Basic Neuroscience Exam 2

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Normal body temperature range

97 F - 100.4 F

Arterial-venous malformation: connection from brain artery directly into a vein without any intervening capillary beds, that becomes a space occupying lesion "Serpentine coils of vessels" - susceptible to hemorrhage

A patient presents with headaches. Imaging is attached. Diagnose.

Urge Incontinence

A state in which a person experiences involuntary passage of urine that occurs soon after a strong sense of urinary urgency (inability to delay voiding) Cause: detrusor hyperactivity, hyperactive micturition reflex ◦ Overactive bladder ◦ Irritation: cystitis, stones, bladder cancer ◦ Stroke, MS, Alzheimers, Parkinson's, Spinal cord injury → leads to a micturition reflex that is hyperactive (bladder fills to a low level, and then automatically empty)

Wher are the preganglionic parasympathetic cells bodies located?

"Craniosacral region" ◦ Brain stem ◦ IML-like area of the sacral spinal cord

Kluver-Bucy Syndrome

A syndrome due to bilateral lesions of the amygdala which results in: ◦ Agnosia: visual, tactile and auditory (does not recognize objects by sight, touch or hearing). ◦ Hyperorality: examining objects excessively by mouth ◦Hypermetamorphosis: intensively exploring the immediate environment ◦ Placidity: no fear and anger ◦ Hyperphagia: may even eat objects that are not food ◦ Hypersexuality ◦ Amygdala lesions may be associated with temporal lobe lesion - amnesia, dementia or aphasia

Subclavian Steal syndrome

A syndrome which arises from the occlusion or stenosis of the Subclavian Artery proximal to the vertebral artery, resulting in a pressure difference of blood flow through the vertebral arteries. Since pressure will be lower in the subclavian artery distal to the occlusion, blood will flow from the vertebral artery into the subclavian artery instead of into the basilar artery, essentially "stealing" blood from the basilar artery. The Basilar artery is responsible for supplying blood to the posterior circulation (pons, cerebellum, midbrain, and thalamus) and decreased blood flow can lead to strokes anywhere in the posterior circulatory region.

How does an injury above the Lumbo-sacral spinal cord effect micturition?

Bladder will act similar to a skeletal muscle that has seen an upper motor neuron injury Initially, there will be shock, and the bladder will be flaccid and areflexic. Then, days to weeks later, the bladder becomes spastic and hyperactive with increased tone and decreased capacity (bladder filled to a low level and then reflexively empties- similar to an urge incontinence)

What is the blood supply of the Thalamus and what does an infarct result in?

Blood Supply: Posterior Cerebral Artery (PCA) Infarct: results in damage to the VPM and VPL, causing pure sensory symptoms ◦ Contralateral loss of all sensation (face and body) ◦ Lateral geniculate body → contralateral homonymous hemianopsia ◦ Possible Ataxia → motor circuits from cerebellum run through here ◦ Normal reflex and strength ◦ No Babinski Sign → corticospinal tract uneffected

Pathways of the baroreceptor reflex

Carotid Sinus contains baroreceptors and chemoreceptors Increased BP causes Baroreceptors to fire, and the signal travels to the solitary nucleus which then synapses In the nucleus ambiguous, activating parasympathetic cells in the dorsal vagal nucleus and decreasing HR and blood pressure through the vagus n.

Where are the sympathetic preganglionic cell bodies located?

Lateral horn of the spinal cord, T1-L3

Radiation

Loss of heat in the form of infrared rays (high to low)

Evaporation

Loss of heat through liquid changing to gas

Korsakoff Syndrome

Most commonly found in alcoholics, it is due to a prolonged thiamine deficiencyb that results in lesioning of the mammillary bodies, dorsomedial nucleus of the thalamis, fornix, and the hippocampal formation (Circuit of Papez) Patients will exhibit "confabulation" in which they string together fragments of memories from different memories to create an artificial memory of an event that never occurred Wenicke-Korsakoff syndrome: is the above pug ataxia (due to cerebellar damage)

NCS

Nerve conduction study; An elctrodiagnostic technique that involves the stimulation of a peripheral nerve with a stimulating electrode and then recording the passage of the potential to a muscle Measures the velocity of the current being carried by the nerve

What does the Posterior cerebral artery supply?

