1 Flashcards
What refers to tissue damage associated with excessive cooling of the skin and the underlying tissue?
And what occurs in more extreme cases of the said term?
- Frostbite
- In the more extreme cases, cellular death takes place due to ice crystal formation or a lack of liquid water
What is a prolonged decrease in body temperature below the normal range and beyond the body’s ability to compensate?
- Hypothermia
What is an increase in body temperature that results from an immune response to infection or inflammation and involves the release of endogenous pyrogens from macrophages?
And, what is its mechanism of action?
- Fever
- These endogenous pyrogens are responsible for changing the set point of the hypothalamus, initiating a “cold response.” Thus, in a fever, the hypothalamus initiates compensatory mechanisms that increase the internal body temperature to match the altered set point.
What is a more dangerous condition that results from a breakdown of the thermoregulatory ability of the hypothalamus, such that body temperature increases in the absence of the normal compensatory mechanisms?
- Heat stroke
What involves a drop in BP and results from overactivity of the body’s heat loss mechanisms, such that body temperature increases despite the normal compensatory mechanisms, such as sweating and vasodilation?
- Heat exhaustion
What is a prolonged increase in body temperature above the normal range and beyond the body’s ability to compensate?
What may it result from physiologically & pathologically?
And, does it include fever?
- Hyperthermia
- May result physiologically from exercise or pathophysiologically from abnormalities associated with the hypothalamus or metabolic rate
- It doesn’t include fever
What occurs to heat production and heat loss mechanisms in response to heat exposure (coordinated by the anterior hypothalamus)?
- Decreased Heat Production: Such as, decreased muscle tone & decreased voluntary exercise
- Increased Heat loss (Heat Conservation): Such as, skin vasodilation, sweating, & cool clothing
What occurs to heat production and heat loss mechanism in response to cold exposure (coordinated by the posterior hypothalamus)?
- Increased heat production: Such as, increased muscle tone, shivering, increased voluntary exercise, & nonshivering thermogenesis
- Decreased heat loss (Heat Conservation) – Such as, skin vasoconstriction, postural changes to reduce exposed surface area (e.g., hunching shoulders etc.), & warm clothing
The coordinated adjustments to both heat production and heat loss occur in response to…
- Occur in response to decreases and increases in internal core temperature
What occurs to the thermal information after it is detected by peripheral & central thermoreceptors?
- This thermal information is integrated & compared to a set point in the hypothalamus
- Which then relays this efferent information to the effectors in response to deviations from the set point
Which two thermoreceptors are thermal information detected by?
And what are their locations?
- By central thermoreceptors located in the hypothalamus, CNS, & abdominal organs
- By peripheral thermoreceptors located in the skin
What does the anterior hypothalamus coordinate the response to?
- To increases in body temperature
What does the posterior hypothalamus coordinate the response to?
- To decreases in body temperature
What is the strucutre called that homeostatically regulates body temperature?
- The hypothalamus
What is the loss of the heat required to transform a liquid into a gas?
And, how does it occur in humans (passively & actively)?
- Evaporation
- It occurs in humans both passively (through respiration & from skin surfaces) and actively (through sweating).
What is the transfer of heat energy by air or water currents?
- Convection
What is the transfer of heat between objects in physical contact with each other?
- Conduction
What is the emission of heat as electromagnetic (heat) waves?
And, how does it relate to humans?
- Radiation, also humans emit & absorb radiant energy.
List the 4 mechanism by which heat exchange occurs
- Radiation, conduction, convection, & evaporation
Which 2 factors can be regulated to maintain body temperature?
And, how is a decrease in internal core temperature counteracted?
- Heat input & output
- Counteracted by increasing the internal heat production & minimizing heat loss
What are the sources of heat output from the body? Or how does heat output occur from the body?
- Occurs through heat loss from exposed body surfaces to the external environment
What are the sources of heat input into the body?
- Can originate from the external environment or from internal heat production
What needs to occur for the internal core temperature to be maintained at a given level?
- Heat input into the body must equal heat output from the body
What does the temperature of the outer shell consist of? And how does it differ from the internal core temperature?
- It consists of the skin & the subcutaneous fat of the body
- It is much more variable than the internal core temperature
List the 4 possible factors responsible for the variation in the internal core temperature
- The innate biological rhythm
- Female reproductive menstrual cycle
- Exercise
- Exposure to extremes of temperature
Which regions of the body does the internal core include?
How is it maintained?
And, what is its normal set point about?
- Includes: the abdominal & thoracic organs, CNS, & skeletal muscles
- It is precisely maintained within a narrow range around the normal set point of about 37.8 °C
What does the variation of body temperature depend on?
- Depending on the region of the body
Are decreases or increases in body temperature better tolerated?
- Decreases in body temperature are better tolerated than increases in body temperature.
What is the result of decreases in body temperature?
hint: Speed of chemical reactions…
- Resulting in a decrease in the speed of chemical reactions in the body & in the metabolic rate of the body.
What is the result of increases in body temperature? And, what is the upper limit of body temperature compatible with life?
