ch. 26: blood flow & blood pressure -

what are the walls of arteries like?

thick, elastic, and muscular

what are the walls of veins like?

thinner than arteries

what does vascular endothelium do? (3 functions)

• regulates thrombosis: releases tissue plasminogen activator (t-PA), which dissolves blood clots

• controls the transfer of substances: movement of molecules btwn blood and surrounding tissue

• regulates blood flow: releases nitric oxide, which relaxes vascular smooth muscle & causes vasodilation

what does vascular smooth muscle do?

• regulates blood pressure

• regulates systemic vascular resistance

how does the sympathetic nervous system work with vascular smooth muscle to regulate BP and vascular resistance?

sympathetic nervous system releases norepinephrine (NE), which binds to alpha-1 receptors on vascular smooth muscle —? vasoconstriction, increased vascular resistance, and increased BP

what is BP?

force exterted by circulating blood against the walls of blood vessels (particularly arteries)

what is systolic pressure?

pressure exerted when blood is ejected from ventricles during contraction

what is diastolic pressure?

sustained pressure when ventricles relax

what is pulse pressure?

the difference between systolic and diastolic BP

what 3 things alter BP?

1. cardiac output (CO)

2. blood volume

3. blood vessel diameter/peripheral resistance

what is cardiac output?

volume of blood pumped by one ventricle per minute

what is blood volume?

total amount of blood circulating in body

how does blood volume affect BP?

• increased BV = increased CO = increased BP

• decreased BV = decreased CO = decreased BP

how does blood vessel diameter affect BP?

• vasoconstriction = increased resistance = increased BP

• vasodilation = decreased resistance = decreased BP

what regulates short term BP?

• the sympathetic nervous system

• rapidly adjusts heart activity and blood vessel diameter

what does the SNS use to regulated BP?

• baroreceptors & the baroreceptor reflex

what is the baroreceptor reflex?

• primary neural mechanism the SNS uses for short-term BP regulation

• negative feedback loop between pressure sensors and SNS

what do baroreceptors do? how do they connect to BP?

• stretch-sensitive receptors in the walls of the carotid sinuses & aortic arch

• connect to BP:

  • detect changes in BP

  • signal brain to adjust HR, CO, and BV diameter

what regulates BP long-term?

• hormonal regulation

• adjusts BV and systemic vascular resistance through ADH, RAAS, and epinephrine

how does ADH play a role in long-term BP regulation?

increases water reabsorption by the kidneys = raises blood volume = raises BP

how does RAAS play a role in long-term BP regulation?

RAAS activated when BP, BV, or kidney perfusion drops —> vasoconstriction & increased Na and H2O retention —> raised BP

how does epinephrine a role in long-term BP regulation?

increases HR & cardiac contractility = vasoconstriction = increased blood pressure

with low BP, walk through how RAAS works

low BP —> renin converts angiotensinogen into angiotensin I —> ACE converts angiotensin I into angiotensin II —> angiotensin II causes vasoconstriction & aldosterone release —> aldosterone increases Na and H2O retention in kidneys —> raised BP

what is a lipoprotein?

particle made of lipids & proteins that transport cholesterol & triglycerides through the blood stream

what are the 4 kinds of lipoproteins?

• chylomicrons

• VLDL

• LDL

• HDL

what do chylomicrons do?

transport dietary triglycerides

what does VLDL do?

transport triglycerides made in the liver

what does HDL do?

good cholesterol!

made up of 50% protein

takes excess cholesterol from the bloodstream to the liver to be broken down, where it is converted into bile acids & elimated through feces

what does LDL do?

bad cholesterol (in excess)

main carrier of cholesterol

transports cholesterol from the liver to body cells

what do high LDL levels contribute to?

atheroma formation (fatty plaque)

what do high HDL levels contribute to?

overall cardiovascular health! removes cholesterol from tissues

between HDL and LDL, which is mostly protein?

HDL

what makes up chylomicrons?

80-90% triglycerides

2% protein

what makes up VLDL?

55-65% triglycerides

10% cholesterol

5-10% protein

what makes up LDL?

10% triglycerides

50% cholesterol !!!

25% protein

what makes up HDL?

5% triglycerides

20% cholesterol

50% protein

what is hypercholesterolemia?

high cholesterol in blood

what value indicates hypercholesterolemia?

total serum cholesterol level of 240 mg/dL or more

what does hypercholesterolemia contribute to?

heart attack, stroke, atherosclerosis

what is primary hypercholesterolemia? ex?

