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The Neurological System

The Neurological System

The branches of science that will help you understand the body parts and functions are anatomy and physiology. Anatomy deals with the study of the human body (the component parts, structure and position) and physiology the study of how the body functions.

Body Systems

The body comprises of a number of systems including the: Cardiovascular system, Digestive system, Endocrine system, Muscular system, Neurological system, Respiratory system and the Skeletal system.

The Neurological System

All of our body systems work in conjunction with each other and none are capable of working in isolation. The nervous system controls and coordinates the functioning of all other systems in response to our surroundings. Each stimulus or change in our environment is detected by our senses and messages are interpreted by the brain that in turn, sends directions to the various organs to respond and adapt according to the external conditions which affect our body.

The function of the Neurological System is to transmit and receive a constant series of messages via electrical impulses to and from the control centre situated in the brain. These messages are either those receiving "information" from various body tissues via the sensory nerves, or those initiating the function of other tissues such as organs, muscles, etc.

The nervous system is divided into the central nervous system (CNS) that includes the brain and spinal cord, and the peripheral nervous system (PNS) comprising cranial nerves and spinal nerves. The PNS includes nerves emerging from the brain (cranial nerves) and nerves emerging from the spinal cord (spinal nerves). These nerves are divided into sensory nerves that conduct messages from various parts of the body to the CNS, whilst motor nerves conduct impulses from the CNS to muscles and glands. The PNS is further divided into the Somatic System (SNS) and Autonomic System (ANS), depending on the area of the body these messages are transmitted to and from.

The SNS consists of sensory neurons from the head, body wall, extremities, and motor neurons to skeletal muscle. The motor responses are under conscious control and therefore the SNS is voluntary. Certain peripheral nerves perform specialised functions and form the autonomic nervous system; they control various activities that occur automatically or involuntarily such as the contraction of smooth muscle in the walls of the digestive system. The autonomic system is further divided into the sympathetic and parasympathetic systems. These two systems provide nerve stimuli to the same organs throughout the body, but bring about different effects.

The Sympathetic Nervous System helps prepare the body for "fight or flight" and create conditions in the tissues for physical activity. It is stimulated by strong emotions such as anger and excitement and will therefore speed up heart rate, increase the activity of sweat glands, adrenal glands, and decrease those of the digestive system. It also produces rapid redistribution of blood between the skin and skeletal muscles.

Conversely, the Parasympathetic Nervous System slows down the body and helps prepare for a more relaxed state, ready for digestion and sleep. It will therefore increase peristalsis of the alimentary canal, slow down the heart rate, and constrict the bronchioles in the lungs. The balance between these two systems is controlled to create a state of homeostasis that is where the internal stability of the bodily systems are maintained in response to the external environment.

Effect of exercise on the neurological system

Good coordination and balance is vital to the sports person. The quicker the reactions, the more chance the individual has of having "the edge" over the opposition, or of improving his or her personal best. As with most of the Systems, the neurological system can be trained and improved with repetitive exercises. New and extended movements may be progressively attempted, practiced and perfected involving action with the musculoskeletal systems and, as importantly, the voluntary nervous system to initiate those actions.

It is also important to realise that to some extent nerves serving muscles under our conscious control work in pairs and therefore when rehabilitating an injured part it is often beneficial to exercise and stimulate the symmetrically uninjured part as well.

We have already noted how other systems may benefit from exercise and these improvements take place with the help of the neurological system. Like other systems, the neurological system may be adversely affected by smoking, lack of sleep, poor diet and stress.

The nervous system is adversely affected by age. As we grow older neurons are lost and not replaced. There is also a decreased capacity for transmitting impulses to and from the brain and both voluntary and reflex actions become slower.

The Skeletal System

The branches of science that will help you understand the body parts and functions are anatomy and physiology. Anatomy deals with the study of the human body (the component parts, structure and position) and physiology the study of how the body functions.

Body Systems

The body comprises of a number of systems including the: Cardiovascular system, Digestive system, Endocrine system, Muscular system, Neurological system, Respiratory system and the Skeletal system.

