Brains II

The

uh…

Brain 2

W by Aridi

hat this book is not:

There is no substitute for a subject specific book when learning about the brain. However, and typically, the illustrations are too few and too minimalist to convry the actual complexity of this subject. Use this to enhance the visuals that your source is lacking. Except where otherwise noted all illustrations for this library of books are by Dr. Roy M. Nuzzo, MD [by hand or CAD]. The basic anatomical CAD form is by Zygote R All rights are reserved CR 2024 & prior.

Skull dome removd showing the right cerebral hemisphere. 2 external planes: 1. eye pupils to ear canals 2. tip of nose to ear canals. Behind ear (mastoid) SCM = sterno cleido mastoid muscle. C1 atlas C2 odontoid

Landmarks externally help visualize the inner relationships. A rod from ear canal to opposite ear canal is not obvious in this side view but seen in some that follow. Here C1 & C2 are seen poking out just behind the upper STM which runs from the sternum to the mastoid emenence just behind & below the ear. Notice how a level plane from nose tip to ear canal passes just above the nasal/oral palatte.

Looking along the upper plane (pupils) at the lower (nasal tip) and seeing the ear to ear canals line. The lower SCM shows the ‘C’ [cleido = clavicles] better. A double lower connection to sternum and clavicles. Begin to color code brain (left side) by what it does.

From front to back Think Do Feel Compare relate & select See On side Remember and emote (toward center).

Here, the right temporal lobe is gently pulled outward to see a portion of the brain deep to it = the “insula”. Also note that the carotid artery is seen coming into the skull through a foramen in line with one in C1 (atlas). Travels in along the insula to emerge over the top edge of the temporal lobe as made visible here by pulling the temporal lobe away from its more medial resting place. A blockage of the artery in the neck will damage far more brain than blockage of that blood path higher up.

Brain stem from upper spinal cord to pyramids just inside the Foramen Magnum Two egg shaped thalamus sides are at the top Red nucleus peeking out below the left thalamus. The trigeminal thick arms reach forward with fingers of the branches covering most of facial sensation.

Looking from inside we see the shallow 4 th ventricle whose roof is cerebellum and sides cerebellar peduncles. The 5 th cranial nerve nuclear components ring the floor of this ventricle.

We can see the embryonixc early tubulation plane quite well here. In conditions of slowed infolding the eyes are wider apart. Theere may be clefts of the palate. The incompletely infolder 4 th ventricle looks like a cystic enlargement of the tubular canal and is often described as Arnold Chiari cyst.

Arnold – Chiari malformation (tubulation was too slow & incomplete) Often associated with missing corpus callosum at least posterior portion or more. Optical functional properties can be altered by the missing L=>R=>L.. information exchange.

The lower cerebellum ‘herniates’ (protrudes downward through larger foramen magnum than is normal. Corpus callosum defects vary, but

wide nasal bridge with eyes wider apart is a common clue.

Hemiplegia?

In an adult, a PURE motor hemiplegia (sensory spared) is nearly always from midbrain (vascular or other) and further refined by if other abnormal things (facial) are on same side ( higher before sides cross) or on the opposite side (below the crossing). Also note that the “Circle of Willis” is only a circle ON AVERAGE (lumping humanity in a single image). Typically it is “C” shape with a token narrow connection to form a full circle. The variability accounts for the variation of signs in many vascular distributions – especially in vaso-spasm syndromes.

Notice the plane through the pupils passingright along the base of the skull through which the olfactory (smell) jellyfish tentacle-like sensory endings penetrate a cluster of bone (ethmoid plate of skull). A fore-aft jolt can easily shear them leaving the victim without any sense of smell. Also notice that this FIRST Cranial Nerve - to the anatomy purists - isn’t a ‘nerve’ at all but part of the brain itself. So much so that any memory tied to smell has a direct connect to memory and especially to good/bad memory. That makes perfume $$$$!! & phermones… Head shake or hit and two black eyes? Loss of smell and runny nose = cerebrospinal fluid!!!!!

