A THOUGHT FOR TODAY

  A THOUGHT FOR TODAY
  “Education is the most powerful weapon which you can use to change the world”
  -NELSON MANDELA

SPECIAL SENSES -SECRETS

  SPECIAL SENSES - SECRETS
1. What is attenuation reflex?

When very loud sound is transmitted through ossicular system to CNS ,reflex is initiated with a latent period of 40 to 80 ms.this reflex causes contraction of tensor tympani muscle which pulls the malleus inward whereas contraction of stapedius muscle which pulls stapes outward. These two opposing effects make the ossicular system very rigid; therefore, it fails to vibrate with the sound wave. Thus, sound is not allowed to enter inner ear (it is attenuated) or its intensity is reduced by 30 to 40 decibels.

2. What is electro-olfactogram?

When an odorous substance gets absorbed on to the olfactory mucosa, electrical changes are setup.Monophasic negative potential is recorded which lasts for 4 to 6 seconds. This recorded response is known as electro-olfactogram.

3. What is purkinje shift?

In bright light ,cones are optimally functioning ,therefore the peak spectral sensitivity of retina is at 560 nm.In scotopic vision only rods are functional ,therefore peak spectral sensitivity of retina is at 500 nm.This shift of peak spectral sensitivity when a person goes from bright to dim light is known as purkinje shift.

4. What is flicker fusion frequency?

Images of any object remain on the retina for some time so that if pictures are shown one after the other, they give an appearance of being continuous. The critical frequency at which fusion occurs is known as flicker fusion frequency. Critical frequency is much higher in bright light.

5. What is the importance of light and dark adaptation?

Sensitivity of retina increases during darkness and decreases during exposure to light. Thus, sensitivity of retina is automatically adjusted to changes in illumination.

SECRETS WITHIN THE HEART

SECRETS WITHIN THE HEART

1. What is law of heart muscle?

It states that the size of the fibers, glycogen content and rate of conduction increases from nodal to purkinje, while length of systole, duration of refractory period and rhythm city increases in reverse order.

2. Which part of the conducting system of heart has longest refractory period at normal heart rate?
Right bundle branch has the longest and bundle of his has the shortest period.

3. What is the normal refractory period in children?

Oneyear-0.11 sec
6years-0.13sec
12years-0.14sec

4. What is Hill’s sign?

In aortic regurgitation, the blood pressure in the leg is higher than the arm. BP increases that is goes “uphill” as the examiner goes down the body.

5. What are neurohemal organs?

Some of the circumventricular organs function as neurohemal organs. (similar to glands but they store their secretary products in a special chamber until stimulated to release it by a signal from the nervous system or another hormone in to the circulation.eg.oxytocin and vasopressin enter the circulation in posterior pituitary and hypothalamic hypophysiotropic hormones enter the portal hypophysial circulation in the median eminence.

6. What is vagal tone?

Impulses from the vagal nerve producing inhibition of the heart beat.SA node displays intrinsic automacity –spontaneous pacemaker activity at a rate of 100-110 action potentials (beats) per minute.(SAnode is predominantly innervated by right vagus)this vagal tone reduces the resting heart rate down to 60-80 beats per minute.

7. What is vasomotor tone?

Under normal condition, C1 area of the VMC transmits signals to sympathetic vasoconstrictor fibers at a rate of half to two impulses per second called sympathetic vasoconstrictor tone. These impulses maintain a partial state of constriction in the blood vessel called vasomotor tone.

8. What is J point?

The point marking the end of QRS complex and the beginning of ST segment .at this point all parts of the ventricles have become depolarized .so no current is flowing around the heart. Therefore, the potential of ECG at this point is zero voltage.

9. What is J wave?

This is rounded rather narrow ‘hump’ like wave usually superimposed on the distal limb of QRS complex and it is due to the early repolarization.Also known as Osborne’s wave occurs in hypothermia.

10. What is central venous pressure?

Pressure in the right atrium is called CVP because all the systemic veins open into the right atrium.

RAYS OF LIGHT

RAYS OF LIGHT

HEART

*The divine is always seated in your heart, consciously living in you.

*It is the heart that has wings, not the head.

*For the mind-knowledge
  For the heart –love and joy
  For the life-power
  For the matter –beauty.

