lecture 14

Question 1

Extinction learning is often dependent on what

Answer 1

the neural activity in the prefrontal cortex

Question 2

what is the Role of the Ventromedial Prefrontal Cortex

Answer 2

Region of prefrontal cortex at base of anterior frontal lobes, adjacent to midline; plays an inhibitory role in expression of emotions

Many investigators believe that impulsive violence is consequence of faulty emotional regulation
• For most people, frustrations may elicit urge to respond emotionally, but people usually manage to calm themselves and suppress these urges

Question 3

what is the case of Phineas Gage

Answer 3

The PFC (Prefrontal cortex) has inhibitory connections with the amygdala which are responsible for suppressing emotional responses in social
In the mid 1800’s, Phineas Gage was a victim of a tragic construction accident.
§ An explosion sent a 3 cm thick, 90 cm long tamping rod through his face, skull and brain.
§ Before his injury he was a good natured, kind, responsible, well liked and respectable man.
§ After his injury, he became childish, irresponsible and thoughtless of others. He had severe temper outbursts and used profane language. He was unable to make plans or carry them out. He lost his job and was unable to keep a social network of friends.

Question 4

what is the Research with Humans with regard to anger, aggression and impulse control

Answer 4

Early experiences can certainly foster development of aggressive behavior, but studies demonstrate that heredity plays significant role
• Several studies found that serotonergic neurons play inhibitory role in human aggression
• For example, a depressed rate of serotonin release (indicated by low levels of the serotonin metabolite 5-HIAA in the CSF) are associated with aggression and other forms of antisocial behavior, including assault, arson, murder, and child beating. Drugs that increase the amount of serotonin in the synapse (e.g. Prozac) decreases irritability and aggressiveness

Question 5

explain RISKY BEHAVIOUR AND IMPULSE CONTROL and monkeys

Answer 5

The serotonin metabolite 5-HIAA was measured in the cerebrospinal fluid of young male rhesus monkeys, which were then tracked over 4 years.
The monkeys with the lowest levels of 5-HIAA were risk takers. They took dangerous unprovoked leaps between trees and were highly aggressive towards older, dominant males. They typically died early from attacks by stronger monkeys

Question 6

Damage to the vmPFC causes what

Answer 6

serious and often debilitating impairments of behavioral control and decision-making

Question 7

Damage to the vmPFC causes serious and often debilitating impairments of behavioral control and decision-making
• These impairments appear to be consequence of what

Answer 7

emotional dysregulation, as cognitive abilities are not strongly affected by damage to the vmPFC

Question 8

what are the PHYSIOLOGICAL REGULATORY MECHANISMS

Answer 8

System variable
set point
correctional mechanism
homeostasis
ingestive behaviour
negative feedback
satiety mechanism

Question 9

what is Homeostasis

Answer 9

Process by which body’s substances and characteristics (such as temperature and glucose level) are maintained at their optimal level

Question 10

what is ingestive behaviour

Answer 10

Eating or drinking

Question 11

what is System variable

Answer 11

Variable that is controlled by a regulatory mechanism

For example, temperature in a heating system.. if thermostat detects hotness it will stop the electric heater and if it is cold it will start the heater

Question 12

what is set point

Answer 12

Optimal value of the system variable in a regulatory mechanism

Question 13

what is correctional mechanism

Answer 13

In regulatory process, mechanism that is capable of changing value of system variable

Question 14

what is Negative feedback

Answer 14

Process whereby the effect produced by a correctional mechanism serves to diminish or terminate the corrective action
Characteristic of regulatory systems

Question 15

what is Satiety mechanism

Answer 15

Brain mechanism that causes cessation of hunger or thirst, produced by adequate and available supplies of nutrients or water

Question 16

Thirst occurs when there is either…

Answer 16

1) not enough blood circulating in the body (volumetric thirst) or
2) there is too much salt in the blood (osmometric thirst).

