Feedback Control: Temperature and Other Vital Signs

Question 1

What is Pulse?

Answer 1

Pulse - heart rate (adults normal resting HR 60-100 beats/min), rhythm, volume, character

Question 2

What is normal Respiratory Rate?

Answer 2

Respiratory Rate – adults normal resting RR 12-20 breaths/min)

Question 3

What is normal Oxygen Saturation?

Answer 3

normal ≥96%.

Question 4

What is normal Capillary Refill time?

Answer 4

<2 seconds

Question 5

What is Core Body Temperature?

Answer 5

• The temperature of the structures deep within the body
• Homeostatically maintained at about 37.8 ℃
• Human body can be thought of of a core and outer shell - the outer shell consists of skin and subcutaneous tissue.

Question 6

What is Normothermia?

what alters it?

Answer 6

• 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

Question 7

How to Indirectly estimate core body temperature?

Answer 7

Ear Drum (tympanic themometer): normal range about 36oC-37.5oC:

Question 8

How to directly estimate core body temperature?

Answer 8

Rectal or Oesophageal: Slightly higher than tympanic temperature

Question 9

What temperature range is considered hyperthermia?

Answer 9

above 40oC

Question 10

What temperature range is considered abnormally high/fever?

Answer 10

38-40oC

Question 11

What temperature range is considered hypothermia?

Answer 11

below 35oC

Question 12

How is heat lost/ gained from the external environment?

Answer 12

Radiation
Conduction
Convection
Evaporation

Question 13

Describe Radiation Heat Loss

Answer 13

• emission of heat energy as electromagnetic waves
• ½ of total body heat loss

Question 14

Describe conduction heat loss

Answer 14

• transfer of heat between objects in contact (warmer → cooler)
  
  • Depends on temperature gradient and thermal conductivity
  • Combines with convection

Question 15

Describe Convection Heat Loss

Answer 15

• 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

Question 16

Describe Evaporation Heat Loss

Answer 16

• 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

Question 17

How is heat gained from the internal environment?

Answer 17

Metabolic heat

Question 18

Describe Metabolic Heat Gain

Answer 18

• Basal Metabolic Rate: basic level of heat production
• Can be increased by hormones
• Muscle activity - shivering

Question 19

How does Maintenance of core body temperature work?

Thermoregulation

Answer 19

1. Sensor detects change - central thermoreceptors, peripheral thermoreceptors (skin)
2. Sends signal to hypothalamus (control centre)
3. Effectors (e.g. skeletal muscles, skin arterioles, sweat glands) triggered to respond and restore variable to normal

Question 20

What is the Hypothalamus?

Answer 20

• 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

Question 21

Which Hypothalamic Centre is activated by warmth and how?

Answer 21

anterior

Question 22

Which Hypothalamic Centre is activated by cold and how?

Answer 22

posterior