Physiology :
System Nervous :
III.1.2.3. Capillaries
Are tiny blood vessels, 50 times smaller than a hair, connecting arteries
and veins together. Blood flows through them very slowly, allowing
exchanges between the blood and the cells. Oxygen and nutrients are
delivered to the cell while waste products from the cell are collected by
the blood.
III.2 The circulation
The heart is in fact a double pump: one pump, the right heart. The other,
the left heart. Each of the pumps has specific functions:
- The right heart: is the pump that handles the pulmonary circulation
to send blood (not oxygenated) to the lungs.
- The left heart: is the pump that deals with the systemic circulation, which
is responsible for distributing blood (oxygenated) to the whole body
(Figure 32).
III.3. Properties of the myocardium
III.3.1. Nodal tissue and cardiac automatism
The heart has a mechanical activity which is electrically controlled.
Cardiac automaticity: existence of myocardial cells spontaneously
producing an electrical signal that stimulates neighboring cells. This set of
cells constitutes the nodal tissue.
Two cell clusters:
Sinus node or Keith and Flack.
Atrioventricular node or Aschoff-Tawara node.
Extension by the His bundle, division into 2 branches: Purkinje fiber
network. Birth of the heart stimulation process in the sinus node.
Sinus node = pace-maker imposes its rhythm to the whole heart = sinus
rhythm.
