M103 T3 L2 Flashcards
Where in the body is bp taken from?
from the brachial artery in the upper arm area
What is one kPa equal to in Newtons per square metre?
1000 N/m2
What is 1 torr proportional to?
1mm of mercury in height
What are the standard measurements of blood pressure?
120/75 mmHg
where 120 is systolic, 75 is diastolic
How does blood travel from the intestines to the liver when in the hepatic portal system?
blood leaves via the capillary beds in the walls of the gut
pass through the hepatic portal vein
reach the capillary beds in the liver
Which three factors can result in an increase of bp and which organs are responsible for their regulation?
cardiac output - heart
blood volume - kidney
peripheral resistance - blood vessels
How long does a single heart beat course last?
approx 1 sec
What happens to blood pressure during diastole and systole?
Diastole - heart relaxes - pressure decreases
Systole - heart suddently contracts - pressure sharply increases, then pressure slowly decreases as heart relaxes and aortic valve closes
What is the equaiton for pulse pressure?
Pulse Pressure = Systolic pressure - Diastolic pressure
How do you calculate the mean pressure from an arterial pressure graph?
it is 1/3 of the way up between the diastolic and the systolic pressure
How is the RR interval calculated?
60 / heart rate
What is the equation for cardiac output?
Cardiac output = Heart rate x stroke volume
What is the effect of atrial systole on ventricular blood volume capacity?
20-25% of the total that fills the ventricles
What is the equation for Stroke Volume?
Stroke volume = End Diastolic volume - End systolic volume
What is the equation for Ejection Volume?
Ejection volume = Stroke volume / End diastolic volume
What is the equation for Conductance?
g = 1 / R
What is the relationship between blood vessel radius and blood flow?
as the radius gets larger, the flow increases by x^4
What physical factors affect blood flow? (Rich Penguins Videotaped Lizards)
Blood vessel radius
Pressure
Viscosity
Length
What biological factors have an impact on blood vessel diameter?
Central regulation - the CNS
Local regulation of pressure
Immune system
Haemostasis
How does exercise affect cardiac output and systolic / diastolic pressure?
Cardiac output increases by four fold
Systolic increases, diastolic decreases
What happens when you stand up after a while?
all the blood that had been sitting around the backside area suddenly slides down to the legs, resulting in a huge pooling for a second or two of blood that will be in the lower extremity
Getting that blood out of the lower extremity and back to the rest of the body requires an increase in the heart’s work as well as some kind of exercise / movement to trigger the heart pump
What are the effects of standing?
peripheral vasoconstriction
vastly increased heart rate
diastolic pressure drops dramatically and systolic pressure is really low
Vasoconstriction occurs so that both pressures get back to normal
What are the overall bp changes from standing?
Diastolic pressure increases, systolic stays the same
What types of control are there for systemic blood pressure?
Local - nitrous oxide
Neurological - ANS, Sympathetic, Noradrenaline
Humoral (renal, pituitary, adrenal) - majorly the kidney - central to bp regulation
What are the effects of the sympathetic NS on blood vessels?
vasoconstriction
increased heart rate, bp, PR and heart beat strength
What are the effects of the vagal NS on blood vessels?
slows down the heart, more relaxed
Where are baroreceptors located?
in the transverse aortic arch and the carotid sinuses of the L & R internal carotid arteries
How does the carotid artery send its messages to the brain?
Cranial nerve no.9, the glossopharyngeal nerve
Where are chemoreceptors located?
in the carotid and aortic bodies
What are the factors affecting preload when increased?
Atrial contractility
Aortic pressure
Central venous pressure
Decrease in heart rate (longer period between each beat, more time for ventricle to fill up)
What are the factors that increase preload?
back pressure from the aorta or the pulmonary arteries
when the exit valves don’t fully open
How does the thoracic pump work?
during inspiration, blood from below towards the right atrium is pulled up IOT refill the heart
on inspiration, the chest cavity increases in size so intrathroacic pressure becomes more -ve
Part of this negative pressure is used to pull air from outside of body into lungs
It also pulls blood from elsewhere in body to the thorax
Meanwhile abdominal pressure is positive due to compression of viscera by the diaphragm
The negative and positive pressures lead to a pressure gradient which drives the blood towards the heart
What terms are associated with the vasculature of the lungs?
high capillary density
low vascular resistance
What is the difference in how the lungs (pulmonary circulation) reacts to low/high O2, Co2 and pH compared to in the systemic system?
the effects are opposite in the different environments
usual muscle, low o2 = vasodilation to send more o2 there
in lungs, low O2, the lungs can’t oxygenate the blood so the arterioles constrict
If CO2 or H+ are high, also leads to vasoconstriction
How do the lungs act as a blood reservoir?
has parallel tissues - low pressure system, very easy for blood to flow so they hold a lot of blood in them (9%)
How do the lungs control bp?
Through endocrine control by producing ACE
How do the lungs act as a filter?
often small embolisms will get caught in the capillaries of the lungs - removes these for the rest of the body
What is oxygen demand for coronary circulation like?
high o2 demand - so it receives an inordinate proportion of blood given its weight
Which gets oxygenated blood first, the aorta or the coronary arteries?
the coronary arteries
What is primary hypertension caused by?
idiopathic - most cases
a mismatch between blood volume and circulatory capacity
hormones - partial reason
NTS controls of bp constriction - potential reason
What can hypertension be secondary to (linked to)?
kidney diseases
What can chronic hypertension lead to?
aneurysm / stroke / MI
Cardiac Hypertrophy
Kidney failure, Heart failure
What can standing for a long period of time result in?
low bp due to low venous return - blood pools in the legs and doesn’t return to heart
can lead to dizziness or syncopy
What are the causes of orthostatic hypotension? (HAD)
hypovolaemia, age or drugs
What age group is orthostatic hypotension common in?
the elderly
What are the compensatory mechanisms (symptoms) for cardiogenic shock?
tachycardia and tachypnoea
What negative effects will cardiogenic shock lead to?
low urine output due to insufficient kidney activity
hypotension - could lead to confusion or syncopy
acidosis
What does the letter ‘nu’ represent?
blood viscosity
How do mmHg measurements works?
the amount of pressure that would drive mercury up against gravity
What is the average stroke volume at rest?
70ml
What is the average cardiac output?
avg 4.9L/min
What is the normal diastolic volume?
120ml
What is the normal ejection volume?
between 55 - 70% of the output of the filling of the heart
What activities do neurons in the medullary centers control?
heart rate, respiration, blood vessel diameter, coughing, swallowing, and vomiting
What two areas does the glossopharyngeal nerve carry signals between?
the carotid artery and the brain
From where is bp controlled?
NTS, in the medulla
Where is ACE produced?
in the lungs
What is a benefit of blood travelling via the capillary beds in the liver when in the hepatic portal system?
bc it allows the liver to come into contact with the nutrients / toxins in the blood before they are distributed across the body
When does most of the flow in the heart occur?
mostly during diastole
when in diastole, blood vessels open up and take blood from aorta
when the heart is in systole, all blood vessels being squeezed
