# 20.2 Blood flow, blood pressure, and resistance  (Page 4/34)

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## Cardiac output

Cardiac output is the measurement of blood flow from the heart through the ventricles, and is usually measured in liters per minute. Any factor that causes cardiac output to increase, by elevating heart rate or stroke volume or both, will elevate blood pressure and promote blood flow. These factors include sympathetic stimulation, the catecholamines epinephrine and norepinephrine, thyroid hormones, and increased calcium ion levels. Conversely, any factor that decreases cardiac output, by decreasing heart rate or stroke volume or both, will decrease arterial pressure and blood flow. These factors include parasympathetic stimulation, elevated or decreased potassium ion levels, decreased calcium levels, anoxia, and acidosis.

## Compliance

Compliance is the ability of any compartment to expand to accommodate increased content. A metal pipe, for example, is not compliant, whereas a balloon is. The greater the compliance of an artery, the more effectively it is able to expand to accommodate surges in blood flow without increased resistance or blood pressure. Veins are more compliant than arteries and can expand to hold more blood. When vascular disease causes stiffening of arteries, compliance is reduced and resistance to blood flow is increased. The result is more turbulence, higher pressure within the vessel, and reduced blood flow. This increases the work of the heart.

## A mathematical approach to factors affecting blood flow

Jean Louis Marie Poiseuille was a French physician and physiologist who devised a mathematical equation describing blood flow and its relationship to known parameters. The same equation also applies to engineering studies of the flow of fluids. Although understanding the math behind the relationships among the factors affecting blood flow is not necessary to understand blood flow, it can help solidify an understanding of their relationships. Please note that even if the equation looks intimidating, breaking it down into its components and following the relationships will make these relationships clearer, even if you are weak in math. Focus on the three critical variables: radius (r), vessel length (λ), and viscosity (η).

Poiseuille’s equation:

• π is the Greek letter pi, used to represent the mathematical constant that is the ratio of a circle’s circumference to its diameter. It may commonly be represented as 3.14, although the actual number extends to infinity.
• ΔP represents the difference in pressure.
• r 4 is the radius (one-half of the diameter) of the vessel to the fourth power.
• η is the Greek letter eta and represents the viscosity of the blood.
• λ is the Greek letter lambda and represents the length of a blood vessel.

One of several things this equation allows us to do is calculate the resistance in the vascular system. Normally this value is extremely difficult to measure, but it can be calculated from this known relationship:

