Regulation of Body Temperature - Lecture 6 Flashcards
What components of our bodies must be kept within narrow homoeostatic ranges? (5)
Pressures and volumes
Body Temperature
Concentration of nutrients e.g. glucose
Concentration of O2 and CO2
concentration of waste products e.g. urea
In terms of temperature control, how can the body be divided?
Core
Outer Shell
What is the outer shell composed of? (2)
Skin
Subcutaneous Tissue
How is the Core Temperature maintained?
By Homoeostasis - Involving a negative feedback system
What is a normal Core body temperature?
37.8°C
What happens to the Core Body temperature in environmental changes?
The Core Temperature is kept constant (37.8°C)
What is Normothermia?
The normal core body temperature (normothermia) is optimum for cellular metabolism and function
What does increased body temperature do?
Increase cellular metabolism
What does overheating of the body cause?
Protein denaturation
Nerve malfunction
Convulsions
Death
How can the Core Body Temperature be defined?
The temperature of structures deep within the body
What does decreased body temperature cause to the body?
Slows down the rate of cellular reactions.
What are the site for monitoring temperature?
Ear Drum (Tympanic)
Rectal
Oral
What is the range for temperature of the Tympanic site?
35.5°C - 37.5°C
What is the range for temperature of the Rectal site?
36.7°C - 37.5°C
What pattern does body temperature display?
Diurnal Variation
What point of the day is temperature at its lowest?
Morning
What must be equal for core body temperature to stay constant?
Heat gain and heat loss must be equal
How is heat gained from the internal environment?
Metabolic Heat
How is heat gained from the the external environment? (3)
Radiation
Convection
Conduction
How is heat lost to the external environment? (4)
Convection
Conduction
Radiation
Evaporation
How is Metabolic heat produced?
Oxidation of metabolic fuel derived from food in the body
What is the Basal Metabolic Rate (BMR)?
Minimum amount of energy required to sustain vital body functions
How can the BMR be increased? (3)
Hormones
Muscle Activity
Shivering
What leads to the basic level of Heat Production?
Basal Metabolic Rate (BMR)
What are the hormones that increase the BMR? (3)
Adrenaline
Noradrenaline
Thyroxine
What is Radiation of heat?
Emission of heat energy in the form of electromagnetic waves from a surface
- The body emits and absorbs radiant heat
What is conduction of heat?
Transfer of heat between objects in contact
Heat moves from warmer to cooler object
What does Conduction depend upon?
Heat conduction depends on temperature gradient and thermal conductivity
What is Convection of heat?
Transfer of heat energy by air (or water) currents that help to carry the heat away from the body
What two forms of heat transfer are combined to dissipate heat from the body?
Convection
Conduction
What is Evaporation of heat transfer?
Energy is required to convert water in the skin surface and the lining of the respiratory airways into vapour
energy comes from the body resulting in evaporative heat loss - cools the body
What is Passive Evaporative Heat Loss?
Water molecules continuously passively diffuse from the surface of the skin and the linings of the respiratory airways
What is Active Evaporative Heat Loss?
Sweating is an active evaporative heat loss process controlled by the sympathetic nervous system
What affects the amount of evaporation?
Relative Humidity
What is required a negative feedback system?
Sensor
Control Centre
Effectors
What are the sensors of the negative feedback system for Temperature Control? (2)
Central thermoreceptors (in hypothalmus, abdominal organs, elsewhere) Peripheral thermoreceptors (in skin)
What the control centre of the negative feedback system for Temperature Control?
Hypothalamus
What are the effectors of the negative feedback system for Temperature Control? (2)
Skeletal Muscles
Skin Arterioles
Sweat Glands
Where are the negative feedback receptors for temperature regulation located on the Hypothalamus?
The Neural Inputs of the Hpothalamus
What part of the Hypothalamus is activated by cold?
The Posterior Hypothalamic Centre
What part of the Hypothalamus is activated by warmth?
The Anterior Hypothalamic Centre
What systems does the Hypothalamus have connections with?
Limbic System
Cerebral Cortex
Motor Neurones - control skeletal muscles
Sympathetic Nervous System
What is the response of the Skin Arterioles when exposed to cold?
Vasoconstriction - Decreases heat loss
What is the response of the Skeletal Muscle when exposed to cold? (3)
Increased muscle tone
Shivering
Increased voluntary movement
What is the response of the Skin Arterioles when exposed to Heat?
Vasodilation - Increased Heat Loss
What is the response of the Sweat Glands when exposed to Heat?
Sweating - Evaporation of sweat
Increased Heat Loss
What is the response of the Skeletal Muscle when exposed to Heat? (3)
Decreased muscle tone
Decreased voluntary
Movement
Decreased heat Production
What is an endogenous pyrogen?
Stimulate the release of prostaglandins in the hypothalamus
What is the function of a Postaglandin?
prostaglandins act on the hypothalamic thermo-regulatory centre to “reset” the thermostat at a higher temperature
What action does the Hypothalamus carry out when prostaglandins act on the it?
Hypothalamus initiate mechanisms to heat the body “cold response” to raise the body temperature to the new higher temperature, resulting in Fever
How is the Hypothalamic temperature set point raised? (6)
- Infection causes Macrophages to release chemical to produce endogenous pyrogen
Release of Postaglandins
Hypothalamic set point increased
Initiation of cold response
Heat Production increase - heat loss decreased
Increased Body Temperature
What temperature is the new set point for a fever?
38°C - 40°C
What is hyperthermia?
Extreme uncontrolled increase in body temperature
Temperature above 40°C
What is hypothermia ?
Drop in body temperature below that required for cellular metabolism
Temperature at or below 35°C
