Homeostasis Flashcards
What happens when the parasympathetic division is activated in initiating feeding?
Feeding behavior is stimulated
What does drinking more water cause in hyponatremia?
Worse conditions. Fave the fluid signal (ADH) mixed with more fluid
A fluid containing solutes
Solution
What is lipostatic theory and where can it be seen functioning in the body?
We are sensitive to the amount of fats we have. Receptors in the liver monitor fatty acids
What does the ventromedial hypothalamus do?
Participates in satiety (fullness)
Why do we eat?
Energy and nutrients, pleasure, and complex cultural and psychological factors
How is hyponatremia caused?
Extreme endurance activities caused by low extracellular fluid and low Na
What are osmoreceptors?
Neurons that change firing rate due to water tonicity
What parts of the brain are associated with the hypothalamus?
Infundibulum, anterior pituitary, and posterior pituitary
What does angiotensin II do?
Aids in maintaining blood pressure (tightens blood vessels) and signals the adrenal glands to secrete aldosterone which promotes retention of sodium by the kidneys
Solutions with equal concentrations of solutes. Goal
Isotonic
What leads to hydration?
Water + electrolytes
What percentage of body fluid is intracellular?
67%
What happens with ADH and Na levels in hyponatremia?
ADH is continuously produced which causes water retention and further reduction in Na concentration
What are causes of hypovolemic thirst?
Sweating, vomiting, diarrhea, and blood loss (this is why a cookie and juice is given after blood donations)
Contains warm sensitive (30%), cold sensitive (5%), and other neurons (65%)
Preoptic area of the anterior hypothalamus
What is sensory specific satiety?
When we reject food that’s too similar to what we’ve been having. We want variety
Thirst that is caused by eating. The consumption of liquids while eating
Prandial thirst
Part of the brain that detects and responds to cooler temps. Shows more neuronal activity when the blood is colder
Posterior hypothalamus
How is hyponatremia prevented?
Taking in electrolytes during and before extreme endurance activities. Consumption of salty snacks before/during endurance activities
What are prostaglandins?
A product of the hypothalamus that raises our temp set point
What are the mechanisms of hypovolemic thirst?
Results from lower volume of interstitial fluid, blood, or both.
Lower blood volume is sensed by receptors in the heart and kidneys
The wall of the heart muscle contains baroreceptors that measure blood pressure
As blood volume decreases, blood pressure decreases as well
The kidneys contain blood flow receptors that also respond to changes in blood volume
What does hyponatremia cause?
Hypovolemic thirst, cell swelling, severe headache
How is food regulated?
Ebb and flow of nutrient absorption and use (diff patterns in burning energy), short term and long term energy needs (save energy for use later), and body weight set point
Disorder of insulin production diagnosed in childhood or early adulthood
Type 1 diabetes mellitus
What does a lesion to the OVLT cause?
Reduced drinking in response to salty solution
What do kidneys secrete in hypovolemic thirst?
Renin
What are the endothermic responses to warm temps?
Perspiration (human default), licking and panting (other animals), and blood vessels dilate near skin surface
What does a constant need for energy with feeding occurring intermittently show?
We have to function in low and high caloric settings
Signals that encourage food consumption
hunger/appetite
How should weight loss be approached and why?
Small gradual changes are more impactful than extreme changes due to set point. Your body could think you’re starving with large changes
What are the areas of the brain associated with satiety?
Ventromedial hypothalamus, paraventricular nucleus, and nucleus of he solitary tract
What do antidepressants and serotonin syndrome cause?
GI distress, high fever, hallucinations, and possibly death. Very rare
What happens to urine production in hypovolemic thirst?
It is reduced to conserve fluid
Solutions with a higher concentration of solutes outside the cell
Hypertonic (shrivels)
What are upper value, lower value and set point?
Upper: triggers a response to counteract the increase
Lower: triggers a response to counteract the decrease
Set point: ideal value
Whats the chemical signal to retain sodium?
Aldosterone
Levels of ghrelin and leptin in hunger and satiety
Hunger: leptin low and ghrelin high
Satiety: leptin high and ghrelin low
A complex carbohydrate used to store energy in the liver. Long term energy storage
Glycogen
What does the Zona Incerta do? Where is it?
Initiates drinking. If it is stimulated, the animal will drink no matter what. Located outside the hypothalamus
What are cytokines?
Inflammatory markers released by leukocytes
How does a fever work?
In response to reduced inhibition from the warm sensitive neurons, cold sensitive cells increase their output which results in a higher temperature set point
What do low leptin and insulin levels stimulate the release of?
Neuropeptide Y (NPY) and agouti-related protein (AgRP) from the arcuate nucleus
Thirst that is a response to low fluid level in the bodys cells due to diffusion
Osmotic thirst
What is the path temperature detection takes in the body?
Structural hierarchy from thermoreceptors to spinal cord through the brainstem to the hypothalamus
Three things in the body for assessing satiety
Stomach fullness, duodenal glucoreceptors, and cholecystokinin
Activates and directs behavior toward a goal. Imbalance in a state causes this. Has drive/push theories and incentive/pull theories
Motivation
What does the lateral hypothalamus do?