Occipital lobe and the Inferior part of temporal lobe, thalamus, corpus callosum, medial and lateral geniculate

Circuit of Papez

Pathway within limbic system that plays a key role in memory, consisting of: 1. Fornix 2. Mammillary body 3. Mammillothalamic tract 4. Anterior thalamus 5.T halamocortical fibers 6. Cingulate Cortex

Superior Division of the Middle Cerebral Artery territory supplied and signs and symptoms of a lesion

Pathway: comes out of the lateral sulcus, then ascends, supplying the frontal lobe, primary motor cortex, and primary somatosensory cortex → Supplies face, hand, and upper extremity Lesions result in contralateral sensory loss of the face and upper extremity, contralateral weakness (lower facial paralysis, tongue deviation), contralateral upper extremity weakness, expressive aphasia (if on the left side), incontinence, magnetic gait, apraxia

Inferior Division of the Middle Cerebral Artery territory supplied and signs and symptoms of a lesion

Pathway: comes out of the lateral sulcus, then descends, supplying Wernicke's area, parietal lobe, white matter (Meyer's Loop) Lesions result in Receptive aphasia (Wernicke's Area), contralateral neglect (Parietal lobe), "Pie in Sky"

Lenticulostriates Division of the Middle Cerebral Artery territory supplied and signs and symptoms of a lesion

Pathway: supplies the basal nuclei and the internal capsule (anterior limb, genu, and posterior limb) Lesions result in Complete contralateral sensory loss and contralateral upper motor neuron signs (contralateral face, tongue deviation, Babinski sign, hyperreflexia, spasticity)

Will a sympathetic or parasympathetic response be more widespread. Why?

Sympathetics will have a more widespread effect because their preganglionic fibers will innervate much larger numbers of ganglionic cells than do the parasympathetics This is why sympathetics will have a general effect (fight or flight), while parasympathetics have a more specific effect (regulate the function of a particular organ)

Horner Syndrome

Syndrome in which there is destruction of either the superior cervical ganglion, the fibers that run into the superior cervical ganglion, or the fibers that come out of the superior cervical ganglion resulting in a parietal and visceral sympathetic lesion of the head. ◦ Flushing of the face → loss of sympathetically mediated vascular tone ◦ Ptosis → paralysis of the superior tarsal muscle of Müller ◦ Anhydrosis → diminished sweating; loss of sympathetic innervation of the sweat glands ◦ Myosis → unopposed parasympathetic innervation of the constrictor pupillae muscle

Where are the preganglionic cell bodies of sympathetic nerves for thoracic organs located?

T1 - T6 cord levels (T1 - T5 for the heart, T2 - T6 for the lungs)

Where are the preganglionic cell bodies of sympathetic nerves for abdominal organs located?

T5 - L2 cord levels

Nerve Conduction Velocity

Test that measures the speed at which impulses travel through a nerve NCV = (distance between two stimulation points)/ (difference in latency times for the two stimulation points)

Heat Loss Center

The Anterior/ Preoptic Area of the hypothalamus that contains heat and cold sensitive neurons that respond to core temperature receptors. It will respond when the core temperature is hot in an effort to get rid of heat Lesions here will result in no sweating or vasodilation in response to an increase in temperature

Conduction

The direct transfer of heat from one substance to another substance that it is touching.

What is the blood supply of the internal capsule?

The majority of the internal capsule is supplied by the Lenticulostriate aa. (small arterial branches off of the middle cerebral artery) The more inferior aspect of the internal capsule will be supplied by the anterior choroidal artery (branch of the internal carotid) which if damaged results in weakness and hemianopsia

Heat Production Center

The posterior nucleus of the hypothalamus which integrates signals from the preotic area and peripheral temperature receptors It will respond to cold temperatures to produce heat Lesions here will result in decreased heat production mechanisms

Convection

The transfer of heat by the movement of warm air creating a gradient

Anterograd Amnesia

Usually caused by an injury of the hippocampus- it is short term memory loss in which a patient is unabel to remember anything that occurred more than a few minutes rior Memories of the distant past and intelligence remain intact

Left CN III ◦ Center Panel: Left Ptosis, Left Mydriasis ◦ Difficulty looking up, down, and adducting

Where is the lesion?

What is the mechanism of referred pain?

Within the spinal gray matter, GVA fibers nd GSA fibers can synapse on the same interneuron. The interneuron can then fire and transmit the pain sensation to the brain from either the GVA or GSA source, and the brain is unable to tell where the pain is coming from. Therefore, certain skin areas can be associated with pain during dysfunction of particular organs

What do the sacral parasympathetic fibers control?

• Defecation • Urination • Erection

What do the cranial parasympathetic fibers control?

