lecture 14-temperature regulation Flashcards Preview

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Flashcards in lecture 14-temperature regulation Deck (47):
1

what is malignant hyperthermia triggered by

anesthetics

2

what main factors determine rate of heat loss

how rapidly heat can be conducted from body core to skin and how rapidly heat can be transferred form skin to surroundings

3

what is the continuous venous plexus in subQ supplied by

inflow of blood from capillaries from dermis

4

how is heat conduction to skin controlled

by the degree of vasoconstriction of arterioles and the arteriovenous anastomoses that supply blood to the venous plexus of the skin

5

what is vasoconstriction controlled mostly by

almost entirely by sympathetic system in responses to core temperature and environmental temperature

6

describe radiation

loss of heat in the form of IR heat rays. it is radiated by all objects not at absolute zero.

7

define conduction

kinetic energy of the molecules of the skin is transferred to the air if the air is colder than the skin

8

define convection

removal of heat from the body by convection air currents

9

how any calories of heat are lost for each gram of water that evaporates from the body surface

0.58 calories of heat

10

define insensible perspiration

occurs at a rate of 600-700 ml/day and causes a continual heat loss at a rate of 16-19 calories/day

11

what does the amount of heat transferred by radiation depend on

temperature difference and ability of object to absorb energy

12

define evaporation

heat is dissipated by the use of thermal energy to cause a change from fluid to gas

13

what are stimulating factors for sweating

stimulation of anterior hypothalamus-pre-optic area in the brain electrically or by excess heat. cholinergic sympathetic nerve fibers (muscarinic) and circulating epinephrine and norepinephrine)

14

what are the principal areas of the brain that affect body temperature

anterior hypothalamic pre-optic area and pre-optic area

15

what type of neurons does the anterior pre-optic area contain

both heat-sensitive and cold-sensitive neurons

16

describe heat sensitive neurons of the anterior pre-optic area

increase firing rate 2-10X in response to a 10 degree celcius increase in body temperature

17

describe cold-sensitive neurons in the anterior pre-optic area

increase firing rate when temperature falls

18

what does heating the pre-optic area cause

dilation of skin blood vessels over the entire body, profuse sweating over the entire body, and inhibition of excess heat production

19

T/F: vasodilation increases body heat

false; it decreases it

20

how does vasodilation of skin blood vessels reduce body heat

by inhibiting sympathetic centers in posterior hypothalamus that cause vasoconstriction

21

what are the main mechanisms to reduce body heat

vasodilation of skin blood vessels, sweating, decrease in heat production (due to inhibition of shivering and thermogenesis)

22

what are the main mechanisms to increase body heat

skin vasoconstriction, piloerection, and increase in thermogenesis

23

what is the primary motor area for shivering

dorsomedial portion of posterior hypothalamus

24

how does the dorsomedial portion of the posterior hypothalamus relate to the anterior hypothalamic pre optic area

normally inhibited by signals from heat center in anterior hypothalamic pre optic area

25

when is the dorsomedial portion of the posterior hypothalamus activated

excited by cold signals from skin and spinal cord

26

what is the most potent mechanism for increasing heat production

shivering

27

what is shivering orchestrated by

posterior hypothalamus

28

what type of neurons are activated when shivering occursq

alpha and gamma motor neurons

29

define chemical thermogenesis

increase in rate of cellular metabolism due to sympathetic stimulation (or norepinephrine in blood)

30

how is chemical thermogenesis related to epinephrine/norepinephrine

uncouples oxidative phosphorylation

31

how is chemical thermogenesis related to brown fat

degree of thermogenesis is directly rated to amount of brown fat

32

where is brown fat distributed in humans

interscapular space in infants

33

what effect does increased thyroxine output have on cellular metabolism

activates uncoupling protein

34

what in the uncoupling protein that thyroxine activates

mitochondrial inner membrane protein that can dissipate the proton gradient before it can be used to provide the energy gradient for oxidative phosphorylation energy is used to generate heat)

35

what is the critical body core temperature

37.1 degrees celcius or 98.8 degrees F

36

how does core temperature relate to heat loss and heat production

heat loss is greater at temperatures above this temperature and heat production is greater at temperatures below this temperature

37

define set point

level at which sweating begins or shivering begins in order to return to critical core body temperature

38

what occurs if core temperature is less that set point

posterior hypothalamus activates heat-generating mechanisms

39

what occurs if core temperature is greater than set point

anterior hypothalamus activates heat loss mechanisms

40

define fever

body temperature above the usual range of normal

41

what do pyrogens do

increase set point temperature by increasing production of IL-1 in phagocytic cells

42

what does IL-1 cause the anterior pituitary to produce

prostaglandins

43

how does aspirin effect fever

decreases set-point temperature by inhibiting cycooxygenase which results in decrease production of prostaglandins

44

when is heat stroke likely to occur

when body temperature increases to point of tissue damage; normal response (sweating) is impaired and core temperature continues to rise

45

describe heat exhaustion

caused by excessive sweating; blood volume and arterial blood pressure decrease, resulting in fainting

46

describe malignant hyperthermia

caused by susceptible individuals by inhalation anesthetics. characterized by massive increase in oxygen consumption and heat production by skeletal muscle, leading to rapid rise in body temperature

47

describe hypothermia

ambient temperature is so low that heat-generating mechanisms cannot maintain core temperature near set point