The Skeletal System



The skeletal system comprises of 206 bones and provides four basic functions:

Support for tissues and muscle
Protection for vital organs
Movement through bones and attached muscles
Storage for minerals and immature blood cells
Growth

Ossification is the process by which bone is formed. Some bones (e.g. the flat bones of the skull) are formed in one stage from the connective tissue. This process is known as intramembranous or direct ossification.

Other bones (e.g. short bones) are formed from the cartilaginous model of the future bone developed in the embryo, being dissolved and replaced by bone cells. This process is known as endochondral or indirect ossification - most bones are formed this way.

Support

Bones and cartilage that make up the skeleton are the only rigid materials in the body. The 206 bones of the skeleton provide a framework and points of attachment for many of the soft tissues of the body. The five main classifications of bones are : Long (e.g. femur), Short (e.g. tarsal bones of the foot), Flat (e.g. frontal bone of the skull), Irregular (e.g. vertebrae) and Sesamoid (e.g. knee cap)

Protection

These structures protect some of the vital tissues and functional organs of the body. Typical examples are:

Skull - protects the brain
Vertebrae - protects the spinal cord
Thoracic cage - protects the heart and lungs
Movement

Bones act as levers during movement and provide solid structures to which muscles are attached. The joints allow movement between bones and these movements are directly related to the type of joint and range of motion. Joints fall into one of three categories: Fixed fibrous or Synarthroses (e.g. bones of the skull), Slightly moveable or Amphiarthroses (e.g. symphysis pubis) and Freely movable or Diarthroses.

Freely Movable joints comprises of four main groups: Ball and Socket (e.g. hip), Hinge (e.g. elbow), Pivot (e.g. radius and ulna) and Gliding (e.g. carpal joint of the wrist)

Component parts of a synovial joint

A fibrous capsule surrounds the joint and is strengthened by ligaments. The stability of these joints is dictated by the shape of articulating surfaces, their surrounding ligaments and muscles. For example, the knee is given great strength from 2 cruciate and 2 collateral ligaments. Whilst one of the hardest joints to dislocate is the hip. It is formed with the head of femur fitting neatly into the socket or acetabulum in the pelvis.

Articular or hyaline cartilage covers and protects the ends of bones which meet to form a joint and therefore allows freedom of movement. It is a very hard, smooth material which does not repair itself when damaged.

Tendons connect muscle tissue to bone and although more elastic than ligaments, have a far greater tensile strength than muscle.

Synovial membrane lines the joint cavity and covers the tendons and ligaments which pass through it. The membrane produces synovial fluid which lubricates the joints

Shoulder Joint


Ligaments are tough fibrous bands of tissue which connect bone to bone and help stabilise a joint, the strongest ligament in the body being situated at the front of the hip capsule, preventing excessive backward movement of the legs. Ligaments, although stronger than muscle tissue, have fewer nerve endings and less blood supply , and therefore take longer to repair when damaged. Whilst these strong fibrous bands offer great stability to a joint in preventing excessive movement, if they are stretched or torn through injury, they do not necessarily return to their former length and therefore may remain stretched, therefore offering reduced stability to that particular joint.

A bursa is a small sac formed in connective tissue lined by a synovial membrane and containing a small amount of synovial fluid. It is situated between moving parts, often between tendon and bone, to prevent rubbing.


Storage

In some bones, there is red marrow which produces red blood cells, some white cells and platelets. Minerals, especially calcium and phosphorous are also stored in bones and can be distributed to other parts of the body.

Effect of exercise on the skeletal system

The condition of bone may be improved by exercise as it responds to mechanical stresses. These mechanical stresses usually take the form of skeletal muscle pulling at their points of attachment being their origins and insertions. Where these mechanical stresses are applied, most it has been shown that more mineral salts are deposited and more collagenous fibres are produced. Therefore, both the density and size of bone in these areas may be increased and these changes in bone structure are stimulated by increased loads being placed on the skeleton. This has been borne out by greater bone mass being observed in weight lifters than in other lighter endurance athletes such as joggers. Other examples include racquet players who have been shown to have greater bone density in their playing arms. It has even been shown that if a leg is immobilised by being placed in plaster, due to a fracture, that even after a few weeks the bone becomes decalcified from lack of mechanical stress.

