Feeding Flashcards
Unlearned and learned components of feeding regulation
some commonents of feeding are innate, like suckling, others we learn
What elicits eating behaviors?
sensory experiences
Motivation types for eating
- motivation reigns supreme for eating/drinking
- “do i want the food” (incentive motivation) vs “do i need the food”
pleasure driven motivation components
- incentive motivation
- flavors, reward, hedonic tone (ability to feel pleasure)
Homeostasis driven motivation components
- Do I need the food?
- glucose levels, proteins, fats, salts
What is homestasis and what are some examples of it in the body?
- Acheiving and maintaining physiological balance
- Energy, water, temperature, oxygenation
What is another way to describe homeostasis?
- maintaining the set point
how does the body maintain the set point?
- monitors physiological mechanism
- includes blood glucose, body fat, salt levels, etc and compares to set point
What behaviors are encouraged if deficient in terms of homeostasis?
- encourage seeking/feeding
- big difference between a little hungry after class vs. extremely hungry/starving if you get lost while hiking
What behaviors encouraged to maintain set point when body is in surplus (in terms of homeostasis)?
- suppress seeking/feeding
- negative feedback regulation
What are redundancies?
- multiple mechanisms of maintaining homestasis so if something goes wrong, there are systems in place to compensate
What are the three parts associated with thermoregulation?
- Afferents: skin surface, body core, hypothalamus/PONeural
- Neural regions: spinal cord, brainstem, hypothalamus/POA
- Effectors: behavioral responses (shivering/heat seeking and avoiding behaviors) as well as autonomic responses (vasoconstricton/dilation, sweating, respiration, brown-fat stimulation, thyroid hormone secretion)
What does POA stand for and where is it located?
preoptic area of the hypothalamus
thermoregulation
What do afferents do?
- pick up info and send to neural regions
thermoregulation
Neural regions
- goes to spinal cord, ascends to the brainstem, and into the hypothalamic area
Effectors
- behavioral: shivering and heat seeking/avoiding behaviors
- autonomic: vasodilation/constriction, respiration, sweating, brown-fat stimulation, thyroid hormone secretion
thermoregulation
responses to cold
- increased thyroid activity (thyroid hormone increases metabolism)
- metabolism of brown fat
- constriction of cutaneous blood vessels
- shivering of muscles
thermoregulation
responses to heat
- accelerated respiration
- perspiration
- dilation of cutaneous vessels
thermoregulation
What happens if the preoptic area of the thalamus is lessioned?
- physiological responses are impaired, without disruption to behavior
- inability for body to adapt/regulate
thermoregulation
What happens if you lesion the lateral hypothalamus?
- abolishes behavioral regulation, but does not affect physiological responses such as shivering
What is osmolality?
- the number of particles (electrolytes/salts) per unit volume of water
What is an isotonic salt solution?
- for most mammals and humans: .9% NaCl
- this is .9 grams NaCl in 100 mL of water
hypertonic
more salt than an isotonic solution
hypotonic
less salt than an isotonic solution
How does water move/in out of cells?
- osmosis
- if salt added , water rushes in to dilute
- if salt removed, water rushes out
Circumventricular organs: Subfornical organ and Organum vasculosum of the lamina terminalis
- on the third ventricle
- subfornical organ and OVLT is very important for monitoring thirst
- sensitive to how salty the blood is, osmoreceptors
- BBB very thin around the OVLT and SFO, allowing this parts of the brain to monitor very efficiently
Osmotic thirst
- extracellular compartment filled, but intracellular compartment does not have enough water
- high salt concentration (too much!) in extracellular compartment causes water in intracellular compartment to leave (flows out of cells)
- caused by regular water loss (respiration, persipiration, urine) or eating something salty
What responds to salt levels?
osmoreceptors
osmotic thirst from neuronal perspective
- osmosensory neurons in hypothalamus- neurons have osmoreceptors
- cells shrink based on water content, ion channels open, action potentials
- triggers osmotic thirst
- vasopressin release to reduce urination
- neurons that directly initiate drinking behaviors are signaled
What is hypovolemic thirst?
- too little volume of extracellular fluid due to large water loss (vomiting, hermorrage, diarrhea)
- lose water and salts
Which type of thirst is characterized by salt and water loss?
hypovolemic
What happens during hypovolemic thirst from a bio/hormone perspective?
- blood pressure drops causing…
- Baroreceptors (in blood vessels) signal to brain via autonomic nervous system and kidney
- Renin (from kidneys), then angiotensis II (in blood)
- vasopressin is released
- hypovolemic thirst triggered (eat salty food and drink water)
- reduces urination and increased blood pressure
hypovolemia definition
reduced blood pressure
What do baroreceptors measure?
blood pressure
hypovolemic thirst process in order (off of diagram)
- kidney baroreceptors-renin-angiotensin II
- Subfornical organ
- Preoptic area
- hypothalamic thirst network-drinking
- supraoptic nucleus/paraventricular nucleus- water conservation via vasopressin release
Satiety- an anticipatory response
- more satiety when water given through mouth/throat vs. stomach
- when able to drink but water diverted via esophagus rats keep drinking
- drinking is stopped in anticipation of correcting the extracellular volume and/or osmolality
- the cessation of one signal alone will not stop thirst; this redundancy safeguards against dehydration.
short term energy storage
- glycogen in muscles and liver
- you can convert glycogen to glucose using glucagon
how is long-term energy stored?
as adipose tissue
Does insulin cause us to feel sated?Why?
- low blood insulin leads to hunger
- high blood insulin also leads to hunger since it causes hypoglycemia (low blood sugar)
Do blood glucose levels cause us to feel sated?
- no
- people with untreated diabetes have high blood sugar levels, but are hungry
What causes us to feel sated?
multiple hypothalamic systems
What happens if you damage the Ventromedial hypothalamus?
- hyperphagia (over eating)
- a new set point that is higher
What happens if you damage the lateral hypothalamus (LH)?
- aphagia (inability to eat)
- then new set point (lower set point)
body “warns” hypothalamus ab nutrient surplus/deficiency
Leptin
- released by fat cells into blood, allow for monitoring of body energy reserves
- without it rats keep eating and become obese
- both excitatory and inhibitory
body “warns” hypothalamus ab nutrient surplus/deficiency
Insulin
- released by pancreas into blood, allows for monitoring of blood glucose levels
- inhibitory
body “warns” hypothalamus ab nutrient surplus/deficiency
Ghrelin
- released by stomach into blood while fasting, appetite stimulant
- excitatory
body “warns” hypothalamus ab nutrient surplus/deficiency
PYY(3-36)
- released by intestines into blood while ingesting food, appetite suppressant
- inhibitory
hypothalamic circuits for feeding
What does the NST do? Where is it located?
- the nucleus of the solitary tract (NST) in the brainstem receives and integrates appetite signals from many sources, some via the vagus nerve
hypothalamic circuits for feeding
What is the arcuate purpose?
- hypothalamic mechanisms integrate appetite signals from the arcuate
body “warns” hypothalamus ab nutrient surplus/deficiency
Orexigenic neurons
- of the lateral hypothalamus (LH)
- act to increase appetite and food intake
body “warns” hypothalamus ab nutrient surplus/deficiency
Anorexigenic neurons
- of the paraventricular nucleus (PVN) act to decrease appetite and feeding
What does OVLT osmosensory neurons detect?
- osmotic thirst (high solute concentration)
What does the subfornical organ detect?
- Angiotensin II (hypotvolemic thirst/low volume)
