Internal regulation Flashcards
Homeostasis:
Temperature regulation and other biological processes that keep certain body variables within a fixed range.
Set point:
Level at which a homeostatic process maintains a variable.
Negative feedback:
Processes that reduce discrepancies from the set point.
Allostasis:
Dynamic, adaptive and anticipatory changes in the body’s set points in response to changes in its life or changes in the environment (much of this control depends on cells in the hypothalamus)
Basal Metabolism:
Energy used to maintain a constant body temperature at rest. Twice as much energy is used for temperature regulation as all other activities combined (2/3 of energy is spent on basal metabolism)
Poikilothermic:
Animals with body temperatures the same as their environment (i.e., fish and lizards).
Homeothermic:
Animals with physiological mechanisms that maintain an almost constant body temperature despite variations in environmental temperature. These types of animals generate heat in proportion to their total mass but radiate heat in proportion to their surface area. For these animals, sweating, licking themselves, and panting are used as cooling mechanisms. Shivering and fluffing are used as heating mechanisms
preoptic area/anterior hypothalamus (POA/AH).
The brain regions most critical for temperature control are the anterior hypothalamus and the preoptic area of the hypothalamus (preoptic because it is near the optic chiasm). Because of the close relationship between these areas, they are often treated as one area, the preoptic area/anterior hypothalamus (POA/AH).
b. The POA/AH controls the physiological mechanisms such as shivering, sweating, changes in heart rate and metabolism and changes in blood flow to the skin
Fever
Fever is part of the body’s defences for illness (not the illness itself).
d. Fever works because certain types of bacteria grow less vigorously at high temperatures, and it enhances the activity of the immune system. However, a fever above 39C does more harm than good, and a fever above 41C is life threatening.
Water
- Mammalian body is about 70% water
- Water determines the rate of all chemical reactions in the body, the water must be regulated within narrow limits
vasopressin, also known as antidiuretic hormone (ADH)
For humans, when your body needs water, the posterior pituitary gland releases vasopressin, also known as antidiuretic hormone (ADH), which enables the kidneys to reabsorb water and secrete highly concentrated urine.
Thirst can be divided into two types:
thirst due to eating salty foods (osmotic thirst) and thirst due to a loss of fluids (hypovolemic thirst).
Osmotic pressure:
The tendency of water to flow across a semipermeable membrane from an area of low concentration to areas of high concentration. In cells, the membrane works as a semipermeable membrane and water, but not all solutes, flows freely between the extracellular fluid (fluid outside the cell) and intracellular fluid (fluid inside the cell).
Osmotic thirst: Occurs when certain neurons detect their own loss of water. This loss of water happens when solute concentrations in the extracellular fluid are higher than the concentration of solutes in the intracellular fluid, causing water to be drawn from the intracellular compartment to dilute the solutes in the extracellular fluid.
Occurs when certain neurons detect their own loss of water. This loss of water happens when solute concentrations in the extracellular fluid are higher than the concentration of solutes in the intracellular fluid, causing water to be drawn from the intracellular compartment to dilute the solutes in the extracellular fluid.
Organum Vasculosum Laminae Terminalis (OVLT) and subfornical organ:
Areas located around the third ventricle that are responsible for detecting osmotic pressure.
5. The brain also receives information from receptors in the periphery, including the stomach, that detect high levels of sodium.
The supraoptic nucleus and paraventricular nucleus:
are brain areas located in the hypothalamus that control the rate at which the posterior pituitary gland releases vasopressin.
- Both of these brain areas and the lateral preoptic area (which controls drinking) receive information from the OVLT, the subfornical organ, the stomach, and elsewhere.
angiotensin II
this hormone constricts blood vessels in order to reverse the loss of blood volume and triggers hypovolemic thirst
1. When you lose a significant amount of body fluid by bleeding, diarrhea, or sweating, the body will release hormones, including vasopressin and angiotensin II, that constrict blood vessels. When blood volume decreases, kidneys release the hormone rennin, which splits a portion off angiotensinogen (a large protein in the blood) to form angiotensin I, which is then converted into angiotensin II
hypovolemic thirst
(thirst based on low volume).
- During hypovolemic thirst the body needs to replenish both water and lost solutes such as salt.
aldosterone:
Specific sodium cravings (due to bleeding or excessive sweating) are caused by the release of aldosterone, a hormone which causes the kidneys, salivary glands, and sweat glands to conserve sodium and excrete more watery fluids than usual.
lactase
Many mammals lose the intestinal enzyme lactase, which allows them to metabolize lactose (sugar found in milk). Losing the enzyme lactase may be an evolved mechanism to encourage weaning.
d. The ability to consume large amounts of milk products varies geographically. In China and surrounding countries, nearly everyone lacks the ability to metabolize lactose.
e. The ability to digest lactose depends on the origins of our ancestors (more likely in places that domesticated cattle).
In sham-feeding experiments
everything an animal eats leaks out a tube connected to the esophagus or stomach (under these conditions, animals consume several times as much as untreated animals during each meal).
c. These studies demonstrate that although taste and mouth are important cues, they are not sufficient alone to produce satiety.
The vagus nerve (cranial nerve X)
carries information to the brain regarding the stretching of stomach walls, providing a major basis for satiety.
The splanchnic nerves
convey information about the nutrient contents of the stomach, carrying impulses back and forth from the spinal cord to the digestive organs.
The duodenum
is part of the small intestine adjoining the stomach. The duodenum also releases a hormone called oleoylethanolamide (OEA) to cause satiety.