A closer look deep to the temporal lobe by removing it. Ouch? The blue portion surrounded by white matter is the RIGHT ventricle (1 st or 2 nd – nobody seems to know). We see the middle cerebral branches branching fore and aft to then emerge to cover the brain surface, tree-like. The insula has (more or less) 3 gyrus-like parts as \ | / and is the least mapped brain region. For sure sympathetic & parasympathetic control & reception are here as is taste (telling fresh from rotted food) … But, ?? risk reward also seems to live here along with BALANCE via vestibular input.

Insula damage is associated with apathy. Sex desire? Damage here loses swxual attraction along with taste. Is this why mating involves dining??? Fear, disguist, inner feelings also get affected here. What is most interesting, is that some have asserted that annorexia nervosa lives here. Interesting, as all the bits of that are at play. As a surgeon, I was called to place a feeding tube into a 14 year old girl who looked like a corpse in a war film. Beyond skeletal with multiple spinal collapse fractures, sunken eyes. Given a mirror she described what she saw as being fat and discusting, an impossible description of reality. Yet, she could judge relative states of health of those around her. To a surgeon, that goes beyond psychological to being an organic defect in Vomiting with hearing things not heard by others in insular seizures (some, not all). Documented (electrical) insular seizures can mimic seizures in other brain locations [?? by spread or ??]. Drug unresponsive seizures are very suspect as insular in origin. Choking feelings, There are known genetic things, and weird MRI, SEEG, PET and other stuff that makes this the property of very specialized clinicians with access to some far out technologies. The insula is the top of the embryonic brain before the huge outgrowth and curvature which in C-shape covers it as is seen in the mature structure. As if a ram’s horn grows curved & gets very fat to obscure the rams’s head (the insula in this metaphore). You will note that many wel known brain tracts and structures follow this curve as they were dragged along this pathway of developmental growth. the main circuitrym maybe a seizure like focal glitch? Addiction also seems to live here, at least sometimes.

Outer right hemisphere substance removed: In blue we see the lateral (right) ventricle C_ shaped fluid filled space with the lower portion out laterally flowing into the temporal lobe. Looking from this side we see within the ‘C’ a midline portion (the third ventricle). The ventricles were named by Rocky Balboa, as right, left, 3 rd , & 4 th .

Up and down traveling spino-cortical and cortico-spinal tracts pass medial to the lateral ventricle lower arms and lateral to the upper part. Tucking into the apex of the lateral ventricle curve is the hyppocampus and so following that same contour a series of parts called collectively as the ‘limbic system’.

Ventricles seen at other angles. Notice “limbic structures looping in the embrace of the inner ventricular contourfrom forward medial to eventually the temporal lobe. The amygdala connects at the end of that contour.

In the beginning… things happened, and then…

An egg (without a hard shell) implants in the womb.

Peeking inside the flexible egg bubble (amnion etc) we see an oblong disc wide at the head end and narower with an indentation becoming a slit from what will be low back to toes (represented here by a skeleton face down).

Cutting egg thingy and the early embryo (that’s its name) longways and looking from side we see that the disc had more going on. The backside surface is called ectoderm (the outer derm). We see deep to it a yolk whose membrane against the disc is the endo derm (inner or deep derm). Q: What’s a derm? A: A layer. Isn’t there supposed to be 3 layers? Well some of that infolding slit crawls between the other two layers and gets the name mesoderm (middle layer). It especially crawls between but around a long thin string that runs the whole length between endo & ectoderm. The long string-o-derm? No. The notocord. The notocord behaves like an orchestra conductor telling all cells what they are to become how to behave. Ectoderm, you will be skin and nervous system. ?? Isn’t nervous system supposed to be INSIDE? Yes, but we start with a generality and that development happens a wee bit later. For now just a long longitudinal thin strip is nervous tissue. The rest is skin? No, well, mostly, but where the two touch will be a transitional thin boundary which will eventually connect both. The’neural crest’ will be nerves and things that go from skin to spinal cord to brain. It will also migrate to serve the new middle of the three layers as well.

