what are the processes that proceed implantation in the uterine wall and how long does it take for these processes to complete?

fertililzation, cleavage, morula, blastocyst

takes approximately 8 days

what is the inner cell mass

mass of cells inside the blastocyst that will differntiate into embryonic cell layers

what are the two layers that are formed in a bilaminar disk

primary endoderm (faces the primitive yolk sac)

embryonic ectoderm (facing the amniotic cavity)

what are the two groups of cells contained in the blastocyst and what are their fates

trophoblast = forms the placenta

inner cell mass = forms the embryo

what are the names of the three primary germ layers

 endoderm

mesoderm

ectoderm

what is the original surface defect of the uterine wall closed by

fibrin coagulum

at what time frame do we see a bilaminar disk consisting of primary ectoderm and endoderm

approximately 16 days

what is the primitive streak

increase in surface cellular activity from the narrower posterior portion ofthe disk to the wider anterior portion of the disk

in what direction do we see surface cellular activity move in the primitive streak

from the narrower posterior to the wider anterior portion of the disk

a small cellular bump at the anterior of the primitive streak

primitive (or hensons) node

what lies in the center of the primitive node

the primitive pit = a depression in the center of the primitive node

what is the primitive pit

opening of the neuroenteric canal

what are the two membranous regions forming in the bilaminar disk

prochordal plate = anterior of embryo

cloacal membrane = posterior of embryo

what designates the anterior of the membrane

prochordal plate

what designates the posterior of the membrane

cloacal membrane

what is another name for the surface ectoderm

neural ectoderm

what triggers the formation of the notochord

mesodermal cells begin to proliferate out radially both anteriorly and posteriorly between neural ectoderm and endoderm

how is the notochord formed

the mesodermal activity triggers anterior migration of cells from the primitive node = the primitive notochord

what does the notochord induce

formation of the notochord induces rapid proliferation of the surface ectoderm to invaginate and begin formin ebryonic nervous system

what is neurulation

 rapid proliferation of the neuroectoderm leads to invagination of the nervous system forming a open tubular structure from front to back

what is the neural tube

a open tube form via invagination of the neuroectoderm during neurulation

what are the two openings of the neural tube

anterior = anterior neuropore

posterior = posterior neuropore

what are neural crests

the lateral borders of the evolving neural tube that separate from it taking a position above and lateral to it

at what time do we see neurulation

approximately 28 days

at what time do we see formation of the embryonic notochord

approximately 18 days

what is the neural plate

thickening of the ectoderm near the midline

what is the neural groove

the crease developing along the axis of the neural plate where the neural plate will invaginate

what are the neural folds

lateral edges of the neural plate that will gradually move together

what are the three layers we find in the neural tube

ependymal layer = lines the enclosed cavity

mantle layer

marginal layer

at neurulation what is released into the CSF

alph fetoprotein

what do high levels of alpha fetoprotein imply

spina bifida (posterior neuropore)

hydro-ana-cephalis (anterior neuropore)

what do low levels of alpha feto protein imply

downs syndrome

what condition might be implies if the anterior neuropore doesn't close properly

hydro-ana-cephalis

what condition might be implied if the posterior neuropore does not close properly

spina bifida

what is the primary vesicle

happens when both ends of the neural tube close forming a growing tubular nervous system

what are the four parts of the primary vesicle

 prosencephalon (forebrain)

mesencephalon (midbrain)

rhombencephalon (hindbrain)

spinal cord

how is the secondary vesicle formed

transverse segmentation

the forebrain

prosencephalon

the midbrain

mesencephalon

the hindbrain

rhomboencephalon

what are the six parts of the secondary vesicle

telencephalon

diencephalon

mesencephalon

metencephalon

myelencephalon

spinal cord

what occurs because the brain grows faster than the school

 flexion

what is evagination

 the process by which the cortical hemispheres, cerebellum and special sensory capsule develop via outpouches growing off of the secondary vesicle

what are the derivatives of the telencephalon

cerebral cortex

basal nuclei

olfactory bulbs and tracts

lateral ventricles

what are the derivatives of the diencephalon

optic chiasm, tracts, nerves

thalamus

hypothalamus

third ventricle

what are the derivatives of the mesencephalon

mid-brain nuclei

cerbral aqueduct

what are the derivatives of the metencephalon

pons

cerebellum

fourth ventricle

what are the derivatives of teh myelencephalon

medulla oblongata

fourth ventricle

what are the two types of cells in the nervous system

neurons and neuroglia

what are the two precursor cells of neurons

neurotubular epithelium and neural crest

what does neurotubular epithelium give rise to

neurons of the CNS

neuroglia

ependymal cells

what do neural crests give rise to

neurons of the PNS

what are the cellular derivatives of neurotubular epithelium

neuroblasts (CNS neurons)

