Chapter 9 PsychBio

Three types of heritability for obesity

1) Syndromal obesity When a gene causes a medical problem that includes obesity. Prader-Willi syndrome. Blood levels of ghrelin 4-5x higher than average. 2) Monogenic obesity When a single gene leads to obesity without other physical or mental abnormalities. 3) Polygenic / Common obesity Many genes that slightly increase the probability of obesity.

Allostasis

Adaptive way in which the body changes its set points depending on the situation

Aldosterone

Adrenal hormone that causes the body to retain salt

Lateral hypothalamus

Area of the hypothalamus that controls insulin secretion and alters taste responsiveness An animal with damage to this area refuses food and water, but if it is stimulated, there is an increased drive to eat.

The Lateral Hypothalamus facilitates feeding by... (4)

Axons from the lateral hypothalamus to the NTS (nucleus of the tractus solitarius) alters taste sensations and salivation responses to tastes. When the lateral hypothalamus detects hunger, it sends messages that make the food taste better. Axons from the lateral hypothalamus extend into several parts of the cerebral cortex, facilitating ingestion and swallowing and causing cortical cells to increase their response to the taste, smell, or sight of food. Increases pituitary gland's secretion of hormones that increase insulin secretion. Sends axons into the spinal cord, controlling autonomic responses such as digestive secretions.

Preoptic area/anterior hypothalamus (POA/AH)

Brain area important for temperature regulation, thirst, and sexual behavior

Subfornical organ (SFO)

Brain structure where its cells monitor osmotic pressure and sodium concentration. Has one area of neurons that increases thirst and another that suppresses it.

Osmotic Thirst

Caused by eating salty foods.

Hypovolemic Thirst

Caused by losing fluid by bleeding or sweating. Heart has trouble pumping blood to the head, and nutrients do not flow as easily as usual into your cells. Receptors on your kidneys and blood vessels react to the decreased blood pressure by sending messages to the brain to release vasopressin, which constricts blood vessels and conserves fluid. Kidneys also release renin, which helps to build A2.

Ghrelin

Chemical released by the stomach during a period of food deprivation. Also released as a neurotransmitter on the hypothalamus which stimulates eating. Binds to the same receptors as growth-hormone releasing hormone [GHRH].

Neuropeptide Y (NPY)

Compound that blocks the satiety actions of the paraventricular nucleus

Input to the satiety-sensitive cells of the arcuate nucleus

Distension of the intestines releases CCK (Short term). Blood glucose directly stimulates satiety cells and prompts the pancreas to release insulin, which also stimulates these cells (Short term). Body fat releases leptin (Long term). Nicotine also stimulates satiety cells.

Antidiuretic hormone (ADH)

Enabler of the kidneys to reabsorb water from urine (which makes urine more concentrated); also known as vasopressin. Released in posterior pituitary which raises blood pressure by constricting blood vessels. This compensates for decreased blood volume. Supraoptic nucleus and the paraventricular nucleus (PVN) control the rate at which the posterior pituitary releases vasopressin.

Basal metabolism

Energy used to maintain a constant body temperature while at rest

Output from the Arcuate Nucleus

Goes to the paraventricular nucleus (PVN) of the hypothalamus. Axons from the satiety-sensitive cells of the arcuate nucleus deliver an excitatory message to the paraventricular nucleus, releasing melanocortins and glutamate.

Leptin

Hormone released by fat cells in proportion to their volume. As fat reserves decrease, leptin decreases, and you react by eating more and becoming less active, to save energy. As leptin levels return to normal, you eat less and become more active.

Cholecystokinin (CCK)

Hormone released from the duodenum that constricts the sphincter muscle between the stomach and duodenum. CCK stimulates the vagus nerve, which sends signals to the hypothalamus, which causes cells to release a neurotransmitter that is a shorter version of CCK. Short Term Effects only.

Angiotensin II

Hormone that constricts the blood vessels, compensating for the drop in blood pressure. When A2 stimulates neurons in the third ventricle, those neurons send axons back to the hypothalamus, which release A2. The neurons surrounding the third ventricle respond to A2 and release it. A and A2 change properties of taste receptors on the tongue, neurons in the nucleus of the tractus solitarius (part of the taste system) and neurons elsewhere in the brain to increase salt intake. A indicates low sodium while A2 indicates low blood volume.

Arcuate Nucleus

Hypothalamic area with sets of neurons for hunger and satiety. Input comes from insulin and leptin, but also from amygdala, basal forebrain, and thalamus. Part of the input to the hunger sensitive cells comes from axons releasing ghrelin

Ventromedial Hypothalamus

Hypothalamus region in which damage leads to faster stomach emptying and increased insulin secretion

Agouti-related peptide (AgRP)

Inhibitory transmitter that blocks the satiety actions of the paraventricular nucleus

Three hormones that increase satiety and one that increases hunger.

Insulin, CCK, Leptin. Ghrelin.

Damage to the ventromedial hypothalamus and the surrounding area...

Leads to overeating and weight gain. Cells are starved for nutrition because high insulin levels keep moving blood glucose into storage.

Which neuropeptide from the arcuate nucleus to the paraventricular nucleus is most important for satiety?

Melanocortin

Insulin

Pancreatic hormone that enables glucose to enter the cells. Released immediately before and after a meal

Glucagon

Pancreatic hormone that stimulates the liver to convert stored glycogen to glucose. As time passes after a meal, insulin levels drop, glucose enters cells more slowly, and hunger increases. The pancreas releases glucagon, which stimulates the liver to convert some of its stored glycogen back into glucose.

Paraventricular nucleus (PVN)

Part of the hypothalamus in which activity tends to limit meal size. Certain cells in the PVN inhibit the lateral hypothalamus, an area important for eating. These inhibitory transmitters are a combination of GABA, neuropeptide Y (NPY) and agouti-related peptide (AgRP) Inhibiting an inhibitor produces net excitation, which is how the stimuli for hunger increase eating and arousal. Additional pathway from the PVN leads to cells in the lateral hypothalamus that release orexin. Orexin plays a role in wakefulness, but two roles in feeding: Increases animals' persistence in seeking food. Increases activity and motivation in general.

Preoptic Area

Part of the hypothalamus that controls drinking

Duodenum

Part of the small intestine adjoining the stomach; first digestive site that absorbs nutrients. Distension of the duodenum releases cholecystokinin.

Organum vasculosum laminae terminalis (OVLT)

Structure important for monitoring osmotic pressure and sodium concentration in the blood. Receives input from digestive tract, which enables it to anticipate needs.

Osmotic pressure

Tendency of water to flow across a semipermeable membrane from low to high solute concentration

Homeostasis

Tendency to maintain a variable, such as temperature, within a fixed range

___ conveys info to the brain about the stretching of the stomach walls.

The vagus nerve

Melanocortin

Type of chemical that promotes satiety

Both OVLT and SFO...

detect sodium levels in blood, and both provide input to the hypothalamus.

The main signal to end a meal is...

distension of the stomach.

Negative Feedback

homeostatic process that reduces discrepancies from the set point