C&M neur part 1

What are the two principal cell types in the nervous system?

Neurons and glia

What is Cytoarchitectonics?

The study used by Brodmann to divide the cerebral cortex into discrete architectural areas

How many discrete architectural areas did Brodmann identify in the human cerebral cortex?

44 areas (52 areas total, with 8 additional areas found in non-human primates)

What is the definition of Afferent signaling?

Signaling towards the CNS (Central Nervous System)

What is the definition of Efferent signaling?

Signaling away from the CNS

What three types of signals can neurons transmit?

Excitatory, inhibitory, or modulatory

Describe Principal Neurons (Projection Neurons).

They have long axons and participate in long-range connections (macrocircuits)

Describe Interneurons.

They have short axons and participate in local circuit function (microcircuits)

What are Macrocircuits?

Circuits involving a population of neurons that project from one brain region to another (e.g., prefrontal-amygdala)

What are Microcircuits?

Circuits reflecting local cell-cell interactions within a particular brain region (e.g., CeA-BLA)

What are the three general classifications of neurons by function?

Sensory, motor, and interneuron.

What is a way to classify neurons based on physiological action?

By their firing properties (e.g., bursting, tonic, quiescent).

What are the functions used to classify neurons

• whether the neuron is a relay neuron (macrocircuit) or a local interneuron (microcircuit)

• whether it is involved in sensory processing or correction of motor responses.

What are Sensory Neurons?

afferent neurons that collect information from sensory organs (eyes, nose, skin). They transform stimuli (chemical, physical, pressure) into electrical and chemical signals to inform the nervous system.

What is the primary function of a Motor Neuron?

Responsible for the direct or indirect control of effector organs such as muscles and glands. Their axons are efferent nerve fibers

What does it mean when sensory neurons are afferent

Gather information about what is going on inside and outside of the body and bring that information into the CNS so it can be processed

What does it mean that motor neurons are efferent

carry signals away from the CNS to produce movements

What are the tyoes of neurons

1. Pyramidal: large, pyramid-shaped brain cells that send long signals to other areas, mainly found in the cerebral cortex.

2. Non-pyramidal: smaller, varied-shaped brain cells that mainly act as local connectors and inhibitory regulators.

How is the Cerebral Cortex structurally organized?

It is divided into six distinct layers, each with specialized types of neurons and functions

What neurotransmitter is typically used by Cortical Pyramidal Neurons?

The excitatory neurotransmitter glutamate and/or aspartate.

What is the primary function of the Cell Membrane?

Separates intracellular and extracellular fluid and regulates movement of substances into and out of the cell (most cannot pass)

Describe the head and tail of a Phospholipid.

The hydrophilic head is phosphorous, polar, and water-liking.

The hydrophobic tail is made of lipids (fat-liking) and is non-polar.

Name the five major organelles contained within the Soma (Cell Body).

1. Nucleus

2. Mitochondria

3. Ribosomes

4. Endoplasmic Reticulum (Rough and Smooth)

5. Golgi Apparatus.

What is the role of the Nucleus?

Contains genetic material (DNA) and controls cell activities by regulating gene expression

What is the Nuclear Envelope?

A double membrane that encloses the nucleus and isolates its contents from the cellular cytoplasm

What is the main function of Mitochondria?

They are the sites for cellular respiration, converting sugar and oxygen to energy (generating ATP)

What is the Rough Endoplasmic Reticulum (RER) associated with?

Protein production. Ribosomes attached to its exterior make it appear rough

List three key functions of the Smooth Endoplasmic Reticulum (SER).

1. Synthesis of lipids and steroids

2. metabolism of carbohydrates

3. regulation of calcium concentration

What is the role of the Golgi Apparatus?

It packages, ships, and delivers proteins, often adding sugars as markers to guide them to their destination.

What part of the neuron is the "receiving portion"?

Dendrites, which channel electrical and biochemical signals to the cell body

What is the purpose of Dendritic Spines?

They expand the area of dendrites and are the points where inputs from other cells are directed (connection points)

What is the function of the Axon?

It is specialized to carry information and traffic cell components away from the cell body. 

Where is the Action Potential typically initiated?

At the axon hillock

What type of signal propagation occurs along the axon?

Signals propagate in an all-or-none fashion (called the action potential or nerve impulse)

What are Synapses?

Specialized connections where neurons communicate with each other. vsn be excitatory or inhibitory to increase or decrease activity in target neuron

How is Myelin formed, and what is its role?

Produced by glial cells, it acts as an insulator for large axons, affecting the speed of signal transmission

What are Nodes of Ranvier?

Small gaps between the myelin sheath that enhance the speed and efficiency of electrical signal propagation.

Name the three types of differentiated neuroglial cells.

Astrocytes, Oligodendrocytes/Schwann cells, and Microglia

what do radial glial cell contribute to

Neurogenesis and gliogenesis

what are the steps of CNS development

1. Neurogenesis: division of nonneuronal cells to produce neurons

2. Cell migration: movement of cells to establish distinct neuronal cell populations

3. Differentiation: formation of distinct neurons or glia

4. Synaptogenesis: establishment of synaptic contacts (axons and dendrites grow)

5. Neuronal cell death: selective death of many neurons

6. Synapse rearrangement: loss of some synapses and development of others; refine synaptic connections

What is the primary role of Radial Glial Cells in the developing CNS?

