Module 1 Lecture 4 Flashcards
Label the diagram on blood pressure throughout circulation!
–
What does blood pressure gradient do?
the blood pressure gradient keeps blood flowing from high to low
What is blood pressure depended on?
- the volume of blood and the compliance of vessel, Fluctuates throughout the systemic circulation & during the cardiac cycle
What is systolic pressure?
– Systolic pressure is the max
pressure in arteries when blood
is pumped into them
What is diastolic pressure? what is the diagram yo?!
Diastolic pressure is the min
pressure in arteries when there
is no heart contraction & blood
continues to flow into arterioles
What is pulse pressure?
Pulse pressure is the difference between systolic & diastolic pressures. It is this pressure difference we can feel when taking our pulse
What is mean arterial pressure?
Mean arterial pressure is the average pressure during each cardiac cycle. This is the pressure that the body monitors & regulates
What is MAP
MAP = diastolic pressure + 1/3 (systolic – diastolic)
MAP is the average pressure during each cardiac cycle
What is MAP’s Main purpose?
The main purpose of MAP is to drive blood into tissues
Blood flow to organs depends on what?
Blood flow to any given organ depends on:
1. resistance of local arterioles
2. vascularisation/open capillaries
MAP is the driving pressure head
Driving pressure head in arteries diagram, explain!
Why must MAP be closely monitored and regulated?
MAP must be closely monitored & regulated to ensure:
1. high enough for sufficient drive, despite local
adjustments
2. low enough to avoid damage to heart & blood
vessels
What are the 2 determinants of MAP?
Regulation occurs through the integration of elaborate
mechanisms, involving various aspects of the body. The
two determinants of MAP are:
MAP = CO x TPR
NOTE DIAGRAM
A change in any factor will change MAP unless another factor changes to compensate for it
When MAP deviates from a normal ‘set-point’ numerous
responses are initiated, what are they?
Short-term: autonomic nervous system to heart,
veins, & arterioles as well as hormones -> CO & TPR
- Long-term: kidney & thirst responses to regulate
total blood volume -> CO
What are baroreceptors and where are they located?
Short-term: autonomic nervous system to heart,
veins, & arterioles as well as hormones à CO & TPR
- Long-term: kidney & thirst responses to regulate
total blood volume à CO
How does Baroreceptors reflex regulates short-term responses in MAP
-Baroreceptors fire action potentials in response to
pressure in these arteries
– Impulses are delivered via afferent neurons to the
cardiovascular control centre in medulla of brain
stem, where information is integrated
– Sympathetic & parasympathetic outflow via efferent
neurons are adjusted
– Heart & blood vessels change their status to restore
MAP
Describe the journey where changes in blood pressure occur
–
What are the 2 long-term regulation of MAP?
Left atrial volume receptors and Hypothalamic osmorecepters
What are left atrial volume receptors?
Left atrial volume receptors: detect a profound fall in
blood volume/pressure. Stimulates hypothalamus to
release ADH from posterior pituitary -> targets kidneys to
reabsorb water (↑ blood volume) & arterioles to cause
vasoconstriction (↑ TPR)
What are hypothalamic osmoreceptrs?
Hypothalamic osmoreceptors: detect a rise is ECF
concentration (e.g. dehydration) à stimulates thirst
responses (↑ fluid intake, ↑ blood volume)
What happens in the cardiovascular system under stress (exercise)
Marked changes occur in anticipation & at
onset of exercise:
• CO ↑ ~3-5-fold with moderate to heavy
exercise
• CO is re-distributed compared to rest:
- Skeletal muscle, cardiac muscle & skin receive a ↑ proportion
- Other organs receive ↓ blood flow, but brain is maintained
• TPR reduced due to widespread vasodilation in skeletal muscle
• MAP modestly increased
Hypertension? p1
Hypertension > 140/90 mmHg
• Two broad types:
- Secondary: known cause &
accounts for 10% of cases, e.g.
kidney disease
- Primary/Essential: unknown cause, accounts
for 90% of cases, e.g. genetic, exacerbated by
environmental factors
• Vicious cycle: damages vessel walls,
atherosclerosis - increased TPR - further
elevates BP
HypERtension? p2
Baroreceptors do not return blood pressure back to
normal levels à new set-point?
• Increased workload on heart as it is now
pumping against an increased pressure
Complications:
- Left ventricular hypertrophy -> systolic heart
failure
- Stroke (rupture of cerebral vessels)
- Myocardial infarction (rupture of coronary
vessels)
- Kidney failure
- Vision loss
Hypotension
heart
• Orthostatic (postural) hypotension: transient inadequacy in
sympathetic activity
– Lying to standing à blood pools in lower leg veins -
reduced venous return - reduced SV, CO & MAP -
reduced baroreceptor response à dizziness or fainting
• Circulatory shock: extremely low blood pressure such that
blood flow to tissues is compromised. Causes: hypovolemic
shock, cardiogenic shock, vasogenic shock, & neurogenic
shock