• caused by genetic factors

• develops independently of other medical conditions

• ex) familial hypercholesterolemia (no lifestyle or metabolic disorders?

what is secondary hypercholesterolemia? ex?

• result of medical conditions, medications, or lifestyle

• ex) DM, obesity, hypothyroidism

what is arteriosclerosis?

general term for thickening, hardening, loss of elasticity of arteries, which makes it harder to maintain blood flow

what is atherosclerosis?

• a kind of arteriosclerosis

• buildup of fatty plaques (atheromas) in walls of large & medium sized arteries

what do atheromas contain?

• cholesterol

• lipids

• inflammatory cells

• fibrous tissue

• maybe Ca over time

what is the pathogenesis of atherosclerosis?

• endothelial injury

  • triggers inflammatory response

• LDL enters and accumulates in damaged arterial wall

• LDLs oxidize to produce inflammatory mediators and free radicals

• endothelial cells release inflammatory chemicals that attract macrophages to affect area

• macrophages enguld oxidized LDL cholesterol and become foam cells

• smooth muscle cells migrate and multiply within arterial wall —> forming fibrous cap over a fatty core

what is the structure of a atherosclerotic plaque?

• necrotic core w/ foam cells

• shoulder (weak area!)

• cap of endothelial cells

  • contains scar tissue, endothelial cells, smooth muscle cells

what characterizes stable plaques?

• slow growing

• narrows artery over time

• reduces blood flow

• less likely to form emboli

what characterizes unstable plaques?

• more likely to rupture & erode

• can trigger rapid blood clot formation

• may completely block artery or become an embolus

what are nonmodifiable predisposing factors of atherosclerosis?

• cannot be changed

• age

• genetic or familial factors

  • inherited conditions

what are modifiable predisposing factors of atherosclerosis?

• risk factors that can be reduced or managed

• obesity

• sedentary life

• cig smoking

• DM

• poorly controlled hypertension

how does atherosclerosis progress?

• more lipids accumulate

• inflammation develops

• plaques become more complex

what are the earliest visible lesion of atherosclerosis?

• fatty streaks

• thin, flat, yellow discoloration that enlarge

what develops as lipids continue to accumulate and a fibrous cap forms over the lipid core?

• fibrous atheromatous plaque forms

• gradually thickens & narrows lumen

what is a complicated lesion?

• advanced, more complex atherosclerotic plaque

• can rupture, ulcer, hemorrhage, cause blood clots

what arteries are most frequently involved in atherosclerosis? what are common complications involved with these arteries?

• those supplying heart, brain, kidneys, lower extremities, and small intestine

• common complications in larger arteries: thrombus formation, weakening of vessel wall, aneurysm

what are common complications in medium arteries experiencing athersclerosis?

• ischemia or infarction from vessel occlusion

what is peripheral arterial disease?

narrowing of arteries supplying lower extremities due to atherosclerotic plaque buildup

is PAD common?

yes! 21 mil americans over 40 y/o are affected

when do PAD symptoms begin?

• asymptomatic until blood flow becomes significantly reduced

• once artery is narrowed more than 50%

• can manifest acutely when thrombi or emboli compromise blood flow (but this is uncommon)

what are classic symptoms of PAD?

• leg pain

• cramping during walking or exercise

• pain improves with rest

• gastrocnemius (visible calf) muscle needs more oxygen during exercise

• ischemic pain from narrowed arteries

what are advanced symptoms of PAD?

• reduced blood flow even at rest

• pain in legs or feet at rest

• weak distal pulse

• redness in depended position bc of gravity

• thinning of skin, non-healing sores, nail changes

treatment of PAD?

• walking slowly

• avoid injury

• antiplatelet agents

• bypass grafting

• angioplasty

what is acute arterial occlusion?

sudden blockage of arterial blood flow because of a thrombus or embolus, often ocurring in patients with pre-existing PAD

classic manifestations of acute arterial occlusion

• the five P’s (not all may be present simultaneously)

• pistol shot

  • sudden, severe pain

• pulselessness

• paralysis

• paresthesia

  • tingling, burning, itching

• pallor

• polar

  • affected limb feels ice cold

what is thromboangiitis obliterans (TAO) (buergers disease)?

• rare, progressive, non-atherosclerotic inflammatory disease

• affects small and medium sized blood vessels

what characterized TAO?

