Cardiovascular L10: Regulation of blood pressure cont. & blood composition Flashcards
What are the 3 main purposes of MAP when driving blood into tissue?
- MAP (the driving pressure head)
- resistance of local arterioles (which overrides sympathetic effect) (smooth muscles around- can dilate or constrict- determine how much blood gets to the organ)
- vascularisation/open capillaries (skeletal muscle- no smooth muscle but have sphincters at rest = 10% are open When blood isn’t required= tighten sphincter )
What are 5 factors that can detect and/or influence MAP?
- Baroreceptors (from horizontal to vertical (supine –> standing)) in the aortic arch &carotid sinus sensitive to pressure –> short-term (regulation of BP)
- Left atrial volume receptors &hypothalamic osmoreceptors –> long-term
- Chemoreceptors in carotid & aortic arteries sensitive to low O2 & high H+ –> short-term
- Cerebral cortex-hypothalamic pathway sensitive to behaviour & emotion, which influence MAP
- Hypothalamus sensitive to body temperature, which affects cutaneous arterioles & overrides regulation of MAP
Resistance in arterioles 1 and 2 _____ (increases/decreases) while CO is unchanged?
increases
What happens to flow through vessels 1 and 2?
Decreases (higher resistance)
What happens to MAP?
Increases (blood has to go somewhere)
What happens to flow through vessels 3 and 4?
Increases (blood needs to go somewhere)
Baroreceptor reflex compensates within seconds – what steps are involved in this response?
Describe the reflex arc- when increase in MAP
(individual steps- start corotid and aortic sinuses) systems (parasympathetic and sympathetic) and structures it innervates
What happens to the hydrostatic/ultrafiltration pressure in the capillaries downstream of arterioles 1 & 2?
related to bulkflow
decreased volume
decreased BP
decreased hydrostatic/ultrafiltration pressure in capillaries downstream of arterioles 1 and 2
Less volume = less hydrostatic pressure
Left atrial volume receptors & hypothalamic osmoreceptors regulate _______ responses in MAP
long-term changing how much volume there is
Exracellular fluid (ECF) = plasma (20%) and interstitial space (80%)
regulating ECF = regulating plasma
(The cardiovascular system under stress: exercise- physiological). What are 3 Marked changes occur in anticipation & at the onset of exercise?
- CO increases 2.5-fold with moderate exercise. And CO is redistributed compared to rest:
- skeletal muscle, cardiac muscle & skin (help with losing heat) receive a greater proportion
- other organs receive less blood flow, but brain is maintained
- TPR reduced due to widespread vasodilation in skeletal muscle
- MAP modestly increase
How does MAP increase in exercise? (if TPR decreased)
cardiac output increases = increased HR and stroke volume
MAP = TPR x cardiac output
(The cardiovascular system under stress: hypertension- pathological). What is the blood pressure?
> 140/90mmHg
What are the 2 broad types of hypertension?
- Primary/essential
- Secondary
What is the primary/essential broad type of hypertension?
unknown cause, accounts for 90% of cases, e.g. genetic, exacerbated by environmental factors
What is the secondary broad type of hypertension?
known cause & accounts for 10% of cases, e.g. kidney disease
Why is hypertension a viscious cycle?
damages vessel walls, atherosclerosis –> increased TPR (plaque built up = increase resistance = increases MAP)–> further elevates BP
In hypertension, baroreceptors ____ (do/don’t) return blood pressure back to normal levels –> new set-point?
do not
In hypertension, since baroreceptors don’t return blood pressure back to normal levels, there is an increased workload on heart as it is now pumping against an increased TPR. What are 5 complications?
- Left ventricular hypertrophy –> systolic heart failure
- Stroke (rupture of cerebral vessels)
- Myocardial infarction (rupture of coronary vessels) (heart attack)
- Kidney failure (glomerulus is being damaged too)
- Vision loss
What happens in hypotension (pathological stress)?
Low blood volume for given vascular capacity or weakened heart (not able to inject blood into the blood)
What is orthostatic (postural) hypotension? What does that mean?
transient inadequacy in sympathetic activity Lying to standing –> blood pools in lower leg veins –> reduced venous return –> reduced SV, CO & MAP –> reduced baroreceptor response –> dizziness or fainting
What is circulatory shock (hypotension)?
extremely low blood pressure such that blood flow to tissues is compromised.
Causes: hypovolemic shock, cardiogenic shock, vasogenic shock, & neurogenic shock
What are 3 features in the composition of blood?
- Blood travels within blood vessels to transport materials to cells &away from them
- Blood is a liquid containing plasma & suspended cellular elements
- Erythrocytes (red blood cells)
- Leukocytes (white blood cells)
- Platelets (thrombocytes)
- It makes up ~8% of our body weight
- 5L in women
- 5.5L in men
Blood travels within ______ to transport materials to cells & away from them
blood vessels
Blood is a liquid containing plasma & suspended cellular elements. What are the 3 major elements?
Erythrocytes (red blood cells) – Leukocytes (white blood cells) – Platelets (thrombocytes)