  RAYS OF LIGHT
  Sayings of 
  THE MOTHER

RESPIRATORY SYSTEM-SECRETS

RESPIRATORY SYSTEM-(SECRETS)

1. Explain the voluntary control of respiration

Voluntary control of respiratory muscles by the motor cortex can override the medullary respiratory centre. This allows us either to speed up ventilation or to hold our breath at will. However, voluntary control is only partial, because if we stop breathing for more than a minute or so, arterial pco2 rises and po2 falls providing a chemoreceptor –driven stimulus to ventilation.

2. What is air hunger?

Increased activity in the vasomotor centre is primarily responsible for cardiovascular adjustments to low blood pressure but also stimulates ventilation. This explains the increased breathing, known as air hunger, which is seen in surgically shocked patients.

3. What is smokers cough?

Individuals who smoke create a constant irritation to the trachea. Overtime, the irritation from smoke can cause the epithelium of trachea to change from a pseudo stratified ciliated columnar to stratified, squamous epithelium. Without cilia, the epithelium cannot clear the mucus and debris. This provides an environment for the growth of microorganism leading to respiratory infections. This trigger the cough reflex commonly called smokers cough.

4. What are the effects of ageing on the respiratory system?

With advancing age, the airways and tissues of the respiratory tract, including the alveoli, become less elastic and more rigid; the chest wall also becomes more rigid. the result is a decrease in lungcapacity.moreover ,a decrease in blood level of o2,decreased activity of alveolar macrophages and diminished ciliary action of the epithelial lining .owing to all these age related factors ,elderly people are more susceptible to pneumonia, bronchitis and other pulmonary disorders.

5. What is the significance of residual volume?

Some amount of air is always present in the lung because of RV or FRC, and therefore continuous exchange of gases is made possible and thereby concentrations of o2 and co2 in blood are maintained constant.

6. Why are venous RBCs more fragile than arterial RBCs?

When blood passes through tissue capillaries, co2 enters into blood and causes chloride shift. (Chloride ions diffuse from plasma into the RBCs).as a result, osmotic pressure inside the RBCs becomes higher than that of plasma. this causes osmotic absorption of fluid into the RBCs.venous RBCs contain therefore the greater quantity of fluid as compared to arterial RBCs .when placed in hypotonic solutions they can take lesser amount of fluid and hence more fragile than arterial RBCs.

PHYSIOLOGY SECRET

PHYSIOLOGY SECRET

Comment on fatigue in diaphragm
Diaphragm is a striated skeletal muscle innervated by phrenic nerve. (C3-C5).Like the heart it must contract in repetitive rhythmical fashion for life. The muscle composition of diaphragm is well suited to the task. Though diaphragm is a skeletal muscle, it is not fatigued.
55% of diaphragm fibers are slow twitch oxidative type: Highly resistant to fatigue.

25% are fasttwitch, oxidative, glycolytic type: Relatively resistant to fatigue.

The remaining 20% are fast twitch glycolytic: susceptible to fatigue.

In general, slow twitch oxidative fibers are arranged with more capillaries, myoglobin, mitochondria and isoenzymes that favors aerobic metabolism. In addition, fast twitch with less capillaries, myoglobin, mitochondria, and isoenzymes that favors anaerobic metabolism.75percentageof muscle fibers have good to excellent endurance characteristics.

PHYSIOLOGY SECRETS

PHYSIOLOGY SECRETS

1. What is amphipathic?
Lipids forms the basic structure of the membrane .the lipid molecules are amphipathic, inotherwords they have a hydrophilic polar region at one end of the molecule and hydrophobic hydrocarbon tail at the other end.
The hydrophilic ends of the lipid molecule line up facing the ICF and ECF.
The hydrophobic tail end faces each other in the interior of the bilayer.

2. What is integral and peripheral membrane protein?
1) Integral or intrinsic proteins bind to the hydrophobic center of the lipid bilayer.
Eg: a).transmembrane protein-span the entire bilayer.
They serve as: channels-through which water-soluble substances can diffuse.
  Carriers-transport materials across the bilayer.
  Pumps-actively transport ions across the bilayer.
  Receptors: initiate intracellular process when activated.
 b) Proteins that is present on only one side of the membrane-
  Eg-enzymes-activate or inactivate various metabolic processes.
2) peripheral-or-Extrinsic-bind to hydrophilic polar heads of lipid or integral protein.
Cytoskeleton-peripheral protein binds to intracellular surface of the membrane.
Glycocalyx-bind to extra cellular surface.

