Lecture One- Homeostasis Flashcards
Homeostasis and examples
regular range despite changes in the external environment
Examples: body temp, blood pressure,
Steady state
a condition that does not change with time
Is energy required to maintain equilibrium?
No
Is equilibrium a type of steady state?
Yes
Difference between equilibrium and steady state
When input is equal to output it is steady state…. requires some energy
In equilibrium there is NO net movement-two equal and opposite forces
Energy requirement for Equilibrium
None- NO ATP is required, no net flow
______ systems are needed to maintain equilibrium
Control systems
Sensor
Measuring variable trying to control-think a thermostat
Integrating center
compares info from sensor with a set point, generally the brain or spinal cord
effector (as a component of a control system)
way to cause a change i.e. glands, smooth muscle (it is the heater itself in the heating example)
Negative feedback
when the effector opposes the change
When room gets too cold, the heat turns on and opposes the change, this is what?
Negative feedback
Positive feedback
the effector increases the change given a defined ENDPOINT when the system resets
When smooth muscle of the urinary bladder reflex to tell smooth muscle to contract and causing bladder to empty-this is an example of what
Positive feedback
When glucose is too high, insulin converts to glycogen stores, this is an example of what process
Negative Feedback
why is temperature regulation necessary?
For optimal enzymatic and chemical reactions
Excessive heat (what is the temp and results)
43C/109F-Fatal as rate if reaction slows, cardiovascular collapse and CNS effects… Cells will die via apoptosis and denaturation of proteins
Excessive cold (what is the temp and results)
25 C/77F… Fatal as rate of rxn slows, cardiovascular collapse and CNS effects
Define the bodies core and the temperature it should be at
brain, thoracic/abdominal cavities should be around 37C
Define Fever and what happens regarding temp changes
increase in set point, when body temp goes below that you shiver
In fever, infection, trauma will cause what (stimulates what and what is the result)
macrophages–> increase in pyrogens (ex:IL-1) –> increase in prostaglandins (PGE2) in hypothalamus –>
increase set point
Why do inhibitory drugs work for fever reduction
they block prostaglandins
Hyperexia is defined as what
Fever which is > 41.5C
*HE did say would not ask temps on hypothermia.. so not sure
Hypothermia defined as (what temp is fatal?)
less than 25C is fatal
What are the effects of hypothermia (2)
CNS effects: apathy, confusion, unconsciousness
Cardiac arrhythmias can be fatal
Progression of heat exhaustion
profuse sweating –> fluid loss –> decrease blood volume –> decreased blood pressure –> faintaing
Is heat exhaustion life threatening
No- but needs to be treated
Signs/Symptoms of heat exhaustion:
cramps, nauseated, headache
Can skeletal muscle produce heat?
yes, via shivering and nermogenesis??? Moving skeletal muscle is not efficient so it produces heat (less than 50% efficient)
Heat stroke progression
GI Vasoconstriction –> ischemia –> endotoxins from intestines released into blood which will change the set point so high that body does not know to sweat
Why is drinking alcohol when cold bad?
Increases vasodilation of skin allowing heat to be lost
Is heat stroke life threatening?
Yes-mechanism unknown
Signs of heat stroke
increased body temp, no sweating, delirium, coma, seizure
Peripheral thermorecetors (what and location)
on the skin to monitor shell temp and to tell the temp of the environment
Where are central core receptors found
in the hypothalamus and abdominal cavity
Brown adipose tissue
Brown fat common in babies, found in some adults, more dense and good at generating heat-has lots of mitochondria in it
The integrating center of the control center is located where and how does it work
hypothalamus: it compares ambient temp to core to maintain set point
Proteins in brown adipose important for heat production
Uncoupling Proteins (UPC) which allows protons to flow down their gradient (against proton gradient) without producing energy and therefore produces lots of heat rather than energy
Effectors of the control system include what… (3)
Vascular smooth m.
Sweat glands
Skeletal muscle
When you have vasodilation you do what
release heat to environment to cool down-NOT when temp is too hot of course
most important method of heat dissipation
sweating
Vascular smooth muscle as an effector (where and what)
in arterioles
Can dilate or contract to direct blood flow to skin
Sweat glands as an effector (where and what)
dissipate heat
what a fever does to bodies set point
increases it-this is why you can feel cold even with a 100 degree F
Pyrogen
Fever causing hormone or agent
Sweat glands as an effector (where and what)
dissipate heat through evaporative loss-secrete sweat –> cooling effect
Skeletal muscle as an effector
shiver-works to regain heat
Metabolic uncoupling-burns energy (not making ATP, just dissipating energy as heat in mitochondria)
Why adults with brown fat may be skinnier
this fat does not store fat well
How you can die with heat stroke
When dehydrated you stop sweating and cannot regulate body temp-GI tract when heated up the bacterial pyrogens can circulate (this is just a theory)
Blood flow when cold?
decreased blood flow to skin
Nervous system activity in cold and what the result of this is
increased sympathetic NS activity –> skin vasoconstriction –> decreased blood flow –> decreased heat loss
How shivering is activated
The hypothalamus stimulates rythmic motor neuron activation which causes skeletal muscle contraction to generate heat
Response to cold
Behavioral adjustment: drink warm drinks, put on sweater ii. Decreased blood flow to skin: increase sympathetic NS activity à skin
vasoconstriction à decreased blood flow à decreased heat loss iii. Shivering: hypothalamus à rhythmic motor neuron activation à
skeletal muscle contraction to generate heat iv. Increase metabolic rate: increase epinephrine and thyroid hormone
release OR increase fat breakdown OR brown fat
1. Controlled by adrenal gland, increases metabolic uncoupling