Glioblasts (marcroglia)

Ependymoblasts (ependymal cells)

what are the cellular derivatives of neural crests cells

 sensory ganglia (PNS, DRG's, Cranial Nerves) 

motor ganglia (PNS autonomic ganglia)

schwann cells

chromaffin cells of adrenal medulla

melanocytes

head mesenchyme

the largest and most numerous glial cell

astrocyte

what are the roles of astrocytes

 Insure stability of CNS environment by

regulate extracellular K

control extracellular glutamate (excitatory) and GABA (inhibatory)

play role in modulating energy needs of neurons

what are the two types of astrocytes

fibrous

protoplasmic

what are fibrous astrocytes

interpossed between neurons and adjacent blood vessels

white matter

perivascular feet

what are protoplasmic astrocytes

mostly in gray matter

These cells form most primary brain tumors

astrocytes form gliomas

These are seen in sever brain damage and made from which type of glial cell

anisomorphic gliosis (glial scars)

formed from astrocytes

these are laid down by astrocytes in response to neuron damage

fibrilar gliosis (filamentous components)

these cells are involoved in BBB and guide axon elongation

astrocytes

What are oligodendrocytes

 small neuroglial cells with few processes

more in white matter than gray matter

what are the three types of oligodendrocytes

perineuronal

intrafascicular

perivascular

what are perineuronal oligodendrocytes

satellite cells in close proximity to cell bodies and dendrites

what are infrfascicular oligodendrocytes

 white matter in rows btwn myelinated fibers

form and maintain myelin sheaths in CNS (can myelinate 7 to 70 axons)

attemp remylination in damaged processes

pH regulation

what is the origin of microglia

mesodermal

what are microglia

white and gray matter

activated by inflammatory processes

shaping neuronal circuits during development

what are ependymal cells

line ventricles and central canal of spinal cord

microvilli

help form choroid plexus

what are schwann cells

form the myelin in PNS can only myelinate one nerve at a time

what is the relationship between fiber diameter and conduction velocity

directly proportional the larger the diameter the faster the conduction velocity

found mostly in white matter

fibrous astrocytes

infrafascicular oligodendrocytes

found mostly in gray matter

 perineuronal oligodendrocytes

protoplasmic astrocytes

found in both white and gray matter

microglia

what is endoneurium

connective tissue surrounding individual nerve fibers

what is perineurium

connective tissue surrounding nerve fasicles

what is epineurium

connective tissue sheath surrounding a group of fasicles in nervous tissue

what is the alar plate

the part of the spinal cord where sensory inputs are developed

what is the basalar plate

part of the nervous system where motor components are developed

what causes the resting membrane potential

because of protiens being almost exclusively present inside the cell and they have a net negative charge which skew the distribution of ions

what is the major ion distribution inside and outside the cell

Na= 10mM (inside) 140mM (outside)

K= 140 mM (Inside) 4mM (outside)

Cl= 40mM (Inside) 103mM (Outside)

what is conductance

the ability to move across the membrane

what is the relative conductance of Na, K

Na = .04

K = 1.00

What is the most permiable ion across the membrane

K

What two forces can cause an ion to want to move

electrical and concentration

Where do sodiums concentration and electrical forces want it to move

both forces point inside of the cell so sodium will move, because it can (conductance) and wants (force) to, inside the cell

what does the nerst equation tell us about K

that at -94mV the concentration forces are equal and opposite and at that membrane potential there will be no net etndency for K to move

In which direction does K concentration force pull it

outside the cell

So what happens to K at -70mV

the electrical force is to weak to pull it into the cell at -70 so K move outside of the cell due to concentration force

what is the driving force

the net force on an ion to diffuse

what is the nerst potential, membrane potential, and driving force for Na and K

Na= 70mV (NP) -70mV (MP) 140mV inward (DF)

K= -94mV (NP) -70mV (MP) 24mV outward (DF)

