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Nervous system

Overview of the Nervous System

  • Neurons and Neuroglia

    • Importance of keeping terminology fresh.

    • Neuroglia: includes Schwann cells and myelin.

Anatomy of the Brain

  • Cerebrum:

    • Interprets sensory stimuli and sends motor impulses.

    • Home of creativity.

  • Diencephalon:

    • Contains the Hypothalamus - key for maintaining homeostasis.

  • Brain Stem:

    • Composed of the midbrain, pons, and medulla oblongata.

    • Medulla oblongata regulates essential functions like respiratory and heart rate.

  • Spinal Cord:

    • Discussed spinal cord injuries and their impacts on body functions.

Peripheral Nerves

  • Cranial Nerves:

    • Originate from under the brain; there are 12 cranial nerves.

    • Important cranial nerves:

    • 1 (Olfactory), 2 (Optic), 8 (Vestibulocochlear), 10 (Vagus).

Nervous System Actions

  • Peripheral nerves serve motor functions by activating glands or muscles (via acetylcholine).

  • Autonomic nervous system regulates involuntary actions, split into:

    • Sympathetic: Fight or flight.

    • Parasympathetic: Rest and digest.

Special Senses

  • The five special senses:

    • Vision, hearing, smell, taste, touch.

  • Receptors convert stimuli into electrical signals:

    • Stimulus ➜ Transduction ➜ Action Potential ➜ Sensory Nerve ➜ CNS.

Sensation and Perception

  • Processes:

    1. Sensation: Awareness of a stimulus (e.g., sound).

    2. Perception: Interpretation of the sensation (e.g., identifying sound source).

    3. Adaptation: Brain ignores repetitive stimuli (e.g., background noise).

Pain and Referred Pain

  • Referred Pain: Pain felt in areas other than its source due to shared nerve pathways.

  • Example: Heart pain may manifest as pain in the left arm.

Sensory Receptors

  • Types of receptors:

    • Chemoreceptors: respond to chemical stimuli (smell and taste).

    • Thermal Receptors: respond to temperature changes.

    • Mechanoreceptors: respond to movement (touch, pressure).

    • Photoreceptors: respond to light in the eye.

Pain Management

  • Common methods of pain relief:

    • NSAIDs (Nonsteroidal Anti-Inflammatory Drugs): Aspirin, ibuprofen.

    • Opioids: Prescribed pain relief, high potential for addiction.

    • Non-pharmacological approaches: Physical therapy, psychological approaches (e.g., antidepressants).

  • Importance of addressing the psychological aspect of chronic pain to assist healing.

The Special Senses - Detailed

  • Olfactory (smell):

    • Receptors: Chemoreceptors located in the nasal passage through the cribriform plate, connecting to the olfactory nerve (cranial nerve 1).

    • Strong emotional connections due to its processing through the limbic system.

  • Gustatory (taste):

    • Taste buds primarily located on the tongue with five taste sensations: sweet, sour, salty, bitter, umami.

    • Taste cells send information through sensory nerves for interpretation in the brain.

  • Auditory (hearing):

    • Involves hair cells in the cochlea; sound waves stimulate these cells.

  • Visual (sight):

    • Involves photoreceptors (rods and cones) in the retina, leading to action potentials through the optic nerve (cranial nerve 2).

Sensory Adaptation and Special Cases

  • Adaptation allows ignoring unimportant stimuli (e.g., constant noises).

  • Certain rare conditions like synesthesia result in unusual crossover of sensory perception (e.g., seeing colors with numbers).