Lecture 8 Flashcards
Give two reasons why blood pressure is important?
- Blood flow to a given tissue must match the metabolic rate of that tissue.
- Without this adequate blood supply of O2 and nutrients, tissue will start to undergo necrosis.
What is hemodynamics, the physical principles of blood flow, based mainly on?
Pressure and resistance
What does vascular resistance, or total peripheral resistance, depend on?
- Size of the vessel lumen
- Length of the blood vessel
- Blood viscosity
What is the force (or hydrostatic pressure) that blood exerts against a blood vessel wall?
blood pressure
What does blood pressure variation depend on?
- the system; systemic or pulmonary
- the distance from the ventricles of the heart
- whether the heart is in systole, contraction, or diastole, relaxation
What is usually measured in clinical circumstances?
Arterial blood pressure
What is pressure exerted by a liquid in response to an applied force?
hydrostatic force
What results in high blood pressure?
Cardiac output from both sides of the heart is equal but total resistance of the systemic circuit is much greater
What do capillaries enable?
Redistribution of blood to the areas of greatest need
What is the peak arterial blood pressure attained during ventricular systole?
systolic pressure
What is the minimum arterial pressure during ventricular diastole?
diastolic pressure
What is the difference of pressure between systolic and diastolic pressure?
pulse pressure
What is a pulse?
Rhythmic pressure oscillation that accompanies each heart beat
What is systolic pressure mainly affected by?
Ejection velocity, EV
Stroke volume, SV
What is diastolic pressure mainly affected by?
Total peripheral resistance
Mostly arteriole resistance
Blood flow from arterial to venous sides
(Mean arterial pressure) MAP=?
diastolic blood pressure + 1/3 of (systolic BP-diastolic BP)
Where is the arterial blood pressure typically measured at?
brachial artery with the art at heart level
What is used to measure arterial blood pressure?
sphygmomanometer and a stethoscope
What are the four steps in measuring arterial BP?
- Inflate cuff to a pressure greater than the person’s systolic BP to prevent any blood flow in the artery
- Start to slowly deflate the cuff
- As the cuff deflates, a spurt of blood flows through the artery and a sound is heard = systolic pressure
- Once the sound becomes softer/muffled = diastolic pressure
What are the associated sounds in arterial BP measurements called?
Korotkoff sounds
What is the loud sound caused by in measuring arterial BP?
turbulent blood flow
What indicates that laminar blood flow has resumed when measuring arterial blood pressure?
The silence which resumes
What can account for different values of diastolic pressure between UK and US stats?
The UK diastolic pressure is indicated by the muffling sound while the US uses the silence
Which location is the most accurate place to measure arterial BP?
forearm
Which makes a larger sound; systolic or diastolic pressure? And why?
systolic (Phase I)
systolic pressure is larger than the cuff
What phases indicate diastolic pressure?
Phase IV or silence
Name three factors that can disturb homeostasis?
- physical stress
- chemical changes
- increased tissue activity
In response to the factors that disturb homeostasis what leads to local decrease in resistance and increase in blood flow?
Inadequate local BP and blood flow
When decrease in resistance and increase in blood flow proves ineffective, signals are received by which two areas?
- Baroreceptors (in distensible areas of artery)
2. Kidney
The signals received by the baroreceptors and the endocrine system lead to what?
Baroreceptors: processed by cardiovascular artery and leads to short-term increase in BP by increased cardiac output and peripheral vasoconstriction
Endocrine system: Long-term increase in BP by increasing blood volume
What do baroreceptors detect?
Stretching of blood vessels
What is an example of baroreceptors and where is it located?
Carotid sinus
In the internal carotid artery above the branching of the common carotid into the internal and external carotid arteries
Do baroreceptors contain unmyelinated or myelinated sensory fibers?
both
What are the sensory fibers of the baroreceptors integrated with?
elastic layers
Do baroreceptors use graded or action potentials?
Graded
Where is the aortic arch located?
Just above heart
What does the aortic arch have a lot of?
elastic fibers
What are the effectors for baroreceptors?
What do they control?
Cardiac muscle
Vascular smooth muscle
(adjust cardiac output and peripheral resistance)
What center increases sympathetic activity to the heart?
Cardioacceleratory center
What center increases parasympathetic activity to heart?
Cardioinhibitory center
What does the vasomotor center do?
Controls activity of sympathetic neurons that innervate vascular smooth muscle
When do we need short-term regulation of arterial BP?
Orthostasis
What happens during orthostasis? What does orthostasis control?
Cardiovascular centers increase vasomotor tone
Posture
Why do some people faint when waking up too quickly?
BP hasn’t adjusted yet
Temporary lack of blood supply
Laying down: low BP
Standing up: High BP
What are examples of long-term regulation of arterial BP?
Hormonal resistance
Negative feedback loop
Adjusting blood volume
What hormone causes Na retention and K loss at the kidneys?
Aldosterone
What factor stimulates antidiuretic hormone release from the pituitary gland causing vasoconstriction and water conservation in the kidneys?
Angiotensin II
Effect of angiotensin II on BP is at least _ times greater than that of _
four
noradrenaline
What organ releases renin?
kidneys
What organ releases angiotenisogen?
liver
What is a precursor molecule of angiotensin II?
Angiotensin I
What two parts of the brain does angiotensin II stimulate and what does it lead to?
Hypothalamus
-Thirst, drinking, vasoconstriction
Adrenal cortex
- salt and water retention for elevated BP
What are two examples of blood pressure variations in sleep-wake cycle?
Low BP during sleep
High BP during waking
BP is activity dependent. Which is why people with a compromised internal clock can have heart attacks. Where would this often happen?
in the bathroom
_ is a chronic resting BP of over 140/90
hypertension
What can hypertension lead to?
hypertensive stroke constricted blood vessels in the eye atherosclerotic plaque formation ventricular hypertrophy glomerulosclerosis aneurysm
What are two groups of drugs that disrupt the renin-angiotensin-aldosterone system?
Angiotensin converting enzyme (ACE) inhibitors
Angiotensin receptor blocker (ARB)
What is an examole of an ACE inhibitor?
Ramipril
What is an example of an ARB?
Losartan
What reduces blood volume?
thiazide diuretics
What type of antagonist decreases cardiac output?
sympathetic beta-1 adrenoceptor antagonist
What is an example of the antagonist that decreases cardiac output?
metoprolol
What are two types of antagonists that decrease total peripheral resistance via vasodilation? Name one example for each.
Sympathetic alpha-1 adrenoceptor antagonist
- doxazosin
Calcium channel antagonist
- nifedipine
