Lunatics and Princesses

Pregnancy does cause memory loss, study says

( Linkophobes line up here )

This reminds me of an article I read in Scientific American sometime last year about how pregnancy changes your brain and its chemistry permanently. Just one more reason not to have a kid- I like my brain quite the way it is, thank you very much.

Thoughts?

NEUROPHYSIOLOGY...
...Electrical Properties of Nerve cells (neurons)

electrophysiology of neurons lies in their... Membrane Physiology
the model organism is : Squid Giant Axon [Loligo pealei]
there is a a great diversity* of Nervous Systems

FUNCTIONS of NERVOUS SYSTEM -
[a la SIGNAL TRANSDUCTION : reception - transduction - response ]
1. gathers sensory input (sense organs via Peripheral NS) --> info in
2. integrates information (CNS - brain & spinal cord)
3. responds with motor output (effector organs via PNS - muscles)

STRUCTURAL PARTS of Nervous System -
central nervous system - brain and spinal cord...
(neural stem cell = origin of brain)
peripheral nervous system - outside the CNS- carries signals in/out of CNS
PNS = sensory (affernet) and motor (efferent) neurons:
- somatic nervous system - carries signal to skeletal muscle - under conscious control
- autonomic nervous system - signals regulate internal systems - involuntary control
2 antagonistic Parasympathetic (cranial & cholenergic)* - calming: HR-, energy storage

systems: Sympathetic (spinal & noradrenaline)* - energy & arousal: HR+, glycogen--> glu


FUNCTIONAL TERMINOLOGY of Neurons -
Nerve - bundle of neurons wrapped in connective tissue
Ganglia - cluster of cell bodies of individual neurons
Sensory neurons... (afferent neurons) - external stimuli from receptors toward CNS
Interneurons... integrate & relay sensory input to motor neuron
Motor Neurons... (efferent neurons) - convert signals to effector cells = response
Pathway through Nervous system*

STRUCTURE of a NERVE CELL
Cell Body- is main part of neuron cell with cytoplasm & organelles
Dendrites*- short cylindrical outgrowths of cell Body
- carry signals (electrical impulses) into cell body
Axon**- long outgrowth of cell body - carry signals to next neuron
Schwann cell* - cells surrounding axon in vertebrates -
- produce myelin (sheath) membrane (components)
protein + lipid-like membrane insulation surrounding axon
Nodes of Ranvier* - space between successive Schwann cells
inter-node area is a non-myelinated area
speed of conduction - w/o myelin speed is less (5 m/sec)
w/myelin (100 m/sec or 200 mi/hr)

Multiple Sclerosis - degeneration of myelin sheaths
Synaptic Knob* - enlarged ends of neuron
- holds neurotransmitters in synaptic vesicles

Reflex Arc - hard wired, unconscious rapid response to external stimulus
involving spinal nerves & effector cell electrical impulses


The electrical properties of cells: resting & action potentials

RESTING POTENTIAL - the characteristic electric charge
exhibited by a cell at rest... most often negative (-)

potential - (in electrical terms) is amount of electrical charge
at one point in an electric circuit compared to some other
point in the same circuit measured with a volt-meter (multi-meter*)

How to measure membrane potentials* in cells - microelectrode* pic*
inside vs. outside of cells
SGA - 65 to - 70 mVi
Frog muscle fibers - 90 mVi
Nitella (algae) - 150 mVi
Valonia (algae) + 15 mVi


Causes of Resting Potential... -65 mV inside for SGA ...
ion distributions* - all of which make inside of cell negative (-) HOW ?
ENa = +62mVi 150/15 = 10
Nernst Emv = +/- 62 log10 [Co]/[Ci] EK = -92mVi 5/150 = 0.033
ECl = -65mVi 120/10 = 12

1. active transport of Na & K...* high Na outside [3] & high K inside [2]
2. differential permeability* of K (faster out) & Na (slower in) = inside (-)
3. lots of protein anions* (-) at cell pH, thus inside more (-) then outside
4. normal diffusion of* Cl- into the cell



ACTION POTENTIAL -
- a self-propagating change in the RP voltage across membrane of nerve cells...
- name given to changes in electrical charges that occur during the
stimulation of a nerve cell,
- usually visualized graphically from an oscilloscope* recording [graph]

PROPERTIES of an AP...
... requires a living cell, i.e., requires O2 for metabolism
eliminated by metabolic poisons, such as cyanide
... is measured using microelectrodes impaled into cells
... has a threshold - minimal amount of stimulus needed to "fire" an AP
... is an "all-or-none" phenomena, either yes or no, no in-between
... is very rapid - time course = 2-3 msec

EVENTS DURING an AP oscilloscope trace* graph [Gasser & Erlanger]
depolarization* - cell goes from inside negative (-) to inside positive (+)
Na channel opens - Na floods in* --> -70mV to +58mV
repolarization* - Na channels close & K channels open [returns to inside (-)]
K follows diffusive gradient & K floods out* of cell
hyperpolarization* - "undershoot" of resting potential (-75mv)
refractory period - time before another AP can 'fire'
current changes during an AP* and overall* mechanism*


CONDUCTION of an AP along an axon
local spreading of electric charge depolarizes* adjacent membranes
change in membrane permeability of adjacent non-myleinated region
leads to an autocatalytic - "domino effect"............ figure*

Synaptic Transmission...
synapse - functional connection between neurons allowing transmission of
AP's between cells: can be electrical or chemical
synaptic cleft - open space between neurons [ 10 to 20 nm across ]
across which a chemical neurotransmitter may diffuse
synaptic knob - site of vesicles holding neurotransmitter at end of axon
synaptic vesicle - holds neurotransmitters (ex: acetylcholine)
action potentials trigger release of neurotransmitters*
pre-synaptic side - releases neurotransmitter
post-synaptic side - has a receptor which binds transmitter and ...
... ion channels open - leads to change of potential charge
on the post-synaptic membrane ----> new AP
removal of stimulus - an enzyme destroys neurotransmitter: ex. "ACH-ase"



Post-synaptic responses:

EPSP - excitatory post-synaptic potential (-15mVi)
excitatory PSM neurons --> open Na channels --> inside + --may--> AP

IPSP - inhibitory post-synaptic potential (-75mVi) figure*
inhibitory PSM neurons --> opens Cl channels - in -> more - --> no AP
--> opens K channels - out -> more - --> no AP

AP - all or none 120mv depolaorization/repolarization (-65 to +62 mVi)

MEPP - minature end-plate potential (-2 to 5 mVi)
small membrane depolarizations due to vesicle fusions with pre-SM
integration of impulses* & multiple innervations*
summation of impulses* & temporal/spatial summations*

What the fuck do you expect when the store is already closed?

Wow. Things like that really kind of belittle the entire civil rights movement. "I'm Oprah. I'm black. And because I showed up at your boutique fifteen minutes after closing, and you don't let me in, that means that you're being discriminatory."

What the fuck, Oprah. What the fuck.

OMG ARMAGEDDON!!!

I will not cry. I will not cry. This is not a massive government coverup story circulated to make us all unworried about our impending doom. It's not an asteroid the size of Texas.
It's not, dammit. *hides under bed*

More death in Iraq

I don't get it. I mean, I get it, but I don't. What is blowing yourself up going to accomplish in the big scheme of things?

The Turin Shroud is a fake

I love science.
..........

Kind of sickish. If Quinn gave me his germs, I'm going to kill him.