cardiovascular 6-8 Flashcards
Why is arterial blood pressure important?
- to provide a driving force
- to ensure effective tissue perfusion
- to keep vessels open
For which tissues is blood pressure critical and how?
Hint - the obvious and then the blood-cleaner
- brain (if MAP < 60 mmHg, you become unconscious)
- kidneys
What value does blood pressure progressively reach once it reaches the RA?
- falls to 0 mmHg
What is the formula for cardiac output?
cardiac output (L min-1) = heart rate x stroke volume
What does the distribution of cardiac output into the circulatory system depend on?
the pressure difference and resistance to blood flow in vessels
What is blood pressure?
the pressure blood exerts against a wall of the vessel/chamber
How is BP expressed?
systolic/diastolic i.e. 120/80
Where does blood flow from?
Hint - same direction as gases and water
high to low pressure
What is the formula for blood flow?
flow ∝ pressure difference/resistance
If there is a greater pressure difference what does it mean for blood flow?
greater blood flow
Describe blood pressure in terms of how constant it is.
- is pulsatile (varies)
- and rises and falls with each heartbeat
Which 3 factors does vascular resistance (R) depend on?
Hint - BLB
- lumen size – smaller diameter means greater resistance to flow
- blood viscosity – thicker blood (i.e. by polycythaemia) can increase MBP
- blood vessel length – longer vessels require higher resistance
What does systemic vascular resistance (SVR) oppose and what does it depend on?
- opposes blood flow
- depends on smaller arterioles
What is the formula for mean blood pressure?
Hint - MCP
Mean Blood Pressure = Cardiac Output x Peripheral Resistance
With blood pressure:
a) what happens to CO if MBP decreases?
b) what happens to PR if MBP increases?
c) what must CO and PR do?
a) decrease in MBP means CO must decrease
b) increase in MBP means PR must increase
c) CO and PR must balance
What is venous return?
Hint - Venous return chamber
pressure generated by LV so blood can flow back to heart
What is the cardiac centre and what does it monitor?
- cardio-acceleratory centre → increases HR via sympathetic innervation of SAN/AVN
- cardio-inhibitory centre which slows heart
- both monitor changes in BP, PO₂ and pH via baroreceptors and chemoreceptors
Where is the cardiac centre located and what is its input?
- location → medulla oblongata
- input → nerve impulses from sensory receptors + higher brain centres
What is the vasomotor centre?
- large group of cells → vasoconstriction
- small group of cells → vasodilation
Where is the vasomotor centre located and what is its input?
- location → (also) medulla oblongata
- input → increased frequency of nerve impulses
Where are baroreceptors located?
Hint - all heart WAC
in carotid sinus, aortic sinus and wall of right atrium
Where are aortic baroreceptors located and what do they monitor?
(Hint - both parts to do with main aortic vessel)
- ascending aorta
- monitor stretch within aorta (associated with adequate blood supply to systemic system)
What do carotid baroreceptors monitor and what is this associated with?
(Hint - carotid + it takes minutes)
- blood pressure in carotid arteries
- associated with adequate blood supply to brain
Which receptors detect increased blood pressure and what does this initiate?
(Hint - all about feedback to slow HR + BP)
- baroreceptors
- initiate regulatory feedback signals to CV centre promoting:
• inhibition of cardio acceleratory centre and stimulation of cardio inhibitory system
• inhibition of vasomotor cells associated w/ vasoconstriction
What effect does parasympathetic stimulus have on blood pressure on a molecular level?
(Hint - NT and the effect it has at end of ECG)
- releases Ach
- extends repolarization
What effect does sympathetic stimulus have on blood pressure on a molecular level?
(Hint - a different NT and effect on ECG)
- releases NA
- shortens repolarization
Explain the Renin-Angiotensin-Aldosterone System including the effects of outside hormones.
- low BP → renin secreted by kidneys
- angiotensinogen (renin) → angiotensin I (ACE, or angiotensin-converting enzyme) → angiotensin II
- angiotensin II:
• vasoconstriction arterioles – increase peripheral resistance
• increases aldosterone secretion - blood volume increases by renal reabsorption of Na⁺ + H₂O - hormones like E and NA increase HR by affecting SAN
- epinephrine also affects contraction of cells
(see notes for diagram)
How can blood flow be modified?
Hint - mechanisms of what by which parts of the vessel?
mechanisms of localised vasoconstriction + vasodilation of precapillary sphincter muscles
Name some vasodilators.
Hint - three Os, breastfeeding hormone, what is taken for allergies
O₂, CO₂, NO, histamine, lactate
Name some vasoconstrictors.
Hint - ETs both released by similar-sounding cells
- thromboxains → released by platelets in a wound
- endothelins → released by damaged endothelial cells
Name the 2 regions of the CV centre (functions already discussed).
- cardiac centre (cardio acceleratory + cardioinhibitory centres which monitor changes in BP, PO₂, pH → baroreceptors + chemoreceptors)
- vasomotor centre (large + small group of cells associated with vasoconstriction and vasodilation respectively)
What is vasoconstriction achieved by and mediated with?
Hint - which CNS division + which receptors in which cell?
- sympathetic system
- α-1 adrenoreceptors located in smooth muscle membranes
What is vasodilation mediated via?
Hint - increasing dissertation vasodilator within the main type of muscle of body
via increasing NO within SM
State the baroreceptor reflex.
Hint - about decreasing BP
- increased BP is detected by baroreceptors which initiate regulatory feedback signals to CV centre promoting:
• inhibition of cardioacceleratory centre and stimulation of cardioinhibitory system
• inhibition of vasomotor cells associated with vasoconstriction
Where are chemoreceptors which mediate reflexes located?