What is Flux and what is it a function of

Flux = total diffusion

it is a function of conductance and driving force

Flux = (conductance)(driving force)

how do we alter membrane potential

by altering permiabilities

what is threshold

that point at which the membrane must be excited to fire an action potential

what is depolarization

here the charge seperation across the membrane is being lost or the polarity of the membrane is being lost

what is the overshoot

where the inside of the neuron actually becomes positively charged after depolarization and before repolarization

how long are depolarization and repolarization phases

1mSec each

what is repolarization

where the membrane is returning to the resting membrane potential because positive charge is moving out of the cell

what is afterhyperpolarization

 where the membrane becomes even more negative then resting potential after repolarization phase

what is the relative refactory period

the time of afterhyperpolarization where it is less likely that that the membrane will reach threshold again

what two factors make it so Na and K do not cancel each other out when the voltage gated channels open

Na driving force is much greater so it flows more rapidly

K channels open more slowly

what is depolarization a result of

Na having the greatest permiablity

what is repolarization a result of

 Na permiability is at rest and K permiability is at a peak

what is afterhyperpolarization a result of

Na permiability is at rest will K permiability is greater than at rest

At rest which gates are open and which are closed

Ungated channels open

Na inactivation open

Na activation closed

K gate closed

At threshold which gates are open and closed

Na activation gates open

K activation gates open

Na gates open faster than K

At peak of action potential which gates are open and which are closed

Na inactivation gets closed

K gates become fully open

Repolarization occuring

During repolarization which gates are open and closed

Na activation gate is closed

K gate is open

 once below threshold which gates are open and which are closed

Na activation closed

Na inactivation open

K gate open for hyperpolarization

 Once hyperpolarization is reached which gates are open and which are closed

K gate slowly close

Na activation closed

Na inactivation open

returns everything back to resting potential and permiabilities

what is the maximal frequency for firing action potentials

400 - 500 impulses per second

because absolute refractory there must be 2mSec inbetween action potentials

what are the two types of synapes

chemical and electric

what is the intercellurlar space of the chemical and electric synapses

 chemical = 20-30nm

Electric = 2nm

how is the signal mediated in chemical and electric synapses

 chemical = neurotransmitter

electrical = ionic current mediator

what is the synaptic delay in chemical and electrical synapses

chemical = 1-5ms

electrical = almost not synaptic delay

what is the direction of chemical and electrical synapses

chemical = unidirectional

electrical = bidirectional

where do we see electrical synapses

cardiac and smooth muscle

what are the components of the neuromuscular junction

presynaptic boutoon (nerve terminus)

synaptic vesicles

synaptic cleft

motor end plate

What is the role of Ca at the neuromuscular junction

Ca enters the bouton and binds to the vesicle once it is bound to the vesicle it moves the vesicle to the distal end of the bouton where it binds with a snare protein

what allows Ca to bind to the vesicle in the bouton

fusion protein (snap proteins)

What allows the Ca bound vesicle to bind to the membrane

snare protein

what are the different types of synaptic transmission

  Inhibitory post synaptic potential

excitatory post synaptic potential

pre-synaptic inhibition

post-synaptic inhibition

competitive inhibition

what happens with ion permiability with excitatory synapses

Na permiability is increased to depolarize the membrane

What happens to ion permiability at an inhibitory synapse

K and Cl flow out of cell to hyperpolarize the membrane

what is temporal summation

successive stimulation of the same neuron

what is spatial summation

sums stimulus from 2 different neurons

what is the role of acetylcholine

it is the chemical messanger

Neurotransmitter

what is the role of acetylcholinesterase

breaks down and recycles ACh once it has been released and bound to receptor

peptide neurotransmitters

Enkephalins

Endorphins

Substance P

Somatostatin

Vasopressin (ADH)

Oxytocin

Neurotensin

small molecule neurotransmitters

acetylcholine

amino acid neurotransmitters

Glutamate

aspartate

GABA

Glycine

catecholamine neurotransmitters

 dopamine

norepinephrine

epinephrine

Indolamine neurotransmitter

 serotonin

imidazolleamine neurotransmitter

histamine

these neurotransmitters reduce pain sensation

enkephalins

endorphins

this neurotransmitter enhances pain

substance P

main excitatory neurotransmitter in the CNS

glutamate

main inhibitory neurotransmitter in the CNS

GABA

excitatory neurotranmitter in the cerebellum

aspartate

inhibitory neurotransmitter in the spinal cord

glycine

What enzyme breaks down catecholamines

MAO

monoamineoxidase

these neurotransmitters are all derivites of tyrosine

catecholamines

What are the two classes of cholinergic receptors

nicotinic

muscarinic

where do we find nicotinic receptors

 autonomic ganglia

skeletal muscle motor end plates

where do we find muscarinic recptors

 Central Autonomic Ganglia

Smooth Muscle

Cardiac Muscle

What are the muscarinic blockers

 atropine (Belladonna)

