The Neuron: Application of Cell Transport Concepts

Where are neurons found?

the nervous system

Neuron function

depends on membrane structure and the regulated transport of ions across the plasma membrane

what are neurons?

specialized cells found throughout the nervous system that transmit information through electrical signaling

image of a neuron

Dendrites

receive incoming signals from other cells

Axon

conducts electrical signals along the axon membrane

Myelin Sheath

-Insulates the axon and increases the speed of signal transmission

-fat is a good insulator

-30 wraps

Nodes of Ranvier

gaps in the myelin sheath where ions cross the membrane

Axon terminals

transmits signals to other cells

Schwann cell

protects nerves by forming myelin wrapped around them

electrical signals

-long distance communication along the neurons membrane

-generated by regulated ion movement across the neurons plasma membrane

-travels along the neuron

-within

chemical signals

-short distance communication between cells

-acts as synapses

-between

information flow

from a presynaptic cell (a neuron) to a postsynaptic cell (a neuron, muscle, or gland cell)

membrane potential

-every cell has a voltage (difference in electrical charge) across its plasma membrane called membrane potential

-changes in membrane potential act as signals, allowing neurons to transmit and process information

resting potential

-the membrane potential of a neuron not sending signals

-many Na (sodium) ions are located outside the neuron, while many K (potassium) ions are located inside the neuron

-the inside of the neuron is more negatively charged than the outside, creating a difference in electrical charge across the plasma membrane (because of channels there are more positives leaving)

what type of transport are channels?

passive: facilitated diffusion

what do the concentration gradients represent?

chemical potential energy

sodium potassium pumps

-uses the energy of ATP to maintain these K and Na gradients across the plasma membrane, not the action potential itself

-for every cycle: 3 Na are pumped out, 2 K are pumped in

what type of transport are sodium potassium pumps

active transport protein

Action potential change in ion movement order

1) resting state

2) depolarization

3) rising phase of the action potential

4) falling phase of the action potential

5) undershoot