PBSI 235 Exam 3 Review: Homeostasis, Sleep, and Emotions

Homeostasis

Process in which the body achieves a stable, balanced internal environment.

Set Zone

Range within which a physiological system can function.

Thermoregulation

Process by which body maintains an ideal temperature.

Preoptic area (POA)

Takes care of the physiological responses that raise body temperature in response to cold.

Shivering

Metabolic burn required for motion generates heat.

Constriction of blood vessels

Reduced blood flow makes the skin and fat more effective as insulation.

Lateral hypothalamus

Crucial for behavioral regulation of temperature.

Thirst

Motivational response to fluid loss which is required by normal processes like breathing, sweating, and urination.

Osmotic thirst

Triggered by increase in salt levels from urination or consuming salt.

Hypovolemic thirst

Decrease in the volume of bodily fluids triggered even if salt concentrations do not change.

Circumventricular organs

Contain osmosensory neurons, which can detect changes in the salt concentration in the cerebrospinal fluid.

Osmosis

Diffusion of solvent molecules across a permeable biological membrane.

Baroreceptors

Receptors located in the blood vessels of the kidney and heart that monitor changes in blood volume.

Vasopressin

Hormone released by the pituitary gland that tells kidneys to retain water.

Insulin

Allows glucose to enter muscles and liver cells to be used or converted into glycogen for short term storage.

High levels of insulin inhibit NPY neurons, which reduce hunger

Glucagon

Converts glycogen back into glucose when glucose levels in the blood fall.

Adipose tissue

Where glucose goes for long term storage when there is more than needed in the short-term.

Diabetes

Results in a failure of insulin to allow glucose to be taken into cells.

Type 1 Diabetes

Juvenile onset; pancreas stops making insulin.

Type 2 Diabetes

Adult onset; cells no longer respond to insulin.

Basal metabolism

The energy spent on basal metabolism goes to maintaining basic physiological functions.

Basal metabolism

level of energy use at rest

Metabolic adaptation

When energy intake decreases → The body becomes more efficient at using less energy (making it important for survival)

Hunger

the motivational drive to eat

Satiety

the feeling of being full/the absence of hunger

Arcuate nucleus

What monitors the levels of hunger and satiety-relevant hormones

POMC neurons

signal satiety when activated, inhibiting hunger

NPY neurons

signal hunger when activated, promoting feeding

Ghrelin

High levels of ghrelin activate NPY neurons, which stimulate hunger

Leptin

High levels of leptin inhibit NPY neurons and activate POMC neurons → reduces hunger and promotes satiety

GLP-1

Presence of food in the gut causes digestive organs to release GLP-1

GLP-1 stimulation

GLP-1 stimulates release of insulin from pancreas

Nucleus accumbens

What part of the basal ganglia is involved in motivation in both humans and rats

Mu-opioid receptor

What receptor do many neurons in the nucleus accumbens express

Bliss point

The amount of an ingredient needed to make a food maximally delicious

Sensory specific satiety

The decline in pleasantness associated with a food as it is eaten, compared to a food that has not been eaten

Biological rhythms

Periodic fluctuations in normal physiological processes that occur over different timescales

Circadian rhythms

fluctuations occurring in approx 24 hour period

Examples of circadian rhythms

1. Sleep/wakefulness 2. Hormonal concentrations in blood 3. Feeding

Zeitgebers

What syncs the internal clock with the external environment

Suprachiasmatic nucleus

What does the suprachiasmatic nucleus of the hypothalamus contain

Sleep patterns without SCN

They would become almost random

Period and cryptochrome

What genes are activated by the clock/cycle dimer

Inhibition by period/cryptochrome dimer

period/cryptochrome dimer (proteins) inhibit clock/cycle dimer → prevents it from activating period and cryptochrome genes

Clock/cycle dimer release time

Around 24 hours

Melatonin release gland

Pineal gland

EEG

EEG measures the combined activity of many neurons (brain waves) and differentiates the stages of sleep and wakefulness

Stages of sleep

1. Non-REM a. 3 phases i. Early: heart rate slows and muscles relax ii. Final: high amplitude waves and synchronized (non seizure) activity across the cortex 2. REM a. Rapid, darting movement of eyes b. Complete loss of muscle tension

Deepest phase of non-REM sleep

Slow wave sleep

Another name for REM sleep

Paradoxical sleep

Do animals show non-REM and REM sleep?

Yes!

Biological functions of sleep

1. Developmental a. Younger people sleep more and have a higher proportion of REM sleep b. Growth hormones tend to be released in slow wave sleep 2. Memory a. Rats show patterns of brain activity associated with maze they learned the day before

Where do lateral hypothalamus neurons release
orexin onto?

They release orexin onto neurons in the reticular formation

What do neurons in the ventrolateral preoptic area (VLPO) of the hypothalamus do?

They release GABA onto the neurons in the reticular formation → inhibiting it and decreasing wakefulness

What is Narcolepsy?

Overwhelming sleepiness that occurs suddenly and unpredictably. People with narcolepsy have lower numbers of orexin neurons.

Sleep paralysis

Brief inability to move before/after waking.

REM behavior disorder

No loss of muscle tension during REM sleep.

According to the locationist view, what is an
emotion?

