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HUMAN BIOLOGY, PART 2

Part Two

URINARY SYSTEM

NERVOUS SYSTEM

ENDOCRINE SYSTEM

REPRODUCTIVE SYSTEM

URINARY (RENAL) SYSTEM

This system consists of the KIDNEYS, URETERS, URETHRA, and BLADDER.

Not many structures, but very important.

Functions:

Regulate electrolytes (K, Na, etc) in body
Regulate pH in blood
Regulate blood pressure
Regulate blood volume
Removing metabolic wastes (chemicals produces by chemical reactions in the body are excreted). This is the least important of the kidney’s functions. You can survive for a few weeks without excreting waste products in the urine, but hour by hour, the other functions are more important.

LOCATION OF THE KIDNEYS

They are toward the back side of the body, partly protected by the lower border of the ribcage.

UREA

Urea is a waste product of amino acid metabolism. Remember, proteins are made of amino acids, so when you break down proteins, you break down amino acids, and the waste product left over is urea. This is the main waste product in urine.Diuretics are substances that make you excrete more urine. Alcohol, regular coffee, and regular Coca-cola are diuretics.

COLOR OF URINE

When you urinate, it should be mostly clear with almost no yellow color. The more yellow the urine is, the more dehydrated you are. If the urine is very dark yellow, you are burning too much protein (as in food deprivation).

PROBLEMS WITH THE URINARY TRACT

UTI (urinary tract infection) needs to be treated, or infection can reach the kidney.

UTI can be prevented by drinking lots of water, blueberry or cranberry juice

URETHRITIS = infection of the urethra

CYSTITIS = infection of the urinary bladder

PROBLEMS WITH THE KIDNEY

Things can happen to the kidney: infection, excess proteins, pH change, blood pressure drops, and can lead to kidney failure.

Treatment is DIALYSIS, which removes blood, sends it through a filter, and returns it without the wastes. Done three times a week. Ideally, need a kidney transplant because the kidney has other functions as well.

The brain, heart, and kidney are the only three organs in the body that have to get oxygen to sustain life.

KIDNEY STONES

These develop for unknown reasons.

Stones are made out of a variety of things: uric acid, calcium, etc.

They keep growing.

Kidney Stones cause blockage of the urethra, causing the kidney to enlarge. As the kidney stretches, it causes excruciating pain in cycles of hours. As pressure builds up around the stone, urine can pass, and the kidney stone moves down the urethra slowly.

Symptomatic kidney stones are pea sized or larger (up to 1 ½ inches).

Treatment is ULTRASOUND: Put a powerful speaker on the outside of the kidney, sends a shock wave which the tissues absorb, but the stones shatter so the pieces can pass easier. To help prevent kidney stones, drink enough fluid so your urine stays clear and light colored.

NERVOUS SYSTEM

Parts of the Nervous System

Central Nervous System (CNS): brain and spinal cord.
Peripheral Nervous System (PNS): nerves of the body

Before we talk about these parts, let’s talk about the nerve cells.

The brain has about a trillion nerve cells.

NEURON(main cell of the nervous system)

All neurons do three things:

Receive a signal.
Transmit a signal to another location.
Stimulate another cell
Another neuron  transmit signal
Muscle  contraction
Gland  secretion

There are hundreds of different types of neurons, each one is specialized for a particular task (e.g. sense light, smell, tell muscles to contract, etc). They all share certain characteristics.

MYELIN SHEATH is a coating of lipids around certain types of neurons. It is like the plastic coating around wires we use around the house. It functions to transmit the signals faster. This is important because in a fetus, the only fat in the body is on the myelin sheaths of neurons. Therefore, excess vitamins A, D, E, and K will tend to lodge there and interfere with nerve transmission.

MULTIPLE SCLEROSISis an autoimmune disease where the sheaths of the neurons are destroyed, interfering with the neuron functions in the CNS and brain. Starts to manifest in late teens and early 20’s. It progresses to paralysis and sometimes death. There are treatments, but no cure.

Nerve RegenerationHuman Biology by Sylvia Mader (p.61)

In humans, axons outside the brain and spinal cord can regenerate, but not those inside. After injury, axons in the human central nervous system degenerate, resulting in permanent loss of nervous function. This is not so in cold water fish and amphibians, where axon regeneration in the central nervous system does occur. So far, investigators have identified several proteins that seem to be necessary to axon regeneration in these central nervous system of these animals, but it may be a long time before biochemistry can offer a way to bring about axon regeneration in the human central nervous system. It is possible though, that one day these proteins will become drugs or that gene therapy might be used to cause humans to produce the same proteins when such injuries occur.

