Saturday, November 26, 2011

Vasomotor reversal of Dale

Do you know that a particular neurotransmitter can act on different types of receptors?
So it's not the neurotransmitter but the receptor on which the response depends upon
Hence depending upon the receptor a varied effect is obtained! :O

An awesome example of this is the neurotransmitter adrenaline.
It acts on two types of receptors.. Alpha and beta receptors.
Alpha receptors cause vasoconstriction where as beta receptors mediate vasodilation.
Beta receptors are more sensitive.

So large i.v. infusion of adrenaline causes vasoconstriction which increases blood pressure via the alpha receptors.
But after a while, there is a re-uptake and dissipation of adrenaline.
This decreases the adrenaline concentration.
Which doesn't stimulate the alpha receptors but is enough to stimulate the sensitive beta receptors.
Hence there a secondary fall in blood pressure.

Vasomotor reversal of Dale
So what happens if you block only the alpha receptors?
A fall in blood pressure due to beta mediated vasodilation!
This is known as vasomotor reversal of Dale :D

To be specific, the receptors involved are Alpha 1 and Beta 2 receptors.
You may remember the mnemonic, ABCD, Alpha - Constriction, Beta - Dilation! :D

That's all!

Have an amazing weekend! :)


Updated: Mnemonic on 28 Nov, 2013.
Related posts: Noradrenaline and adrenaline mnemonic

Thursday, November 10, 2011

Clotting factors mnemonic

Hello everyone! =D

Clotting factors are substances in the blood that act in sequence to stop bleeding by forming a clot.

Here's a mnemonic to help you remember them ^___^

Clotting factors mnemonic

Fasciculus gracilis and cuneatus

Hey guys.. Let's draw the sensory tracts that are found within the dorsal white column of the spinal cord!
Might as well read about em too ^_^

What I like to do is write down the points with the diagrams [As you guys already know]
So lemme present to you.. my notes! =D

Their primary responsibility is to carry sensory information regarding discriminative senses (viz., proprioception, vibration, stereognosis, and two-point discrimination) to higher centers
I've drawn a feather for fine touch, tuning fork for vibration and closed eye for stereognosis! [In case you didn't understand ^_^ ]

Here is the description point wise.. :)

Sensory regions covered by Cuneatus and Gracilis mnemonic
GRAcilis - Walk GRAcefully (Lower extremities and lower trunk)
CunEATus - EAT with your hands (Upper extremities and upper trunk)

Remember: Crude touch is NOT carried by this tract
It is carried by the anterior spinothalamic tract

That's all :)


Wednesday, November 9, 2011

Sciatic nerve distribution and Sciatica

Hey guys.. I'm gonna tell you about Sciatica today!

But first, lets see a summary of the distribution of the sciatic nerve ^_^
The sciatic supplies nearly the whole of the skin of the leg, the muscles of the back of the thigh, and those of the leg and foot
It is the largest nerve in the body! :O
It has the tibial part which is a ventral division of anterior primary rami of L4 L5 S1 S2 S3 nerves
and the common peroneal part.. the dorsal division of anterior primary rami of L4 L5 S1 S2
[My mnemonic was CD.. Common peroneal - Dorsal division & since C is the 3rd alphabet so its smaller than T which is the 20th letter of the alphabet.. hence it has lesser nerve roots]

Sciatica - The compression or irritation of Sciatic nerve.. which causes pain..