Emotions are distinct states that correspond with specific sites in the brain
- Fast evaluation of circumstances → brain activates and produces emotion
- When these specific sites are activated → emotion is produced

What do emotions promote? Give 3 examples

Emotions promote survival
1. Threatening situations trigger fear → promote avoiding or defending to increase
survival
2. Rotting food triggers disgust → reduces contact with pathogens to increase survival
3. Offspring trigger parental love → increases parental investment to increase offspring’s survival

Limbic system structures

Anterior cingulate cortex, Hippocampus, Amygdala, Hypothalamus.

Location of the amygdala

Temporal lobe.

Effects of amygdala removal in monkeys

Caused bizarre emotional and motivational responses, less fear and aggression, docile, and abnormal food consumption.

Input to the amygdala

Amygdala receives input directly from sensory regions of the thalamus (low road) and cortex (high road).

Constructionist definition of emotion

Emotions are a mix of psychological components; they are the result of a combination of core affect and other psychological processes.

Evidence for constructionist approach

Regions that tend to be active in fMRI studies of any emotion; common series of structures become active.

Degree of brain region activity

Degree to which different brain regions are active across different emotional states; matter of degree differs.

Abulia

Disorder in which individual is incapable of making basic decisions; strong form of apathy, lack of willpower or drive.

Causes of abulia

Reduced emotional reactions, less intense feelings, reduced physiological responses to emotional stimuli; caused by damage to the anterior cingulate cortex (ACC).

Darwin's view of facial expressions

Darwin viewed that all humans produce the same/similar facial expressions in response to a core group of emotions.

Facial expressions in industrialized vs isolated societies

Good cross-cultural agreement among people from various industrialized societies about the meaning of many facial expressions; less agreement about meaning of facial expressions from people in more isolated, smaller societies.

Types of facial muscles

Superficial facial muscles create subtle movements; deep facial muscles create larger movements.

Control of facial muscles

Facial nerve and Trigeminal nerve.

Action units

Observable movements of individual muscles or groups of muscles; result from the contraction of a specific pattern of facial muscles.

Definition of stress

Physiological response to threatening/aversive stimuli.

Regulation of stress

Hypothalamus-pituitary-adrenal axis (HPA) regulates the hormonal component of stress.

Stress hormone

Cortisol; the HPA controls the release of cortisol from the adrenal gland.

Amygdala

Areas of brain (like the amygdala) send information about threats to the hypothalamus

Corticotropin-releasing factor (CRF)

Hypothalamic neurosecretory cells release corticotropin-releasing factor (CRF) into portal vein

Adrenocorticotropic hormone (ACTH)

CSF reaches pituitary gland → causes release of adrenocorticotropic hormone (ACTH) into blood

Cortisol

ACTH travels to adrenal gland → stimulates cortisol release

Negative feedback loop

System is a negative feedback loop → increase of cortisol decreases the release of CRF and ACTH

Sympathetic nervous system

Stress activates the sympathetic nervous system ('tells the body to burn energy'/'fight or flight')

Parasympathetic nervous system

Activation of the sympathetic nervous system inhibits the parasympathetic nervous system ('rest and digest')

HPA axis

Persistent activation of HPA axis can have harmful effects since it is designed to provide short term solutions → can cause negative health effects of chronic stress

Yokes

Yokes (no control) showed learned helplessness and showed effects of chronic stress → weight loss, ulcers

Masters

Masters (had control) control reduced stress response and inoculated them against future stressors

Medial prefrontal cortex (mPFC)

Medial prefrontal cortex (mPFC) → inhibits activity in regions like amygdala → which reduces stress response

Mood disorders

Disruptions/distortions in mood which significantly impair normal activity

Symptoms of depression

1. Persistent feelings of despair 2. Anhedonia → inability to take pleasure in activities one found pleasurable previously 3. Sleep and weight disruptions 4. Severe pessimism and suicidality

Genetics and depression

There is a strong genetic component in depression

Polygenic vulnerability

Vulnerability to depression is polygenic → multiple genes involved, not just one

Glucose levels in depression

At the baseline, subgenual cingulate takes up less glucose in depressed patients and more glucose in manic patients

Sleep alterations in depression

Reduction in slow wave sleep → can affect memory; REM sleep can occur immediately (usually occurs after non-REM sleep)

Cortisol in depression

Cortisol is higher in individuals with clinical depression

HPA dysregulation

HPA becomes dysregulated; Dexamethasone does not suppress the release of normal cortisol through negative feedback in individuals with depression

Drug treatments for depression

1. SSRIs → prevent serotonin reuptake 2. MAOIs → inhibit enzymes involved in breaking down neurotransmitters

Neurotransmitter deficiency hypothesis

Not everyone with depression responds to drugs; strong placebo effect for antidepressants; antidepressants have a big effect on neurotransmitter levels before they show benefits for clinical depression

Subgranular zone of the dentate gyrus

Contains dividing neural progenitor cells that can give birth to cells that will eventually become neurons, which are integrated into hippocampal circuits

Cortisol and neurogenesis

Cortisol inhibits neurogenesis; Monoamines promote neurogenesis

Cognitive Behavioral Therapy (CBT)

CBT: form of talk therapy where therapist helps client develop antidepressant cognitive strategies; identify self defeating thoughts and replace with affirming/therapeutic cognitive strategies; CBT + medication is more effective than either on their own