UNIT TWO COMPREHENSIVE

Functions of Membrane Proteins

Transport, enzymes, signal transduction, cell recognition, intercellular joining, attachment to the cytoskeleton.

Semipermeable Membrane

Cell membranes allow selective passage of substances; some can pass freely, while others cannot.

Tonicity: Hypertonic

Cells lose water and shrink.

Tonicity: Isotonic

No net movement of water; cells remain the same size.

Tonicity: Hypotonic

Cells gain water and swell.

Active Transport

Transport that requires energy (ATP) to move substances against their concentration gradient.

Facilitated Diffusion

Transport of polar molecules across the membrane facilitated by proteins without the use of energy.

Sodium-Potassium Pump

Moves Na+ out and K+ into the cell; crucial for maintaining resting membrane potential and requires ATP.

Paracrine Signaling

Signals that act on nearby cells.

Stages of Cell Signaling

Reception, transduction, and response describe cellular communication processes.

Water-Soluble Hormones

Bind to receptors on the cell surface.

Lipid-Soluble Hormones

Pass through the membrane to interact with internal receptors.

Neurosecretory Cells

Neurons that release hormones into the bloodstream, coordinating nervous and hormonal signals.

Positive Feedback

Amplifies a response.

Negative Feedback

Reduces response to maintain homeostasis.

Neuron Structure: Dendrites

Receive signals.

Neuron Structure: Axons

Transmit impulses.

Resting Membrane Potential

Difference in charge across the membrane crucial for nerve signal conduction.

Action Potential Phases

Depolarization, repolarization, and hyperpolarization.

Core Functions of the Nervous System

Input, integration, and output.

Components of the Sensory System

Reception, transduction, transmission, and perception.

Photoreceptors

Detect light.

Mechanoreceptors

Detect pressure.

Thermoreceptors

Detect temperature.

Chemoreceptors

Detect chemical stimuli.