Body fluids and Circulation 3 Flashcards
what is electrocardiograph and electrocardigram
This type
of machine (electro-cardiograph) is used to obtain an electrocardiogram
(ECG). ECG is a graphical representation of the electrical activity of the
heart during a cardiac cycle.
how is ecg obtained
To obtain a standard ECG,a patient is connected to the
machine with three electrical leads (one to each
wrist and to the left ankle) that continuously
monitor the heart activity. For a detailed
evaluation of the heart’s function, multiple
leads are attached to the chest region.
define:
(i) polarisation
(ii) depolarisation
(i) The polarised state of a membrane refers to the membrane at a stage of rest with set charges on the inner and outer side of the membrane.(+ outside, - inside)
(ii) When a stimulus strikes a membrane, the charges get reversed and the membrane is said to the depolarised. this results in the generation of action potential.( - inside, +inside)
explain the different waves
The P-wave represents the electrical
excitation (or depolarisation) of the atria,
which leads to the contraction of both the atria.
The QRS complex represents the depolarisation of the ventricles,
which initiates the ventricular contraction. The contraction starts shortly
after Q and marks the beginning of the systole.
The T-wave represents the return of the ventricles from excited to
normal state (repolarisation). The end of the T-wave marks the end of
systole.
how is ecg useful
Obviously, by counting the number of QRS complexes that occur in a
given time period, one can determine the heart beat rate of an individual.
Since the ECGs obtained from different individuals have roughly the same
shape for a given lead configuration, any deviation from this shape
indicates a possible abnormality or disease. Hence, it is of a great clinical
significance.
explain the souble circulation of theheart
(i)As mentioned earlier, the blood pumped by the right ventricle enters the
pulmonary artery, whereas the left ventricle pumps blood into the aorta.
The deoxygenated blood pumped into the pulmonary artery is passed on
to the lungs from where the oxygenated blood is carried by the pulmonary
veins into the left atrium. This pathway constitutes the pulmonary
circulation.
(ii) The oxygenated blood entering the aorta is carried by a
network of arteries, arterioles and capillaries to the tissues from where
the deoxygenated blood is collected by a system of venules, veins and
vena cava and emptied into the right atrium. This is the systemic
circulation (Figure 18.4). The systemic circulation provides nutrients, O2
and other essential substances to the tissues and takes CO2
and other
harmful substances away for elimination.
what is the hepatoc portal system
A unique vascular connection
exists between the digestive tract and liver called hepatic portal system.
The hepatic portal vein carries blood from intestine to the liver (for detoxification)before it is
delivered to the systemic circulation. A special coronary system of blood
vessels is present in our body exclusively for the circulation of blood to
and from the cardiac musculature.
explain the structure of blood vessel
The blood flows strictly by a fixed route through Blood Vessels—the
arteries and veins. Basically, each artery and vein consists of three layers:
an inner lining of squamous endothelium, the tunica intima, a middle
layer of smooth muscle and elastic fibres, the tunica media, and an
external layer of fibrous connective tissue with collagen fibres, the tunica
externa. The tunica media is comparatively thin in the veins
how is cardiac activity regulated
Normal activities of the heart are regulated intrinsically, i.e., auto regulated
by specialised muscles (nodal tissue), hence the heart is called myogenic.
A special neural centre in the medulla oblangata can moderate the cardiac
function through autonomic nervous system (ANS). Neural signals through
the sympathetic nerves (part of ANS) can increase the rate of heart beat,
the strength of ventricular contraction and thereby the cardiac output.
On the other hand, parasympathetic neural signals (another component
of ANS) decrease the rate of heart beat, speed of conduction of action
potential and thereby the cardiac output. Adrenal medullary hormones
can also increase the cardiac output.
what is hypertensions
Hypertension is the term for blood
pressure that is higher than normal (120/80). In this measurement 120
mm Hg (millimetres of mercury pressure) is the systolic, or pumping,
pressure and 80 mm Hg is the diastolic, or resting, pressure. If repeated
checks of blood pressure of an individual is 140/90 (140 over 90) or
higher, it shows hypertension. High blood pressure leads to heart diseases
and also affects vital organs like brain and kidney.
what is cad
Coronary Artery Disease, often referred
to as atherosclerosis, affects the vessels that supply blood to the heart
muscle. It is caused by deposits of calcium, fat, cholesterol and fibrous
tissues, which makes the lumen of arteries narrower.
what is angina
It is also called ‘angina pectoris’. A symptom of acute chest pain
appears when no enough oxygen is reaching the heart muscle. Angina
can occur in men and women of any age but it is more common among
the middle-aged and elderly. It occurs due to conditions that affect the
blood flow.
what is hear failure
Heart failure means the state of heart when it is not pumping
blood effectively enough to meet the needs of the body. It is sometimes
called congestive heart failure because congestion of the lungs is one of
the main symptoms of this disease. Heart failure is not the same as cardiac
arrest (when the heart stops beating) or a heart attack (when the heart
muscle is suddenly damaged by an inadequate blood supply).
what is clottting of blood
Blood exhibits coagulation or clotting
in response to an injury or trauma. This is a mechanism to prevent
excessive loss of blood from the body.
Calcium ions play a very important role in clotting
explain the process of clotting
-An injury or a trauma stimulates the platelets in the blood to release
certain factors which activate the mechanism of coagulation. Certain
factors released by the tissues at the site of injury also can initiate
coagulation.
-These factors perform a seires of linked enzymatic reactions ( cascade process) which form an enzyme complex called thrombokinase.
-Prothrombins are inactive substance present in the plasma which in the presence of thrombokinase give rise to thrombins.
-Fibrins are formed by the conversion of inactive fibrinogens in
the plasma by the enzyme thrombin.
- a clot or coagulam formed mainly of a network of threads
called fibrins in which dead and damaged formed elements of blood are
trapped.
