Please enable JavaScript.

Coggle requires JavaScript to display documents.

Case 1: Thermoregulatuion, What is the Piloerection Reflex ? Arrector…

- - - - How is Heat produced through Muscle Activity ?
        Heat is produced through:
        
        Shivering Thermogenesis
        
        Shivering is an involuntary process, triggered by the Hypothalamus.
        Shivers are uncoordinated tremors, that result in 5-fold heat production.
        However, shivering requires a HIGH oxygen consumption of 3-8 fold.
        
        Other activities
        
        Other activities that also produce heat are as follows:
        Muscle Tone maintenance
        Voluntary activity
        
        How is Heat produced through Non-Shivering Thermogenesis ?
        Non-Shivering Thermogenesis is more prominent in Neonates, and less in adults.
        It occurs in brown fat which is rich in Mitochondria content.
        Areas with brown fat, and are rich in mitochondria:
        
        Scapula
        
        Mediastinum
        
        Kidneys
        
        In Non-Shivering Thermogenesis, Triglycerides are broken down to form Fatty acids and Glycerol, resulting in the release of Heat.
        This reaction is coupled with the Uncoupling Oxidative Phosphorylation.
        Non-Shivering Thermogenesis is initiated by sympathetic activation (Noradrenalin)
        The Onset is SLOW, and the Progression or Termination is also SLOW - High time consumption.
- - - - Heat Transfer through Evaporation
        Describe evaporation
        Evaporation is the loss of volatile liquids on the body surface.
        
        Describe how Heat is Transferred/Lost from the Body surface to the Environment through Evaporation
        Evaporation can occur from the skin, water vapour lungs, bowel etc.
        This occurs due to the latent heat of vaporisation.
        Evaporation accounts for 30% of heat loss (insensibly + sweating).
        
        What does Evaporation depend on ?
        Evaporation depends on Humidity.
        
        List ways to prevent heat loss through Evaporation
        
        Control of ambient temperature
        
        Humidification of gases
- - - - How does the body respond to ambient temperature ?
        The concept of Thermoneutral Range
        The Thermoneutral range is temperature range between two critical temperatures where the basal metabolic rate remains constant.
        
        In a thermoneutral environment the metabolic rate does not change, ONLY other reflexes such as Vasoconstriction or Vasodilation maintain heat, promote or prevent heat loss.
        The Basal metabolic rate changes ONLY in the extremes of the thermoneutral range either to cause more heat loss or heat conservation.
        Critical Temperatures: 27 - 31 degrees Celsius.
        NOTE: Certain diseases can alter the thermoneutral range.
        
        Temperature Regulation - Extremes of Age
        How do the extremes of Age affect the Temperature Regulation in Neonates
        Paediatric (neonates/infants) have:
        
        Functional immaturity status where they:
        
        Lack shivering (<3 months)
        Have NO behavioural thermo-conservation
        Have a higher Thermoneutral Zone
        
        Unique proportions such as
        
        Large surface area
        80% vs 65% body waterless
        Subcutaneous fat padding
        High skin permeability (preterm)
        
        Temperature Regulation - Extremes of Age
        How do the extremes of Age affect the Temperature Regulation in Elderly
        Elderly experience changes in:
        
        Thermogenesis
        
        Decrease in Basal Metabolic Rate and No non-shivering thermogenesis
        Decrease in muscle tone and onset or intensity of shivering.
        
        Thermosensation
        
        Skin receptor discrimination: 2 vs 1 degree Celsius in young due to gradual neuropathy or co-existing disease.
        
        Thermal transfer
        
        Atrophy of sweat glands
        Decreased cutaneous autonomic control (arterial -venous shunts fails)
        
        High Temperature and Fever
        What causes an INCREASE in Ambient Temperature ?
        Eg: Heatstroke
        
        Depends on relative humidity
        
        Shock and clotting disorder
        
        Shock dysfunction, early or late
        
        Medical emergency
        
        What causes an INCREASE in Core temperature
        Eg: Fever
        
        An infectious agent enters into the body, causing the release of Macrophages and T cells.
        
        Macrophages will phagocytose infectious agent
        
        Pyrogen release eg: IL-1
        
        Stimulation of Prostaglandins synthesis
        
        Prostaglandin E will then reset thermostat (TRIC)
        
        TRIC will respond to cold, resulting in an increase in heat production and a decrease in heat loss.
        
        Temperature Abnormalities
        What are the benefits of Artificial Hypothermia ?
        
        Protects tissue by decreasing the metabolic rate
        
        Decreases Brain, Heart metabolism by 50% or more - hence complex surgery is possible.
        
        What are the limitations in Hypothermia Benefits ?
        
        It is only effective for a short period
        
        Enzyme dysfunction can occur eg: coagulation
        
        Cell fragility
        
        Uneven cooling or re-warming