9 - Cell-Cell Communication: Neurons

Central Nervous System

Peripheral nervous system

Neurons and ganglia

Neurons

Specialized nerve cells in the nervous system responsible for transmitting information through electrical and chemical signals

Glia cells

non-neuronal cells in the nervous system that provide support and protection to neurons

Function of neurons

Integrate incoming signals - to determine whether or not the information should be passed along

Communicate signals to target cells - other neurons, muscles, or glands

Neuron anatomy

Dendrites

Receive signals from neighboring neurons

Axon

Transmits signals over a distance

Axon terminal

Transmits signals to other neuron dendrites of tissue

Concentration gradient

The difference in ion concentrations between the inside of the neuron and the outside of the neuron

Neuron charge…

Negative

Neuron resting membrane potential…

-70 mV

Concentration of Na/K during resting potential…

There are more Na ions outside and more K ions inside the neuron

Size of action potential along the axon…

The size of the action potential remains the same as it travels down the axon

Synapse

The place where neurons connect and communicate with each other

Depolarizing

The inside of the cell becomes more positive

Hyperpolarizing

The inside of the cell becomes more negative (less positive)

Excitatory neurotransmitters

The change makes the target cell more likely to fire its own action potential

Inhibitory neurotransmitters

The change makes the target cell less likely to fire an action potential

Modulatory neurotransmitters

The change makes the target cell adjust or “tweak” the action potential

Microglia

Immune cells/macrophages

Oligodendrocytes

Myelinating cells in central nervous system (CNS)

Schwann cells

Myelinating cells in peripheral nervous system (PNS)

Astrocytes

Blood-brain barrier (touch neurons and capillaries)

Ependymal cells

Produce cerebrospinal fluid (CSF)

Gated Channels

Can be either open (allowing ions to flow through) or closed depending on the protein conformation

Voltage-gated channel

Ion channels in the cell membrane that open or close in response to changes in the membrane potential or voltage difference across the membrane

Ligand-activated channels

Sensitive to binding of ligand/signal; they undergo a change in shape when a neurotransmitter binds, causing the channel to open (this may either be inhibitory or excitatory)

Mechanosensitive channel

Sensitive to mechanical stress on membrane

Ratio of Na/K in/out

3 Na+ ions out for every 2 K+ ions inW

When does action potential occur (threshold value) ?

-55 mV