Topic 67 - Heat balance regulation Flashcards
1
Q
Words to include
A
Defense against cold
- Heat conservation
- Diminishing heat-loss
- Muscular activity ↑
- Tonic (isometric) or shivering ↑
- Chemical (non-shivering) thermogenesis
- Brown adipose tissue (compared to white adipose tissue):
- Foamy
- intensive blood supply
- Mitochindria
- Heat production in brown adipose:
- Cold
- Sympathetic activation (epinephrine, norepinephrine)
- Futile cycle
- cAMP production
- Lipase activity ↑
- FFA level ↑
- Transport to other organs
- Oxidation
- Oxidation in mitochondria
- Transport to other organs
- Sympathetic excitation
- Adrenaline / noradrenaline effect
- Thyoxine effect
- Uncoupling of oxidative phosphorylation by thermogenins
- Calorigenic effect of thyroid hormones
- Heat production prolonged effect
- BMR
- Number of mitochondria
- Amount of thermogenin
- Activity of Na+/K+ pump
- Brown adipose tissue
- Foamy
- Fine IC granular content
- Intensive blood supply
- Many mitochondria
- High humber of cyochrome-oxidase
- α and β-adrenergic receptors on their surface
- Morpho-functional changes against cold
- Thickening of fur and subcutaneous tissue
- Secretion of calorigenic hormones ↑:
- Thyroid hormones
- Glucocorticoids
- Metabolic rate ↑
- Superficial vasoconstriction (a/v shunt)
Defense against heat
- Humid heat loos: evaporation
- Persipiratio sensibilis
- Sweating
- Persipiratio insensibilis
- Diffusion from surface of alveoli, skin and oral mucous membranes
- Panting
- Persipiratio sensibilis
- Panting:
- Evaporation (water loss)
- Advantage: Influence degree of heat loss
- Disadvantage: Alkalosis and consume energy
- Behaviroal defense reactions
- Dry heat loss
- Conduction
- Direct contact with surrounding objects
- Convetion
- Air/water touching body
- Morpho-functional changes against heat:
- Thickness and density of insulating layers ↓
- Heat dissipating mechanisms
- Vasodilation
Circulation and heat balance
- Hypothalamic center
- Control body temperature
- Circulation in heat:
- Superficial skin layer
- Precapillary sphincters open
- Deep system:
- Major veins contract
- Superficial veins dilate
- Superficial skin layer
- Circulation in cold:
- Superficial skin layer
- Precapillary sphincters close
- Deep system:
- Major veins dilate
- Superficial veins contract
- Superficial skin layer
Specialized structures
- Defense against major heat loss through limbs
- Looping heat exchange
- Warm blood flowing towards limbs can get cool
- Ø temperature gradient among body and environment
- Warm blood flowing towards limbs can get cool
- Looping heat exchange
- Counter current heat exchange
- In hot
- In the leg of birds (rete mirabile)
- In cold
- In head (rete of carotis)
- In testicles (rete testis)
- In hot
- Heat tolerant species
- Sheep
- Cooling of brain and CNS
Central thermoregulation
- Hypothalamic center
- Thermostat
- Set value of core temperature
- Effector system
- Maintain body temperature near to hypothalamic set-point
- Receptors
- Peripheral
- In organs
- Afferentation
- Hypothalamic termostat
- Efferentation
- Somatic
- Vegetative
- Hormonal
- Hypothermia
- Below controllable range
- Metabolism ↓
- Heat / respiratory frequency ↓
- Circulatory failure
- Hypercapnia
- Too much CO2 in blood
- Hypoxia
- Too little dissolved CO2
- Hypercapnia
- Disorders of:
- Digestion
- Absorption
- Kidney functions
- Fainting
- Ventricular fibrillations
- Hyperthermia
- Insufficient operation of heat dissipating mechanism
- Metabolism ↓
- Corruption of circulation → overheating shock
- Hypercapnia
- Hypervolemia
- Loss of salts and water
- Muscle seizure
- Fever
- Fever
- Fever is a regulated hyperthermia
- Induced by:
- Infections
- Inflammations
- Tissue destruction
- Induced by:
- Exogenous pyrogens get into organism
- Macrophage activation
- Formation of interleukin-1 & 6
- Direct stimulation of hypothalamic heat center by local prostaglandin (PGE1) release
- Pyrogens
- Endotoxins of Gram-negative bacteria
- Heat stable polysaccharides
- Membrane derbis
- Lipopolysaccharide fragments
- Pyrogens set hypothalamic set point to a higher temperature
- Incude heat production and heat conserving processes
- Shivering
- Temperature stabilizes at a higher value
- Removing pyrogens → set point drops back to previous normal value
- Sweating (cooling mechanism starts to work)
Acclimatization
- Adaption
- Shift to lower/higher critical temperature
- Shift of thermoneutral zone
- Shift to lower/higher critical temperature
- Morpho-functional changes in heat:
- Thickness and density of insulating layers ↓
- Dominance of heat dissipating mechanisms
- Activation of sweat glands
- Activity of respiratory muscles ↑
- Superficial vasodilation of skin
2
Q
Topics to include in the essay
A
- Maintaining constant body temperature
- Defense against cold
- Sympathetic excitation
- Calorigenic effect of thyorid hormones
- Brown adipose tissue
- Morpho-functional changes against cold
- Hypothermia
- Defense against heat
- Panting
- Morpho-functional changes against heat
- Hyperthermia
- Defense against cold
- Circulation and heat balance