If we rearrange this slightly,

anatomy defination in urdu
human body largest organ.....
liver
JOY
liver
Lem
Skin
amen
lungs
Zamiir
liver and skin
Marina
skin
brian
by mass is liver but externally is de skin
Kumsah
brian
no
Rehman
liver is the largest gland of the body but skin is the largest organ of the body
Rehman
Marina
afcous skin.because difference between Gland and organ
Safiya
Only the skin
Williams
The largest organ is the skin and the liver is a gland
Williams
skin is the largest organ of the body
Denis
liver
julie
it's the skin
trinna
skin 100%
Mallikharjun
largest organ- liver largest system- Skin
Shahriar
largest organ is skin because it covers the rest of the organs
Syed
nisha
liver
Justine
skin
Areej
liver is largest gland
Areej
skin is largest organ liver is largest gland femur is largest bone thyroid gland is largest endocrine gland seratus muscle is largest muscle
Tanveer
sciatic nerve is largest nerve
Tanveer
portal vein is largest vein
Tanveer
GIT is largest tube in body
Tanveer
explain about cerebrum cereblum and pons medulla
Tanveer
Nervous system anotomy and physiology
Tanveer
skin is the human body's largest organ
Kimbley
@Tanveer, the cerebrum consists of the cerebral cortex, corpus callosum, hippocampus, and basal ganglia. The cerebellum is located inferior to the occipital lobe. The pons and medulla are part of the lower brainstem.
Carmelo
The cerebral cortex are divided into 4 lobes and control functions such as: thinking, learning, speech, sensory perception, motor functions, hearing and vision, etc. The cerebral cortex is mainly present only in mammals due to evolution. The hippocampus plays a main role in memory formation.
Carmelo
The cerebellum works together with the motor cortex and other parts of the brain to coordinate and fine tune muscular activity. The pons and medulla control autonomic functions such as: sleep, respiration, swallowing, vomiting, heart rate, vasomotor control and more other things.
Carmelo
skin hai friend
Tilak
what is the biliary tract
famuyiwa
The biliary tract involves the liver, gallbladder, and bile duct. Certain liver cells (hepatocytes) synthesize bile salts derived from cholesterol in response to Secretin hormone. The gallbladder stores the bile. Gallbladder releases bile to the bile duct in response to Cholecystokinin hormone.
Carmelo
The role of bile is to emulsify fats so that they can be easily broken down and absorbed by the enterocytes into the lacteal vessels.
Carmelo
what is the difference between negative feedback loop and positive feedback loop
famuyiwa
what is cholesterol
Kay
unsaturated fats
famuyiwa
so what is the main purpose of anomaly
Kay
Cholesterol is a waxy substance your body uses to protect nerves, make cell tissues, and produce certain hormones.
Favour
Cholesterol is a type of lipid and it is a nonpolar molecule. The molecule is mainly composed of hydrocarbon chains. Cholesterol is synthesized in the smooth endoplasmic reticulum in eukaryotic cells, and is the main building block material for steroids, Vit D, and bile salts.
Carmelo
Negative feedback loop reverses any change back to its set point. For ex, when your internal body temperature rises above 98.6 F, your hypothalamus triggers your dermal blood vessels to dilate and activate sweat glands through sympathetic motor nerves so you can sweat and cool off back to 98.6 F.
Carmelo
Positive feedback loop amplifies a change. For ex, during labor, oxytocin is released continuously in a positive feedback loop from the posterior pituitary gland to stimulate contraction of the myometrium so the baby can come out.
Carmelo
define homeostasis and explain it's importants
define the important life processes of humans
how the bone marrow transplantation is done?
Tanveer
what is homeostasis
internal temperature of body
Sanket
Homeostasis is the internal constancy in which your body tries to maintain for optimal cellular functioning. For example, your body tries to maintain an internal body temperature of about 98.6F for optimal functioning of your body.
Carmelo
If a prolonged lost of homeostasis occurs, death of the organism will be the outcome.
Carmelo
Another example of homeostasis is that your body tries to maintain a specific blood sugar level, so that your cells can undergo constant cellular respiration and keep you alive.
Carmelo
homeostasis is the fairly constant internal changes of an environment (your internal environment).The temperature of a body must be kept between the range of 37.5°c
raphael
which tissue is more sensitive
to what?
Lari
explain types of hypertension
What is bulbar paralysis?
how can make penis larger
what is the stimuli initiates the control of erythropoiesis?
oxygen
Liyungu
Erythropoietin, a hormone synthesized and released by the kidneys stimulate erythropoiesis in red bone marrow. When an Individual loses blood (hemorrhage) and the concentration of RBCs or oxygen decreases, erythropoitein will be released.
