Please enable JavaScript.
Coggle requires JavaScript to display documents.
Blood circulation, Characteristics, CARDIAC CYCLE, The sino atrial node…
Blood circulation
THE HEART
This organ is dived into 4 chambers : left & right atria (collecting chamber) left &right ventricles (pumping chambers)
The walls of the heart are made of cardiac muscle, muscles with a very unique function which is to contract and relax without the intervention on nerves. This is called myogenic contraction
-
The muscular wall of the heart are made of many capillaries these are supplied with blood by the coronary arteries. The blood that carries the coronary arteries contains nutrients as well as oxygen for reaction the aerobic respiration which provides energy for the myogenic contraction
-
-
-
-
-
-
Left side : pump through the aorta oxygenated blood to the rest of the body organs(except the lungs)
-
-
-
-
Characteristics
Arteries: tough outer coat // thick walls (to withstand the high pressure // narrow lumen // thick layer containing fibres to maintain high pressure
Capillaries : permeable walls to allow the exchange of material between the tissues // wall consist of single thin layer of cells to facilitate diffusion // narrow lumen thus small surface area to allow the capillaries to fit anywhere // pores between the cells that make up the walls to let some plasma leak out (phagocytes may leak out as well)
Veins : thin outer coat // wide lumen to "accommodate" the low pressure // contains valves to prevent back flow // thin walls which allow the vein to be flattened in order for blood to flow // thin layers with some or no fibres tissues.
CARDIAC CYCLE
Constitutes of muscles that can contract and relax without the intervention of the nervous system, they are called myogenic muscles. They have an inherent rate, for the atria its 60 beats per minute and for the muscles of the ventricle it is 20beats per minute
-
The wall of the atrium constitutes of a the sinoatrial node located in between the inferior and superior venacava. It has the greatest inherent rate of 72 beats per minute. It also called a pacemaker because it imposes itself onto the inherent rates of the other muscle which also explains how the heart beats 72 times per minute
The cycle of actions: 1.Contraction of the atria pushes blood into the ventricles via the atrio-ventricular valves which are opened unlike the semi-lunar valves, so the ventricles then feel up with blood
- Then the wall of the ventricles contract, pressure increases and cause the closing of atrio-ventricular valves(preventing the blood flow of blood to the atria) but opening of the semi-lunar valves letting blood in the arteries. In parallel step one is happening again.
- The ventricles relaxes, pressure falls, semi-lunar valves closes to prevent back flow form the arteries to the ventricles, the atrio-ventricular valves open to receive blood from the veins in the atrium and starts flowing again to fill up the ventricles. And the cycle re-starts as soon as the atria contracts.
The sino atrial node generates an electric impulse that flow through the right atrium muscles then the left atrium muscles. On the other hand,the ventricles are "shielded",insulated against this electric impulse due to a fibrous tissue with a high electricity resistance within the muscles.
And so it's takes longer for the impulse to reach to the ventricles because it must overcome this resistance and it must through the atrio ventricular node
message can be carried to the SA node through
1.impulses : impulses from the medulla of the brain, indicates the heart to change it's speed; one nerve is there speed up and the other one slows the heart down.
2.hormones : When helping the heart prepare for vigorous activities a hormone called epinephrine is secreted, it's speed up the heart rate
-
The coronary artery disease is a heart condition where "fatty plaque" builds up in the inner lining of arteries. Usually arteries have a wide lumen but this condition makes them narrowed.
The blood flow to the cardiac muscle is then restricted as this condition because severe, leading to chest pains. Mineral that also build up in the plaque cause the passage to become hard and rough
This condition maybe cause by :
-high blood cholesterol levels
-smoking
-high blood pressure (hypertension)
-high blood sugar (diabetes)
-genetic factors