circulatory system

blood flow

how much blood you move past a given point and time period. measured in (liter/hour, ml/min)

Blood Pressure

force exerted on the wall of a blood vessel by the blood contained within, measured in mmHg

blood pressure

the systemic arterial pressure of large vessels of the body (mm Hg)

Resistance to Flow (Peripheral Resistance)

the FORCE resisting the flow of blood through a vessel (usually from friction)

what is blood pressure short for

the blood pressure in the large systematic arteries coming away from the heart that are close to it, usually start at brachial artery

viscosity

a measure of the "thickness" or "stickiness" of a fluid flowing through a pipe, effecting resistance (causing more)

viscosity example

V water < V blood < V toothpaste

. water flows easier than blood

how tube length effect resistance of blood flow

the longer the vessel, the greater the drop in pressure due to friction

how does tube diameter effect resistance of blood flow

smaller diameter= greater friction, smaller tube means flow decreases to any liquid

Blood flow

difference in blood pressure (P) / Peripheral resistance (R)

Increased pressure=

increased flow

decreased preessure

decreased flow

increased resistance (vasoconstriction)

decreased flow

decreased resistance (vasodilation)

increased flow

what produces blood pressure

the heart blood pressure by pumping the blood

what happens to blood pressure when its farther from heart?

Blood pressure decreases with distance from Heart

systolic arterial blood pressure

pressure in aorta (& major arteries) in middle of ventricular contraction (120 mm Hg in healthy adult)

diastolic arterial blood pressure

pressure in aorta (& major arteries) during ventricular diastole, when semilunar valves are closed (80 mm Hg in healthy adult)

mean arterial pressure (MAP)

the "average" blood pressure produced by the heart (93 mm Hg in healthy adult)

mean arterial pressure (calculation)

diastolic pressure + 1/3 pulse pressure

pulse pressure =

systolic pressure - diastolic pressure

L ventricle blood pressure

120 mm Hg

arteries blood pressure

120- 60 mm Hg

arterioles

>60 - 40 mm Hg

capillaries blood pressure

40 - 20 mm Hg

venous

20 - 10 mm Hg

R atrium

10 - 0 mm Hg

venous return

venous blood pressure is so low, other factors contribute to venous blood flow

respiratory pump

breathing action of thorax "squeezes" blood back toward the heart, helps circulation

muscular pump -

contraction/relaxation of skeletal muscles to help circulation across the body

Cardiac Output

stroke volume X heart rate

increased cardiac output causes

increased blood pressure

increased stroke volume causes

increased blood pressure

increased heart rate causes

increased blood pressure

Peripheral Resistance

arteriole constriction ---> increased blood pressure,

resistance inversely proportional to the "fourth power" of the radius change

peripheral resistance when small changes in radius, what happens?

large change in resistance , easy to control resistance bec. of vasodilation/vasoconstriction

hemorrhage

decrease in blood pressure due to blood loss (less RBC)

salt/fluid -

increase in blood pressurem due to increase of fluid retention

polycythemia

increase in blood viscosity, making blood flow harder

RBC anemia

decrease in blood viscosity , decreasing efficiency

Nervous System Control of blood pressure

control of arteriole diameter and directs blood flow to proper organs and tissues that need it

REFLEX PATHWAY:

baroreceptors/chemoreceptors/brain -->

afferent nerve fibers -->

medulla (vasomotor center) -->

vasomotor (efferent) nerve fibers -->

smooth muscle of arterioles

Vasomotor Fibers to Smooth Muscle of Arterioles

sympathetic fibers that release norepinephrine (NE); cause vasoconstriction of arterioles

Vasomotor Center of the Medulla

sympathetic neuron cell bodies in the medulla, receive input from baroreceptors, chemoreceptors, and brain

. vasomotor tone

- general constricted state of arterioles set by vasomotor center

Baroreceptors

blood pressure receptors large arteries (carotid sinuses, aortic arch, neck/thorax arteries)

send blood pressure information to vasomotor center of medulla

increased pressure pathway

increased pressure -->

inhibits vasomotor center -->

vasodilation

decreased pressure pathway

decreased pressure -->

stimulates vasomotor center ->

vasoconstriction

Chemoreceptors location

in aortic arch and carotid arteries

a. carotid and aortic bodies

chemoreceptor function

monitor OXYGEN and pH levels of the blood

low OXYGEN or low pH -------> increase blood pressure, return blood to lungs quickly

Higher Brain Centers Control on BP

hypothalamus & cortex also effect vasomotor area

hormones of adrenal medulla

"fight-or-flight" response to fear; release of

norepinephrine and epinephrine from adrenal medulla; causes vasoconstriction and

increased BP

atrial natriuretic factor (ANF) -

secreted by the atria of the heart, promotes general

decline in blood pressure kidney releasing more Na+ and water, reducing fluid volume

antidiuretic hormone (ADH)

released by the hypothalamus, causes increase in blood pressure by getting the kidneys to conserve water in the body; e.g. during hypotensive situations

endothelium derived factors

endothelin - strong vasoconstrictor

endothelium derived relaxing factor - vasodilation

alcohol causes

- causes vasodilation

Renal (Kidney) direct regulation

fluid loss through urine

a. low pressure/volume --> conserve water

b. high pressure/volume --> release more water

renin-angiotensin mechanism (pathway)

low blood pressure -->

release of renin -->

formation of angiotensin II--> vasoconstriction

release of aldosterone --> Na+/water reabsorption (by kidney)

Measuring Blood Pressure, vital signs

- blood pressure, pulse, respiratory rate, and body temperature

sphygmomanometer-

wrapped around upper arm

b. inflate above systolic pressure of brachial a.

c. pressure released, first sounds - systolic pr.

d. disappearance of sounds - diastolic pr

Hypotension (below normal blood pressure, < 100/60) factors

age, physical conditioning, illness

orthostatic hypotension -

generally in elderly, drop in blood pressure during postural changes

chronic hypotension -

ongoing low blood pressure

chronic hypotension symptoms

low blood protein levels (nutrition)

b. Addison’s disease (adrenal cortex malfunction)

c. hypothyroidism

d. also sign of various types of cancer

Hypertension (above normal blood pressure at rest, > 140/90)factors

weight, exercise, emotions, stress

chronic hypertension

ongoing high blood pressure, prevalent in obese and elderly, leads to heart disease, renal failure, stroke. also leads to more arteriosclerosis

primary hypertension

unidentified source like , high Na+, cholesterol, fat levels, clear genetic component (in families)-

diuretic

promote water removal

NE blockers

- slow vasoconstriction

secondary hypertension

identifiable disorder, kidney disorders, endocrine (hormone) disorders, or arteriosclerosis

Blood Flow in the Body, General Feature

delivery of oxygen and removal of carbon dioxide,. gas exchange in the lungs, absorption and delivery of nutrients from GI tract, and processing/waste removal in the kidneys

normal blood flow at rest abdominal organs

24%

normal blood flow at skeletal muscle

20%

normal blood flow at brain

13%

normal blood flow at heart

4%

other normal blood flow

15%

velocity of blood flow is directly related to

the TOTAL cross-sectional area of the vessel(s)

fastest to slowest velocity

aorta 40-50 cm/s

arteries 20-40 cm/s

arterioles 1-20 cm/s

SLOWEST capillaries 0.1-1 cm/

autoregulation

regulation of blood flow by altering arteriole diameter

a. oxygen and carbon dioxide levels

b. prostaglandins, histamines, kinins

c. needy areas --> more blood flow

myogenic response

change in flow through arteriole in response to stretch of smooth muscle