Spring Exam 2 Flashcards
what happens when temp is about 41C
Temp. regulation is impaired
heat stroke, brain lesions
what happens when temp is 36-41C
Temp regulation efficient in febrile disease and health and exercise
what happens when temp is 34-30C
Temp regulation is impaired
what happens when temp is 30-24C
Temp regulation is lost
what happens when temp is 27-25C
prone to cardiac arrhythmias
what is the normal range for temperature
36-38C
body temperature constancy (or body thermal mass) is a function of what?
heat production and heat lost to the surroundings
mechanisms by which we LOSE heat to the environment
- Radiation
- Convention
- Conduction
- Evaporation
movement of heat to one body that is in contact to another
conduction
heat loss from ____ is insensible or sensible to us
evaporation
example of what type of heat loss?
Breathing= instantly saturating breath with water.
evaporation
transfer of heat from warm body to the medium surrounding the body
convention
body radiates heat to any surrounding
radiations
radiant heat loss is ___% of heat loss
40%
factors that contribute to radiant heat loss
- body SA
- radiant characteristics of the environment
- skin/radient temp of environment
convention is ___% of heat loss
20%
why do infants lose heat pretty readily
bc they have a large SA relative to their mass
conduction is ___% of heat loss
40%
evaporation is __% of heat loss
20%
in order for evaporation to occur, what must be present?
heat (energy in the form of heat must be absorbed by water)
for each liter of water evaporated, how much heat is lost from our systems
580kcal
what part of the NS controls sweat glands?
cholinergic- sympathetic control
ACh release stimulates muscarinic cholinergic R–> stimulates sweating
describe the solution of sweat
hypo-osmotic (hypotonic) due to active reabsorption of ions
mechanisms by which we PRODUCE heat
- basal metabolic rate (~75kcal/hr)
- extreme muscular activity (15 fold increase)
- shivering (3-5 fold increases)
describe the non-shivering thermogenesis mechanism
endogenous uncoupling of the ETS in brown fat via thermogenin. (creates a pore in the ETS and allows constant flow of H+ do reduce EC gradient–> reduces ATP synthetic rate–> decreases AC–> increase catabolic enzymes= increase metabolic activity)
what is thermogenesis under the control of?
T3 and T4
thermogenin is restricted to what?
brown fat (in infants and lower animals)
how does vasoconstriction promote heat conservation?
impacts blood flow to the skin and shunts blood away from the skin surface to reduce radiant and conductive heat loss and to reduce the cooling of deep venous blood–> shunts blood through a path of lesser resistance
describe blood flow during vasoconstriction
warm blood leaving the system will enter the deeper systems and exchange between slightly warmer blood (returns to core through deeper veins)
mechanisms by which we CONSERVE heat (4)
- vasoconstriction
- drinking warm drinks
- adding layers
- turning up the heat
vasoconstriction is due to an increase in ___ tone (which results in)
- SNS
- increased SmM contractility = increased resistance to flow
increasing blood flow to skin promotes what
radiant and convective loss
promotes heat loss
vasodilation of vascular beds promotes what
conductive/convection heat loss
promotes heat loss
net heat production/loss is a function of what
hypothalamic temperature
**BUT heat production is constant (~20cal/sec at base)
Characteristics of thermoreceptors
- warm and cold receptors are always firing (at an overall slower rate)
- work in a limited temp range
- poorly adapting receptors (w/ graded response–> frequency modulation)
what is the “heat loss center”
POAH (preoptic anterior hypothalamus)
what is the “heat gain center”
posterior hypothalamus
what stimulates the POAH?
Major: local brain temp/ECF
Minor: cut. warm receptors and cut. cold receptors (inhibitory)
what stimulates the posterior hypothalamus?
Major: inhibition from POAH, cut. cold receptors
Minor: inhibition from cut. warm receptors
what are the effects of POAH stimulation?
vasodilation (increase blood flow–> increase radiant heat loss)
- sweating, panting, salivation
- *Heat loss!!
what are the effects of the posterior hypothalamus
vasoconstriction (heat conservation)
- shivering, piloerection (trap heat)
- *Heat gain!!
what acts upon thermoreceptors in the hypothalamus during a fever?
