Sue - The Vascular System Flashcards
Give the characteristics of arteries?
High pressure, elastic outer layer , small lumen, smooth inner layer
Give the characteristics of capillaries?
Large SA, one cell thick to slow blood down for diffusion = narrower diameter
Give characteristics of veins?
Thinner muscle, low pressure, valves to prevent back flow, wider lumen
Order of the circulatory system
Heart > Arteries > Arterioles > Capillaries >Venules > Veins
What occurs in the arterioles?
Vasoconstriction and Vasodilation
Blood pressure =
blood flow x resistance
Systolic pressure…
Contraction forcing blood out, increasing pressure (120)
Diastolic pressure…
Relaxation, decreases pressure in the ventricles (80)
Name some Venous return mechanisms
- The Skeletal muscle pump
- The respiratory pump
- Valves
- A thin layer of smooth muscle within the veins
- Gravity
How does the Skeletal pump work?
When muscles contract they press on nearby veins causing a pumping effect
and squeezing the blood towards the heart
How does the Respiratory pump work?
When muscles contract and relax the processes of inspiration and expiration
cause pressure changes
which compress nearby veins
and assist blood to return back to the heart
What is Venous Return?
The amount of blood returning to the heart
How does blood redistribution occur?
Detection by chemoreceptors, baroreceptors and proprioreceptors send impulse to medulla so vasoconstriction/dilation occurs to redistribute blood to places that need it most and those areas that don’t
During exercise, what area’s of the body need more blood?
The heart > needs MORE oxygen to beat faster
The muscles > needs MORE oxygen for energy
The Skin > energy is needed to cool the body down
The difference between the oxygen content of the arterial blood arriving at the muscles and the venous blood leaving the muscles
Arterio-venous Difference (a-vO2 diff)
During exercise the a-vO2 diff is high, how does this affect gas exchange?
Increases gas exchange at the alveoli sop more oxygen is taken in and more CO2 is removed
Has is oxygen transported around the body?
By haemoglobin - 4 molecules at any one time
‘Muscle haemoglobin’ that acts as a store of oxygen in the muscle fibres
Myoglobin
Give three factors that cause the Bohr Shift
Decrease in blood pH, increase in blood temperature and increase in blood CO2
What is the Bohr Shift (move to the right)?
When muscles require more oxygen the dissociation (movement) of oxygen from haemoglobin in the blood capillaries to the muscle tissue occurs more readily
