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BIOSC 0715 (21)
Lecture 18

BIOSC 0715 Lecture 18: Lecture 17

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Biological Sciences
BIOSC 0715
Karen Curto

Lecture 15a and b 111716 Two types of cells Glia o Supporting cells o Structural reinforcement o Protection, insulation o Assistance in speeding up nervous conduction o Made predominantly of myelin Neurons o Chemical and electrical signals Two forces at work on ion distributionmembrane potential Concentration gradient Electrical (charge) gradient o Ions move across membrane toward their opposite charge or away from like charges At a membrane potential of 90mV for potassium: Rate of K+ moving down its concentration gradient to the outside of the cell equals rate of K+ moving down its electrical gradient to the inside of the cell There are more potassium channels, so resting potential (70mV) is closer to the potential for potassium than sodium (+60mV) Two types of signals, stimulus opens gate and causes either: Hyperpolarization of membrane potential o Inside becomes more negative Depolarization of membrane potential o Inside becomes more positive Undershoot = hyperpolarization Synapses two modes of transfer between one neuron and another Electrical cardiac cells o Gap junctions allow for spread of local ion currents between neurons; rare Chemical o Synaptic cleft o Synaptic vesicles of neurotransmitters Photoreceptors Rods more sensitive to light Cones color vision When a photon of light is absorbed by retinal, its conformation changes
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