kolbintro6e_lectureslides_ch03_UPLOAD

What Are the Nervous System’s Functional Units?

• Chapter 3 of the textbook "Introduction to Brain and Behavior" by Kolb, Whishaw, and Teskey.

Overview of the Nervous System

• The nervous system is made up of complex structures that include cells that perform various functions.

• Key focuses:

  • Cells of the nervous system.

  • Internal structure of a cell.

  • Relationship between genes, cells, and behavior.

Cells of the Nervous System

Historical Perspectives

• Early 1900s Debate:

  • Golgi's view: Proposed that the nervous system was a continuous network called a "nerve net."

  • Cajal's hypothesis: Argued for the neuron hypothesis; suggested the nervous system is made of discrete cells (neurons).

Cajal's Contribution

• Cajal used the Golgi stain to demonstrate the structure of discrete cells, solidifying the neuron hypothesis.

• Neurons are considered the fundamental units of brain function.

Basic Structure of a Neuron

• Cell Body (Soma): Core region containing the nucleus.

• Dendrites: Branching extensions that collect information from other cells.

  • Derived from the Greek for "tree."

• Axon: Main projection that carries messages to other neurons.

  • Only one axon per neuron, but many dendrites can exist.

Neurons: The Basis of Information Processing

Functional Groups and Networks

• Neurons work in groups, forming neural networks that connect various regions of the brain and spinal cord.

• Mapping the human brain's connectivity is an ongoing research goal.

Subdivisions of Neurons

• Dendrites: Information gatherers.

• Cell Body: Integrates information using the nucleus to process inputs.

• Axon: Transmits processed information to other neurons.

Major Parts of a Neuron

• Dendrites from neighboring neurons.

• Dendritic spine: Increases the surface area for synaptic connections.

• Axon hillock: Junction between soma and axon; where action potentials begin.

• Axon Collaterals: Branches of an axon for wider signal distribution.

• Teleodendria & Terminal Button (End Foot): End of the axon that communicates with other neurons at the synapse.

Information Flow Through a Neuron

• Dendrites: Collect information from other neurons.

• Cell Body: Integrates incoming information.

• Axon: Sends processed information to the next neuron.

Types of Neurons

1. Sensory Neurons

• Carry information from sensory receptors to spinal cord.

2. Interneurons

• Connect sensory inputs and motor outputs within the CNS.

3. Motor Neurons

• Transmit signals from the brain and spinal cord to muscles.

Neuronal Networks and Behavior

• Sensory neurons collect information and relay to interneurons, which connect to motor neurons for behavioral outputs.

• Networks are structured for input, association, and output.

Neuron Excitation and Inhibition

• Neurons receive both excitatory and inhibitory signals.

• They sum these signals to determine activity, leading to complex behavioral outputs.

Examples of Neuronal Behavior

Barbara Webb’s Robot Cricket

• The robot uses simple rules to mimic behavior based on sound detection and corresponding motor activation.

Glial Cells: Support Structures in the Nervous System

• Five types of glial cells:

  • Ependymal Cells: Secrete cerebrospinal fluid (CSF).

  • Astrocytes: Provide structural support, transport nutrients, and help form the blood-brain barrier (BBB).

  • Microglia: Act as the brain's immune system, removing debris and monitoring health.

  • Oligodendroglial Cells: Myelinate CNS axons.

  • Schwann Cells: Myelinate peripheral nerves.

Internal Structure of a Cell

• Cells produce thousands of proteins, crucial for their functions, composed of water, salts, and ions.

Cell Membrane and Transport

• Cell Membrane: Acts as a barrier and gatekeeper, regulating substance movement via embedded proteins.

• Phospholipid Bilayer: Composed of hydrophilic heads and hydrophobic tails, facilitating selective permeability.

Chemistry of Cells

Elements, Atoms, and Ions

• Elements: Fundamental substances like oxygen, carbon.

• Atoms: The smallest units retaining element properties, composed of protons, neutrons, electrons.

Molecules

• Molecules form when atoms bond together; they retain the properties of the substances they are made of (e.g., water, salts).

Protein Synthesis in the Cell

• Nucleus: Contains DNA; responsible for protein synthesis through transcription and translation processes.

• Ribosomes: Sites for protein assembly from amino acids based on mRNA instructions.

Genetic Information and Expression

• Gene: Segment of DNA responsible for encoding proteins.

• Genetic mutations can affect traits, potentially leading to disorders.

Disorders and Genetic Impact

• Genetic defects like Tay-Sachs and Huntington's disease showcase the impact of alleles and genetic mutations on brain function.

Epigenetics and Behavior

• Epigenetic factors influence gene expression based on environmental interactions.

• Phenotypic plasticity and the epigenetic code explain variability in trait expression among individuals.