Whilst it may therefore be considered beneficial to utilise exercise to maintain healthy bones, great care must be taken with children whose bones and muscles are still developing. They should not be subjected to forms of sport involving high degrees of mechanical stress, partly because of the weaknesses that still exist within the bones, and also because of adverse effects on the development of these bones before maturity.

There are two main effects on bones as we grow older. Bones begin to lose calcium and this is one of the factors contributing to the condition called osteoporosis. Secondly, with age less protein is produced which alters the make-up of bone and sometimes creates brittle bones.

Heart Animation: Coronary Angiography


What is ANGIOPLASTY and STENTING?


Physiology of Lipoprotein Metabolism


neuromuscular junction - motor unit


What is Cholesterol


What is Cholesterol?
Cholesterol is defined as a waxy alcohol, fat-like substance that occurs naturally in all areas of the human body. Your body needs some cholesterol to help it work properly and is required to establish proper membrane permeability and fluidity.
To see your ideal level of cholesterol in the blood see the cholesterol level chart below.
If you have an excess of cholesterol in your blood according to the chart, it can stick to the walls of the arteries. When cholesterol adheres to the artery walls it is called plaque. Plaque will gradually narrow your arteries and can even block them completely.
If an artery that supplies blood to the muscles in your heart becomes blocked, a heart attack can occur.
If an artery that supplies blood to your brain becomes blocked, a stroke can occur.
More that a million Americans die of heart disease each year. One of the major causes is high cholesterol levels in the blood.
The National Cholesterol Education Program suggests that total blood cholesterol level should be:
< 200 mg/dL normal blood cholesterol
200-239 mg/dL borderline-high
> 240 mg/dL high cholesterol.
Cholesterol Level Chart
This blood cholesterol chart shows what your blood cholesterol levels should be and includes low and high cholesterol level measurements
Blood Cholesterol Level ChartDesirableBorderline (high)High Risk
Total Cholesterol< 200200-240> 240
Triglycerides< 150150-500> 500
Low Density Cholesterol< 130130-160> 240
High Density Cholesterol> 5050-35< 35
Eighty-percent of the cholesterol in your body is produced by your liver, and the rest comes from foods like meats, eggs and dairy products.
The biggest influence on blood cholesterol level is fats in your diet, not the amount of cholesterol you eat from food. Narrowing it down further what really matters is the "type" of fat you eat.
Their are two types of fats, "good fat" which are monounsaturated and polyunsaturated fats, lower your risk of disease such as heart disease and atherosclerosis.
"Bad fats" being saturated and trans fats will increase the risk for certain diseases. The key to healthy eating is to substitute the bad fats for good fats avoiding the trans fats. See: Guide to Good and Bad Cholesterol
Major dietary sources containing high cholesterol include cheese, egg yolks, beef, pork, poultry, and shrimp. See: Foods to Reduce Bad Cholesterol.
Cholesterol is insoluble in blood and is transported in the body's circulatory system within lipoproteins.
There is a large range of lipoproteins within blood, generally called, from larger to smaller size: chylomicrons, very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL), low density lipoprotein (LDL) and high density lipoprotein (HDL). The actual cholesterol within all the various lipoproteins is identical.
LDL = bad cholesterol and HDL = good cholesterol
How is Cholesterol Measured?
The measurement of your blood cholesterol level and other blood fats is obtained with a simple blood test by your doctor
You will be advised to fast (not eat) for 12 hours before the blood test is performed. Blood is then taken and sent to a laboratory, where the number of milligrams of cholesterol in the blood is determined. Your doctor will then provide you with the test results in accordance with their medical cholesterol level chart..
The American Heart Association recommends that adults aim for a total cholesterol level below 200 milligrams per 100 milliliters of blood serum.
Testing Cholesterol Levels in the Blood - How often Should you be Tested?
It is recommended by the American Heart Association to test cholesterol every 5 years for people aged 20 years or older.
Cholesterol level testing should be more frequent if a person: is a man over age 45 or a woman over age 50, has total cholesterol of 200 mg/dL or more, has HDL (good) cholesterol less than 40 mg/dL, or is at risk of heart disease and stroke.
Reducing your Cholesterol Chart Levels
If you have had your cholesterol level tested and according to the doctors cholesterol chart you are told you have high blood cholesterol you should look at ways of lowering your cholesterol levels including jogging, walking and any activity that concerns exercising more, eating a variety of fruits and vegetables, and cholesterol lowering medication. It has been said that Yoga may reduce the effect of cholesterol in your body.
Research has also shown that flaxseed and niacin have been proven to lower cholesterol. Red rice extract has also shown that it has cholesterol lowering properties.
Lately a new natural product on the market called red marine algae has been claimed to be an effective means of reducing the cholesterol levels in the blood.