They act as a scaffold for neuronal migration and provide structural support during axon growth. They are also progenitor cells contributing to neurogenesis and gliogenesis

What are Progenitor Cells?

Descendants of stem cells that can differentiate into specific cell types. 2 types: NEPs and radial glial cells.

What cell type do most radial glia become at the end of cortical development?

Astrocytes, during the process of gliogenesis

Which type of astrocyte is found in gray matter?

Protoplasmic Astrocytes, which have many fine, complex processes that contact blood vessels (perivascular endfeet) and neurons.

Which type of astrocyte is found in white matter?

Fibrous Astrocytes, which have long processes and extensions that contact axons at the Nodes of Ranvier.

What is the Blood-Brain Barrier (BBB)?

A highly selective semipermeable membrane barrier separating the circulating blood from the brain and extracellular fluid in the CNS

How do astrocytes help form and maintain the BBB?

Astrocyte endfeet wrap around blood vessels and signal to endothelial cells, which then form tight junctions.

Which cells form the myelin sheath in the CNS?

Oligodendrocytes

Which cells form the myelin sheath in the PNS?

Schwann cells

How does Oligodendrocyte myelination differ from Schwann cell myelination?

Oligodendrocytes can myelinate different axons and several internodes per axon.

Schwann cells myelinate a single internode in a single axon

What process is regenerated at the Node of Ranvier?

Action potentials, using numerous voltage-gated sodium channels

Describe the function of Inflammatory Microglia (M1 phenotype).

They trigger astrocyte activation, cause damage to neurons, and disrupt the BBB, potentially leading to neuroinflammation

Describe the function of Anti-inflammatory Microglia (M2 phenotype).

They support neuronal survival, attenuate neurotoxic effects, restrict BBB permeability, and promote tissue repair.

Define Current.

The movement of electric charges through a conductor or space, defined as the net rate of flow of electric charge

Define Voltage (V).

The pressure that pushes electric charges through a conductor. It is a measure of potential energy per unit charge. measure between 2 points

Define Resistance (R).

The opposition that slows down the flow of electricity in a circuit

Define Capacitance.

The ability to store electrical charge

What are the charge carriers in an electrolyte (like the body)?

Ions

What is Potential Energy in a static electrical condition?

Energy stored due to an electric charge imbalance that has the possibility (potential) of release

What is a Conductor?

Materials (like copper or saltwater) whose outer electrons are loosely bound, allowing electric current to flow easily

What is an Insulator?

Materials (like glass, plastic, or fat) whose outer electrons are tightly bound, resisting the flow of electric force

State Ohm’s Law mathematically.

I = V/R (Current equals Voltage divided by Resistance)

How is current related to voltage and resistance according to Ohm's Law?

Current (I) is directly proportional to voltage (V) and inversely proportional to resistance (R)

How does capacitance affect current flow?

Capacitors accumulate and store electrical charge, introducing a time element so that current and voltage changes are no longer simultaneous

What two requirements are necessary for generating cellular electrical signals?

1. A concentration gradient of specific ions across the membrane.

2. The membrane is selectively permeable to some ions (via ion channel proteins)

Define Conductance (g) and its relation to Resistance (R).

Conductance is the inverse of resistance (g=1/R). Conductance increases when ion channels open.

What is the Resting Membrane Potential?

The constant voltage across the membrane when the cell is at rest (typically -40 to -90 mV)

Define Receptor Potential.

A change in potential that occurs when sensory neurons are stimulated

Define Synaptic Potential.

A change in potential caused when one neuron stimulates another across a synapse using neurotransmitter

Which charged particles are typically in higher concentration outside the cell?

Sodium (Na+) and chloride (Cl−)

Which charged particles/molecules are typically in higher concentration inside the cell?

Potassium (K+) and large proteins (A−)

Define Electrochemical Equilibrium (or Equilibrium Potential, Veq.​).

The point where the electrical force pulling an ion across the membrane is exactly equal and opposite to the chemical force pushing the ion down its concentration gradient, resulting in no net movement

What is the purpose of the Goldman equation?

It is an extension of the Nernst equation used to calculate the membrane potential when multiple permeant ions (and their respective permeabilities) are taken into account

How does the Na+–K+ pump maintain the resting potential?

It extrudes Na+ from the intracellular fluid and injects K+. This is a form of active transport.

Define Concentration Gradient (in terms of movement).

The difference in substance concentration that allows the substance to diffuse from higher concentration to lower concentration

Define Diffusion.

The movement of particles (like ions) from high to low concentration through random motion

What does the Nernst equation calculate?

The equilibrium potential (Veq.​) for a given ionic species, based on its concentration inside and outside the neural membrane

How do closed ion channels affect circuit resistance in the membrane?

They act as small resistors; therefore, more closed channels lead to a higher overall resistance.

Why do large proteins (A−) remain inside the cell, contributing to the negative resting potential?

The membrane is relatively impermeable to large molecules, so no channels are large enough to allow these negatively charged proteins to leave