Brain and Behavior Exam 3: Chapter 9, 10, 11

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Set point

a single value that the body works to maintain

Negative feedback

processes that reduce discrepancies from the set point. Much of motivated behavior can be described as this.

Allostasis

refers to the adaptive way in which the body anticipates needs depending on the situation. Helps avoids errors and not just correct them.

Homeostasis

refers to temperature regulation and other biological processes that keep certain body variables within a fixed range.

Temperature regulation

One of the body’s biological priorities. Maintaining this requires twice as much energy as all other activities combined

Basal metabolism

Energy used to maintain a constant body temperature while at rest

Poikilothermic (ectothermic)

idea that the body temperature matches
that of the environment because of lack of internal regulation. Amphibians, reptiles, and most fish have this aka cold blooded.

Homeothermic (endothermic)

use of internal physiological mechanisms to maintain an almost constant body temperature. Characteristic of mammals and birds through sweating, panting, and shivering. aka warm blooded

Poikilothermic animals

Death will occur if body temperature drops below freezing. Ice crystals form in cells and blood

The Advantages of Endothermy

Mammals evolved to have a constant temperature of 37 ̊C (98 ̊F). Muscle activity benefits from being as warm as possible. Ready for vigorous activity

preoptic area/anterior hypothalamus

receives input from temperature
receptors throughout the body. Heating in this area leads to panting or sweating; cooling leads to shivering (responses)

Prostaglandins & histamines

trigger fever, shivering, metabolism.

Fever

raised set point for body temperature to slow bacterial growth, Boosts immune response.
Risks: 39°C (103°F): harmful and 41°C (109°F): life-threatening

When you need water…

axons from the hypothalamus modify the
responses of more than half the cells in the cortex to increase their responses to any signal of water availability

Sufficient fluid

needed in circulatory system

Vasopressin (ADH)

Released by posterior pituitary. Constricts blood vessels (raises BP). Promotes water reabsorption in kidneys. Produces concentrated urine

Osmotic thirst

results from eating salty foods

Hypovolemic thirst

a thirst resulting from loss of fluids due to bleeding or sweating

The higher concentration of solutes outside the cell

results in osmotic pressure, drawing water from the cell to the extracellular fluid

Eating salty food

Causes sodium ions to spread through the blood and extracellular fluid of the cell. Certain neurons detect the loss of water and trigger osmotic thirst to help
restore the body to its normal state.

The brain detects osmotic pressure from

Receptors around the third ventricle; The OVLT (organum vasculosum laminae terminalis) and the subfornical organ (SFO) with sodium content of the blood. Receptors in the periphery, including the stomach and digestive tract

Receptors also relay information to the ____

lateral preoptic area, which controls drinking.

Low blood volume

kidneys release enzyme renin which helps form angiotensin I. Other enzymes convert that into angiotensin II

Like vasopressin, angiotensin…

constricts blood vessels to compensate for a drop in blood pressure

Angiotensin II

stimulates neurons subconical that release angiotensin II as a neuromodulator.

Animals with hypovolemic thirst

Prefer slightly salty water

Animals with osmotic thirst

Prefer pure water 

Sodium-specific hunger

strong craving for salty foods, Develops automatically to restore solute levels in the blood

When the body’s sodium reserves are low…

the adrenal glands release the hormone aldosterone that causes the kidneys, salivary glands, and sweat glands to retain salt.

Leptin

Hormone released when fat stores are high to suppress hunger

POA/AH (preoptic area/anterior hypothalamus)

Primary site for body temperature regulation

Aldosterone

Hormone that signals kidneys to retain salt

CCK (cholecystokinin)

Hormone released from the duodenum promoting satiety

Vasopressin (ADH)

Hormone that constricts blood vessels and promotes water retention

Arcuate Nucleus

Hypothalamic region containing hunger- and satiety-sensitive neurons

 Osmotic Thirst Sequence

Eat salty food

Cells lose water → osmotic pressure increases

OVLT/SFO detect imbalance

Vasopressin released

Drinking restores balance

Female Hormonal Cycle

FSH stimulates follicle growth

Estradiol rises

LH/FSH surge → ovulation

Corpus luteum releases progesterone

If no fertilization → hormone levels drop → menstruation

Stress-Response Pathway (HPA Axis)

Stress → Hypothalamus releases CRH

Pituitary releases ACTH

Adrenal cortex secretes cortisol

Cortisol feeds back to suppress CRH/ACTH

Hydrochloric acid and enzymes in the stomach digest____

proteins 

Enzymes in the small intestine digest___

proteins, fats, and carbohydrates

The large intestine absorbs___

water and minerals

The vagus nerve

Also known as cranial nerve X. Conveys information about the stretching of the stomach walls to the brain

Duodenum

Part of the small intestine. Site of initial absorption of significant amounts of nutrients. Distention of this can also produce feelings of satiety. It also releases the hormone cholecystokinin (CCK), which regulates hunger.

Glucose

Main product of digestion. Important source of energy for the body and nearly the only fuel used by the brain. Insulin and glucagon regulate the flow of this into cells.

