CH 2 Temperature Flashcards
Balance between the heat produced or acquired by the body and the amount lost
Body temperature
Warm-blooded
Homoiothermic
Cold-blooded
Poikilothermic
To maintain a relatively constant internal body temperature; monitors and acts to maintain temperatures that are optimal for normal cellular and vital organ function
Purpose of Thermoregulatory System
What are the three primary components of the thermoregulatory system?
Thermoreceptors, regulating center, and effector organs
Provides input to the hypothalamus
Thermoreceptors
Temperature regulating center
Hypothalamus
(skin temp); composed primarily of of free nerve endings and have a high distribution in skin
Peripheral Receptors
(core temp); located in deep tissues (abdominal), nervous system, and hypothalamus
Central Thermoreceptors
Demonstrate a larger distribution of cold receptors than warmth receptors; sensitive to rapid changes in temp
Cutaneous peripheral thermoreceptors
Signals enter spinal cord through afferent nerves and travel to the hypothalamus via the lateral spinothalamic tract
Cutaneous peripheral thermoreceptors
Sensitive to temperature chages in blood perfusing the hypothalamus; also initiate responses to converse or dissipate heat
Thermoreceptors in hypothalamus
Particularly sensitive to core temperature changes and monitoring body warmth; permit feed forward responses to expected changes in core temp
Thermoreceptors in hypothalamus
Coordinates heat production and loss processes (like a thermostat)
Hypothalamus
Respond and function to increase and dissipate body heat
Effector Organs/Systems
What are the primary effector systems?
Vascular, metabolic, skeletal muscle (shivering), and sweating
Mechanisms are activated to conserve heat and increase heat production when?
When body temperature is lowered
What are the heat conservation and production mechanisms?
Vasoconstriction of blood vessels, decrease of sweat gland, cutis anserina or piloerection (gooseflesh), shivering and hormonal regulation
When the hypothalamus activates the sympathetic nerves, resulting in vasoconstriction of cutaneous vessels throughout the body
Vasoconstriction of blood vessels
Significantly reduces the lumen of vessels and decreases blood flow near the surface of skin (where blood is normally cooled)- reducing the amount of heat lost
Vasoconstriction of blood vessels
To reduce or to prevent heat loss by evaporation
Decrease sweat gland activity
Hairs standing on end
Piloerection
Goose flesh
Cutis anserina
Functions to trap a layer of insulating air near the skin and decrease heat loss in lower mammals with greater hair covering
Cutis Anserina and Piloerection
What mechanisms are designed to produce heat when decreased body temp occurs?
Shivering and hormonal regulation
Primary motor center for shivering
Posterior hypothalamus
Activated by cold signals from the skin and spinal cord
Posterior hypothalamus
What can be partially suppressed through conscious cortical control and voluntary muscle activity?
Shivering reflex
How does shivering work in response to cold?
Impulses from the hypothalamus activate efferent somatic nervous system causing increased tone of skeletal muscles to increase to a certain threshold level
Function in thermal regulation is to increase cellular metabolism, which increases the body heat
Hormonal influences
When increased metabolism occurs through circulation of hormones from the adrenal medulla: norepinephrine and epinephrine is called what?
Chemical Thermogenesis
What is more important in infants than adults because hormones increase heat by 100% compared to 10-15% in adults?
Chemical Thermogenesis
4 primary methods to dissipate excess heat from the body
Radiation, conduction, convection, and evaporation
Transfer of heat by electromagnetic waves from one object to another accomplished by radiation
Radiation
Heat transfer occurs through the air between objects not in direct contact; heat lost to surrounding objects that are colder than the body
Radiation
Transfer of heat from one object to another through a liquid, solid or gas
Conduction
This type of heat transfer requires direct contact between two objects; heat lost by conduction to air
Conduction
Transfer of heat by movement of air or liquid (water)
Convection
Accomplished secondary to conduction
Convection
Heat loss is most effective when air or liquid surrounding the body is continually moved away and replaced
Convection
Heat is conducted to the air, then air is moved away from the body by currents
Convection
Dissipation of body heat by conversion of a liquid to a vapor
Evaporation
Heat loss occurs on a continual basis through the respiratory tract and through perspiration of skin
Evaporation
Provides major mechanism of heat loss during exercise
Evaporation
Elevation of normal body temperature- commonly known as fever
Pyrexia
Occurs when the “set” value of the hypothalamic thermostat is triggered to rise by circulating pyrogens secreted from toxic bacteria, viruses, and injured body tissue
Fever
Signs and symptoms: general malaise, headache, increased pulse and respiratory rate, chills, piloerection, shivering, loss of appetite, skin flushes and hot to touch, nausea, irritability, restlessness, constipation, sweating, thirst, coated tongue, decreased urinary output, weakness, insomia
Signs and symptoms of fever
Period of fever that occurs just prior to onset; symptoms: slight headache, muscle aches, general malaise, or loss of appetite
Prodromal
Period of fever from either gradual or sudden rise until the maximum temperature is reached
Phase one fever: onset
Symptoms of phase one fever: onset?
Chills, shivering, and pale appearance of skin
Which fever phase? As body temp is raised, vasoconstriction moves blood to the interior of the body to retain heat; the skin becomes cool and shivering is initiated to produce more heat
Phase one fever: onset
Which phase of fever attempts to preserve and produce heat continue until a new, higher temp is reached
Phase one fever: onset
Period of fever that is the point of highest elevation of fever
Phase two fever: course
Which phase of fever remains relatively stable once the higher temp is reached?
Phase two fever: course
Which phase of fever is when heat production and heat loss are equal so the shivering stops?
Phase two fever: course
Which phase of fever has skin warm to the touch and appearing flushed?
Phase two fever: course
Which phase of fever occurs when the fever subsides and temp lowers until normal?
Phase three fever: Termination
Which phase of fever has vasodilation occurring and sweating to help cool the body?
Phase three fever: Termination
What are the types of fevers?
Continuous, intermittent, relapsing, remittent
What type of fever is when body temp is constantly elevated above normal throughout day but does not fluctuate more than 1.8*F
Continuous (constant, sustained) fever
What type of fever is seen in uncomplicated minor infection, UTI, lobar pneumonia,typhoid (foodborne illness), infective endocarditis, typhus (flea-borne disease)
Continuous (constant, sustained) fever
