Biopsyc - Chapter 10: Homeostasis: Hunger, Thirst, and Temperature

Homeostasis

Maintaining a balance of the body's internal states, including but not limited to temperature, sugar, fats, proteins, water, salts, PH, and hormones.

Set points

Optimal level of the body's internal states. There are mechanisms to compare the body's current state to its set points that use feedback loops to maintain set points.

Positive or negative feedback loops

Biological and behavioral mechanisms to adjust the body's internal state to get it close to set points. Ways of maintaining homeostasis.

Allostasis

Behavioral and physiological changes to maintain homeostasis in a changing environment.

Glucose

A simple sugar that is used in cellular respiration to create energy in the form of ATP. It is the only thing that can be used in the brain for energy, so having a balanced amount of glucose is important.

Glucoprivation

Low levels of glucose detected in the blood, creating hypoglycemia, which can be dangerous. Feedback loops increase glucose when glucoprivation is detected.

Glycogen

The storage of glucose in long chains.

Insulin

A hormone secreted by the pancreas that binds free glucose into glycogen. … also helps transport glucose into cells to be broken down in cellular respiration to create energy in the form of ATP.

Glucagon

A hormone secreted by the pancreas that releases individual glucose molecules from glycogen.

Cholecytokinin (CCK)

Hormone secreted by the digestive system that is important in initiating fat digestion. It also acts as an appetite suppressant through the vagus nerve.

Ventromedial hypothalamus (VMH)

An area of the hypothalamus with glucose-sensing neurons and may serve a function in appetite satiation. Lesions in this area make animals eat too much and get fat.

Lateral hypothalamus (LH)

An area of the hypothalamus with glucose-sensing neurons that may function in increasing appetite. Lesions in this area make animals eat less.

Arcuate nucleus (ARC)

Area of the hypothalamus important in feeding. It detects digestive hormones like leptin—lesions in this area cause uncontrolled feeding in animals.

Median eminences

Area between the hypothalamus and the pituitary gland that can detect large molecules in the blood normally blocked by the blood-brain barrier.

Neuropeptide Y (NPY)

A neurotransmitter for cells in the arcuate nucleus, which is important in chemical detection in the blood and signaling other areas concerning appetite.

Glucostatic theory

The idea that we have mechanisms for detecting blood glucose and physiological and behavioral mechanisms to keep homeostatic glucose levels in the body.

Glucose-sensing neurons

Neurons that change their firing rate depending on the levels of glucose in the blood. There are two types: glucose-inhibiting neurons and glucose-exciting neurons.

Lipostatic theory

This is the idea that we have a set-point of fat, and we have ways of detecting fat levels and behavioral and physiological mechanisms to keep this set point. This set point can be changed, but slowly.

Weight set-point theory

The idea that we have a way to monitor our weight to keep it at a set point. Losing weight quickly initiates physiological and behavioral mechanisms to get back to set point.

Leptin

This is a hormone released from fat cells that act as an appetite suppressant by affecting NPY neurons in the arcuate nucleus.

ob/ob mouse

A strain of mouse with an abnormal form of the hormone leptin. Leptin is unable to signal the arcuate nucleus and so the mouse remains hungry.

db/db mouse

A strain of mouse with nonfunctioning leptin receptors. The … mouse is often used as an animal model for diabetes.

Peptide YY (PYY)

A chemical released from the small intestine and colon in response to meals. It acts as a messenger to slow the movement of food from the stomach, but it also acts as an appetite suppressant affecting NPY neurons in the arcuate nucleus.

Ghrelin

A hormone secreted from the small intestine that promotes hunger.

Iron

An element important in blood cells. Low levels have been shown to affect cognitive performance.

Proteins

One of the three main types of nutrition. Proteins are needed for enzymes, building bones and muscle, and creating neurotransmitters. There is also evidence that a balanced diet with sufficient protein is important in cognition.

Omega-3 fatty acids

Fatty acids made from fish oil that may reduce symptoms of depression and help with neurogenesis.

Body-mass index (BMI)

The value that relates height to weight. BMI above 30 is considered obese.

Type 2 diabetes

The disorder often caused by obesity in which the body does not produce enough insulin, resulting in several health-related problems and forcing people to monitor blood glucose levels and inject insulin.

Bariatric surgery

Laparoscopic surgery where the stomach is made smaller and the area for absorption in the small intestine is reduced—a proven way to reduce weight in people who are obese.

Osmoregulation

The body's attempt to monitor and maintain homeostatic water levels in the body.

Osmosis

The movement of water through a cell membrane from an area of high to low concentration of water.

Hypotonic

An extracellular environment that has a higher water concentration than the cell. Water flows into the cell, and it swells.

Hypertonic

An extracellular environment that has a lower water concentration than the cell. Water flows out of the cell, so it shrinks.

Isotonic

Where the cell and the extracellular environment have the same water concentration, so there is no directional flow of water.

Osmotic thirst

Thirst brought on by a hypertonic extracellular environment possibly caused by extra salt in the blood.

Hypovolemic thirst

Thirst caused by low blood volume brought on by the loss of blood, vomiting, or diarrhea.

Osmoreceptors

Neurons in the hypothalamus that change their firing rate depending on water concentration.

Organum vaculosum of the lamina terminalis (OVLT)

This area has neurons that have osmoreceptors so they can detect levels of water and salt. They send signals to the supraoptic nucleus of the hypothalamus.

Supraoptic nucleus

Area of the hypothalamus that release antidiuretic hormone (ADH) from the posterior pituitary gland.

Antidiuretic hormone (ADH)

Also known as vasopressin, the hormone released from the posterior pituitary gland that signals the kidney to release less water in the urine.

Renin

Enzyme released from the juxtaglomerular cells in the kidney in response to low water concentration or high salt concentration in the blood. Causes the production of angiotensin II.

Hyponatremia

A condition where there is too much water in the blood and not enough salt, causing cells to swell and possibly die. Can be very dangerous.

Endotherms

Animals (e.g., mammals and birds) that maintain their body temperature by generating heat.

Ectotherms

Animals (e.g., reptiles, amphibians, and insects) that must use external sources of heat to reach optimal body temperature.

Hypothermia

This is when the body becomes too cold, causing muscle shivering, and can lead to drowsiness, unconsciousness, and death.

Hyperthermia

This is when the body becomes too warm, causing sweating, and eventually dizziness, seizures, and death.

Preoptic area of the hypothalamus (POA)

An area that has thermosensing neurons and regulates body temperature.

Brown fat cells

A type of adipose tissue that generates heat when energy is burned from these cells. They are important in thermoregulation.

Interleukin-1

Chemical messengers from white blood cells in the immune system. They can signal the hypothalamus to raise the body temperature, causing a fever.

Microbiome

Bacteria, viruses, and fungi that live primarily in the gut. The health of these microbes is linked to mood, behavior, and diseases.

MIA mice

A strain of mice created by giving the mice's mother fever during pregnancy. They show similar behavioral characteristics to children on the autism spectrum. These mice also have similar problems with their digestive system and microbiome.

Alpha-synuclein

Proteins found in high levels in people with Parkinson's disease that begin to develop in the gut first.

Angiotensin II

Increases under the influence of renin and helps retain water in the kidney. Also acts as a messenger to the brain to promote thirst.