Anatomy Dissection Planes and Nerves

Dissection Planes

• Coronal plane: A plane that divides the body into front (anterior) and back (posterior) portions.
• Horizontal plane: A plane that divides the body into top (superior) and bottom (inferior) portions.
• Sagittal plane: A plane that divides the body into left and right portions.

Nuclei and Tracts

• Nucleus (gray matter): A cluster of neuron cell bodies (and their dendrites) in the central nervous system (CNS) where synapses occur and information is processed.
• Tract (white matter): Bundles of myelinated axons connecting nuclei, facilitating communication between different brain regions.
• Afferent: Neurons carrying sensory information towards the CNS.
• Efferent: Neurons carrying motor information away from the CNS.
• Somatic: Relating to the body.
• Visceral: Relating to internal organs (viscera).

Functional Components of Nerves

• General Somatic Afferent (GSA): Carry sensory information from muscles and skin to the CNS.
• General Somatic Efferent (GSE): Carry motor information from the CNS to skeletal muscles.
• General Visceral Afferent (GVA): Carry sensory information from organs and blood vessels to the CNS.
• General Visceral Efferent (GVE): Carry motor information from the CNS to smooth muscle and glands (part of the parasympathetic nervous system).
• Cranial nerves: Specific senses.
• Special Somatic Afferent (SSA): Sensory information related to vision, hearing, and balance.
• Special Visceral Afferent (SVA): Sensory information related to smell and taste.
• Special Visceral Efferent (SVE): Motor information to branchial arch striated muscles.

The Nervous System

• Central Nervous System (CNS): Composed of the brain and spinal cord.
  • Brain: Includes the cerebral hemispheres, diencephalon, cerebellum, and brainstem.
  • Spinal cord: Long bundle of nerves conveying signals between the brain and the rest of the body.
• Peripheral Nervous System (PNS): Nerves branching out from the CNS. Includes:
  • Somatic Nervous System: Controls voluntary actions, includes sensory and motor nerves, spinal and cranial nerves.
  • Autonomic Nervous System: Controls involuntary actions, such as smooth muscle contractions and glandular secretions. Includes sympathetic and parasympathetic components.
    • Ganglion: Collection of neuron cell bodies in the PNS. Example: dorsal root ganglion

Early Development of the Brain

• Five secondary brain vesicles: Structures that develop into parts of the mature brain.
  • Telencephalon: Cerebral cortex and basal ganglia.
  • Diencephalon: Thalamus, hypothalamus, pituitary gland, pineal gland (among other structures).
  • Mesencephalon: Midbrain.
  • Metencephalon: Pons and cerebellum.
  • Myelencephalon: Medulla oblongata.
• Brainstem: Consists of the midbrain, pons, and medulla oblongata.

Main Regions of the Brain

• Cerebral Cortex: Six-layered sheet of grey matter. Folded to increase surface area. Divided into two hemispheres.
• Longitudinal fissure: Divides the two cerebral hemispheres.
• Central sulcus: Separates frontal and parietal lobes.
• Lateral sulcus: Separates temporal lobe from parietal and frontal lobes.
• Parieto-occipital sulcus: Separates parietal and occipital lobes.
• Calcarine sulcus: In the occipital lobe, helps locate the primary visual cortex.
• Precentral gyrus: Primary motor area.
• Postcentral gyrus: Primary somatosensory area.
• Primary auditory area: Located below the lateral sulcus.
• Primary visual area: Surrounds the calcarine sulcus.
• Interventricular foramen of Monro: Connects the two lateral ventricles.
• Septum pellucidum: Thin membrane separating the two lateral ventricles.