NeuroHistology Structure & Condition

what are the functions of neurons

• drive motor function

• release hormones

• regulate immune and metabolic functions

what is the junctions between neurons called

synapse

a large axon has a large cell body and a small axon has a small cell body why is that

that is because the axon must be supported by the cell body

what is the range of resting membrane potentials for a neuron

-90mv to -50mv

how is resting membrane potential established in neurons

through the sodium potassium pump and potassium leak channels

what causes neurons to utilize so much energy in the body

the use of the sodium potassium pump to reestablish the membrane potential after the action potential

what can trigger an action potential to occur

• neurotransmitter binding

• nociceptor response

The sudden influx of what ion allows for the action potential to begin

Sodium

What stabilizes the closed outer gate in the sodium gated channel

calcium

what direction can the action potential travel down a neuron

it can travel both directions

What are the 3 steps of repolarization

1. close the sodium channel

2. open the potassium channel

3. reestablish the membrane potential

How would a dog having hypoglycemia or hypoxemia affect a neuron

Neurons would not be able to run the sodium potassium pump making it hard to establish a membrane potential

how would a dog having increased extracellular potassium affect neurons

it would diminish the gradient for leak channels making it hard to establish membrane potential.

how would a dog having decreased extracellular calcium affect the neurons

it would reduce the stabilization of the outer sodium gate making it easier for an action potential to happen

Brevotoxin, tetrodotoxin and saxitoxin cause paralytic sea food poisoning. What is the target of these toxins?

Voltage gate sodium channels

Lidocaine is used to block transmission of painful stimuli along the course of sensory neurons. What is the target of this nerve block agent?

Voltage gate sodium channels

where can neurotransmitters be synthesized

• axon terminus

• neuron cell body

the rise of this intracellular ion causes fusion of vesicles containing neurotransmitters with the plasma membrane of the axon terminus

calcium

what are the 2 types of post synaptic receptors

• ion channels

• enzyme receptors

between ion and enzyme receptors which one is known as slow and which one is known as fast

• ion is fast

• enzyme is slow

what are the 2 general results of neurotransmitters binding

• excitation

• inhibition

what channels are opened in excitatory vs inhibitory responses

• sodium in excitatory

• potassium in inhibitory

what type of neurotransmitters bind to ion channels

small molecule rapidly acting neurotransmitters

what type of neurotransmitters bind to enzyme receptors

neuropeptides

a neuron is called a Cholinergic neurons because it produces acetylcholine why is that?

that is because a neuron can only produce one type of small molecule neurotransmitter

where are small molecule neurotransmitters synthesized

pre synaptic terminal

where are neuropeptides synthesized

cell body

what is synaptic complexity

it is where the input of various neurons may influence the activity of one postsynaptic neuron

the death of a neuron from excessive release of an excitatory neurotransmitter is called what

Excitotoxity

what is nissil substance

rough endoplasmic reticulum found in the cell body of a neuron

what are the two types of axoplasmic transport

• fast antegrade

• slow antegrade

the blocking of either fast antegrade or slow antegrade transport of axonal substances might cause what?

Neuroaxonal dystrophy

what structure is the result of blocking axoplasmic transport

spheroid

what is Wallerian degeneration

it is when an axon is essentially amputated

in cases of extreme hypoxemia and glycemia a cell will lose its nissel substance resulting in what

central chromatolysis

what is saltatory conduction

it is the jumping of depolarization from node to node

what are the benefits of saltatory conduction

• increased action potential velocity

• conserves energy

what cell produces myelin in the CNS

oligodendrocytes

what cell produces myelin in the PNS

Schwann cells

if an autoimmune disease was to target myelin what would be its difficulty

it would have to select between Schwan myelin and oligodendrocyte myelin

what special characteristic of schwann cells allows for neurons to be regrown in the peripheral nervous system

schwann cells produce collagen tissue on the side opposite of the myelin

which myelin producing cell is more efficient at covering neurons

oligodendrocytes

loss of myelination can take two forms what are they

• primary demyelination

• secondary demyelination

what is the cause of secondary demyelination

axon degeneration

what are causes of primary demyelination

• viral infection

• immune mediated

• toxins

• metabolic damage

if you were to find primary demyelination alongside inflammation what two causes would you suspect

