anat & phys lecture 15

function of the nervous system

generate and process information

first level of complexity

the binary system: 0 vs 1/neuron at rest VS neuron at action potential

• neuron is at a constant negative internal resting state of -80 mV

• membrane potential: the difference in electrical state between the inside (axon) of a neuron and the extracellular world

• action potential: neuron goes from a negative state to a positive state and then back to negative state

action potential

each action potential takes 2 miliseconds

a neuron can fire 50-75 action potentials per second

next level of complexity

more neurons (100 billion neurons)

• each neuron is a processor that can generate 50 action potentials per second

• still at binary electric states

next level of complexity

the conversion of electrical signal to a chemical signal

• the electrical state only exists inside the axon and the electrical state can’t be communicated with other cells so in order to communicate the information that exists whether the neuron is at rest or at action potential the electrical signal has to be transduced into a chemical signal

• transduction of the electrical signal to a chemical signal occurs at the synapse and requires neurochemicals

  • there are 100s neurochemicals but only 10 neurotransmitters because only a few can be used to communicate between neurons and cells

next level of complexity

take the chemical signal to create a change in cellular function

• neurotransmitter receptors: changes the chemical signal to initiate a change in the neuron or cell

  • hundred types of neurotransmitter receptors

next level of complexity

circuits: neurons don’t act individually they are wired into circuits allowing for more complex function

example:

• A activates B → B activates C → C activity goes up

• A inhibits B → B is not on → no activity of C

• A activates B → B inhibits C → C activity goes down

next level of complexity

structures: have multiple circuits so allows for more complex function

• example: amygdala

next level of complexity

systems: multiple structures so allows for more complex function

• example: limbic system

next level of complexity

emergence: the collective activity of multiple systems so there fore more complex function

in all complexity and functionality…

plasticity is found

neuroplasciticy: the capacity of the nervous system to change as a consequence of prior activity

• only some parts of our nervous system are supposed to be plastic because some are supposed to have limited biological ranges to keep the nervous system functioning within a narrow range and keep body functioning properly

two types of cells found in the nervous system

glia: 10 times more glia than neurons, creates the environment that neurons live in

neurons: give rise to the actual physiological activities that are responsible for the nervous system function

neurons

• cell body: just like other cells has a nucleus, cytoplasm, organelles, endomembrane system

• how neurons differ from other cells: amitotic, non-zero resting membrane potential, unique morphology

unique morphology of a neuron

different processes: axons and dendrites

• axons: generates, propagates, transduces action potential

• dendrites: receives incoming information from other cells/neurons with neurotransmitter receptors

efferent signals

information can only go one way (away from cell body and to the synapse)

• outgoing information, action potential is going down the axon and away from the cell body

afferent signals

information that the neuron is receiving from other cells and other neurons

• incoming information, involves neurotransmitters binding to the neurotransmitter receptors on the dendrites, towards the neuron