Carmelo
how lymph is from
Lymph is essentially interstitial fluid that ends up in the lymphatic vessels that didn't go back into the venules. Lymph is composed of the same components as your blood plasma which contains water, solutes, oxygen, CO2, foreign particles such as toxins, bacteria and viruses.
Carmelo
what is the cause of twins
Clarus
The cause of identical twins is when a single fertilized egg undergo mitosis (splits in two) . As a result, both eggs now have the same genetic information, therefore producing two identical twins.
Carmelo
how structure and function relate to each other?
Garmai
This is a very important rule in Anatomy and Physiology. The structure of a cell, tissue, or organ will tell you a lot about it's function.
Carmelo
For example, simple columnar cells (enterocytes) in the villus present in the duodenum of the small intestine contain microvilli. Microvilli are finger like projections of the cell membrane (produce by the cytoskeleton)that increase the surface area for absorption of nutrients into the enterocytes.
Carmelo
The main role of these enterocytes is to absorb. Therefore, having Microvilli as a structure relates to its function.
Carmelo
@ Carmelo thanks for the answer.
Garmai
welcome
Carmelo
what is the difference between negative feedback loop and positive feedback loop
famuyiwa
what is anatomy
is simply defined as the stody of internal and external structure of human body and the relationships between the body part.
Surajo
Anatomy Is The Study Of The Structure Of The Human body
Dennis
anatomy is the science that deals with the study of the body structure
Vida
what is stress hyperglycaemia and Pathophysiology
amani
Hyperglycemia is the term used when somebody is in a state of high blood sugar levels. For example, after you eat a meal with carbohydrates in it, (post-absorbptive state) your blood is hyperglycemic.
Carmelo
Pathophysiology is the study of how diseases function and cause abnormal functioning in the body. Usually pathophysiology is studied at a molecular/cellular level.
Carmelo
I meant to say absorbptive* state on explanation of hyperglycemia. Usually during post-absorbptive state your blood has low blood sugar levels.
Carmelo
Explain two best methods of avoiding pregnancies as adolescents
Bright
what is sex?
Your biological sex is determined by your sex chromosome which is pair number 23. if you have a XX pair then you are a female. if you have XY pair then you are a male.
Carmelo
the sex chromosomes are called as allosome
Tanveer
True, the other 22 pairs are called autosomes :)
Carmelo
why the left hemisphere controls the right side body parts and right hemisphere controls the left side body parts?
Tanveer
because it is like that
Sherin
It has to do with how the neuronal pathway are intertwined to opposites sides of the body I think. A motor output from the left cerebral hemisphere (motor cortex) will end up stimulating your right side of the body.
Carmelo
brother Carmelo don't miander, sex ,it just the state of being a male or female
Liyungu
Your biological sex is tied to your DNA (genetic information). A male have testes and female have ovaries which are reproductive organs is tied to your genetic information (sex chromosome). If an individual feels like it is either a male or female is called gender identity.
Carmelo
thanks our beloved brother Carmelo
Liyungu
that's great learning something everyday
Tasheria
what is anatomy
Rohino
most blood enters the ventricle during what phase?
rapid ejection
Tanveer
Most of the blood in the heart enters the ventricles during the diastolic phase.
Carmelo
ok
ren
which of the following is the types of personal protective equipment protects mucous membranes?
Garmai
Most (not all) mucous membranes secrete mucus because they contain goblet cells in between the epithelial tissue. Mucus coats the layers of epithelium and traps particles. The epithelial type is either stratified squamous, simple columnar, or pseudostratified columnar in mucous membranes.
Carmelo
Are you a professor Carmelo?
Sherin
No sir, I'm a nursing and biology student as well in university.
Carmelo
smart!
Sherin
thanks!
Carmelo
why the fever occurs if any injury or pain occurs
Tanveer
fever is de best indication to show there is an infection
Kumsah
what is the actual mechanism of fever
Tanveer
correct Tanveer, the normal internal body temperature is 98.6 Fareinheit. When the temperature rises above 100 fareinheit, it is usually an indication of infection.
Carmelo
White blood cells which protect you against foreign antigens become active and release cytokines (pyrogens) during infection which causes the hypothalamus to raise your internal body temperature.
Carmelo
thank you so much.really you are very intelligent.
Tanveer
thank you. you are very intelligent
Tanveer