Now how does that happen? :O
It may be due to tumors, pregnancy or infection of muscles [causing inflammation and irritation]
I'll elaborate on spinal disc herniation and Piriformis syndrome :D

Nerves called the spinal nerves or nerve roots, branch off the spinal cord and pass out through a hole in each of the vertebrae called the foramen
Now if you have studied the spinal cord well.. You'll know that the spinal disc are right up against the nerve..
If herniation of disc occurs.. It'll push up against that nerve.. which will create pain that is transmitted all the way down to the sciatic nerve

Also there is a muscle called Piriformis.. which runs from the sacrum to the hip.. in most people muscle is on top of the sciatic nerve.. Which is normal
In some people the nerve pierces the muscle.. which causes compression of the nerve and hence the Piriformis syndrome

Course of Sciatic nerve - Description is pending and will be updated later :)

The Straight leg raise, also called Lasegue's sign is done to determine whether the patient has a herniated disk
With the patient lying down on his back.. the examiner lifts the patient's leg while the knee is straight
If pain in the sciatic distribution is reproduced between 30 and 70 degrees passive flexion of the straight leg the test is positive

Tenderness in the area of the sciatic notch indicates Piriformis syndrome

Low back and leg pain? Check Sciatica! :D

That's all!
Thank you so much for reading :)


Monday, November 7, 2011

Decompression sickness - Caisson's disease

Caisson's disease.. key-suh n.. :D

Occurs when you return to normal pressure from area of high pressure. 

Do you know that even at about 10 m below the surface the water exerts twice the pressure?
So when you go underwater, the pressure increases.. That's how your lungs end up taking more nitrogen than usual! :O

Water pressure increases.
Pressure of nitrogen increases in compressed air.
Gas density increases.
So you are taking more nitrogen than you'd take on sea level. 
Get it?

You know O2 and CO2 are metabolized... so they get their way out! ;)

BUT instead of being exhaled, however, the extra nitrogen safely dissolves into the tissues, where it remains until the diver begins his or her return to the surface!

On the way up, decompression occurs (in other words, the water pressure drops)
and with the change in pressure, the extra nitrogen gradually diffuses out of the tissues and is delivered by the bloodstream to the lungs, which expel it from the body.

If the diver surfaces too quickly, however, potentially dangerous nitrogen bubbles can form in the tissues. 
The precise reasons for bubble formation remain unclear.

These bubbles can compress nerves, obstruct arteries, veins, and lymphatic vessels, and trigger harmful chemical reactions in the blood.

Treatment: Decompress again and recompress slowly in a recompression chamber.
Also give hyperbarric oxygen therapy.

So next time you go underwater, beware! :P
Come up slowly.

That's all! :)

Thank you so much for reading ^_^


Saturday, November 5, 2011

Ondine's curse

̉Do you know that the voluntary and automatic control of respiration is seprate?

Sometimes the automatic control of respiration is disrupted without loss of voluntary control :O
And this clinical condition is know as Ondine's curse!

Lemme tell you a German legend.. Once upon a time, a water nymph, Ondine, fell in love with a human being (aww!)

Nymphs are immortal and they never age, unless they have a child with a mortal. Ondine gave up her immortality for this guy (Lawrence, his name.)

She starts to age and loses her beauty. Lawrence is no longer in love with her.
Ondine finds out Lawrence cheated on her! She sees him in the arms of another woman! :O (That bastard, I know!)

Just like the women of twenty first century.. Ondine was a vindictive one!

She curses Lawrence saying "You swore faithfulness to me with every waking breath, and I accepted your oath. So be it. As long as you are awake, you shall have your breath, but should you ever fall asleep, then that breath will be taken from you and you will die!"

To make it simple for all my medico friends.. It translates to the curse took away all his automatic functions and in this state, he could stay alive only by staying awake and remembering how to breathe.

To all those who are still wondering how this sad love story ends.. He eventually fell asleep from sheer exhaustion, and his respiration stopped.

Patients with this intriguing condition generally has bulbar poliomyelitis or disease processes that compress the medulla. Or it may be genetic.

Remember: The pathways for voluntary control pass from the neocortex to the motor neurons innervating the respiratory muscles, bypassing the medullary neurons!

