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Physiology > Homeostasis > Flashcards

Homeostasis Flashcards

1
Q

steady state VS chemical equilibrium

A

steady state - needs energy input; the amount of substance in compartments don’t change over time (still movement in/out)
-potential is a resting membrane potential
chemical equilibrium - doesn’t need energy input

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2
Q

mass balance for a system at steady state for metabolism

A

any substance taken in by the body is nearly equal to the amount leaving the body plus that removed by metabolism

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3
Q

basal metabolic rate

A

energy expenditure at rest; largest proportion of our daily energy usage (60% if sedentary)
-less than RMR b/c various forms of daily activity

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4
Q

resting metabolic rate

A

more than BMR b/c of various forms of daily activity

-higher in males, some hormones, if arctic, younger age

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5
Q

electrolyte concentration in extracellular and intracellular fluid

A

ECF - Na+
ICF - K+
maintained by Na+/K+ ATPases (3 Na+ out, 2 K+ in)

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6
Q

what is the major process used to maintain homeostasis

A

negative feedback

  • initiation of responses that counter deviations iof a controlled variable from a normal range
  • acts in combination with feedforward controls
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7
Q

feedforward controls

A

regulates body systems, particularly when a change with time is desirable

  • acts in combination with negative feedback
  • involves a command signal, but doesn’t directly affect the sensed compound
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8
Q

positive feedback

A

accelerates a process and can be unstable

-less common in nature than negative feedback, but still important

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9
Q

perturbation, gain, and correction

A

P - original change in homeostasis (ex: drop in blood pressure)
C - how much of the pertubation is repaired (pertubation - remaining error)
G - correction/remaining error (capacity of the system to restore a controlled variable to its set point after a pertubation)

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10
Q

negative and positive feedback due to blood loss

A

NFB: if less than 1 liter of blood lost; eventually returns to homeostasis
PFB: if more than 1 liter of blood lost; will eventually die

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11
Q

thermodynamic equilibrium in absence of solute electrochemical potential difference across membrane

A

driving force for solute transport

  • charged: if equal and opposite in direction across membrane, net force is zero
  • uncharged: if equal and opposite in direction, NOT a driving force
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12
Q

3D concept of a gradient

A

difference - solute concentration
direction - “up/against” or “down” gradient
driving force - potential energy acting on movement or change in physical and/or chemical properties of a defined space relative to comparable space

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13
Q

types of thermodynamic transport

A

passive transport - only down gradient
primary active transport - only up gradient, needs energy
secondary active transport - dependent on PAT to create a gradient (indirectly uses energy)
-sometimes travels up gradient, other times down gradient

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14
Q

types of molecular mechanisms

A

ion translocating pump (primary active)
channel (passive; mostly inorganic ions)
carriers (passive uniporters, secondary active symporters/cotransporters, or antiporders/cotransporter/exchangers)

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15
Q

ion-translocating ATPases

A

primary active transporters

  • Na/K (3 Na out, 2 K in)
  • H+
  • H/K
  • Ca++
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16
Q

kinetics of simple diffusion VS carrier-mediated diffusion

A

SD: straight line that doesn’t “saturate”
CM: hyperbolic curve that “saturates”

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17
Q

transfer stoicheometry

A

number of substrate molecules transported in one complete cycle of molecular events mediated by transport PRO, resulting in transfer of substrate across membrane

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18
Q

transfer electrogenicity

A

confers membrane potential difference (voltage) as well as substrate concentration difference as an additional driving force favoring/opposing transfer

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19
Q

acid extruder VS acid loader

A

Extruder: H+ leaves, base enters, increasing pH (acidosis: H+ is expelled in exchange for Na+)
Loaders: H+ enters, base exits, decreasing pH (alkalosis: HCO3 is expelled in exchange for Cl-)

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20
Q

what do core temperatures vary with?

