Thermoregulation Flashcards Preview

Neuro I > Thermoregulation > Flashcards

Flashcards in Thermoregulation Deck (66):
1

Normal body temperature
normal range

36.7 (98.06)
36.3-37.1 (lowest in the morning, higher as day goes on)

2

Themoregulation is a FEEDBACK system meaning

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

3

Variable maintained around a set point - stable. due to

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

4

FeedFORWARD system

information is used to PREVENT changes in the controlled variable

5

The vast majority of feedback systems in the human body are

negative feedback

6

thermoregulation is a _______ system.

feedback, although there are some feedforward aspects

7

Sensor=

Thermoreceptors

8

Thermoreceptor definition

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

9

Warm Sensitive Thermoreceptors

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

10

Discharge rate of warm sensitive thermoreceptors

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

11

Cold Sensitive Thermoreceptors

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

12

discharge rate of cold sensitive receptors

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)

13

Thermoreceptor locations

skin, viscera and brain
different locations tell the brain about different temperatures

14

Contoller =

hypothalamus

15

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

hormonal, autonomic, and behavioral changes

16

The part of the hypothalamus that responds to heat

anterior

17

the anterior hypothalamus

responds to heat
contributes to heat loss behaviors

18

The part of the thalamus that responds to cooling

posterior

19

the posterior hypothalamus

responds to cooling
contributes to heat production behaviors

20

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

core temperature

21

the carter we get from the core,

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

22

Body T changes with sleep

decreases
circadian influence
set point decrease

23

Body T changes with exercise

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

24

Temperature influenced by circadian rhythm

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

25

The ______ has a ______ for core temperature

hypothalamus
set point

26

Set point=

the desired value

27

______ determines the set point for core temperature

hypothalamus

28

Thermoreceptors are found in

brain, skin, gut

29

Thermoreceptors are found in

brain, skin, gut

30

Two kinds of information you need to know for thermoregulation

what my current body temp is
what is the temperature around me

31

Current body temp

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

32

Environmental body temp

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

33

Thermoreceptors in the core - where

brain and viscera

34

Cutaneous thermoreceptors - where

axons located in the sin

35

Cutaneous thermoreceptors - what

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

36

Visceral thermoreceptors - what

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

37

Central thermoreceptors - where

preoptic and superoptic regions of hypothalamus

38

central thermoreceptors - what

neuron cell bodies sensitive to changes in T
3X as many warm sensitive, they relay their information to other areas of the hypothalamus

39

Detection of CORE temp

preoptic and superoptic regions of hypothalamus and visceral thermoreceptors

40

detection of ENVIRONMENTAL temp

cutaneous thermoreceptors

41

Hypothalamus - thermoregulation

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

42

Two general categories of effectors

heat loss
heat production

43

Heat production mechanisms and ways of producing heat

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

44

Heat production - muscular activity

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

45

Heat production - non shivering thermogenesis

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

Heat production - brown adipose tissue

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

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

energy (heat) lost as water evaporate
1. insensible (respiratory)
2. sweating (controlled)

48

Heat loss - convection and conduction

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

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

49

Heat loss - convection and conduction

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

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

50

Heat loss - radiation

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

51

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

yes, put on a jacket

52

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

adjust both heat loss and heat production

53

Integrative responses to increased Core T

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

54

Heat loss - cutaneous blood

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

55

Heat loss - sweating (innervation)

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

56

Heat loss - sweating (sweat gland)

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

sweat starts out as a filtrate of plasma

57

Sweating process

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

sweating - low flow rate:

concentrated, little water, high Na

59

sweating - high flow rate:

lots of water, little Na, dilute

60

Sweating - along the duct reabsorb

Na, Cl and water
aldosterone can help reabsorb the Na

61

Integrative responses to Decreased Core temp

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

62

Fever - definition

a controlled increase in body temperature

63

fever - implication

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

64

Making of a fever

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

Hyper and hypothermia - definition

uncontrolled changes in body temperature

66

hyper and hypothermia - implications

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