Internal Regulation Flashcards
What affects many aspects of behaviour? For example, activity levels, sleep-wake cycles.
Temperature.
What is vital to normal functioning?
Temperature regulation.
What does temperature regulation allow?
Normal functioning.
What is homoeostasis?
Maintenance of a set point.
Explain a set point, what it is related to, and some examples.
A single value that the body works to maintain, homoeostasis, and water, oxygen, glucose etc. levels.
What does poikilothermic mean?
The idea that the body temperature matches the environment.
What does ectothermic mean?
The idea that the body temperature matches the environment.
When would an organism become poikilothermic?
When it lacks the internal, physiological mechanisms of temperature regulation.
How is poikilothermic temperature regulation achieved?
Choosing locations in the environment.
What is an example of a poikilothermic animal?
Lizards, other cold-blooded animals.
What does homoeothermic mean?
Use of internal physiological mechanisms to maintain an almost constant body temperature.
What does endothermic mean?
Use of internal physiological mechanisms to maintain an almost constant body temperature.
What does homoeothermic temperature regulation require?
Energy and fuel.
How do homoeothermic animals increase and decrease temperature?
Sweating and panting to decrease temperature, and increasing temperature via shivering, decreasing blood flow, and increasing insulation.
What temperature did mammals evolve to maintain?
Roughly 37 degrees.
Why is an even temperature an advantage for mammals?
Muscle activity benefits from warmth.
If muscle activity benefits from warmth, why aren’t mammals warmer? (2)
Maintaining a higher body temperature increases energy demand, and proteins in the body break their bonds and lose their useful properties at higher temperatures.
What areas of the brain control temperature?
Pre-optic area (POA), and the anterior hypothalamus (AH).
What do the POA and AH control?
Controls panting, sweating and shivering.
What do the POA and AH receive input from? (2)
Temperature receptors in the body and the immune system.
How can the body conserve water? (3)
Excreting concentrated urine, decreasing sweat, and drinking more water than the body needs and excreting the rest.
What is vasopressin?
A hormone released by the posterior pituitary.
What does vasopressin do?
Raises blood pressure by constricting blood vessels, compensates for decreased water volume.
What is vasopressin also known as?
The anti-diuretic hormone (ADH).
What does vasopressin allows the kidneys to do?
Reabsorb water and excrete highly concentrated urine.
What are the two types of thirst?
Osmotic and hypovolemic thirst.
Explain osmotic thirst.
Results from eating salty food.
Explain hypovolemic thirst.
Results from loss of fluids due to bleeding or sweating.
How does osmotic thirst work?
Solutes inside and outside a cell create osmotic pressure, causing water to flow across a semi-permeable membrane from an area of low solute concentrations to an area of high solute concentration.
When does osmotic thirst occur?
When solutes are more concentrated on one side of the membrane than the other.
What is the normal concentration of solutes?
0.15 M
How does the brain detect osmotic pressure? (4)
Receptors around the third ventricle, the organum vasculosum laminae terminalis (OVLT), the sufornical organ, and receptors in the periphery, like the stomach and digestive tract.
What do the OVLT and subfornical organ do?
Detect osmotic pressure and sodium content of the blood.
How is hypovolemic thirst triggered?
By the release of the hormones vasopressin and angiotensin II.
What do angiotensin II and vasopressin do?
Constrict blood vessels to compensate for a drop in blood pressure.
What do neurons in the third ventricle do in relation to angiotensin II?
Send messages to the hypothalamus.
Why do predators have large digestive systems?
Because they’re adapted to huge, infrequent meals.
How often do bears eat?
Constantly.
Why do small birds eat only what is needed in the moment?
To preserve light weight for flight.
What percentage of their body weight do Chickadees eat daily?
10%, but they lose it all at night keeping warm.
What is the function of the digestive system?
To break down food so it can be used.
Where does digestion begin?
In the mouth, with saliva.
What happens to proteins in the stomach?
The hydrochloric acid and enzymes digest them.
What happens in the small intestine?
Enzymes digest proteins, fats, and carbohydrates. which are then absorbed into the bloodstream.
What does the large intestine absorb?
Water and minerals.
What are oral factors in feeding?
The desire to taste and chew, like chewing gum, are motivating factors in hunger.
Do sham feeding experiments produce satiety?
No.
What is the main signal to stop eating?
Stomach distension.
What does the vagus nerve do?
Conveys information about the stretching of the stomach walls to the brain.
What are the splanchnic nerves?
Nerves that convey information about the nutrient contents of the stomach.
What is the duodenum?
Part of the small intestine, which is the site of initial absorption of nutrients.
What, related to the duodenum, can produce feelings of satiety?
