energy metabolism and body temperature
DESCRIPTION
Energy metabolism and body temperature. Outline of the lecture. Section 1 Energy Metabolism 1. Energy storage, liberation, transfer and utilization 2. Energy balance 3. Metabolic rate Section 2 Body Temperature 1. Body temperature 2. Balance between heat production and heat loss - PowerPoint PPT PresentationTRANSCRIPT
Energy metabolism and body Energy metabolism and body temperaturetemperature
Outline of the lectureOutline of the lectureSection 1 Energy Metabolism1. Energy storage, liberation, transfer and
utilization
2. Energy balance
3. Metabolic rate
Section 2 Body Temperature1. Body temperature
2. Balance between heat production and heat loss
3. Regulation of the body temperature
materialsynthesis
materialbreakdown
releaseenergy
requireenergy
materialmetabolism
energy metabolism
Metabolism
Anabolism Catabolism
Energy storage, liberation, transfer and utilization
Energy balance
Energy input = energy output
heatFood heat heat ATP cellular functions heat
metabolismFood heat
metabolic ratemetabolic rate
amount of energy liberated from a living organism per unit of time
expressed in terms of the rate of heat liberation during the chemical reactions
Metabolic rateMetabolic rate
Measurement of the metabolic rateDirect calorimetryIndirect calorimetry Caloric value / thermal equivalent of food Oxygen consumption / thermal equivalent of
oxygen ( 1 L ) Respiratory quotient ( CO2 / O2 )
Factors that affect the metabolic rateFactors that affect the metabolic rate1. Exercise Exercise produces an increase in metabolic rate2. Ingestion of food Increase metabolic rate The specific dynamic action of protein3. Emotional state4. Environmental temperature 20-30 °C have stable metabolic rate < 20 or >30°C , metabolic rate is increased5. Other factors (sleep, sex, etc.)
Basal Metabolic Rate (BMR)Basal Metabolic Rate (BMR)
Metabolic rate during basal conditionsMinimum level of energy required for lifeUseful for diagnosing the diseases:
– Hyperthyroidism, hypothyroidism
Basal conditionsBasal conditions
must not have eaten food for at least 12 hours after a night of restful sleep no strenuous activity is performed for at least 1
hour before the test all psychic factors that cause excitement must be
eliminated the temperature of the air must be comfortable and
between 25 – 30 °C no physical activity is permitted during the test
Section 2 Body temperatureSection 2 Body temperature
Skin temperature– temperature of the skin and tissues immediately underlying the
skin. – rises and falls with the temperature of the surroundings
Core temperature – the temperature of the deep tissues of the body – the “core” of
the body.
– remains almost exactly constant, varying not more than 1 ℃ – Rectal T: 36.9-37.9 ℃ – Oral T: 36.7-37.7 ℃ – Axillary T: 36.0-37.4 ℃
Range of body temperatureRange of body temperature
Factors affecting normal temperatureFactors affecting normal temperature
1. Circadian rhythm
In the early morning, the body T is the lowest.
In late afternoon or early evening, it is the highest.
2. Age
Newborn child > adult > old person
3. Sex
Women > man 0.3 °C
4. Muscular activity
Increase T
5. Other factors: emotion, eating, change in climate
Balancing between heat production Balancing between heat production and heat lossand heat loss
1. Heat production– (1) BMR of all the cells– (2) Extra metabolism caused by
muscle activity the the effect of hormone (thyroxine, growth hormone and
testosterone) the effect of epinephrine, norepinephrine and sympathetic
stimulation on the cells increased chemical activity in the cells themselves
2. Heat loss• The major organ to loss heat is the skin• Blood flow to the skin from the body core provides heat transfer
Methods of heat loss from the skin to the surroundings
• Evaporation• 1) Insensible perspiration
• 2) SweatingA. Innervation of the sweat gland
• Mainly sympathetic
cholinergic
• nerve (acetylcholine)
• Caused by nervous reflex
B. Mechanism of sweat secretion Primary secretion reabsorption Sweat (urea, lactic acid, K+ )
Regulation of the body temperatureRegulation of the body temperature
1. Behavioral control of the body temperature
For example: In freezing weather, we can move into a heated room
2. Autonomic control of the body temperature
The temperature of the body is regulated almost entirely by nervous feedback mechanism through temperature regulating centers located in the hypothalamus.
Feedback mechanisms of regulation Feedback mechanisms of regulation of the body temperatureof the body temperature
1. Temperature receptor– 1) Peripheral temperature receptor
A. Locations: skin, mucous, abdominal viscera B. Types: cold receptor and warmth receptor cold receptor > warmth receptor
– 2) Central temperature receptor A. Locations: spinal cord, preoptic and anterior
hypothalamic area of the hypothalamus (PO/AH) B. Types: heat-sensitive neurons and cold-sensitive
neurons
2. Temperature-regulating center– 1) The thermoregulating center is mainly in the
hypothalamus– 2) The PO/AH area is the basic thermostatic
temperature controlling center
3. Efferent pathways: Control of the heat loss and heat production– 1) Control of the skin vascular tone and
sweating by sympathetic nerve system– 2) Changes of the muscular tension by somatic
motor nerve system– 3) Control of the metabolic rate by altering the
function of endocrine system, mainly the hormone secretion of the thyroid glands or adrenal medulla
“Set-point”
37 °C
PO/AH area
T > 37 °C
Production < loss
T < 37 °C
Production > loss
Fever
SummarySummary
Metabolism Metabolic rate heat body temperature BMR Heat production “set-point” PO/AH Heat loss