaries, the deoxygenated blood returns through a system of veins to the right atrium of the heart.
2. The pulmonary circulation (Lesser circulation) with low resistance circuit) passing through the lungs.
The circular movement of blood was described in 1628 year by William Harvey. Pulmonary circulation
transports oxygen-poor blood from the right ventricle to the lungs, where blood picks up a new blood supply.
Then it returns the oxygen-rich blood to the left atrium.

5. • The cardiac muscle is responsible for
the contractility of the heart and,
therefore, the pumping action. The
cardiac muscle must contract with
enough force and enough blood to
supply the metabolic demands of the
entire body. This concept is termed
cardiac output and is defined as heart
rate x stroke volume.

6. Morpho functional characteristics of cardiac
muscle
Morphological
features
Metabolic features
of myocardium
Myocardium

7. Morphological features
 Cardiac muscle cells (cardiomyocytes) are striated, branched, contain many mitochondria, and are under
involuntary control. Each myocyte contains a single, centrally located nucleus and is surrounded by a
cell membrane known as the sarcolemma. The sarcolemma of cardiac muscle cells contains voltage-
gated calcium channels, specialized ion channels that skeletal muscle does not possess.
Cardiac Muscle Skeletal Muscle

8. There are two types of muscles in myocardium: typical (contractile) and atypical.
Functional Syncytium. Cardiac muscles are separated from one another by intercalated discs
which have low electrical resistance, allowing free diffusion of ions.
Cells of myocardium are rich by mitochodria.

9. Metabolic features of
myocardium
Cyclical exchange processes.
Electromechanical connection. The role of calcium ions in the AP generation.
The ability of the myocardium to adsorb from the blood energetic substances.
Intensive oxygen consumption.
The processes of re-synthesis and regeneration are realized rapidly.

11. Myocardium
 It is the muscular middle layer of the heart that is sandwiched between the epicardium and
endocardium. Sometimes it is referred to as the mass of the heart. The myocardium is made up of two
types of cells: cardiac muscle cells(also called heart muscle cells,cardiomyocytes, cardiac
myocytes, or cardiac rahbdomyocytes) and fibroblast.
 The heart is the central circulatory organ in the human body that circulates the blood throughout the
body. The heart is located in a thin fibroelastic, double-layered, fluid-filled sac known as
“pericardium”. The two layers of the pericardium are the outer fibrous or parietal pericardium and
the inner serous or visceral pericardium.

12. The three layers of the heart wall
•Epicardium: It is the outermost layer of the heart wall. This
contains mesothelial cells under which are connective and adipose
tissues. This layer also constitutes the visceral layer of the serous
pericardium. Below the epicardium coronary arteries and veins,
lymphatic vessels, and nerves are present.
•Myocardium: This is the muscle layer of the heart responsible for
the pumping action of the heart and occupies 95% of the
cardiomyocytes mass and is the thickest layer in the heart wall. The
thickness of the myocardial layer is dependant on the pressure which
is present in each chamber.
•Endocardium: This is the innermost layer that lines the inner wall
of the heart and also lines the heart valves. The endocardium is
further subdivided into two layers: (1) an inner endothelial cell layer
that lines the heart chamber and (2) the second layer is the
subendocardial layer which is a connective tissue layer in
continuation with the connective tissue of the myocardial connective
tissue layer. The impulse-conduction system of the heart is placed in
this subendocardial layer.

24. 11-12th week lectures
Cardiovascular system

25. Heart cycle, its
periods
Ventricular systole - 0.1 s.
Ventricular diastole - 0.7 s.
Ventricular systole - 0.3 - 0.33 s.
Decay period - 0.08 s
Relaxation period - 0.25s
Ventricular diastole - 0.47 s.
Fast pumping - 0.12 s
Slow pumping - 0.13 s

26. Systolic blood volume
The volume of blood coming out of the heart during one systole (equal to 65-70 ml when systole is min.
70-75 times).

27. Minute blood volume
The volume of blood leaving the heart in one minute (4.5-5.0 l). The minute blood volume is
determined by Fick's method with the introduction of indifferent dyes and integral rheograph,
radioactive isotopes.

30.  Cardiac index is a measure that describes the unit of blood supply to the body surface in one
minute.
Appearances of cardiac activity, research methods.
1. Sound (auscultation, PCG).
2. Mechanical (palpation, DKG, BKG).
3. Electrical (ECG, VKG, etc.).

36. Invasive research method
The invasive method is very often used in medicine and provides information about the changes in
pressure inside the heart, inside the veins, the main indicators of hemodynamics, coronary blood flow
and the state of the valvular apparatus of the heart.
This method includes:
Catheterization of the heart cavity and trunk vessels;
Selective injection of a thrombolytic drug into the coronary artery;
Transluminal angioplasty (expansion) of coronary vessels; Electrical
irritation of the heart.

43. The baroreceptor reflex keeps the heart rate and
stroke volume within normal ranges. When the
blood pressure increases, the baroreceptors are
stimulated. Action poten-tials are sent along the
nerve fibers to the medulla oblongata at
increased frequency. This prompts the
cardioregulatory center to increase
parasympathetic stimulation and decrease
sympathetic stimulation of the heart. As a result,
the heart rate and stroke vol-ume decrease,
causing blood pressure to decline.