The Peripheral Nervous System

The Peripheral Nervous System

  • The Peripheral Nervous System (PNS) involves nerve fibers that facilitate communication between the Central Nervous System (CNS) and the rest of the body.

Group Discussion Activity

  • Flow Chart Task: Create a flow chart detailing the impact of spicy food on:

    • Thermoregulation

    • Heart-rate

    • Awareness

  • Keywords for Post-it Notes: Generate 3-4 keywords relating to:

    • Gustation

    • Thermoregulation

    • Heart-rate

    • Awareness

  • Connect these keywords with lines and brief explanations of their relationships in 10 minutes.

Spicy Food

  • Why does spicy food cause discomfort?

    • Capsaicin: The ingredient that binds to specific receptors in the mouth.

    • Scoville Scale: Measures the heat level of chili peppers and spicy foods.

Example of Scoville Heat Units

  • Pure capsaicin: 16,000,000 units

  • U.S.-grade pepper spray: 2,500,000 - 5,300,000 units

  • Carolina Reaper: 1,000,000 - 2,200,000 units

  • Trinidad Moruga Scorpion: 1,000,000 - 2,000,000 units

  • Bhut Jolokia (Ghost Pepper): 855,000 - 1,041,472 units

  • Other peppers ranked from very hot (Habanero) to mild (Bell pepper).

Effects of Eating Spicy Food

  • General Effects:

    • Spicy foods act as stimulants (due to capsaicin).

    • They increase circulation and body temperature while aiding perspiration that cools the body down.

    • May suppress appetite but evidence is conflicting.

    • Relevant geographic context where spicy foods are consumed benefits fat metabolism and reduces Ghrelin production.

Peripheral Nervous System Details

  • PNS is divided into:

    • Afferent Division: Detects and transmits peripheral signals to the CNS for homeostasis and sensory perception.

      • Visceral Afferent: Gathers information from internal organs.

      • Sensory Afferent: Involves body sensations and special senses (sight, hearing, taste, smell).

Receptors Overview

  • Receptors: Specialized structures at the ends of afferent neurons that detect stimuli and convert them into electrical signals (action potentials).

  • Process: The detection process is referred to as transduction.

Types of Receptors

  • Photoreceptors: Sensitive to light.

  • Mechanoreceptors: Respond to mechanical energy.

  • Thermoreceptors: Sense temperature changes.

  • Osmoreceptors: Detect solute concentrations in fluids.

  • Chemoreceptors: Respond to specific chemicals (smell, taste, O2, CO2 concentrations).

  • Nociceptors: Pain receptors sensitive to tissue damage.

Uses for Sensory Information

  • Afferent input is crucial for controlling efferent output.

  • Sensory information processed by the reticular activating system is essential for consciousness.

  • Perception arises from central sensory processing; sensory stimuli significantly affect emotions.

Receptor Potential Mechanism

  • Receptors may adapt rapidly or slowly.

  • Tonic Receptors: Slow adaptation, relay continuous information (e.g. muscle stretch).

  • Phasic Receptors: Rapidly adapting, signal changes in stimulus intensity.

Somatosensory Pathways

  • Central processing involves neuronal chains for conscious sensations:

    • First-order Neurons: Detect stimuli and synapse with second-order neurons.

    • Second-order Neurons: Located in spinal cord or medulla, synapse with third-order neurons.

    • Third-order Neurons: Located in the thalamus.

Acuity and Perception

  • Acuity: Discriminative ability influenced by receptor field size and lateral inhibition.

    • Smaller receptive fields yield greater acuity.

Visual Perception Insights

  • Conscious Interpretation: Our sensory input generates different perceptions due to brain processing.

    • Visual input illustrates variable interpretations (e.g. duck-rabbit illustration).

  • Children and adults perceive images differently based on learned associations.

Eye Structure and Function

  • Anatomical Layers: Sclera, Cornea, Choroid, Retina.

  • Components:

    • Lens and Cornea: Crucial for refractive ability.

    • Retina: Contains rods and cones that convert light into nerve impulses.

  • Focus on pupils and iris structure for regulating light entry.

Hearing Mechanics

  • Understanding Sound: Sound properties include pitch (frequency), intensity (amplitude), and timbre (quality).

Chemical Senses: Taste and Smell

  • Chemoreceptors: Taste buds detect flavor; olfactory receptors sense smell.

  • Taste involves primary tastes like salty, sour, sweet, bitter, and umami.

Pain Perception and Mechanisms

  • Pain serves as a protective mechanism indicating possible tissue damage, with subjective experiences influenced by memory and past experiences.

Autonomic Nervous System Overview

  • Divisions: Sympathetic (fight-or-flight) and Parasympathetic (rest-and-digest).

  • Illustrate the role of the two systems in organ control and physiological responses.