Blood Pressure Flashcards
(29 cards)
Blood pressure
Force exerted by circulating blood on the walls of blood vessels
●Highest in the aorta and reduced as blood flows through other blood vessels
●Often referred to as arterial blood pressure
●Measured using invasive and non-invasive methods
Blood pressure valves
Systolic (mmHg) Diastolic (mmHg) Normal 100-119 60-79 Hypotension < 100 < 60 Prehypertension 120-139 80-89 Hypertension 1.Stage 1 2.Stage 2 ≥140 140-159 ≥ 160 ≥90 90-99 ≥ 100 (Adapted from Starr and McMillan: Circulation-The Heart and Blood Vessels)
Pulse rate
●Pulse pressure= systolic pressure minus diastolic pressure
●It represents the force that the heart generates each time it contracts.
●Mean arterial pressure (MAP) represents average arterial pressure during cardiac cycle
●MAP=diastolic + 1/3 pulse pressure
Peripheral resistance
Resistance of the arteries to blood flow
•As the arteries constrict, the resistance increases, as they dilate, resistance decreases
Autonomic activity: The sympathetic and parasympathetic nervous systems.
The sympathetic nervous system prepares your body for physical and mental activity.
heart beats faster and stronger, Respiration is increased, and inhibits digestion.
The parasympathetic nervous system is responsible for bodily functions when we are at rest: it stimulates digestion, helps with relaxation.
But the sympathetic and parasympathetic nervous systems do not always work in opposite directions; they sometimes complement each other too.
Blood pressure measurements
Measured in mmHg
●Values in healthy adult <120/80 mmHg
●Values lower in children
●Can also be influenced by stress, drugs, exercise, disease etc.
How is blood pressure regulated
The pressure of arterial blood is regulated by blood volume, total peripheral resistance and the cardiac rate
Regulatory mechanism adjust these factors in a negative feedback manner to compensate for deviations
Short term regulation and Long term regulation
Arterial blood pressure cardiac output total peripheral resistance α ×
cardiac rate
stroke volume
vasoconstriction
Blood pressure regulation : baroreceptor reflexes
Baroreceptor Arterial Pressure Control System
Baroreceptors are spray-type nerve endings that lie in the walls of the arteries; they are stimulated when stretched
Baroreceptors are extremely abundant in:
(1) the carotid sinus
(2) the wall of the aortic arch
Bacoreceptor reflex
Signals are transmitted from each carotid sinus through the Hering’s nerve to the Glossopharyngeal nerve and then to the tractus solitarius in the medullary area of the brainstem
Signals from the aortic arch are transmitted through the vagus nerves also into this area of the medulla
After the baroreceptor signals have entered the tractus solitarius of the medulla, secondary signals inhibit the vasoconstrictor center of the medulla and excite the vagal parasympathetic center.
Circulatory reflex initial by bacoreceptor
The net effects are:
(1) vasodilation of the veins and arterioles throughout the peripheral circulatory system and
(2) decreased heart rate and strength of heart contraction. Therefore, excitation of the baroreceptors by high pressure in the arteries reflexly causes the arterial pressure to decrease because of both a decrease in peripheral resistance and a decrease in cardiac output.
• Conversely, low pressure has opposite effects, reflexly causing the pressure to rise back toward normal
Control of arterial pressure by the carotid and aortic chemoreceptors-effect of oxygen lack on arterial pressure
- Similar to the baroreceptor reflex except that chemoreceptors, instead of stretch receptors, initiate the response
- Chemoreceptors are chemo sensitive cells sensitive to oxygen lack, carbon dioxide excess, and hydrogen ion excess
What is carotid or aortic body supplied by
When do the baroreceptor become stimulated
Each carotid or aortic body is supplied with an abundant blood flow through a small nutrient artery
•Whenever the arterial pressure falls below a critical level, the chemoreceptors become stimulated because diminished blood flow causes decreased oxygen, as well as excess buildup of carbon dioxide and hydrogen ions that are not removed by the slowly flowing blood.