Cholesterol: Top 5 foods to lower your numbers

Cholesterol: Top 5 foods to lower your numbers

Can a bowl of oatmeal help lower your cholesterol? How about a handful of walnuts or even a baked potato topped with some heart-healthy margarine? A few simple tweaks to your diet — like these — may be enough to lower your cholesterol to a healthy level and help you stay off medications.

1. Oatmeal, oat bran and high-fiber foods

Oatmeal contains soluble fiber, which reduces your low-density lipoprotein (LDL), the "bad" cholesterol. Soluble fiber is also found in such foods as kidney beans, apples, pears, barley and prunes.
Soluble fiber can reduce the absorption of cholesterol into your bloodstream. Five to 10 grams or more of soluble fiber a day decreases your total and LDL cholesterol. Eating 1 1/2 cups of cooked oatmeal provides 6 grams of fiber. If you add fruit, such as bananas, you'll add about 4 more grams of fiber. To mix it up a little, try steel-cut oatmeal or cold cereal made with oatmeal or oat bran.

2. Fish and omega-3 fatty acids

Eating fatty fish can be heart-healthy because of its high levels of omega-3 fatty acids, which can reduce your blood pressure and risk of developing blood clots. In people who have already had heart attacks, fish oil — or omega-3 fatty acids — reduces the risk of sudden death.
Doctors recommend eating at least two servings of fish a week. The highest levels of omega-3 fatty acids are in:
  • Mackerel
  • Lake trout
  • Herring
  • Sardines
  • Albacore tuna
  • Salmon
  • Halibut
You should bake or grill the fish to avoid adding unhealthy fats. If you don't like fish, you can also get small amounts of omega-3 fatty acids from foods like ground flaxseed or canola oil.
You can take an omega-3 or fish oil supplement to get some of the benefits, but you won't get other nutrients in fish, like selenium. If you decide to take a supplement, just remember to watch your diet and eat lean meat or vegetables in place of fish.

3. Walnuts, almonds and other nuts

Walnuts, almonds and other nuts can reduce blood cholesterol. Rich in polyunsaturated fatty acids, walnuts also help keep blood vessels healthy.
According to the Food and Drug Administration, eating about a handful (1.5 ounces, or 42.5 grams) a day of most nuts, such as almonds, hazelnuts, peanuts, pecans, some pine nuts, pistachio nuts and walnuts, may reduce your risk of heart disease. Just make sure the nuts you eat aren't salted or coated with sugar.
All nuts are high in calories, so a handful will do. To avoid eating too many nuts and gaining weight, replace foods high in saturated fat with nuts. For example, instead of using cheese, meat or croutons in your salad, add a handful of walnuts or almonds.

