The Building Blocks of the Brain: Neurons

Flashcards covering the building blocks of the brain, including neuron structure, function, and supporting glial cells, as well as an overview of the nervous system divisions.

How many neurons are estimated to be in the human brain?

85-100 billion neurons

What is the estimated number of synapses in the human brain?

125 trillion to 1 quadrillion synapses

What is considered the single unit of the nervous system?

The Neuron

What is the primary function of neurons?

To form complex circuits and connections that integrate information to further distribute it to other regions of the brain.

What are the four major structural regions of a neuron?

Dendrites, Soma, Axon, Axon Terminals

What is the function of dendrites and where are they located?

Dendrites are extensions of the neuronal membrane at the Input Zone that receive information from other neurons through synapses.

What is the soma and what is its role?

The soma is the cell body of the neuron, which integrates received information to determine whether to send a signal.

What is the function of the axon and where is it located?

The axon is a single membrane extension from the soma that carries the neuron's electrical signal away from it, acting as the Conduction Zone.

What are axon terminals and what is their role?

Axon terminals are bulbs of membrane at the end of axons in the Output Zone where synapses form, sending information.

What is a synapse?

A synapse is the cellular junction at which information can be transmitted from a presynaptic onto a postsynaptic neuron.

What are the three main components of a synapse?

Presynaptic membrane, Synaptic cleft, Postsynaptic membrane

What is the presynaptic membrane?

The axon terminal of the transmitting neuron.

What is the synaptic cleft?

The gap between the presynaptic and postsynaptic neurons.

What is the postsynaptic membrane?

The dendrite or cell body of the receiving neuron.

What is the input zone of a neuron?

Where cellular extensions called dendrites are present.

What is the integration zone of a neuron?

The cellular body of a neuron, also called the soma, where the decision to produce a neural signal is made.

What is the conduction zone of a neuron?

Takes place at another cellular extension called the axon, where information can be electrically transmitted.

What is the output zone of a neuron?

Carried out in specialized swellings of the membrane at the ends of the neuron called axon terminals or terminal boutons, where the neuron transfers information to other cells.

What are dendritic spines?

Smaller swellings formed by dendrites that provide additional spaces to form more synapses.

Where is the neuron's electrical stimulus initiated?

At the soma (cell body).

What are axon collaterals?

Branches that an axon may form.

In what direction does the signal travel along an axon?

Unidirectionally.

What are the two broad categories of the nervous system?

Central Nervous System (CNS) and Peripheral Nervous System (PNS).

What does the Central Nervous System (CNS) consist of?

The brain and the spinal cord.

What are the main divisions of the Peripheral Nervous System (PNS)?

Somatic and Autonomic Nervous Systems.

What are the divisions of the Autonomic Nervous System?

Sympathetic and Parasympathetic Nervous Systems.

What is the primary role of the Sympathetic Nervous System?

Physiological arousal, preparing the body for action ('fight or flight' response).

What is the primary role of the Parasympathetic Nervous System?

Return to baseline arousal, preparing the body for recovery and repair ('rest and digest').

Which nervous system has shorter axons innervating the sympathetic ganglia?

The Sympathetic Nervous System.

Which nervous system has longer axons projecting to ganglia near the target organ?

The Parasympathetic Nervous System.

What is the primary role of glial cells?

To support neurons and maintain cellular homeostasis in the nervous system.

What are astrocytes and what are their functions?

Glial cells that support the blood-brain-barrier, synapses, and supply neurons with nutrients and essential molecules.

What are microglia and what is their function?

The immune cells of the brain; they act as scavengers.

What are oligodendrocytes and what is their function?

Glial cells that provide myelin to CNS neurons.

What are Schwann Cells and what is their function?

Glial cells that provide myelin to PNS neurons.

What are the four types of glial cells?

Astrocytes, Microglia, Oligodendrocytes, and Schwann Cells.

Why is neuronal shape and structure important?

It reveals clues about function and shape and function are interlinked.

What is one type of neuronal shape mentioned?

Multipolar, Bipolar, or Unipolar.

Do neurons contain common cellular machinery?

Yes, all common cellular machinery is present in the soma.

How do oligodendrocytes and microglia interact during CNS development?

They symbiotically modify myelin.

What is the primary functional difference between the Central Nervous System (CNS) and the Peripheral Nervous System (PNS)?

The CNS is responsible for integrating and processing information, while the PNS connects the CNS to the limbs and organs, transmitting sensory and motor information.