• Pupillary contraction: running in cranial nerve III • Innervation of the small salivary glands: running in the cranial nerve VII • Innervation of the parotid (salivary) gland: running in the cranial nerve IX • Parasympathetic balance of thoracic and abdominal organs: running in cranial nerve X - vagus nerve

Detrusor-Sphincter Dyssynergy

Involuntary detrusor muscle contractions without relaxation of the external urethral sphincter → this leads to residual volume in the bladder that cannot be empties

Explain the Micturition pathway

"Infant" Bladder → Simple reflex with no higher order control 1. Bladder fills to a certain pressure, activating stretch receptors which sends the information to the spinal cord 2. When a certain pressure is reached, the bladder will automatically empty (relaxation of internal and external sphincter, contraction of the detrusor muscle) Adult Bladder A. Filling Phase → Low pressure in the bladder, allowing for the accumulation of urine 1. Sympathetics inhibit the detrusor m. (relaxing it) and activate the internal sphincter (keeping it close) 2. The Pudendal n. will act to keep the external sphincter closed B. Voluntary Emptying 3. Once urine has accumulated in the bladder, and is under higher pressure (activating the stretch receptors), this sensory information is sent to the reticular formation and from there, to the frontal cortex 4. The frontal cortex will make an executive decision on whether the reflex should be over-rid (don't urinate) or if emptying the bladder is okay (urinate)

A Flaccid Bladder occurs due to lesions in the (!), while a spastic bladder occurs due to lesions in the (II)

(I) Sacral spinal cord or Cauda equina ("lower motor neuron" type reaction) (II) Above the sacral segments ("upper motor neuron" type reaction)

Pathogenesis of Fever

1. Bacterial Infection creates exogenous pyrogens 2. The pyrogens will attract macrophages and monocytes 3. Macrophages and monocytes will activate endogenous pyrogens (cytokines: IL-1, IL-6, TNF-α) 4. Cytokines will increase PGE2 productions causing the alteration to temperature set point hypothalamic neuron firing 5. Altered hypothalamic neuron firing will raise the temperature set point

What composes the limbic system?

1. Limbic Lobe: contains the amygdala 2. Intralimbic gyrus: composed of gray matter 3. Inner Arc: composed of the fornix, it will terminated in the mammillary body

What is the course of the sacral parasympathetic fibers?

1. Preganglionic cell bodies are located in the lateral horn of the spinal cord 2. Preganglionic fibers run through the ventral root, into the spinal nerve, and then form the pelvic splanchnic nerves 3. The pelvic splanchnic nerves leave the spinal nerve and synapse on the pelvic parasympathetic ganglia (next to the organ) or the intramural ganglion in the wall of the organ 4. Post ganglionic fibers can either form parasympathetic plexi or run through the wall of the organs

What is the course of the GVE fibers of the parietal portion of the sympathetic nervous system?

1. Preganglionic cells bodies will be located in the lateral horn (T1-L3) 2. Preganglionic fibers will leave the lateral horn, and enter the ventral root into the spinal nerve, where they will then travel through the white communicating branch to enter the sympathetic ganglia where they will synapse with sympathetic postganglionic cell bodies 3. The postganglionic fibers will then leave the sympathetic ganglia through the gray communicating branch and re-enter the spinal nerve

What is the course of the GVE fibers of the Visceral portion of the sympathetic nervous system?

1. Preganglionic sympathetic cells bodies will be located in the lateral horn 2. Preganglionic fibers will enter the ventral root and into the spinal nerve, where they will then travel into the white communicating branch and enter the sympathetic ganglia 3. Inside the sympathetic ganglia, some preganglionic fibers will synapse (these will be the ones to innervate thoracic viscera) while others will run through the ganglia, synapsing instead in a prevertebral ganglion (these will be the ones to innervate abdominal and pelvic viscera) or rarely, intramural ganglion (inside the abdominal or pelvic organs) 4. Postganglionic fibers will leave via the splanchnic nerves and travel to the walls of the organs

