Qualification > Sciences
Edexcel BIOLOGY Doubts!!!!
Weaam:
I know the writing isnt clear.
It says: (on the top) the diagram below shows the structure of the heart.
(under the picture) Suggest which stage on the cardiac cycle is shown in the diagram and give a reason for your answer.
Deadly_king:
--- Quote from: weaam on December 03, 2010, 01:44:26 pm ---Well, the first is about a diagram so u cant answer it.
But the second says, Explain how the properties of a phospholipid contribute to the structure of the cell membrane.
--- End quote ---
Phospholipid consist of two main parts; a polar(hydrophilic) head and a non-polar(hydrophobic) tail.
This allows the membrane to line up in such a way that the head faces the aqueous medium while the tails are inside away from water.
Amelia:
--- Quote from: Pink Princess on December 02, 2010, 08:29:24 am ---Guys I srsly need ur help in this ECG it's killing me =(
--- End quote ---
I'll give a simple explanation. Simple according to me :P I hope it helps.
A electrocardiogram (ECG) is a recording of the electrical changes that occur in myocardium (it is the major portion of the heart consisting largely of Cardiac muscle tissue) during a cardiac cycle. Body fluids contain ions that conduct electric currents. Therefore, the electrical changes in myocardium can be detected on the skin's surface. When an ECG is being taken, electrodes are placed on the skin are connected by wires to an instrument that detects the myocardium's electrical changes. Thereafter, a pen rises or falls on a moving strip of paper. The image below depicts the pen's movements during a normal cardiac cycle.
(Ignore da formula)
When the SA node triggers an impulse, the atrial fibres produce an electrical change called the P wave. The P wave indicates the atria are about to contract. After that, the QRS complex signals that the Ventricles are about to contract. The electrical changes that occur as the ventricular muscle fibers recover to produce the T wave.
P.S - My dad rocks. ;) ;D. (Ok, that was too random. :D)
obstacle26:
The graph below shows changes in the blood pressure in the aorta and the left ventricle during two complete cardiac cycles.
(a) On the graph, draw an arrow to show when the left atrioventricular (mitral) valve closes.
(b) Use the information in the graph to calculate the heart rate. Show your working.
Don't know how to calculate the heart rate (b) , anyone explain
Markscheme says: (b) 60 ÷ 1.0 ; [accept equivalent calculations] = 60 beats per minute ; [accept range 60 to 64], but how does 60 beats come only pressure and time in seconds is given? Thanx in advance :)
Amelia:
Heart rate is the number of heartbeats per unit of time - typically expressed as beats per minute (bpm) - which can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep.
Typical healthy resting heart rate in adults is 60–80 bpm
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