Brains, Neurons, and Membranes

Flashcards on brain evolution, functional neuron classes, neural conduction/transmission, cellular organelles, plasma membrane properties, and molecular chemistry.

Why did brains evolve from an evolutionary perspective?

• Brains evolved to generate adaptive behavior appropriate to current (and predicted) circumstances

• Appropriate behavior includes managing body energy budget to optimize functioning and stay alive

• Brain learns about circumstances by processing sensory information from outside itself

What are the three basic jobs of the nervous system and the corresponding neuron types that perform them?

Gathering sensory information (sensory neurons), processing and integrating information (interneurons), and producing actions in the internal or external environment (motor neurons).

What is the distinction between afferent and efferent neural pathways?

Afferent pathways bring sensory information from the peripheral nervous system toward the Central Nervous System (CNS), while efferent pathways send motor information away from the CNS to peripheral muscles or glands.

Where are interneurons located and how do they process information?

Interneurons are located within the CNS; they process information by combining signals sent from different neurons to generate new information and transmit it to other neurons.

What is the difference between neural conduction and neural transmission?

Neural conduction refers to a signal moving within a single neuron, whereas neural transmission refers to a signal moving from one neuron to another neuron.

What is cytoplasm and what is the environment inside a cell like?

Cytoplasm is the jelly-like watery fluid inside cells, which is actually very crowded and busy both inside and outside cells.

What functions do microtubules serve in a neuron?

Microtubules serve as an internal "skeleton" to support neuron shape and provide "tracks" to move substances along inside the cell.

Why are plasma membranes described as selectively permeable?

Because most fat-soluble substances can dissolve directly through the membrane and pass freely, while most water-soluble substances cannot dissolve through and require specialized protein "doors".

What is an ion channel in a plasma membrane?

An ion channel is a specialized protein molecule that acts as a selective "door" allowing specific water-soluble molecules to cross the plasma membrane.

What is the modern chemistry definition of a molecule?

A discrete group of two or more atoms held together by chemical bonds, that can exist as an independent entity.

What components make up an atom and its nucleus?

An atom consists of a nucleus containing protons (positive charge) and neutrons (no charge), which is orbited by electrons (negative charge).

What is the difference between a cation and an anion?

A cation is an ion with a net positive charge (fewer orbiting electrons than protons in nucleus), whereas an anion is an ion with a net negative charge (more orbiting electrons than protons in nucleus).

What is electrostatic pressure and how does it dictate charge interactions?

Electrostatic pressure is the invisible force ions exert on each other; identical charges produce mutual repulsion, while opposite charges produce mutual attraction.

Why is water ($\text{H}_2\text{O}$) considered a polar molecule?

Electrons are shared unequally and spend more time around the oxygen nucleus, making the oxygen end more negative and the hydrogen end more positive.

How does sodium chloride ($\text{NaCl}$) dissolve when added to water?

Water molecules exert electrostatic pressure on $\text{Na}^+$ and $\text{Cl}^-$ ions, surrounding each ion and pulling them away from each other into solution.

Why are lipids not water-soluble?

Lipids are non-polar, so there is no electrostatic attraction between lipids and water molecules; water molecules attract each other much more strongly, causing lipids to cluster together away from water.

What structural composition allows soap molecules to make grease dissolve in water?

Soap molecules have a water-soluble polar head and a lipid-soluble non-polar hydrocarbon tail.

What are the two structural parts of a phospholipid molecule and their distinct properties?

A water-loving (phosphate) head with a weak negative charge that repels fat, and two lipid-loving (fatty acid) tails that accept fatty substances and are repelled by water.

How do phospholipids arrange themselves when placed in an aqueous solution?

They spontaneously form a phospholipid bilayer ("fat sandwich") with hydrophilic heads facing outward toward water and hydrophobic tails facing inward forming the filling.

How do water-soluble and lipid-soluble substances pass through the phospholipid bilayer?

Water-soluble substances cannot pass through the fatty filling and require protein doors, whereas lipid-soluble substances can squeeze past the phosphate heads and dissolve through the fatty middle.