General principles Flashcards
Define: homeostasis
Maintaining nearly constant conditions in the internal environment (i.e. a steady state)
What is the difference between equilibrium and steady state?
Equilibrium does not require energetic input. Steady state does.
Additionally, in equilibrium, parameters are constant in time. In a steady state, they are nearly constant.
Define: Organ, Organ system
Organ: composed of 2 or more kinds of CT
System: A collection of organs that perform a general function
Define: Mass balance for a system at steady state
Any substance taken in is nearly equal to the amount leaving the body
Define: Basal Metabolic Rate
Energy expenditure at rest in kcal/hr/sq meter surface area
What accounts for most (20-30%) of basal metabolic rate?
Skeletal muscle
What are some factors that influence metabolic rate?
Age, gender, activity level, hormones, climate, nutrition status
Why is positive feedback rarely used?
It accelerates a process and can be unstable
Define: gain
The capacity of a system to restore a controlled variable to its set point after perturbation.
Mathematically, it is correction/remaining error
Give some examples of positive feedback in the body
Contractions in childbirth, blood clotting, estrogen effects on pituitary-hypothalamus before ovulation, action potential, bleeding out after excessive blood loss
What is the goal of negative feedback?
To bring a variable back to a set point, opposite the change that has occurred
Define: active transport
Moving a solute from a region of low electrochemical potential to a region of high potential. Up the gradient. Requires energy
Define: passive transport
Moving a solute down its electrochemical potential gradient (from high to low). Does not require energy
Define: thermodynamic equilibrium
When chemical and electric driving forces on a solute are equal and opposite in direction so the net driving force is zero
What type of transport is a pump?
Primary active
Give two examples of secondary active transport
Symporter carrier proteins and antiporter/exchanger carrier proteins
What type of transport is an ion channel?
Passive transport
Is simple diffusion mediated or unmediated?
Unmediated
Which is faster, facilitated diffusion through a carrier protein (uniporter) or through an ion channel?
Ion channel, by many orders of magnitude
Protein-mediated transport can be _____ at high concentrations of solute
Saturated
What is the difference between competitive and noncompetitive transport inhibition?
Competitive inhibition can be overcome by an increase in solute concentration. Noncompetitive can not.
Define: electrogenic
When the charge transfer from one side of the membrane to the other is unequal, producing a net charge (i.e. Na+/K+ antiporter produces a net positive charge outside of the cell)
Define: endotherm
An animal that generates its own body heat. Ex. a human.
Define: homeotherm
An animal that maintains a core body temperature in a narrow range. Ex. a human.
Does thermoregulation have a high or a low gain?
High gain. It is a very powerful system
Define: radiation
Transfer of heat as electromagnetic waves between objects that are not in contact
Define: conduction
Intermolecular heat transfer between solid objects in direct contact
Define: convection
Loss or gain of heat by movement of air or water over the body
Define: evaporation
Loss of heat due to transformation of water from liquid to gas on the skin or in the respiratory tract
How does a normal person at rest in a normal environment lose most of their heat?
Radiation
How does an exercising person in a normal environment lose most of their heat?
Evaporation- sweating
In a hot environment, how does a normal person let off heat?
Evaporation- sweating. Radiation and convection do not apply
The skin has more (cold/warm) receptors
Cold, by about 10-fold
The hypothalamus has more (cold/warm) receptors
Warm
Is thermoregulation a positive or negative feedback response?
Negative
What happens when a pyrogen is present in the body?
The hypothalamus raises the set point of body temperature, creating a fever state. Consequently, the hypothalamus thinks the body is too cold and a person gets chills with vasoconstriction, shivering, piloerection and epinephrine secretion to attempt to warm up the body.
Define: heat exhaustion
A failure of cardiovascular homeostasis to dissipate heat in a hot environment. Decreased blood volume due to vasodilation and sweating can lead to syncope
Define: heat stroke
Elevated core temperature in conjunction with severe neuro distrubances (loss of consciousness, convulsions). Accelerated by exercise and humidity
Define: hypothermia
Heat loss is greater than heat production (i.e. immersal in cold water). Drowsiness, slow speech, bradycardia, hypoventilation and decreased metabolic rate
Define: frostbite
Exposure to low temperatures causes freezing of surface areas and necrosis. Vasoconstriction with sudden-cold induced vasodilation as a protective response.
What gives rise to a membrane potential?
A separation of charges (a gradient)
What does the Nernst equation tell you?
The equilibrium potential for an ion across a membrane that is only permeable to that one ion
What does the Goldman equation tell you?
Membrane potential for a membrane permeable to more than one ion
Positive current is defined as the net flow of (positive/negative) ions (into/out of) a cell
Positive ions into a cell
Total body water is what percentage of body weight?
60%
Intracellular fluid is what percentage of total body water? Of total body weight?
ICF is 67% of total body water. 40% of total body weight. For a 70 kg standardized patient, ICF volume would be 28L
Extracellular fluid is what percentage of total body water? Of total body weight?
ECF is 33% of total body water and thus 20% of total body weight. For a 70 kg standardized patient, ICF volume would be 14L
Define: osmolality
The sum total of all solute concentrations in a compartment
What is the normal osmolality of plasma?
300 mOsm/L
Define: osmotic pressure
The amount of pressure needed to force water back into its original chamber once it has moved down its concentration gradient into a chamber of higher osmolality
What two ion transporters are activated by cell shrinkage due to an increase in extracellular osmolality?
A H+/Na+ antiporter and a HCO3-/CL- antiporter. Outside of the cell, H+ and HCO3- form H2O and CO2 which enter the cell to increase volume and lower osmolality to normal
What three mediated transporter proteins are activated by cell swelling due to an decrease in extracellular osmolality?
K+ channels, Cl- channels, and a K+/Cl- cotransporter out of the cell. These lower the cell osmolality and thus water moves out of the cell
Edema is a shift in fluid from which compartment to which other compartment?
Intravascular to interstitial