A

time of day (highest between 3-6 PM, lowest between 3-6 AM)
stage of mestrual cycle (1 C higher if post-ovulatory)
level of activity/emotional stress
age (decreases as older)

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21
Q

radiation

A

transfers heat as electromagnetic waves between objects not in contact

  • rate of transfer proportional to temperature difference
  • humans emit infrared (~60%)
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22
Q

conduction

A

intermolecular thermal heat transfer between solid objects in direct contact
-minimal if wearing shoes/clothing

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23
Q

convection

A

loss/gain of heat by movement of air/water over the body

  • heat rises, carrying heat away from body
  • body immersed in water exchanges most heat by convection
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24
Q

evaporation

A

from skin and respriatory tract, carrying large amounts of heat generated by body (when air temp higher than body temp)

  • air circulation and hypotonic improves rate of evaporation
  • high humidity makes it less effective
25
Q

where is most body heat generated?

A

deep organs, by cellular metabolism

26
Q

what determines rate of heat loss

A

how rapidly heat is:
1. carried from core to skin
2. transferred from skin to surroundings
regulated by sympathetic nervous system (increased efferent will decrease blood flow to skin)

27
Q

passive/unregulated heat transfer

A

in steady state, rate of heat production by body core must be matched by flow of heat from core to the skin to environment

28
Q

continuous venous plexus

A

blood vessels beneath skin, very profuse

-supplied by skin capillaries and arteriovenous anastomosis

29
Q

how large is the increase in heat conductace from vasoconstricted to vasodilated

A

8-fold from changes in environmental temperatures

30
Q

sympathetic nervous system in regards to temperature changes

A

increased temp: inhibits supply to skin so vasodilation (improved heat loss)
decreased temp: activates supply so vasoconstricts (improved heat retention)

31
Q

acclimatization to hot weather

A

takes 1-6 weeks

-sweating capabilities increase from 1 L/hr to 2-3 L/hr

32
Q

sweat gland innervations

A

acetylcholine-secreting sympathetic nerve

  • primary PRO-free secretion formed by glandular portion
  • absorbtion in duct, leaving dilute, watery secretion
  • if rate of sweating is too high, will not reabsorb
33
Q

cold VS warmth receptor fibers in skin

A

10X more cold receptors than warm, b/c more sensitive to cold (to prevent hypothermia)
-both project to control center in hypothalamus

34
Q

cold VS warmth sensitive neurons in hypothalamjus

A

more heat-sensitive neurons

-integrates thermal information from skin and central temperature receptors

35
Q

effects of increased body temperature

A

skin vasodilation, sweating, decreased heat production

36
Q

effects of decreased body temperature

A

skin vasoconstriction, piloerection, thermogenesis (heat production), (nor)epinephrine excitation

37
Q

effects of heating preoptic area of hypothalamus

A

heat-sensitive neurons and receptors in hypothalamus are activated
-skin sweats profusely and skin vessels vasodilate

38
Q

components of negative feedback homeostatic reflex arc in thermoregulation

A

regulated variable - body temperature
stimulus - decreased body temperature
sensors - temperature-sensitive neurons in periphery and CNS
integrator - hypothalamic neurons that compare input to set point
effectors - sympathetic nerves regulating blood vessels in skin/sweat glands
-hypothalamic motor centers regulating shivering

39
Q

body heat balance during exercise (rate of heat production, core temperature, and skin temperature)

A

rate of heat production increases in proportion to exercise intensity, exceeding rate of heat dissipation

  • causes heat storage and rise in core temp due to delayed onset of sweating (provides error signal that sustains sweating response in exercise)
  • mean skin temperature is maintained nearly constant due to effect of sweating
  • -decreases slightly due to increased evaporative cooling of skin
40
Q

pyrogen effect

A

trigger increase in set point of hypothalamic temperature-regulating center

  • prostaglandin synthesis effect hypothalamus to increase set temperature
  • after pyrogens cleared, the setpoint is reduced
41
Q

effects of increasing the set point on body temperatrue

A

chills:

