Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
71 Cards in this Set
- Front
- Back
|
For the body, what acts as a
-Radiator system -Insulator system |
Radiator = the circulation
Insulator = clothes and fat |
|
|
What is the anatomy of cutaneous (skin) circulation like?
|
A very dense system of capillary loops
|
|
|
What is the structure of subpapillary venous plexi like?
|
-Large volume
-In close proximity to body surface |
|
|
What is the bloodflow through subpapillary venous plexi like?
|
Slow - low flow velocity
|
|
|
Function of Arteriovenous anastomoses:
|
Allows fast shunting of hot blood from arteries to veins
|
|
|
Are arteriovenous anastomoses always open?
|
No; in cold they are shut.
|
|
|
How does blood get shunted more quickly by arteriovenous anastomoses?
|
It doesn't have to go through capillaries first.
|
|
|
What is the prominent controller of skin circulation?
|
Sympathetic outflow
|
|
|
What type of receptors are on cutaneous arteries?
|
Predominantly alpha adrenergic receptors (few beta)
|
|
|
How does sympathetic stimulation alter arteries?
|
It causes vasoconstriction
|
|
|
What is the normal resting state of cutaneous arteries at normal body core and skin temp?
|
Vasoconstricted due to tonic sympathetic outflow.
|
|
|
What allows vasodilation of cutaneous arteries?
|
Decreased sympathetic outflow, as well as some innervation by Cholinergic fibers.
|
|
|
What is the structure of cutaneous veins like? Why?
|
Highly compliant - allows them to act as a large reservoir of blood - like a floodwater plain to allow evaporation, lets blood release from skin surface when filled.
|
|
|
What type of nerve receptors are on Cutaneous veins?
|
Alpha adrenergic - like the arteries.
|
|
|
What does sympathetic outflow do to cutaneous veins?
|
Causes constriction
|
|
|
What is the system that controls vasoconstriction and dilation?
|
The Hypothalamic Thermoregulatory Reflex Control
|
|
|
How is Core temp different from Skin temp?
|
Core temp varies much LESS than skin temp; remains constant in spite of fluctuations of atmospheric temp
|
|
|
What are the 2 components involved in physiological control of temperature?
|
1. Hypothalamus
2. Peripheral temp sensors (in the skin and deep body tissues) |
|
|
How do peripheral sensors affect temperature control?
|
They alter the setpoint in the hypothalamus, above/below which sweating and shivering will occur.
|
|
|
What is the normal body temp range?
|
97 to 99.5
|
|
|
What can cause a body temp range of 99.5 - 101?
|
-Hard work
-Emotion -A few normal adults -Many active children |
|
|
What can cause a body temp range of 95.5 to 96.5?
|
-Early morning
-Cold weather |
|
|
At what range of atmospheric temps does body temp remain constant? Stipulation?
|
50 - 130 -> that is if the air is dry!
|
|
|
What happens to arteries in cold? In hot?
|
Cold = vasoconstrict
Hot = vasodilate |
|
|
Why do vessels constrict in cold?
|
-To reduce loss of body heat
-To maximize flow to deep organs like the brain and heart. |
|
|
What happens if you are adapted to wisconsin weather (Avg T=0) and go to the tropics (T=100)?
|
-Initially period of hypotension due to intense sweating
-Symptoms resulting from shunt of bloodflow from deep body organs to the skin |
|
|
How does increasing environmental temp affect heat conductance through skin? How?
|
It increases because the arteries go from a fully constricted state (up to 75) to fully dilated state (at 100).
|
|
|
What is the main mechanism of heat production in the body?
|
The metabolic rate
|
|
|
What is the main mechanism of heat loss in the body?
|
Heat transfer from deep organs to the skin by bloodflow.
|
|
|
What are the 2 determinants of heat loss?
|
1. Speed of conduction from deep organs to the skin
2. Speed of transfer from skin to environment. |
|
|
7 mechanisms for heat GAIN by body:
|
1. Metabolic heat production
2. Exercise 3. Shivering 4. Thyroxine 5. Sympathetic stimulation 6. Radiation 7. Conduction 8. Convection |
|
|
What are 4 mechanisms for heat LOSS by the body?
|
1. Radiation
2. Evaporation (of sweat) 3. Convection 4. Conduction |
|
|
How is heat lost by radiation?
How much? |
By the emission of infrared heat rays - dependent on the relative temp of body to atmosphere.
60% |
|
|
How is heat lost by conduction?
How much? |
Mainly by contact with air - 15%; (very small amt is directly through touching OBJECTS - 3%).
|
|
|
How is heat lost by convection?
