Sunday, June 13, 2010

Does stress affect memory?


PHYSIOLOGY TUTORIAL
Does stress affect memory?
The primary area of the brain that deals with stress is its limbic system. Because of its enormous influence on emotions and memory, the limbic system is often referred to as the emotional brain.
During times of stress, the body responds by releasing hormones that trigger physical changes. Chronic stress can have negative effects on our well being, leading to higher blood pressure, increased abdominal fat and decreased bone density.
Exposure to stress can damage hippocampus. The damage results from a kind of chain reactions or feedbackloop.The cycle begin when adrenal glands release steroid hormones called glucocorticoids into the bloodstream. The hippocampus has a high density of receptors for glucocorticoids and in normal circumstances it helps regulate the production of stress hormones. However hippocampus is particularly sensitive to these hormones. Studies have shown that hippocampal neurons of rodents die when they are exposed to glucocorticoids for months and the neuronal dendrites atrophy when they are exposed for few weeks of stress. As a result of the damage stress hormones continue to be secreted at increased levels, resulting in even more damage to the hippocampus
Because exposure to stress can damage the hippocampus and because hippocampus is an important brain structure associated with declarative memories for facts, researchers have been particularly interested in how stress affects our ability to remember new information.
Stress management is the solution, not stress elimination
Bear in mind that an appropriate stress response is healthy and necessary part of life. one of the things it does is to release NE ,the excitatory neurotransmitter.NE is needed to create new memories, it improves mood, problems feel like more challenges, which encourage creative thinking that stimulates our brain to grow new neuronal connections .
Sympathetic system turns on fight and flight response. In contrast the parasympathetic system promotes relaxation response. The challenge in this day and age is not to let the sympathetic system stay chronically aroused. This may require knowledge of techniques that work to activate our relaxation response.
Lifestyle, personality, and even genetic makeup influence our emotional and physiological responses to stress. But we can modify those responses by making changes in how we act, think, relate, move, and relax.
P.S –Refer, Stress and destress posted by Dr.R.vinodha in vinodha’s blog on Sep 2, 2007.

Tuesday, February 23, 2010

PHYSIOLOGY TUTORIAL- "Free running rhythm"



“FREE- RUNNING” CIRCADIAN RHYTHM
Most totally blind people have free-running circadian rhythm. (i.e. Not synchronized to 24 hr light dark cycle, but oscillates on a cycle slightly longer than 24 hr.).This causes insomnia and daytime sleepiness. A similar phenomenon is seen in subjects exposed to continuous absence of natural light in Antarctica during winter months.
Melatonin secretion shows a circadian rhythm, the level being higher at night, the peak at 3-4 am. This fluctuation depends on the sympathetic innervations of the pineal gland. (Nervi conarii).Further in blind melatonin level shows an approximate 24 hr rhythm, but the peak may be at any time. So, in blind the biological clock (SCN of Hypothalamus) is able to maintain circadian rhythmic secretion but not its relationship to light-dark cycle. Such a 24hr rhythm which shows no relation to light or dark is called “free-running”.since evidences support that, diurnal changes in melatonin secretion function as a timing signal that coordinates endocrine and other internal events with light-dark cycle, the blind people can be “ entrained”to 24 hr cycle with melatonin.
Note: Retino hypothalamic fibers synapse in the SCN. There are connections from SCN to intermediolateral gray column of spinal cord.preganglionic neurons pass from spinal cord to superior cervical ganglion, post ganglion neurons project from this ganglion to pineal in the nervi conarii.

Sunday, January 3, 2010

HAPPY NEW YEAR 2010


HAPPY NEW YEAR 2010
Every moment in a day has its value
Don’t waste time grieving over past mistakes
Learn from them and don’t repeat the same mistake
New Year begins; let us pray for happiness &peacefulness
I wish you that your all dreams comes true.
HAPPY NEW YEAR

A VECTOR DIAGRAM OF OCULAR MUSCLE ACTION


Saturday, December 12, 2009

PHYSIOLOGY TUTORIAL


PHYSIOLOGY TUTORIAL

What are the angles formed by extra ocular muscles with the visual axis in primary position? Explain the movements on the different direction of visual axis.

The relative importance of primary and secondary actions of extra ocular muscles depends on the direction of visual axis.

Medial and lateral recti lie on the horizontal meridian of the globe. Their functions are relatively simple and antagonistic. Contraction of medial rectus adducts and lateral rectus abducts the globe.

Superior and inferior recti subtend a 23° angle with the visual axis when the eye is in primary position.

When the eye is abducted 23°

The superior rectus acts solely as an elevator,

The inferior rectus acts solely as depressor.

When the eye is adducted 67°

The superior rectus acts solely to incyclotort the globe

The inferior rectus acts solely to excyclotort the globe.

Superior oblique –this vector plane subtends a 54° angle with the visual axis when the eye is in primary position.

When the eye is adducted 54°

Superior oblique acts solely to depress the globe

When the eye is abducted 36°

Superior oblique acts to incyclotort the globe.

Inferior oblique-subtends a 51° angle with visual axis when the eye is in primary position.

When the eye is adducted 51°

Inferior oblique solely elevates the globe.

When the eye is abducted 39°

Inferior oblique solely excyclotort the globe.

Sunday, August 23, 2009

A THOUGHT FOR TODAY


Never leave till tomorrow, which you can do today.
Benjamin Franklin.

Tuesday, August 18, 2009

PHYSIOLOGY SECRETS IN IMMUNOLOGY


1.which cell is called military intelligence system?
B-lymphocyte.

2.what is virgin B/naive cell?
B cell with fully rearranged IG genes but not yet encountered non-self antigen.

3.what is immunological synapse?
The interaction between TCR and MHC

4.List the main categories of antigen recognition molecule-
TCR,BCR,MHC

5.What is the ratio of T:B?
3:1