• inflammation of blood vessels

• narrowing and occlusion

• reduced blood flow to fingers, toes, hands, feet

what group does TAO mainly affect?

men older than 45 years

what’s an early symptom of TAO?

• pain, cramping, in the arch of the foot or the legs while walking

• superficial thrombophlebitis

manifestations of TAO

ischemic ulcerations and gangrene in toes, multiple amputation

what is an aneurysm?

local dilation and weakening of arterial wall, often associated with damage to middle layer of wall (tunica media, where smooth muscle is)

what are the 3 kinds of anyeursms?

• saccular

• fusiform

• dissecting

what is a saccular aneurysm?

local, sac-like bulge on one side of arterial wall

what is a fusiform aneurysm?

circumferential dilation (balloon formation, on both sides, basically) along section of artery

what is a dissecting aneurysm?

tear develops in inner arterial layer (tunica intima), allowing blood to enter & separate the layers of the arterial wall

what is a berry aneurysm?

• an aneurysm that occurs in the circle of willis in the brain

• small, spherical vessel dilation

where do fusiform and saccular aneurysms typically occur?

• thoracic or abdominal aorta

• gradual & progressive enlargement of aorta

what occurs in an abdominal aortic aneurysm, and what are signs & symptoms?

• wall of aorta weakens & stretches

• frequently asymptomatic

• can hear a blowing sound because of turbulent blood flow in the affected artery

• may be able to feel a pulsating abdominal mass

what are signs & symptoms of a dissecting aneurysm?

• abrupt, excruciating pain

• BP and pulse unobtainable

• high mortality risk

  • severe internal bleeding and death without immediate treatment

who is mainly affected by dissecting aneurysms?

men aged 40-60 w/ hypertension Hx

what are varicose veins?

• enlarged, dilated, tortuous superficial veins in the legs

• caused by weakened vein walls or damaged valves

how do varicose veins form? risk factors?

• faulty valves allow blood to flow backward and accumulate in veins

• increased venous pressure —> veins enlarge and become twisted

• risk factors:

  • age

  • female

  • obesity

what is thrombophlebitis?

inflammation of vein because of a blood clot

signs and symptoms of thrombophlebitis?

• asymptomatic

• aching or burning

• tenderness, redness, swelling around affected vein

• serious risk of pulmonary embolism

what is virchow’s triad?

the 3 major factors that increase the risk of venous thrombosis:

1. venous stasis: sluggish blood flow

2. endothelial injury

3. increased blood coagulability

what is hypertension?

high BP

what value indicates hypertension?

BP readings of 130/80 mmHg or higher

what is primary (essential) hypertension?

high blood pressure that develops gradually over time with no identifiable cause

what is the pathophysiologic mechanism of hypertension?

• increased SNS activity

• arteriolar vasoconstriction —> increased peripheral resistance

• increased HR and cardiac contractility —> increased CO

• RAAS stimulation —> increased BV

what is secondary hypertension?

high BP because of a specific conditon

what are common causes of secondary hypertension?

• renal disease

  • kidney disorders that affect fluid balance, and therefore BP regulation

• endocrine disorders

  • hormonal imbalances that increase BP

• pheochromocytoma

  • tumor of adrenal medulla that releases excess adrenaline (a kind of catecholamine)

what is malignant hypertension?

severe, rapidly progressive form of hypertension that causes acute damage to vital organs

what are signs & symptoms of malignant hypertension?

• extremely elevated BP

• diastolic pressure around or above 120 mmHg

• serious complications involving brain, heart, kidneys, eyes

what is left ventricular hypertrophy (LVH), as a complication of hypertension?

• left ventricular wall thickens because heart must work harder to pump blood against increased vascular resistance (increased afterload)

• thickened heart muscle may become stiff & less efficient, leading to heart failure

what is nephrosclerosis, as a complication of hypertension?

damage and hardening of small renal blood vessels because of long-term hypertension

what is glomerular damage, as a complication of hypertension?

reduced blood supply and injury to glomeruli

what is a stroke, as a complication of hypertension?

hypertension weakens cerebral blood vessels, increasing risk of ischemic and hemorrhagic stroke

what are predisposing factors of hypertension?

• age

• sex

  • men develop it earlier in life

  • incidence in women increases after menopause

  • family history

  • high salt intake

  • smoking

  • chronic stress

what are management strategies of hypertension?

• reduce salt intake

• achieve and maintain healthy body weight

• reduce stress

• drug therapy