How We Hear – Travel Along a Sound Wave from Ear to Brain

Hearing happens in an instant – quick transformations to energy until the movement of molecules is meaningful to a listener. It’s not magic, but the small size and complexity of shapes, movements and structures involved in energy transformation makes the process seem magical. To be able to hear beautiful music or birdsong in spring or mother’s voice is an awesome act of nature.

To put it very simply, sound is a type of energy and to get it from outside the head to the place in the brain where it can be “heard,” sound energy has to be sent from the microphone to the amplifier, along wiring, and on to the translating device.

Outer Ear

The ear that seen on the side of the head acts like a satellite dish that catches waves of sound. This outer ear is shaped to funnel and swirl the sound of energy made when molecules move as they are displaced by air, water or solid objects. The displacement forms waves that flow into the ear hole. In the tunnel that leads to the ear’s complex structures, the molecules move closer together and become louder.

On to the Middle and Inner Ear

Just about an inch past the ear that is seen outside the body and inside the ear hole, sound energy beats on the ear drum. The rhythm is taken up and passed along by three very tiny bones. In the middle ear compartment, the mechanical action of the bones amplify the air waves.

Now in the form of mechanical energy, the wave moves on to another tiny membrane that leads to the shell-shaped and fluid-filled inner ear. In the shell, called the cochlea, sound energy swims through the fluid and strums across teeny, tiny hairs that bend and snap.

On to the Brain

Energy fires neurons bundled into the nerve of hearing, the auditory nerve. The nerve’s long wires or axons zings energy forward to lower brain structures until the energy in analyzed in the cortex of the brain.

Now, if anything is really magical, it’s this part of hearing. How does that electrical energy get processed into meaningful words and sentences? Researchers are just beginning to understanding how the brain works and new discoveries are revealing more and more amazing information every day.

Sound Traveled, Energy Converted, Hearing Accomplished

Hear that? Fast, wasn’t it?

To summarize, the sound energy from the air is captured by the ear, knocks on the ear drum, is amplified by the bones of the middle ear, swims into the waters of the inner ear where waves wash over tiny hairs, which snap an electrical message along nerve wiring to the brain. The energy zaps to the cortex where analysis takes place and a response unfolds next.

Although it happens in an instant, it’s not magic. But hearing is still rather miraculous … or magical … don’t you agree?

Louis Pasteur – A Pioneer: Contributions of Pasteur to the Development of Microbiology

Louis Pasteur, one of the greatest scientists the world has seen, was born on December 27, 1822, in Dole, France. His father was a poor tanner but he wanted Louis to get a good education. Pasteur attended school in a nearby town called Arbois. His headmaster saw potential in him and encouraged him to go to Paris to further his education.

Early Life of Louis Pasteur

Pasteur’s first sojourn to Paris did not go too well. He got homesick and came back to study in a town called Besancon, where he received degrees in Letters and Mathematical Sciences. He got admitted to an elite college in Paris called Ecole Normale Superieure. He obtained his doctorate degree in 1847 and a year later he became professor of Chemistry at the University of Strasbourg. He courted and married Marie Laurent, the daughter of the University Hostel’s Rector, in 1849.

Birth of Stereochemistry

Pasteur’s first landmark contribution was to the field of chemistry where he showed the presence of chiral molecules of sodium ammonium tartarate. Chiral compounds have the same molecular formula but they are mirror images of each other. This discovery triggered the search for chiral molecules of many other compounds giving rise to a new branch of chemistry called Stereochemistry. In 1856, he was made the administrator and director of scientific studies at Ecole. By 1857, Pasteur had become a world famous scientist.

Pasteurization

During his time at the University of Lille, Pasteur was approached by the wine manufacturers of the region. They were concerned about many recent batches of their wine turning sour and this problem was seriously affecting the reputation (and profits) of the famous French Wine Industry. Careful analysis by Pasteur showed that a bacterium had “contaminated” the wine fermentation batches and was producing an acid which was resulting in souring of the wine.

He found out that gentle heating of the wine to around sixty degrees centigrade for about thirty minutes was enough to destroy the bacterium and prevent souring. This came as a great relief for the French Wine Industry and also helped Pasteur’s reputation go far and wide. This technique of Pasteur’s was applied to other beverages as well and particularly to milk where it came to be known as pasteurization.

Discovery of Germ-Disease Relationship

Pasteur also rescued the French Silk Industry which was plagued by a disease called pebrine which affected the caterpillars which died before making their cocoons. Pasteur found out that the disease was caused by a bacterium. He thus found out the connection between bacteria and diseases. He worked with the silk industry to devise methods to keep their hatcheries bacteria-free and thus, disease-free.

Discovery of Attenuation

One of the most important discoveries of Pasteur is, without doubt, attenuation. He was working on a disease which plagued chickens and was affecting the poultry farmers of France. This disease called “chicken cholera” was caused by a bacterium. Pasteur isolated the bacteria from diseased chickens, cultured them outside and when he inoculated this fresh culture into healthy chickens, they developed the disease and died. Legend has it that he left a bottle of culture in his laboratory and went for a couple of weeks’ vacation. When he returned, he inoculated the “old” culture into healthy chickens. The chickens became sick but recovered, much to the chagrin of Pasteur who had expected them to die.

