Neurons, Synapses, and Signaling

Flashcards covering neurons, synapses, and signaling for module 14: the nervous system.

Cephalization

Clustering of neurons in a brain.

Neuron

The functional cell of the nervous system that generate & transmit electrical messages.

Dendrites

Conduct information in the form of electrical signals towards cell body.

Axons

Convert signals from the cell body into a neural impulse, produced by an action potential and conduct signals away from cell body.

Glial cells

Nervous system cells that are essential for the normal functioning of neurons.

Astrocytes

Structural support, facilitate information transfer, and increase blood flow to active neurons.

Schwann cells

Produce myelin sheaths in the PNS.

Oligodendrocytes

Produce myelin sheaths in the CNS.

Nodes of Ranvier

Impulse “jumps” from node to node → ↑ speed!

Central nervous system

Brain & spinal cord.

Peripheral nervous system

Everything outside CNS.

Motor system

Skeletal muscles, sensory & motor neurons, acetylcholine, and voluntary control.

Autonomic system

Glands, smooth muscle, cardiac muscle, acetylcholine & norepinephrine, involuntary control, and concerned primarily with homeostasis.

Sympathetic

“Fight or flight” and neurotransmitter is norepinephrine (post-ganglionic).

Parasympathetic

“Resting & digesting” and neurotransmitter is acetylcholine (post-ganglionic).

Neural impulses

An action potential is generated when a polarized neuron (unequal distribution of + and - charges inside and outside) is suddenly depolarized along its length.

Membrane potential

All living cells have an electrical charge difference across their plasma membrane.

Hyperpolarization

Inside becomes more negative (open K+. e.g.).

Depolarization

Inside becomes less negative (open Na+).

Graded potentials

Magnitude varies with the strength of the stimulus.

Action potential

A wave of depolarization.

Absolute refractory period

Na+ inactivation loops closed and CANNOT refire.

Relative refractory period

Na+/K+ pumps working and CAN refire with a very strong stimulus.

Myelin sheaths

Insulate (composed of lipids) and speed up impulse transmission.

Saltatory Propagation

The nerve impulse “leaps” from one node to the next.

Electrical synapses

Occur at gap junctions between neurons (cells physically connected).

Chemical synapses

Communication is via chemicals called neurotransmitters.

Presynaptic neuron

Releases neurotransmitter.

Postsynaptic neuron

Has receptors activated by neurotransmitters.

Inhibitory synapses

Make depolarization and a resulting AP less likely.

Temporal summation

Two EPSPs occur in rapid succession at a single synapse.

Spatial summation

EPSPs produced by different synapses can also add together.