3.10.3 Biological Measurement Flashcards
What side of the heart is responsible for pumping deoxygenated blood to the lungs?
Right
What side of the heart is responsible for pumping oxygenated blood around the body?
Left
What directions do veins go?
veINs go INto the heart
What direction do arteries go?
Go away from the heart, out to the body.
What is the purpose of valves?
Stop backflow of blood
Why do muscles contract?
They are stimulated by electrical signals
What does the sinoatrial (SA) node control?
Controls the contraction of the atria.
What does the atrioventricular (AV) node control?
Controls the contraction of the ventricles.
How many electrical pulses does the SA produce per minute?
70
What do nerve cells do?
Carry impulses (electrical signals) around the body.
What do dendrites do?
Carry signals to other cells.
What does the nerve fibre consist of?
Aton and Myelin Sheath
What does the nerve fibre do?
Passes the signal along to contract the muscle.
What do the signals (that the nerve cell carries) depend on?
The concentration of K+ and Na+ ions inside and outside the cell membrane.
What happens during Resting (no signal)?
There is a large conc. of K+ inside, and Na+ outside.
The Na+ concentration is bigger, so there is p.d. across the membrane - cell is polarised.
- membrane is not permeable.
What happens during Action (cell stimulated)?
Cell membrane is permeable to Na+, and they diffuse through due to a concentration gradient and negative ions inside.
What happens if the stimulus is big enough?
The threshold potential (around -55mV) is reached.
The flow of ions increases rapidly, decreasing the p.d
[depolarisation]
What happens when the p.d reaches 0V?
It’s depolarised
What value(s) does the p.d continue to flow to?
+30mV
(+40mV for the heart)
What happens to the cell membrane when it’s reversed polarised?
Membrane is impermeable to Na+ ions.
What happens during repolarisation?
Membrane now permeable to K+ ions, which diffuse through and restore the original p.d balance.
What happens before the p.d goes back to its resting position?
It gets an ‘overshoot’
How long does the process (of stimulus causing depolarisation and repolarisation) take?
2 ms
What is contraction in the heart controlled by?
SA and AV nodes
How long does the contraction in the heart take?
0.2 s
What is depolarisation?
The contraction of muscle
What is repolarisation?
The muscle relaxing
What does ECG stand for?
Electrocardiography
Why are electrodes placed on the certain parts of the skin surface for an ECG?
Needs to be where arteries are close to the surface.
How is contact conductivity improved during an ECG?
Clearing/ removing hair
Removing dead skin cells (exfoliating)
Use of electrolyte gel
What does an electrolyte gel do?
Removed air gap so there is better contact conductivity.
Why do signals received from an ECG need amplifying?
Signals at the surface are weak.
What parts of the body are used in an ECG?
Limbs
Chest
Why isn’t right leg used in an ECG?
Too far away from heart (arteries)
How many electrodes are used during an ECG?
3
How are the electrodes used in an ECG?
2 held at 0 potential + connected to 2 diff. limbs.
Other attached to remaining limb.
[it is possible to record the difference in potential between one limb and the average of the other two]
What does trace depend on?
Where the electrodes are put.
What is a P-wave?
The depolarisation and contraction of the atria.
What is the QRS-wave?
The depolarisation and contraction of the ventricles.
What is a T-wave?
The repolarisation and relaxation of the ventricles.
