Psyc 302 Exam 3

Diabetes

Insulin: a hormone secreted by the pancreas that causes cells to absorb glucose.

Diabetes Type 1

Congenital, autoimmune disease. Immune system kills cells in pancreas that

secrete insulin, insulin dependent diabetes

Diabetes Type 2

Late onset, insulin receptors on cells become resistant to insulin, associated withobesity, insulin resistant diabetes

How does stress complicate diabetes?

1) Stress causes even more glucose to pour into the circulation

2) Stress promotes insulin resistance

Type 1: difficult to balance blood sugar

Type 2: worsens syndrome

What problems can arise with chronic stress?

Irritable Bowel Syndrome

Irritable Bowel Syndrome

Symptoms:

1) Stomach pain relieved by defecation

2) Diarrhea or constipation

How does stress increase risk of getting Irritable Bowel Syndrome?

Repeated turning on and off of the digestive system results in loss of coordination of the components ofthe system

Peptic Ulcer

Ulcer of the stomach or portion of the esophagus or intestine immediately bordering the stomach

Caused by Helicobacter pylori

How does stress increase risk of getting a peptic ulcer?

Weakening of the stomach walls and suppressed immune system

Effects of stress on growth

Severe prolonged stress during childhood can lead to stunted growth

How does severe stress stunt growth?

1) Reduced release of Growth Hormone Releasing Hormone from the hypothalamus

2) Increased release of Growth Hormone Inhibiting Hormone

3) Reduces sensitivity to growth hormone

4) Fail to absorb nutrients

What is the critical variable in child neglect that leads to stunted growth?

Active touching

Michael Meany rat licking study

amount of licking and touching during early postnatal development effects stress reactivity in adulthood through methylation of glucocorticoid receptor gene promotor

Definition of stress

The physiological response to a physical, mental or emotional challenge, or

perceived challenge that activates the sympathetic nervous system and the HPA axis

Why Zebras Don't Get Ulcers

Why Zebras Don't Get Ulcers by Robert Sapolsky explains how chronic stress, common in humans due to psychological worries, leads to stress-related diseases like ulcers, heart disease, and depression, while animals like zebras only experience acute stress for immediate threats and then shut it off

Parasympathetic (Rest and Digest)

Slows heart beat

Stimulates digestion

Penile erection

Vaginal lubricatio

Sympathetic (Fight or Flight)

Adrenalin rush

Increases heart beat

Inhibits digestion

Dilates lungs

Ejaculation

Orgasm

Hypothalamic-Pituitary-Adrenal axis

(HPA axis)

Step 1: You feel stressed and hypothalamus releases CRH

into a private circulatory system linked to the pituitary gland

Step 2: CRH causes pituitary to release ACTH

CRH binds to receptors in the pituitary gland which causes the pituitary to release adrenocorticotropin releasing hormone (ACTH) into the blood
Step 3: ACTH causes adrenal glands to release glucocorticoids

ACTH binds to receptors on adrenal glands which causes them to release glucocorticoids into the blood

Glucocorticoids

stress hormones

are steroid hormones (because of their molecular structure)

Other steroid hormones include testosterone, estrogen, progesterone.

Cholesterol is also a steroid

Cortisol

is most well known glucocorticoid

Glucocorticoids bind to receptors all over the body and in the brain to cause changes (the stress response)

What do glucocorticoids do?

Energy mobilization

Storage —> Glycogen, Fat, Protein

Stress converts to usable form: Glucose and acetyl CoA

Effects of stress on reproduction

Step 1: Luteinizing Hormone Releasing Hormone (LHRH) released from the hypothalamus also known as gonadotropin releasing hormone (GnRH)

Step 2: causes pituitary to release the gonadotropins, Luteinizing

Hormone (LH) and Follicle Stimulating Hormone (FSH)

LH works synergistically with FSH:

In males to stimulates the testes to release testosterone and produce sperm.

In females, regulates menstrual cycle, stimulates the ovaries to release estrogen, produce and release eggs.

How does stress affect this system?

1) Stress causes the hypothalamus to release less LHRH (GnRH)

Increased endorphins released into the hypothalamus shuts off LHRH cells.

Sexual side effects of stress

Too much sympathetic action, no erection, no lubrication

Parasympathetic nervous system needed for erection and vaginal

lubrication. Sympathetic nervous system kicks in too early, premature ejaculation

Other effects of stress on the reproductive system?