Hint - 2 types of bodies and then an oblong shape
- carotid bodies
- aortic bodies
- medulla oblongata
What are chemoreceptor reflexes sensitive to?
changes in blood O₂, CO₂ and pH
How are vasodilation and vasoconstriction induced by chemoreceptor reflexes?
(Hint - 3 main increases/decreases)
- vasoconstriction by:
• low blood O₂ (vasodilation by high O₂)
• low pH
• high CO₂
Which hormones are involved in hormonal (endocrine) control mechanism?
(Hint - AAAVE - last is a kidney hormone)
- adrenaline
- angiotensin
- atrial natriuretic hormone (ANP)
- vasopressin (ADH)
- erythropoietin
What effect does adrenaline have on the CV system?
- activates cardio acceleratory centre
- increasing sympathetic stimulation of heart via NA
What effects does the angiotensin-aldosterone system have on the CV system?
• decreased BP induces juxtaglomerular apparatus to secrete renin
• whole process of (renin + ACE) converting angiotensinogen to angiotensin I
• angiotensin II:
- vasoconstriction
- stimulates aldosterone secretion
- kindles thirst
- increases salt appetite + ADH secretion
What is the reason for vasopressin (ADH) secretion and what effects does it have on the CV system?
(Hint - causes a move on blood vessels + urine volume modification)
- caused by decreased BP
- causes vasoconstriction + decreased urine production
Where is atrial natriuretic hormone released from and what effect does have on the CV system?
(Hint - clue-is-in-the-name cells + opposite effect of ADH)
- released from atrial cells in response to increased atrial BP
- causes increased urine production
What is the fluid shift (hormonal) mechanism and what does this result in?
(Hint - movement of fluid between cells + opposite effect on BP)
- BP increases fluid from blood vessels into interstitial space
- results in decreased BP
What is the stress relaxation response and what does this result in?
- as BP decreases in vessels, reduction in force applied to vessel endothelium
- SM cells → respond by slowly contracting
How many long-term and short-term parts are three in the cardiovascular response to wounds/haemorrhaging?
(Hint - long response for the road)
- two short-term responses
- one long-term response
What are the short-term cardiovascular responses to wounds/haemorrhaging?
(Hint - BP sinuses and widening vessels, additional fight-or-flight)
- decreased BP detected by baroreceptors in aortic + carotid sinuses → promotes vasoconstriction
- stress-related responses further stimulate SNS
What is the long-term cardiovascular response to wounds/haemorrhaging?
(Hint - more urine hormone, kidney/acne hormone, raas)
increasing:
- activation of renin angiotensin system
- ADH system
- secretion of erythropoietin
What can circulatory shock arise because of?
Hint - DDEE → blood escape, cardiac harm, cardiac force, too much vessel widening
- drop in BP due to a major haemorrhage
- damage to heart
- external pressure on heart
- extensive peripheral vasodilation
State the symptoms of circulatory shock.
Hint - CIPHAC
- confusion/disorientation
- increased HR and weak pulse
- pale cool skin
- hypotension
- acidosis
- cessation of urination
What can failure to stimulate sympathetic innervation to a patient in circulatory shock cause?
- BP to decrease further → irreversible shock
What is oxygen consumption (VO2)?
rate at which oxygen is delivered to tissues + extracted from blood by tissues
What happens to oxygen consumption (VO2) during exercise?
increases to a maximal oxygen consumption
Which changes in cardiac output occur during exercise?
Hint - anticipatory, abdomen + veins, VEDV
- anticipatory increase in CO by SNS
- decreased blood flow to abdominal arteries temporarily increasing venous return → increased ventricular EDV (RV contracts more forcefully during systole)
How is respiration controlled and how can it be influenced?
Hint - meddys, what they do, how this can be influenced
- controlled by medullary neurones which set basic rhythm of respiration
- influenced by inputs from other parts of brain + peripheral sensory receptors
Where is the respiratory centre located and which 2 regions does it consist of?
- located in medulla oblongata with two regions:
1. inspiratory centre
2. expiratory centre
Describe the inspiratory centre.
- two dorsally-situated regions of medulla
- neurones within centres show spontaneous rhythmicity and cyclic activity
- action potentials derived from cells → along intercostal + phrenic nerves → supply inspiratory muscles
Describe the expiratory centre.
- two ventrally-situated groups of neurones
- mostly inactive but during heavy breathing they send action potentials to expiratory muscles
Apart from the inspiratory and expiratory centre, which other 2 brain centres are associated w/ respiratory control and what are their effects?
- apneustic centre: scattered neurones in the pons send action potentials to inspiratory centre
- pneumotaxic centre: neurone within superior pons inhibitory effect on inspiratory and apneustic centre
Which steady-state effects does exercise have on the CV system?
(Hint - resp increase + RR)
- respiration starts to increase linearly with O₂ uptake
- respiratory rate is measured as ventilatory equivalent for oxygen (VE/VO₂)
Which non-steady-state effects does exercise have on the CV system?
(Hint - disproportionate O₂, disproportionate VR, lactate + sodium bicarb)
- RR increases disproportionately to oxygen uptake
- disproportionate increase in ventilation rate at ventilatory threshold
- accumulation of blood lactate + increased lactic acid buffered with sodium bicarbonate
- lactic acid + NaHCO₃ → Na-lactate + H₂CO₃
State 4 cardiovascular adaptive changes endurance training can result in.
changes in:
- oxygen consumption
- HR and SV
- arteriovenous differences
- BP and blood flow