Distension.
What hormone does the duodenum release?
Cholecystokinin (CCK)
What does cholecystokinin regulate?
Hunger.
What is glucose? (3)
The main product of digestion, an important source of energy for the body, and nearly the only fuel used by the brain.
What do insulin and glucagon regulate?
The flow of glucose into cells.
What happens to excess glucose?
Enter the liver and fat cells.
What is insulin?
A hormone released by the pancreas.
What does insulin do?
Allows glucose to enter cells.
Explain the first change after a meal.
Blood glucose levels fall.
Explain the second change after a meal.
Insulin levels drop.
Explain the third change after a meal.
Glucose enters cells more slowly.
Explain the fourth change after a meal.
Hunger increases.
Explain the fifth change after a meal.
The pancreas releases glucagon.
What is glucagon?
A hormone released y the pancreas when glucose levels fall.
What does glucagon do?
Stimulates the liver to convert some of its stored glycogen to glucose.
Why does the liver convert stored glycogen to glucose?
To replenish low supplies in the blood.
How is long-term hunger regulation accomplished?
Monitoring fat supplies in the body.
What peptide do the body’s fat cells produce?
Leptin.
What does leptin do?
Signal the brain to increase or decrease eating.
What do low levels of leptin do?
Increase hunger.
What do high levels of leptin do?
Reduce eating and increase physical and immune system activity.
What is the arcuate nucleus?
The master area for controlling appetite.
Where does the arcuate nucleus receive information from?
All parts of the body.
What is the arcuate nucleus a part of?
The hypothalamus.
What types of neurons does the arcuate nucleus contain?
Neurons sensitive to hunger signals, and neurons sensitive to satiety signals.
What is ghrelin?
A neurontransmitter released in the brain that acts on the hypothalamus to increase appetite.
What does gherlin do?
Triggers stomach contractions.
What neurotransmitter has a relationship with obesity?
Ghrelin.
What are satiety signals?
Input to the satiety sensitive cells of the arcuate nucleus.
What does blood glucose stimulate?
Satiety cells in the arcuate nucleus.
What does body fat release and what does that stimulate?
Leptin, which stimulates satiety neurons.
Where does output from the arcuate nucleus go?
The paraventricular nucleus in the hypothalamus.
What does the paraventricular nucleus inhibit?
The lateral hypothalamus.
What delivers an excitatory message to the paraventricuar nucleus?
Axons fro the satiety sensitive cells of the arcuate nucleus.
What do melanocortins do?
Limit food intake.
What do cells in the lateral hypothalamus release?
Orexin.
What does orexin do?
Increases animals persistence in seeking food.
What Influences response to incentives and reinforcement in general?
Orexin.
What does the lateral hypothalamus control?
Insulin secretion and taste responsiveness.
What does stimulation of the lateral hypothalamus increase?
The drive to eat.
What does damage to the lateral hypothalamus do?
Causes aversion to food.
What does the ventromedial hypothalamus inhibit?
Feeding.
What does damage to the ventromedial hypothalamus cause?
Overeating and weight gain.
What is increased stomach motility?
The stomach empties faster than normal.
Why do birds sometimes stand on one leg?
To conserve heat.
How do toucans use their large beaks to regulate temperature?
During flight, blood flow through the beak is cooled, and the toucan tucks its beak under a wing to prevent heat loss.
Who introduced the term homeostasis?
Cannon.
What does homeostasis refer to?
Temperature regulation and other biological processes that keep body variables within a fixed range.
Define a set point.
A single value that the body works to maintain.
Explain negative feedback.
Processes that reduce discrepancies from the set point.
Explain allostasis.
The adaptive way in which the body anticipates needs depending on the situation, avoiding errors rather than just correcting them.
Give some examples of breakdown of homeostasis processes.
Obesity, anorexia nervosa, high blood pressure, and diabetes.
What is basal metabolism?
The energy used to maintain a constant body temperature while at rest.
How much energy does maintaining body temperature take?
Twice as much as all other activities combined.
How do we produce heat?
Metabolism in the brown adipose cells..
An animal ____ heat in proportion to its total mass, but it ____ heat in proportion to its surface area.
Generates, radiates.
Name some physiological mechanisms that increase body heat in a cold environment.
Shivering, decreased blood flow to the skin, and fluffing out the fur.
How does shivering increase heat?
Through muscle contractions.
What cells require a cooler environment than the rest of the body?
Reproductive cells.
What brain areas controls physiological mechanisms like shivering and sweating?
The hindbrain’s raphe nucleus.
Where does the hindbrain’ raphe nucleus receive input from?
The preoptic area and the anterior hypothalamus.
Where does the POA/AH recieve input from?