That's all about Ondine's curse ^_^
Thank you so much for reading :)


Friday, November 4, 2011

Supination and Pronation of Forearm

Hello lovely folks!
Lets learn something from superior extremity.. supination and pronation!
They occur at the superior and inferior radioulnar joints
They are pivot type of synovial joints
It is the rotatory movement of forearm around a vertical axis
The axis passes from the head of the radius above to the ulnar attachment of articular disc below
The axis is not stationary because the lower end of ulna moves backwards and laterally during pronation & forwards and medially during supination

Let's consider pronation
In the movement of pronation, the head of the radius rotates within the annular ligament
Whereas the distal end of the radius with the hand moves bodily forward [pronate your hand and see]
The ulnar notch of the radius moves around the circumference of the head of ulna
In addition, the distal end of ulna moves laterally
If it didn't your hand wouldn't stay in line with the upper limb and would probably displace medially [You dont want that, trust me! :P]
Supination is the reversal of this process

We have two pronators and two supinators
Pronator teres and pronator quadratus, as the name suggests, for pronation
Supinator and Biceps Brachi for supination
[People usually forget to mention biceps brachi, which is really lame, its an important and awesome muscle!]

That's all for today
Thank you so much for reading! :)


Wednesday, November 2, 2011

Peritoneal ligaments of liver

Hey guys.. Wanna learn about the peritoneal ligaments of liver?

They support our liver.. Along with the hepatic veins draining into the Inferior Vena Cava and tone of the abdominal muscles.

My handwriting is really sucky.. So lemme just help you read =D


The falciform ligament ascends from the umbilicus to the liver.
It has a free margin that contains ligamentum teres.

It passes to the anterior and superior surface
and splits into anterior coronary ligament and left triangular ligament.

The right extremity of the coronary ligament is known as the right triangular ligament.
The pertioneal layers of the coronary ligament are widely separated and leaves an area devoid of peritoneum - bare area of the liver.

The lesser omentum arises from the edges of porta hepatis and fissure for ligamentum venosum
and passes into the lesser curvature of the stomach.

These are from my notes.. They are really bad.. *embarrassed*
I uploaded them anyway..

Thank you so much for reading =]


Lymphatic drainage of the tongue

The anterior part of the tongue tends to drain into the nodes farthest down the deep cervical chain (See diagram) ^_^
Anterior two thirds drain unilaterally
Posterior one third bilaterally
That's all you need to know! :)


Extrinsic muscles of the tongue

Extrinsic muscles of the tongue
This is a really cool diagram to explain the tongue..
You can see three out of the four extrinsic muscles here..
Lemme tell you about them! ^_^

Origin: From tip and anterior surface of the styloid process
Insertion: Into the side of the tongue
Action: So what'll be its action? Its pulling the tongue to its origin.. ie behind
Hence action will be retraction of tongue

Origin: Greater cornua and lateral part of hyoid bone
Insertion: Side of the tongue
Action: Think.. Pulling the tongue downward, towards the origin.. Hence, depression of tongue

Origin: Upper genial tubercle of the mandible
Insertion: Forms bulk of the tongue
Action: Protrudes the tongue.. [Pulling towards origin, remember?]

Sorry guys.. I don't have a diagram for this muscle.. Will upload soon!
Origin: Oral surface of palatine aponeurosis
Insertion: Descends into the palatoglossal arch to side of tongue at junction between oral and pharyngeal parts
Action: Elevation of tongue

Nerve supply
I have shown the nerve supply.. Its hyoglossal nerve.
Except for palatoglossus.. which is supplied by the vagus and cranial part of the accessory nerve (CN XI) that travel via the pharyngeal plexus

I just love this diagram.. Shows the muscles properly with the nerve supply.. and it's really cute.. So do make the diagram in your exam, it's really easy! :)
So basically you can remember the origin and insertion through the diagram.. I'll elaborate on palatoglossus with the muscles of the palate.. That's all for the extrinsic muscles!
Thank you so much for reading!

Pray that I do well in my exams =)


Related topic: Innervation of the tongue, palate, pharynx & larynx with mnemonic