10b. Homeostasis Flashcards
What is homeostasis?
The maintenance of stable conditions in the internal environment
What are some external environmental challenges?
- Microparticles
- traffic fumes
- Industrial fumes
- Microorganisms
- External temperature
What are some internal environmental challenges?
- Exercise
- metabolic reactions and heat production
- quality of foods and liquids ingested, levels of nutrients, effects on BP urinary output etc
What does the regulatory system consist of?
Nervous and endocrine system
What is the set point?
A point chosen by the system as the most stable point for maintaining homeostasis
What is negative feedback?
Tells the regulatory system to reduce or reverse a process
What is positive feedback?
Tells the regulatory system to amplify or increase a response beyond the set point
What are endotherms?
They regulate body temperature by producing heat or active mechanisms of heat loss (mouse, human , horse)
What are ectotherms
Animals whose body temperatures are determined mainly by external sources of heat
How is heat generated in the body?
Metabolism
How is head released from the body?
Evaporation
How does blood flow reduce body heat?
Blood flow to skin is another way to reduce body heat. Heat from the body bia blood to skin is lost to the environment
How is body heat generated?
All energy reactions in the body are inefficient and produce heat as a by product
What is the basal metabolic rate?
BMR of an endotherm is the lowest metabolic rate necessary for biochemical and physiological processes f a resting animal
What is hypothesis
Heating or cooling the hypothalamus will result in predictable changes to body temperature
What does the hypothalamus do when body temperature is below normal?
- Heat produciton
- Blood vessels constrict
- Skeletal muscles contract
- Shivering
What does the hypothalamus do when body temperature is above normal?
- Heat loss
- Blood vessels dilate
- Skeletal muscles relax
- Panting, sweating
What does heat stress equate to?
The sum of heat generated in the body (metabolic heat) plus heat gained from the environment (environmental heat) minus heat lost from the body to the environment.
What are the 4 climatic factors that determine the body’s heat balance?
- Air temperature
- Radiant temperature
- Humidity
- Air movement
What are the 2 non climatic factors that determine the body’s heat balance?
Clothing and the metabolic heat produced at rest or during physical activities
How does heat dissipation occur?
through dry heat loss (radiation and convection) and evaporative heat loss (sweating)
What are the 3 progressively worse steps in heat stress?
Heat cramps, heat exhaustion, heat stroke
What happens in heat cramps?
- Exercise associated cramps
- Due to dehydration and loss of sodium via sweating
- Painful muscle spasms
What happens in heat exhaustion?
- Symptoms are nausea, vomiting, weakness, headache, fainting, sweating and cold skin
- If left untreated, heat exhaustion can lead to heatstroke
What happens in heat stroke?
Life threatening condition requiring immediate medical attention
Symptoms include confusion, irritability, headache, dizziness, fainting, nausea, vomiting, visual problems, fatigue and seizures and failure of major organs or even death in 20% of cases
Why does heat stress cause failure of organs or death?
Hyperthermia leads to improper function of proteins and cell membranes and can ultimately lead to cell death (enzymes cannot bind to substrate causing denaturation)
What is hypothermia?
A below normal body temperature due to starvation, exposure to extreme cold, serious illness, anaesthesia
-Drop in temperature is unregulated
What is hibernation
Regulated hypothermia - adaptation in animals to scare food or periods of cold
-regulated drop in body temperature
What is a heterotherm?
An animal that regulates its body temperature at a constant level sometimes but not others, such as a hibernator.
