Sensory and Motor Neurons

Difference between Sensory and Motor Neurons

Sensory Neuron Motor Neuron
Neurons that carry sensory impulse from sensory organs to the central nervous system are known as sensory neurons A neuron that carries motor impulses from the central nervous system to specific effectors is known as motor neurons.
They are located in the dorsal root ganglion of the spinal nerve They are located in the ventral root ganglion of the spinal cord.
It is unipolar It is multipolar
Comprises of a short axon Comprises of a long axon
An adult has an average of 10 million sensory nerves in the body Half million of motor neurons are found in the body
Found in eyes, skin, ears, tongue and nose Found in muscles and glands

 

Lateral wall of nose

Short essay on lateral wall of nose:

The lateral wall of the nasal cavity is a region of the nasopharynx essential for humidifying and filtering the air we breathe in nasally.

Here we can find a structure called agger nasi. The agger nasi is also referred to as the ‘nasoturbinal concha’ or ‘nasal ridge.’ It can be described as a small mound or ridge found in the lateral side of the nasal cavity. The structure is located midway along the anterior aspect of the middle nasal concha. An abnormally enlarged form may restrict the drainage of the frontal sinus by obstructing the frontal recess area.

The lateral cartilage (upper lateral cartilage, lateral process of septal nasal cartilage) is situated below the inferior margin of the nasal bone, and is flattened, and triangular in shape.

Surfactant

What is surfactant and what is its function?

Surfactant is a mixture of fat and proteins made in the lungs. Surfactant coats the alveoli (the air sacs in the lungs where oxygen enters the body). This prevents the alveoli from sticking together when your baby exhales (breathes out).

Its classically known role is to decrease surface tension in alveolar air spaces to a degree that facilitates adequate ventilation of the peripheral lung.

Physiology of the eye

What is the physiology of the eye?

The eye is composed of a series of lenses and spaces that give focus to images, just as a camera does. It is composed of the vitreous humor, aqueous humor, the crystalline lens, and the cornea, and each of these has its own refraction index (the average being 1.34, because of the content of these tissues).

Physiology of the Eye

The primary function of the eye is to form a clear image of objects in our environment. These images are transmitted to the brain through the optic nerve and the posterior visual pathways.

The various tissues of the eye and its adnexa are thus designed to facilitate this function.

The Eyelids

Functions include: (1) protection of the eye from mechanical trauma, extremes of temperature and bright light, and (2) maintenance of the normal precorneal tear film, which is important for maintenance of corneal health and clarity.

The Tear Film

The tear film consists of three layers: the mucoid, aqueous and oily layers.

The mucoid layer lies adjacent to the corneal epithelium.It improves the wetting properties of the tears.

The Cornea

The primary function of the cornea is refraction. In order to perform this function, the cornea requires the following:

  • transparency
  • smooth and regular surface
  • spherical curvature of proper refractive power
  • appropriate index of refraction.

The Aqueous Humour

The aqueous humour is an optically clear solution of electrolytes (in water) that fills the space between the cornea and the lens. Normal volume is 0.3 ml. Its function is to nourish the lens and cornea.

The Vitreous Body

The vitreous consists of a three-dimensional network of collagen fibers with the interspaces filled with polymerized hyaluronic acid molecules, which are capable of holding large quantities of water.

The Lens

The lens, like the cornea, is transparent. It is avascular and depends on the aqueous for nourishment.

It has a thick elastic capsule, which prevents molecules (e.g., proteins) moving into or out of it.

The Ciliary Body

The ciliary muscle (within the ciliary body) is a mass of smooth muscle, which runs circumferentially inside the globe and is attached to the scleral spur anteriorly.

Accommodation

Accommodation is the process whereby relaxation of zonular fibers allows the lens to become more globular, thereby increasing its refractive power.

The Retina

This is the “photographic film” of the eye that converts light into electrical energy (transduction) for transmission to the brain.

Laryngeal Cartilages

The larynx consists of nine laryngeal cartilages: three are single (epiglottic, thyroid, cricoid) and three are paired (arytenoid, corniculate, and cuneiform).

