Hello everyone. So I've not been active at all lately , cause Final Year ! Pretty depressing 🙄. Anyway. Here's a post about the nerves and what we need to know for clinical application!
Nerves
So Erlanger and Gasser classified the nerves into A, B and C based on Myelination and size.
So you have :
A
(Which has Alpha , Beta , Gamma , Delta fibres )
B
C
Out of these , the first 3 :
A - Alpha , Beta , Gamma = Large fibres which are largely Myelinated.
And next 3 :
A - Delta , B , C = Small fibres which are not Myelinated as much.
How I remember these fibres is as per evolutionary significance.
The least Myelinated fibres , which are the smallest are the ones all living creatures need. As we progress from C to B to A , we continue to gather more and more well developed and specialised fibres.
C -
The smallest fibres.
Least Myelinated.
Most basic fibres and most primitive from an evolutionary stand point !
Control sensations of Dull Pain and Temperature (Heat)
B -
Small fibres.
Low Myelination.
Next most Basic Instinct - Urination.
Controls your Autonomic nervous system.
Remember- B = Bladder
A Delta -
Moderately Small fibres.
Lower Myelination than other A fibres.
Responsible for sensation of Sharp pain and Temperature ( Cold )
Thus to summarize the small fibres -
We have C , B and A Delta.
Out of these
C and A Delta control Pain and Temperature
( where C controls Dull pain and Heat ; A Delta controls Sharp pain and Cold )
And B controls Bladder /ANS.
(How to remember A Delta vs C.
C is more primitive. Hence controls Dull pain. Sharp pain is a little more specialized and hence is controlled by the relatively more modern fibre - the A Delta)
Coming to the large fibres.
We progress from A gamma to A beta to A alpha.
A Gamma :
Large but smaller then Alpha and beta.
Myelinated but not as much as alpha and beta.
Responsible for muscle tone.
Remember : A Gamma = Gamma motor neuron which is responsible for tone.
A Beta :
Very large.
Well Myelinated.
Responsible for modern sensations like Fine touch, Pressure and Vibration.
A Alpha :
Largest.
Most Myelinated.
Responsible for Muscle Contraction and Most modern sense - Proprioception.
It's the Bomb of the fibres hence responsible for muscle contraction.
Thus , demyelinating diseases like Guillian Barre syndrome and CIDP would affect the fibres that are used to being Myelinated.
So your presentation in these diseases would generally involve loss of:
A Alpha - Motor + Proprioception
A Beta - Modern sensations of fine touch and vibration.
A Gamma - Tone
And Axonal Polyneuropathic Diseases like Metabolic or Post infectious ones would involve loss and abnormalities of -
A Delta - Sharp Pain and Cold
B - ANS
C - Dull pain and Heat.
Hope this was helpful !
Happy studying !
Stay awesome.
~ A.P. Burkholderia
Hello There!
So let's enlist few important points in relation to the ischial spines.
Ischial spines can be generally be palpated at about a finger-length into the vagina, at 4 & 8o'clock.
They are felt as bony prominences and their palpation may cause a little discomfort to the patient.
These spines serve as a landmark for:
1) Engagement of Fetal Head.(Most commonly used for determining the Fetal Station during labor.
Ischial spines are considered as Station0)
2) Internal Rotation of the fetal head.
3) Pudendal Nerve Block.
4) External os.
5) Obstetric Curve (J shaped) takes forward curve at this level.
6) Insertion of levator Ani.
7) Plane of least pelvic dimension.
8) Ring pessary is kept at the level of ischial spines.
These are the few things I know about at the level of the Ischial spines.
Do let me know some additional points you know of, to add to the list.
Let's learn Together!
-Medha.
Hello everybody!
Recently during my Ob-Gyn internship while delivering the placenta, the Umbilical cord that I held, was very lumpy bumpy. Little knowing about the reason at that moment, I came home found out the reason.
Let's see how the Umbilical cord can get knotty sometimes.
So there are two types of knots seen in the cord.
1)True Umbilical Knots
2)False Umbilical Knots.
True Knots :
These are noted after delivery.
The umbilical vessels, are protected by the thick myxomatous Wharton jelly, and can rarely be occluded completely. The jelly protects the vessels and the fetal blood supply, as there is only flattening or dissipation of Wharton jelly when a Knot is formed.
Due to the knot some amount of venous congestion distal to it and some partially or completely occlusive vascular thrombi may also be observed.
A true knot is formed when a loop of cord slips over the infant’s head or shoulders during delivery.
If the knot is pulled tightly it can cause fetal demise due to restriction of the circulation in the cord.
The True Knots can occur due to:
1)A long cord,
2)Large amounts of amniotic fluid
3)A small infant,
4)An overactive fetus
5)As a result of external version.
(All the above causes lead to increased fetal movements in utero)
However the fetal mortality rate associated with true knots is low.
False Knots:
In the cord the blood vessels are longer than the cord and are often folded on themselves producing nodulations on the surface of the cord. These nodulations are lumps and bumps I saw!
These have been termed as false knots.
So guys the next time you see a lumpy bumpy cord, unlike me, you now know the reason.
That's all, on the Umbilical cord and it's knots.
Let's learn Together!
-Medha.
Hello everybody!
In this post let's quickly learn about Terson Syndrome.
So what is it?
This Syndrome is a combination of intraocular and subarachnoid haemorrhage secondary to aneurysmal rupture, most commonly arising from the anterior communicating artery.
Terson Syndrome along with other bleeding disorders is included amongst the Systemic causes of vitreous hemorrhage!
Intraocular haemorrhage is also seen to occur with:
1)Subdural haematoma
2)Acute elevation of intracranial pressure
The mechanism of intraocular bleeding:
There is increase in cavernous sinus pressure due to the subarachnoid/subdural hemorrhage leading to stasis in the retinal veins. This stasis in the retinal veins leads to increased intraluminal pressure in the veins making them susceptible to bleed.
The haemorrhage is often Bilateral.
Typically intraretinal and/or preretinal. With this hemorrhage there is a possibility of it leaking in the vitreous.
The vitreous haemorrhage usually resolves in a few months and the long-term, the visual prognosis is good.
I hope you guys found it useful. Do let me know about some neuro-opthalmology syndromes you know about.
Let's learn Together!
-Medha.
Hello everybody!
Let's today learn about cerebellum and how amazing it is.
So all of us know that walking, swimming or typing needs conscious effort while being learnt for the first time, but after learning, one can continue these activities mechanically without having to think about them.
After learning, the responsibility for these activities seems to shift more and more to the cerebellum leaving the cerebral cortex free for other tasks.
That is why a child who is learning to walk has to put all his mind into it. Any distraction may make him fall. But as adults we can multitask along with walking.
Let's see how this happens.
There is evidence that cerebellar circuits can undergo functional changes as a result of experience.
The climbing fibres play an important role in this process. (bring information only from the inferior olivary nuclei, and establish excitatory synapses with Purkinje cells)
In a new situation, the climbing fibre activity is high, and it tends to reduce mossy fibre activity.
(Mossy fiber excitation not only stimulates Specific Purkinge cells but also inhibits the neighbouring Purkinge Cells.)
On repeated exposure to stimulus while learning, the mossy fibre response gets stabilized at the low level without an increase in the climbing fibre activity and the Cerebellar efferents perform the function semiautonomously on stabilized afferent input.
Thus Cerebellar learning may spare the cerebral cortex in the learnt movements.
I hope this was informative.
Let's learn together!
-Medha.