Question 17

what is Volumetric thirst

Answer 17

occurs when there is not enough blood circulating in the body, which is called hypovolemia. The heart needs a certain amount of blood to keep beating

Question 18

Hypovolemia causes what

Answer 18

volumetric thirst

Question 19

Hypovolemia causes volumetric thirst, which is why people feel an intense thirst after they lose lots of what

Answer 19

blood

Question 20

what are the components of volumetric thirst

Answer 20

renin
Angiotensin
Subfornical organ

Question 21

what is renin

Answer 21

Hormone secreted by kidneys that causes conversion of angiotensinogen in the blood into angiotensin

Question 22

what is Angiotensin

Answer 22

Peptide hormone that constricts blood vessels, causes retention of sodium and water, and produces thirst and salt appetite

Question 23

what is Subfornical organ

Answer 23

Small organ located at the junction between the lateral ventricles and the 3rd ventricle in the frontal lobe
Contains neurons that detect the presence of angiotensin in blood and excite neural circuits that initiate drinking

Question 24

what does Tonicity refer to

Answer 24

the relative concentration of dissolved molecules (solutes) on either side of a semipermeable membrane. It is used to describe the direction and extent of water diffusion across a (cell) membrane

Question 25

what are the three stages of Tonicity

Answer 25

Isotonic solution: | Hypotonic solution: Hypertonic solution:

Question 26

what is Isotonic solution

Answer 26

similar solute concentrations are present inside and outside the cell. The cell will neither gain nor lose water.

Question 27

what is Hypotonic solution

Answer 27

solute is less concentrated outside the cell than in, so water will enter the cell.

Question 28

what is Hypertonic solution

Answer 28

solute is more concentrated outside the cell than in, so water will leave the cell.

Question 29

Hypertonic solutions cause what

Answer 29

cellular dehydration (water leaves the cell).

Question 30

what are Osmoreceptors

Answer 30

neurons that detect interstitial solute concentration; The membrane potential of osmoreceptors and their release of neurotransmitter relate to their volume (cell size).

Question 31

Some neurons in the subfornical organ are what

Answer 31

osmoreceptors. Other neurons here are sensitive to angiotensin. Some neurons have both qualities

Question 32

Ingestion of hypertonic saline strongly activates what

Answer 32

the subfornical organ in humans in an FMRI machine

Question 33

The subfornical organ immediately returns to normal baseline activity upon what

Answer 33

``` drinking water (before water has reached the blood), which demonstrates the existence of a rapid feedback mechanism. ```

Question 34

Cold sensors in the mouth and sensory fibers in the stomach are part of what mechanism

Answer 34

the rapid feedback mechanism

Question 35

explain the effects of insulin and glucagon on glucose and glycogen

Answer 35

The pancreas detects blood glucose levels. When blood glucose levels are high, the pancreas releases insulin, which causes the body to store glucose as glycogen. When blood glucose levels are low, the pancreas releases glucagon, which causes the body to convert glycogen back into glucose. • Cells internalize glucose with a glucose transporter. The glucose transporter that neurons have always works. Non-neuronal cells however, have a glucose transporter that only works when insulin is present. They have a insulin-dependent glucose transported. • The insulin-dependence of the glucose transporter in non-neuronal cells means these cells can also use glucose for fuel when there is an excess of glucose around (signaled by insulin). When insulin is not around, non- neuronal cells have to use fatty acids for energy instead of glucose

Question 36

what is Glycogen

Answer 36

Polysaccharide often referred to as animal starch Stored in liver and muscle Constitutes the short-term store of nutrients

Question 37

what is insulin

Answer 37

Pancreatic hormone that facilitates 1) entry of glucose and amino acids into the cell’s of the body, 2) conversion of glucose into glycogen, and 3) transport of fats into adipose tissue

Question 38

what is Glucagon

Answer 38

Pancreatic hormone that promotes conversion of liver glycogen into glucose

Question 39

what is Triglyceride

Answer 39

Form of fat storage in adipose cells (fat cells). Constitutes the long-term store of nutrients Consists of molecule of glycerol joined with three fatty acids

Question 40

what is Glycerol

Answer 40

Substance (also called glycerine) derived from breakdown of triglycerides, along with fatty acids Can be converted by liver into glucose

Question 41

what is Fatty acid

Answer 41

Substance derived from breakdown of triglycerides, along with glycerol Can be metabolized into sugars by most cells of body except for brain

Question 42

what are the parts of metabolism

Answer 42

``` insulin Glycogen Glucagon Triglyceride Glycerol Fatty acid ```

Question 43

decrease in blood glucose causes the pancreas to do what

Answer 43

stop secreting insulin and start secreting glucagon

Question 44

The absence of insulin means what

Answer 44

that most of cells of body can no longer use glucose. Thus, all glucose present in blood is reserved for central nervous system.

Question 45

Although many factors influence feelings of hunger (sights and sounds, smells and tastes, time of day and habits, thoughts, etc...), a particularly influential signal comes from what

Answer 45

the stomach when it is empty

Question 46

An empty stomach (or, more accurately, an empty duodenum) is communicated to the brain by the stomach’s release of what

Answer 46

a peptide hormone called ghrelin

Question 47

Levels of circulating ghrelin increase with hunger and fall with satiation. Exogenous administration of ghrelin does what

Answer 47

increases food intake. aka makes you hungry

Question 48

WHAT STARTS A MEAL?

