NEUROANATOMY NOTES 08/03/99
Profesor: Dr. Martinez Sandoval
Question: A hoarse voice, along with pain and temperature deficits in the left face and right limb would most likely be caused: External laryngeal nerve.
What neuron transmits the sensations in the body? Primary neuron in the dorsal root ganglion.
These micro/macroscopic structures that receive info are receptors. There are superficial and deep receptors. Superficial are the most abundant. These receptors are naked free endings. they are distributed in the entire skin. They are the ones that will receive pain, temperature, light touch. These are the receptors that usually, as an example, if you use a piece of carpet in different parts of the body, you are trying to stimulate the light touch. Or, if you shave in men, and women, and then you apply alcohol, you will feel pain immediately after you shave. Then, some men will feel a little pain. These receptors are the most abundant of all of them. So they receive pain, temperature. Then from the receptors you can take any of the terminals, branches from plexuses, or intercostal nerves, so if you are in the hand, you know that the hand, as you may recall the palm of the hand ,you have the medial nerve and ulnar nerve corresponding to C8-T1. You have receptors in the skin, and the stimulus travels through the medial nerve or ulnar nerve up the arm, and it enters the brachial plexus. If you are talking about the ulnar nerve, they enter the ventral ramus, C7-T1. Then the ventral rami becomes the spinal nerve, which then divides into ventral and dorsal root. Then in the dorsal root, you find the dorsal root ganglion. Then, these axons become central processes, or dorsal root which enters the spinal cord. These are the first neurons. So all first neurons are located in dorsal root ganglion, on both sides of the spinal cord.
For example, you are here in the patellar reflex, so automatically you think L2-4. These are the segments that will receive the propioception from the patellar tendon. So now what was the peripheral nerve that supplies the quadriceps muscle? Femoral nerve. So the pulse travels via the femoral nerve, which reaches the lumbar plexus. And we know that the levels for femoral nerve are the same: L2-4. So now the axons reach the ventral rami. And then spinal nerves. Lumbar spinal nerves. And then in the junction between dorsal and ventral roots. And then instead of ending in the spinal cord, they ascend. But there are some that just enter and leave the spinal cord for reflexes. Each of the ganglia has unipolar cell bodies, except: Which of the following least likely participates in the pain pathways? Which of the following cranial ganglia, participates in the pain, temperature pathways in the head. Sensory pathways are the trigeminal ganglion, which contains unipolar cells. And then the unipolar cells in the trigeminal ganglia will form the maxillary division, ophthalmic division, and finally the mandibular division. These all come from the main sensory root.
Trigeminal Pathways: These convey light touch from the head and there is a descending root in the descending nucleus of the trigeminal nerve. These convey pain, temperature from the head. Light touch to the main sensory nucleus in the pons. Descending nucleus in the pons, medulla, and spinal cord, for pain and temperature receptions. So, these are the first neurons, the ones related in the tirgeminal ganglion.
You have also, in the same way, in other ganglia, such as the geniculate ganglia which has unipolar cells with central processes that enter the CNS through the intermediate nerve. Peripheral processes for pain and temperature will be in the external ear. So this type of axon deals with a little bit ofpain and temperature for the external ear (GSA), although some authors deny this.
Superior Glossopharyngeal and superior vagus ganglion: These lie immediately above the jugular foramen. Then the unipolar cells leave and send their peripheral axons, those in the glossopharyngeal go to the external ear also, and the middle ear principally. That is the typical tympanic nerve that we mentioned before. The central processes form the glossopharyngeal and enter the descending nucleus of V. The Vagus nerves send auricular branches to the ear, and central processes to the descending nucleus of V. All unipolar cells will receive peripherally pain, and temperature, and then the central processes, it doesn't matter if it is vagus, glossopharyngeal, or trigeminal, will send their axons into the descending nucleus of CNV. So in your capsules you should write, all pain and temperature by the head is received by the descending nucleus of the CNV. Which of the following least likely pertains to the GSA (Pain, temp) from the entire head? superior glossopharyngeal, superior vagus, trigeminal, geniculate, but not petrosal ganglion, which is for taste perception primarily. The petrosal ganglion is for GVA, SVA (taste) activities. The same as the nodose ganglion is primarily GVA, SVA also. What type of functional component is in the descending nucleus of CNV? GSA. The question is which of the following nuclei, represent the termination of the primary neurons that receive pain temp from the head? Descending nucleus of V.