If insulin level stays constantly high:

Blood glucose drops and hunger increases in spite of high insulin levels. Food is rapidly deposited as fat and
glycogen. Causes weight gain

Melanocortin

chemical important in limiting food intake. Deficiencies of this receptor lead to overeating

Input from the hunger cells of the arcuate nucleus:

Inhibits the paraventricular nucleus which, in turn, inhibits the lateral hypothalamus

Men may spread genes by:

Committing to one partner and helping raise offspring or mating widely, hoping others raise the children.

Women may benefit from multiple mates by:

Ensuring reproduction if one partner is infertile. Gaining more resources or “trading up”

Both men and women prefer a romantic partner that is…

healthy, intelligent, honest, kind, and physically attractive.

Because males have only one X chromosome…

a recessive gene on the X chromosome shows its effects more often in males than in females

Klinefelter syndrome

characterized by an XXY pattern, or less commonly XXYY or XXXY. The appearance is masculine, but most individuals are infertile.

Turner syndrome

characterized by an X chromosome and no second sex chromosome, or just part of a second X chromosome, or one X in some cells and two Xs in others. Feminine appearance, and almost always self-identification as female

Emotional situations arouse___

the autonomic nervous system

Most situations evoke___

a combination of sympathetic and
parasympathetic arousal.

Pure autonomic failure

Output from autonomic nervous system to body fails. People with this condition report feeling same emotions, but less intensely. People with damage to the right somatosensory cortex have typical
autonomic responses to emotional music but report little subjective
experience.

What does pure automatic failure suggest?

autonomic responses and subjective experience are not always closely connected.

Heart rate and breathing rate increase
with…

he intensity of an emotion. They do not distinguish fear from anger, or any other pair of emotions.

could you identify anyone’s emotion
by measuring autonomic activity?

no

Limbic system

located around the thalamus, is central to emotional processing

Disgust is…

the only emotion strongly tied to a specific brain region: the right temporal parietal junction. Insular cortex’s role in flavor perception

emotions exist along…

dimensions (e.g., pleasure vs displeasure, intensity, complexity) rather than as discrete categories.

Behavioral Activation System (BAS)

associated with the left hemisphere (frontal and temporal lobes) and linked to approach behavior (happiness or anger).

Behavioral Inhibition System (BIS)

associated with the right hemisphere (frontal and temporal lobes) and linked to inhibiting impulses and resolving conflict between drives.

greater left frontal cortex activity

tend to be happier and more extraverted

greater right hemisphere activity

typically more withdrawn, cautious, and prone to negative emotions

Facial expressions

similar across cultures, supporting
the idea of basic emotions. Blind individuals still show typical emotions expressions, suggesting they are innate. People can match expressions to emotions better than chance worldwide.

We rarely identify emotions from facial expressions alone, what else do we use?

body posture 

Contemplating moral decisions activates…

prefrontal cortex and cingulate gyrus

People with strongest autonomic arousal least likely to…

make decision to kill one person to save five others

Moral decisions

seldom made rationally. One decision or the other just “feels” right. We rationalize after decision has been made

fMRI studies show:

Different brain areas process utilitarian and emotional aspects separately. Ventromedial prefrontal cortex integrates both to guide decisions.

Prefrontal cortex damage leads to:

Less emotional consideration in decisions. Greater likelihood of choosing the utilitarian option (e.g., kill one to save five)

Individual differences in aggressive, violent, or antisocial behavior
depend on…

hereditary and environment 

MAOA gene

low activity form shows a link to
aggression

What is Impulsiveness and aggressive behavior linked to?

low serotonin release

Serotonin turnover

The amount of serotonin that neurons released, absorbed, and replaced.  Measured by the concentration of 5-HIAA in the cerebrospinal fluid. Many studies use blood samples to measure the concentration. Blood serotonin levels and brain serotonin levels don’t correlate too well.

what is low serotonin turnover in humans linked to?

violent behavior, including arson and
violent suicide.

Moro reflex

Built in fear, like a sudden loud noise causes newborns to arch their backs, briefly extend their arms and legs, and cry

What can be used as a behavioral measure of anxiety?

Startle reflex. It is also more vigorous if already tense.

amygdala responds most strongly…

when a facial expression is difficult to interpret. Shown through fMRI studies

Urbach-Wiethe disease

rare genetic condition that causes calcium to accumulate in the amygdala until it wastes away

Case study of person called SM

Experiences fearlessness, Correctly drew faces with various emotions but
had trouble drawing a fearful face, Did not generally look at people’s eyes, Lack of fear is dangerous to her.

Amygdala damage

affects the ability to recognize facial expressions of fear or disgust. When recognized, rated as less intense than other people

Panic disorder

Frequent periods of anxiety and occasional attacks of rapid breathing,
increased heart rate, sweating, and trembling. More common in women than men, and in adolescents and young adult

The HPA axis

the hypothalamus, pituitary gland, and adrenal cortex. Dominant response to prolonged stressors. 

B-cells

leukocytes that mature in the bone marrow and secrete antibodies

Psychoneuroimmunology

Deals with the way experiences alter the immune system. Also examines how the immune system influences the central nervous system

In response to a stressful experience

he nervous system activates the
immune system. Increases production of natural killer cells, leukocytes and cytokines. The cytokines combat infections but also trigger prostaglandins.