Seeing the World: Perspectives from Vision Science

21 Pages • Complete Study Notes • Year: Pre-2021

• LEVELS OF ORGANISATION: chemical  cellular  tissue  organ  body system  organism • Cellular:  Specific combinations, arrangements and binding of molecules form cells o Cells are the fundamental structural and functional units of a living organism 
 o Exist alone or as a group in a multicellular organism 
 • Basic Function of Cells: Nutrient and oxygen  energy (eliminate waste/by products) • Synthesise proteins and other components for cells structure/growth/function • Specialised cell functions in multicellular organisms • Cell Diversity: Morphology (diff shape, size, structure and bio chemistry) & Specialisation Cell to Cell Adhesions • Plasma membrane of cells not only act as the outer boundary – adhesion • Cell Adhesion Molecules: o Proteins that protrude from outer membrane surface to form loops and hooks o Binds to other cells or extracellular matrix • Extracellular Matrix (ECM) o Molecules secreted by cells – meshwork of proteins embedded in interstitial fluid o Structural and biochemical support • Specialised cell junctions Desmosomes (adhering) Tight Junctions (impermeable) Gap Junctions (communicating) • Attach two non-touching cells • Strongest • Plaque located in the inner surface, filaments link adjacent cells • Adjacent cells bind at point of direct contact • Seal off passageway between cells = prevents movements of materials between cells • Adjacent cells connected by small connecting tunnels (connexion): hollow tube like structure that extends through the plasma membrane • Communicating Junctions – molecules, ions & electrical impulses to directly pass through regulated gate between channels Tissue • Cells combine to form tissue • Various types: muscle, nervous, epithelial, connective • Muscle Tissues: contracting  tension  movement o Skeletal: Skeleton o Smooth: Tubes and Organs e.g. digestive track o Cardiac: Height • Nervous Tissues: initiating and transmitting electrical impulses (brain body) o Brain, spinal chord, nerves and special sense organs • Epithelial Tissue: exchanging materials between cell and environment o Epithelial sheets – tightly joined cells, lining covers body o Secretory glands: specialised epithelial tissue (secretion) • Connective Tissues: connecting, supporting and anchoring various body parts o E.g. blood Organs • Two or more types of primary tissue organised to perform a particular function(s) • Groups of organs  body systems • Body is made of 11  Homeostasis • Maintenance of a relatively stable internal environment o Establish optimal condition, balanced and steady state • Functions performed by each body system  contribute to homeostasis o Detect deviations from normal internal environ.  integrate information & make adjustments • Control systems: 1. Intrinsically controlled: built into or inherent in an organ 2. Extrinsically controlled: initiated outside an organ to alter organ activity • Negative Feedback Control: change stimulates a response that seeks to restore to normal by moving the factor in the opposite direction of its initial change • Positive Feed Control: change stimulates a response that seeks to restore normal by enhancing or amplifying the change – same direction of initial change • Feed Forward Control: anticipate and prevent change

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