  • vasoconstriction
  • piloerection
  • epinephrine secretion
  • shivering
42
Q

heat exhaustion/collapse

A

failure in cardiovascular homeostasis in hot environment

  • decrease in circulating blood volume cauesd by skin vasodilation and sweating-induced decrease in central venous pressure
  • blood pools in limbs, causing weakness, confusion, ataxia, anxiety, vertigo, headache, nausea, and finally syncope
  • dilated pupils and profuse sweating
  • treat with rest in cool place with fluid/electrolyte replacement
  • core temperatures normal/mildly elevated
43
Q

heatstroke

A

elevated core temperature and heart rate + severe neurological disturbances (loss of consciousness/convulsions; normal blood pressure)

  • classical: environmental stress overwhelms impaired thermoregulatory system
  • exertional: high metabolic heat production
  • dry air: promotes rapid evaporative heat loss (survives for many hours)
  • humid air: elevates core temperature
  • treat with rapid lowering of core body temp (ice bath), hydration, airway maintenance
44
Q

malignant hyperthermia

A

massive increase in metabolic rate, O2 consumption, and lethal heat production in skeletal muscle

  • usually have mutations that disrupt Ca homeostasis in muscle (b/c mutated ryanodine receptor)
  • triggered by inhalation anesthetics and depolarizing muscle relaxants
  • treat with discontinuation of trigering agent, ryanodine receptor antagonists, cooling body
45
Q

hypothermia

A

heat production cannot increase enough to compensate for heat loss

  • drowsiness, slurred speech, bradycardia, hypoventilation
  • if severe: coma, hypotension, fatal cardiac arrythmias
46
Q

frostbite

A

freezing of surface areas

  • permanent necrotic damage if extensive ice crystals form in cells of skin and subcutaneous areas
  • gangrene follows thawing
  • sudden cold-induced vasodilation is final protective response near freezing temperatures (smooth muscle in vascular walls in paralyzed by cold)
47
Q

depolarization

A

reduction in charge separation, with less negative (more positive) membrane potential

48
Q

hyperpolarization

A

increase in charge separation, with more negative membrane potential

49
Q

capitance

A

amount of electrical energy separated for a given electrical potential
C = Q/V

50
Q

which is more, intracellular or extracellular for:

  • K+
  • Na+
  • Ca++
A

more K+ intracellular

more Na+, Ca++ extracellular

51
Q

diffusion potential

A

potential difference generated across a membrane when a charged solute diffuses down its concentration gradient (caused by diffusion of ions)

52
Q

equilibrium potential

A

concentration difference for an ion across a membrane, and membrane is permeable to that ion, a diffusion potential is created

53
Q

Nernst equation

A

equilibrium potential = (RT/zF)ln([X]2/[X]1)
=(58/z)log([X]2/[X]1)
-usually negative

54
Q

Goldman equation

A

resting membrane potential =
58log((P[K]o + P[Na]o)/(P[K]i + P[Na]i))
where P = permeability in physical terms
(alpha = Pna/Pk)

55
Q

effects of changing solute concentrations on equilibrium potential

A

increasing concentrations will increase from negative to near/above zero

56
Q

normal ratio of K:Na:Cl at resting potential and peak of action potential

A

rest: 1.0 : 0.04 : 0.45
AP: 1.0 : 20 : 0.45

57
Q

total body water and its proportions

A

60% of body weight; 42 L if 70 kg man

  • ICF: 2/3 of TBW = 40% body weight = 28 L
  • ECF: 1/3 of TBW = 20% body weight = 14 L
  • -interstitial fluid: 75% ECF = 11 L
  • -plasma: 25% ECF = 55% of blood volume = 3 L
58
Q

osmotic pressure

A

amount of pressure that would have to be applied to force water back into its original chamber
-water moves down its osmotic gradient until two chambers equilibriate, but can be forced back with proper applied pressure

59
Q

effect of extracellular osmolarity on intracellular volume and osmolarity

A

hypotonic: water enters ICF from ECF
isotonic: fluid stays in ECF
hypertonic: water enters ECF from ICF

equilibriate the osmolarity at expense of volume
osmolarity does NOT return to normal isotonic, but volume eventually does

Physiology (60 decks)

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