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PHYSIOLOGY SEMESTER 2 > lecture 14-temperature regulation > Flashcards

lecture 14-temperature regulation Flashcards

1
Q

what is malignant hyperthermia triggered by

A

anesthetics

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2
Q

what main factors determine rate of heat loss

A

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

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3
Q

what is the continuous venous plexus in subQ supplied by

A

inflow of blood from capillaries from dermis

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4
Q

how is heat conduction to skin controlled

A

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

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5
Q

what is vasoconstriction controlled mostly by

A

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

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6
Q

describe radiation

A

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

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7
Q

define conduction

A

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

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8
Q

define convection

A

removal of heat from the body by convection air currents

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9
Q

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

A

0.58 calories of heat

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10
Q

define insensible perspiration

A

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

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11
Q

what does the amount of heat transferred by radiation depend on

A

temperature difference and ability of object to absorb energy

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12
Q

define evaporation

A

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

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13
Q

what are stimulating factors for sweating

A

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)

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14
Q

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

A

anterior hypothalamic pre-optic area and pre-optic area

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15
Q

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

A

both heat-sensitive and cold-sensitive neurons

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16
Q

describe heat sensitive neurons of the anterior pre-optic area

A

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

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17
Q

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

A

increase firing rate when temperature falls

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18
Q

what does heating the pre-optic area cause

A

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

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19
Q

T/F: vasodilation increases body heat

A

false; it decreases it

20
Q

how does vasodilation of skin blood vessels reduce body heat

A

by inhibiting sympathetic centers in posterior hypothalamus that cause vasoconstriction

21
Q

what are the main mechanisms to reduce body heat

A

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

22
Q

what are the main mechanisms to increase body heat

A

skin vasoconstriction, piloerection, and increase in thermogenesis

23
Q

what is the primary motor area for shivering

A

dorsomedial portion of posterior hypothalamus

24
Q

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

A

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

25
Q

when is the dorsomedial portion of the posterior hypothalamus activated

A

excited by cold signals from skin and spinal cord

26
Q

what is the most potent mechanism for increasing heat production

A

shivering

27
Q

what is shivering orchestrated by

A

posterior hypothalamus

28
Q

what type of neurons are activated when shivering occursq

A

alpha and gamma motor neurons

29
Q

define chemical thermogenesis

A

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

30
Q

how is chemical thermogenesis related to epinephrine/norepinephrine

A

uncouples oxidative phosphorylation

31
Q

how is chemical thermogenesis related to brown fat

A

degree of thermogenesis is directly rated to amount of brown fat

32
Q

where is brown fat distributed in humans

A

interscapular space in infants

33
Q

what effect does increased thyroxine output have on cellular metabolism

A

activates uncoupling protein

34
Q

what in the uncoupling protein that thyroxine activates

A

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
Q

what is the critical body core temperature

A

37.1 degrees celcius or 98.8 degrees F

36
Q

how does core temperature relate to heat loss and heat production

A

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

37
Q

define set point

A

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

38
Q

what occurs if core temperature is less that set point

A

posterior hypothalamus activates heat-generating mechanisms

39
Q

what occurs if core temperature is greater than set point

A

anterior hypothalamus activates heat loss mechanisms

40
Q

define fever

A

body temperature above the usual range of normal

41
Q

what do pyrogens do

A

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

42
Q

what does IL-1 cause the anterior pituitary to produce

A

prostaglandins

43
Q

how does aspirin effect fever

A

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

44
Q

when is heat stroke likely to occur

A

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

45
Q

describe heat exhaustion

A

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

46
Q

describe malignant hyperthermia

A

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
Q

describe hypothermia

A

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

PHYSIOLOGY SEMESTER 2 (20 decks)

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