- Circulation in heat
- Circulation in cold
- Specialized structure
- Limbs (defense against heat-loss)
- Heat tolerant species (sheep)
- Central thermoregulation
- The fever
- Acclimatization
3
Q
Defense against cold
A
-
Heat conservation: diminishing heat-loss
- Animals living in groups cuddle up to each other diminishing the surface are of heat loss
-
Muscle activity ↑
- Tonicity (isometric) or shivering ↑
-
Chemical (non-shivring) thermogenesis
- If the two above-mentioned forms are not able to maintain the constant body temperature
Sympathetic excitation
- Effect of adrenaline / noradrenaline
- Long term thyroxine effects
- (Uncoupling of oxidative phosphorylation by thermogenin)
Calorigenic effect of thyroid hormones
- Prolonged effect on heat production
- Basic metabolic rate (BMR)
- Number of mitochondria
- Increase energy consumption and heat production
- Amount of thermogenin
- Activity of Na+/K+ pump
Brown adipose tissue
- Foamy
- Fine IC granular content
- Intensive blood supply
- Many mitochondria
- High number of cytochrome-oxidase
- α and β-adrenergic receptors on their surface
Hypothermia
- Body temperature decreases below the controllabele range
- Metabolism ↓
- Heart / respiratory frequency ↓
-
Circulation failute
- Hypercapina (too much CO2 in blood)
- Hypoxia (too little dissolved CO2)
- Disorders of:
- Digestion
- Absorption
- Kidney functions
- Fainting
- Ventricular fibrillations
Morpho-functional changes
- Thickening of fur coat and subcutaneous adipose tissue
-
Calorigenic hormones increases secretion:
- Thyroid hormones ↑
- Glucocorticoids ↑
- Metabolic rate ↑
- Superficial vasoconstrictor mechanism of sikn (a/v shunt)
Figure: heat production in brown adipose
4
Q
Defense against heat
A
-
Humid heat-loss: evaporation:
-
Perspiratio insensibilis
- Panting by diffusion from the alveoli, skin and oral mucous membranes
-
Perspiratio sensibilis
- Sweating
-
Perspiratio insensibilis
-
Panting:
- Advantage: animal can actively influence the degree of heat-loss
- Disadvantage: excessive panting can cause alkalosis and consumes energy
Hyperthermia:
- Insufficient operantion of heat dissipating mechanisms:
- Metabolism ↓
- Corruption of circulation → overheating shock
- Hypercapnia
- Hypeovolemia
- Water and salt loss
- Muscle sizure
Morpho-functional changes:
- Thickness and density of isulation layers ↓
- Activation of sweat glands
- Aldosterone effect
- Respiratory muscles ↑
- Superficial vasodilation of skin
5
Q
Circulation and heat balance
A
- Thermal conductivity of tissues is lower, therefore are heat transported between the organs, inner body parts and the body surface
- Thermoneutral zone
- Circulation in heat:
- Superficial skin layer:
- Precapillary sphincters open
- Deep system:
- Major veins contract
- Superficial veins dilate
- Superficial skin layer:
- Circulation in cold:
- Superficial skin layer:
- Precapillary sphincters close
- Deep system:
- Major veins dilate
- Superficial veins contract
- Superficial skin layer:
6
Q
Specialized structures in different species
A
- Defense against major heat loss through limbs:
- Looping heat exchange
- Warm blood flowing towards the limbs can get cool to a degree that close to the ground there is hardly any temperature gradient among the body and the environment
- Polar animals that are exposed to extremely low temperatures has a much higher proportion of unsaturated fatty acids in the cells of the limbs compared to other body parts
- Heat tolerant species (sheep) have special circulatory units
- Ensuring cooling of brain and CNS
- Plexus of nasal cavity: cools blood by panting
- Cooled venous blood gets to ring of Willsius
- Blood of ascending a. carotis gets cooled by heat exchang before reaching the brain
- Ensuring cooling of brain and CNS
7
Q
Central thermoregulation
A
- The hypothalamic center as a thermostat determines a certain set point value for the core temperature
- The effector systmes are used to maintain body temperature near to the hypothalamic set-point
8
Q
The fever
A
-
Pyrogens:
- Endotoxins of Gram-negative bacteria
- Heat stable polysaccharides
- Membrane derbis
- Lipopolysaccharide fragments
- At the beginning of fever process the pyrogenic substance sets the hypothalamic set point to a higher temperature
- This induces heat production and heat conserving processes (shivering)
- As the current value reaches the set point the fever temperature becomes stabilized at a higher value
- After removing the pyrogenic substance the set point drops back to the previous normal value:
- Cooling mechanisms start to work (sweating) and the fever becomes solved
- Feves is regulated hyperthermia
-
Influenced by:
- Infection
- Inflammations
- Tissue destruction
-
Influenced by:
- Exogenous pyrognes get into the organism
- Macrophage activation
- Formation of:
- Interleukin-1
- Interleukin-6
- Direct stimulation of hypothalamic heat center by local prostaglandin (PGE1) release
- Hypothalamic regulation
9
Q
Acclimatization
A
- Adaptation can shift the lower or higher critical temperature (shift of the thermoneutral zone) to higher or lower levels