স্পেশাল বিসিএস (স্বাস্থ্য) - লং কোর্স

Structure seen through opthalmoscope:
1.Optic Disc
2.Retina
3.Blood vessels
4.Macula

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Lateral Rectus Muscle is supplied by Abducens Nerve
 
Functions of Facial Nerve
Main: Motor innervation to muscles of facial expression (SVE)
Others:  1.Taste innervation of anterior two-thirds of tongue and palate (SVA),
               2. parasympathetic innervation of lacrimal, nasal, palatine and salivary glands (except parotid) (GVE),
               3. sensation to parts of auricle and retroauricular region (GSA)

Snell 8th -351

In penile erection initial penile vascular engorgement ias controlled by PNS part of ANS( S2,S3,S4 segments of spinal cord)

Erection and ejaculation
Erection and ejaculation are regulated by the autonomic innervation of the penis. The parasympathetic stimulation is excitatory for the penis, as it causes the erection. The parasympathetic stimuli relax the smooth musculature of the corpora cavernosa and produce vasodilation in the helicine arteries. The helicine arteries then fill the corpora cavernosa, compressing the venous outflow from the penis. This process is called the veno-occlusive mechanism and it results with penile erection.

On the other hand, the inhibitory sympathetic stimuli cause the ejaculation when the critical level of sexual excitement has been reached. The ejaculation process can be divided into two phases. In the first phase, the sympathetic stimuli cause the vasoconstriction of helicine arteries, contraction of the smooth muscle cells within the septa of corpus spongiosum and contraction seminal vesicles and prostate. This results in accumulation of seminal fluid into the proximal part of the urethra. During the second phase, the bulbospongiosus muscle contracts  and expels the seminal fluid through the urethra (ejaculation). When the ejaculation is finished the penis returns into the flaccid state. An individual normally produces 3-5 ml of semen per one ejaculation which contains about 300 million sperm cells.

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The falx cerebri is Largeset dural fold which seperates two separtes two cerebral hemisphere

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 Falx cerebri: separates left and right cerebral hemispheres. Located in the longitudinal cerebral fissure
- Tentorium cerebelli: Separates the cerebrum from the cerebellum
- Diaphragma sellae: Forms a lid or roof over the hypophysial fossa of sphenoid, covering the pituitary gland.

The interpeduncular fossa
infront by the optic chiasma,
behind by the antero-superior surface of the pons,
antero-laterally by the converging optic tracts,
postero-laterally by the diverging cerebral peduncles.

Blood supply of macula:

1. Posterior Cerebral Artery
2. Middle Cerebral Artery

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Proprioceptive sensations include
•       Position sensations
•       Pressure sensation from the bottom of the foot
•       Sensation of equilibrium
•       Tendon & muscle sensation

In adult humans who are awake but at rest with the mind wandering and the eyes closed, the most prominent component of the EEG is a fairly regular pattern of waves at a frequency of 8–13 Hz.

This pattern is the alpha rhythm. It is most marked in the parietal and occipital lobes and is associated with decreased levels of attention. A similar rhythm has been observed in a wide variety of mammalian species.

During sleep:
1. Pulse & RR decreases
2. BP falls
3. Tendon relex lost

Loss of ankle jerk with extensor planter response
•       Subacute combined degeneration of spinal cord
•        Friedreich’s ataxia
•       Taboparesis
•       Multiple sclerosis
•       DM with cervical myelopathy.

Tabes Dorsalis morphology:
DORSALIS
1. Dorsal column degeneration
2. Orthopedic pain (Charcot joints)
3. Reflexes decreased (deep tendon)
4. Shooting pain
5. Argyll-Robertson pupils
6. Locomotor ataxia
7. Impaired proprioception
8. Syphilis

Argyll Robertson Pupil (ARP):
Hallmark of neurosyphilis
1. Light-near dissociation (no reaction to light but brisk response to near).
2. Both pupils usually involved, but the degree may be asymmetrical.
3. Pupils are small and frequently irregular in shape.
4. Pupils dilate poorly after instillation of mydriatics.
5. To make a diagnosis of ARP vision in the affected eye must be normal.

Special points Regarding blood supply of spinal cord
1. Anastomosis is least efficient at the region of lateral columns
2. Cervical and lumbar segments have rich vascular supply
3. T1 to T4 segments are most vulnerable to ischemia
4. Anterior spinal artery thrombosis causes ischemia of anterior 2/3rd of the cord, sparing the posterior column, hence leads to dissociated sensory loss.

Nerve cells in the anterior gray columns
• Large & multipolar and  Axons pass out in the anterior nerve roots as a-efferents
• Smaller nerve cells are multipolar and Axons pass out in anterior roots as y- efferents

Pain Initiators
• Glutamate - Central
• Substance P - Central
• Brandykinin - Peripheral
• Prostaglandins - Peripheral
• Aspartate
Pain Inhibitors
• Serotonin
• Endorphins
• Enkephalins
• Dynorphin
• GABA
• Glycine

Spinal Nerve:
1.They are 31 Pairs
2. Formed by Union of anterior and Posterior Nerve roots
3.The posterior ramus contains both motor and sensory axons
4. The anterior ramus contains only motor axons

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Conduction velocity:
1. It is the speed at which motor and sensory impulses traverse a given segment of nerve (meter/sec)
2. Larger axons & proximal segments conduct faster than smaller ones & distal segments.
3. New born infant's nerves have slower velocities than adult.
4. CV in UL is faster than in LL
In elderly there is slowing of conduction,
in local tissue temperature slows CV.

Isotonic Contractions
Isotonic contractions maintain constant tension in the muscle as the muscle changes length. This can occur only when a muscle’s maximal force of contraction exceeds the total load on the muscle. Isotonic muscle contractions can be either concentric (muscle shortens) or eccentric (muscle lengthens).

Isometric Contractions
In contrast to isotonic contractions, isometric contractions generate force without changing the length of the muscle . This is typical of muscles found in the hands and forearm: the muscles do not change length, and joints are not moved, so force for grip is sufficient. An example is when the muscles of the hand and forearm grip an object; the joints of the hand do not move, but muscles generate sufficient force to prevent the object from being dropped.

Myelinated Nerve Fibre:

1. The nerves that are insulated by a sheath or myelin called myelinated nere fibre.
2. These are made up of lipid & protein and so, appear white.
3. These have nodes of Ranvier which always constant in number.
4. Nerve fibres outside CNS and myelinated.

Non-Myelinated nerve fibre:
1. The nerves which lack such sheath are called non-myelinated nerve fibre.
2. They appear grey because of absence of myelin sheath.
3. They do not have node of Ranvier.
4. Post-ganglionic sympathetic nerves are non-myelinated.

1 Nerve Fibres served by Cell in Peripheral Nerve

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The peripheral nervous system refers to the parts of the nervous system that are outside the central nervous system, that is, those outside the brain and spinal cord.
Thus, the peripheral nervous system includes
The nerves that connect the head, face, eyes, nose, muscles, and ears to the brain (cranial nerves)
The nerves that connect the spinal cord to the rest of the body, including the 31 pairs of spinal nerves
More than 100 billion nerve cells that run throughout the body

There are three foramina present in the greater wing -
a.the foramen rotundum,
b. foramen ovale
c. foramen spinosum.
They conduct the maxillary nerve, mandibular nerve and middle meningeal vessels respectively.

Diagnosis requires patient history, neurological examination and medical imaging
Magnetic resonance imaging is considered the best imaging modality for Chiari malformation
Diagnosis of Chiari type II malformation can be made prenatally through ultrasound (J Neurosurg Pediatr 2015;16:159)