Physiology Flashcards
What is physiology?
Understanding the mechanisms of living things and how things work in the body
Homeostasis
Everything kept in balance, uses dynamic equilibrium
How do signals travel around body to maintain homeostasis? (2)
- Nervous system
- Hormonal (endocrine) system
Essential components of negative feedback loop (5)
- Controlled variable
- Receptors (sensors)
- Processor (compare to set point)
- Set point
- Effector mechanisms (to restabilize)
Controlled variable
- Starting problem (independent variable… sorta)
- ex. core body temperature, blood pressure, blood glucose, osmolarity of plasma, blood oxygen levels
Effector mechanism
Changes to restore homeostasis
- ex. heart rate, urine concentration, respiratory rate
What can and cannot diffuse across cell membrane?
- Yes: small gases along concentration gradient, water
- No: sugars, proteins, ions
What causes liquids to diffuse across membrane (Brownian motion) (3)
- Thermal motion and collisions
- Down concentration gradient
- Inversely related to size
- Only small distances
Pores
always open, non selective, any small ion
Channel definition and the 2 types of channels
selective to 1 type of ion
- Non-gated: always open
- Gated: open only when stimulated by voltage, ligand (chemical signal), or sec (second messenger)
Carriers
- Facilitated passive transport (relying on 1 concentration gradient
- Specific binding
- Confirmational change
- Releases 1 ion at a time
Types: 1 ion in, 2 ions in, 1 out/1in
Pumps
Active transport w/ATP
Electrochemical gradient purpose
Allows passive transport. Important for the passage of solutes which impacts cell function
Osmosis
How water moves across body compartments
- ECF pressure maintained by homeostatic mechanisms. ICF changes depending on ECF
Molarity
grams of solute/1L
Osmol
number of particles
Osmolarity
measure of solvent activity (Number of osmoles/ unit volume of solution)
- higher osmolarity, lower solvent activity
Osmosis
Movement of water from higher solvent activity to lower solvent activity across semipermeable membrane
Osmotic pressure
Exact pressure required to stop osmosis
Effective osmotic pressure cause
- Depends on properties of membrane separating compartments
- O=1, not permeable
- O=0, freely permeable
- O=0-1, varying permeability
Tonicity
Effect of bathing solution on cell volume
Isotonic
No net movement
Hypertonic
Net outwards, shrinking
Hypotonic
Net movement inwards, lysis
Starling’s forces
Determine how much water moves in and out of capillaries (based on oncotic (in) pressure and constant hydrostatic pressure (out)
How much of the animals body is water?
60%
How much water is ICF
40%
How much water is ECF
20%
Gibbs-Donnan Effect
- ICF negative charge drawing in positive ions and water
- Cells combat this using 3NA/2K pump
