CVS Control Flashcards
What is normal systolic blood pressure?
120mmhg (contaction)
What is normal diastolic blood pressure?
80mmhg (relaxation)
How is pulse pressure calculated?
systolic BP - diastolic BP
How is the mean atrial pressure calculated?
diastolic BP + 1/3 pulse pressure
CO x TPR
What is the TPR?
total peripheral resistance/ systemic vascular resistance
the resistance encountered by blood flow as it passes through systemic circulation
What is blood pressure?
The force of circulating blood on the walls of the arteries
How does the cardiac output affect blood pressure?
the higher the cardiac output, the higher the volume of blood in the vessels. Therefore, this increases the pressure in the vessels.
How can peripheral resistance affect blood pressure?
Blood pressure is increased when there is an increase in resistance because the heart must pump harder to maintain blood flow through the constricted blood vessels.
What is MAP (mean atrial pressure)?
the average arterial pressure throughout one cardiac cycle, systole, and diastole.
When is blood pressure highest and lowest?
greatest at waking, lowest at sleeping
What device is blood pressure measured by?
sphygmomanometer
How are korotkoff sounds generated?
Korotkoff sounds are generated when a blood pressure cuff changes the flow of blood through the artery.
What are the rapid regulation mechanisms of BP?
hormones
nerves
What is the long term regulation mechanism of BP?
blood volume
Where does the pressure gradient exists and when it is highest?
exists from arterial to venous system
highest at contraction of left ventricle that causes blood to enter aorta
What are baroreceptors?
mechanoreceptors that measure the degree of stretch in blood vessel walls
What are the primary arteries supplying the head and neck?
carotid
Where are the baroreceptors most abundant?
carotid sinus, aortic arch
Where is the carotid sinus?
at the bifurcation of the common carotid artery, which is found at the level of the thyroid cartilage
What nerve supplies the baroreceptors on the carotid sinus?
nerve of Hering (a branch of the glossopharyngeal nerve)
Where is the aortic arch?
under the carotid sinus as it lies on the peak of the ascending aorta
What nerve supplies the baroreceptors on the aortic arch?
aortic nerve (branch of the vagus nerve)
Why are carotid sinus baroreceptors more important?
they are more sensitive to changes in blood pressure and have a lower threshold pressure
Where is the glossopharyngeal nerve located?
medulla oblongata
Describe the action of baroreceptor firing when BP decreases
Baroreceptors detect a decrease in arterial pressure
Reduced Action Potential firing from baroreceptors
Stimulation travels along afferent neurons
Reaches Medullary Cardiovascular Center (located in Medulla Oblongata)
Increased stimulation of Sympathetic neurons to heart/arterioles/veins
Decreased stimulation of Parasympathetic neurons (Vagus Nerve) to heart
Describe the action of baroreceptor firing when BP increases
Baroreceptors detect an increase in arterial pressure
Increased Action Potential firing from baroreceptors
Stimulation travels along afferent neurons
Reaches Medullary Cardiovascular Center (located in Medulla Oblongata)
Decreased stimulation of Sympathetic neurons to heart/arterioles/veins
Increased stimulation of Parasympathetic neurons to heart/arterioles/veins
What is the valsalva manoeuvre?
breathing method to exhale when mouth and nose are closed
attempting to expire with a closed glottis
Describe what happens during the valsalva manoeuvre
Increased intrathoracic pressures causes increase in BP due to sympathetic activation
Decreased venous return causes a fall in CO and MAP
Activation of sympathetic system via baroreceptors
What happens when the glottis is reopened?
Intrathoracic pressure falls, BP falls initially
Venous return is rapidly restored, EDV & CO increase, raising BP
Increased BP is sensed by baroreceptors results in reflex bradycardia (slowing of HR)
What happens when blood pressure is elevated for long periods of time (>15 mins)?
the threshold for baroreceptor activity is raised to a higher value
How can baroreceptor sensitivity be reset?
During exercise – Maintains Cardiac Output as heart rate does not fall in response to increase in BP accompanying exercise
Hypertension – aids buffering of acute fluctuations in BP at new higher BP level
What influences blood volume?
venous pressure
venous return
end diastolic volume
stroke volume
cardiac output
What does an increased blood volume increase?
arterial pressure
What are arterioles?
small diameter blood vessels
What nervous system + receptors cause constriction in arterioles?
sympathetic
alpha 1 noradrenaline adrenergic receptors
What nervous system + receptors cause dilation in arterioles?
sympathetic beta 2 receptors
What are the values in which hypertension is diagnosed?
140 systolic, 90 diastolic
What are environmental factors that increase risk of hypertension?
Age
Cigarette smoking
High salt intake
Lack of exercise
Being overweight
Regularly drinking large amounts of alcohol
Stress
Genetic predisposition
What are health conditions that increase risk of hypertension?
Kidney conditions
(Chronic Kidney Disease (CKD)
Narrowing of arteries that supply blood to kidneys / Renal hypertension
Long – term kidney infections
Glomerulonephritis – damage to glomeruli filters in the kidney)
Diabetes
Obstructive sleep apnoea
Hormone problems – e.g. under/over active thyroid
What are drugs that increase risk of hypertension?
Contraceptive pill
Non-steroidal anti-inflammatory drugs (NSAIDS)
Recreational drugs (e.g. cocaine and amphetamines)
What are the systemic consequences of prolonged hypertension?
Aneurysms in cerebral arteries
Left Ventricular Hypertrophy (LVH)
Thickening of arteries
Atherosclerosis deterioration
What could the consequences of prolonged hypertension cause?
Renal Disease
Development of heart failure due to myocardial adaptation to compensate for LVH
Malignant Hypertension – Severely high BP
Angina or Myocardial Infarction (Cardiac Ischaemia)
Stroke
What are the considerations in dentistry for patients with high BP?
Many anti – hypertensive drugs have interactions with local anaesthetics and analgesics
May lead to local anaesthetic toxicity
Dental treatment is stressful for many patients and any increase in BP may lead to acute complications, e.g. Myocardial Infarction or Stroke
Thus, dental patients with CV Disease have associated higher risk of complications due to release of endogenous catecholamines due to pain/stress
What values indicate hypotension?
90 systolic, 60 diastolic
What is postural hypotension?
Abnormal drop in blood pressure when individual stands up after sitting/lying down
Where is postural (orthostatic hypotension) most common?
More common in older people and those with certain underlying conditions that affect (Sympathetic or Parasympathetic nervous system)
Parkinson’s disease or Diabetes
dehydration or certain medicines
When measuring blood pressure what is the tapping sound?
systolic BP
When measuring blood pressure what is the quiet sound?
diastolic BP
What happened to systolic pressure from pre tilt to during tilt?
stayed the same
What happened to diastolic pressure from pre tilt to during tilt?
increased
(sympathetic system activated)
What happened to pulse pressure from pre tilt to during tilt?
decreased
What is hypovolemia?
reduction in circulating blood volume
What happens in hypovolemia?
arterial BP drops because the venous return is reduced causing the stroke volume to decrease
What happens in postural hypotension?
transient fall in blood pressure when they stand up after a period of lying down
Why does postural hypotension happen?
pressure in the blood vessels below the heart is increased
increase in BP will descend the walls of the blood vessels
veins distend more than arteries
this distention increases the amount of blood in the veins and the venous return is consequently decreased (venous pooling)
Why does the systolic BP stay the same during the experiment?
systolic pressure reflects the force exerted by the heart to pump blood out to the body, while the diastolic pressure reflects the pressure in the arteries when the heart is at rest between beats.