How to Learn Human Physiology


“How to Learn Human Physiology Visually in 24 Hours”
-    Dr. Wayne Huang
Human Physiology could be one of the core courses in your academic career. How can you learn it fast and learn it well?
Simple answer: “Rapid Learning”.
Rapid Learning? Yes, it could be your learning edge to ace this course.
You can get started today at Human Physiology
Rapid Learning = Rich Media + Smart Teaching
Rich Media: Human Physiology is a visual science. Naturally, it is easier to learn it visually with rich media.
Smart Teaching: Human Physiology is all about understanding the functions of human organs. Relate them to problem solving (i.e. your exam questions). Smart teaching provides the learning of the core concepts and their interconnections, and applies such the understanding to answer questions and solve problems.
So far so good, but how about the 24 hours?
Learn it the rich-media way. Each intensive hour, you will study the visual tutorial of one chapter for 30 minutes, then you will practice on the interactive problem drill for another 20 minutes, and finally you will super-review the chapter via the pre-made chapter cheat sheet.
With the latest web and video technologies, online learning is now a snap, anytime and anyplaceHuman Physiology. It is much more enjoyable and rewarding than crawling through your lengthy textbooks.
Here is the solution … the rapid learning course “Teach Yourself Human Physiology Visually in 24 Hours”.

IUSOM Faculty Opening in Human Physiology

International University School of Medicine (IUSOM) from its all Worldwide Campuses 
is Providing Medical Education and Training to All without International Borders 
regardless of race, national origin, religion, sex, or age, whoever desires to devote 
the extensive time and effort necessary to practice medicine. IUSOM provides a 
comprehensive 
Basic Science and Clinical Medicine Education enabling students to 
complete a Doctor of Medicine (M.D.) degree. IUSOM Main Campus and all its 
Branch Campuses situated in the different parts of the world also offer 
Pre-Medical 
(PreMed) program.

The Main Campus of International University School of Medicine (IUSOM) located in 
Bonaire, Dutch Caribbean (Formerly Netherlands Antilles) has a faculty position 
open for teaching Human Physiology for the Basic Sciences of Doctor of Medicine 
(M.D.) Degree Program. IUSOM is also accepting applications to fill-in similar faculty 
positions vacant at its Worldwide Branch Campuses situated in Barranquilla 
(Colombia), México City (México), and Sialkot (Pakistan).

Applicants should have preferably an M.D. and/or a Ph.D. Degree, demonstrable 
teaching and clinical experience, and good oral and written English language skills. 
Applicants having lower than Ph.D. Level Education with Outstanding Achievements 
and Experiences in their field of expertise shall also be given full considerations in 
filling these academic vacancies. The position shall be filled at the Assistant, 
Associate or Full Professor level depending upon qualifications and experience.

At IUSOM, positions are offered on a one to three year contract basis, renewable.

Faculty is responsible for course and curriculum development and members are 
placed on student admission committees, promotions committees and other faculty 
and administrative committees.

Applicants from U.S.A, Canada, México, South America, EU, and Asia are welcome 
to apply.
Position requirements

  • Doctoral degree in Human Physiology (e.g.M.D., Ph.D., or equivalent)
  • Substantial teaching experience at a U.S., Canadian, European, Asian or Caribbean Medical School
  • Strong record of excellence and commitment to teaching
  • Evident interest in innovative approaches to teaching
  • Candidates must be willing to relocate to the locality of IUSOM Campus

Compensation
  • Position and salary will be related to the teaching experience
  • Salaries comparable to International prevailing rates
  • Payable direct in US dollars (US $)
  • Up to 90% discount for basic tuition fee at IUSOM, to the Children (Maximum 2) of Faculty staff, who are admitted for pursuing a PreMed and/or M.D. degree program at IUSOM

ApplyingInterested candidates can send an application letter and a complete C.V. together 
with name, mailing address, telephone number, fax number, and E.-Maill address of 
at least 3 professional references,  to IUSOM Headquarters and Main Campus, at 
the following address:

IUSOM Headquarters and Main Campus
International University School of Medicine
Attention: Vice-President Academic
Kaya Mòfi 1
P.O. Box 59
Kralendijk
Bonaire
Dutch Caribbean (Formerly Netherlands Antilles)
Tel.: + 599-717-6792
Fax: + 599-717-8385
E.-Mail: 
admin@InternationalUniversity-SchoolOfMedicine.org
All applications will be treated with strictest confidentiality

