Ch. 9 Flashcards
Chapter 9 of The Mind's Machine
Homeostasis
The maintenance of a relatively constant internal physiological environment
Motivation
The psychological process that induces or sustains a particular behavior
Deviations from the optimum state can affect what?
Motivation- ex. overwhelmingly powerful need to get water if you’re lost in the desert)
Thermoregulation
The active process of maintaining a relatively constant internal temperature through behavioral and physiological adjustments
Endotherms
An animal whose body temperature is regulated chiefly by internal metabolic processes (mammals). We make our own heat inside our bodies
Ectotherms
An animal whose body temperature is regulated by, and whose heat comes mainly from, the environment
Negative Feedback
The process whereby a system monitors its own output and reduces its activity when a set point is reached. The property by which some of the output of a system feeds back to reduce the effect of input signals. Ex. house thermostat
Set Point
The point of reference in a feedback system
Set Zone
The optimal range of a variable that a negative feedback system tries to maintain
How does our body use redundancy to maintain homeostasis?
Multiple redundancy (backup that protects the critical system) is a feature of many of the body’s homeostatic systems, protecting the constant internal environment that is crucial for survival
What are three kinds of temperature-regulating behavior?
- Behaviors that change exposure of the body surface (huddling or extending limbs)
- Behaviors that change external insulation (using clothes or nests)
- Behaviors that change surroundings (moving into the sun, into the shade, or into a burrow)
How does the mammalian thermoregulatory system function in general?
Receptors in the skin, body core, and hypothalamus detect temperature and transmit that information to three neural regions (spinal cord, brainstem, and hypothalamus). If the body temperature moves outside the set zone, each of these neural regions can initiate physiological and behavioral responses to return it to the set zone
Allostasis
The behavioral and physiological adjustments that maintain optimal (rather than unchanging) functioning of a regulated system in the face of changing environmental stressors
Obligatory Losses
The unavoidable expenditures of bodily resources that must then be regained from the external environment. Ex. restoring expended water
What percentage of the brain is water?
80%
Most organisms evolved homeostatic systems that ensure the composition of their body fluids closely resembles what?
Dilute Seawater
Intracellular Compartment
The fluid of the body that is contained within cells
Extracellular Compartment
The fluid of the body that exists outside the cells. Divided between the interstitial fluid (the fluid between cells) and blood plasma (the protein-rich fluid that carries red and white blood cells)
Diffusion
The spontaneous spread of molecules from an area of high concentration to an area of low concentration until a uniform solute concentration is achieved
Selectively Permeable
Also called semipermeable. A membrane that is permeable to some molecules but not other
Osmosis
The passive movement of a solvent, usually water, through a semipermeable membrane until a uniform concentration of solute (often salt) is achieved on both sides of the membrane
Osmotic Pressure
The tendency of a solvent to move across a membrane in order to equalize the concentration of solute on both sides of the membrane
Physiological Saline
A solution with a concentration of salt of about 0.9 percent. This is normally the concentration of salt in the extracellular fluid of animals. Described as isotonic.
When do cells lose water?
If the cells are surrounded by a saltier solution because the water will move out of the cell to produce uniform saltiness.
What can happen if the movement of water out of the cell is excessive?
it will damage or kill the cell
The extracellular fluid serves as a what?
Buffer: a reservoir of isotonic fluid that provides and accepts water molecules, so cells can maintain proper internal conditions and prevent such damage
Osmotic Thirst
A desire to ingest fluids that is stimulated by high concentration of solute (like salt) in the extracellular compartment. Water is pulled out of cells through osmosis.
Osmosensory Neurons
A specialized neuron that monitors the concentration of the extracellular fluid by measuring the movement of water into and out of the intracellular compartment. Found in several hypothalamic regions and the organum vasculosum lamina terminalis (OVLT)
Organum Vasculosum Lamina Terminalis (OVLT)
One of a set of specialized brain structures, called the circumventricular organs, that monitor the fluid balance of the body
Circumventricular Organs
Any of multiple distinct sites that lie in the wall of a cerebral ventricle and monitor the composition of the cerebrospinal fluid.
Vasopressin
Also called arginine vasopressin (AVP) or antidiuretic hormone (ADH). A peptide hormone from the posterior pituitary that promotes water conservation and increases blood pressure. Acts on the kidneys to slow the production of urine by increasing the reabsorption of water
Aldosterone
A steroid hormone that is released from the adrenal glands in order to stimulate the kidneys to conserve Na+
Hypovolemic Thirst
A desire to ingest fluids that is stimulated by a reduction in volume of the extracellular fluid. Could result from vomiting, diarrhea, or hemorrhage
Baroreceptors
Pressure receptors located in major blood vessels and in the heart that detect the initial drop in extracellular volume
What does the brain activate in response the the signal from the baroreceptors (extracellular volume is too low)?
-thirst
-salt hunger
-sympathetic nervous system stimulates muscles in the artery walls to constrict, reducing the size of the vessels and partly compensating for the reduced volume
-organs respond by altering hormonal release
Replacing the water without replacing salts would result in what?
Hypotonic extracellular fluid
How is hormone release altered in response to hypovolemic thirst?
