Physiology 2 week 6 Flashcards
When does the body temperature rise?
When heat production exceeds heat loss
When does the body temperature decrease?
When heat loss surpasses heat production
What is heat a by product of?
Metabolism
Name 3factors heat is influenced by?
- Basal metabolic rate of body cells
- Increased metabolism from muscle activty
- Effects of hormones like throxyine, growth hormones and testtosterone
Name and describe the 2 steps heat transfer occurs
- Conducting heat from internal organs to the skin.
2.Transferring heat from the skin to the surroundings
Name insulators in the insulator system and their role
- Skin, subcutaneous tissues and fat
- They reduce the heat loss
What is the role of insulation system
It allows skin temperature to mach the surroundings while maintaining stable internal core temperatures
Explain how the blood vessels in the skin work
-Skin has a venous plexus beneath it, recieving blood from the capillaries
- In hands, feet and ears arteriovenous anastomes direclty supply bood to the plexus.
What is the role of High blood flow?
- It effectively conducts heat from the body core to the skin
What is the function of reduced blood flow
- Minimizes heat transfer
What is the blood flow to the skin regulated by and controlled by?
-It is regulated by vasoconstriction of arterioles and arteriovenous anastomoses.
Controlled by the sympathetic nervous system in response to changes in body core and environmental temperature.
Name the 3 methods of heat loss
- Radiation
- Conduction
- Evaporation
What happens in Radiation?
When does heat loss occur ?
- Heat radiates as infrared rays
- Heat loss occurs if the bodys temperature is higher than its surroundings ?
What happens in conduction?
How is heat transferred ?
When does heat transfer stop?
- Heat transfers via direct contact
- Heat transfer stops when air temperature equals skin temperature unless the heated air is replaced
What happens in convection?
How is heat transferred?
- Heat is transferred from the skin to air and carried away by moving air currents
Compare SHC, heat loss and insulating layers in water and air
- Water has a higher SHC than air
- Heat loss in water is greater than in air
- Both have not insulating layers
What is insensible evaporation?
- When water evaoprates insensibly from the skin to the lungs even when a person is not sweating
When is evaporation neccessary
When the surrounding air temperatures exceeds the skin temperature , so then heat is gained from the environment via conduction and radiation
What happens to individuals with an absence of sweat glands
They cannot loose heat effecitvely leading to heatstroke risks
What is the effect of clothing on heat loss
- Clothing traps the air near the skin, reducing heat loss by conduction and convection
What does coating clothes in reflective metals do?
- Enhances insulation by reflecting radiant heat back to the body
Does wet clothes reduce or increase heat loss
increases heat loss
What is the role of the Anterior hypothalamus preoptic area
- Stimulates sweating in response to heat
Explain the Autonomic pathway for sweating
- The sweating signals travel through cholinergic sympathetic nerve fibers, which release acetylcholine
Explone the hormonal influence in response to sweating
- Epinephrine and Norepinephrine frome the adrenal medulla can also stimulate sweat glands indirectly during exercise
Describe the structure of a sweat gland and its functions
- Coiled secretory protein( produces percursor fluid)
-Duct portion ( modifies fluid)
What happens to Na and Cl at low sweating rates
- ## They are reabsorbed, reducing their concentrations
What happens to Na and Cl at high sweating rates
-There is less reabsorption, resulting in higher Na and Cl concentrations
What is the body temperature regulated by?
- The nervous feedback mechanisms and these mechanisms operate via the temperature regulating centers in the hyopthalamus
What does the anterior hypothalamic preoptic area contain?
- Heat senesitive nerons
- Cold sensitive neurons
What happens when the anterior hypothalamic preoptic area is heated?
- Profuse sweating occurs across the body
- The skin blood vessels dilate
What receptors does the skin have?
Cold and warmth receptors
Where are the deep body receptors found?
- Spinal cord, abdominal viscera around great veins in upper abdomen
What is the role of deep body detectors
- They detect core body temperature , focusing in cold detection to prevent hypothermia
Name the 3 reflex responses to chilling(cold)
- Shivering- increase heat production
-Sweating- reduce heat loss
-Vasconstriction- minimise heat loss from the skin
What does the Posterior hypothalamus integrates?
- Peripheral temperature signals
-central signals from the anterior hypothalamic preoptic area
What are the mechanisms that take place to decrease the body temperature when it is too high
- Vasodilation:
- Sweating
-Decrease in heat production: - inhibiting shivering and chemical thermogenesis
What happens in vasodilation
- The blood vessels in the skin dilate due to the inhibition of sympathetic vasoconstrictor centres in the posterior hypothalamus
What are the mechanisms that take place to increase the body temperature when it is too cold
- Vasoconstriction
- Pilo erection
- Increase in heat production:
stimulating shivering and thyroxine secretion
What is the function of vasoconstriction and what is it caused by
-Reduces heat loss
Caused by the stimulation of the posterior hypothalamus sympathetic centers
What is the function of throxyine in increasing the body temperature
- Boosts cellular meabolism, enhancing heat production
What is shivering controlled by
- Primary Motor center for shivering
critical body
What is the set point
- Critical body temperatures that the temperature control mechanisms aim to maintain
What happens at temperatures above the set point
- Heat loss exceeds heat production causing a decress in body temperature
measure of
What is the feedback gain
- A measure of the effectiveness of temperature regulation
What influence does the skin receptors have on the set point
-Signals from the skin receptors can modify the hypothalamic set point
Give 2 examples of psychological behavioural adjustments
- Feeling cold- move to a warmer area
- Feeling warm- Move to a cooler area
What is the most effective mechanism for maintaining body heat
- Behaviour control
What is a fever
- Elevated body temperature beyond the normal range
What is a fever caused by
- Brain abnormalities,Toxic substances,infections,brain tumours
What is the mechanism of a fever- when does it occur
- When the hypothalamic set point is raised dye to pyrogens
Where do pyrogens originate from
- Toxins
What is the role of pyrogens
- They act directly on the hypothalamus to increase the set point
o - They act indirectly through intermediates like (cytokines)
