Review of Chapter 60 - Guyton & Hall's Medical Physiology

Topic: Sleep and Disorders of Brain Activity

Definition of Sleep

Sleep: Unconsciousness from which a person can be aroused by sensory or other stimuli.
- Different from a coma (no arousal possible).
Types of Sleep: REM (Rapid Eye Movement) and Non-REM (Slow Wave Sleep).

Characteristics:
- Active sleep, not very restful.
- Occurs in cycles (~every 90 minutes).
- Increased dreaming and body movements.
- Difficult to arouse, irregular heart and respiratory rates.
- High brain activity, paradoxical sleep (similar to wakefulness).

Characteristics:
- Very restful, recovery sleep.
- More prominent the longer one has been awake.
- Strong, low-frequency brain waves.

Measurement: Electroencephalogram (EEG).
Types of Brain Waves:
- Alpha Waves: Awake, resting state.
- Beta Waves: Concentration, lower amplitude, irregular.
- Theta Waves: Emotional stress, brain disorders.
- Delta Waves: Deep sleep, low neuronal activity.

Active inhibitory process.
Stimulatory Pathways:
- Raphe Nuclei: Secretes serotonin, inhibits neural activity.
- Nucleus of Tractus Solitarius: Inputs from vagus and glossopharyngeal nerves.
- Diencephalon: Rostral hypothalamus, diffuse thalamic nuclei.
Sleep-Promoting Substances: Muramyl peptide, other cerebrospinal fluid substances.

Reticular Formation: Activates cerebrum upon waking; fatigue leads to inhibition and sleep.
Orexin Neurons: Active during wakefulness, destruction causes narcolepsy.

Effects of Sleep Deprivation:
- Cognitive and physical performance reduction.
- Lower productivity, poorer health.
- Restorative role for central nervous system balance.
Further Reading: Matthew Walker's book on sleep (link in description).

Epileptic Seizures:
- Uncontrolled, excessive neuronal activity.
- Types:
  - Focal Seizures: Localized to one hemisphere, can spread.
  - Generalized Seizures: Involves both hemispheres, e.g., grand mal seizures (tonic-clonic).
- Epilepsy: Multiple recurrent seizures.
- Treatment: Anti-epileptic drugs, surgical fixes for focal seizures.

Parkinson’s Disease: Dopamine deficit in substantia nigra.
Huntington’s Disease: Loss of GABA neurons.
Depressive Psychosis: Diminished norepinephrine or serotonin.
- Treatment: MAO inhibitors, tricyclic antidepressants.
Bipolar Disorder: Excess norepinephrine or serotonin.
- Treatment: Lithium compounds.
Schizophrenia: Possible causes include blocked prefrontal lobes, excess dopamine, abnormal limbic system function.
- Treatment: Decrease dopamine secretion.
Alzheimer’s Disease: Premature brain aging, memory loss, beta-amyloid peptide accumulation.