• viral infection

• immune mediated

if you were to find primary demyelination alongside no inflammation what two causes would you suspect

• toxins

• metabolic damage

what are astrocytes

cells used as a replacement for the extracellular environment

what are the functions of astrocytes

• metabolic support

• regulate tissue water content

• direct formation of the blood brain barrier

• support neuronal signal transduction

in the case of injury in the CNS what cell strengthens and extends their cytoplasmic processes by increasing synthesis of cytoskeletal intermediate filaments

astrocytes

in developing neonates external granular cell layer neurons want to migrate to the internal cell layer, what cell can assist them with that

astrocytes

what are microglia

macrophages for the CNS

what two signals are microglia seeking out

• damage associated molecular patterns

• pathogen associated molecular patterns

• interferons

what cells do microglia resemble when inactive

oligodendrocytes

what is the most abundant feature in gray matter

neuronal cell bodies

what is the most abundant feature in white matter

oligodendrocytes

in the cerebellar cortex from outside to in list of the sections of tissue

• Molecular layer

• purkinje cell layer

• granular cell layer

• white matter

in the spinal cord from outside to in name the tissue layers

• white mater

• dorsal gray matter

• lateral gray matter

• ventral gray matter

what tissue contains ascending axons

dorsal lateral gray matter

what tissue contains descending axons

ventral lateral gray matter

what cell bodies does ventral gray matter contain in the spinal cord

large motor neuron cell bodies

what cell bodies does lateral gray matter contain in the spinal cord

autonomic nervous system cell bodies

what cell bodies does dorsal gray matter contain in the spinal cord

sensory fibers

in the periphery what does ganglia mean

it is an aggregate of cell bodies

sympathetic neurons synapse with what

discrete ganglion cell neurons

parasympathetic nerons form a synapse with what

neruons embedded in the target organs

what is the synapse of a neuron located in the target organ called

plexus

from macro to micro list the connective tissue surrounding neurons in the peripheral nerves

• epinerium

• perinerium

• endonerium

You are performing a gross post mortem examination, and you see pathological changes localized to grey matter. How do you interpret this change?

The disease is targeting neurons.

what structures form the blood brain barrier

• endothelium

• basement membrane

• astrocyte

what areas of the brain are considered circumventricular organs

• hypothalamus

• pituitary glands

• pineal glands

what is special about circumventricular organs

they are able to respond to systemic metabolic changes

why has axillary CSF circulatory system evolved

it addresses the needs of the cells within the center of the brain mass

name the ventricular pathway for cerebrospinal fluid

1. lateral ventricle

2. interventricular foramen

3. third ventricle

4. mesencephalic aquaduct

5. fourth ventricle

after exiting the ventricles what happens to the cerebro spinal fluid

• exits onto the surface of the brain

• emerge onto the surface of the spinal cord

what generates the CSF

Choroid plexus

what are the parts of the choroid plexus

• blood vessels

• tela choroidea

• plexus epithelium

in what ventricles are choroid plexi present

• lateral ventricle

• third ventricle

• fourth ventricle

what drives circulation of the CSF

the cilia of the ependymal cell layer

True or false? The barrier between blood and CSF exists at the levels of the plexus epithelium and not the vascular endothelium.

True

what is the space called in which CSF empties into

Subarachnoid space

label the meninges

1. Dura matter

2. arachnoid membrane

3. pia matter

4. subarachnoid space

what structure allow for resorption of CSF into the dorsal sagittal venous sinus

Arachnoid granulation

True or false? A feedback mechanisms exists to balance CSF production with the rate of resorption.

false

what does decreased resorption of CSF cause

hydrocephalus

Analysis of cerebrospinal fluid (CSF) reveals an increase in total protein and a large number of lymphocytes. How do you interpret this change?

There is inflammation, but the location cannot be determined based upon CSF analysis alone.