Reduced sexual libido via reduced testosterone or estrogen

Miscarriage due to reduced blood flow to the uterus

The immune system

Energetically costly

Complex and sophisticated

Essential for survival

Macrophages and Neutrophils:

White blood cells that phagocytose (engulf) dead or foreign material and release alarm signals

Lymphocytes:

White blood cells that recognize, remember and respond to foreign invaders

Innate Immune System

- Inflammation

- vasodilation

- cytokines

- neutrophils and macrophages

Acquired (or adaptive)

-Antibodies and Antigens

-Lymphocytes (white blood cells)

• B and T cells (from bone marrow or Thymus), B secretes antibodies, T cells can remember antigens

B cells

lymphocytes that produce antibodies and release cytokines (chemical alarm signals)

Cytotoxic T cells

are lymphocytes that kill infected or targeted cells

Helper T cells

are lymphocytes which recognize and remember antigens and signal other cells as to their presence

Two ways the immune systems can fail:

1) Not repair the damage, leading to cancer, or not kill the invaders leading to infection. E.g AIDS

2) Autoimmune disease: When the immune system attacks your own tissue. E.g. multiple sclerosis, Type 1 diabetes.

How does stress affect the immune system?

Acute stress enhances immunity while prolonged chronic stress shuts down immune system

Synthetic glucocorticoids are used as pharmacological agents to treat:

- Autoimmune diseases

- To reduce inflammation

- After organ transplant

Epi Pen

Epinephrine (adrenaline) is used in times of emergency for allergies (e.g., food, bee stings, snake bites, etc.)

High Glucocorticoids

Glucocorticoids kill lymphocytes and cause them to be removed from the system, immune suppression

Stress and Cancer

1) Compromised immune system allows cancer to spread

2) Glucocorticoids provide energy for cancer cells

Short term memory

- remembered for seconds, minutes or hours then lost

- not dependent on gene expression

Long term memory

- remembered for days, weeks, years, a lifetime.

- dependent on gene expression

Memory trace

biochemical change in the brain which encodes an experience, which lasts beyond the stimulus

Consolidation

stabilization of the memory trace

Reconsolidation

stabilization of the memory after bringing it back into awareness

Retrieval

bringing the memory into awareness

Extinction

learning that a context is no longer associated with a stimulus

Forgetting

loss of the memory trace

Explicit, declarative memory

eg. remembered that Obama was president, the smell of your grandmothers cupcakes.

Cerebellum and dorsal striatum

- Coordinators of movements

- Critical for habit learning, procedural and skill learning

Hippocampus

• Integrator of sensory information

• Binds information about events, time and space.

• Critical for forming new declarative memories

How does stress affect memory?

The hippocampus is loaded with glucocorticoid receptors

Acute stress enhances memory in what way?

Due to increased glucose in the blood (via glucocorticoids) and increased blood flow to the hippocampus (via sympathetic nervous system)

Chronic stress impairs memory

1) Neuron damage shrinking of neurons, weakening memories

2) Neuron vulnerability

3) Neuron death

4) Reduced hippocampal neurogenesis (reduced growth of new neurons)

Chronically elevated glucocorticoid signaling is associated with:

1. A smaller hippocampus

2. Cushing’s disease

3. PTSD

4. Major depression

5. Normal aging

6. Synthetic glucocorticoids

Cushing’s syndrome

hypertrophy of the adrenal gland is associated with memory impairments

Cushing’s syndrome symptoms

• Obesity

• Moodiness, irritability, or

depression

• Memory impairment

• Type 2 Diabetes

• Hypertension

• Immune suppression

• Menstrual disorders such as

amenorrhea in women

• Infertility in women

• Impotence in men

Chronic exposure to synthetic glucocorticoids is associated with

memory impairments

Why do high levels of glucocorticoids make neurons vulnerable?

Chronically elevated glucocorticoids eventually cause neurons to starve for energy. Reduced storage of energy in astrocytes and neurons.

Engineer neurons to obtain energy more readily (increase number of glucose transporters on their membranes) and they are protected from glucocorticoid toxicity

Chronic stress increases risk for:

• Heart disease

• Diabetes

• Ulcers

• Irritable bowel syndrome

• Immune dysfunction

• Cancer

• Impaired growth

• Reproductive dysfunction

• Memory loss

Stress and Aging

Old people (> 80 years) have higher resting levels of glucocorticoids, and it takes them longer to decrease levels of glucocorticoids after stress

Negative feedback

Glucocorticoids kill hippocampal neurons and reduce adult hippocampal

neurogenesis. This impairs the sensor in the negative feedback loop, resulting in greater accumulation of glucocorticoids, which cause more damage to hippocampus, resulting in negative spiral.

How can exercise help people cope with stress if it is a stressor itself?

1) Exercise is usually an acute stressor not chronic (1 hour a day not 12 hours a day)

2) When you are exercising you are using the stress response adaptively, e.g., you need the energy

3) Exercise trains the body physiologically (e.g., more mitochondria in the muscles, higher aerobic capacity), so physical stressors the rest of the day are less stressful.

4) Exercise affects the brain differently than psychological stress, e.g., increases adult hippocampal neurogenesis, makes psychological stress perceived less stressful.