week 1b

Anatomy of neurons and synapse

Overview

  • Focus on terminology for major subdivisions of the nervous system.

  • Importance of understanding neuroanatomy for future discussions.

Neuron Structure

  • Neurons: Basic units of the nervous system.

    • Cell Body: Contains the nucleus.

    • Dendrites: Receive inputs from other neurons.

    • Axon: Conducts electrical impulses (action potentials).

Glial Cells

  1. Oligodendrocytes: Myelinate axons in the CNS.

  2. Schwann Cells: Myelinate axons in the PNS.

  3. Microglia: Clean up debris and respond to injury.

  4. Astrocytes: Support neurons and regulate blood-brain barrier.

Neuron Zones

  • Input Zone: Dendrites receive signals.

  • Integration Zone: Cell body processes inputs.

  • Conduction Zone: Axon transmits action potentials.

  • Output Zone: Axon terminals release neurotransmitters.

Synapse Structure

  • Synaptic Cleft: Gap between pre- and post-synaptic neurons.

  • Neurotransmitter Release: Action potentials trigger release into the cleft.

Dendritic Spines

  • Dynamic structures for synaptic connections.

  • Involved in learning and memory through structural changes.

Action Potential

  • Initiated at the axon hillock after sufficient excitation.

  • Conducted along the axon, leading to neurotransmitter release.

Summary

Understanding these components is crucial for grasping how the nervous system functions and communicates

Anatomy of the peripheral nervous system

Peripheral Nervous System (PNS)

  • Definition: All nerves outside the brain and spinal cord.

  • Components:

    • Cranial Nerves

    • Spinal Nerves

  • Subdivisions:

    • Somatic Nervous System: Controls muscle movements and sensory information.

    • Autonomic Nervous System: Regulates involuntary functions.

Autonomic Nervous System (ANS)

  • Divisions:

    • Sympathetic Nervous System:

      • Function: Prepares body for "fight or flight."

      • Effects: Inhibits digestion, accelerates heartbeat, dilates pupils.

      • Neurotransmitter: Norepinephrine.

    • Parasympathetic Nervous System:

      • Function: Promotes "rest and digest."

      • Effects: Stimulates digestion, slows heart rate, constricts pupils.

      • Neurotransmitter: Acetylcholine.

    • Enteric Nervous System:

      • Function: Governs gut function and digestion.

      • Neurotransmitters: Acetylcholine, serotonin.

Key Points

  • Sympathetic and parasympathetic systems often oppose but can work together.

  • Enteric nervous system influences mental processes and gut health.

Central Nervous system major divisions

  • Anatomy Focus: Primarily on the brain, with the spinal cord included.

  • Sectioning Methods:

    • Horizontal: Cuts the brain horizontally.

    • Sagittal: Cuts vertically, dividing left and right.

    • Coronal: Cuts vertically from front to back.

  • Directional Terms:

    • Dorsal/Ventral: Up/Down.

    • Anterior/Posterior: Front/Back.

    • Medial/Lateral: Midline/Away from midline.

  • CNS Hierarchy:

    • Spinal cord → Hindbrain → Midbrain → Forebrain (increasing complexity).

  • Brain Structure:

    • Cerebral Hemispheres: Two halves connected by the corpus callosum.

    • Cortex: Wrinkled surface with gyri (peaks) and sulci (valleys).

    • Lobes: Frontal, Parietal, Occipital, Temporal, each with distinct functions.

  • Functional Specialization:

    • Right brain controls left body; left brain controls right body.

    • Motor/Sensory Cortex: Non-proportional allocation of cortical space based on complexity of movements and sensory input.

  • Evolutionary Adaptation: Brain structures reflect species-specific needs (e.g., rats have specialized areas for whisker sensory input).

Regions of the central nervous system

Major Divisions

  1. Forebrain

    • Prefrontal Cortex

      • Largest in humans; involved in impulse control, decision-making, and memory.

      • Inhibits impulsive actions (e.g., aggression, stealing).

      • Supports delayed gratification and abstract thinking (e.g., complex tasks).

      • Historical context: frontal lobotomy reduced agitation but caused emotional blunting.

    • Subcortical Regions

      • Thalamus: Relay station for sensory information to the cortex.

      • Hypothalamus: Controls vital drives (feeding, fighting, mating) and regulates hormones.

      • Basal Ganglia: Important for voluntary movement and habit learning.

    • Limbic System: Involved in memory, emotion, and motivation (e.g., hippocampus, amygdala).

  2. Midbrain

    • Involved in eye gaze and dopamine production.

  3. Hindbrain

    • Cerebellum: Regulates movement, balance, and coordination.

    • Brainstem: Controls vital functions (heart rate, respiration).

Fun Facts

  • Cerebellum: Name means "little brain."

  • Characters inspired by brain regions: Princess Amygdala (Star Wars) and Miss Cerebellum (Power Puff Girls).

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