the mechanism of fever appears to be a defensive reaction by the body against infectious disease. when bacteria or viruses invade the body and cause tissue injury one of de body immune system's responses is to produce pyrogen
Kumsah
Yes, the hypothalamus responds to pyrogens by raising your body temperature. The reason your hypothalamus does this is to stunt the growth and metabolism of whatever is causing the infection (bacteria, virus, fungi protozoa, etc.)
Carmelo
how the kidney transplantation is done
Tanveer
Which university are you studying?
Sherin
karnataka
Tanveer
and all of you ,university
Tanveer
Really so talented
Savita
Sherin
Georgia State University.
Carmelo
oh nice! I'm in University of Texas
Sherin
nice!!!
Carmelo
vicious this is chaptare I reading 5day after
Taufik
pleas sir can u teach me
Taufik
not sure, can u help me?
Nichole
I'm in University of Technology, Jamaica
Nichole
why do you not helf me
Taufik
what difference exist between anatomy and physiology?
Anatomy: study of the structure of the body parts and their relationship to one another
Shana
Physiology: Study of the function of body parts and how they work to carry out life-sustaining activities
Shana
physiology function and anatomy location
Bashir
anatomy refers to the study of the body parts and their relationship to each other while physiology deals with functioning of those body parts
Umutoni
Yes of course.In layman language Anatomy is study of internal organs, whereas physiology is study of how those organs function. Anatomy is is related to how they look their shape size... Physiology is how they work
Juveriya
anotomy dealt with the external and internal stuctural features of body and their constituent physiology deals with the functioning or action of that stucture
Tanveer
Anatomy is the study of the structures (internal and external) of a living organism. Physiology is the study of how the structures of a living organism function often at a molecular and cellular level.
Carmelo
anatomy is the structure of different body parts of human body and physiology is the normal body function of body parts of the human body
Akshay
anatomy is study of structure of the body e.g, system,organ's size shape location and physiology is the study of function of the body eg,eye ball movement , release of hormones , circulation of blood etc
Soumya
thanks
Tammy
thanks guys. I appreciate
Collins
thanks bro
SAGAR
Explain the meaning of life in a scientific manner
Dezni
probably it doesn't have a meaning yet it can be realised by certain signs that have a scientifically defined terms?!!!!
Osama
At least in a scientific manner, scientists have agreed that production and use of cellular energy, as well as growth and reproduction are essential when defining what is alive in a biological sense. For example, viruses are not considered alive because they cannot grow or reproduce by themselves.
Carmelo
this virus issues is being challenged currently.
Osama
what z your conclusion over virus bro?
Liyungu
pipo what is the relationship between T- cells ( specifically T-helper), & all three line of defence mechanism
Liyungu
anatomy is the science that deals with the study of the human structure whilst physiology is a science that covers the function and process of the body structure.
Vida
defien brache of Anatomy
anatomy is the study of internal and external body parts while physiology is the science that covers the function and process of the body structure.
Priscillah
what is blood fluid
what is menstrual cycle
periodic flow of blood from the female human vigina, after an unfertlized egg has been released from the ovaries
Kobby
the shedding of of the uterine walls,that occurs when fertilization doesn't occur
Kevin
fertilization after occur menstrual cycle
Bashir
it's called menses
Melissa
menses:(menstrual cycle) A monthly shedding of uterine lining and blood. For up to 3 to 7 days every 28 days.
Mel
The menstrual cycle is divided into multiple phases. Menses is the last phase of the cycle when fertilization doesn't occur and endometrium of the uterus shed (stratum functionalis) due to lack of estrogen and progesterone signaling.
Carmelo
The lack of estrogen and progesterone signaling is due to the degeneration of the corpus lueteum when fertilization doesn't occur.
Carmelo
Blood fluid: Blood is composed of blood plasma + formed elements. The blood plasma is 55% of blood volume and it contains 90% of water. It also contains ions, hormones, gases, protein transporters, etc. Blood plasma is also considered extracellular fluid.
Carmelo
The formed elements of blood include RBCs (45-50% of blood), WBCs and Plalets (less than 1% of blood).
Carmelo
Almost forgot, blood plasma also carries nutrients which is obviously very important for survival.
Carmelo
we appreciate bro, our studies are becoming easy & easy
Liyungu
why are postsynaptic ganglionic neurons unmyelinated