In the meantime, some accident victims are trying other ways to bring about a cure. In 1995, Christopher Reeve, best known for his acting role as Superman, was thrown headfirst from his horse, crushing the spinal cord just below the neck’s top two vertebrae. Immediately, his brain lost almost all communication with the portion of his body below the site of damage and he could not move his arms and lags. Many years later, Reeve could move his left index finger slightly and could take tiny steps while being held up right in a pool. He had sensation throughout his body and could feel his wife's touch.

Reeves improvement was not the result of cutting edge drugs or gene therapy-- it was due to exercise. Read the exercised as much as five hours per day, especially using a recombinant bike outfitted with electrodes that made his leg muscles contract and relax. The bike cost him $16,000. It could cost less if commonly used by spinal cord injury patients in their own homes. Reeves, who was an activist for the disabled, was pleased that insurance would pay for the bike about 50% of the time.

It's possible that Reeves advances were the result of improved strength in bone density, which led to stronger nerve signals. Normally, nerve cells are constantly signaling one another, but after a spinal cord injury, this signal ceases. Perhaps Reeves’ intensive exercise brought back some of the normal communication between nerves. His physician is convinced that his axons were regenerating. Reef was convinced that stem cell therapy would one day allow him to be off his ventilator and functioning normally; however, Reeve died in 2004. So far, researchers have shown that both embryonic stem cells in bone marrow stem cells can differentiate into neurons in the laboratory. Bone marrow stem cells apparently can also become neurons when injected into the body.

1. CENTRAL NERVOUS SYSTEM: The brain and spinal cord

THE BRAIN : ANATOMICAL REGIONS

The brain is divided into parts. The largest portion is theCEREBRUM, which makes up 80% of the brain. It’s responsible for consciousness and all the complex behaviors, sensations, etc. The cerebrum is divided into 2 halves calledCEREBRAL HEMISPHERES.In general, the left side controls the right half of the body, and the right side of the brain controls the left half of the body. These two halves of the brain communicate with each other.

Since the brain is so important, it is protected by the skull, cerebrospinal fluid which cushions it, and meninges which are membranes that surround the brain and only let certain substances cross through to the brain.

The brain is one of the few organs that can only use glucose to get ATP as its energy source. Therefore, without some sugar in our bloodstream, the brain will die. That’s one reason why proper nutrition is so important.

By the way, geniuses have the same size brain as everyone else; they are just more efficient at forming synapses. We don’t use 10% of our brains, we use 100%.

MENINGES

These are tissues that cover the entire CNS. They have fluid between them (CSF) and serve to protect and cushion the brain.

HYDROCEPHALUS

Hydrocephalus is when the brain swells.

CEREBRAL SPINAL FLUID

CSF is similar to plasma because it is derived from plasma.

Allows the brain to float. The brain has the consistency of Jell-O, and weighs three pounds. Its weight would crush the inferior structures if it didn’t float.
It cushions. In sudden movement, like riding a bike into a tree, and hitting the head on the tree, the brain hits inside the skull in the front, and then in recoil it hits the back of the skull = closed head injury, not necessarily with a fracture.

MENINGITIS

Meningitis is an infection requiring a spinal tap for diagnosis. This is when the meninges become infected. Can be caused from virus (not that bad) or bacteria (can be fatal). The main symptom is a headache, so when this occurs in an infant, they can’t say where they hurt. So when an infant presents with a high fever of 104˚with no other symptoms, they will usually test for meningitis, because if they miss it, it’s fatal. The test is aSPINAL TAP, where a needle is inserted in the low back below the level of the spinal cord. They draw the CSF to look at. It it’s cloudy or bloody, it’s usually meningitis.