Human Physiology (12th Edition)



Book Description:
Clear explanations and a solid learning framework have been market tested and refined. Fox helps students master the fundamentals by providing appropriate anatomical detail.
Human Physiology, Twelfth Edition, is intended for the one-semester Human Physiology course often taken by allied health and biology students. The beginning chapters introduce basic chemical and biological concepts to provide students with the framework they need to comprehend physiological principles. The chapters that follow promote conceptual understanding rather than rote memorization of facts. Health applications are included throughout the book to heighten interest, deepen understanding of physiological concepts, and help students relate the material to their individual career goals. Every effort has been made to help students integrate related concepts and understand the relationships between anatomical structures and their functions.
Book Details:
 US Edition (Reference Only)International Edition (Actual Book)
Condition:Brand NewSame
Edition:12thSame
Author:Stuart Ira FoxSame
Publisher:McGraw-Hill Science/Engineering/MathMcGraw-Hill Higher Education
ISBN-10:00773500650071221905
ISBN-13:97800773500629780071221900
Format:HardcopyPaperback
 Cover Design:Image 1Image 2
 Book Content:US EditionSame
Language:EnglishSame
Color Printed:YesSame
Paper Quality:HighSame
Addons:n/an/a

What is an International Edition? Why buy International Edition?
Most International edition textbooks have the same page-to-page and word-to-word content as US Edition. The price of the International edition textbook is much cheaper than that of US edition. An international edition textbook has soft cover format, different cover design and ISBN. On very rare occasion, some international textbooks may come with different exercises at the end of chapters. International edition textbooks normally have restricted sales disclaimer like “Not for Sales in USA and Canada” printed on the cover of the book even that the books have the same content as US edition or legal to use in North America. United States Supreme Court recently ruled on this issue that conserve your right. Click here to read more on the article reported by New York Times on why thousands of students are now buying International edition textbooks!
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renal physiology

Introduction
In order to analyze the work and development of the wearable artificial kidney and bio-artificial kidney, it is important to understand the physiology that the organ replacement therapies intend to replace. This section describes the important aspects of the anatomy, functions, and failure of the kidney that will help you in analyzing the present and future research endeavors presented in this site.

Anatomy
The kidneys are a pair of fist sized organs located in the small of the back behind the peritoneum. Each kidney weighs about 115g-170g and have the following approximate dimensions: 11 cm in length, 6 cm in width, and 3 cm thick - about the size of a deodorant stick.[3] 
 
 

Source: Fox S.I., Human Physiology 6th edition, pg. 528
Each kidney is perfused at a rate of 600 ml/min by way of the renal artery [3]. Each renal artery branches into interlobar arteries, arcuate arteries, interlobular arteries, and then into 1.2 million afferent arterioles that each feed each nephron, the functional unit of the kidney. After blood has been filtered through the glomerulus and transported through the nephron's vasculature it passes through the interlobular, arcuate, and interlobar that merge into the renal vein and back in to systemic circulation. [2]
The kidney is composed of two regions, the renal cortex and medulla. The cortex is where the renal corpuscles reside, proximal tubules, and distal tubules are found. The medulla is home to the loop of Henle, vasa recta, and collecting tubules. Urine from the various collecting ducts drains into the renal pelvis, ureter, and bladder. 
 
Major functions
The kidneys are often thought of as the body's filters, removing toxins and metabolic waste products from the body. The kidneys certainly perform this task; however they have a few more responsibilities, without which we would not be able to survive.
 

Ultrafiltration
Of the renal blood flow, 125 ml/min is filtered by glomerulus. In one day, the kidney filters approximately 180 liters of blood and produces 1.5 liters of urine. Thus, it is evident that the kidneys possess extraordinary mechanisms to reabsorb water while removing metabolic waste by-products and toxins. [3] Kidney function is measured by the glomerular filtration rate (ml/min) which is defined as the filtration of a solute that is not reabsorbed nor secreted. The clearance (mass removal of a solute/concentration of solute) of a solute can also be used to quantify renal function. 