3. What is Michaelis-Menten, kinetics?
Unlike simple diffusion the rate of facilitated diffusion rises as the concentration gradient increases until all the binding sites are filled. At this point the rate of diffusion can no longer rise with increasing point of concentration. This is called saturation or Michaelis –Menten, kinetics.

4. How does the membrane potential affect the rate of diffusion of anions and cations?
Electrical potential produce an electrostatic force. A positive charge inside the membrane will attract anions into the cell and repel cations.net movement of an ion will depend on the balance of the chemical and electrical gradient acting on it that is the electrochemical gradient.

5. Which ions are most important in the osmotic control of cell volume? Why are they important?
Na ions and Cl ions in the ECF and K ions and inorganic anions (po4and sulphates) inside the cell. These ions are important because,
1. They are osmotically active at cell membrane, which have only limited permeability to them
2. They make the largest contributions to the total osmolality of the relevant solutions.
3. There is a concentration gradient across the cell membrane.
This is maintained both by low membrane permeability and by active transport system (for Na and K)
6. What are cell adhesion molecules? CAMs
Cells are attached to each other by cell adhesion molecules. They also transmit signals into and out of cell. These adhesion proteins (viz.laminin, integrin, IgG, Catherin, selectin) play important role in 
1. Embryonic development
2. Formation of N.S
3. Holding tissues together
4. Inflamation and wound healing
5. Metastasis of tumor

7. What is demarcation potential?
If the axon under one of the electrode is damaged, e.g.-by crushing or cutting the nerve (in damaged area, polarity is abolished) then the damaged area becomes negative relative to the healthy portion at rest. Therefore steady potential difference bn: Two electrodes are recorded at rest, called injury (demarcation) potential.

8. What is Retropulsion?
It is the back and forth movement of the chyme caused by forceful propulsion of food against the closed pyloric sphinter.The wave of peristalsis reaches the pyloric sphinter before the chyme,then when the chyme reaches the sphinter ,it is pushed back in to the body of the stomach.

9. What is receptive relaxation?
When the food enters the stomach, the fundus and upper portion of the body relax and accommodate the food. Peristalsis then begins in the lower portion, mixing and grinding permitting small, semi liquid portion to pass through the pylorus and enter the duodenum. Receptive relaxation is vagally mediated and triggered by movement of esophagus and pharynx.

10. What is haustral shuttling?
Bands of muscles divide the large intestine into saclike segments called haustrations.Although haustrations are present when the colon is empty, the entry of food into the colon cause an increase in colonic contractile activity.
The dynamic formation and disappearance of haustral contractions squeeze the chyme, moving back and forth along the colon similar to S.I segmental contractions.

11. What is antral systole?
The contractions of distal stomach caused by peristaltic wave are called antral systole. In addition, can last up to 10sec.waves occur three-4 times/mt

12. What is Ghrelin?
It is a 28a.a polypeptide. It stimulates growth hormone secretion and has pronounced effect on food intake. It is produced in the stomach and arcuate nucleus. The blood levels of it are decreased after food and increased during fasting.

13. What is paralytic secretion?
Claude Bernard observed that cutting the chorda tympani (parasym) in experimental animals produces scanty secretion of thin turbid saliva, which increases to peak on 7th day and decreases in 3rd week. He called it paralytic bcz it was due to cutting the nerve. However, later on it was observed that the secretion is due to increased sensitivity if the gland to adrenaline after cutting the nerve.

14. What is caloric value? State the caloric value of fat, protein and carbohydrate.
The energy liberated from metabolism of 1gm of substance is known as caloric value of that substance.
Fat-9 calories
Protein-4
Carbohydrate-4

15. What is molecular mimicry?
It is a phenomenon that has been discovered as one of the causes for autoimmunity bcz of molecular similarity between foreign and selfpeptides.An example is Rheumatic fever following streptococcal infection. It is due to development of antibodies against streptococcus that cross-react with cardiac myosin and damage the heart. (A portion of cardiac myosin resemble a portion of streptococcal M protein)