Homeostasis and Behaviour Flashcards
What is homeostasis?
The constancy of the internal environment
Five chemical parameters for homeostasis
- Temperature
- Fluid balance
- Blood glucose
- Blood pressure
- Blood O2/CO2
Four homeostasis for external conditions
- Water availability
- Food availability
- Air temperature
- Oxygen availability
What does fluid balance do?
Aims to maintain composition and temperature of extra cellular fluid (ECF) at a constant level- in particular, water and sodium
Fluid balance- water
Cells need water for virtually all metabolic processes and as solvent for ions
Water is essential for functioning of the nervous system and other physiological processes
Water is continuously lost through perspiration, respiration, urination and defecation so it must be replaced
Very little extra water is stored in the body
Water and thirst
Water can pass freely through semi-permeable biological membranes
Elf has 2 primary constituents: fluid component (plasma) and interstitial fluids (contains dissolved solutes and proteins)
What is osmosis?
Water moves across biological membranes to the compartment with a higher solute concentration
What is osmolality?
The concentration of solutes in a solution
What is osmoregulation?
The control of osmolality
What is hypovolemic thirst? ‘
Reduction of blood volume (e.g. by perspiration)
Water, salts and other solutes are lost without necessarily pulling water out of the cell
Hypovolemia and kidney function
Reduces blood volume and resulting low blood pressure prevent the kidneys from extracting water effectively
2 types of stimuli provoke the release of ADH from the posterior pituitary
- Intracellular dehydration of cerebral osmoreceptors (during osmotic thirst)
- Reduction of blood plasma volume (during hypovolemic thirst)
Intracellular dehydration of cerebral osmoregulation
All cells drink in size as water moves into the interstitial space - but when this occurs in cerebral osmoreceptors, they signal the paraventricular nuclei and supraoptic nuclei of the hypothalamus
Reduction of blood plasma volume
A loss of blood volume is detected by stretch receptors in walls of cardiac blood vessels.
These receptors signal the PVN and SON to release ADH - which acts as a vasoconstrictorto increase blood pressure
What part of the body is responsible for the thirst response?
Brain - Latina terminalis
Energy balance- why do animals eat?
They need to meet the needs of the structural part of the body, for example to make bone or muscle, and to obtain energy to fuel cellular processes
What are the three complex interactions of energy balance?
- Hormones
- Neurotransmitters
- Neuromodulators
These change as an animals fluctuate between a well fed and fasting state
Two phases of energy use and storage during a well fed state
- Postprandial phase
- Post absorptive stage
What is the postprandial phase?
It occurs immediately after eating, were the supply of metabolic fuels enter the bloodstream.
What is the postabsorptive phase?
It’s a storage of energy access
Insulin secretion stimulate the conversion of glucose to glycogen in the liver to store in the liver and muscles
Insulin is the sole hormone responsible for energy storage invertebrates
What happens in a state of fasting?
The influx of energy from the no longer exceeds the body, energy usage requirements
Glucose is a primary feel used by the central nervous system, and during the fasting state glucose is preferred by the brain most of the cells switch to metabolic fatty acids such as lipids to make ATP
What is a glycogenesis during a fasting state?
The breakdown of glycogen in the liver
What is lipolysis during the fasting state?
Breakdown of triglycerides, stored in the adipose tissue into free fatty acids and glycerol
What happens to glucagon during the fasting stage?
Glucagon is released from the pancreas, while secretion of insulin is inhibited- glucagon introduces both these processes
