`star` Double Circulation
`star` Regulation of Cardiac Activity
`star` Disorders of Circulatory System


● As mentioned earlier, the `color{violet}("blood pumped")` by the `color{violet}("right ventricle")` enters the `color{violet}("pulmonary")` artery, whereas the left ventricle `color{violet}("pumps blood")` into the `color{violet}("aorta.")`

● The `color{violet}("deoxygenated blood pumped")` into the `color{violet}("pulmonary artery")` is passed on to the `color{violet}("lungs")` from where the `color{violet}("oxygenated blood")` is carried by the `color{violet}("pulmonary veins")` into the left atrium.

● This pathway constitutes the `color{brown}("pulmonary circulation.")`

● The `color{violet}("oxygenated blood")` entering the aorta is carried by a network of arteries, arterioles and capillaries to the `color{violet}("tissues")` from where the `color{violet}("deoxygenated blood")` is collected by a system of `color{violet}("venules, veins")` and `color{violet}("vena cava")` and emptied into the right atrium.

● This is the `color{brown}("systemic circulation.")`

● The `color{violet}("systemic circulation")` provides nutrients, `O_2 `and other essential substances to the `color{violet}("tissues")` and takes `CO_2` and other harmful substances away for `color{violet}("elimination.")`

● A `color{violet}("unique vascular")` connection exists between the digestive `color{violet}("tract and liver")` called `color{brown}("hepatic portal system.")`

● The `color{violet}("hepatic portal")` vein carries `color{violet}("blood")` from intestine to the `color{violet}("liver")` before it is delivered to the `color{violet}("systemic circulation.")`

● A `color{brown}("special coronary system")` of `color{violet}("blood vessels")` is present in our body exclusively for the `color{violet}("circulation of blood")` to and from the `color{violet}("cardiac musculature.")`


● Normal activities of the `color{violet}("heart")` are regulated intrinsically, i.e., auto regulated by specialised muscles (`color{brown}("nodal tissue")`), hence the heart is called `color{brown}("myogenic.")`

● A special `color{violet}("neural centre")` in the medulla oblangata can moderate the `color{violet}("cardiac function")` through `color{brown}("autonomic nervous system (ANS)")`.

● `color{violet}("Neural signals")` through the `color{brown}("sympathetic nerves")` (part of ANS) can increase the rate of `color{violet}("heart beat")`, the strength of ventricular contraction and thereby the `color{violet}("cardiac output.")`

● On the other hand, `color{brown}("parasympathetic neural signals")` (another component of ANS) decrease the rate of `color{violet}("heart beat, speed")` of conduction of `color{violet}("action potential")` and thereby the cardiac output.

● `color{brown}("Adrenal medullary hormones")` can also increase the `color{violet}("cardiac output.")`


`star` `color{green}("High Blood Pressure (Hypertension):")`

● `color{brown}("Hypertension")` is the term for `color{violet}("blood pressure")` that is higher than normal (`color{brown}("120/80")`).

● In this measurement 120 mm `color{violet}("Hg")` (millimetres of mercury pressure) is the `color{brown}("systolic")`, or `color{brown}("pumping, pressure")` and 80 mm Hg is the `color{brown}("diastolic, or resting, pressure.")`

● If repeated checks of `color{violet}("blood pressure")` of an individual is `color{brown}("140/90 (140 over 90)")` or higher, it shows `color{violet}("hypertension.")`

● `color{violet}("High blood pressure")` leads to `color{violet}("heart diseases")` and also affects vital organs like `color{violet}("brain and kidney.")`

`star` `color{green}("Coronary Artery Disease (CAD):")`

● `color{brown}("Coronary Artery Disease,")` often referred to as `color{brown}("atherosclerosis,")` affects the vessels that supply blood to the `color{violet}("heart muscle.")`

● It is caused by deposits of `color{violet}("calcium, fat, cholesterol and fibrous tissues")`, which makes the `color{violet}("lumen")` of arteries narrower.

`star` `color{green}("Angina:")`

● It is also called `color{brown}("‘angina pectoris’.")`

● A `color{violet}("symptom")` of acute chest pain appears when no enough `color{violet}("oxygen")` is reaching the `color{violet}("heart muscle.")`

● `color{violet}("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 `color{violet}("blood flow.")`

`star` `color{green}("Heart Failure:")`

● `color{violet}("Heart failure")` means the state of `color{violet}("heart")` when it is not `color{violet}("pumping blood effectively")` enough to meet the needs of the body.

● It is sometimes called `color{brown}("congestive heart failure")` because congestion of the `color{violet}("lungs")` is one of the main `color{violet}("symptoms of this disease.")`

● `color{violet}("Heart failure")` is not the same as `color{brown}("cardiac arrest")` (when the heart stops beating) or a `color{brown}("heart attack")` (when the heart muscle is suddenly damaged by an inadequate `color{violet}("blood supply")`).