Temperature receptors in the skin, organs, and the brain, particularly the POA/AH themselves.
How do the immune system and POA/AH work together in the face of infection?
The immune system delivers prostaglandins and histamines to the POA/AH, which causes shivering, increased metabolism, and a fever.
At what temperature does a fever become life threatening?
41 degrees.
How does fever help fight infection?
Certain types of bacterial grow less vigorous at high temperatures, and the immune system works more vigorously at high temperatures.
What are the physiological effects of not drinking on the human body?
Water is conserved by excreting concentrated urine and decreasing sweat.
What does the posterior pituitary do in response to dehydration?
Releases vasopressin, which constricts blood vessels and increases blood pressure.
What is another name for vasopressin?
Antidiuretic hormone (ADH).
What do the kidneys do when activated by vasopressin?
Reabsorb water from urine.
Define osmotic thirst.
Thirst caused by eating salty food.
Define hypovolemic thirst.
Thirst caused by losing fluid by bleeding or sweating.
What does the combined concentration of all solutes in fluids remain at?
0.15 M
What is osmotic pressure?
The tendency of water to flow across a semi-permeable membrane from the area of low solute concentration to the area of higher concentration.
What is a semipermeable membrane?
One which water can pass but solutes cannot.
When does osmotic pressure occur?
When solutes are more concentrated on one side of the membrane than the other.
What is the intracellular fluid?
Fluid inside the cell.
What is the extracellular fluid?
Fluid outside the cell.
Explain what happens when sodium ions are concentrated outside the cells in the extracellular fluid?
Water is drawn from the cells to the extracellular membrane, which triggers osmotic thirst.
Explain osmotic thirst.
A drive for water that helps restore the normal state.
How do the kidneys respond to osmotic thirst?
They excrete concentrated urine to rid the body of excess sodium and maintain as much water as possible.
Where does the OVLT receive input from, and what does this enable it to do?
The digestive tract, enabling it to anticipate an osmotic need before the rest of the body experiences it.
What do the brain areas surrounding the third ventricle monitor?
The contents of the blood.
Where do receptors in the OVLT, the subfornical organ and stomach relay their information to?
Several areas of the hypothalamus, like the supraoptic nucleus and the paraventricular nucleus (PVN).
What do the supraotic nucleus and paraventricular nucleus control?
The rate at which the posterior pituitary release vasopressin.
What does the lateral preoptic area control?
Drinking.
What do the kidneys release when blood volume drops?
The enzyme renin, which splits a portion off angiotensinogen to form angiotensin I, which is then converted to angiotensin II.
What are the effects of angiotensin II?
It constricts the blood vessels, compensating for the drop in blood pressure, and triggers thirst.
How is hypovolemic thirst different from osmotic thirst?
The body needs to restore lost salts and not just water.
What happens when angiotensin II reaches the brain?
It stimulates neurons in areas adjoining the third ventricle, which causes the hypothalamus to release angiotensin II as a neurotransmitter.
Define sodium-specific hunger.
An animal that becomes deficient in sodium shows an immediate strong preference for salty tastes.
What do the adrenal gland produce when sodium reserves are low?
Aldosterone.
What does aldosterone do?
It causes the kidneys, salivary glands and sweat glands to retain salt.
What is the effect of aldosterone and angiotensin II on taste?
They change the properties of taste receptors on the tongue, and neurons in the nucleus of the tractus solitarius to increase salt intake.
What is the function of the digestive system?
To break food into smaller molecules that the cells can use.
Where does digestion begin?
In the mouth, where enzymes in saliva break down carbohydrates.
What happens in the stomach?
Food mixes with hydrochloric acid and enyzmes that digest proteins.
What does the small intestine do?
Digests proteins, fats and carbohydrates, and absorbs digested material into the bloodstream.
What happens in the large intestine?
Absorbs water and minerals and lubricates the remaining materials to pass as feces.
What is lactase?
An intestinal enzyme which is necessary for metabolising lactose, the sugar in milk.
How does tryptophan induce sleepiness?
After eating carbohydrates, insulin moves sugars and phenylalanine into storage, which makes it easier for tryptophan to reach the brain, inducing sleepiness.
How does the stomach convey satiety to the brain?
The vagus nerve and the splanchnic nerves
Which cranial nerve is the vagus nerve?
Cranial nerve X.
What information does the vagus nerve convey?
Information about the stretching of the stomach.
What information do the splanchnic nerves convey?
Information about the nutrient content of the stomach.
Where is oleoylethanolamide (OEA) released?
By fat in the duodenum.
What does OEA stimulate?
The vagus nerve.