What is excited by the signal
The signals transmitted from the chemoreceptors excite the vasomotor center (cardiovascular and respiratory centres), and this elevates the arterial pressure back toward normal.
Lower pressure
- However, this chemoreceptor reflex is not a powerful arterial pressure controller until the arterial pressure falls below 80 mm Hg
- Therefore, it is at the lower pressures that this reflex becomes important to help prevent further decreases in arterial pressure.
Atrial stretch reflexes
Both the atria and the pulmonary arteries have in their walls stretch receptors called low-pressure receptors (Bainbridge reflex)
Renal -body fluid system for arterial pressure control(Long term regulation of blood pressure)
An increase in arterial pressure in the human of only a few mm Hg can double renal output of water, which is called pressure diuresis, as well as double the output of salt, which is called pressure natriuresis via Atrial niatric peptide (ANP)
- In the human being, the renal-body fluid system for arterial pressure control is a fundamental mechanism for long-term arterial pressure control
- The renin angiotensin system plays an instrumental role in this process
What do you call the double renal output of water
Diuresis
What undo you call the double output of salt
Natriuresis
Importance of salt(NaCl) in the renal-body fluid schema for arterial pressure regulation
Salt increases extracellular fluid volume by 2 basic mechanisms
When there is excess salt in extracellular fluid, the osmolarity of fluid increases, this in turn stimulates the thirst center in the brain, making the person drink extra amounts of water to return extracellular salt concentration to normal. This increases the extracellular fluid volume-VENOUS RETURN INCREASES
The increase in osmolarity caused by the excess salty in the extracellular fluid also stimulates the hypothalamic-posterior pituitary gland secretory mechanism you secrete increased quantities of antidiuretic hormone. The antidiuretic hormone(ADH) then causes the kidneys to reabsorbed greatly increases quantities of water from the renal tubular fluid, thereby diminishing the excreted volume of urine but increasing the extracellular fluid volume increases I
Hypertension
Hypertension is defined as a systolic blood pressure greater than or equal to 140 over 90 mmHg
Primary hypertension is the result of complex and poorly understood processes
Secondary hypertension is result of disease processes
Even moderate elevation of arterial pressure leads to shortened life expectancy’s
At severe high pressures-mean arterial pressures 50 percent or more above normal- a person can expect to live no more than a few more years unless appropriately treated
Primary/Essential Hypertension
Approximately 90% of people have primary hypertension
Primary hypertension is due to a combination of hereditary predisposition and environmental factors
Age Stress Smoking Obesity Diet Hereditary
Can primary hypertension be cured
What can you do in your diet to control hypertension
What are the things you should quit
Primary hypertension cannot be cured but in most cases can be controlled
Restricting salt , cholesterol, reduced fat intake
Losing weight Stopping smoking Managing stress Taking anti hypertension drugs Beta blockers Diuretics Calcium channel blockers ACE inhibitors Angiotensin 2 receptor blockers
Secondary hypertension
Approximately 10% of hypertension people have secondary hypertension which is due to identifiable disorders
Renal artery construction
Coarctation of the aorta (narrowing of the aorta )
Phaeochromocytoma (tumor of adrenal glands)
Primary aldosteronism (elevated aldosterone)
Name the 3 ways in which hypertension can be lethal
Excess workload on the heart leads to early heart failure and coronary heart disease , often causing death as a result of a heart attack
The high pressure frequently damages a major blood vessel in the brain, followed by death of major portions of the brain, this is a cerebral infarct “stroke” paralysis, blindness, or multiple other serious brain disorders
High pressure almost always causes injury in the kidneys, producing many areas of renal destruction and, eventually kidney failure, uremia, and death
Volume-loading hypertension
Volume-loading hypertension means hypertension caused by excess accumulation of extracellular fluid in the body
A small tumor in one of the adrenal glands occasionally secreted large quantities of aldosterone, which is the condition called “primary aldosterone”
Aldosterone increases the rate of reabsorption of salt and water by the tubules of the kidney, thereby reducing the loss of these in the urine while at the same time causing an increase in blood volume and extracellular fluid volume
Consequently, hypertension occurs