Participates in hunger
Disorder of insulin recognition by cells. Has an adult onset and obesity is a major risk factor
Type 2 diabetes mellitus
What happens to TSH and ACTH release in eating initiation?
Release is suppressed to slow metabolism
A pancreatic hormone that assists in moving glucose from the blood supply into body cells. Helps store glucose as glycogen
Insulin
Used for immediate energy, stored by adipose tissue, and causes release of hormone cholecystokinin (CCK) which is a satiety signal
Lipid/fat digestion
What is learned taste aversion?
Association of food with illness or poor nutrition
Sensory info from baroreceptors and osmoreceptors via vagus nerve
nucleus of the solitary tract
Signals that end food consumption
satiety
Direct sensing of blood and afferent sensory info from thermoreceptors in skin and coordinates thermoreceptors with behavioral responses to dissipate heat (panting, sweating, etc)
Preoptic area of the anterior hypothalamus
How is a fever triggered?
Pathogens activate leukocytes which release cytokines (inflammatory markers) which stimulate the hypothalamus which produces prostaglandins (raise our set point) which triggers a fever
What does the paraventricular nucleus do?
Involved in the regulation fo hunger, metabolic processes (body temp, fat storage, cell energy use)
What do amphetamines, cocaine, and MDMA (ecstasy) cause?
An increase in temperature. Dangerously high fevers in the case of MDMA
Whats the chemical signal to retain fluid?
Antidiuretic hormone (ADH)
What area of the brain fires more as temperature increases?
Preoptic area of the anterior hypothalamus
What are the endothermic responses to cold temperatures?
Shiver, blood vessels constrict, thyroid hormone increases to boost metabolic rate (use more energy from food), social huddling (usually in other animals)
What is learned taste preference?
Preference for flavor of food that contains necessary nutrients
What fluids make up the extracellular fluid?
Blood supply (7%) CSF (less than 1%) Interstitial fluid (surrounds cells 26%)
Animals with a body temperature that changes with the temp of the environment. More sensitive to what’s happening in the environment. Behaviors regulate temps
Ectotherms
What does the extracellular fluid contain higher concentrations of?
Na+ and Cl-
Sports drinks relationship with hyponatremia
Sports drinks are still hypotonic (less Na than the concentration of blood) so will not completely prevent hyponatremia
Where are glucoreceptors and what do they do?
Hindbrain in liver. Ones in liver influence insulin release by the pancreas. They monitor blood glucose to detect when it is low to let us know when we are hungry
What does ADH do and when is it released?
Prevents you from peeing to save body fluid. Released in hypovolemic thirst
Solutions with a lower concentration of solutes outside the cell
Hypotonic (swells)
What percentage of body fluid is extracellular?
33%
In hypothalamus, input from NST, SFO. Output to ZI
median preoptic nucleus
Broken down into amino acids and used by muscles and other tissues for growth and protein synthesis
Protein digestion
What are signals of hunger in the body?
Low blood glucose availability, lipostatic theory, and possible assessment of circulating amino acids
What is aldosterone and when is it released?
Save the sodium signal released by the adrenal glands in hypovolemic thirst
What happens to the parasympathetic division of the automatic nervous system during eating initiation?
It is activated
What does cellular dehydration (hypovolemia) result in the release of?
Antidiuretic hormone (ADH; vasopressin) from the pituitary gland
What factors in selecting food?
Taste, sensory specific satiety, leaned taste aversion, and learned taste preference
How is drinking stopped?
Fluid receptors in mouth, throat, and digestive system indicate enough fluid has been acquired
What is the normal body temperature for humans and does it change?
Each person has a different normal that fluctuates throughout the day. Usually between 97.16 and 98.24
How is drinking initiated?
Angiotensin II acts on subfornical organ (SFO). Nucleus of the solitary tract gets input from baro and osmoreceptors. NST and SFO communicates with median preoptic nucleus. Stimulation of zona incerta stimulates drinking
What does too little Na lead to?
Reduced blood volume and pressure
A pancreatic hormone that converts glycogen into glucose. Long term storage into immediate energy use
Glucagon
Animals that generate metabolic heat to maintain internal temperature. Internal temp doesn’t change much at all with outside temp
Endotherms
What is the central pathway of hunger?
- ) Glucose deficit sensed by liver via the vagus nerve (CN X)
- ) NST in the medulla
- ) Arcuate nucleus of hypothalamus and spreads out a bit when it gets to hypothalamus
- ) Release neuropeptide Y and agouti related protein in bloodstream
- ) Increase eating and reduce metabolism
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A dangerous condition in which Na levels drop to 10% or more below normal
Hyponatremia
This is a body response that is effective in fighting disease
Fever
What does the intracellular fluid contain higher concentrations of?
K+
What is pyrexia?
A fever
How is osmotic thirst detected?