(hint: Speed of chemical reactions…)
- Resulting in an increase in the speed of chemical reactions in the body & in irreversible protein denaturation, both of which particularly affect the functioning of the nervous system
- 43.3 °C
Why must body temperature be homestatically regulated?
- Because deviations from the normal range interfere with cellular processes
What is included in energy output and is vital in the maintenance of body temperature?
- The production of thermal energy
What is the result of chronic states of negative energy balance?
- Will result in nutritional deficiencies
What is the result of chronic states of positive energy balance?
- Will result in obesity
What does the regulation of food intake have implications for?
- Has important implications for energy balance
What do the psychological and environmental factors include for the regulation of food intake? For example…
List all 6 factors
- Habits
- Social factors
- Taste
- Pleasure derived from food & the eating experience
- Mental status
- Availability of food
In addition to long-&short- term regulatory factors, what other factors play a key role in the regulation of food intake?
- Psychological & environmental factors
How are peptide YY (PYY3-36) & cholecystokinin (CCK) different from Ghrelin?
What is the mechanism of action of both secretants? (What do they inhibit and stimulate)
- In contrast to ghrelin, both are intestinal secretions that serve as satiety signals
- PYY3-36: Inhibits hypothalamic Neuropeptide Y (NPY)-secreting neurons
- CCK: Stimulates the nucleus tractus solitarius (NTS) of the brain stem.
Why is Ghrelin known as the “hunger hormone”? Where and why is ghrelin secreted? And, what is its mechanism of action?
- Known as such due to its role as an appetite stimulator
- Secreted from the stomach prior to a meal
- Mechanism of action: It stimulates the neuropeptide Y-secreting neurons of the hypothalamus
What are the 3 hormones called that play an important role in the short-term regulation of food intake?
- Ghrelin, peptide YY (PYY3-36), and cholecystokinin (CCK)
What is the structure that secretes Insulin called?
Insulin is secreted in response to…
And what is its mechanism of action (it inhibits…)?
- Secreted by the pancreas
- Secreted in response to increased levels of nutrients (glucose, amino acids, & fatty acids) in the plasma
- Acts to inhibit Neuropeptide Y (NPY)-secreting neurons of the hypothalamus
What is the structure that secretes leptin called, & what is it referred to as?
What does the plasma concentration of leptin correlate to?
What is the function of leptin?
And what is the mechanism of action of leptin in inhibition & stimulation?
- Secreted by adipocytes, is referred to as an adipokine
- The plasma concentration of leptin correlates with the amount of triglyceride stored in adipose tissue
- Function: To decrease appetite & food intake
- Mechanism of action: Exerts its actions by inhibiting Neuropeptide Y (NPY)-secreting neurons & stimulating melanocortin-secreting neurons
What are the 2 hormones called that play an important role in the long-term regulation of food intake?
- Leptin & insulin
What is the region of the brain called that serves as a satiety centre to decrease appetite & food intake?
- The nucleus tractus solitarius (NTS) of the brain stem
What does the paraventricular hypothalamic nucleus (PVN) secrete?
And, what does the secretion do?
- Secretes neuropeptides, which decrease appetite & food intake
What does the lateral hypothalamic area (LHA) secrete? And, what does the secretion do?
- Secretes orexins, which increase appetite & food intake
Where do both the NPY- & the melanocortin-secreting neurons project?
- They project to the lateral hypothalamic area (LHA) & the paraventricular hypothalamic nucleus (PVN).
Within the arcuate nucleus of the hypothalamus, what are the 2 structures called that increase & decrease appetite & food intake?
And, what do they secrete as a result?
- The Neuropeptide Y (NPY)-secreting neurons release Neuropeptide Y (NPY), which acts to increase appetite & food intake,
- The melanocortin-secreting neurons release melanocortins, which act to decrease appetite & food intake.
Which 2 brain regions are primarily responsible for the regulation of food intake?
- The hypothalamus & the brain stem
Which 2 brain regions are primarily responsible for the regulation of food intake?
- The hypothalamus & the brain stem
Which body systems are involved in the regulation of food intake?
- Endocrine & nervous systems
Describe a negative energy balance. How does it reflect changes in body weight?
- Exists when energy input is less than energy output
- In negative energy balance = body weight decreases.
Describe a positive energy balance. How does it reflect changes in body weight?
- Exists when energy input is greater than energy output
- In positive energy balance, body weight increases.
Describe a neutral energy balance. How does it reflect changes in body weight?
- Exists when energy input equals energy output
- In neutral energy balance, body weight remains constant.
List the different classifications of energy balance. & what is energy balance reflected in?
- Can be classified as neutral, positive, or negative
- Energy balance is reflected in changes in body weight
What is the minimal waking rate of internal energy expenditure?
How is it regulated?
- Basal metabolic rate (BMR)
- BMR is regulated by the thyroid hormones
What is the rate of energy expenditure?
- Metabolic rate
How does energy output occur?
- Occurs through work & the production of heat or thermal energy.
How does energy input occur?
- Occurs in the form of nutrient ingestion
How is energy balance achieved?
- Energy input into the body must equal energy output or expenditure from the body.
What does the 1st law of thermodynamics state?
- States that energy cannot be created or destroyed
