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Neuro I > Thermoregulation > Flashcards

Thermoregulation Flashcards

1
Q

Normal body temperature

normal range

A
  1. 7 (98.06)

36. 3-37.1 (lowest in the morning, higher as day goes on)

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2
Q

Themoregulation is a FEEDBACK system meaning

A

information is fed back to the controller to report changes in the controlled variable

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3
Q

Variable maintained around a set point - stable. due to

A

negative feedback, which brings it back to set point regardless of the direction it changes

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4
Q

FeedFORWARD system

A

information is used to PREVENT changes in the controlled variable

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5
Q

The vast majority of feedback systems in the human body are

A

negative feedback

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6
Q

thermoregulation is a _______ system.

A

feedback, although there are some feedforward aspects

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7
Q

Sensor=

A

Thermoreceptors

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8
Q

Thermoreceptor definition

A

thermoreceptors are neurons which change their firing rate in response to changes in local temperature
may be warm or cold sensitive
presumed to be bare nerve endings

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9
Q

Warm Sensitive Thermoreceptors

A

4 channels identified
TRP-V1-4
sensitive over different ranges
V=vanilloid=capsaicin (hot peppers)

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10
Q

Discharge rate of warm sensitive thermoreceptors

A

low when temperatures are low (out of range)
increase with increasing temperature
at high enough levels, it decreases again, maybe indicating we are damaging them and compromising function

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11
Q

Cold Sensitive Thermoreceptors

A

Two receptors TRPM8, TRPA2
also activated by menthol
channels open as temperature decreases
allows Na or Ca influx

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12
Q

discharge rate of cold sensitive receptors

A

high when temperature is low
decrease as temperature increases
if T gets high enough , you may have a second peak (when something is VERY hot)

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13
Q

Thermoreceptor locations

A

skin, viscera and brain

different locations tell the brain about different temperatures

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14
Q

Contoller =

A

hypothalamus

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15
Q

The hypothalamus has the connections to control __________________ that are part of thermoregulation

A

hormonal, autonomic, and behavioral changes

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16
Q

The part of the hypothalamus that responds to heat

A

anterior

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17
Q

the anterior hypothalamus

A

responds to heat

contributes to heat loss behaviors

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18
Q

The part of the thalamus that responds to cooling

A

posterior

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19
Q

the posterior hypothalamus

A

responds to cooling

contributes to heat production behaviors

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20
Q

The variable that we want to keep stable over a wide range of environmental temperatures

A

core temperature

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21
Q

the carter we get from the core,

A

the more variance we get in body temperatures - these things (hands,feet) are not controlled by the brain, they are just along for the ride

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22
Q

Body T changes with sleep

A

decreases
circadian influence
set point decrease

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23
Q

Body T changes with exercise

A

increases (as high as 40)
increased heat production
set point increase

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24
Q

Temperature influenced by circadian rhythm

A

varies 1-2 degrees over a 24 hour period, lowest in the morning around 6 AM

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25
Q

The ______ has a ______ for core temperature

A

hypothalamus

set point

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26
Q

Set point=

A

the desired value

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27
Q

______ determines the set point for core temperature

A

hypothalamus

28
Q

Thermoreceptors are found in

A

brain, skin, gut

29
Q

Thermoreceptors are found in

A

brain, skin, gut

30
Q

Two kinds of information you need to know for thermoregulation

A

what my current body temp is

what is the temperature around me

31
Q

Current body temp

A

T affects enzyme activity (Q10)
will change cellular function
for better or worse, usu worse

32
Q

Environmental body temp

A

is a threat to body temp, since I am always generating heat, my problem is usu getting rid of heat

33
Q

Thermoreceptors in the core - where

A

brain and viscera

34
Q

Cutaneous thermoreceptors - where

A

axons located in the sin

35
Q

Cutaneous thermoreceptors - what

A

TELL US ABOUT ENVIRONMENTAL CONDITIONS
often bimodal (T and touch)
may be warm or cold (10X as many cold sensitive)

36
Q

Visceral thermoreceptors - what

A

sense core temperature

sense threats to maintenance (food ingested may change body T - tell hypothalamus about these threats) feed forward

37
Q

Central thermoreceptors - where

A

preoptic and superoptic regions of hypothalamus

38
Q

central thermoreceptors - what

A

neuron cell bodies sensitive to changes in T

3X as many warm sensitive, they relay their information to other areas of the hypothalamus