Answer 48

Ghrelin | Duodenum

Question 49

what is Ghrelin

Answer 49

Peptide hormone released by the empty stomach that increases eating Also produced by neurons in the brain

Question 50

what is Duodenum

Answer 50

First portion of small intestine, attached directly to stomach. The presence or absence of food in the duodenum regulates the release of ghrelin from the stomach

Question 51

WHAT STOPS A MEAL?

Answer 51

Gastric Factors Short-term satiety (fullness) signals are released by the stomach and duodenum immediately after eating, before food is digested . (Swelling of the stomach causes a bloated feeling, but that is different than feeling full.) • The most prominent among these are cholecystokinin (CCK) and PYY, which are secreted by the duodenum in response to food ingestion in proportion to the calories ingested. These and other satiety-related peptides correlate with feelings of fullness and inhibit food intake, but the effects are short lived. They mostly influence how long people eat for. (CCK also regulates gastric motility and causes the gallbladder to release digestive enzymes into the duodenum.) • The repeated administration of CCK and PYY to healthy individuals does not reliably cause sustained weight loss. It does decrease meal size, but the body will react with an increase in meal frequency.

Question 52

AFTER THE MEAL ENDS what heppens

Answer 52

The satiety produced by gastric factors and duodenal factors (CCK & PYY) is anticipatory (i.e. your cells haven’t received the nutrients yet). • These factors predict that the food in digestive system will, when absorbed, eventually restore system variables that cause hunger • Not until nutrients are absorbed from intestines can they be used to nourish the cells of body and replenish body's nutrient reservoirs • This stage of satiety appears to occur in the liver and pancreas, as they detect when food has been absorbed into the blood and is available to the body. • The satiety signal released by the pancreas is insulin, which is actively trafficked across the blood brain barrier. There are neurons in the hypothalamus that express insulin receptors and their activity reduces feelings of hunger. • The liver signals satiety through the vagus nerve

Question 53

In most people, body weight appears to be regulated how

Answer 53

over a long-term basis

Question 54

If a healthy animal is force-fed so that it becomes fatter than normal what happens

Answer 54

it will reduce its food intake once it is permitted to choose how much to eat

Question 55

what isLeptin

Answer 55

a circulating hormone that is secreted by adipocytes (fat cells). Leptin is thought to signal the size of peripheral energy stores in the body

Question 56

As fat cells (energy stores) grow and proliferate what happens to lepin

Answer 56

there is a concomitant increase in leptin levels in the blood stream. This leptin provides a negative homeostatic feedback signal that decreases hunger

Question 57

Exogenous administration of leptin does what to meal size

Answer 57

decreases meal size in healthy people

Question 58

Humans and animals can be born or become insensitive to leptin. A reduced ability to detect leptin levels increases what

Answer 58

hunger and causes obesity.

Question 59

Leptin receptors are located in many areas of the brain. | In the hypothalamus, leptin signaling does what

Answer 59

decreases food intake and increases metabolic rate, primarily by inhibiting AGRP/NPY neurons and activating POMC/a-MSH neurons in arcuate nucleus. Leptin also makes these neurons more sensitive to CCK and other satiety peptides

Question 60

Leptin receptors are also located on dopamine neurons that control what

Answer 60

the reinforcing value of stimuli, like food. Increases in leptin decrease the likelihood that people will desire (choose) to eat the same food again.

Question 61

what are The hedonic aspects of hunger

Answer 61

both the motivational and reinforcing properties of food fluctuate in accordance with hunger and available energy stores. Satiety or fullness reduces both the rewarding and reinforcing value of food. Hunger increases the rewarding and reinforcing value of food.

Question 62

what is Arcuate nucleus of the hypothalamus

Answer 62

Nucleus in base of hypothalamus that contains neurons highly sensitive to circulating levels of leptin. Contains AGRP/NPY neurons and POMC/a-MSH neurons, which are involved in feeding and metabolic rate

Question 63

what is Paraventricular nucleus (PVN) | of the hypothalamus

Answer 63

Nucleus of hypothalamus that receives inputs from arcuate nucleus. Contains oxytocin neurons that signal that body has adequate levels of leptin (fat)

Question 64

explain the Paraventricular Nucleus (PVN) of the Hypothalamus

Answer 64

The paraventricular nucleus (PVN) contains oxytocin neurons, whose activity signals that body has enough fat and inhibits hunger. If PVN neurons have a low firing rate, below some threshold, animals will feel intense hunger. Excess activity of PVN neurons does not prevent feeding triggered by other parts of the circuitry, so this region is thought to play a large role in low leptin-induced emergency feeding.