Deficit detected by organum vasoculosum of the lamina terminalis (OVLT) in hypothalamus
When solutes break into ions when dissolved
Electrolytes
How is a response to osmotic thirst created?
OVLT detects deficit and deficit is communicated to median preoptic nucleus of the hypothalamus to the Zona incerta where drinking is initiated
What do NPY and AgRP do?
Communicate with the paraventricular nucleus (PVN) of the hypothalamus and the lateral hypothalamus (LH)
Levels of leptin and its relationship to weight loss
High leptin when full. We make plenty of leptin but more often have trouble responding to it
What drops as a function of time since last meal?
Insulin. Signaling its time to eat
When does type 1 diabetes mellitus usually occur?
Juveniles. It has an early onset
What does too much Na lead to?
High blood pressure
Actively defend certain values or set points (temp, fluid levels, metabolism, body weight, pH, hormones, and many more) and require effort to maintain
Regulatory systems
A type of simple sugar found in foods used for immediate energy use. Carbohydrate
Glucose
What percentage water is the body?
70%
Thirst that is a response to low blood volume because of a loss of extracellular water
Hypovolemic thirst
What are the neurochemicals associated with satiety?
Leptin found in blood when body fat levels are high
How is osmotic thirst caused?
Excessively high salt or sugar intake. Drinking a sugary drink with salty foods and needing another drink
A peptide synthesized in the pancreas and stomach that is released during fasting and stimulates eating behavior
Ghrelin
What is a fever and why does it happen?
A controlled increase in the core temp set point during an illness. Bacteria and viruses can’t survive the slight temp change. Letting a fever ride ends sickness quickest
What does stimulating the ventromedial hypothalamus do? Lesioning it?
Stim: stops eating
Lesion: Cant stop eating, obesity/higher set point, extremely picky eating habits (picking one thing and eating it all)
What is Raynauds disease?
Extreme blood vessel constriction in the cold. Cuts of circulation to fingers and toes
Part of the brain that detects and responds to warmer temps. Shows more neuronal activity when the blood is warmer
Preoptic area of the anterior hypothalamus
What are the three features of a homeostatic system?
A precisely defined set point, mechanisms for detecting deviations away from the set point (detect the problem by sampling current state), and internal and behavioral elements designed to regain the set point (fix the problem to get back to the set point)
What is a major risk factor of type 2 diabetes mellitus?
Obesity
What do neurons in the LH do in eating initiation?
Release melanin-concentrating hormone (MCH). Associated with higher order motivated behaviors leading to feeding. Projections throughout the cerebral cortex
What does leptin do? When can it be found in high levels?
Found in blood when body fat levels are high. High levels stimulate aMSH and CART to inhibit feeding
Molecules that have been dissolved in fluid. Electrolytes
Solutes
What is drive reduction theory of motivation?
Imbalance in a regulatory state causes motivation to get balanced. Take action to satisfy needs. Like a thermometer
Example of adaptations among species to maintain body temp
Ear size in foxes of different climates
What drops when fat stores are low?
Leptin levels. Signaling its time to eat
What does AgRP do in the lateral hypothalamus?
Blocks MC4 receptors
How does the way we think about what we are eating affect ghrelin and leptin release?
If we think something is supposed to be super filling, our ghrelin levels will drop lower and our leptin levels will rise after eating it even if it isn’t actually super filling
What is body weight set point mostly determined by?
Genetics
What do most homeostatic systems use?
Negative feedback
Responds to angiotensin II
subfornical organ
Why do people with pale skin turn red quickly in warm temperatures?
The blood vessels near the skin surface dilate in warm temps
Examples of homeostatic systems using negative feedback?
Hot temp: More sweating, less temp
Cold temp: More shivering, more temp
What does stimulating the lateral hypothalamus do? Lesioning it?
Stim: produces immediate eating behavior
Lesion: stops eating, starvation unless force fed
This area of the brain involved in temperature has and needs to have a weak blood brain barrier
Preoptic area of the anterior hypothalamus
What is cholecystokinin (CCK)?
A hormone that is a satiety signal for when we have had enough fat
Where is the OVLT and what does it contain?
Near the third ventricle. Contains many osmoreceptors
This occurs when compensating mechanisms can’t keep core temp within the normal limits. Higher risk in young children and older adults
Hyperthermia (heat stroke)
What does prandial thirst do?
Facilitates chewing and digestion
What do ghrelin and orexins do?
Stimulate feeding behavior
When the body temp falls too low
Hypothermia
What are external cues for hunger?
Time of day, sight and smell of food, or social setting
In midbrain, connections to motor areas, initiates drinking behaviors
Zona incerta
This happen during menopause as a result of decreasing estrogen
Hot flashes
A type of mechanoreceptor sensory neuron that is excited by stretch and inhibited by relaxation of the blood vessels
Baroreceptors
A peptide produced in the lateral hypothalamus that stimulates hunger (AKA hypocretin)
Orexin
What does secreted renin from the kidneys lead to?
Increased angiotensin II production
