Nerve Cells, Impulses, and Psychopharmacology: A Comprehensive Overview

Consilience

the principle of linking knowledge from different disciplines to form a strong, unified understanding

Physiological explanation

The immediate influence of behavior → description of an organism's structure and how its mechanisms work

Ontogenetic explanation

Developmental influences → description of an organism's development, from DNA code to the forms of different life stages

Functional explanation

Adaptive purpose → explanation for the characteristics of a species based on how they give a selective advantage

Evolutionary explanation

Evolutionary origins → description of the history of a species as reconstructed from its fossil precursors and DNA evidence

Neurons

Dendrites, soma, axon, myelin sheath, synapses, neurotransmitters, vesicles, presynaptic cleft, receptor sites, synaptic cleft, post synaptic membrane

Afferent axon

Brings information into a structure (a sensory neuron)

Efferent axon

Carries information away from a structure (a motor neuron)

Intrinsic neurons

Interneurons whose dendrites and axons are completely contained within a single structure like the amygdala or hippocampus

Dendritic spines

Some dendrites have _______ that further branch out and increase the surface area of the dendrite

Soma

Contains the nucleus, mitochondria, ribosomes, and other structures found in other cells → responsible for most of the metabolic work of the neuron

Axon

Thin fiber of a neuron responsible for transmitting nerve impulses toward other neurons, organs or muscles

Myelin sheath

An insulating material that covers some neurons with interruptions known as the nodes of Ranvier

Glia

The other major unit/cell of the nervous system → there are about an equal amount of neurons and glia in the brain

Oligodendrocytes

Cells that build the myelin sheath in the brain and spinal cord

Schwann cells

Cells that build the myelin sheath outside the PNS

Astrocytes

Help synchronize the activity of the axon by wrapping around the presynaptic terminal and taking up chemicals released by the axon

Microglia

Remove waste material and other microorganisms that could prove harmful to the neuron

Radial glia

Guide the migration of neurons and the growth of their axons and dendrites during embryonic development

Ependymal cells

Produce the cerebrospinal fluid that fills the ventricles

Blood-Brain Barrier

Surrounds the brain and blocks most chemicals from entering

Active transport

The protein-mediated process that expends energy to pump chemicals from the blood into the brain

Nourishment in Vertebrae Neurons

Need a steady supply of oxygen and 20% of all oxygen consumed by the body is used by the brain

Nerve Impulse

The electrical message that is transmitted down the axon of a neuron (action potential!)

Resting potential

Refers to the state of the neuron prior to the sending of a nerve impulse

Sodium-potassium pump

A protein complex that pumps three sodium ions out of the cells while drawing two potassium ions into the cell

Hyperpolarization

Increasing the polarization or the difference between the electrical charge of two places

Depolarization

Refers to decreasing the polarization towards zero

Action potential

A rapid depolarization of the neuron triggered when stimulation exceeds the threshold of excitation

Action Potential (AP)

A rapid rise and fall in membrane potential that occurs when a neuron is activated.

Sodium Channels

Channels that open to allow sodium ions to enter the neuron during an action potential.

Potassium Channels

Channels that open to allow potassium ions to flow out of the neuron, returning it to its resting state.

All-or-None Law

The principle that action potentials occur fully or not at all, regardless of the stimulus intensity.

Refractory Period

The time following an action potential during which a neuron resists the production of another action potential.

Absolute Refractory Period

The first part of the refractory period when the membrane cannot produce another action potential.

Relative Refractory Period

The second part of the refractory period when another action potential can occur but requires more stimulation.

Propagation of Action Potential

The transmission of the action potential down the length of the axon, regenerated at each step.

Nodes of Ranvier

Short unmyelinated sections of axons where action potentials are regenerated.

Saltatory Conduction

The process by which action potentials jump from node to node, speeding up conduction.

Multiple Sclerosis

A disease characterized by the destruction of the myelin sheath, leading to poor muscle coordination.

Synapses

The gap between presynaptic terminals and postsynaptic dendrites where neurotransmission occurs.

Presynaptic Neuron

The neuron that sends the signal across the synapse.

Postsynaptic Neuron

The neuron that receives the signal at a receptor site.

Excitatory Postsynaptic Potential (EPSP)

A positive graded potential that pushes the postsynaptic cell closer to the threshold for an action potential.

Inhibitory Postsynaptic Potential (IPSP)

A negative graded potential that pushes the postsynaptic cell further from the threshold for an action potential.

Spontaneous Firing Rate

The periodic production of action potentials by a neuron without synaptic input.

Spatial Summation

The cumulative effect of synaptic input from multiple locations triggering a nerve impulse.

Temporal Summation

The cumulative effect of repeated stimulation over time producing a nerve impulse.

Neurotransmitters

Chemicals that transmit signals across the synapse between neurons.

Exocytosis

The process by which neurotransmitters are released from the presynaptic terminal.

Reuptake

The process by which neurotransmitters are taken back into the presynaptic neuron for recycling.

Ionotropic Effect

When a neurotransmitter binds to a receptor and immediately opens ion channels.

Metabotropic Effect

When a neurotransmitter binds to a receptor and initiates slower, longer-lasting metabolic reactions.

Agonist

A drug that increases the actions of a neurotransmitter.

Antagonist

A substance that decreases the actions of a neurotransmitter.

Affinity

How well a drug binds to a receptor site.

Efficacy

The kind of response a drug produces after binding to a receptor.

Metabolic Tolerance

Tolerance that occurs when the body increases enzyme production to metabolize a drug more efficiently.

Pharmacodynamic Tolerance

Tolerance that occurs when neural function changes in response to a drug.

Caffeine

A psychoactive substance that stimulates the central nervous system and is absorbed quickly from the GI tract.