How does cholecystokinin (CCK) limit meal size? (2)
It constricts the sphincter muscle between the stomach and the duodenum, causing the stomach to hold its contents and fill more quickly, or it stimulates the vagus nerve to send signals to the hypothalamus, which then releases a neurotransmitter that is a shorter version of the CCK.
What two pancreatic hormones regulate the flow of glucose into cells?
Insulin and glucagon.
When is insulin released?
Before, during and after a meal.
What happens to excess glucose after a meal? (2)
The liver converts it into glycogen and stores it, and fat cells convert it to fat and store it.
What happens after a meal?
Blood glucose and insulin levels fall, glucose enters the cells more slowly and hunger increases.
Explain glucagon’s role.
It stimulates the liver to convert some of its stored glycogen back to glucose.
What happens if insulin levels remain constantly high?
The body continues moving blood glucose into liver and fat cells long after a meal, causing rapid drops in blood glucose and increases in hunger.
What happens if insulin levels remain constantly low, as in type I diabetes?
Blood glucose levels may be three or more times the normal levels, but little enters the cells, so they eat more but excrete most of the glucose in their blood.
How does the body compensate for day-to-day errors in consumption?
By monitoring fat supplies.
What animals is leptin limited to?
Vertebrates.
When does leptin sensitivity decline?
During pregnancy, obesity, and in animals preparing for hibernation.
What is the only way to reverse the effects of obesity on leptin?
Prolonged physical exercise, which increases production of chemicals of the immune system and decreases inflammation of the hypothalamus.
What two sets of neurons does the arcuate nucleus contain?
One sensitive to hunger signals and the other sensitive to satiety signals.
When and where is ghrelin released?
The stomach, during periods of food deprivation where it triggers stomach contractions.
Where does the output from the arcuate nucleus go?
The paraventricular nucleus.
What does the paraventricular nucleus inhibit?
The lateral hypothalamus.
What are the inhibitory neurotransmitters involved in the hypothalamus?
GABA, neuropeptide Y (NPY), and agouti-relatedpeptide (AgRP).
How are melanocortins released?
Axons from the satiety-sensitive cells of the arcuate nucleus deliver an excitatory message to the paraventricular nucleus.
What are melanocortin receptors important for?
Limiting food intake.
Name the two types of input the amygdala and related areas send to the hypothalamus?
One path inhibits eating during illness and mediates aversion too foods previously associated with illness, and the other path stimulates eating in response to highly tasty foods.
What pathway releases orexin?
The pathway from the paraventricular nucleus leads to cells in the lateral hypothalamus.
Name orexin’s two roles in feeding.
It increases animal’s persistence in seeking food, and it responds to incentives in general.
What does the lateral hypothalamus control?
Insulin secretion, alters taste responsiveness, and facilitates feeding.
How does the lateral hypothalamus effect taste?
Axons from the lateral hypothalamus to the NTS (nucleus or the tractus solitarius) alter the taste sensation and the salivation response to the tastes - therefore, when the lateral hypothalamus detects hunger, it makes food taste better.
What do the lateral hypothalamus’ connections with the cerebral cortex facilitate?
Ingestion, swallowing, and causing cortical cells to increase their response to taste, smell or sight of food.
What is the effect of the lateral hypothalamus on the pituitary gland?
It increases the secretion of hormones that increase insulin secretion.
What does damage to the ventromedial hypothalamus cause?
Overeating and weight gain.
What kind of meals does a damaged paraventricular nucleus enable?
Large meals.
What kind of meals does a damaged ventromedial nucleus enable?
Normal sized meals, but more frequently.
What is the effect of a lesion in the preoptic area?
A deficit in physiological mechanisms of temperature regulation.
What is the effect of a lesion in the lateral preoptic area?
A deficit in osmotic thirst due partly to damage to cells and partly to interruption of passing axons.
What is the effect of a lesion in the lateral hypothalamus?
Undereating, weight lodd, low insulin level, underarousal, and underresponsiveness.
What is the effect of a lesion in the ventromedial hypothalamus?
Increased meal frequency, weight gain and a high insulin level.
What is the effect of a lesion in the paraventricular hypothalamus?
Increased meal size, especially increased carbohydrate intake during the first meal.
Explain syndromal obesity?
Obesity that results from a medical condition.
What is Prader-Willi syndrome?
A genetic condition marked by mental retardation, short stature, and obesity.
How does Prader-Willi syndrome cause obesity?
People with the syndrome have blood levels of ghrelin 4-5 times higher than average.
Name some genes associated with obesity?
A mutated gene for the recepetor for melanocortin, and a variant form of the gene FTO.
What is bulimia nervosa?
A condition in which people alternate between binges of overeating and periods of strict dieting.
