General chest pain Flashcards
State the function of blood vessels.
- Circulate nutrient/waste
- Regulate Blood Pressure
State the significance of the parallel arrangement of vessels in the cardiovascular system.
- Allow independent regulation of blood flow to different organs
- Adapts to metabolic demands of tissues accordingly. (For example, during exercise the skeletal muscles will receive more blood than usual)
What is the average blood flow at rest in the CVS?
5 L/min
State the way by which parallel arrangement of vessels in the CVS allows independent regulation of blood flow to different organs.
- Nervous system mediated ways in which we distribute blood (e.g fight or flight)
- Sphincters control blood flow through capillaries
Which of the following is the correct order of blood vessels:
A) Aorta → arterioles → capillaries → arteries → veins
B) Aorta → venules → capillaries → arterioles → arteries
C) Aorta → arteries → arterioles → capillaries → venules
Answer: C
Which of the following figures represents the percentage of blood flow in veins, venules, and venous sinuses at any one time: A) 9% B) 45% C) 64% D) 84%
Answer: C
(84% represents the blood in systemic circulation which involves the arteries too minus pulmonary circulation and the blood in the heart at any one time)
Describe the features of the capillaries that make them the ultimate deliverer of nutrient supply to tissues around the body.
- Smallest diameter blood vessel
- Simple tube, one thick cell of flattened endothelial cells
- Allows for diffusion of nutrients, waste etc.
We cannot perfuse all the capillaries in the body at the same time, therefore control of blood flow into certain capillaries is essential. However, the capillaries are non-muscular structures.
A) Name the structure that controls the blood flow into the capillaries.
B) Describe how the metabolic of tissue may control this structure and therefore the capillary responsible for the tissue.**
A) Precarpillary sphincters (these are rings of smooth muscles which control the entry of blood from the arterioles into each capillary)
B) Lack of blood supply → ischemia → release of local factors → build up of factors → opening of the local precapillary sphincter (remember, this is because not all capillaries can be perfused at once, hence while one is open other will be closed)
A) What is a compliant vessel?
B) Give an example.
A) One that accommodates an increase in volume without generating a huge amount of pressure
B) Veins (more compliant than arteries as they have thinner walls)
non-compliant: capillaries and arterioles.
What are the three ways in which you can control the heart? And which parts of the CNS can control each way.
- Increase rate (Sympathetic)
- Decrease rate (Parasympathetic)
- Increase/regulate the force of contraction (Sympathetic)
State the equation for the calculation of mean arterial blood pressure.
MABP = diastolic pressure + 1/3 pulse pressure
Pulse Pressure= systolic pressure – diastolic pressure
Due to the effects of gravity, when standing completely, blood pressure gets higher as you go down the body reaching its peak in the legs. Which means we would experience cerebral hypoperfusion and faint if we did not have the compensatory mechanisms.
A) Name two mechanisms by which we compensate for the effects of gravity.
The effects of gravity also mean that when moving immediately from a supine position to an upright position, we experience postural hypotension, which can lead to losing balance due to a feeling of lightheadedness.
B) Describe why this occurs.
A)
• Vein valves
• Muscle pumps (aids in pumping blood back up the veins through contraction and movement)
B)
Around 500ml from the upper body to legs → decreased venous return → decreased cardiac output → decreased blood pressure → reduced blood supply to the brain
A) Using La Place’s law, explain how the diameter of a blood vessel influences its ability to contract against the pressure within it.
B) Explain how this applies to capillaries.
- La Place’s Law: T (Tension) = P (pressure against vessel wall) x R (radius)
- The larger the diameter → the greater the tension required to push against the pressure generated by the blood within the vessel → the thicker the wall of the vessel that is required to generate the tension
B) Capillary’s are under high pressure but have such a tiny radius that the tension is low and they remain only one cell thick
A) What is the Reynolds number?
B) What are factors that may increase the likelihood of turbulent flow based on the equation used to calculate the Reynolds number?
C) Why is turbulent flow problematic.
A) It is a measure of the likelihood that flow is turbulent or laminar. Above the calculated value the flow is likely to have turbulence
B) High velocity, larger diameter, low blood viscosity, abnormal vessel wall ( Re = (velocity of flow) x (radius of vessel) / viscosity))
C) Increased turbulence = increased work by heart = heart failure due to higher metabolic demand
State the equation for arterial pressure.
Cardiac output x total peripheral resistance
What is the relationship between radius and flow?
Positive relationship (bigger the radius the lower the resistance and the higher the flow)
List the structures that form the conduction pathway in the heart in the correct order.
SA Node → atrial muscle → AV Node → His Bundle → Bundle branches → Purkinje Fibers → ventricular muscle
Which cells initiate the Action potential, which spreads over the heart?
Autorhythmic cells (pacemaker cells)
Which structure of the conduction pathways sets the heart rate?
(depolarisation of) SA Node
Name the 4 locations in the heart where you can find the specialized autorhythmic cells (pacemaker cells).
- Sinoatrial Node
- Atrioventricular Node
- Bundle of Hiss
- Purkinje Fibers
As the action potential spreads over the atria, there is only one point where it can move through onto the ventricles.
A) Name this point.
As the action potential reaches the point in (A), there is a delay before it spreads over the ventricles.
B) What is the reason behind this delay?
C) Which segment on an ECG represents this delay.
A) Atrioventricular Node
B) Allows time for atrial contraction and blood to move from the atria into the ventricles before systole/ventricular contraction
C) P-R Segment
Cardiac muscles consist of muscle cells interconnected by _________, which contain junctions named _______ junctions which allow action potential to spread and a contraction to take place.
Intercalated discs, gap
Describe the generation of an action potential in pacemaker cells.
Funny sodium channels open (Na+ slowly enters) → T-type calcium channels also open and help in this slow depolarization → Ca+ and Na+ cause the Membrane potential to rise until pacemaker potential is reached → L-type calcium channel open and calcium slowly flows in → depolarization of cell → once a set threshold is reached Ca+ channels close and K+ channels open → repolarization → -ve RMP → K+ channels close and Funny Na+ channels open.
