lecture 14-temperature regulation

Question 1

what is malignant hyperthermia triggered by

Answer 1

anesthetics

Question 2

what main factors determine rate of heat loss

Answer 2

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

Question 3

what is the continuous venous plexus in subQ supplied by

Answer 3

inflow of blood from capillaries from dermis

Question 4

how is heat conduction to skin controlled

Answer 4

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

Question 5

what is vasoconstriction controlled mostly by

Answer 5

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

Question 6

describe radiation

Answer 6

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

Question 7

define conduction

Answer 7

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

Question 8

define convection

Answer 8

removal of heat from the body by convection air currents

Question 9

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

Answer 9

0.58 calories of heat

Question 10

define insensible perspiration

Answer 10

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

Question 11

what does the amount of heat transferred by radiation depend on

Answer 11

temperature difference and ability of object to absorb energy

Question 12

define evaporation

Answer 12

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

Question 13

what are stimulating factors for sweating

Answer 13

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)

Question 14

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

Answer 14

anterior hypothalamic pre-optic area and pre-optic area

Question 15

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

Answer 15

both heat-sensitive and cold-sensitive neurons

Question 16

describe heat sensitive neurons of the anterior pre-optic area

Answer 16

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

Question 17

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

Answer 17

increase firing rate when temperature falls

Question 18

what does heating the pre-optic area cause

Answer 18

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

Question 19

T/F: vasodilation increases body heat

Answer 19

false; it decreases it

Question 20

how does vasodilation of skin blood vessels reduce body heat

Answer 20

by inhibiting sympathetic centers in posterior hypothalamus that cause vasoconstriction

Question 21

what are the main mechanisms to reduce body heat

Answer 21

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

Question 22

what are the main mechanisms to increase body heat

Answer 22

skin vasoconstriction, piloerection, and increase in thermogenesis

Question 23

what is the primary motor area for shivering

Answer 23

dorsomedial portion of posterior hypothalamus

Question 24

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

Answer 24

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

Question 25

when is the dorsomedial portion of the posterior hypothalamus activated

Answer 25

excited by cold signals from skin and spinal cord

Question 26

what is the most potent mechanism for increasing heat production

Answer 26

shivering

Question 27

what is shivering orchestrated by

Answer 27

posterior hypothalamus

Question 28

what type of neurons are activated when shivering occursq

Answer 28

alpha and gamma motor neurons

Question 29

define chemical thermogenesis

Answer 29

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

Question 30

how is chemical thermogenesis related to epinephrine/norepinephrine

Answer 30

uncouples oxidative phosphorylation

Question 31

how is chemical thermogenesis related to brown fat

Answer 31

degree of thermogenesis is directly rated to amount of brown fat

Question 32

where is brown fat distributed in humans

Answer 32

interscapular space in infants

Question 33

what effect does increased thyroxine output have on cellular metabolism

Answer 33

activates uncoupling protein

Question 34

what in the uncoupling protein that thyroxine activates

Answer 34

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)

Question 35

what is the critical body core temperature

Answer 35

37.1 degrees celcius or 98.8 degrees F

Question 36

how does core temperature relate to heat loss and heat production

Answer 36

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

Question 37

define set point

Answer 37

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

Question 38

what occurs if core temperature is less that set point

Answer 38

posterior hypothalamus activates heat-generating mechanisms

Question 39

what occurs if core temperature is greater than set point

Answer 39

anterior hypothalamus activates heat loss mechanisms

Question 40

define fever

Answer 40

body temperature above the usual range of normal

Question 41

what do pyrogens do

Answer 41

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

Question 42

what does IL-1 cause the anterior pituitary to produce

Answer 42

prostaglandins

Question 43

how does aspirin effect fever

Answer 43

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

Question 44

when is heat stroke likely to occur

Answer 44

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

Question 45

describe heat exhaustion

Answer 45

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

Question 46

describe malignant hyperthermia

Answer 46

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

Question 47

describe hypothermia

Answer 47

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