Pasteur then inoculated fresh “virulent” bacterial culture into the same chicken, which surprisingly, failed to die. Pasteur deduced that the bacterial culture had lost its “virulence” or disease-causing ability and had been “attenuated.” This forms the basis of vaccination. Pasteur applied this technique to help protect sheep from anthrax, another fatal bacterial disease. But Pasteur is best remembered for his work on the rabies vaccine, the first human vaccine.

The Rabies Vaccine

Pasteur inoculated the fluid taken from a rabid dog that had just died, into a rabbit. The rabbit developed rabies and died. Pasteur removed the spinal cord of the rabbit, dried it and powdered it. He injected this into a healthy rabbit, which was later inoculated with the virulent inoculums. The rabbit failed to develop rabies. The first person on whom the rabies vaccine was tested was a young boy named Joseph Meister. The boy repaid the benevolence of Pasteur by returning to Paris and working for him. When Meister was key keeper of the Pasteur Institute in Paris, the Nazis raided it and forced Meister to hand over the keys of Pasteur’s crypt. Instead of handing over the keys and betraying his benefactor, Meister shot himself.

Pasteur dedicated his entire life to the goodwill of humankind. He faced personal tragedies during his life with three of his five children dying at a young age. It is a general belief that had the Nobel Prize been instituted earlier, Pasteur would have won it a number of times for his various important contributions. Pasteur died on September 18, 1895 from complications arising from a stroke he had suffered a few years previously.

The Structure and Growth of Flowering Plants: A Comparison Between Monocots and Dicots

An overview of the structure and function of an angiosperms’ root system, stem and leaves, and flowering plant’s adaptations to their environment.

Angiosperms are the most diverse and widespread group of plants. There are over 280,000 known species of flowering plants.

Plant Adaptations to the Environment

Like other organisms, plants have evolved over time, often reflecting the environment in which they live. For example, the cactus that has reduced its leaf size and uses its stem for photosynthesis as a way of reducing water loss. Or plants that live in water that have adapted feathery leaves to increase surface area for photosynthesis.

For most plants however, conditions are not that extreme, and could vary on a daily, weekly or seasonal basis. Because of this, plants have developed physiological adaptations.

Plants produce a hormone that closes stomata when there is not much rainfall or water in soil. Stomata are pores in the plant leaves through which water is lost, or released. In wetter conditions, plants will open their stomata to excrete extra water.

The Difference Between Monocots and Dicots

Monocots:

  • One cotyledon (embryo)
  • Veins in leaves usually parallel
  • Stems have vascular bundles, complexly arranged
  • Fibrous root system
  • Floral parts usually in multiples of threes

Examples of monocots include grasses (wheat, rice, corn), cattails, lilies, palms trees, orchids, bamboos and yuccas.

Dicots:

  • Two cotyledons
  • Leaf veins are usually netlike
  • Stems have vascular bundles arranged in a ring
  • Taproot usually present
  • Floral parts usually in multiples of four or five

Examples of dicots include many trees, and most ornamental and crop plants such as roses, sunflowers or beans.

Plant Structure

The three basic organs of a plant are:

  • Roots
  • Stems
  • Leaves

Plants are multi-cellular organisms. They have organs composed of different tissues, and tissues composed of different cells.

Plant Roots

A plant’s roots are what anchors it to the soil and how the plant takes up nutrients. Monocots have fibrous root systems that expand a mat of thin roots below the surface of the soil to increase the plants exposure to water and minerals.

Dicots have a taproot, which is one large root, which produces smaller lateral roots. These taproots often store food for the plant to consume during flowering and fruit production.

One both monocot and dicot root systems are tiny root hairs, which reside near the root tip. The purpose of these root hairs is to increase the surface area of the root for optimal absorption of water and minerals.

Plant Stems

Plant stems are a system of nodes, internodes, axillary buds and terminal buds.

  • Nodes: the point where leaves attach to stem
  • Internodes: stem segments between nodes
  • Axillary buds: structures that can form vegetative branches, but are usually dormant
  • Terminal buds: where growth of young shoots occurs. Terminal buds have developing leaves and a complete series of nodes and internodes. Terminal buds suppress the growth of axillary buds. This is referred to as apical dominance.

Apical dominance is an evolutionary adaptation that makes the plant grow taller and this exposes the plant to more sunlight. In cases where the top of the plant is damaged (ie: eaten by an animal), or light intensity is strongest at the sides of the plant then the top, axillary buds break dormancy and start to grow, complete with their own terminal buds, axillary buds and leaves.

Plant Leaves

Most photosynthesis occurs in the leaves although green stems can also perform photosynthesis. Leaves generally consist of:

  • A flattened blade
  • A stalk
  • The petiole: which joins the leaf to the node of the stem

Leaves can vary in structure, however. Grasses for example (and many other monocots) lack petioles. Instead the leaf base forms a sheath around the stem. Plant taxonomists use plant leaves to determine plant identity and classification.

Differences in plant leaves aside from shape, spatial arrangement and vein pattern, are:

  • Simple leaf: leaf that has a single, undivided blade
  • Compound leaf: which are divided into several leaflets
  • Double compound leaf: leaf that is further divided into several leaflets

Most large leaves are compound leaves or doubly compound, which allows for strength against strong wind (less tearing) and protection against pathogen spread (ie: able to confine some pathogens to a single leaf rather then whole leaf).