Question 65

what is the Prader-Willi Syndrome

Answer 65

Prader-Willi syndrome is a rare chromosomal abnormality in which up to 7 genes are deleted from chromosome 15. One of these genes is critical for the development/survival of oxytocin-containing neurons in the PVN. People with Prader-Willi syndrome are born with very low muscle mass and have little interest in eating. But later, between 2 and 8 years old, these people develop a heightened, permanent and painful sensation of hunger, a feeling of starving to death. Average life expectancy in the United States is 30; most die of obesity-related causes. People with this disorder have no sensations of satiety to tell them to stop eating or to throw up, so they can accidentally consume enough food in a single binge to fatally rupture their stomach.

Question 66

what are Emergency circuits

Answer 66

activated when a specific critical need to eat or not eat overrides energy homeostasis circuitry

Question 67

what are the 2 emergency circuits

Answer 67

Glucoprivation | Lipoprivation

Question 68

what is Glucoprivation

Answer 68

Dramatic fall in level of glucose available to cells (detected in liver and brain) Can be caused by a fall in blood level of glucose or by drugs that inhibit glucose metabolism

Question 69

what is Lipoprivation

Answer 69

Dramatic fall in level of fatty acids available to cells (detected in liver and brain) Usually caused by drugs that inhibit fatty acid metabolism

Question 70

what is Hypoglycemia

Answer 70

low blood sugar

Question 71

for hypoglycaemia....When the brain senses that it does not have enough glucose (sugar) to support normal brain function (via glucose-sensing neurons in various regions of the brain), it launches an emergency cascade of effects: explain them

Answer 71

Suppresses insulin secretion to keep sugar in the blood • Triggers glucose production in the liver • Slows energy expenditure (basal metabolic rate) and halts growth and reproduction related systems • Promotes a potent and sustained feeling of hunger

Question 72

Hypoglycemia-induced feeding overrides energy homeostatic mechanisms, and this does what

Answer 72

Hypoglycemia-induced feeding overrides energy homeostatic mechanisms, in that it can stimulate feeding irrespective of body fuel stores (indicated by leptin and insulin levels). • Excess insulin will also trigger this kind of eating, because insulin causes glucose to leave the blood and enter fat and muscle tissue

Question 73

explain Lipoprivation in its basic terms

Answer 73

Not enough fat

Question 74

explain Lipoprivation

Answer 74

When the brain senses dangerously low leptin levels, it believes the body has no stored energy (fat) to support the energy homeostasis system. So, it launches an emergency cascade of effects that are almost identical to those observed in response to low blood sugar: Glucose production is increased, insulin production is decreased, metabolic rate is slowed, and a profound hunger takes hold. Dangerously low levels of glucose (immediately available fuel) and dangerously low levels of fat (stored fuel via leptin signalling) trigger the same emergency feeding circuits that aim to raise blood glucose levels. Disruptions in insulin signaling results in high blood sugar (hyperglycemia), because the sugar is not trafficked from the blood and into fat and muscle tissue. Without treatment, this will cause progressive weight loss and a loss of body fat. Without fat cells to release the hormone leptin, leptin levels plunge. Low leptin will initiate a intense hunger (a feeding emergency) even if the person is hyperglycemic (too much sugar in blood).

Question 75

The system in overweight individuals seems to be doing what

Answer 75

actively defending elevated levels of body fat. Their bodies have an elevated leptin set point that they are trying to maintain, and they have a blunted response to increases in leptin levels

Question 76

The system in overweight individuals seems to be actively defending elevated levels of body fat. Their bodies have an elevated leptin set point that they are trying to maintain, and they have a blunted response to increases in leptin levels. .... what is this called

Answer 76

This is called leptin resistance

Question 77

In different populations of overweight animals, people have observed:

Answer 77

Ø a reduction in leptin’s ability to cross the blood-brain barrier Ø a reduction in the neuronal response to leptin signalling Ø a reduction in the downstream consequences of leptin-signalling neurons After several days of eating a cafeteria-style diet (high fat, high sugar), inflammation has been observed in the hypothalamic arcuate nucleus of rodents. This results in a decreased sensitivity to leptin. These animals require more leptin in the blood (more fat cells) to maintain their energy homeostatic set point.