As the infolding lower line now a groove (neural groove) develops the upper head end (bigger than the leg end) also becomes a deep groove affair but more by outgrowth expansion than by downward plunge. From end to end we have an ectoderm strip that is now U shaped. Middle of the tube joins the U at the back surface to form an O. That joined bit begins a zipper process that turns the ectoderm into a tube. In the process that mesoderm has been forming along the sides of the ectoderm/notocord as segments (shown above a muscle color but there is still ectoderm (the skin part) covering it. This muscular segmentation is between the slices Skinand endoderm. Doesn’t the endoderm get to play in this symphony? Yes. Again the notocord tells the nearby endoderm to form gut. (not lip nor butt, but all rest between). [mostly, kinda sort of].

Above are a few moe angles of view with a cross section of events so far. On right notice that muscular mesoderm is capturing within it’s domain a part of the yolk. The boundary is called THE BELLY BUTTON.

Or, if you are a Roman living in 40 BC, the umbilicus. Needs flexibility as growth is going bonkers at this point. The umbilicus elongates to be the umbilical cord. Yolk portion

gets less as a substitute nutrition source takes over with veins and arterial delivery. That needs a pump – the heart [beginning as a pulsing artery] and blood to deliver the oxygen required.] Meanwhile the segmented head end is beginning to look more and more like ancient fish, which were eel-like in many ways.There were slits for water flow between the segments (making those segment slits called GILL slits and the tissues between the gill arches. Only some go so far as to make a full slit, but there is a good correspondence arch by arch. Many fish detected vibration with their jaw structure. We use the same corresponding bones as the three inner ear bones of hearing – hammer, anvil, and stapes). They have muscles that can tune what sounds get through easiest. Human speech is the center of that tuning. New mothers are tuned exactly to infant crying and hear it regardless of noise levels.

About this zippering into a tube. Proportionally massive growth is also ongoing. This needs a whole lot of DNA production as cells are dividing exponentially. Folate insufficiency is a serious risk to zippering if the mother is on a trendy diet, or staying esthetically thin without regard to what is actually in the diet.

The dietary defect does its damage well before the mother is even aware that she is pregnant. What a heck of a time for common dietary psychological problems! Drug experimentation? Too nasty to illustrate, for me anyhow…

The surgeon’s diet? Only good stuff of every color every day.

Back to brains.What was the bump at the head end of the neural groovr/tube begins to grow like crazy but confined by head size needs to fit within.

That brain growth is up and out then down and under very similar to ram’s horns. The space of the groove travels with this arcing swelling growth as the two sides fuse. The original central space is the third ventricle. The dragged ram horn hollow centers become the left and right ventricles.

Nerve pathways that were forming get dragged along this path as the lead end wraps around wide of the original growing region to become the temporal lobe. There are differing chemistry types to different system functions that optimise and segregate those functions. So the chemistry also follows the ram horn brain & ventricle formation (BELOW: left upper white path is cholinergic – for example).

Above, we see the generality of function by area. But remember that outer surface inward there are layers of organization that ASSOCIATE or negate other thingd elsewhere. The primary motor area is kind of misunderstood. Although any point is associated a body point location, the determination is from an average of a wider fiels. Like pointing a flashlight, the center of what is lit is what is wanted. Redundancy averaged is a mechanism to negate noise (an aberrant signal gets ignored).

Also note a functional attraction to location. The actual sound locus has a make a sound (lips tongue) nearness nearby in the motor area and is surrounded by interpretive cortex. Close by is the parieto-occipital-temporal area which has to deal incoming actual sound cards to the various players that are playing at the table. Deeper are connections to emotional related interpreters (limbic complex).

Memory gets connections as does what sound go with what thoughts and which words, if spoken, convey that.

Light capture signals from the eyes cross in the optical sorting place (optic chiasm) such that regardless of which eye, what is on our right is seen in the left posterior optic) cortex (upside down) and the side reverse for left field of view ==> right. The pituitary, sits below the optic chiasm. A pituitary tumor will have progressive loss of lateral fields of vision on both sides.

From eyes to visual cortex the optic chiasm closely huggs below the thalmus which has a posterior bump to sample some of the optical input. That in turn goes to a more medial bump superior colliculus in the most forward brainstem mid btain.Information is passed to the medial longitudinal fasciculus (the mess of goobers seen above (within the brainstem). This has the job of coordinating eye focus and convergence on what is of interest. This complexity underpins “blind sight” where a totally blind person can startle at something not seen but somehow sensed.

