Homeostatis Flashcards
What is homeostatis?
Homeostasis is the body’s way of keeping everything in balance, like a thermostat that regulates temperature
- The motivaton to maintain optimal conditions for the body such as water, sodium, other nutrients and temperature
What are the three mechanisms of homeostatis?
- A set point - so what a normal temp is for you
- A detection mechanism - when it has deviated from set point
- Behaviour - to do soemthing about it
Example of how homeostatis acts
The thermostat acts to keep room temperature a certain point
What is the function of energy balance?
We eat to obtain energy to fuel and grow our bodies, ensuring a continuous supply of metabolic fuels
What are the evolutionary effects?
- Energy requirements fluctuate throughout the day and seasonally
- Fat storage can provide benefits for survival during food shortages
What is the control of energy balanced influenced by?
Experience, habits, and availability
What does the metabolism do?
It is described as the process of breaking down food into energy
- Excess energy after a meal is stored as glycogen in the liver and muscles or as fatty acids in cells
How much of a mammals body weight is water?
2/3
Tell me the distribution of water in blood plasma, inside cells, and intersital fluid.
67% inside cells
7% blood plasma
26% Interstitial fluid
What is osmotic thirst?
Where the body requires water from sodium intake
Does the body have surplus water?
No, so physiology and behaviour regulates water supply
How does osmotic thirst work?
(Fitzsimons., 1998)
The motivation to seek and injest water.
1. Sodium intake -> water is attracted to salt
2. Sodium is extracellular fluid -> Takes from inside the cell
3. Thirst arises wehn limited water inside of the cell
How does the body release osmotic thirst?
(Guaer & Henry., 1963)
- Body is thirsty -> Osmorereceptor cells detect this thirst. This signal is sent to hypothalamus to release vassopressin
- Vassopressin reaches the pituitary gland, releases ADH (anti diacretic hormone)
- ADH is released into the bloodstream, changing the function of the kidneys
- Kidneys stop filtering out water as normal
When is ADH reduced?
When water content reaches normal levels
What happens when storing food?
- Food is broken down into amino acids, fats, and glucose
- excess energy is left to be stored
Amino acids - muscle cells
Glucose - muscles fat cells
- Insulin released from Pancras to store glucose as glycogen in liver and muscle cells
What happens when energy is released?
- Energy is needed
- Brain looks for glucose
- Pancreas releases glycagon to break down molecules stored
- Glucose enter bloodstream to provide body with energy
What is hypovolemic thirst?
Thirst that occurs when vomit/diarrhea
What happens in hypovolemic thirst?
- Water, sodium, and nutrients are lost
- ADH is released by constricting blood vessels
LOSS OF BLOOD VOLUME: low blood pressure = kidneys dont function properly
- ADH restricts blood vessels to increase blood pressure -> kidneys work to retain water
Followed by:
- To balance sodium content in fluids which were lost
Kidneys also release angiotensin II, which also restricts blood vessels; it leads to the release of aldosterone from the adrenal glands, which decreases the amount of sodium excreted in urine, thereby helping to restore balance
What do we do behaviourally when we have hypovolemic thirst?
Eat and drink
What do endocrine regulators do?
These regulators control the release of hormones, ensuring that the right amount is produced at the right time to keep the body’s systems in balanc
What are the three endocrine regulators?
- Leptin
- Ghrelin
- CKK (Cholecystokinin)
What is leptin?
(Hayes et al., 2009)
- Released from fat cells
- Purpose is to provide feeling of fullness
- More fat cells = more leptin
What is Gherlin?
(Wren et al., 2001)
- Produced and released in the stomach
- Signals hunger to the body -> starvation hormone, serves purpose of feeling full
- Gherlin and leptin are inversly correlated
Study - Wren et al., 2001
- Injected rats with gherlin, had increased body mass and food intake
What is CKK?
(Morley et al., 1985)
- Found in small intestine
- Primary hormonal factor which provides a feeling of satiety (feeling satisfied)
- Released during eating
Works by:
- CKK binds to receptors on the VAGUS nerve
- This signals to the hypothalamus that fat and protien have been injested
- Blood levels do not vary much in CKK. However local levels around vagus nerve do.
Study (Morley et al., 1985)
- Hungry animals administered with CKK, food intake decreases
