Homeostasis Flashcards
Homeostasis
The maintenance of a stable, balanced internal environment
Set point
The optimized, desired value in a feedback system
Set zone
The optimal range of tolerance in a feedback system
Negative feedback
As a system deviates from a set point, the body reduces its activity, allowing for precise control over an internal environment
Allostasis
The dynamic regulation of set points depending on specific conditions in the environment (ex: fever)
Endotherms
Organisms that generate their own heat energy mainly through metabolism
Exotherms
Organisms that get most body heat from the external environment
Where are receptors for thermoregulation?
Skin’s surface, body core, pre optic area
Which nuclei of the hypothalamus are involved for behavioral and physiological responses?
Medial and lateral nuclei
What are behavioral responses to thermoregulation?
Shivering (muscle activity generates heat), Heat seeking/ avoiding behaviors
What are physiological responses to thermoregulation?
Constriction/ dilation of blood vessels (increase in surface area allows more heat to dissipate)
Sweating (evaporation cools)
Respiration (blow out hot air)
Thyroid hormone secretes (generates heat by metabolism)
Goosebumps (hairs stand to retain heat)
Diffusion
Molecules of a solute dissolved in a solvent will move from high to low concentrated areas until a uniform concentration is achieved
Osmosis
Passive movement of solvent (water) through a semipermeable membrane between solutions of different solute concentrations (low to high) until both sides become equal
Osmotic pressure
The force that pushes or pulls water across the membrane
Hypovolemic thirst receptors, signal, behavior, response
Baroreceptors in major blood vessels
Pressure drop from fluid loss (solutes and solvents)
Inhibits drinking
Slow urine production, blood vessels constrict, increase blood pressure
Osmotic thirst receptors, signal, behavior, response
Osmosensory neurons in the brain
Increased saltiness of extracellular fluid
Eat salty foods
Pulls water out of intercellular compartment
Osmotic thirst system
- Extracellular fluid is too salty
- Water is drawn out of cells by osmosis
- Loss of intracellular water/ increased salt detected by osmosensory neurons
- Induces thirst, dry mouth
- Stimulates hypothalamic thirst network to increase drinking
- Vasopressin is released from pituitary to slow urine production and constrict blood vessels to preserve blood volume
- Aldosterone is released from adrenal glands to stimulate Na absorption and slow the loss of water
Hypovolemic thirst
- Low extracellular volume from body fluid loss stimulates loss of blood volume
- Baroreceptors detect blood pressure drop and signals an inability to perfuse organ tissue
- The brain activates thirst and salt hunger
- The SNS causes arteries to constrict to maintain blood pressure
- Heart decreases secretion go atrial natriuretic peptide to increase blood pressure
- Pituitary gland increases vasopressin release to constrict blood vessels
- Kidneys produce angiotensin II to constrict blood vessels and aldosterone to increase Na absorption
Digestive system
- Chewing breaks up food and mixes it with saliva
- Saliva lubricates food and begins digesting from enzymes in saliva
- Swallowing moves food down the esophagus to the stomach
- The stomach acts as a storage container and hydrochloric acid in the stomach breaks down food into small particles while pepsin breaks down protein molecules into amino acids
- The stomach gradually empties its contents through the pyloric sphincter into the duodenum of the small intestine
- Most absorption takes place in the small intestine where digestive enzymes from the pancreas and gallbladder break down protein molecules into amino acids and digestive enzymes break down starch and complex sugar molecules into simple sugars
- Fats are emulsified (broken down) by bile made in the liver and stored in the gallbladder until it’s released in the duodenum
- Most remaining water and electrolytes are absorbed from the waste in the colon and the remainder is ejected
How does the brain use energy?
The brain uses only glucose for energy without the need for insulin
How does the body use energy?
The body can use glucose or fatty acids for energy with the need for insulin to use glucose
Glycogenolysis
The process of breaking down glycogen into glucose with the help of the hormone glucagon
Gluconeogenesis
The process of breaking down fat from adipose storage into fatty acids, glucose, and ketones to be used as fuel under prolonged food deprivation after glycogen stores have been used
Where is excess glucose stored?
Stored as glycogen in the liver and skeletal muscles for short-term usage that’s regulated by insulin
