Midterm 1 Review Flashcards
neurons
brain consists of ~100 billion neurons
neuroglia
a glia:neuron ratio less than 1:1
synapses
anywhere from 1k to 10k synapses for each neuron
Brain cells broken into two groups:
neurons & neuroglia
4 types of glial cells
astrocytes, oligodendrocytes, microglia, ependymal cells
brain tissue broken down into
gray & white matter
gray matter
mostly unmyelinated neurons, most of which are interneurons; this is area of nerve connections & processing
white matter
mostly myelinated neurons that connect regions of gray matter to each other & rest of body. myelinated neurons transmit nerve signals much faster than unmyelinated axons. white matter acts as info highway of brain to speed connections between distant parts of brain & body.
neuroglia or glial cells
act as helper cells of brain; support & protect neurons
neuronal circuits are
rarely linear, frequently converge/diverge & are often bidirectional (reciprocal)
1-2% of human genes are
“brain-specific”
Cajal developed
“neuron doctrine”
4 functional zones of neuron
1) input
2) integration
3) conduction
4) output
1) zone of input in a neuron:
soma+dendrites
2) zone of integration:
axon hillock
3) zone of conduction:
Axon
4) zone of output
terminal buttons @ ends of axon
3 ions to remember
potassium K+
sodium Na+
calcium Ca++
potassium (K+)
20mM extracellular concentration
400mM intracellular concentration
1/20 extra/intra ratio
sodium (Na+)
440 mM extracellular concentration
50 mM intracellular concentration
9:1 extra/intra ratio
calcium (Ca++)
10mM extracellular concentration
0.0001 mM intracellular concentration
100,000:1 extra/intra ratio
sodium-pottasium pump (Na/K-ATPase)
moves 2 potassium ions into a neuron for every 3 sodium ions that it moves out, consuming 1 molecule of ATP
voltage gated Na+ channels______than voltage gated K+ channels; they also______.
open more quickly; close earlier
simaltaneous opening of both Na+ & K+ channels (overlap) is
metabolically inefficient
Absolute refractory period
starts @ -55mV & includes depolarization & repolarization (when AP happens)
relative refractory period
@ end of action potential & includes hyperpilarization (undershoot meaning it goes past the resting potential @ -70mV)
absolute refractory period
time from opening of Na+ activation gates until closing of inactivation gates; neuron cannot respond to another stimulus
relative refractory period
follows absolute refractory period. Na+ gates closed, K+ gates open & repolarization is ocurring. during this period only a strong stimulus can generate AP.
above threshold_______triggers AP by______________.
depolarization; opening voltage-gated Na+ channels
myelin sheaths
increase speed of AP propogation
nodes of ranvier
between myelin sheath have higher concentration of Na+ ion channels which help AP “leap” down axon faster than in unmyelinated axons