He shows a picture of the cranial nerve nuclei in the brainstem. He colors the contralateral ascending axons from the CNV. But, ther will also be other axons leaving the nuclei, all acting as relays using second order neurons. The first neuron was in the peripheral ganglia. So now the desceding nucleus sends the contralateral axons via the trigeminal thalamic pathways. There are two: 1) ventral, and 2) dorsal trigeminal thalamic pathway. These pathways reach the posteriomedialventral (PMV) nucleus of the thalamus, which is a recipient of the SVA. So that receives pain, temperature from the head, and taste (SVA). So, now these neurons ascend through the posterior limb of the internal capsule and project and finish at the level of the cerebral cortex. Where? In the somasthetic area (3, 1, 2). In addition, to area 43, for taste projection. Area 43 that lies in the most inferior part between the precentral and postcentral gyrus.
Now you can see the other one here, from the main sensory nucleus, axons contra- and ipsi- lateral. Mainly crossing pathways. They ascend to the PMV nucleus of the thalamus. This represents the third order neuron of the trigeminal pathways representing pain, temp, light touch from the entire head. The mesencephalic nucleus is for propioception from tendons, muscles, joints. As we said before, the mesencephalic nucleus, which lies here, and he draws it on his transparency, it is in thepons, and reaches the midbrain. This was defined as the only exceptional nucleus, the only one, within the CNS that contains unipolar type of cells. Because all unipolar cells lie in peripheral ganglia, except mesencephalic nucleus. So now you can see the mesencephalic cells giving origin and leaving to the masticatory muscles, to the tensor tympani, temporal, masseter, med/lat pterygoid, mylohyoid, anterior digastric, tensor tympani, etc. The unipolar cells may, may, reach the eye, tongue, all muscles in the face. So the central process goes to other motor nuclei, such as the trigeminal motor nucleus, or you can see a collateral, that will go to the facial nucleus, ipsilaterally, however we can go contralaterally. So in this case, the unipolar neurons are found in the mesencephalic nucleus.
Question: A hoarse voice, along with pain and temperature deficits in the left face and right limb would most likely be caused:
A. Lateral medulla
B. Medial medulla
C. Lateral pons
D. Medial pons
What is the origin for the neurons that gives to the vagus and then to the superior and inferior laryngeal? Nucleus Ambiguus. He shows us a transverse section of the medulla showing us where the nuclei are located. The spinal lemniscus on the left of the brainstem, leads to an affected pain and temperature right side of body. You need to include the vestibular, dorsal motor nucleus, the solitary nucleus, in order to have all these alterations, nausea, vomting, vertigo, etc in addition to the signs/symptoms that we've mentioned.
Now you are here in the medulla again and we are looking at the question. Upper motor neuron lesion leads to babinski sign. You get sensory ataxia (loss of two point discrimination), loss of propioception, Rhomberg sign. So, the affectation of the medial lemniscus is very clear. The tectal spinal tract. This tract is the key tracct for the reflex movements of rotation for the head/neck. So, and finally the hypoglossal nucleus. The lesion of the hypoglossal nerve will cause the deviation of the tongue. None of that is referred to in this question. That is why we're not selecting medial medulla. Lateral pons. What do you find in the lateral pons? You are here in the lateral pons. He shows us a transverse section of the upper half of the pons. You can see the 3 trigeminal nucli (mesencephalic, motor trigeminal, principal trigeminal sensory). In the lower half of the pons, identify CNVI and CNVII nuclei. That is why we do not select lateral pons. What structures do I have in the medial pons? Corticospinal. Corticospinal means upper motor neurons. Spastic paralysis, areflexia, babinski sign. Spinal Cord C4-C5. So, there they are referred to the left face, and the spinal cord really has nothing to do with the head, only the neck down. The answer is: A. Lateral Medulla
Question: Examination of a patient reveals the following deficits on one side: loss of the gag reflex, loss of touch sensation over the posterior tongue, and loss of, and los of secretion from the parotid gland:
Examination of the gag reflex. Glossopharyngeal, and a bit of the vagus controls this. The tongue has ant, mid, post thirds and base of the tongue. Sensory, pain, temperature, and taste. Sensory of the tongue in the anterior two thirds, pain, temperature and light touch, belongs to CNV. What branch? Lingual nerve. The anterior two thirds of tongue is chorda typani branch of the facial. The glossopharyngeal controls posterior two thirds, and the vagus the base of the tongue. Taste is SVA.
I need to be sure that when you face the patient, how you are going to physically explore the tongue. You should know the difference between perception of pain versus perception of taste. All of these questions, the sensory and motor innervation of the tongue will be on the exam. So in that moment the posterior tongue is the glossopharyngeal and the vagus. So loss of sensation of the parotid gland. The glossopharyngeal auriculotemporal branch (parasympathetic secretion) supplies the parotid gland. Therefore, the answer to the qeustion is: glossopharyngeal nerve (CNIX).
