Fetal Brain Development Stages

Fetal Brain Development

• Neural tube develops by week 4 of gestation; defects lead to spina bifida or anencephaly.
• Neural tube closure is aided by folic acid.

Stages of Fetal Brain Development

• Rapid cell division occurs during neurogenesis (neural proliferation).
• Radial glial cells guide neurons during migration to final locations.
• Neurons take on specific functions during differentiation.
• Synapses are formed between neurons during Synaptogenesis.
• Unused connections are eliminated through pruning.

Critical Periods

• Brain development is shaped by experience during limited time windows.
• Language acquisition, vision, and emotional bonding are examples of critical periods.

Effects of Experience

• Enriched environments lead to more synapses and a larger cortex.
• Deprivation results in fewer synapses and potential long-term cognitive and emotional issues.

Adolescence and Frontal Lobes

• Frontal lobe (prefrontal cortex) matures last at mid-20s.
• Impulsivity and risk-taking occur because of the incomplete development of the frontal lobe.
• Stronger connections between the frontal lobe and the limbic system develop over time.

Plasticity and Phantom Limb Sensations

• Plasticity describes the brain's ability to change.
• After limb loss, the sensory cortex reorganizes, causing a phantom limb sensation.

Nun Study (Snowdon)

• Staying intellectually active reduces the risk of Alzheimer’s disease.
• Education, social support, physical activity, and faith may have an impact.

Chronic Traumatic Encephalopathy (CTE)

• Repeated head trauma causes CTE.
• Memory loss, aggression, depression, and motor issues are symptoms of CTE.

Sensory Processing

• Dermatomes are skin areas that map to specific spinal nerves.
• C fibers transmit slow throbbing pain.
• A-delta fibers transmit fast, sharp pain.
• A homunculus maps the cortical representation of body parts in the sensory/motor cortex.
• Cortical reorganization causes phantom limb sensations in the somatosensory cortex.

Muscle Function

• Type I muscles are slow-twitch muscles with high mitochondria; they support endurance and are red.
• Type II muscles are fast-twitch muscles with low mitochondria; they support explosive power and are white.

Muscle Composition

• Dark chicken meat (legs) uses slower Type I muscles.
• White chicken meat (breast) uses faster Type II muscles.

Proprioception

• Muscle spindles detect muscle stretch.
• Golgi tendon organs prevent excessive force.
• Renshaw cells regulate motor neurons and prevent over-excitation.
• Energy drinks can cause overstimulation which can affect proprioception.

Procedural Memory

• Implicit (procedural) memory allows learning skills.
• The basal ganglia and cerebellum store implicit memories.

Motor Control

• The basal ganglia and substantia nigra are responsible for stopping and initiating movement.
• The cerebellum is responsible for balance and fine-tuning movement.

Motor Pathways

• The dorsolateral corticospinal tract controls limb movement.
• The ventromedial corticospinal tract controls trunk and postural movement.

Basal Ganglia Disorders

• Parkinson’s disease is characterized by a loss of dopamine in the substantia nigra.
• Tremors, rigidity, and slow movement are symptoms of Parkinson's.
• Huntington’s disease is a genetic disorder characterized by excessive movement.

Music and the Brain

• Music therapy can improve movement for Parkinson's patients.

Circadian Rhythms & Sleep Regulation

• Light is the primary zeitgeber that resets the circadian clock.
• The Suprachiasmatic Nucleus (SCN) controls the sleep-wake cycle.
• The pineal gland releases melatonin.

EEG & Sleep Stages

• Stage 1 sleep is characterized by theta waves as an example of light sleep.
• Stage 2 sleep is characterized by sleep spindles and K-complexes.
• Slow-wave sleep (SWS) is characterized by delta waves as an example of deep sleep and body repair.
• REM sleep is characterized by dreaming, high brain activity, and muscle paralysis.

Staying Awake

• The Reticular Activating System (RAS) keeps someone awake and alert.
• Acetylcholine, norepinephrine, serotonin, histamine, and hypocretin promote wakefulness.
• GABA, adenosine, melatonin, and prostaglandins promote sleep.

Effects of Sleep Deprivation

• Sleep deprivation results in memory impairment, emotional instability, and lower immunity.

Narcolepsy

• Sudden sleep attacks are caused by low hypocretin (orexin) from the lateral hypothalamus.

Thalamus & Sleep

• The thalamus inhibits sensory input during sleep

Fatal Familial Insomnia

• Fatal Familial Insomnia is a sleep disorder in which a genetic prion disease causes progressive sleep loss, eventually leading to death.