Medical Neuroscience



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Chapter 2-6



1. Vascular anatomy of spinal cord
Branches of vertebral arteries

Anterior spinal artery

Supply ventromedial spinal cord along entire length

Dorsal and ventral horns

Lateral corticospinal tracts

Lateral to spinal cord gray matter

Posterior spinal arteries

Supply margins of entire cord

Supplied from radicular branches of lateral spinal arteries

Neck = vertebral arteries

Below neck = intercostals arteries

Artery of Adamkiewicz = T9-L4


2. Occlusion of artery of Adamkiewicz
Thoracic region of cord = least number of spinal arteries

“Terminal drought” region

Most likely to be affected

Artery of Adamkiewicz

Infraction of anterior and posterior spinal artery perforators region

Lateral corticospinal tracts

Lateral spinothalamic tracts

Below lesion level

“Anterior spinal artery syndrome”

Chapter 2-7



1. Elevated central venous pressure and high CSF pressure
Superior sagittal sinus – confluens of sinuses – transverse sinuses – sigmoid sinuses – internal jugular veins

Inferior sagittal sinus – straight sinus – confluens of sinuses – transverse – sigmoid – internal jugular veins

Brain surface go to cortical veins

Deep brain go to straight sinus

Cavernous sinuses – superior and inferior petrosal sinuses – transverse and sigmoid sinuses

Periorbital and paranasal face

Drain into cavernous sinuses
Central venous pressure

Communicate through arachnoid granulations to CSF compartment

Obstruction of cerebral venous flow = increased CSF pressure
2. Cerebral sinus thrombosis and elevated intracranial pressure with pseudotumor cerebri
Pseudotumor cerebri = increased intracranial pressure in absence of a mass

Caused by obstruction of outflow of CSF

Sinus thrombosis obstruct CSF though arachnoid granulations

Increase in intracranial pressure

Intracranial pressure interfere with flow of cytoplasmic constituents along retinal ganglion axons

Swelling of optic nerve heads


3. Sinus thrombosis can cause cerebral infarction
Sinus thrombosis spread to cortical venous thrombosis

Collaterals cannot drain blood from sinuses

Perfusion stop = tissue infracted

Superior sagittal sinus = most common

Parasagittal region of brain = motor cortex of precentral gyrus
4. Cranial venous flow and central facial infections
Venous drainage from ocular and paranasal tissues

Into cavernous sinuses



Chapter 2-8



1. List major principles governing cerebral energy metabolism.
Brain = glucose

CNS glucose uptake = ATP-linked transport

Do not require insulin

Exclusively aerobic metabolism

No oxygen storage

Minimal glucose storage in glia



<50% energy for intermediate metabolism

>50% energy for maintenance of ion gradients

Synthesis, transport, packaging, release, reuptake

Require high blood flow = 20% resting cardiac output


2. Cerebral Blood Flow: cerebral vascular autoregulation & arterial CO2
Increase Local Blood Flow

Potassium = outflow of potassium from neural cytosol into extracellular space

Instantaneous

Tigger vasodilatation

CO2 concentration

Slower


Large fluctuation in arterial CO2

O2 concentration

Slowest
3. Ranges of cerebral blood flow rates
Normal cerebral blood flow = 50-60 mL/100g/min

Higher in women

Lowest normal cerebral blood flow = 23 mL/100g/min

Metabolic reserve of two-thirds

Lowest cerebral blood flow without damage = 18-23 mL/100g/min

Neural activity ceases

Cerebral blood flow infraction = Below 18 mL/100g/min
*High cerebral tolerance = makes cardiac surgery feasible & opportunity for treatment of stroke
4. Reduction of blood pressure in patients with acute stroke is catastrophic
Ischemic penumbra = volume of tissue in which blood flow is 15-23 mL/100g/min

All neurons in region = silent & serious jeopardy

Resistance vessels (arterioles) are maximally dilated

Cerebral blood flow = linear function of perfusion pressure

Reduction in systemic blood pressure = increase infarction size

Chapter 3-1



1. Morphology of neurons
Dendritic spines = small bulbous excrescences of dendritic neural membrane

Increase surface area for axonal contact

Abnormal spines = Down’s syndrome

Cell body = receiver & metabolic center

Axon = conductor & metabolic center

Axon hillock = generate action potential

Axon terminal = secretory & transmitter

Terminate in synaptic boutons = neurotransmitter & neurosecretion


* pyramidal neuron = cerebral cortex
2. Neuronal metabolic demand
Require glucose and O2

Numerous organelles = high biosynthetic activity

Maintenance of processes and neurotransmitter synthesis

Prominent ribosomes and rER (Nissl bodies)


3. Elements of cytoskeleton
Microtubules

13 thick linear protofilaments = form 25-nm diameter cylinder

Neurofilaments (intermediate filament)

24 thin protein filaments of cytokeratin = form 10-nm diameter solid fibril

Microfilaments

7-nm diameter fibers composed of two actin filaments


Cytoskeleton function:

  • maintenance of neural morphology

  • positioning of membrane proteins (receptors and ion channels)

  • distribution of membrane-bound organelles

  • provide scaffold for axoplasmic transport

  • neurotransmitter release


4. Axoplasmic transport and disorders
Axoplasmic transport = process of moving proteins and organelles along axons

Require local supply of ATP

Anterograde

Fast


Membrane-bound intracellular organelles (mitochondria, lysosomes)

Kinesin motor protein

Slow

Cytoskeletal proteins



Regrowth of axons occur at this slow rate (1 mm per day)

Retrograde

Trophic support substances (growth factors)

Axon terminal to cell body

Cell maintenance (proteins & lipids)

Path for pathology (rabies, herpes, polio, tetanus)


Axotomy = axon being severed from cell body

Loss of retrograde axoplasmic transport of trophic factors

Wallerian degeneration

Vincristine neurotoxicity in Hodgkin’s disease

Prevent microtubule polymerization = paresthesias of senses and distal weakness
5. Chemical synapse
Presynaptic & postsynaptic regions of thickening synaptic membrane

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