  • Thyroid:
    • Largest of the cartilages
    • It is composed of two plate-like laminae that fuse on the anterior side of the cartilage to form a peak, called the laryngeal prominence, known as the Adam’s apple.
    • Its posterior border is elongated both inferiorly and superiorly to form the superior horn of thyroid cartilage and inferior horn of thyroid cartilage.
  • Cricoid:
    • Only laryngeal cartilage to form a complete ring
  • Epiglottic cartilage:
    • Consists of elastic cartilage, giving flexibility to the epiglottis
    • Almost entirely covered in mucosa
    • Its stalk projects superiorly and attaches to the posterior aspect of the tongue, so that during swallowing the epiglottis will move to cover the respiratory opening, thus keeping food out of the lower respiratory tubules
  • Arytenoid:
    • Pyramid shaped
    • Anchor the vocal cords
  • Corniculate:
    • Attach to the apices of the arytenoid cartilages
  • Cuneiform:
    • Do not directly attach to other cartilages

Formation of Urine

The nephrons of the kidneys process blood and create urine through a process of filtration, reabsorption, and secretion. Urine is about 95% water and 5% waste products. Nitrogenous wastes excreted in urine include urea, creatinine, ammonia, and uric acid.

Urine formation depends on three functions:

  • Filtration is accomplished by the movement of fluids from the blood into the Bowman’s Capsule
  • Reabsorption involves the transfer of essential solutes and water from the nephron back into the blood
  • Secretion involves the movement of materials from the blood back into the nephron
  • For a detailed diagram and summary, see Fig. 1 on p. 350 and Table 2 on p. 351

Filtration

  • Blood running through the afferent arteriole into the glomerulus is under high pressure (65 mmHg compared to 25 mmHg normally found in capillary beds)
  • Most dissolved solutes (see Table 1, p. 349 for a list) pass through the walls of the glomerulus into the Bowman’s capsule

Reabsorption

  • On average, 600 mL of fluid flows through the kidneys every minute
  • About 20% (or 120 mL) is filtered into the nephron
  • If all of that fluid left in urine, dehydration would be a constant danger
  • Fortunately, only 1 mL of urine is formed for every 120 mL, meaning that 119 mL of fluids and solutes are reabsorbed
  • Selective reabsorption occurs by both active and passive transport
  • Carrier molecules move Na+ ions across the cell membranes of the cells that line the nephron
  • Negative ions (Cl- and HCO3-) follow the positive Na+ ions by charge attraction
  • Many mitochondria supply energy needed for active transport
  • Reabsorption occurs until the threshold level of a substance is reached
  • Excess (like NaCl) remains in the nephron and is excreted with urine
  • Other molecules are actively transported from the proximal tubule
  • Glucose and amino acids attach to specific carrier molecules, which shuttle them out of the nephron and into the blood
  • The amount of solute that can be reabsorbed is limited
  • Ex – individuals with high blood glucose will excrete some in their urine
  • The solutes that are actively transported out of the nephron create an osmotic gradient that draws water in from the nephron
  • A second osmotic force, created by the proteins not filtered into the nephron, also help reabsorption
  • The proteins remain in the blood stream and draw water from the interstitial fluid into the blood
  • As water is reabsorbed from the nephron, the remaining solutes become more concentrated
  • Molecules like urea and uric acid will diffuse from the nephron back into the blood

Secretion

  • Secretion is the movement of wastes from the blood into the nephron
  • Nitrogen containing wastes, excess H+ ions, and minerals like K+ ions are examples of substances secreted
  • Drugs (like penicillin) can also be secreted
  • Cells loaded with mitochondria line the distal tubule, providing energy for active transport

What is vital capacity and its importance?

What is vital capacity and its importance?

Vital capacity (VC) is the maximum amount of air a person can expel from the lungs after a maximum inspiration. It is equal to the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume i.e, VC = IRV + TV + ERV.

The breathing capacity of the lungs expressed as the number of cubic inches or cubic centimeters of air that can be forcibly exhaled after a full inspiration. It is about 3.5 – 4.5 liters in the human body.

It promotes the act of supplying fresh air and getting rid of foul air, thereby increasing the gaseous exchange between the tissues and the environment. Thus, the greater the VC, the more is the energy available to the body. VC of a person gives important clues for diagnosing a lung problem.

Its measurement helps the doctor to decide about the possible causes of the diseases and about the line of treatment.

It determines the stamina of sportsperson and mountain climbers. Sportsperson and mountain dwellers have a higher vital capacity. Young persons have more vital capacity than aged.