HIGHER FUNCTIONS OF THE BRAIN(control behavior and emotion)

BEHAVIOR

THE FRONTAL LOBEinvolved in planning and judgment. How much time do you need to be ready for the test? Damage here causes people to become docile and do what they are told. 1930’s when people acted up, they did a pre-frontal lobotomy by going up the eyelid and stirring up the brain. Stopped in 1960’s; we do it with drugs now. There was a 16 year old rebel who shot himself in the head, but the bullet went too far forward, and his personality improved! Riddlin suppresses CNS in children, stimulates it in adults. In a criminal psych ward, an inmate with a lobotomy got his hand caught in the electric door, and while his hand was dangling half off, a nurse asked him if it hurt, and he just calmly said, “Yes, quite a lot.” No emotion.

Remember, when you kill a neuron, it does not regenerate; it’s gone forever.

MEMORY

You have different types of memories

MOTOR MEMORYis when you remember things by using your body movements. Drummers and people who play other percussion instruments are good at this. When someone asks you to spell a word and you have to say, “Wait a minute” and you have to write it out, that’s because you learned the word with motor memory.

MEMORY OF EVENTSis when you remember people and events. This type of memory is also used to convert short term memory into long term memory.

When you have to look up a phone number, and then forget it 5 minutes later, that’s short term memory. Memorizing new material is accomplished in two ways:

Repetition
Context

You can’t learn anything brand new; you have to add to what you already know, by putting it into context.

AMNESIA is not caused by a blow to the head; it has to be damage deeper, like from a stroke. Also, a second blow doesn’t cure the first one!Strokes and Alzheimer’s are most likely to cause amnesia. Nemo’s fish friend, Dorothy, has RETROGRADE AMNESIA, which is when a person cannot remember anything new at all.

You can get around amnesia by using motor memory. Give an amnesiac a new puzzle; they’ll do it in 30 mins. The next day, they don’t recognize the puzzle, but they do it in 20 mins, the next day in 10. Therefore, they are learning by motor memory. They can learn their route from home to the market by repetition. But they can’t make a detour, and if anything bumps them off track, they’ll be lost.

No one can remember new things, so you need some context; you need to associate the new thing with something you are already familiar with. That’s why pneumonics are good. If the word “cerebrum” is a brand new word, it sounds like “Sir read broom”, which are words you already know and can visualize. Think of Harry Potter asking a wizard to read the strange words on his new broom: “Sir read broom”, and the wizard scratches his brain (cerebrum) as he tries to read the words. Now it’s easy to remember because you can relate it to something you already know and can picture.

FUN FACTS ABOUT THE BRAIN

Bees tell other members of the hive where food is by doing a special dance that relays distance and direction. Octopus have the ability to sort out complex problems on their own

A dolphin doesn’t need to see to catch a meal. It sends out sound waves which bounce back and create a 3D ultrasound picture of it, even in complete darkness. A dolphin’s brain in relation to its body is larger than that of a chimpanzee or great ape.

Dolphins are one of the most intelligent mammals; they've learned to sleep using only half their brains. While one half rests, the other remains alert and continues the respiratory process, without interruptions.

The brain of a roach is located in its body, and if by accident (natural or human) it should lose its head, it can live up to nine days completely decapitated. It dies from starvation.

SPINAL CORD

Really, this is just a continuation of the brain. The primary functions of the spinal cord are for simple reflexes and to be a link between brain and body

If a person has a spinal cord injury in their cervical region, they could have quadriplegia (arms and legs paralyzed).

If a person has a spinal cord injury in their thoracic region, they could have paraplegia (legs only)

THE EYE

EYE JOKE

What did the right eye say to the left eye?
Between you and me, something smells!

GLANDS OF THE EYE

1. LACRIMAL GLANDS are the largest set. They are on the superior lateral eyelid (overhead) and they produce tears, which have enzymes to kill bacteria (which thrive in warm, moist conditions). The tears moisten and lubricate the eye surface. They drain out into the LACRIMAL DUCT, which is seen as a small hole in your lower inner eyelid.

2. LACRIMAL CARUNCLE (“little meat”) is the spot on the medial corner of the eye. It makes an oily secretion to lubricate the eye for the eyelids. When the secretion dries, it is called “sand” in the eyes.

3. CILLIARY GLANDS go to only the cilia. When clogged = STY.

PROBLEMS WITH THE LENS

PRESBYOPIA: (“old eyes”). Occurs around age 45-50. With age, the lens loses flexibility. It stays in the position for seeing far, so there is trouble focusing on things that are near.

CATARACTS: Clouds in the lens which can completely cloud the eye. Treatment is to remove the lens and replace it with a plastic one.