How much? |
Air currents/wind has a major cooling effect; think about it as you sweat and air hits you get cold. This is the conduction to air - 15%
|
|
|
How is heat lost by evaporation?
How much? |
By loss of sweat from sweat glands; 22%
|
|
|
3 main mechanisms for heat loss:
|
1. Vasodilation
2. Sweating 3. Decrease in heat production |
|
|
How is vasodilation achieved?
|
By inhibiting sympathetic output -> decreases tonic vasoconstriction.
|
|
|
How much increase in heat loss can be achieved by inhibition of sympathetic vasoconstriction?
|
Up to 8x
|
|
|
How is Sweating achieved?
|
By stimulation of sweat glands when the core temp rises above the set point.
|
|
|
How does the body decrease Heat Production?
|
By inhibiting shivering and chemical thermogenesis.
|
|
|
What is the composition of sweat like?
|
Protein free plasma - mainly sodium and chloride.
|
|
|
How is sweat produced?
|
By epithelial cells of sweat glands; produce a precursor secretion.
|
|
|
What happens to the precursor solution secreted by glandular epithelial cells?
|
It is modified as it flows through sweat ducts - remove more solutes and water.
|
|
|
What is the final product of sweat gland ducts like?
|
High in Lactate, Urea, and body waste.
|
|
|
How does sweating help to reduce body temperature?
|
By removing heat via evaporative cooling.
|
|
|
What does excessive sweating do?
|
Causes increased Aldosterone secretion from adrenal cortex - to reabsorb more sodium from sweat.
|
|
|
When does excessive sweating occur?
|
When an unacclimatized person moves to a climate that is much warmer.
|
|
|
What is the response of an unacclimitized person in a warm climate?
|
-Initial hypotension due to excess loss of H2O/Na in sweat
-Then adaptation and less sweat production due to Aldosterone |
|
|
What types of nerves innervate sweat glands?
|
Cholinergic sympathetic nerves
|
|
|
What controls the formation and release of sweat?
|
The preoptic area of the anterior hypothalamus.
|
|
|
What stimulates sweat release?
|
-Cholinergic nerves
-Circulating Epi and NE during heavy exercise |
|
|
What is Behavioral thermoregulation?
|
An extremely important mechanism for controlling heat production in extremely cold environmental temps
|
|
|
Can behavioral thermoregulation play a role in losing excess heat in extremely warm environmental temps?
|
No; the only way to lose heat is via sweating and evaporation.
|
|
|
What are 3 main mechanisms for increasing body temperature?
|
1. Cutaneous vasoconstriction
2. Piloerection 3. Increased heat production |
|
|
How is cutaneous vasoconstriction achieved?
|
Via stimulation of posterior hypothalamic sympathetic centers.
|
|
|
What are 3 ways of increasing heat production?
|
1. Shivering
2. Chemical thermogenesis 3. Thyroxine secretion |
|
|
What type of neural control is shivering under?
|
Autonomic - cannot voluntarily cause shivering to stop.
|
|
|
Where is shivering initiated?
|
In the primary motor cortex
|
|
|
How is shivering caused?
|
By activation of motor neurons causing muscle spindle oscillations.
|
|
|
What is nonshivering thermogenesis?
|
Chemical thermogenesis
|
|
|
2 types of chemical thermogenesis:
|
-Sympathetic nervous system
-Brown fat |
|
|
What causes increased Thyroxine output and what is its effect?
|
-Caused by cooling of the preoptic region in hypothalamus;
-Result is TRH release, Thyroxine release, and increased metabolism generating heat. |
|
|
2 types of insulator systems:
|
-Fat/subcutaneous tissue/skin
-Clothing |
|
|
What is the most important type of insulator? Why?
|
Fat - because it conducts heat only about 1/3 as well as other tissues.
|
|
|
How does fat insulation affect core and skin temp?
|
-Insulates core because it is SUBcutaneous
-Lets skin temp approximate environmental temp |
|
|
How does clothing act as an insulator?
|
By trapping air and decreasing convective loss of heat.
|
|
|
What are 2 causes of fever?
|
1. Pyrogens
2. Brain lesions |
|
|
What are 3 pyrogens?
|
-Bacterial toxins
-IL-1 -Prostaglandins |
|
|
What brain lesions can alter body temp?
|
-Surgery in area of hypothalamus
-Brain tumors |
|
|
What causes heat stroke? Why?
|
Exercise - because the heat generated cannot be dissipated adequetely.
|