Source: Fox S.I., Human Physiology, 6th edition, pg. 544.


Endocrine Function
The kidneys secrete the following hormones to initiate processes that occur in other parts of the body: 
1. Erythropoietin to stimulate erythrocyte production in bone marrow. 
2. The active form of Vitamin D, 1,25-dihydroxyvitamin D3, to aid in gut absorption of calcium for bone deposition. 
3. Renin to help regulate blood volume and potassium balance (described in Volume Regulation). 
 

Osmolarity Regulation
Antidiuretic hormone (ADH or vasopressin) is synthesized in the hypothalamus and released in the posterior pituitary in response to an increase in osmolarity as sensed by osmoreceptors in the anterior hypothalamus. The presence of ADH increases the water permeability of the collecting tubule permitting water reabsorption and a shift towards normal plasma osmolarity. In the process, concentrated urine is formed. In the absence of ADH, the water permeability of the collecting tubules is low, more water is excreted in diluted urine, and blood osmolarity returns to normal. 
 

Volume Regulation
In addition to the kidney being anatomically designed to create concentrated urine in order to conserve fluid volume, the kidney is also designed to regulate extracellular fluid volume through the Renin-Angiotensin-Aldosterone (RAA) pathway and Atrial Natriuretic Factor (ANF). 
The kidneys initiate the RAA pathway by secreting renin within the lumen of the afferent arteriole. Renin initiates the cascade of reactions that releases aldosterone from adrenal cortex; thereby stimulating the reabsorption of Na+ in the collecting tubule lumen. Since sodium is primarily an extracellular solute, a change in its concentration will lead to a change in extracellular volume (plasma and interstitial volume). 
Atrial Natriuretic Factor (ANF) is secreted by cells in the atria of the heart to inhibit Na+ reabsorption in the kidneys when there is an excess of Na+ and fluid in plasma. It also inhibits secretion of aldosterone, which also inhibits Na+ reabsorption. 
 

Acid-Base Regulation
Everyday metabolism of proteins and phospholipids generates sulfuric and phosphoric acids, respectively. In order to maintain a normal physiologic pH, the body maintains a buffer reserve of bicarbonate ions. The kidneys regenerate this buffer reserve and excrete the acidic metabolic waste products. 
 
 

Source: Fox S.I., Human Physiology, 6th edition, pg. 554.

Renal Failure
Kidney failure can be grouped into two categories: Acute and Chronic.
 

Acute Renal Failure
There are many mechanisms for this temporary condition when there is sudden loss of renal function in response to trauma, hemorrhage, adverse reactions to anesthesia, bacteria, and autoimmune diseases (glomerulonephritis). There is over a 50% mortality rate associated with acute renal failure. 
 

Chronic Renal Disease & End Stage Renal Disease (ESRD)
Chronic renal disease is defined as the irreversible degeneration of kidney function. People who are diagnosed with chronic renal disease (about 1 in 5,000 to 10,000) have a glomerular filtration rate (GFR) below 25 ml/min.[3] ESRD is diagnosed when GFR is less than 5 ml/min. Dialysis treatment or kidney transplantation is then necessary for survival. Diabetes and hypertension are the two major causes of chronic renal disease, which results in the slow or fast deterioration of nephron functionality. The degeneration of the nephrons is accelerated by the fact that the shrinking population of functional units must assume the filtering capacity of the whole kidney. The other important renal functions (as discussed above) are also compromised. Thus, a person with chronic renal disease or ESRD can be anemic and hypocalcemic and must receive erythropioetin and active vitamin D supplements. 
 

Renal Physiology References
1. Vander A. M.D., Sherman J. Ph.D, Luciano D, Ph.D. Human Physiology: The Mechanisms of Body Function. 6th edition, McGraw-Hill, Inc. 1994. 
2. Fox, S.I., Human Physiology, 6th edition, WCB McGraw-Hill, 1999. 
3. Lysaght, M.J. Ph.D, Biology 108 Lecture Notes, January 30, 2001.

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