The auditory mechanism which includes vestibular input also gets represented in this mish mosh of - where am Iand who is that?

The thalamus sits in the pivotal area by several criteria. A seldom (if ever?) discussed thing is where does ‘ me ’ live? Problems as you go lower than the cluster of nuclei interacting with the thalamus seem to the individual to be happening TO them.

There’s something interfering with my

ability to [whatever]. Focal problems approaching this part og the brain is “the way I am”. This can go to the extreme as not even acknowledging there is anything amiss. In dystonias it can be extreme agitation to being made “better”.

The thalamus is most dependant on the posterior cerebral artery.

Midbrain Dorsal view

Pineal

Superior Colliculi

Inferior Colliculi

Caudate nucleus follows the ventricle into the temporal lobe.

Here we see an inner set of thin surfaces which divide up the thalamus [? Thalamisses? Thalamice? Thalami? The plural of Salami is not Salamus. Hmmm. ] There are two of them, one right the other left. Can’t donate one side to anybody, though. Pretty essential.

THALAMUS:

Posterior

Top, looking down Anterior

From the left side looking up and forward at the left mostly lateral part and the right thalamus mostly medial part.We see the nuclei postions in color (no rainbows were injured to colorize these thalamic structures.

In the top half up front, the anterior nucleus has many cingulate gyrus PATHWAYS going both ways. Below that we see the ventral anterior nucleus (yellow), the ventrolateral nucleus (red), then the ventro posterolateral nucleus is in the back (these are all lateral). Two bumps at the back the geniculate nuclei Lateral is the [optical, SEEN IN GRAY] lateral geniculate which send along to the midbrain superior colliculus. More medial to the last are the medial geniculates which communicate with the inferior colliculli (auditory) on the mid brain just distal to the visual superior coliculi. On each of the medial surfaces – more forward - is the dorsomedial nucleus. Then behind that the large “pulvinar”(light blue”). The pulvinar is the largest portion of the thalmus. It can be amiss in blind sight. It also figures in visual attention. OK – a visuar thingy. But it has something to do with social recognition and sensibility. It juggles the various senses to establish a consensus of the senses. This includes getting attention to what is playing in the visual cortex. Somehow schizophrenia, autism, and prion disorders.

Cingulate gyrus

Lateral spino-cerebellar tract

Left cingulate gyrus

Cingulate gyrus

Caudate nucleus

Pituitary

Fornix Thalamic anterior nucleus

Amygdala

Pituitary – anterior & posterior

anterior thalamic nucleus in yellow

A left hypothalamic nucleus (green) pituitary to optic chiasm

from below: anterior thalamic nucleus (yellow)

pituitary to optic chiasm

Lamina terminalis & septum pellucidum

tract: mamillary-- anterior thalamic nucleus—fornix septal nuc to red nuc tract

cholinergic, basal forebrain complex (BFC)

dentate nuc to red and inferior cerebellum

Noradrenergic nucleus coeruleus

seroternergic raphe nuclei

angular gyrus

(green\blue) & supramarginal gyrus (highlighted in yellow)

cerebral peduncle [cerebral radiation] [internal capsule area when in horizontal x section] Here, simplified in rough gray branching

Source of the Vagus… Salivatory nucleus & nucleus ambiguous

Trigeminal CN Thalmus R & L

fornix amygdala

Fancy letters by Aridi

euro anatomy...

… for the amateur neurosurgeon

OK, put the butter knife down. We’re done. Did this book make you humble? [ ] YES [ ] NO [ ] What’s humble? *

*A famous NYC neurosurgeon in Central Park ran to and attended a fellow who he witnessed falling from a tree onto his head. As he checked the dazed fellow’s neurologic function – an approaching voice was firmly asserting “Step aside. I am a boyscout. Please step aside I am a boyscout.” he repeated putting his hand on the neurosurgeon’s shoulder. The neurosurgeon replied, “It’s OK, son, I am a scout master.” ------------- ------------- ------------- ------------- -------------