biol 3410 11/19 lec

Understanding Reflex Arc

  • Motor Neuron Identification

    • Red neuron represents the motor neuron, which is efferent, exiting the brain and spinal cord.

    • Blue neuron represents the sensory neuron, which is afferent, entering the brain and spinal cord.

    • Familiar from last week's quiz.

  • Describing Reflex Arc

    • Correct answers: polysynaptic and ipsilateral.

      • Polysynaptic: Involves interneurons, indicating multiple synapses.

      • Ipsilateral: Operates on the same side of the body and spinal cord.

Clinical Case Study

  • Sunil's Symptoms: Anterior gray horns of lower cervical regions affected by an infection.

    • Correct symptom: Cannot move his limbs.

      • Analysis: Anterior horns contain motor neurons, which are affected, leading to limb paralysis.

    • Cannot sense touch or pain; these functions are related to sensory neurons and are unaffected.

Switching Focus to the Brain

  • Overview of Nervous System

    • Examining brain structure, cerebrospinal fluid (CSF) circulation, and meninges.

    • Notable imagery and features from National Geographic.

Brain Anatomy

  • Key Structures:

    • Cerebrum, cerebellum, brainstem.

    • Visual distinctions: gyrae (raised areas) and sulci (grooves).

  • Meninges:

    • Brain coverings: Dura Mater (outer), Arachnoid Mater (middle), Pia Mater (inner).

      • Arachnoid Mater: Thin, like shrink wrap around the brain.

      • Pia Mater: Adheres tightly to brain tissue.

Surface Features for Functionality

  • Surface Increase: Rich in gyrae and sulci to maximize surface area, allowing for more neuronal connections.

    • Helps balance size and functionality of the brain within the skull.

Brain Structure Organization

  • Functional Organization:

    • Anterior region processes motor information.

    • Posterior region processes sensory information.

  • Major Brain Regions:

    • Contains various lobes: temporal lobe recognized for associated functions (language, hearing).

    • Specific areas (Wernicke's and Broca's) involved in language processing.

Ventricular System

  • Ventricles Filled with CSF:

    • Two lateral ventricles, third ventricle, fourth ventricle.

    • CSF produced in choroid plexus, circulates through ventricles.

    • Continuous with central canal of spinal cord.

  • CSF Pathways:

    • CSF exits ventricles through median and lateral apertures to surround brain/spinal cord, providing cushioning (akin to an airbag).

    • Protects against physical damage from the skull.

Meninges Comparison: Brain vs. Spinal Cord

  • Similarities and Differences:

    • Both have three layers: dura mater, arachnoid mater, pia mater.

    • In the brain, a sinus (superior sagittal) provides a space for venous blood to collect and exit.

  • Subdural and Subarachnoid Spaces:

    • Not typically seen until trauma or pathology occurs.

CSF Production and Blood-Brain Barrier

  • CSF Generation:

    • Produced by ependymal cells in choroid plexus, circulates to maintain brain homeostasis.

      • Functions to regulate environment and facilitate waste removal.

  • Blood-Brain Barrier:

    • Protects brain from blood substances.

      • Composed of endothelial cells with tight junctions to limit permeability to large molecules.

    • Astrocytes uphold barrier stability and function.

Cranial Nerves Overview

  • Cranial Nerve Classification:

    • Sensory Nerves: Olfactory, optic, vestibulocochlear.

    • Motor Nerves for Eyeball Movement: Oculomotor, trochlear, abducens.

    • Mixed Nerves (motor & sensory): Trigeminal, facial, glossopharyngeal, vagus.

    • Important for functions in head, neck, and body innervation.

  • Mnemonic Devices:

    • Names: "O O To Touch And Feel Very Green Vegetables".

    • Function: "Some Say Marry Money But My Brother Says Big Business Matters More".