Blood Vessels Flashcards
What is the locations of Baroreceptors
Carotid sinuses
Aortic arch
Walls of large arteries of the neck and thorax
What is the function of Baroreceptors?
Inhibits vasomotor and cardioacceleratory centers
-causing arteriolar dilation and venodilation
Baroreceptors are decreased in blood pressure due to…
Arteriolar vasodilation
Venodilation
Decreased cardiac output
What is the function of Chemoreceptors?
Detect increase in CO2, or drop in pH or O2
Causes increase blood pressure
How do chemoreceptors causes increase in blood pressure?
By signaling cardioacceleratory center (which increase CO)
By signaling vasomotor center (which increase vasoconstriction)
What are influences of Higher Brain Centers?
Reflexes in the medulla
Hypothalamus and cerebral cortex can modify arterial pressure via relays to the medulla
Hypothalamus increase blood pressure during stress
Hypothalamus mediates redistribution of blood flow during exercise and changes in body temperature
Hormonal Controls
Short term regulation…via changes in peripheral resistance
Long term regulation…via changes in blood volume
What is the function of neural controls of peripheral resistance?
- Maintain MAP by altering blood vessel diameter
- Alter blood distribution to organs in response to specific demands
- Operate via reflex arcs*
What hormonal controls increase blood pressure?
Epinephrine and norepinephrine from adrenal gland–increases CO and vasoconstriction
Angiotensin 2 stimulate vasoconstriction
High ADH levels causes vasoconstriction
What hormonal controls decreases blood pressure?
Atrial natriuretic peptide causes decreased blood volume by antagonizing aldosterone
What two ways does the kidneys regulates arterial blood pressure?
- By direct renal mechanism
2. By indirect renal (renin-angiotensin-aldosterone) mechanism
What are the functions of Direct Renal Mechanism?
Alters blood volume independently of hormones
- increased blood pressure or blood volume causes elimination of more urine (thus reducing blood pressure)
- decreased blood pressure or blood volume causes kidneys to conserve water, and blood pressure rises
Indirect Mechanism
Explain the renin-angiotensin-aldosterone mechanism….
Decreased arterial blood pressure - releases renin
Renin catalyzes conversion of angiotensingen from liver to angiotensin 1
Angiotensin converting enzyme (from the lungs) converts angiotensin 1 to angiotensin 2
What is the function of Angiotensin 2?
Increases blood volume
- stimulates aldosterone secretion - causes ADH release - triggers hypothalamus thirst center
Causes vasoconstriction to increase blood pressure
Define Vital Signs
Pulse and blood pressure, alone with respiratory rate and body temperature
Define Pulse
Pressure wave caused by expansion and recoil of arteries
How is Systemic Arterial BP is measured?
Measured indirectly by auscultatory method using a sphygmomanometer
Pressure increased in cuff until it exceeds systolic pressure in brachial artery
Pressure released slowly and examiner listens for sounds of Korotkoff with a stethoscope
How to measure Systolic Pressure?
Normally less than 120 mmHg
Is pressure when sounds first occur as blood starts to spurt through artery
How is Diastolic Pressure measured?
Normally less than 80 mmHg
Is pressure when sounds disappear because artery no longer constricted (blood flows freely)
Hypertension of Blood Pressure
Sustained elevated arterial pressure of 140/90
Prehypertension of Blood Pressure
Happens if valves elevated but not in hypertension range
May be transient adaptation during fever, physical exertion, and emotional upset
Persistent in obese people
What are the major causes of prolonged hypertension?
Heart Failure, Vascular Disease, Renal Failure, and Stroke
Heart must work harder
Myocardium enlargers, weakens, and becomes flabby
Also accelerate atherosclerosis
Primary Hypertension
Is 90% of hypertension condition
Has no underlying causes
Has no cure (can be controlled)
Risk Factor of Primary Hypertension
Heredity Diet Obesity Age Diabetes Mellitus Stress Smoking
Primary Hypertension is controlled by..
Restrict Salt, Fat, and Cholesterol intake
Increased Exercise, Lose Weight, and Stop Smoking
Anti hypertension Drugs
Secondary Hypertension
Less common
Due to identifiable disorder:
Obstructed renal arteries, and kidney disease
Endocrine disorder:
Hyperthyroidism and Cushing’s syndrome
What is Orthostatic Hypotension?
Temporary low blood pressure and dizziness when suddenly rising from sitting or reclining position
What is Chronic Hypotension?
Hint of poor nutrition and warning signs of Addison’s disease or hypothyroidism
What is Acute Hypotension?
Important sign of circulation shock
-threat for surgical patients and those in ICU)
What is Tissue Perfusion involved in?
Delivery of O2 and nutrients to, and removal of wastes from tissue cells
Gas exchanges in the lungs
Absorption of nutrients in the digestive tracts
Urine formation by the kidneys
Define Autoregulation
It is automatic adjustment of blood flow to each tissue relative to its varying requirements
Controlled by modifying diameter of local arterioles feeding capillaries
Two types of Autoregulation
Metabolic Controls
Myogenic Controls
Both determines final auto regulatory response
Effects of Metabolic Controls
Relaxation of vascular smooth muscles
Release of No (powerful vasodilator) by endothelial cells
Myogenic Control
Myogenic responses keep tissue perfusion constant
Vascular smooth muscle responds to stretch
Passive Stretch
Increases intravascular pressure
Promotes increased tone and vasoconstriction
Reduced Stretch
Promotes vasodilation
Increases blood flow to tissues
Angiogenesis
Number of vessels to region increases and existing vessels enlarge
Common in heart when coronary vessel occluded, or throughout body in people in high altitude areas
Hypovolemic Shock
Result from large scale blood loss
Vascular Shock
Results from extreme vasoconstriction and decreased peripheral resistance
Cardiogenic Shock
Results when an inefficient heart cannot sustain adequate circulation
Pulmonary Circulation
Short loop that runs from the heart to the lungs and back to the heart
Systemic Circulation
Long loop to all parts of the body and back to the heart
