Brain Structures and Functions

Hypothalamus Abnormalities

  • Abnormalities in the hypothalamus can cause:
    • Blood pressure regulation issues.
    • Digestive tract mobility problems.
    • Issues with the perception of pleasure, fear, and rage.
    • Difficulties in maintaining normal body temperature.
    • Hunger, satiety, and thirst regulation problems.
    • Sleep disturbances.
    • Hormonal imbalances: The hypothalamus releases hormones that both stimulate and inhibit hormone release from other glands, depending on the body's needs.

Satiety

  • Satiety: Feeling of fullness.
  • Problems with the satiety center can lead to overeating and obesity.

Sleep

  • Proper sleep patterns require communication between the pineal gland and the hypothalamus.

Pleasure, Fear, and Rage

  • These emotions are on a spectrum; balance is key.
    • Too much anger or too much fun can be detrimental.
  • pH Scale Analogy:
    • Neutral water: pH=7pH = 7.
    • Blood pH: pH=7.4pH = 7.4 (slightly alkaline).
    • Alkalosis: pH > 7.5, unsafe.
    • Acidosis: pH < 7.35, unsafe.
  • Emotional Balance: Similar to the pH scale, emotions need to be within a healthy range.

Epithalamus and Pineal Gland

  • Epithalamus: Located on the backside of the thalamus.
  • Pineal Gland: Resides in the epithalamus and secretes melatonin.
  • Suprachiasmatic Nuclei:
    • Located above the optic chiasm.
    • Influences gape (unclear what this refers to).
  • Optic Chiasm:
    • The hypothalamus is situated between the optic chiasm and the mammillary body.
  • Choroid Plexus:
    • Located within the epithalamus.
    • Creates cerebrospinal fluid in the third ventricle.

Brain Stem

  • Brain Stem: Connects the brain to the spinal cord and links the brain to the cerebellum.
  • Basic Structures:
    • Thalamus, midbrain, pons, medulla oblongata.
  • Primitive Functions: The brain stem controls essential life-sustaining functions, making it a primitive part of the central nervous system.
  • Cranial Nerves: Many cranial nerves originate in the brain stem (III, IV, V, VI, VII, etc.).
  • Location of Structures (from a front view):
    • Thalamus (pinkish structures), midbrain, pons, medulla oblongata, spinal cord.
    • Optic nerves and optic chiasm are visible from the front.
    • Infundibulum and mammillary body are located behind the optic chiasm.
  • Location of Structures (Sideways View):
    • Thalamus, midbrain, pons, medulla oblongata.
  • White Matter:
    • Composed of myelinated axons.
  • Types of White Matter Fibers:
    • Association Fibers: Connect regions within the same hemisphere.
    • Commissural Fibers: Cross over to the opposite hemisphere.
    • Projection Fibers: Ascend and descend, connecting the brain to the spinal cord.
  • Peduncles: Projection fibers that connect to the brain (cerebral peduncles) or cerebellum (cerebellar peduncles).
  • Cerebellar Peduncles: There are three: superior, middle, and inferior.
    • Superior: Connects to the midbrain.
    • Middle: Connects to the pons.
    • Inferior: Connects to the medulla oblongata.

Midbrain (Mesencephalon)

  • Anterior: Cerebral peduncles.
  • Posterior: Superior cerebellar peduncles.
  • Cut Through Midbrain:
    • Cerebral peduncles in the front and superior cerebellar peduncles on the backside.
    • Cerebral aqueduct: A canal connecting the third and fourth ventricles.
  • Substantia Nigra:
    • Nuclei within the midbrain.
    • Communicates with the basal nuclei.
    • Dysfunction leads to Parkinson's disease.
  • Red Nuclei:
    • Important for subconscious control of upper limb muscle tone.
  • Posterior (Backside):
    • Superior and inferior colliculi (corpora quadrigemina).
  • Superior Colliculi:
    • Reflex center for movements of the eyes, head, and neck in response to visual stimuli.
  • Inferior Colliculi:
    • Reflex center for auditory stimuli.
    • Triggers startle reflexes.

Pons

  • Middle Cerebellar Peduncles: Originate from the pons and connect to the cerebellum.
  • Respiratory Centers:
    • Apneustic center.
    • Pneumotaxic center.
  • Apneustic Center:
    • Important for switching between breathing in and breathing out.
  • Ascending and Descending Tracts: Cerebral peduncles with motor (red lines) and sensory (blue lines) functions.
  • Phrenic Nerve:
    • Originates from the cervical plexus (C5).
    • Activates the diaphragm.
  • Chemical Equation and Breathing:
    • \{CO2 + H2O \rightleftharpoons H2CO3 \rightleftharpoons H^+ + HCO_3^-}}
    • Carbonic acid (H<em>2CO</em>3H<em>2CO</em>3) quickly dissociates into a proton (H+H^+) and bicarbonate (HCO3−HCO_3^-).
    • Accumulation of CO2CO_2 forms carbonic acid, which lowers the pH.
    • Acidity in cerebrospinal fluid stimulates the phrenic nerve, promoting breathing.
  • Soda Pop Analogy:
    • Soda pop is carbonated with CO2CO_2, making it acidic.
    • The pH of Coca-Cola is approximately 2.5.
    • The acidity can dissolve materials like meat or rusty nails over time.
  • Respiratory Centers and Cerebrospinal Fluid:
    • Lack of proteins in cerebrospinal fluid means acidity changes occur quickly.
    • Acidity stimulates the phrenic nerve, initiating breathing.

