Feedback Control: Temperature and Other Vital Signs Flashcards
(23 cards)
What is Pulse?
Pulse - heart rate (adults normal resting HR 60-100 beats/min), rhythm, volume, character
What is normal Respiratory Rate?
Respiratory Rate – adults normal resting RR 12-20 breaths/min)
What is normal Oxygen Saturation?
normal ≥96%.
What is normal Capillary Refill time?
<2 seconds
What is Core Body Temperature?
- The temperature of the structures deep within the body
- Human body can be thought of of a core and outer shell - the outer shell consists of skin and subcutaneous tissue.
What is Normothermia?
what alters it?
- Optimum temperature for cellular metabolism and function
- Shows diurnal variation (lowest temperature in early morning)
- Altered by activity, emotions, exercise, exposure
- Varies during menstrual cycle
- Differs sightly between individuals
How to Indirectly estimate core body temperature?
Ear Drum (tympanic themometer): normal range about 36oC-37.5oC:
How to directly estimate core body temperature?
Rectal or Oesophageal: Slightly higher than tympanic temperature
What temperature range is considered hyperthermia?
above 40oC
What temperature range is considered abnormally high/fever?
38-40oC
What temperature range is considered hypothermia?
below 35oC
How is heat lost/ gained from the external environment?
Radiation
Conduction
Convection
Evaporation
Describe Radiation Heat Loss
- emission of heat energy as electromagnetic waves
Electromagnetic waves travel through the space and transformed into heat on striking another surface
The human body both emits and absorbs radiant heat - ½ of total body heat loss
Describe conduction heat loss
- transfer of heat between objects in contact (warmer → cooler)
- Depends on temperature gradient and thermal conductivity
- Combines with convection
Describe Convection Heat Loss
- air next to skin warmed by conduction,
- warmed air is less dense and will rise
- while cooler air moves next to the skin
- Forced air movement across the body surface (wind) increases the combined effect of conduction-convection
Describe Evaporation Heat Loss
- heat energy to convert water in skin to vapour
Passive: water passively diffuses from the surface of the skin and the linings of the respiratory airways
Active: sweating controlled by Sympathetic Nervous System
How is heat gained from the internal environment?
Metabolic heat
Describe Metabolic Heat Gain
- Basal Metabolic Rate: basic level of heat production
- Can be increased by hormones
- Muscle activity - shivering
How does Maintenance of core body temperature work?
Thermoregulation
- Sensor detects change - central thermoreceptors, peripheral thermoreceptors (skin)
- Sends signal to hypothalamus (control centre)
- Effectors (e.g. skeletal muscles, skin arterioles, sweat glands) triggered to respond and restore variable to normal
What is the Hypothalamus?
- The Temperature Control
Centre- acts as the body’s thermostat - Has a variety of neural and hormonal inputs and outputs
- Posterior and Anterior control centres activated seperately by cold and warmth (respectively)
- Neural connections with the limbic system and cerebral cortex, the motor neurons which control skeletal muscles and the sympathetic nervous system
Which Hypothalamic Centre is activated by warmth and how?
anterior
Which Hypothalamic Centre is activated by cold and how?
posterior
how is the Hypothalamic Temperature Set
Point Raised in “Fever”
-Chemicals released from macrophages in response to infection or inflammation act as an endogenous pyrogen (IL 1, 6) stimulate the release of prostaglandins in the hypothalamus
-The prostaglandins act on the hypothalamic thermo-regulatory centre to “reset” the thermostat at a higher temperature
-“cold response” (e.g. shivering and skin vasoconstriction) to raise the body temperature to the new set point
-can be restored by reducing pyrogen release/ prostaglandins
