Intro to Physiology Flashcards
What is the internal environment?
The carefully regulated fluid environment that cells need in order to function - must remain stable despite changes in external environment
How is the internal environment maintained?
Homeostasis - active process requiring energy
What is part of the external environment?
Digestive system, respiratory system, urinary system
What makes up the internal environment and why?
Cardiovascular system, interstitial fluid, intracellular fluid - does not directly interact with external environment
What is the capillary endothelium?
Between blood and interstitial fluid
What is the plasma membrane?
Between interstitial fluid and intracellular fluid
What makes up the extracellular fluid?
Blood and interstitial fluid
What is interstitial fluid?
Any fluid not in blood vessels or cells
What is osmolality?
Total concentration of all particles that are free in a solution - vital parameter that must be controlled
What is the body’s osmolality?
290 mOsm (milliosmoles per kg of water) in all compartments to avoid movement of water by osmosis
What happens if osmolality is disrupted?
Cells may swell/burst or shrink
How are ions distributed between ICF and ECF?
Na+ Higher in ECF
K+ Lower in ECF
Cl- Higher in ECF
Ca2+ Higher in ECF
What does amphipathic mean?
Has both hydrophobic and hydrophilic parts
What are the properties of a hydrophobic head?
Polar
Interacts with water
Sits on outside of membrane
What are the properties of a hydrophilic tail?
Non-polar
Interacts poorly with water
Sits on inside of membrane
How is a phospholipid structured?
Hydrophilic phosphate head
Hydrophobic lipid tails
(Ethanolamine, Phosphate, Glycerol, Fatty acids)
What other molecules make up the cell membrane?
Cholesterol
Proteins
What is the selective permeability of cell membranes?
Impermeable to: Large molecules e.g. proteins nucleic acids, charged water soluble substances e.g. ions
Permeable to: Hydrophobic molecules e.g. O2, CO2, steroid hormones
Partially permeable to: uncharged, polar molecules e.g. H2O, urea, glucose
What is the function of membrane proteins?
Provide specific channels and carriers - allows polar molecules (ions, sugars, AA, water) to pass through, avoiding hydrophobic core of bilayer
What is homeostasis?
Maintains the steady state of vital parameters
What are the body’s vital parameters?
Oxygen in blood plasma
ATP in ECF
Volume of plasma and ICF (affects BP)
Ion concentrations
Arterial BP
Core body temperature
Glucose
What is an example of an external change?
Temperature change
What is an example of an internal change?
Running - muscles need more oxygen
What are the basic components of a negative feedback loop?
1) Steady state disrupted
2) Receptors sense vital parameter
3) Control centre compares input against a set point (hypothalamus, brainstem)
4) Output signal from control centre to effector (via neural mechanisms - ANS, or via endocrine system - hormones)
5) Effector enables a change to return the vital parameter (sweat glands, skeletal muscle, cardiac muscle)
