WELCOME..... TO .....HIGH SCHOOL BIOLOGY BLOG !!!

Tuesday, July 19, 2011

Cardiac cycle






Cardiac Cycle

1.       Heart contracts + relaxes in a rhythmic cycle.

2.     Cardiac cycle consists of alternating periods of :
·        Systole - contraction phase.
·        Diastole - relaxation phase.

3.     Cardiac cycle = one complete sequence of systole + diastole

4.     Resting adult - cardiac cycle repeated 72 times per minute = resting heart rate.

5.     Pulse = causes by elastic recoil of arteries.

6.     Ventricular pressure + aortic pressure + ventricular volume:
  • changes (in response to the events that occur)
  • at different phases of cardiac cycle.
7.     During diastole:
  • pressureof heart chambers decreases
  • volumeincreases (as blood is pumped in).
8.     During systole:
  • pressureof heart chambers increases
  • volumedecreases (as blood is pumped out).
9.     When aortic pressure > ventricular pressure
à semilunar valves shut + vice versa.

10.  When ventricular pressure > atrial pressure
à AV valves shut + vice versa.

11.   Valves = ensure blood only flows in right direction.

Tuesday, July 12, 2011

Transport In Animals

1. Human heart : 
  • consists of 4 chambers : right atrium, right ventricle, left atrium and left ventricle
  • pump blood to all parts of the body.
  • made up of cardiac muscle. 


Front/venrtral  view of heart
 
2. Superior vena cava
    --> carries deoxygenated blood
    --> from the head + arms
    --> into right atrium.
3. Inferior vena cava
    --> carries deoxygenated blood
    --> from the lower body + legs
    --> into right atrium
4. Right atrium
    --> receives deoxygenated blood
    --> from vena cava
    --> to right ventricle. 
5. Tricuspid (antrioventricular) valves
    --> prevent blood (from right ventricle) flowing backwards
    --> to the right atrium.
6. Right ventricle
    --> pumps blood
    --> to lungs
    --> via pulmonary arteries.
7. Semilunar valves
    --> prevent blood (from pulmonary arteries)
    --> from flowing backwards
    --> into right ventricle.
 


Cross-section of heart
  






8.   Pulmonary artery branches
      --> carries deoxygenated blood
      --> from right ventricle 
      --> to lungs.
9.   Pulmonary vein
      --> carrying oxygenated blood
      --> from lungs
      --> to left atrium.
10. Left atrium
      --> receives oxygenated blood
      --> from lungs 
      --> to left ventricle.
11. Bicuspid (atrioventicular) valves
      -- > prevent blood (from left ventricle) flow backwards to left atrium
12. Left ventricle
      --> pumps oxygenated blood
      --> to body tissue (via aorta).
13. Semilunar/aortic valves
      --> prevent blood (from aorta) flowing backwards (into left ventricle).
14. Aorta
      --> carries oxygenated blood
      --> from left ventricle
      --> to the rest of the body.
15. Septum separates the right and left side of the heart.



Simplified version of heart