-heart decreases its secretion of atrial natriuretic peptide (ANP)=hormone that would typically promote the excretion of water and salt
-The brain’s posterior pituitary gland releases more vasopressin
-kidneys trigger the production of angiotensin II (AII)
Angiotensin II (AII)
A hormone produced in the blood by the action of renin and that may play a role in the control of thirst. Also increases blood pressure.
What do gut neurons monitor?
The saltiness of the fluid in the stomach and intestine and communicate this information to the brain via the vagus nerve
Nutrients
Chemicals required for the effective functioning, growth, and maintenance of the body
Glucose
An important sugar molecule used by the body and brain for energy. Obtained through the breakdown of more-complex molecules
Glycogen
A complex carbohydrate made by the combining of glucose molecules for a short-term store of energy
Glygogenesis
The process of converting glucose into glycogen and storing it. Promoted by insulin
Insulin
A pancreatic hormone that lowers blood glucose, promotes energy storage, and facilitates glucose utilization by cells. Synthesized and released by the pancreas
Glucagon
A pancreatic hormone that converts glycogen back into glucose and thus increases blood glucose (process called glycogenolysis)
Lipid
fat
What happens for long-term nutrient storage?
Molecules of lipid (fat) from dietary sources or created from surplus sugars and other nutrients are stored in adipose tissue (commonly called fat tissue)
Under conditions of prolonged food deprivation, what happens to body fat?
-gluconeogenesis: body fat is converted into glucose
-A secondary form of fuel (ketones) can be similarly utilized by the body and brain
Ketones
An organic molecule, derived from the breakdown of fat, that can be used by cells as an energy source
Basal Metabolism
The use of energy for processes such as heat production, maintenance of membrane potentials, and all the other basic life-sustaining functions of the body
What percentage of energy from food is used for active behavioral processes?
10-20 percent, the rest is used for basal metabolism
Metabolic Adaptation
A dramatic decrease in basal metabolism following weight loss
Glucose Transporter
The membrane-spanning proteins that most cells use to import glucose from the blood. Needs insulin in order to function.
Diabetes Mellitus
A condition, characterized by excessive glucose in the blood and urine and by reduced glucose utilization by body cells, that is caused by a failure to sufficiently produce (type 1) or respond to insulin (type 2)
Cephalic Phase
Insulin release triggered by sights, smells, and tastes that we have learned to associate with food
Digestive Phase
Food entering the digestive tract prompts additional release of insulin
Absorptive Phase
As digested food is absorbed into the bloodstream, specialized liver cells called glucodetectors detect the increase in circulating glucose and signal the pancreas to release still more insulin.
Glucodetectors
A specialized type of liver cell that detects and informs the nervous system about levels of circulating glucose
Viewing pictures of food items increased activity in what brain area?
hypothalamus, and thalamic and frontal regions
Arcuate Nucleaus
An arc-shaped hypothalamic nucleus implicated in appetite control
Leptin
A peptide hormone released by fat cells. The brain monitors circulating leptin levels as an indicator of the body’s longer-term energy reserves in the form of fat
Ghrelin
A peptide gut hormone believed to act on the hypothalamic appetite system to increase hunger
PYY 3-36
A peptide gut hormone believed to act on the hypothalamic appetite system to suppress appetite
Glucagon-like peptide 1 (GLP-1)
A peptide gut hormone believed to act on the hypothalamic appetite system to suppress appetite
POMC/CART Neurons
act as satiety neurons when activated, inhibiting appetite and increasing metabolism
NPY/AgRP Neurons
act as hunger neurons when they are activated, stimulating appetite directly and also inhibiting the POMC/CART neurons (thereby blocking satiety signals) and reducing metabolism
Orexigenic Neurons
Neurons of the hypothalamic appetite system that promote feeding behavior
Anorexigenic Neurons
Neurons of the hypothalamic appetite system that inhibit feeding behavior
Nucleus of the Solitary Tract (NST)
A complicated brainstem nucleus that receives visceral and taste information via several cranial nerves
Orexin
Also called hypocretin. A neuropeptide produced in the hypothalamus that is involved in switching between sleep states, in narcolepsy, and in the control of appetite.
Endocannabinoid
An endogenous ligand of cannabinoid receptors, thus an analog of cannabis that is produced by the brain. Stimulates appetite
Epigenetic Transmission
The passage from one individual to another of changes in expression of targeted genes, without altering the sequence of nucleotides in the gene
Parental obesity may program metabolic disadvantages in offspring via what?
epigenetic transmission
What are some strategies to overcome obesity?
-appetite control: drugs designed to reset the hypothalamic appetite controller
-increased metabolism: raise the body’s metabolic rate and thus expend extra calories in the form of heat
-inhibition of fat tissue: blocking the formation of new fat tissue
-reduced absorption: interfering with the digestion of fat
-reduced reward: reducing the rewarding properties of food may promote weight loss
-Anti-obesity surgery: install a gut liner in order to reduce the absorptive capacity of the digestive system
-Lifestyle changes
-manipulation of the gut microbiome
Anorexia Nervosa
A syndrome in which individuals severely deprive themselves of food
Gut Microbiota
The microorganisms that normally inhabit the digestive system
Enterotype
Each individual’s personal composition of the gut microbiota
Bulimia
Also called bulimia nervosa. A syndrome in which individuals periodically gorge themselves, usually with “junk food,” and then either vomit or take laxatives to avoid weight gain.
Binge Eating
The rapid intake of large quantities of food, often poor in nutritional value and high in calories
