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Title: Nervous System
Description: overview of the nervous system and action potentials. Some senses but mainly action potentials.
Description: overview of the nervous system and action potentials. Some senses but mainly action potentials.
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Nervous system
• “Lines” (nerves) that the information travels along
• Action potentials
o Cell lined with phospholipid membrane
§ Fats don’t like charged things so ions need to go through channels that
allow certain things in and out
§ Potassium channels are open all the time
§ Voltage gated sodium or potassium channels are only open sometimes
• Charge between inside and outside of cell determines whether it is
gonna be open
Ions go from high to low concentration - diffusion
Sodium-potassium pump pumps sodium out and potassium in
Uses energy to move
Sodium and potassium are going against concentration gradient
These pumps are proteins
More positive on outside of cell than on inside when we start out
Na/K pump pumps out 2 K for every 3 Na in
Negative proteins are also in the inside- more negative in the inside
When voltage Na gate opens sodium rushes from high to low concentration so it goes inside the
cell and then the voltage across the cell membrane is flipped
Inside is more positive than the outside now
When Na voltage gated channels are closed because it got so positive inside and at the same time
K channels opened and K rushes from high to low concentration so the K goes out and the cell
goes back to being more negative on the inside
When K voltage gated channels close the Na/K pump pumps sodium back out and
potassium back in like from the start
The moving of these ions is how we get action potentials that move across neurons
How do you measure action potentials??
Resting potential is the negative charge of the inside of the cell not having any action
potentials
Negative value relative to the outside
When the charge goes up it’s an action potential - sudden large transient reversal
This whole process is really quick- milliseconds
•
•
Sensory transduction = change in membrane potential of the receptor cell in response to
a specific stimulus
a
...
Membrane potential of the receptor cell is altered (receptor potential)
§ Graded potentials
Receptor potential spreads to the axon hillock where the action potential is generated and
travels down the axon to the CNS
Receptors convert stimuli to neural signals that are transmitted to the CNS for processing
and interpretation
• Receptor cells must generate action potentials to signal over long distances
...
The receptor cell releases a neurotransmitter that induces a postsynaptic cell to generate
an action potential
• The rate at which action potentials are fired depends on the magnitude of the receptor
potential, which depends on the mechanical stimulus
• The intensity of the stimulus affects how much neurotransmitter is released and how
many action potentials are generated
• Sensory receptor proteins respond to stimuli by directly or indirectly opening ion
channels
...
Ionotropic = protein receptor is an ion channel (mechanoreceptors and
thermoreceptors: touching, hearing, heat)
§ Ionotropic is faster because it directly opens the ion channel while
metabotropic has to induce more reactions further in the cell
• All sensory systems process information by action potentials
...
Vomeronasal organ has a pore that opens into the nasal cavity so when you sniff in it
pulsates and draws a sample of the nasal fluid over the chemoreceptors, sending information to
the olfactory bulb
§ 1
...
G protein is activated
§ 3
...
cAMP binds to and opens calcium channels
§ 5
...
Depolarization causes action potential
a
...
More odorant molecules bound the the olfactory receptor neurons induces more action
potentials at a higher frequency which increases the intensity of the smell
c
...
Chemoreceptors = taste buds
§ On papillae (the bumps on your tongue)
§ Microvilli are pores on taste buds that increase surface area
a
Title: Nervous System
Description: overview of the nervous system and action potentials. Some senses but mainly action potentials.
Description: overview of the nervous system and action potentials. Some senses but mainly action potentials.