Extra Cardio PHYS Flashcards
What is isovolumetric contraction.
Ventricular contraction when all valves are closed. This increases ventricular pressure but as the valves are closed the volume remains unchanged.
What is the duration of systole?
Diastole?
0.3s
0.5s
What is end systolic volume?
The volume of blood remaining in the LV following systole
Define preload.
The initial stretching of the cardiac myocytes, or The volume of blood in the ventricles just before contraction (EDV).
Define afterload.
The pressure against which the heart must work to eject blood in systole.
Define contractility.
The inherent strength and vigour of the heart’s contraction during systole.
Define elasticity.
Myocardial ability to recover it’s original shape after systolic stress.
Define compliance.
How easily a chamber of the heart expands when it is filled with blood (C=ΔV/ΔP).
Define diastolic distensibility.
The pressure required to fill the ventricle to the same diastolic volume.
Give the equation for mean arterial pressure.
MAP = DP + 1/3(SP-DP).
(SP - systolic pressure, DP - diastolic pressure).
5
Give the equation for blood pressure.
BP=COxTPR.
What do arterioles respond to?
Blood pressure changes. Local, neural and hormonal factors.
Name 2 local factors that result in vasoconstriction.
Endothelin, internal BP.
Name 5 local factors that result in vasodilation.
Hypoxia, NO, K+ (accumulate from AP), CO2, H+, adenosine.
What neural factors result in vasoconstriction?
Sympathetic nerves that release noradrenaline.
What neural factors result in vasodilation?
NERUAL - Think nervous system
Parasympathetic innervation.
Name 3 hormonal factors that result in vasoconstriction.
Angiotenisn 2, ADH, Adrenaline (binds to alpha-adrenergic receptors in smooth muscle).
Name 2 hormonal factors that result in vasodilation.
Atrial natriuretic peptide, Adrenaline (binds to beta2 receptors).
Myogenic auto-regulation of blood flow: What is the response to an increase in BP?
Increased BP will result in vasoconstriction and so blood flow decreases.
Myogenic auto-regulation of blood flow: What is the response to a decrease in BP?
Decreased BP will result in vasodilation and so blood flow increases.
What is the cause of active hyperaemia?
When blood flow increases due to an increase in metabolic activity.
- Increased metabolic activity = decreased O2 and increased metabolites = arteriolar dilation = increased blood flow.
What is the cause of reactive hyperaemia?
When blood flow increases following occlusion to arterial flow.
Describe excitation-contraction coupling.
Pathway
1. Action potential causes wave of depolarisation across myocardium —> induces a Na+ sodium ion influx relative to the potassium
2. Plateau phase - Ca2+ coming into cells causes more calcium to be released from sarcoplasmic reticulum inside myocytes. -Ca2+ induced Ca2+ released.
3. The Ca2+ bonds to specific proteins Troponin C –> Troponin C changes shape, and sits on tropomyosin. This moves the tropomyosin away from myosin head, so actin myosin bridges can form
(after this, ATP needed to break bridges so myoisn can move along (muscle can relax))
==> ATP also needed to actively transport Ca2++ back to sarcoplasmic reticulum
After depolarisation, Ca2+ is returned to SR. K+ outflow = repolarisation.
What effect does myocardial contraction have on the
A) A-band of a sarcomere?
B) I band?
c) H Zone
a) stays the same
B and C - get shorter
What is the I Band ?
What is the H band?
What is the A band?
I band - region containing only Thin filaments
H band (the region containing only thick filaments)
A band - just the size of the thick myosin filaments
What is the function of troponin C?
Troponin C has a high affinity for Ca2+. TnC drives away TnI and so allows cross bridge formation.
Where are peripheral chemoreceptors found?
What do they respond to?
What connects them to to the brain
Aortic arch and carotid sinus
Monitor changes in pO2 and pCO2, and conc of H+ ions for pH of blood
(but primarily changes in pO2)
Aortic arch = vagus nerve
cartoid sinus - Glossopharyngeal
What changes can the cardiac centre make in terms of vascular control?
has Sympathetic fibres which alter the diameter of blood vessels (vasoconstriction)
And has Cardiac accelerator centre to increase heart rate and contractility (sympathetic)
and has cardiac decelerator centres to lower heart rate (parasympathetic)
To summarise, what is can the sympathetic autonomic nervous system change?
SYMPATHETIC = increasing The Heart rate, heart contractility, and diameter of blood vessels
PARASYMPATHETIC = Decreasing heart rate only
Chemorecpetors - what change would happen when chemoreceptors pick up
low pO2, high pCO2, and acidaemia?
Sympathetic nervous system REDUCES blood vessels diameter, leading to VASOCONSTRICTION and increase TPR
Also would limit blood flow to peripheral organs and give more to heart and brain, cause vasoconstriction in veins for increased EDV, more preload
Leads to increased BP and CO
What does sympathetic activity leading to increased CO and BP achieve?
pushes more blood to the lungs so more CO2 and be breathed out and more O2 can be breathed in? (to lower hypercapernia and raise hypoxia)
Where are central chemoreceptors located? what do they measure
They are in the medulla oblongate
Measure the PCO2 and pH of the CSF
===> the CO2 breakdown into H+ ions
What do central chemoreceptors do?
Arteriolar and venous constriction , which pumps more blood to the brain so BP in brain > than CSF pressure, and more blood goes to brain
What layer of the tri-laminar disc forms the cardiovascular system?
The mesoderm.
What does the TRUNCUS ARTERIOSUS - gives rise to
AORTA, AORTIC ARTERIES moves down and to the right
what does BULBUS CORDIS - gives rise
RIGHT VENTRILE , AND OUTFLOW TRACTS, moves down and to the right
What does PRIMITIVE VENTRICLE -give rise to
the left ventricle
What does PRIMITIVE ATRIUM -give rise to
gives rise to LEFT ATRIA
What does SINUS VENOSUS -give rise to
gives rise to RIGHT ATRIA, VENA CAVA AND CORONARY SINUS (pulmonary vessels
What affect does parasympathetic stimulation have on heart rate?
Decreases heart rate (-ve chronotropic). Cardiac output therefore decreases with parasympathetic stimulation. (CO=HRxSV).