39
Q

Detection of CORE temp

A

preoptic and superoptic regions of hypothalamus and visceral thermoreceptors

40
Q

detection of ENVIRONMENTAL temp

A

cutaneous thermoreceptors

41
Q

Hypothalamus - thermoregulation

A

integration of afferent
determination of set point
compare set point to core T - if different , generate response (feedback)
respond to environment (feed forward)

42
Q

Two general categories of effectors

A

heat loss

heat production

43
Q

Heat production mechanisms and ways of producing heat

A

ANS - sympathetic system
Hormonal - thyroxin, epi, norepi
Muscular activity - shivering, jumping up and down
Non shivering thermogenesis (non muscular)

44
Q

Heat production - muscular activity

A

Shivering= dorsomedial posterior hypothalamus (increase motorneuron excitation)
increase voluntary activity = cortex (jumping, running)

45
Q

Heat production - non shivering thermogenesis

A

Hormonal influence strong = thyroxin increases metabolic rate (heat production), stimulus for TRH release is cold; epinephrine

Increae food intake= increase metabolism

Brown adipose tissue

46
Q

Heat production - brown adipose tissue

A

low efficiency hydrolysis of ATP (=lots of heat production)
sympathetic innervation of brown fat, circulating dpi
importance in human = strong in infants, recent evidence shows existence in adults, but located more in white fat (requires exposure to cole and sympathetic activation)

47
Q

Heat loss - evaporative heat loss (EHL), two kinds

A

energy (heat) lost as water evaporate

  1. insensible (respiratory)
  2. sweating (controlled)
48
Q

Heat loss - convection and conduction

A

convection = movement of molecules away from contact (air heating and rising)

conduction= transfer of heat between objects in physical contact with one another

49
Q

Heat loss - convection and conduction

A

convection = movement of molecules away from contact (air heating and rising)

conduction= transfer of heat between objects in physical contact with one another

50
Q

Heat loss - radiation

A

infrared radiation transferring heat between 2 objects not in physical contact (you and the walls)

51
Q

Heat loss - can we control these forms (convection, conduction, and radiation) of heat loss

A

yes, put on a jacket

52
Q

In order to respond to changes in core temperature, the hypothalamus will

A

adjust both heat loss and heat production

53
Q

Integrative responses to increased Core T

A

Tb> Tsetpoint
decrease heat production (apathy inertia, anorexia)
increase heat loss (blood to skin, EHL - sweat, insensible heat loss - pant)

54
Q

Heat loss - cutaneous blood

A

how much blood is sent to the skin determines how much heat moves from blood to external environment

55
Q

Heat loss - sweating (innervation)

A

sympathetic CHOLINERGIC innervation

Ach is NT, binding to a muscarinic receptor (anatomically sympathetic) - want to vasodilate so ACH is the NT of choice

56
Q

Heat loss - sweating (sweat gland)

A

lots of blood vessels nearby
coiled region by vessels
duct leading to skin

sweat starts out as a filtrate of plasma

57
Q

Sweating process

A

plasma and ions (no proteins) are filtered from blood vessel to sweat glands –> primary secretion is high in WATER, Na–> water, Na are reabsorbed (taken back to the blood) in the duct of the sweat gland–>sweat is released to environment

58
Q

sweating - low flow rate:

A

concentrated, little water, high Na

59
Q

sweating - high flow rate:

A

lots of water, little Na, dilute

60
Q

Sweating - along the duct reabsorb

A

Na, Cl and water

aldosterone can help reabsorb the Na

61
Q

Integrative responses to Decreased Core temp

A

Tsetpoint> Tb
increase heat production (shivering, non shivering thermogenesis)
decrease heat loss (blood away from skin, decrease evaporative heat loss)

62
Q

Fever - definition

A

a controlled increase in body temperature

63
Q

fever - implication

A

set point increase: body T is only doing what hypothalamus directs it to do

64
Q

Making of a fever

A

Step 1 - the bug (secretion of endotoxins), immune cells (release cytokines) lead to production of PGE2 –> increase hypothalamic set point for T. TBTSETPOINT

Step 5 - increase heat loss, decrease heat production

Step 6 - TB=TSETPOINT, real comfort

65
Q

Hyper and hypothermia - definition

A

uncontrolled changes in body temperature

66
Q

hyper and hypothermia - implications

A

set point remains normal
environmental stresses exceed body;s ability to regulate temperature
at extremes - hypothalmic regulation may be lost

Neuro I (30 decks)

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