Medulla Oblongata

  • Cerebral Peduncles: Continue as pyramids in the medulla.
  • Decussation of the Pyramids:
    • 80% of ascending and descending information crosses over in the medulla.
    • This crossover explains why touching one side of the body is felt on the opposite side of the brain.
  • Nuclei in the Medulla:
    • Cardiac center: Controlled by the vagus nerve (cranial nerve X).
    • Damage to the medulla can cause breathing and heart function to stop.
    • Breathing center.
  • Swallowing Center:
    • Dysfunction can lead to aspiration (food entering the trachea).
    • Long-term diabetes can damage thiscenter.
  • Other Centers: Hiccup, sneezing, etc.
  • Inferior Cerebellar Peduncles: Connects the medulla to the cerebellum.

Cerebellum

  • Vermis: Terminology to note.
  • Lobes: Two lobes, allowing for localized cerebellar problems.
  • Purpose: Coordinates body movements, compares intended actions with actual body performance, and provides smooth, economic movement.
    • Damage to the cerebellum results in poor balance and difficulty with coordinated movements.
    • Cerebellar issues can resemble drunkenness.
      *Examples: Riding bike, walking]]

Cerebellar Function

  • Walking Instructions:
    • Premotor cortex sends instructions to the precentral gyrus (primary motor cortex).
    • Information travels down the spinal cord to muscles.
    • Middle cerebellar peduncles inform the cerebellum.
  • Muscle Receptors (Feedback):
    • Receptors provide feedback to the cerebellum via the inferior cerebellar peduncles.
  • Cerebellum as a Mini-Computer:
    • Corrects deviations from intended movements.
  • Police Sobriety Tests:
    • Tests like standing on one leg or walking a straight line assess cerebellar function.
  • Alcohol and the Cerebellum:
    • Alcohol impairs cerebellar function.
  • Cerebellar Stroke:
    • Symptoms mimic drunkenness.
  • Motor Tasks:
    • Smooth, economical movements.
    • Cerebellar damage results in tremors and difficulty with coordination.
  • Localized Damage:
    • Issues on one side of the cerebellum affect the same side of the body.
  • Brain Involvement in Movement: Moving muscles involves premotor cortex, precentral gyrus (primary motor area), substantia nigra, red nuclei, basal nuclei, and cerebellum.

Motor Disorders

  • Hyperkinetic: Excessive movement.
    • Ballism: Uncontrollable, violent movements.
    • Chorea: Constant, involuntary dancing movements.
    • Athetosis: Writhing movements of wrists and fingers.
  • Hypokinetic: Reduced movement.
    *Akinesia: Absence of movement (late-stage Parkinson's).
    *Bradykinesia: Slowness of movement. [Example: Stone-cold look in late-stage Parkinson's due to facial muscle stiffness.]

Parkinson's Disease

  • Damage to the substantia nigra.
    *Affects basal nuclei.

Huntington's Disease

  • Genetic problem (mutation on chromosome 4).

  • Autosomal Dominant Disease:
    *Only one damaged gene is needed for the disease to manifest.

    • Symptoms appear around age 45 with a ten-year life expectancy after onset.

  • Cerebellar Disorders:
    *Manifestations: Poor posture, poor equilibrium, ataxia (uncoordinated movement), and drunken-like gait.

Limbic System (Emotional Brain)

  • Evolutionary Perspective:
    *Is the oldest part of our brain.

Emotions

*Requires awareness, feelings, urge to take action, and physical displays.

Limbic System Structures

  • Fornix: Connects to mammillary body; brings smell into limbic system.

  • Amygdala and Hippocampus: Nuclei involved in important functions.

  • Cingulate Gyrus: Pathway above corpus callosum.

    Olfactory

*That smell feeds into the mammillary body via the fornix and connects with the amygdala and hippocampus.

  • Sexuality Resides in the Emotional Brain:
    *Damage to amygdala can cause hypersexuality.
    *Stimulation of hypothalamus can cause erection.

    Fear

    *Part of the amygdala. [Example: Monkeys' fear of snakes.]
    *Destroying amygdala eliminates fear.

    Medical Scans

    *Medical scans of normal people seeing fearful images show blood flow to amygdala.
    *Individuals with psychopathic deficits show no such reaction.

  • Phobias: Unnatural fear of something, often linked to abnormalities in the amygdala.
    *Treatments: Pacemakers to tune the amygdala.

    Hippocampus

    K Good for short-term memory and spatial navigation.
    *Damage linked to Alzheimer's disease.
    *Extreme damage results in anterograde amnesia.
    Fifty-First Dates (Movie): [Example is mentioned.
    Adam Sandler and Drew Barrymore (amnesiac).

    Medical Findings

    *Interviewed a sailor with such condition (17 years old in 1941).
    MRI Scans: Demonstrate less blood flow in those with memory problems.

  • Olfactory System and Memory:
    *Strongest memories sometimes come from smell. [Example: Bad smells.]
    *Limbic System and Illness: Psychosomatic illnesses can originate in the limbic system.

Reticular Activating System (RAS)

  • Diffuse Network: Runs through the brainstem (midbrain, pons, medulla).

  • Arousal and Alertness:Governs brain arousal and keeps cortex alert.

Medical Findings

The RAS is a filtering mechanism.
If every sensation was equally important, you d go crazy.
*Activity is inhibited by sleep centers.
*knocked out by psychedelic drugs.
*Stimuli

Psychedelic Drugs

LSD and magic mushrooms

CIA

Kidnap spies
put them on LSD so they would reveal all the secrets.

Coma

   Damage to RAS. Coma occurs

# Narcolepsy

 If doesn't work. Sleep then wake