L25 Sleep, Genes, & Schizophrenia

Question 1

What is Sleep?

Answer 1

Sleep:

• A process when your body rests & restores energy
• It is an active state that affects both your physical & mental well-being

Question 2

What 2 basic states compose sleep?

Answer 2

1. Rapid eye movement (REM) sleep
2. Non-rapid eye movement (non-REM) sleep

Question 3

How many stages make up Non-Rem sleep?

Describe each stage

Answer 3

Stage 1:

• Decrease in activity between wakefulness & stage 1
• Eyes are closed and a person can easily be awakened
• Usually last ~10 min

Stage 2:

• A period of light sleep with spontaneous periods of muscle tone mixed with periods of muscle relaxation
• Decreased HR and body temperatures
• Usually lasts about 20 min

Stage 3:

• Deep sleep stages (AKA slow-wave or delta sleep)
• Repair and regenerates tissues
• Builds bone & muscle
• Appears to strengthen the immune system

Question 4

Explain REM Sleep

Answer 4

REM Sleep:

• Usually occurs 90 minutes after sleep onset
• Several periods occur:
  
  • First period of REM typically lasts 10 minutes
  • Each recurring REM stage lengthens
  • Final one may last up to an hour
• Percentage of REM sleep decreases:
  
  • Infancy: 50% (highest)
  • Adult: 20%
• Characterized by;
  
  • Heart rate & respiration speed up and become erratic; the eyes move rapidly in different directions
  • Intense dreaming occurs as a result of heighten brain activity; however, paralysis occurs simultaneously in the major voluntary muscle groups

Question 5

What does sleep depriviation lead to?

Answer 5

Sleep deprivation:

Causes the brain to become incapable of;

• Putting an emotional event into the proper perspective
• Making a controlled, suitable response to the event

Leads to:

1. Impaired memory and thought processes;
2. Depression
3. Decreased immune response
4. Fatigue
5. Increased pain

May be linked to serious diseases, such as;

• Heart disease
• Type II diabetes
• Mental illness including psychosis & bipolar disorder

Question 6

Define Schizophrenia

Symptoms?

Treatment?

Answer 6

Schizophrenia:

• Mental disorder characterized by a breakdown in thinking & poor emotional responses.

Symptoms:

• Delusions, such as paranoia; Hearing voices or noises that are not there
• Disorganized thinking
• Lack of emotion & motivation
• Symptoms cause significant social and work problems
• Typically begin in young adulthood; ~0.3–0.7% of people are affected during their lifetime

Treatment:

• Mainstay of treatment is antipsychotic medication, which primarily suppresses dopamine receptor activity
• 2nd-Gen medications (i.e. Clozapine) are generally preferred because they pose a lower risk of serious side effects than do first-generation antipsychotics

Question 7

What are the causes of schizophrenia?

Answer 7

Multifactorial disorder:

• Combination of genetic & environmental factors
• Primary genes (2):
  
  • Dysbindin (DTNBP1)
  • Neuregulin (NRG1)

Question 8

How is sleep associated with schizophrenia?

Answer 8

~80% of schizophrenia patients have sleep problems (usually not linked with medication side effect)

The neural and biological system that regulates our sleep-wake cycles to dark and light (collectively known as the clock genes) may play a role in mental disorders

For example, a gene called SNAP25, is important in the circadian system

Mutations in Clock Leads to insomnia, depression and schizophrenia

Question 9

What is the SNAP25 gene?

How is it connected with metal health?

Answer 9

Synaptosomal-associated protein 25 (SNAP-25):

• Component of the trans-SNARE complex, & account for the specificity of membrane fusion & to directly execute fusion by forming a tight complex that brings the synaptic vesicle and plasma membranes together
• Also plays a role in the circadian system and for vesicle cycling in clock cell regulation

Mouse models:

• Heterozygous deletion of the SNAP-25 gene in mice results in a hyperactive phenotype similar to attention deficit hyperactivity disorder (ADHD)
• Missense mutations in SNAP25, resulting in a mouse model of schizophrenia, lead to impaired exocytotic vesicle recycling and exocytosis, along with a reduction in excitatory postsynaptic potentials

Results;

• Suggest that abnormalities in NT signaling predisposing an individual to neuropsychiatric illness can have a direct impact upon sleep/wake timing
• Stabilization of sleep may help reduce symptoms and improve quality of life