BioPsych : Unit 1-2

Neuron

Cells that transmit information through electrical and chemical signals; the basic building blocks of the nervous system.

Soma (Cell Body)

The cell body of a neuron that contains the nucleus and organelles; responsible for maintaining the life of the cell.

Axon

Long, slender projections of a neuron that transmit electrical impulses away from the soma to other neurons or muscles.

Myelin Sheath

A fatty insulating layer around axons that increases the speed of electrical signal transmission.

Dendrites

Branch-like extensions of the neuron that receive signals from other neurons.

Nodes of Ranvier

Gaps between the myelin sheath segments where action potentials are regenerated, speeding up signal transmission.

Axon Terminals

Small knobs at the end of axons that release neurotransmitters into the synapse.

Glia Cells

Support cells in the nervous system that provide structural and metabolic support for neurons.

Astrocytes

Star-shaped glial cells in the CNS that support neurons, form the blood-brain barrier, and regulate nutrient transfer.

Microglia

Immune cells of the CNS that remove waste, damaged neurons, and pathogens.

Ependymal Cells

Glial cells that line the brain's ventricles and produce cerebrospinal fluid (CSF).

Oligodendrocytes

Glial cells in the CNS that form the myelin sheath around multiple axons.

Satellite Cells

Glial cells in the PNS that surround neuron cell bodies in ganglia and regulate the environment around them.

Schwann Cells

Glial cells in the PNS that form the myelin sheath around axons.

Central Nervous System (CNS)

Consists of the brain and spinal cord; processes and integrates information.

Peripheral Nervous System (PNS)

All nerves outside the CNS; connects the CNS to limbs and organs.

Sensory Division (Afferent Division)

Carries sensory information from the body to the CNS.

Motor Division (Efferent Division)

Carries commands from the CNS to muscles and glands.

Somatic Nervous System

Part of the motor division; controls voluntary muscle movements and transmits sensory info to the CNS.

Autonomic Nervous System

Part of the motor division; controls involuntary body functions like heartbeat, digestion, and breathing.

Sympathetic Division

Branch of the autonomic nervous system that prepares the body for “fight or flight” responses.

Parasympathetic Nervous System

Branch of the autonomic nervous system that promotes “rest and digest” activities.

Afferent

Signals going toward the CNS (sensory input).

Efferent

Signals going away from the CNS (motor output).

Neurotransmitters

Chemical messengers released from neurons to transmit signals across a synapse to another neuron, muscle, or gland.

Cell Membrane

The lipid bilayer surrounding a cell that regulates what enters and exits, and helps maintain resting potential in neurons.

Voltage

An electrical potential difference between two points; in neurons, it's the difference in charge across the cell membrane.

Polarization

A state where the inside of the neuron is more negatively charged than the outside.

What is the function of the blood-brain barrier?

To protect the brain from harmful substances in the blood while allowing essential nutrients to pass through.

How can chemicals get past the blood-brain barrier?

By being small and fat-soluble, or through specialized transport proteins (e.g., glucose transporters, active transport)

Is sodium more concentrated inside or outside the neuron?

Outside the neuron.

Is potassium more concentrated inside or outside the neuron?

Inside the neuron.

Is chloride more concentrated inside or outside the neuron?

Outside the neuron.

What is the charge of potassium?

+1 (positive charge).

What is the charge of sodium?

+1 (positive charge).

What is the charge of chloride?

-1 (negative charge).

Where are the negatively charged proteins located?

Inside the neuron; they contribute to the negative resting membrane potential.

What is meant by resting potential?

The electrical charge difference (-70 mV) across the neuron's membrane when it is not sending a signal.

Why are a concentration gradient and a semipermeable membrane required for resting potential?

The concentration gradient allows ions to move from high to low concentration, and the semipermeable membrane controls ion flow, maintaining charge separation.

Sodium-Potassium Pump

An active transport mechanism that moves 3 Na⁺ ions out and 2 K⁺ ions in, using ATP, helping maintain the resting potential.

What is depolarization?

A decrease in membrane potential where the inside of the neuron becomes less negative (more positive) than the resting potential.

. What is hyperpolarization?

An increase in membrane potential where the inside of the neuron becomes more negative than the resting potential.

What is an action potential?

A rapid, all-or-none electrical signal that travels along the axon, caused by the movement of ions across the membrane.

What is the refractory period of a neuron?

A period after an action potential when a neuron is unable (absolute) or less able (relative) to fire another action potential.

Name two characteristics of an axon that will affect the speed of an action potential.

Axon diameter – larger diameters conduct faster.

Myelination – myelinated axons conduct faster.

How does myelination increase the speed of an action potential?

By allowing the action potential to "jump" between nodes of Ranvier in a process called saltatory conduction.

What happens to action potentials in the presence of tetrodotoxin or local anesthetics?

They are blocked because these substances prevent sodium channels from opening, stopping depolarization.