Psychology 2822 - Chapter 2 (Structure and Function of Cells of the Nervous System)

Central Nervous System

Consists of the brain and spinal cord.

Peripheral Nervous System

Consists of all nerves outside the brain and spinal cord.

Nerves

Bundles of axons connecting the rest of the body with the central nervous system.

12

The amount of cranial nerves.

31

The amount of spinal nerves.

Sensory Neurons

Neurons that carry information from the peripheral nervous system to the central nervous system.

Motor Neurons

Neurons that carry output information to the muscles from the central nervous system to the peripheral nervous system.

Interneurons

Neurons that relay information within the central nervous system on local networks or tracts.

Neurons

Cells that process and transmit information with each other and then body by releasing chemicals (neurotransmitters) and generating action potentials.

Glial Cells

Cells that support and protect neurons by supplying energy and nutrients, forming myelin sheathes and the blood brain barrier and synthesize neurotransmitters; do not generate action potentials.

Astrocytes

"Star-shaped" glial cells that form the blood brain barrier, supply nutrients to neurons, engulf and digest debris using phagocytosis and form scar tissue (gliosis) following injury.

Phagocytosis

The process of engulfing and digesting debris used by astrocytes and microglia.

Area Postrema

A region of the brain where the blood brain barrier is weaker.

Gliosis

The process by which astrocytes form scar tissue following injury to the brain.

Oligodendrocytes

Glial cells that form the myelin sheath around axons to create nodes of Ranvier that are only in the central nervous system.

Schwann Cells

Glial cells that form the myelin sheath within the peripheral nervous system.

Microglia

Glial cells that engage in phagocytosis to protect the brain from invasive agents and secrete pro-inflammatory chemicals like cytokines.

Soma

The part of the neuron that integrates incoming signals (decides whether cells "fire") and directs cell function.

Dendrites

The part of the neuron that transmits incoming signals to soma with graded potentials.

Axon

The part of the neuron that generates action potentials.

Terminal Buttons

The part of the neuron that releases neurotransmitters and forms synapses with other neurons.

Myelin Sheath

The part of the neuron that surrounds and insulates axons, improving conduction of action potentials.

Nucleus

The structure within a neuron that contains chromosomes consisting of deoxyribonucleic acid (DNA) and transcribes genes for protein synthesis.

Cytoplasm

A structure within a neuron that contains organelles such as mitochondria (generates ATP for energy) and ribosomes (translation).

Mitochondria

An organelle within a neuron responsible for generating ATP, used for energy.

Cytoskeleton

The structure within a neuron that includes microtubules (protein strands that support vesicles).

Action Potentials

A wave of changes polarity from negative to positive inside an axon that begins at the axon hillock and travels to nerve terminals.

Axon Hillock

The origin of action potentials.

Resting Membrane Potential

The electrical charge of a neuron before an action potential is generated.

-70mV

The value of resting membrane potential.

Depolarization

Occurs when a neuron becomes less negative on the inside than the outside, travelling towards the firing threshold.

Firing Threshold

The point at which a neuron becomes sufficiently depolarized and the inside of the neuron suddenly becomes positive.

-55mV

The value of the firing threshold.

+40mV

The positive value during an action potential.

At rest

The state of a neuron when there is more Na+ outside the cell and more K+ inside the cell.

Force of Diffusion

The process in which ions move from an area of high to low concentration during an action potential.

Electrostatic Pressure

The attractive force that pulls oppositely charged Na+ ions into the negatively charged cell during an action potential.

At firing threshold

The point at which voltage-gated Na+ channels along the axon open and allow Na+ to enter the axon rapidly; as the inside of the cell becomes positive, K+ ions exit the neuron to return the cell to negative.

Closed

The position of the ion channels at rest.

Na+, then K+

The ion channels that open at the firing threshold (in order).

Refractory Period

A period of inactivity after a neuron has fired in which a neuron cannot generate another action potential until resting membrane potential is re-established.

Sodium-Potassium Pump

A transport protein that requires energy to transport 3 Na+ ions out and 2 K+ ions in to a cell to return the inside fo the cell to resting membrane potential.

All or None Law

A law that states neurons never partially fire; an action potential only occurs if the firing threshold is reached and is always the same size along the axon.

The Rate Law

A law that states the strength of a stimulus is represented in the nervous system by the rate of firing of an axon, not the magnitude of the potential.

Saltatory Conduction

The process in which the action potential "skips" along the axon at the Nodes of Ranvier that increases the overall speed of conduction compared to non-myelinated axons.

Synapse

The junction in which neurotransmitters are released after an action potential arrives at the terminal buttons.

Post-Synaptic Receptors

Receptors on adjacent neurons within a synapse that can cause depolarizing or hyper polarizing effects.

Axodendritic

A synapse on the dendrites of post-synaptic neurons.

Axosomatic

A synapse on the somas of post-synaptic neurons.

Axoaxonal

A synapse on the axons of post-synaptic neurons.

Ca++

The chemical that enters a pre-synaptic cell to initiate the release of neurotransmitters.

Vesicles

Pockets that store neurotransmitters to protect them from intercellular enzymes that fuse with the pre-synaptic membrane.

Pores

Areas on the pre-synaptic membrane that open, in which molecules of neurotransmitters are expelled into the synaptic cleft.

Post-Synaptic Receptors

The area to which neurotransmitter molecules bind after diffusing across the synapse from areas of high to low concentration.

Reuptake

The removal of a neurotransmitter from the synaptic cleft back into the presynaptic neuron through the terminal button.

Enzymatic Deactivation

Deactivation accomplished by an enzyme that degrades neurotransmitter molecules; acetylcholinesterase deactivates acetylcholine.

Ionotropic

A receptor that is coupled to a ligand-gated ion channel that has immediate effects and a short duration; an ion channel opens and the ion enters the cell, not the transmitter.

Metabotropic

A receptor that is coupled a G protein that activates a second messenger within cells in which changes take longer to begin and last longer.

Autoreceptors

Receptors located on pre-synaptic neurons that respond to the neurotransmitter they release, regulating internal processes by inhibiting effects when the concentration of a neurotransmitter is too high.