Brain and Behavior CH. 9

basal metabolism

energy used to maintain a constant body temperature at rest

• uses about 2/3 of our energy per day

• TWICE as much energy is used for temperature regulations than all other activities combined

homeostasis

in mammals, temperature regulation, hunger and thirst, are NEARLY homeostatic and not EXACTLY homeostatic

negative feedback

processes that reduce discrepancies from the set point

allostasis

adaptive way in which the body changes in response to changes in life/environment

ectothermic (poikilothermic)

animals with body temperatures that match their environment

• i.e. fish, lizards, cold bloodeds

endothermic (homothermic)

animals that can maintain body temperature of 37^o C or 98^o F

what brain region is critical for temperature control?

POA/AH

• preoptic chasm

• anterior hypothalamus (hypo cold)

we need POA/AH! (POWER)

how does POA/AH work

• monitors own temperature and receives input from temperature-sensitive skin and spinal cord receptors

  • also receives input from the immune system!

Suprachiasmatic N

circadian

Preoptic area

temperature control

Organum vasculosum laminae terminalis

osmotic pressure

Supraoptic and paraventricular N

release of vasopressin

Lateral preoptic area

drinking

Subfonical organ

stimulated by angiotensin II

• drinking

Laternal N

increase eating

Ventrmedial N

decrease eating

Ventral noradrenergic bundle

decreasing eating (bundle)

Paraventricular N

decrease eating (para N)

fever initiation

• bacteria and viruses trigger leukocytes to release cytokines

• cytokines attack intruders but also stimulate the [vagus nerve], which stimulates the hypothalamus to produce fever

newborn rabbit immature hypothalamus

• prefer a room warm enough to increase their body temperature in response to infection

  • it is behavioral!

when does fever get dangerous?

a fever above 39^o C is bad

• above 41^o C is life threatening!!!!

immune system delivers what to cause shivering, increased metabolism and fever

prostaglandins and histamines

what does POA/AH control mainly

controls sweating or shivering

the concentrations of chemicals in water determines the rate of all chemical reactions in the body

true

how is water conserved in humans

• excreting concentrated urine

• decreasing sweat and other autonomic responses

when your body needs water, the ______ gland releases ______ also known as antidiuretic hormone (ADH)

posterior pituitary gland / vasopressin

what does vasopressin do (thirst)

• raises blood pressure by constricting blood vessels

• enables the kidneys to reabsorb water and secrete highly [concentrated urine]

osmotic pressure (why does osmotic thirst happen)

body maintains combined conc. of solutes at fixed level of 0.15 M

• water tends to flow from low to high concentration

osmotic thirst

thirst due to increase in solute concentrations

• triggered by change in osmotic pressure

hypovolemic thirst

thirst due to overall loss of volume

• is based on blood volume becoming too low, so low that water and nutrients cannot enter body’s cells

where do neurons detect osmotic pressure (osmotic thirst)

• receptors around 3rd ventricle

• Organum Vasculosum Laminae Terminalis (OVLT)

• Subfornical organ: near 3rd ventricle

• receptors in periphery: stomach, intestine (detect high sodium)

where are signals from osmotic pressure detectors relayed to

relayed to [supraoptic nucleus] and [paraventricular nucleus] of the hypothalamus that control the rate at which the posterior pituitary gland releases vasopressin (ADH)

• also relayed to lateral preoptic area (drinking)

summary of osmotic thirst diagram

baroreceptors (real flesh and meat stuff)

receptors attached to large veins that determine the pressure of blood returning to the heart

baroreceptors trigger the release of what hormones?

vasopressin and angiotensin II

(hypovolemic thirst) when blood volume decreases, the kidneys release the hormone _____ which splits a portion off ______ (a large protein) to form ________ which is then turned into _______

renin / angiotensinogen / angiotensin I / angiotensin II

what does angiotensin II do?

constricts blood vessels in order to reverse loss of blood volume

• stimulates subfornical organ (SFO) to increase drinking

what does angiotensin II stimulate?

stimulates neurons near the 3rd ventricle

• it is also a neurotransmitter (released by hypothalamus)

animals with osmotic thirst prefer:

pure water

animals with hypovolemic thirst prefer:

slightly salty water

sodium-specific cravings

caused by release of [aldosterone] which causes the kidneys, salivary glands and sweat glands to conserve sodium and excrete more watery fluids than usual

• develops automatically to restore solute levels in blood

• due to bleeding or excessive sweating

big mac diagram

• beef patty: protein, triglyceride, neutral fat

• lettuce: cellulose

• cheese: protein trigylceride

• pickles: cellulose, starch

• onions: cellulose, starch

• bun: starch

25 g protein

28 g fat

47 g carbohydrates

540 calories in total!

the ______ tract provides the body with a continual supply of water electrolyte and nutrients

alimentary

what controls the alimentary tract

local, nervous, and hormonal systems

digestion

• begins in mouth by saliva

• esophagus => stomach, HCl and enzymes digest proteins

• [pyloric sphincter] allows food to periodically enter intestines

• enter small intestines (main site of nutrient absorption into bloodstream)

