Intro to neurobiology

Overview of Cellular Structures and Functions

Body Cells: Different cells in the body have various shapes and sizes, reflecting their specific functions. However, all cells contain cellular cytoplasm.

Definition: Cytoplasm is a viscous substance that fills the cell, resembling a liquid and contains a salt concentration, giving it a slightly salty taste.
Components: It houses essential organelles and the nucleus, which are crucial for cell function.
- Organelles: Specialized structures within the cytoplasm that perform distinct functions. We'll discuss some organelles in detail later.

Location: Positioned away from the dendrites, typically found at the beginning of the axon.
Function: The axon hillock is distinguished by its long projection from the soma (cell body) and is responsible for carrying information from the neuron to adjacent cells (neurons or other cell types).

Function: The axon terminal's role is to transmit signals to other cells, and understanding its location is crucial for grasping neuron communication.

Synapses: The junctions between neurons where communication occurs. These are crucial for neuronal signaling.
Myelin: Described as a wire-like substance of insulation; it is part of the neuron structure that facilitates efficient transmission of electrical signals. Myelin is crucial for the rapid conduction of impulses along the axon.

Gene Definition: Genes are instruction documents encased in DNA; each cell contains a universal set of instructions.
- Human Genes: Humans have approximately 25,000 genes, which provide specific instructions for the production of cellular components.
Junk DNA: The majority of DNA is not part of a gene and was once referred to as "junk DNA." It plays various roles and results from different cell divisions through development.

Cellular Heterogeneity: Despite all cells containing the same set of genes, they express different genes based on their function. For example, lung cells and neurons can access the same genetic instructions, yet they function differently.
- Analogy: Similar to how students at Smith college may access the same library resources but study different majors, cells utilize the same genetic material to fulfill distinct functions.
Cell Regeneration: Although cells like liver cells renew themselves over time, neurons are unique in that they are not replaced.

Neuronal Lifespan: Neurons present at birth remain the same throughout a person’s life; they do not regenerate like other cells do. Thus, the neurons humans have are the same ones they are born with.
Myth of Cell Renewal: It's a common belief that all cells are completely renewed every seven years, which is not applicable to neurons. Skin cells renew, but neurons do not.
Significance of Neurons: Neurons are critical due to their non-renewable nature, and they play an important role in brain function and overall neural communication.

Electrical Transmission: Neurons rely on unique properties to conduct electrical signals, which can be measured by observing the transmission speeds of electrical impulses within nerves.
Experimental Confirmation: Historical experiments validated that neurons do not share cytoplasm but instead function distinctly, requiring a fundamental understanding of how neuronal signaling works.

Pharmacological Effects: Certain drugs can influence neuronal activity, exemplified through various experiments assessing how drugs impact neurons when isolated from other cellular contexts.

Software vs. Hardware: The interaction between neuronal structure (hardware) and neuronal function (software) can illustrate limitations and potentials within biological systems. An analogy can be drawn from automotive mechanics to provide a clearer understanding of biological system functions.

Included Resources: Additional materials such as videos and animations are referenced for enhancing understanding. Note that the readings for these chapters are sourced from a different textbook than discussed in the session.