Physiology Second Stage Lecture 1

Physiology Overview

• Physiology studies organ functions and the physical and chemical processes involved in life.
• Homeostasis is the maintenance of a stable internal environment despite external changes, exemplified by body temperature and blood glucose regulation.

Homeostatic Mechanisms

• Negative Feedback: Most common mechanism; reduces or stops the original stimulus to restore balance.
• Positive Feedback: Enhances the original stimulus, pushing the variable further away from its set point.

Components of Homeostatic Systems

• Sensor: Detects changes in internal or external environment.
• Control Center: Processes information from the sensor and sends out responses.
• Effector: Executes responses that restore homeostasis.

Body Temperature Regulation

• In hyperthermia, heat receptors in the skin detect the increase in temperature.
• The hypothalamus acts as the control center, triggering perspiration and increased blood flow to the skin to cool the body.

Levels of Organization in the Body

• Cell: Basic structural and functional unit of life.
• Tissue: Group of similar cells; four primary types:
  • Muscle: Skeletal, smooth, cardiac.
  • Nervous: Neurons and support cells.
  • Epithelial: Squamous, columnar, cuboidal.
  • Connective: Various forms including cartilage and bone.
• Organ: Composed of two or more tissue types working together to perform specific functions.

Membrane Proteins

• Integral Proteins: Penetrate the phospholipid bilayer fully or partially.
• Peripheral Proteins: Attached to the inner or outer surfaces of the membrane.

Functions of Membrane Proteins

• Act as transport proteins, enzymes, receptors, and cell adhesion molecules (CAMs).
• Glycocalyx is a carbohydrate coat that serves various functions including repelling bacteria and acting as hormone receptors.

Functions of Cell Membrane

• Protective barrier, selective permeability, absorption, excretion, gas exchange, and maintaining cell shape and size.

Cytoplasm and Organelles

• Cytoplasm: Jelly-like substance where organelles are suspended; site for chemical reactions.
• Organelles: Specialized structures within cells, categorized as membrane-bound or non-membrane-bound.

Organelles' Structure & Function

• Endoplasmic Reticulum (ER): Network of membranes;
  • Rough ER synthesizes proteins with ribosomes.
  • Smooth ER synthesizes non-protein substances and stores calcium.
• Ribosomes: Protein/RNA structures; essential for protein synthesis.
• Golgi Complex: Processes and packages molecules; produces secretory vesicles.
• Mitochondria: Energy producers; convert food molecules into ATP.
• Lysosomes: Digest foreign molecules and damaged organelles.

Ribosomes

• Composed of two subunits; critical for synthesizing enzymatic, hormonal, and lysosomal proteins.
• Free ribosomes synthesize proteins for cellular use.

Mitochondria Details

• Double-membranous organelle responsible for energy production via ATP synthesis.
• Inner membrane features invaginations (cristae) to increase surface area.

Other Cytoplasmic Organelles

• Peroxisomes: Detoxify harmful substances; involved in fatty acid metabolism.
• Centrosome & Centrioles: Organize spindle fibers for chromosome movement during mitosis.
• Vacuoles: Store and release various substances.
• Cilia & Flagella: Aid in movement across cell surfaces.

Cytoskeleton

• Composed of microtubules, intermediate filaments, and microfilaments; provides cell shape, support, and facilitates movement.

Nucleus Structure and Function

• Nuclear Envelope: Double membrane with pores regulating material exchange between nucleus and cytoplasm.
• Nucleoplasm: Jelly-like matrix supporting nuclear contents.
• Nucleoli: Sites for ribosome production within the nucleus.
• Chromatin: Thread-like material forming chromosomes, carrying genetic information.

This summary encapsulates key concepts from physiology, highlighting important functions, structures, and processes fundamental to understanding living organisms.

Explore the foundational concepts of medical physiology in this quiz covering the general and cellular basis of body functions. Understand key terms such as homeostasis, and how internal environments maintain stability despite external changes. This quiz is suitable for students in advanced physiology courses.