Disorders of Blood Flow, Blood Pressure Regulation, and Cardiac Rhythm

3 types of blood vessels based on the direction of blood flow

arteries, veins, capillaries

Arteries

carry blood away from the heart; thick, elastic, muscular walls

Veins

return blood back to the heart; thinnger walls than arteries

Capillaries

smallest blood vessels responsible for exchange between blood and interstitial fluid

3 layers of the walls of arteries and veins

tunica interna, tunica media, tunica externa

Tunica interna

inner layer; endothelium

Tunic media

middle layer; smooth muscle

Tunica externa

outer layer; adventitia

Vascular endothelium

multifunctional tissue

What does vascular endothelium do

regulates thrombosis, controls the transfer of substances, regulates blood flow

Regulates thrombosis

releases tissue plasminogen activator (t-PA), which helps dissolve blood clots

Controls the transfer of substances

movement of molecules between the blood and surrounding tissues

Regulates blood flow

releases nitric oxide (NO), which relaxes vascular smooth muscle and causes vasodilation

Vascular smooth muscle

regulates blood pressure and systemic vascular resistance

SNS activation releases ____________ which binds to ________ receptors on vascular smooth muscle

norepinephrine; alpha-1

SNS activation on vascular smooth muscles causes

vasoconstriction, increased VR and BP

Blood pressure is

the force exerted by circulating blood against the walls of blood vessels, especially the arteries

Systolic pressure is exerted when blood is ejeected from

ventricles during contraction (120 mmHg)

Diastolic pressure is sustained pressure when

ventricles relax (80mmHg)

Pulse pressure is

the difference between systolic and diastolic blood pressure

3 main factors that BP is altered by

• cardiac output

• blood volume

• blood vessel diameter

Cardiac output

volume of blood pumped by one ventricle per minute

Blood volume

total amount of blood circulating in the body

Increased blood volume ____________ cardiac output and BP

increases

Decreased blood volume ___________ cardiac output and BP

decreases

Blood vessel diameter (peripheral resistance)

vasoconstriction and vasodilation

Short term regulation (acute) of blood pressure is managed by SNS

SNS rapidly adjusts heart activity and blood vessel diameter

Baroreceptor reflex

primary neural mechanism for short-term blood pressure regulation

Baroreceptor reflex works through a _________________________ involving pressure sensors and the autonomic nervous system

negative feedback loop

Baroreceptors

stretch-sensitive receptors located in the walls of the carotid sinuses and aortic arch

Baroreceptors will detect changes in BP and signal the brain to adjust

heart rate, cardiac output, and blood vessel diameter

Hormonal regulation

slower, long-term process that maintains blood pressure by adjusting blood volume and systemic vascular resistance

Antidiuretic hormone (ADH)

increases water reabsorption by the kidneys, raising blood volume and blood pressure

Renin-angiotensin-aldosterone system (RAAS)

activated when BP, blood volume, or kidney perfusion decreases and raises BP through vasoconstriction and increased sodium and water retention

Epinephrine

increases heart rate and cardiac contractility and cause vasoconstriction

RAAS steps

Low blood pressure so kidneys release renine, renin converts to angiotensin 1, ACE converts 1 to ll, ll causes vasoconstriction and stimulates aldosterone, bv and bp increases

Lipoproteins

particles made of lipids and proteins that transport cholesterol and triglycerides through the blood stream

Chylomicrons

transport dietary triglycerides

VLDL

transport triglycerides synthesized in the liver

LDL

bad; transports cholesterol from liber to body cells and can contribute to atheroma formation

HDL

good; transport excess cholesterol to liver to be broken down and eliminated as bile/feces to support cardiovascular health

Hypercholesterolemia

high level of cholesterol in the blood which can contribute to heart attack, stroke, other cardiovascular events

Primary hypercholesterolemia

mainly caused by genetic factors; develops independently of other medical conditions

Secondary hypercholesterolemia

caused by other medical conditions, medications, or lifestyle factors

Examples primary hypercholesterolemia

familial hypercholesterolemia

Examples secondary hypercholesterolemia

diabetes mellitus, obesity, and hyperthyroidism

Arteriosclerosis

general term for the thickening, hardening, and loss of elasticity of the arteries

Atherosclerosis

type of arteriosclerosis characterized by the buildup of fatty plaques called atheroma in the walls of large and medium-sized arteries

Atheromas contain

cholesterol and other lipids, inflammatory cells, fibrous tissue, calcium may accumulate over time

Plaques gradually narrow the __________ and may restrict or block blood flow

arterial lumen

Steps of atherosclerosis development

• endothelial injury that triggers inflammatory response

• LDL enters and accumulates in arterial wall

• LDL becomes oxidized and promotes inflammation and radical formation

• endothelial cells release inflammatory chemicals that attract immune cells to area

• macrophages engulf oxidized LDL cholesterol and become foam cells

• smooth muscle cells migrate and multiply within the arterial wall

  • form a fibrous cap over the fatty core

Stable plaques

have a thick fibrous cap that usually grow slowly and narrow the artery over time; may cause reduced blood flow an are less likely to form clots or emboli

