Lecture3 Flashcards
First known reference to the brain?
Egyptian papyrus
Functions of the Diencephalon
vegetative functions - breathing, HR, BP, pH of blood, digestive, immune, nervous, body temp, hunger/thirst (involuntary)
Functions of the Telencephalon
think, feel, dislike (this), ability to do calculatons (cognitive functions, you do not need a telencephalon to live)
Typical Size of a Neuron
10 microns - 120 microns in diameter
Describe the basic historic review of neuroscience research
Philosophy (Psychology)–>Anatomy (Histology-Embryology)–>Physiology–>Molecular Biology (where it’s at now)
What is responsible for “head functions?”
pons, medulla, midbrain (brain stem)
Two Classes of Nerve Cells
neurons and glia
Anatomical Characteristics of Neurons
size (10-120 microns), shape (bi-, uni-, multi-), transmitter, intracellular organelles (highly metabolic)
Physiological Characteristics of Neurons
polarity/excitability, signal morphing, signal spread (AP), signal communication
Signal Morphing (Transduction)
using excitability, neurons can transduce physical stimuli into neural stimuli (touch, pressure, stress, temp, sound), neurons can change stimuli into ELECTRICITY
Signal Spread (Action Potential)
spread info over long distances through action potentials, membrane properties allows this communication to occur
Signal Communication (Synaptic Transmission)
communication between cells through neurotransmitters or neuromodulators
Four Zones of Basic Neuronal Morphology
input zone, integration zone, output zone, synaptic zone
Integration Zone
integrating information from other neurons, cell body (soma) is where most intracellular organelles are located, can get communications from 10,000 other neurons
Input Zone
dendritic tree, where synapses put in information, more branches = more synapses = more info, not myelinated
Output Zone
axon, each neuron only has one axon but may have many branches (collateral branches), <1 micron in diameter, may be myelinated
Synaptic Zone
synaptic bouton, will have connections with other neurons
Multipolar Neuron
large number of dendrites, large input zone, can be myelinated or not
Bipolar Neuron
two poles, one will act as a dendrite and one as axon, not myelinated, these are more rare
Unipolar Neuron
rounded cell body without dendrites, single bifurcated axon, central (axon) and peripheral (dendrite) branch, found in sensory ganglia, can be myelinated
Betz Cells
some of the largest in the brain (multipolar), give us control over the main functions in our body
Anatomical Characteristics of Glia
astrocytes, oligodentrocytes, microglia, schwann
Astrocytes
type of glia found in CNS, may be protoplasmic (gray matter) or fibrous (white matter)
Responsible for Formation of the Blood Brain Barrier
astrocytes (protoplasmic and fibrous)
Oligodentrocytes
myelin making cells in the CNS
Microglia
scavenger cells of the CNS, clean up dead cells
Schwann Cells
in the PNS, make myelin and clean up, basal lamina forms conduit which allows for regeneration
Which cells make myelin?
oligodentrocytes (CNS) and Schwann cells (PNS), they make myelin based on diameter of axon
Physiologocial Characteristics of Glia
structure/protection (primary), ion homeostasis, myelin formation, debris clearance
Why can PNS potentially regenerate but not CNS?
Schwann cells, PNS can regenerate through basal lamina (oligodentrocytes do not make a basal lamina)
Basic CNS Functions
collect and analyze information (transduction), react to information, store information as memory (protein), recall memories as appropriate, modify behaviors
Two Types of Axoplasmic Transport
anterograde (away from cell body) and retrograde (towards cell body) transport
Slow Anterograde Transport
“bulk flow,” 1 mm/day (same speed as regeneration in PNS), maintenance (no ATP)
Fast Anterograde Transport
specific membrane-bound organelles, 400 mm/day, synaptic/trophic functions (ATP needed)
Retrograde Transport
specific molecules, 200 mm/day, metabolic turnover, trophic interactions (ATP needed)
Axonal Transport Mechanism
kinesin with vesicles rolls down microtubules witin axon
1780 Luigi Galvani
animal electricity
1849 Emil Dubois-Reymond
nerve conduction
1925 Edgar Adrian
all-or-nothing principle
1938 Kenneth Cole and Howard Curtis
ionic fluxes
1945 Alan Hodgkins, Andrew Huxley, & Bernard Katz
NA+/K+ pumps-sliding filament theory
Resting Membrane Potential
-70mV is average, in reality it is constantly fluctuating, based on concentration gradient of all ions
Threshold
occurs when potential raises to -50mV, conformational change in NA+/K+ pump, opens and NA+ rushes in
Spike Peak
NA+ stops coming in (approx. +30-35mV), K+ starts leaving, begins repolarization process
Repolarization
K+ leaving cells
Hyperpolarization
overshoot in repolarization to about -90mV
Depolarizaton
positive after potential, back to -70mV
Action Potential Components
resting potential, threshold, spike peak, repolarization, hyperpolarizing (negative after potential), depolarizing (positive after potential)
Refractory Period
cannot have another AP, limit to spread of excitation due to this (can only have so many per unit time)
Approximately how long is one action potential?
4 msec
Membrane Cable Properties
AP gets weaker as it travels down the length of the axon as potential leaks out (myelin can allow for better conduction velocity)
Lambda
distance between where 100% current and enough leakage occurs for current to die out (37%)
Saltatory Conduction
counter current of flow down the axon, some ions are flowing in at one node and out at another, can only occur in myelinated axons