Flow of blood to the CNS

A. (1) Vertebral artery will branch off the subclavian artery, travel through the transverse foramen to the foramen magnum and give rise to the "posterior circulation" which supplies the Spinal cord, brainstem, diencephalon (thalamus, subthalamus), and posterior regions of the telencephalon (occipital lobe, lower temporal lobe) → The vertebral artery will give rise to the: (A) Posterior Inferior Cerebellar artery (PICA), (B) Anterior Spinal Artery which sits on the front of the medulla and runs the entire length of the spinal cord, being supported by (6-8) Feeder vessels, and contains "Penetrator artery" branches that enter the spinal cord as well as (C) Posterior Spinal arteries which will be on the right and left hand sides of the spinal cord running its entire length and which are supported by (10-12) Feeder vessels and both of which provide blood supply to the spinal cord The Arterior Vasocorona (AVC) will be the connection between the anterior and posterior spinal arteries → The Vertebral arteries from the right and left sides will join on the underside of the brain, to form the basilar artery, which will branch to supply the medulla, pons, midbrain, and thalamus ◦ The Anterior Inferior Cerebella artery (AICA) will branch off of the Basilar artery, as well as the Pontine aa. and the superior cerebellar artery ◦ The basilar artery will then split in the midbrain, into right and left posterior cerebral arteries which will be connected to the anterior system via the Posterior communicating artery B. (2) Internal Carotid Arteries will form the "anterior circulation", supplying most of the telencephalon (frontal lobe, parietal lobe, insula) and basal nuclei (internal capsule, caudate nucleus) → The Internal Carotid artery will arise from the cervical region of the neck, travel through the temporal bone and into the carotid canal. It then snakes through the cavernous sinus, forming the carotid siphon (snaked/ squiggle portion). When the Internal carotid exits the cavernous sinus, it gives rise to: (A) Ophthalmic Artery which gives rise to the central artery of the retina and supplies the orbit, (B) Posterior communication artery which connects the anterior and posterior circulation, and the (C) Anterior Choroidal artery → The Internal Carotid will split into the (A) Anterior Cerebral Artery which connects the right and left internal carotid arteries in the circle of willis, and the (B) Middle Cerebral Artery which will give rise to the Lenticulostriate aa. which are the major blood supply to the internal capsule Anterior and posterior circulations are connected via the posterior communicating artery in the Circle of Willis (region of blood vessels around the hypothalamus and optic chiasm), but it is small and not entirely functional → The circle of willis has an intimate connection with the cranial nerves → The Anterior communicating artery which connects the (2) Anterior Cerebral arteries from either internal carotid is the most common place for an aneurysm, and is located next to the Optic Nerve (CN II) → The Posterior communicating artery which connects the posterior cerebral artery branches of the basilar artery to the internal carotid a. is also a common site for aneurysms and is linked to the Oculomotor n. (CN III). For this reason, an isolated CN III palsy is a posterior communicating artery aneurysm until proven otherwise

Artery of Percheron

An anatomic varient of the Posterior cerebral artery in which there are not two branches going to the thalami, but rather one. Blockage can results in bilateral ventromedial thalamic infarction

Alzheimer's Disease

An irreversible, progressive brain disorder, characterized by the deterioration of memory, language, and eventually, physical functioning Will be caused by intracellular neurofibrillary tangles and extracellular amyloid deposits which most often first occur in the hippocampus resulting in memory loss.

Function of the hippocampus

Consolidation of short term memories Will emit a signal that allows it to "rehearse" the memory repeatedly until it is stored in the cerebral cortex for long term memory

Motor Neurogenic Bladder

Damage to the peripheral ANS, resulting in a flaccid bladder (increasing capacity) with areflexia (inability to empty bladder) although there is normal sensation Leads to overflow incontinence and painful urinary retention This is an infection risk

Sensory Neurogenic Bladder

Damage to the peripheral ANS, resulting in an inability to sense fullness of the bladder/ reduced urge Areflexia leading to overflow incontinence and urinary retention This is an infection risk

Lesion of the lateral hypothalamic zone results in what?

Decreased food and drink intake

What is the result of a lesion in the hypothalamal-hypophyseal tract between the paraventricular and supraoptic nuclei?

Diabetes Insupidus: there will be a lack of vasopressin, resulting in excessive water loss through the kidney

Benedikt Syndrome (Claude + Weber Syndrome) ◦ Occlusion of the Paramedian Branches of the Posterior Cerebral Artery (PCA) → Damages the Superior Cerebellar Peduncle, CN III, the Corticonuclear tract, the Corticospinal Tract, and the Substantia Nigra ◦ Superior Cerebellar Peduncle damage results in bilateral ataxia ◦ CN III damage results in Ipsilateral CN III palsy (this directly indicates midbrain lesion) ◦ Corticonuclear tract damage results in contralateral lower facial paralysis, sagging palate, and tongue weakness with deviation to the contralateral side ◦ Corticospinal Tract damage results in upper motor neuron signs including hyperreflexia and babinski sign ◦ Substantia Nigra damage results in bradykinesia and tremors