13) Introduction to Physiology

• Physiology:

  • Study of how thing cells, tissues, organs and systems function
• Cells: Basic structural units of living organisms

  Fertilised egg (single cell)

   - Cell division  (Multiplication)

   - Cell differentiation (Specialisation)
• Organs work as a system to perform a complex function

  ⤷ systems do not work by themselves

  ⟶ EG: Blood pressure is controlled by the circulatory system, urinary, nervous and endocrine system
• Structure of heart chambers

   1) an electrical signal initiated by the sinoatrial (SA) node, acting as a pacemaker

  2) This signal spreads across the atria via cell-cell communication (Gap junctions between myocytes)

  3) Nerve fibres coordinate contraction of ventricular myocardium

  ⤷ The pumping of blood is dependant on the structure and function of the heart!
• Movement along gradients: 

   - Matter and energy flow down gradients

  EG: Blood circulation, respiratory airflow, urine, nerve and muscles

  ⤷ Types of gradients include chemical, electrical, pressure, temp, etc
• When substances move down a gradient they go from a high to low concentration

  when substances move up a gradient they go from low to high - Going against a concentration gradient requires additional energy (often ATP)
• 1. Charged particles such as Na+ move down electrochemical gradients
  2. Outside the cell there are a high conc of Na+ and low conc of Na+ inside the cell 

  ⤷ As a result the outside has an overall positive charged and inside has a negative charge 
• Homeostasis

  ⟶ Bodies ability to detect change and reverse it to maintain stable internal conditions 
• Blood glucose levels

   - Glucose levels vary throughout the day, but overall homeostatic blood glucose lvl are maintained
• Dynamic consistency

  ⤷  cellular processes and functions as an organism adapts and responds to its environment over time (often predictable) 
• • Negative feedback: 

  ⤷  Keeps variables close to their initial level 

  • Positive feedback: 

  ⤷ When a stimulus is detected it enhances the change further than normal range 

  eg: Blood clotting