Brain II Notes

Review of the Brain I

• Major Regions of the Adult Brain: Distinct areas such as the cerebrum, cerebellum, brainstem, and diencephalon.

• Commissures, Association Fibres, and Projection Fibres:

  • Commissures: Connect corresponding areas of the two hemispheres (e.g., corpus callosum).

  • Association Fibres: Connect different parts within the same hemisphere.

  • Projection Fibres: Connect the cerebrum with lower brain and spinal cord, transmitting signals between higher and lower centres.

• Major Lobes of the Cerebral Cortex: Frontal, parietal, temporal, occipital.

• Major Fissures: Central sulcus, lateral sulcus, longitudinal fissure.

• Functional Areas of the Cerebral Cortex: Primary motor area, primary sensory area, language, auditory, visual areas.

• Lateralization of Cortical Function: Different functions tend to be predominantly processed in one hemisphere (e.g., language in the left hemisphere).

• Function of the Basal Nuclei: Involved in regulating voluntary motor activity and controlling muscle tone.

Diencephalon

• Components: Includes the thalamus, hypothalamus, and pineal gland.

• Thalamus Functions:

  • Relay station for sensory and motor signals.

  • Involved in consciousness, learning, and memory.

• Hypothalamus Functions:

  • Integrates autonomic nervous system functions.

  • Regulates temperature, thirst, sleep cycles, and endocrine functions.

  • Controls the pituitary gland and produces hormones like oxytocin.

• Pineal Gland Function: Produces melatonin to regulate sleep patterns.

Brain Stem

• Structure: Comprised of the midbrain, pons, and medulla oblongata.

• Midbrain Structures:

  • Cerebral Peduncles: Contain corticospinal motor tracts.

  • Corpora Quadrigemina: Control reflex activities linked to vision (superior colliculi) and hearing (inferior colliculi).

• Medulla Oblongata:

  • Houses vital control centers for autonomic functions (cardiac and respiratory).

  • Medullary pyramids = crossover of motor pathways (contralateral control).

Cerebellum

• Structure and Function:

  • Second largest brain area, coordinating muscle movements for balance.

  • Involved in cognitive functions like thinking and emotion.

• Components:

  • Two hemispheres with three lobes each: anterior, posterior, and flocculonodular.

  • Cerebellar Peduncles: Connect cerebellum to the brain stem.

• Gray and White Matter: Gray matter (cerebellar cortex - folia) and white matter (arbor vitae).

Functional Brain Systems

• Limbic System: Involved in emotional responses and connections throughout the brain.

• Reticular Activating System: Extends through the brain stem to keep the cortex alert and suppresses repetitive stimuli.

Memory

• Types of Memory: Declarative (facts), procedural (skills), motor, emotional.

• Declarative Memory: Short-term vs. long-term; the hippocampus is critical for memory processes.

Consciousness

• Defined on a Continuum: Ranges from alertness to coma based on responsiveness to stimuli.

• Syncope: Temporary medical condition where an individual briefly loses consciousness.

• Coma: Extended loss of consciousness.

Sleep

• Types: Non-rapid eye movement (NREM) and rapid eye movement (REM).

• NREM: Restorative properties.

• REM: Associated with dreaming and cognitive functions.

Protecting the CNS

• Meninges: Three protective membranes covering the CNS: dura mater (outer), arachnoid mater (middle), pia mater (innermost).

• Blood-Brain Barrier: Protects the brain from potentially harmful substances while allowing nutrients to pass.

• Cerebrospinal Fluid (CSF): Provides cushioning and chemical stability; produced by choroid plexus in the brain ventricles.

Diencephalon

• Location: Situated between the cerebrum and the brain stem.

• Subdivisions and Functions:

  • Thalamus: Acts as a relay station for sensory and motor signals; involved in consciousness, learning, and memory.

  • Hypothalamus: Integrates autonomic nervous system functions, regulates temperature, thirst, sleep cycles, endocrine functions, controls the pituitary gland, and produces hormones like oxytocin.

  • Pineal Gland: Produces melatonin to regulate sleep patterns.

Brain Stem

• Regions and Functions:

  • Midbrain: Contains cerebral peduncles (corticospinal motor tracts) and corpora quadrigemina (controls reflex activities linked to vision and hearing).

  • Pons: Connects different parts of the brain and assists in regulating breathing and communication between brain areas.

  • Medulla Oblongata: Houses vital control centers for autonomic functions such as cardiac and respiratory systems; contains medullary pyramids that cross motor pathways for contralateral control.

Cerebellum

• Structure and Function: The second largest brain area, composed of two hemispheres with three lobes (anterior, posterior, and flocculonodular). It coordinates muscle movements for balance and is involved in cognitive functions like thinking and emotion. Contains gray matter (cerebellar cortex - folia) and white matter (arbor vitae).

Functional Brain Systems

• Limbic System: Involved in emotional responses and connections throughout the brain, playing a key role in motivation, learning, and memory.

• Reticular Activating System: Extends through the brain stem to keep the cortex alert, suppressing repetitive stimuli and regulating wakefulness.

Consciousness

• Defined on a continuum, ranging from alertness to coma based on responsiveness to stimuli. Clinically, conditions like syncope indicate temporary loss of consciousness, while a coma reflects an extended loss.

Sleep

• Slow-Wave Sleep (NREM): Considered restorative and crucial for physical recovery, featuring deep relaxation and reduced brain activity.

• REM Sleep: Associated with vivid dreaming, increased brain activity, and is essential for cognitive functions like memory consolidation.