topic 18 ch 16

Walls of blood vessels contain

smooth muscle and elastic and fibrous ct

Wall thickness varies in

Different vessels

Inner layer of blood vessels is endothelium:

-secretes paraceine factors

-regulates bp, blood vessel growth, and absorption

Blood vessels contain vascular smooth muscle which dictate

Vasoconstriction vs vasodilation

Arteries act as

Thick layers of

Made up of

– Act as pressure reservoir

– Thick layers of vascular smooth muscles

– Lots of elastic and fibrous connective tissue

Arterioles: site of

Part of

Less elastic

– Site of variable resistance

– Part of the microcirculation

– Less elastic and more muscular

Meta-arterioles: where

Made of:

Contains

– Branches of arterioles

– Partial smooth muscle layer

– Precapillary sphincters open and close to direct blood flow to capillaries or venous circulation

Capillaries

• Smallest vessels

• Primary site of exchange between blood and interstitial fluid

• Walls Lack smooth muscle And are Flat layer of endothelium

Velocity of flow important for

material exchange efficiency

• Primary determinant of velocity is

total cross-sectional area of all capillaries

– Fastest flow in artery system

– Slowest flow in capillaries venues

Venules: receive

Thin

– Receive blood from capillaries

– Thin exchange epithelium

• Veins take blood back to the heart: act as

Thin wall of

One way

– Act as volume reservoir

– Thin walls of vascular smooth muscles/ Less elastic tissue

– One way valves that prevent backflow

Understand

Understand

Pulse pressure

Measures strength of pressure wave produced by ventricular contraction

= systolic pressure - diastolic pressure

Blood pressure decreases

Decreases over distance due to friction

Venous return aided by:

– Valves: one way flow

– Skeletal muscle pump squeezes the veins

– Respiratory pump: changes in thoracic pressure

Mean arterial pressure

– Mean Arterial Pressure (MAP) represents driving pressure

▪ MAP = DP + 1/3 (SP-DP)

Mean Arterial Pressure (MAP)

• Normal MAP Range =

– At least _ to ensure adequate _

▪ like the

• = about 70-100mmhg

– At least 60 mm Hg (or greater) to ensure adequate blood flow to vital organs

▪ Heart, Brain, Kidneys

High MAP =

▪ Excessive pressure in arteries Can lead to

▪ Heart muscle damage Can cause

= >100mmHg

▪ Blood clots

▪ increased risk of:heart attack, Kidney failure,Heart failure

Low MAP =

– Blood may not reach major organs =

– Conditions associated with low blood pressure include:

= <60mmHg

– = tissue damage

– : sepsis, Stroke, Internal bleeding

Flow proportionality net P/ R. Blood flows if and factors affecting resistance

1. Blood flows if a pressure gradient is present

-from areas of higher pressure to areas of lower pressure

- is opposed by the resistance (R) of the system.

4. Three factors affect resistance: radius of the blood vessels, length of the blood vessels, and viscosity of the blood

Steps to Taking BP:

– Inflate cuff (above ~120 mm Hg)

– Auscultate with stethoscope (+ release cuff pressure)

▪ First Korotkoff sound = systolic pressure

▪ Last Korotkoff sound = diastolic

Blood flow into aorta =

• If flow in exceeds flow out (of aorta) then

= cardiac output of left ventricle

– Blood volume increases And MAP increases

– If blood volume decreases, then

▪ Volume compensated through

pressure decreases

▪Fluid replacement (e.g., drinking or intravenous infusion)

– Vasoconstriction

– Sympathetic stimulation of heart

Changes in blood volume affect

blood pressure

Sympathetic control Through _

▪ Norepinephrine maintains arteriolar tone by

Sympathetic innervation of most systemic arterioles

– Binds α receptors → vasoconstriction

Vascular smooth muscle controlled mostly by

• Sympathetic control:

Sympathetic branch

Adrenal medulla releases epinephrine into blood to vasoconstrict and dilate

▪ Vasoconstriction → binds

α receptors with very low affinity on

– skin And splanchnic vessels (digestive properties)

▪ Sympathetic Vasodilation → binds β2 receptors on:

– Vascular smooth muscle: control heart and heart rate

– Skeletal muscle arterioles

Cardiovascular control center in

the medulla

CVCC: Baroreceptor reflex (mechano) is _ and includes _

– Always functioning

– Includes:

▪ carotid bodies (neck)

▪ aortic bodies

Orthostatic hypotension triggers baroreceptor reflex =

decrease in blood pressure due to postural change

– Failure to compensate =

▪ Symptoms:

decreased delivery of oxygen to brain

▪ Symptoms: Light-headedness, Dizziness

• Risk factors for CVD

– Uncontrollable factors:

– Controllable factors:

– Sex, Age, Family history

– Smoking, Obesity, Sedentary lifestyle, Untreated hypertension

Atherosclerosis=

– Increased

– High-density lipoprotein-cholesterol (HDL-C) =

– Low-density lipoprotein-cholesterol (LDL-C) =

= inflammatory process

– blood cholesterol and triglycerides

– healthy cholesterol

– lethal cholesterol

Understand 1-6

Understand 1-6

Primary (or essential) hypertension (90%)

– Has no clear cause other than hereditary

– Cardiac output usually normal But increased peripheral resistance

Secondary hypertension (10%) Due to

to an underlying pathology

treatment for hypertension:

Diuretics: reduce fluid

Beta-blocking drugs: reduce hr and foc

Ace inhibitors: relax blood vessels