cardio Flashcards
What percentage of blood is found in the systemic system?
84%
What percentage is found in the pulmonary system?
9%
How does an action potential propagate through an atria?
through gap junctions in the intercalated discs of atrial muscle fibres
what is the speed of the first stage of the cardiac action potential?
slow 0.5 m/s
Why does the rate of ejection slow down during ventricular systole?
as the myocytes begin to run out of strength/ ability to shorten in the ventricle
Which blood vessel has the highest compliance?
elastic arteries
therefore lowest elastance
what is another name for elastic arteries?
conducting arteries
What is the size of an elastic artery?
more than 1cm
finger size
What is the function of elastic arteries?
store bolus of blood during ejection
SMOOTHEN OUT the pulsatile flow of blood from the ventricle
push blood out into the arterial tree via Elastic Recoil
What distance after the heart do elastic arteries go for?
first 15 cm
How many sheets of elastic fibres in tunica media can be found in elastic arteries?
up to 50
+ a few smooth muscle fibres
What are the most abundant arteries?
muscular arteries
What is the size of muscular arteries?
pencil –> pin
10mm –> 1 mm
Where are the tunica’s most distinct?
muscular arteries
What is in the tunica externa of muscular arteries?
elastic and collagen fibres
What is in the tunica media of muscular arteries?
smooth muscular 3-40 sheets
connective tissue
elastic fibres
What is located within the tunica interna / intima?
inner elastic lamina (thin sheet of elastic fibres) basement membrane (physical support) endothelium
How many sheets of smooth muscle are in muscular arteries?
3-40 sheets
hence 10mm –> 1mm diameter
What is the function of muscular arteries?
bulk flow
bulk tuning
distributes blood around the body at high pressure
Where is the site of final fine tuning?
arterioles
What is the thickness of arterioles?
100 microns - 10 microns
Besides normal what is the function of arterioles?
to protect capillaries
impact TPR and mabp
How many sheets of smooth muscle are in arterioles?
3-1 of circular smooth muscle
What causes edema?
when the rate of filtration is larger than the rate of reabsoprtion
leads to swollen tissue
lower limbs when standing too long
What are capillaries made out of?
single endothelial cell layer
External BM
NO SM NO CT
What is the function of venules?
site where WBC leave during inflammation and infections- leave to attack pathogen in connective tissue alongside them
WBC (neutrophils) stick to side of vessel due to slow flow
small venules= single layer endothelium and CT (CT + capillary)
large venule= single layer of smooth muscle
What is a small venule made out of?
single layer endothelium + CT
capillary + CT
What is a large venule made out of?
Single layer of Smooth muscle
What is the breakdown of blood in the systemic circuit?
84% in total systemic circuit - 64% in systemic veins and venules (reservoir) 13% in systemic arteries and arterioles 7% systemic capillaries \+ 7% heart 9% pulmonary circulation
What is the compliance of vein walls?
very compliant
What is the structure and function of veins?
similar to muscular arteries but with just a lot less muscle and connective tissue
-venous pump aiding venous return back up to the heart
What does the left artery do and how many branches?
Two branches
supplies front and left of the heart
What does the right artery do and how many branches?
one branch
supplied right and back of the heart
What are anastomes?
coronary artery-to artery junctions
between small penetrating branches of main coronary arteries
What are the artery to artery junctions between small penetrating branches of main coronary arteries?
anastomes
What can ischemia cause?
angina
-due to death of the tissue and pain in breathing
What can cause angina?
ischemia
What can severe angina cause?
death/infarction of LOCAL area of myocardium
What is the advantageous function of anastomes?
they can widen when there is a local ischaemic region, allowing the ischaemic region to recieve blood supply from DISTANT ARTerioles
What happens to distant arterioles when there is angina in the coronary arteries?
anastomes widen and this allows areas with ischaemia due to a diseased coronary artery to receive blood from DISTANT ARTIERIES
What is a thrombosis?
a broken free blood clot
What is a broken free blood clot called?
thrombosis
What do you measure to get blood pressure?
brachial (arm) artery
What is the units for cardiac output?
The amount of blood that is ejected into the aorta per minute
Lmin-1
What is venous return?
the quantity of blood returning to the heart from the vasculature per minute
Lmin-1
What is stroke volume?
the quantity of blood that is pumped into the aorta EACH CONTRACTION
mL/beat
EDV-ESV
What is heart rate?
the number of beats per minute
bpm
Why does the kidney receive such a large portion of cardiac output?
20-25% of CO at rest
1L of blood through kidney alone
allows the filtering of waste and CO2 out of the blood stream to be rapid
What is CO at rest?
75 bpm x 70mL
5.25L
What is CO after exercise?