• nutrients carried by blood to cells in body

• large intestine absorbs water and minerals and lubricates remaining materials for excretion

why lactose intolerance happen

mammals lose ability to metabolize lactose due to decreased levels of lactase

sham feeding experiments

everything an animal eats leaks out of a tube connected to the stomach / esophagus do NOT produce [satiety]

main signal to stop eating

distention of the stomach

• [vagus nerve] carries info to brain regarding stomach wall stretching, is a MAJOR basis for [satiety]

splanchnic nerves

convey info about nutrient contents of stomach

• carries impulses between the spinal cord and digestive organs

duodenum and satiety

glucose produces satiety through receptors in the duodenum or by causing it to release hormones with satiating effect

cholecystokinin (CCK)

hormone released by duodenum to inhibit appetite by:

• closing the sphincter muscle between stomach and duodenum and causing stomach to hold contents and fill faster

• stimulating vagus nerve to send a message to hypothalamus that releases a similar chemical

insulin role in hunger

facilitates entry of glucose in bloodstream into body’s cells

glucagon

stimulates liver to convert stored glycogen into glucose

diabetics eat ____ food than usual but lose weight because their body’s cells are receiving ____ glucose due to poor insulin blood levels

more / little

obese people produce ___ insulin than people of normal weight

these levels of insulin cause more food than normal to be stored as fat, and causes quicker appetite return after a meal

more insulin

leptin

a peptide that signals the brain to increase or decrease eating

• low leptin = HUNGRY

• high leptin = do NOT necessarily decrease hunger, but increases physical and immune system activity

leptin and obese people

most people are obese because they are less sensitive to leptin

• some people are obese because genetic inability to produce leptin

obesity due to constant overeating damages the endoplasmic reticulum in neurons of hypothalamus

• leads to decreased leptin sensitivity

• physical activity repairs endoplasmic reticulum

arcuate nucleus

part of the hypothalamus containing two sets of neurons

• neurons sensitive to hunger signal

• neurons sensitive to satiety signal

neurons of the arcuate nucleus specifically sensitive to hunger signals receive input from:

• taste pathways

• axons releasing neurotransmitter [ghrelin]

  • neurotransmitter in brain and hormone in stomach to trigger contractions

Prader-Willis syndrome

genetic condition marked by mental retardation, short stature, and obesity

• Ghrelin is x5 higher than normal!

melanocortin

neuropeptide responsible for limiting food intake

• people with mutated gene for the receptors melanocortin overeat and become obese

input to the satiety-sensitive cells of the [arcuate nucleus] include signals of both long-term and short-term satiety:

• distention of intestine triggers neurons to release CCK

• blood glucose and body fat increase blood levels of the hormone insulin

• some neurons release a smaller peptide related to insulin as a transmitter

• leptin provides additional input

output from the arcuate nucleus excites the ______ of the hypothalamus

excites paraventricular nucleus

paraventricular nucleus is part of the hypothalamus that _____ the lateral hypothalamus

inhibits latereal hypothalamus

lateral hypothalamus is important for feelings of what?

hunger and satiety

input from the hunger-sensitive neurons of the arcuate nucleus is _______ to both the paraventricular nucleus and the satiety-sensitive cells of the arcuate nucleus

inhibitory to both paraven, and satiety sens. cells

inhibitory transmitters

GABA, neuropeptide Y (NPY), and agouti-related peptide (AgRP)

NPY and AgRP are ___________ that block the satiety action of the paraventricular nucleus and provoke _______

inhibitory transmitters / overeating

output from the paraventricular nucleus acts on the _________

acts on the lateral hypothalamus

lateral hypothalamus controls what and alters what?

controls insulin secretion and alters taste responsiveness

orexin

secreted by lateral hypothalamus

• increases persistence in seeking food

• responds to incentives and reinforcement in general

what if an animal had damage to the lateral hypothalamus? why?

the animal would refuse food and starve unless force fed

1. axons to NTS => change taste sensation and increase salivation

2. axons to forebrain increase ingestion and swallowing

3. activate DA neurons => reinforce behaviors

4. axons to spinal cord, control digestive secretion

damage to the ventromedial hypothalamus leads to what? why?

leads to overeating and weight gain (no decrease in hunger because they consume bitter foods far less than normal)

1. eat normal sized but unusually frequent

2. increased stomach motility and secretions

3. lasting increase of insulin => store in fat

what happens when there is damage to the ventral noradrenergic bundle?

excess eating and increased body weight

paraventricular nucleus (PVN) rats

if damaged, rats eat larger meals rather than more frequent meals

is there a weak or strong relationship between depression and weight gain

weak relationship

a high-fat diet before birth can lead to offspring born with a ______ than average lateral hypothalamus

larger than average

when did obesity increase sharply in america?

in the 1970’s due to high use of fructose, large foods, etc

_________ has replace __________ and decreases meal sizes and binge eating by blocking reuptake of _______ and ________

sibutramine / fenfluramine

serotonin / norepinephrine

Orlistat

prevents intestines from absorbing fats

gastric bypass surgery

removal of part of the stomach

• decreased stomach size allows greater distention of stomach to produce satiety

what percentage of adolescent females are bulimic

10%

obesity risks/symptoms

• high blood pressure, high cholesterol

• shortness of breath

• eating in big bites with no pleasure

bulimia risks/symptoms

• binging and purging

• dry skin/hair

• swollen glands from vomiting (chipmunk cheeks)

• laxative addiction

• stomach rupture

• dental problems

anorexia nervosa risks/symptoms

• dry cold skin, downy hair on skin

• insomnia, hyperactivity

• heart failure

• kidney failure

• low protein stores

• digestive problems

• electrolyte imbalance