Scopolamine

what are the two types of competitive inhibitors

 Non-Depolarizing

Depolarizing

what are the non-depolarizing competitive inhibitors

curare

gallium

what are the characteristics of non-depolarizing competitive inhibitors

Motor end plate inhibitors

slow onset/long duration 30-40min

reversed by colinesterase inhibitors (neostigmine, physostigmine)

what is a depolarizing competitive inhibitor

 succinylcholine

What are the characteristics of depolarizing competitive inhibitors

fast onset/short duration 3-5 min

reversed by cholinesterase or psuedocholinesterase

What is a ganglionic blocker competitive inhibitor

TEA

Tetraethylamonium

what is the function of a ganglionic blocker competitive inhibitor

blocks K channels

this inhibitor allows abdomen to relax

gallium

non-depolarizing competitive

this inhibitor allows the pharyngeal musculature to relax

succinylcholine

what reverses non-depolarizing competitive inhibitors

cholinesterase inhibitors

neostigmine, physostigmine

what reverses depolarizing competitive inhibitors

cholinesterase or psuedocholinesterase

what are the two categories of agents that interrupt synaptic transmission

non reversible cholinesterase inhibitors

reversible cholinesterase inhibitors

What are the non-reversible cholinesterase inhibitors

 organophosphates

• fertilizers
• insectacides
• nerve gases

 what can be done to reverse organophosphates

may be reversed by atropine over a long period of time or by pralidoximine (PAM) a cholinesterase regenerator

What are examples of a reversible cholinesterase inhibitors

neostigmine, physostigmine

what is used in the treatment of myasthenia gravis

neostigmine and physostigmine

reversible cholinesterase inhibitors

what are the neurotoxins

 tetrodotoxin

alpha bungarotoxin, cobora alpha neurotoxin

clostridia botulinus and tetani

stryichnine

this neurotoxin is a Na channel blocker and comes from blowfish

tetrodotoxin

this neurotoxin is a ACh blocker at nicotinic sites

 Alpha bungarotoxin

cobora alpha neurotoxin

this neurotoxin is a Ca channel blocker

clostridia botulinus and tetani

This neurotoxin is a glycine blocker

styrichnine

how do local anesthetics work

block Na channels and reduce nerve conduction

What is axoplasmic flow

the process by which the products formed in the cell body are transported great distances in cytoplasm of the axon both forward and backwards

what are the two compartments of anterograde flow

fast compartment 300-400 mm/day

slow compartment 1mm/day

what is being transported in the fast compartment of anterograde flow

membrane organelles

transmitter components

where does fast compartment anterograde flow take place

SER

Energy required

what is transported via slow compartment anterograde flow

 soluble enzymes

membrane proteins

cytoskeletal units

where does slow compartment anterograde flow take place

bulk flow transport via microtubules

What is the rate of retrograde flow

200 mm/day

what is transported via retrograde flow

membrane components

mitochondria

vesicles

lysosomes

Where does retrograde flow happen

via microtubules

SER

energy required

what is the negative effect of retrograde flow

transport of viruses toward cell body

what are the types of injury that can be sustained by a neuron

laceration

crushing

anoxia (loss of oxygen)

ischemia (lack of blood)

what is the general rule applied to damage to a neuron

the closer the injury to the cell body the less likely the neuron can repair itself

Even if a neuron can repair itself it does not imply it will be functional

what is the axon reaction

reaction undergone by the neuron if nerve trunk is injured

What is involved in the axon reaction

 release of ribosomes from RER and dispersle within cytoplasm

cell body swells

recovery begins in 20 days

recovery will take several months

what  happens to the distal segment in the axon reaction

swells

axon fragments

fragments are phagocytized by schwann cells

what are the components of regeneration

growth cone forms on proximal segment

sprouting

progression towards target tissue

may have neuroma formation