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33 Cards in this Set

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Refers to the temp of the deep tissues of the body
Core Temp
How do rectal and oral temperatures differ?
Rectal temp is about 1 degree higher than oral temperature
How can behavior modulate body temperature?
Body temp increases with exercise and decreases in conditions such as extreme cold
How is heat produced in the body?
1. Basal rate of metabolism of all cells in the body 2. Extra rate of metabolism caused by muscle activity, including muscle contractions caused by shivering 3.Extra metabolism caused by the effect of thyroxine (and other hormones) on the cells 4. Extra metabolism caused by the effect of Epi, Norepi, and sympathetic stimulation on cells 5. Extra metabolism caused by increased chemical activity in the cells themselves, especially when the cell temperature increases 6. Extra metabolism needed for digestion, absorption, and storage of food (thermogenic effect of food)
What 3 things act as the "insulator system for the body"
Skin, Subcutaneous tissues, subcutaneous fat
How is heat transferred from the core of the body to the skin?
Through blood flow. A high rate of blood flow=heat conducted from the core to the skin with great efficiency. A reduction in the rate of skin blood flow=decreased heat conduction from the core
How does the sympathetic nervous system help with heat conduction to the skin?
By almost entirely controlling the vasoconstriction of the arterioles and arteriovenous anastomoses that supply blood to the venous plexus of the skin.
Explain the idea of "set-point"
At a critical body core temp of about 37.1 C or 98.8 F, drastic changes occur in the rates of both heat loss and heat production. Above this temp, the body loses more heat than it produces. Below this temp, the body produces more heat than it loses. This is the body's way to continually attempt to bring the body back to this set-point level
What are the mechanism for heat loss?
Radiation; Conduction/Convection; Evaporation
How is body temperature detected?
Hypothalamus temperature control center; Skin and deep body temp receptors; Role of post. Hypothalamus
How does the preoptic area work to regulate body temperature?
When the preoptic area is heated, the skin all over the body immediately breaks out in a profuse sweat, while the skin blood vessels over the entire body become greatly dilated--causing the body to lose heat. It also inhibits the body from producing excess body heat.
How do the skin and deep body temp receptors work to try to regulate body temp?
There are more cold receptors than warmth receptors. So when the skin is chilled, immediate reflex effects are invoked: 1. Cause shivering 2. Inhibit sweatin 3. Promote skin vasoconstriction to diminish loss of heat from skin
How does the posterior hypothalamus work to try to regulate body temp?
Receives input from anterior hypothalamus and peripheral temp receptors to elicit mainly heat producing and heat conserving reactions
The removal of heat from the body by air currents
Convection
Method by which most of the heat is lost from the skin to surroundings
Radiation
What are the mechanisms for lowering body temperature?
Vasodilation; Sweating; Decreased heat production
This temp decreasing mechanism transfers heat to skin by inhibition of sympathetic centers in the post. Hypothal that cause vasoconstriction
Vasodilation
This temp decreasing mechanism works by stimulating the preoptic ares of the hypothalamus which in turn stimulates this mechanism via sympathetic cholinergic fibers
Sweating
This temp decreasing mechanism works by inhibiting shivering and chemical thermogenesis
Decreased heat production
What are the mechanisms for increasing body temp?
Vasoconstriction; Piloerection; Increase heat production
This temp increasing mechanism works by impeding heat transfer to skin by stimulating sympathetic centers in the posterior hypothalamus
Vasoconstriction.
Shivering, sympathetic excitation of heat production, and thyroxine secretion all work to:
Increase heat production
What can reset the set-point?
Pyrogens
How can pyrogens directly reset the set-point?
Pyrogens released from toxic bacteria or those released from degenerating body tissues can cause fever during disease conditions. When the set-point becomes higher than normal, all the mechanisms for raising body temp come into play, causing body temp to approach this new level
How can pyrogens indirectly reset the set-point?
Interleukin-1 released from phagocytes following phagocytosis of blood-borne pyrogens. IL-1 raises set-point by increasing prostaglandin production (mainly E2)
How does aspirin work to reduce fever?
Fever is caused indirectly by prostaglandins (which form as a result of IL-1 from bacteria). Prostaglandins form from arachiconic acid--aspirin impedes this formation process of prostaglandins
What is crisis or flush?
When factor causing high set-point is removed, but body temp is still hight, the excessive heating of the hypothalamic preoptic area causes intense sweating and hot skin b/c of vasodilation everywhere. This causes body temp to come down
What temp is the body when a heat stroke occurs?
106-108
What causes heat stoke?
Malfunction of preoptic temp control center--sweating ceases
What is the "vicious cycle" that exacerbates heat stroke?
Rising body temp increases metabolism (Q10 effect) which generates more heat
How does the body lose ability to regulate body temp at low temperatures?
Once body falls below 85 F, ability of hypothalamus to regulate temp is lost. The rate of chemical heat production in each cell is depressed almost 2-fold for each 10 F decrease in body temp. Also, sleepines develops (followed by coma) which depresses the activity of the CNS heat control mechanisms and prevents shivering
What is frostbite?
When the body is exposed to extremely low temperatures and surface areas freeze. If it causes formation of ice crystals in the cells, permanent damage results.
What is cold-induced vasodilation?
When temp of tissue fall almost to freezing, smooth muscle in vascular walls become paralyzed b/c of the cold and sudden vasodilation occurs, often manifested by a flush of the skin.