Unstable plaques

have thin fibrous cap, more likely to rupture or erode and trigger rapid blood clot formation, may completely block artery or become an embolus

Nonmodifiable predisposing factors of atherosclerosis

risk factors that cannot be changed like age or genetic or familial factors

Modifiable predisposing factors of atherosclerosis

obesity, sedentary life-style, smoking, diabetes mellitus, poorly controlled hypertension

Atherosclerosis progresses as

lipids accumulate in the arterial wall, inflammation develops, and plaques become more complex

Fatty streaks

earliest visible lesion of atherosclerosis; thin, flat discolorations in the intima that progressively enlarge

Fibrous atheromatous plaque

develops as lipids accumulate and fibrous cap forms over the lipid core; gradually thickens and narrows the arterial lumen

Complicated lesion

advanced, more complex atherosclerotic plaque; may rupture, cause ulceration, hemorrhage, and blood clot

Arteries supplying the _______________________ are the most frequently involved

heart, brain, kidneys, lower extremities, and small intestine

In larger arteries, the common complications are

thrombus formation and weakening of the vessel wall which can lead to an aneurysm

In medium-sized arteries,

ischemia and infarction due to vessel occlusion are more common

Peripheral arterial disease

the narrowing or blockage of arteries supplying the lower extremities due to atherosclerotic plaque buildup

Approximately ___ million Americans aged 40 and older are affected by the disease

21

PAD may cause be asymptomatic until

blood flow becomes significantly reduced

PAD symptoms appear when an artery is narrowed by more than ____

50%

PAD may manifest acutely when

thrombi or emboli compromise blood flow (but uncommon)

Classic symptoms of PAD

• leg cramping or cramping during walking or exercise

• gastrocnemius muscle requires increased oxygen during exercise

• narrowed arteries limit blood flow and oxygen delivery

Advanced symptoms of PAD

severe arterial narrowing or occlusion that causes reduced blood flow; pain in legs or feet with weak distal pulse forming redness, thinning of skin, nail changes

PAD treatment

walking slowly, avoid injury, antiplatelet agents, bypass grafting, angioplasty

Acute arterial occlusion

a sudden blockage of arterial blood flow caused by a thrombus or embolus, often occurring with patients with pre-existing PAD

Classic manifestations of acute arterial occlusions

• pistol shot (acute)

• pulselessness

• paralysis

• paresthesia (burning, numbness)

• pallor

• polar (cold skin)

Thromboangiitis Obliterans (TAO) or Buerger’s disease

rare, progressive, non-atherosclerotic inflammatory disease that affects small- and medium-sized blood vessels

TAO is characterized by

inflammation, narrowing and occlusion, reduced blood flow

TAO more commonly affects

men older than 45

Early symptom of TAO

pain at rest

TAO manifestations in distal areas

affects plantar and digital vessels in foot causing ischemic ulcerations, gangrene

Aneurysms

localized dilation and weakening of an arterial wall, often associated with damage to the tunica media

Saccular aneurysm

a localized, sac-like bulge on one side of the arterial wall

Fusiform aneurysm

circumferential dilation along with a section of artery

Dissecting aneurysms

occurs when a tear develops in the inner arterial layer (intima), allowing blood to enter and separate the layers of the arterial wall

Berry aneurysm

commonly occur in the Circle of Willis in the brain; consists of a small spherical vessel dilation

Fusiform and saccular aneursym locations

commonly occurs in the thoracic or abdominal aorta; characterized by gradual and progressive enlargement of the aorta

Abdominal aortic aneurysm

wall of aorta weakens and stretches and a blowing sound (bruit) may be heard over the affected artery due to turbulent blood flow, pulsating abdominal mass

Hemorrhage

a life-threatening condition in which a tear in the inner layer of the aorta allows blood to enter and separate the layers of the arterial wall

Hemorrhage is more common in men aged 40-60 with a history of

hypertension

Clinical manifestations of hemorrhage

abrupt excruciating pain, BP and pulse unobtainable, high mortality risk

High mortality risk

severe internal bleeding, and death immediate treatment

Abrupt excruciating pain in hemorrhage

described as “ripping” or “tearing” chest or back pain

Varicose veins

enlarged, dilated, and tortuous superficial veins, commonly found in the legs

Faulty valves allow blood to flow

backward and accumulate in the veins

Increased venous pressure causes

the veins to enlarge and become twisted

Risk factors for varicose veins

familial tendency, increased BMI, parity (number of times giving birth)

Thrombophlebitis

inflammation of a vein associated with the formation of a blood clot

Signs and symptoms of thrombophlebitis

• may be asymptomatic or go unnoticed

• aching or burning sensation

• tenderness, redness, and swelling around the affected vein

Thrombophlebitis poses a serious risk of

pulmonary embolism; obstruction of pulmonary arteries by emboli

Virchow’s Triad

three major factors that increase the risk of venous thrombosis

Components part of Virchow’s Triad

venous stasis, endothelial injury, increased blood coagulability

Hypertension

high blood pressure

According to AHA, blood pressure readings of _____ mmHg or higher fall within the hypertension range

130/80