IL-1
what is IL-1
endogenous pyrogen that changes the set point in a dose dependent manner (fxn of amount of triggers)
what does IL-1 promote?
- ACTH release (cortisol increases)
- protein catabolism in muscle (increase gluconeogen. beta oxid., etc)
- redistribution of trace metals (promotes lactoferrin synthesis in neutrophils)
what does lactoferrin do?
chelates/binds free Fe2+, which inhibits bacterial growth due to reduced free [Fe2+] **Beneficial in fever!
what is going on during the onset of a fever
IL-1 levels rise, body shivers and vasoconstricts to generate heat to achieve a new set point (exicite post. hypo and inhibit POAH)
*exists for however long the pyrogens exist
what is going on when a fever breaks
stimulus for set point diminishes and you sweat/vasodilate to lose heat (excited POAH, inhibit post. hypo)
what is the point of a fever?
to create an environment that is less conductive to bacterial growth
How does ASA and NSAIDS help reduce a fever?
inhibits COX 1 and 2 which are used in the synthesis of PGE2 , which alters set points to produce a fever
what are the costs of a fever with each 1C?
13% increase in O2 consumption
- increase caloric intake
- increase fluid requirements
what are the overall effects of a fever
- increase muscle catabolism
- decrease mental acuity, delirium, stupor
- increase seizure possibility (esp. kids)
what is the primary determinant of cardiac cycle length?
diastole period (ventricles are refilling) ~2/3rd of time of cycle
what are the position of ALL the valves during diastole
AV and PV are closed, MV and TV are open
what do glycosides target?
myocardial contractility
what NS regulates myocardial contractility
ANS
what is preload
diastolic filling of ventricles
- greater degree of filling/V. stretch= greater force generated
what is afterload
aortic pressure
what are diuretics aimed at?
reducing preload
describe blood flow through the heart
RA–> TV–> RV–> PV–> pulmonary arteries–> lungs–> pulmonary veins–> LA –> MV–> LV–> AV –> Aorta–> body–> veins –> IVC–> RA
describe the pressure and resistance in each circulatory systesm
pulmonary- low pressure/low resistance (0-25mmHg)
systemic- high pressure/high resistance (80-120mmHg)
**pressure is on the arterial side!
why does we see a pulsatile flow with a venous laceration?
bc there is no oscillation of pressure in the venous system (only in arterial) and there is less overall pressure in venous system
____ is on the arterial side while ___ is on the venous side
pressure- arterial,
volume- venous (2/3rds)
describe the SNS innervation on the heart
B1, B2, and alpha1 Receptors– NE (and epi) NTs,
- innervates predominately ventricles
- mediates + inotropic (force) and chronotropic (increase rate of depolar.)
describe the PSNS innervation on the heart
Muscarinic (M2) receptors– ACh
- innervates predominately atria
- M2 is inhibitory and works to down regulate free cAMP to decrease HR
PSNS innervation is primarily through what nerve?
vagus (x)
what is an intrope?
an agent that alters the force or energy of muscular contractions. (-) inotropic= weaken the force of muscular contractions. (+) inotropic= increase the strength of muscular contraction
what are chronotropic effects?
change the heart rate by affecting the nerves controlling the heart
what is diastole?
relaxation of ventricles(filling)
what is systole?
onset of ventricular contraction
What does the p wave represent?
atrial depolarization (atrial contraction during diastole)
what does the QRS complex represent?
ventricular depolarization (contraction of ventricles)
what does the T wave represent?
ventricular repolarization (relaxation of ventricles)
what are the position of the valves during atrial depolarization (p-wave)?
AV and PV are closed, MV and TV are open
*S4
what are the position of the valves during ventricular repolarization (T wave)?
TV and MV are open
what causes S1 and S2
S1- MV/TV closing
S2- AV/PV closing
Why do we see spike in LA pressure during systole?
pressure regurgitation = pressure increase in LV so high that it can transduce through the AV and register as LA pressure increase