Question: Your patient has difficulty speaking and loss of function in the right upper limb. Occlusion of which of the following arteries is most consistent with these findings? Wernicke's area (22, 44, 45) is affected. That is from the middle cerebral artery. Loss of the function in the right upper limb. What cortical areas suplly the limbs. The primary motor area supplies this is area 4. What artery supplies area 4? Middle cerebral artery.
A. right middle cerebral.
B. Right anterior cerebral.
C. Right posterior cerebral.
D. Left anterior cerebral.
E. Left middle cerebral.
The answer is E. The left middle cerebral artery.
If someone knows the answer, raise your hand.
Question: During an oral examination you observe that your patient's uvula deviates to the right. this may indicate damage to the:
A. Right glossopharyngeal nerve. No, no, no. It only supplies the stylopharyngeus, therefore, does not affect the uvula.
B. Left glossopharyngeal nerve. No.
C. Right facial nerve. No, nothing to do with the palate.
D. Left vagus nerve.
E. Right hypoglossal nerve.
The uvula is supplied by the vagus nerve. The right half is dominted by the left cerebral hemisphere. So the lesion of the corticobulbar will cause affectation to the contralateral side of the uvula.
Question: You would expect a tumor at the internal aspect of the jugular foramen to produce which of the following symptoms?
What cranial nerves pass through this foramen? CNIX, X, XI.
A. Hoarseness. Yes.
B. Nystagmus. No, because CNVIII involved.
C. Atrophy of the muscles of mastication. No, because CNV.
D. Vertigo. No.
E. Bell's palsy. Facial. No.
Match each structure with the correct statement.
A. Internal capsule.
B. Medial longitudinal fascuculus
C. Precental gyrus
D. Putamen
E. Superior temporal gyrus
F. Posterior commissure
G. Caudate nucleus
H. Oculomotor nucleus
I. Frontal eye field.
In horizontal sections of the brain, part of it appears to lie between the thalamus and the globus pallidus. The answer is: A. Internal capsule.
If you cut the medial longitudinal fasciculus the patient will be unable to control the horizontal gaze of the eyes. We will see this in the vestibular system.
Precentral gyrus is the site of origin for the motor neurons (area 4). Putamen is in the basal ganglia. It receives info from the cerebral cortex from all association areas of the cortex, and they are projected to the putamen. Superior temporal gyrus contains which areas? Area 41, 42, 22. This is the primary auditory cortex, part of wernicke's area.
Posterior commissure is the smallest commissure of the brain. Largest is corpus callosum. Second is fornix. Third is anterior commissure. Smallest is posterior commissure. This connects the two superior colliculi. The anterior commissure connects the two temporal lobes. Fornix is for the limbic system. Corpus callosum is for inter-cerebral connections. you are projecting left half area 17 to right half area 17.
Caudate is in the basal ganglia. Recieves sensory information. We will discuss the basal ganglia later.
Oculomotor nucleus is for the movement of the eye. Rises, elevates, depresses, adducts eye, opens and closes the palpebrae fissure. It contains the axons to present pupilary constriction.
Frontal eye field. The voluntary control of the bilateral movements of the eyes. Voluntary lateral conjugated movements of the eyes. This is area 8.
Question: Contains fiber projections from the abducens nucleus going to the contralateral oculomotornucleus. This is one of the activites of the medial longitudinal fasiculus.
Question: Contains the primary sensory cortex for the auditory pathway. This is the superior temoral gyrus.
Question: Compression of the nerve coursing through this opening would affect the muscles of mastication? This is the trigeminal nerve, mandibular branch, which passes through the foramen ovales.
Question: Trauma to this area could result to leakage of cerebrospinal fluid into the nasal cavity? Cribiform plate of the ethmoid bone. Don't forget this, you may have weakness in your internship in the fractures of this area, because of car accidents, which may cause fracture to the cribiform plate. The patient may complain of the constant common cold. There is an unusual quality of the mucous. This is not mucous, but cerebrospinal fluid dripping through the cribiform plate, which could cause acute meningitis.
Now you are facing reality. This is the type of drawing that you will have in your examination. So very easy, as you can see. This is a transverse section of the midbrain.
Question: Motor supplied to the levator palpebralis. This is the oculomotor nerve. You can see Edinger Westphal nucleus. You can also see the central nucleus of Perlia, which is the convergence center, for the convergence of the eyes. Medial geniculate nucleus is here also. So you must first identify the structures, then what do they do, then what happens when there are lesions.