Exam #2_Semester 2 Flashcards
core of body
- includes head, thorax, and abdomen
- is the regulated variable
- area of the core can change (very beneficial for temp maintenance)
- maintained at 37 C
location of accurate body temp and why
tympanic membrane / infrared sensing on temporal lobe
- b/c shares arterial blood supply with hypothalamus and HT is center of regulatory activities that aim to maintain core temp
conduction
transfer of heat from hot object (body) to cooler object though direct contact (accounts of 40% of heat loss)
convection
heat loss from skin to air; due to air moment across skin
- air closest to skin is warmed through convection and then replaced by cooler air
sweat - hypo-osmotic (hypotonic) secretion from sweat glands
Sweat is hypo-osmotic (derived from ECF – 295 mmol/l; sweat is about half = 150 mmol/l))
We lose more water per volume than solute (fluid loss from EC compartment is main issue); however solute (electrolyte) loss is also occurring
mechanisms by which body produces heat
basal metabolic rate (75 kcal/hr)
extreme muscular activity (15-fold inc over basal rate) - not sustainable / energentically costly
shivering (3-5-fold inc over basal rate) - involuntary, can maintain longer
non-shivering thermogenesis
means of generating heat metabolically without shivering
involves uncoupling of the ETC and ATPsynthase activity in brown fat
Thermogenin acts as an inner mitochondrial membrane proton channel that serves to reduce the proton gradient across this membrane.
Cellular adenylate charge drops as a result and an increase in cellular metabolic activity follows producing heat.
brown fat
unique adipose tissue that expresses uncoupling protein (thermogenin) under control of thyroid hormone
thermoreceptors
have both cold and warm receptors in skin; increase or decrease firing frequency depending on skin temp
- poorly adapting receptors - provide constant input
preoptic anterior hypothalamus (POAH)
heat loss center
posterior hypothalamus
heat gain center
cost of a fever
each 1 degree C elevation:
- 13% inc. in O2 consumption
- inc. caloric requirement
- inc. fluid requirment
factors effecting cardiac output
Cardiac factors:
- HR (beats/min)
- contractility: targeted by inotropic agents
Coupling factors
- preload and afterload
preload
diastolic filling of ventricles (inc. beneficial up to a point)
treatment used to target preload
diuretics
treatment used to target contractility of myocardium
positive inotropic agents
afterload
aortic pressure (inc. detrimental to cardiac output)
compliance
change in volume for a given change in pressure (veins are more compliant)
chronotropic
effect rate of the heartbeat
inotropic
effect the force of the heartbeat (can be positive or negative)
SNS receptors
adrenergic receptors mediating response of Norepi
act though g proteins (2nd messenger systems)
beta 1: Gs, inc. cAMP, PKA, phosphorylation
- inc. cardiac contractility
- dec. SM contractility of vasculature
alpha 1: Gq, inc. IP3
- dec. cardiac contractility
- inc. SM contractility of vasculature
cardiac cycle
Cardiac cycle is composed of the electrical, mechanical, pressure & volume events that occur in the heart during one contraction (includes contractile and relaxation events)
Electrical→contractile→pressure→volume
systole
onset and duration of ventricular contraction (contractile period)
- ends with closure of aortic valve
diastole
relaxation of the ventricular myocardium (atrial contraction), longer duration than systole but variable
- begins with end of systole and ends at onset of next systolic period
lactoferrin
protein synthesized in response to IL-1
- binds free iron (Fe2+)
- bacterial growth is dependent on availability of free Fe and, thus, is inhibited
pressure regurgitation
pressure increase in LV so high that it can transduce through the A-V valve (mitral) and register as LA pressure increase (even higher than when atria contract!)
- ends with aortic valve opens