Thermoregulation & Extreme Conditions and Regulation

Question 1

brain

Answer 1

(hypothalamus)

• the temperature regulation center of the body (37˚C)
• responds directly to changes in core temperature and to nerve impulses from receptors in the skin
• then coordinates appropriate nervous and hormonal responses to counteract the changes and restore normal body temperature
• negative feedback: detects a return to normal temperature and the corrective mechanisms are switched off

Question 2

factors causing heat loss/cold response

Answer 2

• wind chill factor accelerates heat loss through conduction
• heat loss due to temperature difference between the body and the environment
• the rate of heat loss from the body is increased by being wet, by inactivity, dehydration, inadequate clothing, or shock

Question 3

counteracting heat loss

Answer 3

these responses are mediated primarily thought the sympathetic nerves of the autonomic nervous system

• thyroxine increases metabolic rate
• erector muscles of hairs contract, raising the hairs and increasing the insulating air layer
• under conditions of extreme cold, adrenaline and thyroxine increase the energy releasing activity of the liver
• muscular activity (shivering) produces internal heat
• vasoconstriction: blood vessels to the skin constrict and blood flow to skin decreases keeping warm blood near the core

Question 4

factors causing heat gain

Answer 4

• gain of heat directly from the environment through radiation and conduction
• excessive fate deposits make it harder to lose the heat that is generated through activity
• heavy exercise, especially with excessive clothing

Question 5

counteracting heat gain

Answer 5

these responses are mediated primarily through the parasympathetic nerves of the autonomic nervous system

• sweating increases, cooling by evaporation
• muscle tone and metabolic rate decrease, reducing the body’s heat output
• vasodilation: blood vessels to the skin dilate; warm blood from the body core is transported to the skin, and heat is lost from the skin surface
• erector muscles of hairs relax, flattening the hairs to decrease the insulating air layer

Question 6

explain why a dab of methanol or ethanol on the skin feels cold, even if the liquid is at room temperature

Answer 6

while the alcohol is evaporating, it absorbs heat (and thus feels cold) from both the skin underneath it and also from the air around it

Question 7

blood vessels

Answer 7

in the dermis dilate or constrict to promote heat loss

Question 8

hairs

Answer 8

raised or lowered to increase or decrease the thickness of the insulating air layer between the skin and environment

Question 9

sweat glands

Answer 9

produce sweat, which cools through evaporation

Question 10

fat

Answer 10

in the sub-dermal layers insulates the organs against heat loss

Question 11

thermoreceptors

Answer 11

in the dermis are free nerve endings which respond to changes in skin temp and send that info to the hypothalamus there are hot and cold ones

Question 12

why does a person from a cool climate have difficulty regulating their body temperature when visiting a hot climate?

Answer 12

people are born with an excess of sweat glands, but if they spend the first years of their life in a cold climate most of these become permanently inactive people acclimatized to a warm climate produce sweat profusely and the sweat is distributed uniformly –> increases efficiency of heat loss

Question 13

hypothermia

Answer 13

• when the core body temp drops below 35 deg caused by exposure to low temps and results from the body’s inability to replace the heat being lost to the environment
• the body starts losing heat more quickly than it can produce it resulting in the body temperature going down rapidly
• fun fact: exposure to cold water produces symptoms faster because water is better than air at conducting heat away from the body

Question 14

hypothermia symptoms

Answer 14

shivering, fatigue, increased heart rate, weak pulse, rapid, shallow breathing, confusion

severe: severe mental confusion (including inability to speak and amnesia), organ and heart failure, and death

Question 15

treating hypothermia

Answer 15

• passive rewarming: (for mild hypothermics) using their own body heat coupled with warm, dry, insulated clothing in a warm dry environment
• active external rewarming: (moderate) warming devices such as hot water bottles or warm water baths
• active internal/core warming: (severe) delivery of warm intravenous fluids, inhaling moist air, or warming the blood externally by using a heart-lung machine

Question 16

mild hypothermia

Answer 16

• shivering
• vasoconstriction reduces blood flow to extremities
• hypertension and cold diuresis (increased urine production due to cold)

Question 17

moderate hypothermia

Answer 17

• muscle coordinate becomes difficult
• movements slow/labored
• blood vessels in ears, nose, fingers, and toes constrict further resulting in these turning a blue color mental confusion

Question 18

severe hypothermia

Answer 18

speech fails irrational mental processes organs and heart eventually fail –> death

Question 19

hyperthermia

Answer 19

when the core body temp exceeds 38.5 deg without a change to the setpoint of the heat control center in the hypothalamus

Question 20

how is hyperthermia different from a fever?

Answer 20

hyperthermia is based on external conditions and the hypothalamus is unable to control the temperature rise, while a fever is a response to an infection in the body

Question 21

causes of hyperthermia

Answer 21

dehydration, hot environment, exercise, response to some drugs

Question 22

treating hyperthermia

Answer 22

external treatments:

• mild: drinking water, removing excess clothes, resting in a cool place
• worse: sponging body with cool water, using cooling blankets/ice-packs, wrapped in wet sheets with a fan, bathtub of cool water
• internal treatments: (severe) cool intravenous fluids, flushing stomach or rectum with cold water, hemodialysis

Question 23

overexertion

Answer 23

phase 1

• accompanied with a red flushed face and rapid short breaths
• correction is by seeking shade and drinking fluid

Question 24

heat exhaustion

Answer 24

phase 2

• profuse sweating, dry mouth, cramps, nausea
• skin will appear red as blood is directed to the skin to reduce core temp
• physical activity should be stopped and shade should be found cool drinks and ice packs

Question 25

heat stroke

Answer 25

phase 3

• thermoregulatory mechanisms fall
• sweat is no longer produced and skin becomes hot and dry
• disorientation then unconsciousness
• metabolic processes become uncoupled and enzymes denature death

Question 26

ecstasy/MDMA

Answer 26

• shuts down blood flow to the skin and mimics serotonin
• changes temp regulation, heart rate, blood pressure, and appetite control
• reduces blood flow to skin and decreases sweating –> reduces heat loss -increases metabolic rate –> increases heat generation
• decreases thirst recognition –> increases dehydration
• hyperthermia is one of the major side effects -
• can result in death body temp increases but can’t regulate
• brain cells die
• serotonin from ecstasy attaches to brain cells and doesn’t fall off until neuron dies