Ch.23 Circulation

WHAT IS A HEART ATTACK?
A heart attack is when cardiac muscle gets damaged typically from a blocked coronary artery. Atherosclerosis is plaques develop inside inner walls of blood vessels. Plaques narrow blood vessels. Blood flow is reduced.

WHAT ARE THE DIFFERENCES AND SIMILARITIES BETWEEN ARTERIES AND VEINS?
Arteries carry blood away from the heart. Aorta is the largest arteries. Veins carry blood towards the heart. Superior, inferior vena cave is the largest veins. They both lined by single layer of epithelial cells. The smooth muscle in walls can reduce blood flow. Elastic ibers permit recoil after stretching. Veins have one-way valves that restrict backward flow.

HOW DOES BLOOD TRAVEL AGAINST GRAVITY?
Blood travels by pressure from muscle contractions between two muscles and between muscles and bone or skin. Also when veins are squeezed, blood can travel against gravity. One other way of blood traveling against gravity is one way valves limit blood flow to one direction, towards heart.

SUMMARY:
For circulatory system, all cells need nutrients, gas exchange which was discussed about in last blog, and removal of wastes. Diffusion alone is inadequate for large and complex bodies. Arthropods and many molluscs use open circulatory systems while other animals use closed circulatory system. The mamalian heart has two thin-walled atria and thick-walled ventricles. The pacemaker sets the rate of heart contractions and it generates electrical signals in atria. Heart attack is damage to cardiac muscle typically from a blocked coronary artery. Stroke is death of brain tissue from blocked arteries in the head. Capillaries have thin walls and are narrow and increase surface area for gas and fluid exchange. Veins and arteries are the main types of blood that go through the heart. Blood pressure is the force blood exerts on vessel walls. It depends on cardiac output and resistance of vessels. It decreases as blood moves away from heart. Hypertension is a serious cardiovascular problem. It can cause heart to work harder, weakening over time, increased plaque formation from tiny ruptures, and increased of blood clot formation. Those conditions can cause heart attacks, strokes, and kidney failure.
Blood consists of red and white blood cells suspended in plasma. Plasma is the fluid that contains various inorganic ions, proteins and nutrients, wastes, gases, and hormones. RBCs transport oxygen bound to hemoglobin. WBCs function inside and outside the circulatory system. They fight infections and cancer. The blood-clotting process is platelets adhere to exposed connective tissue, platelets form a plug, and a fibrin clot traps blood cells. Stem cells divide in bone marrow to produce all the types of blood cells throughout life and they are used to treat some blood disorders.



KEY TERMS:
- Open circulatory systems: heart pumps blood through open-ended vessels
- Closed circulatory system: heart pumps blood through arteries to capillaries
- Double circulation: separate pulmonary and systemic circuits
- Diastole: blood flows from veins into heart chambers
- Systole: blood flows from atria into ventricles
- Cardiac output: amount of blood/minute pumped into systemic circuit
- Heart rate: number of beats/minute
- Heart valves: prevent the back flow of blood
- Heart murmur: a defect in one or more heart valves
- The AV node: relays these signals to the ventricles

This is a diagram of inside a red blood cell and shows the structure of hemoglobin. Hemoglobin has red pigment, which makes the blood red. Hemoglobin carries oxygen throughout the body and it contains oxygen molecule. Red blood cell is made of hemoglobin.

http://www.youtube.com/watch?v=WXOBJEXxNEo

This video talks about the oxygen transport in the body.

5 FACTS:
1) Circulatory systems facilitate exchange with all body tissues.
2) Blood flow through the double circulatory system of humans.
3) The pacemaker sets the tempo of the heartbeat.
4) Smooth muscle controls the distribution of blood.
5) Capillaries allow the transfer of substances through their walls.