150 bpm x 130 mL
19.5
What is the relationship between myocardial infarction and cardiac reserve?
decreased cardiac reserve
decreased ability to increase CO upon exercise
demand of tissues increased, but DECREASED ABILITY TO SUPPLY
decreased CO
can lead to heart failure
What is an average person’s cardiac reserve?
4-6x CO at rest
What is a fit person’s cardiac reserve?
7-8x CO at rest
What is the max HR?
180-200 bpm
What is the max SV?
150mL
What is the key word for preload?
STRETCH
stretching myocytes augments/stimulates the AMOUNT OF CROSS BRIDGE FORMATION
increased EDV
What is the key word for contractility?
forcefulness
the forcefullness at which the ventricle squeezes down on the volume of blood
starlings law of the heart
decreased ESV
inotropic agents- positive can increase Ca2+ inflow
What are inotropic agents related too?
contractility
What does a negative inotropic agent do?
K+
decreases HR and decreases contractile force
What must happen with after load?
aortic/arterial blood pressure must be exceeded
What is the intrinsic regulation of the heart?
degree of stretch of the myocardial fibre at the end of diastole
What is the extrinsic regulation of the heart?
autonomic nervous system activity
circulating levels of hormones
What type or regulation is hormone levels?
extrinsic regulation
what type of regulation is the autonomic nervous system?
extrinsic regulation
What type of regulation is the length of cardiac muscle fibres at the end of diastole?
intrinsic regulation
What does the frank starling law of the heart ensure?
prevents damming of the heart
ensures output = input
-the energy of contraction is a function of the initial length of the myocardial fibres (sarcomere length causes force generation)
How do you count EF?
cardiac echoes
What two things determine blood flow?
going –> pressure difference (Gradient)
resistance
What is the equation for BP?
CO x TPR
Does BP ever fall to zero?
No because of the vasculature
What are the three factors affecting resistance?
radius - inverse relationship
blood viscosity - directly proportional relationship
vessel length - directly proportional relationship
What is the law which talks about resistance?
pousille’s law; 8nL/pixr^4
Is oxygen a vasoconstrictor or a vasodilator?
O2 is a vasoCONSTRICTor
Is carbon dioxide a vasodilator or a vasoconstrictor?
vasoDilator
What is an example of a hormonal factor that is a vasoconstrictor?
Angiotensin II
-focus of drug therapy to decrease it’s levels
What are the four factors affecting vascular tone?
sympathetic nerve activity
hormonal factors
metabolites
intrinsic factors (NO)
What is Angiotensin II in relation to the heart?
hormonal factor which affects vascular tone
vaso constrictor
target to reduced angiotensin II levels in high BP patients
What is an intrinsic factor which regulates vascular tone?
Nitrous Oxide
vasoDILATOR
What are the three higher brain centres?
cerebral cortex
limbic system
hypothalamus
What is the function of chemo receptors?
monitors blood acidity
CO2, O2 and H+
What are the two outputs by the sympathetic nervous system?
vasomotor nerves
cardiac accelerator nerves
What is the relationship between cardiopulmonary and arterial baroreceptors?
cardio pulmonary receptors are relatively more sensitive to changes in blood volume
When there is a 1L loss of blood volume it will be primarily sensed be the cardiopulmonary receptors.
But since this is such a significant loss, it will lead to a decent drop in systemic blood PRESSURE which will be sensed by the arterial baroreceptors (hence pressure)
they will work together in a symbiotic relationship
What is feeling faint/light headed an example of?
decreased blood pressure
What is the order of sympathetic nerve and neurotransmitter release to smooth muscle?
cholinergic -> nicotinic receptor (ACh) –> adrenergic –> adrenergic receptor (NE and E) –> smooth muscle, glands, cardiac
What is the order of sympathetic nerve and neurotransmitter release to sweat glands?
cholinergic –> nicotinic receptors (ACh) –> muscarinic –> muscarinic receptors (ACh) –> sweat glands
What is the order of para sympathetic nerve and neurotransmitter release to smooth muscle?
cholinergic –> nicotinic (ACh) –> muscarinic –> muscarinic receptors (ACh) –> smooth muscle, cardiac, glands
What 3x areas of the body does the autonomic nervous system innervate?
smooth
cardiac
glands
What happens after a decrease in blood pressure?
decreased STRETCH of baroreceptors in aortic arch and carotid sinus
–>
decreased firing of baroreceptors in aortic arch and carotid sinus
–>
sensory neurons
–>
cardiovascular centre in the medulla oblongata
–>
increased stimulation/output of sympathetic nerve (NE and E) and decreased stimulation/output of parasympathetic nerve (ACh)
On average what is MABP?
100mmHg