Ap2 Sensation

Neural Excitation and Inhibition

  • Excitatory Postsynaptic Potential (EPSP): When a green neuron excites another neuron causing a positive change in the membrane potential.

  • Inhibitory Postsynaptic Potential (IPSP): When a red neuron releases inhibitory neurotransmitters on a neuron leading to a decrease in membrane potential.

  • Postsynaptic Potentials: Changes in membrane potential caused by neurotransmitters released in response to stimuli.

Sensory Receptor Function

  • Transduction: The process where stimuli (like sugar, light, vibrations) interact with sensory receptors to cause a change in membrane potential.

  • Receptor Potential: The resultant graded potential in response to stimuli within sensory neurons, which can result in either depolarization or hyperpolarization.

The Role of Ions in Sensory Neurons

  • Multiple ions (calcium, chlorine, potassium, sodium) play a role in changing membrane potentials, regardless of direction (influx or efflux).

  • Variability Across Senses: Different senses may respond differently; the type of sensory receptor affects the nature of the response.

Key Definitions

  • Transduction: The interaction of stimuli with sensory receptors to cause a receptor potential, leading to neurotransmitter release.

  • Receptor Potential: Considered a graded potential occurring within a receptor which can lead to a change in neurotransmitter release.

Sensory Receptors Overview

  • All sensory neurons transduce stimuli by generating receptor potentials that alter neurotransmitter release rates.

  • Not all sensory neurons generate action potentials; some may only influence neurotransmitter release without firing.

  • Action potentials are more likely in longer sensory neurons vs. shorter ones where receptor potentials can still affect neurotransmitter release.

Specific Sensory Receptors

  • Mechanoreceptors: Detect mechanical changes like pressure, vibrations, and movement (e.g., hair cells for balance).

  • Thermoreceptors: Respond to temperature changes, detecting warm and cold stimuli.

  • Photoreceptors: Specialized for detecting light, mainly related to vision.

  • Chemoreceptors: Detect chemicals, involved in taste and smell.

  • Nociceptors: Specialized for detecting harmful stimuli, associated with pain perception.

Adaptation and Sensitivity

  • Adaptation: The decrease in receptor sensitivity over time to a constant stimulus.

  • Sensitivity: Each receptor is specific to a type of stimulus; separate receptors detect different sensations (like taste and sound).

Proprioceptors and Body Awareness

  • Proprioceptors: Specialized stretch receptors found in muscles, tendons, and joints; they provide the brain with information about body position and movement.

  • Important for coordinating movement and maintaining balance.

Olfactory System (Smell)

  • Known scientifically as olfaction; the organ of smell is the olfactory epithelium.

  • Must dissolve in mucus to be detected; moisture helps carry scents effectively to the olfactory receptors.

  • Olfactory signals bypass the thalamus and go directly to the olfactory cortex, linking smell closely with emotion and memory.

Gustatory System (Taste)

  • Known as gustation; the primary organ for taste is the papillae on the tongue.

  • Taste buds, the actual sensory structures, consist of gustatory cells that respond to various taste molecules.

  • Key basic tastes include:

    • Sweet: sugars and carbohydrates.

    • Sour: hydrogen ions (citrus fruits).

    • Salty: sodium ions.

    • Bitter: diverse plant compounds.

    • Umami: primarily glutamate and aspartate (savory flavor from proteins).

Integration of Sensory Information

  • Sensory input leads to changes in neurotransmitter release, enhancing communication between sensory receptors and the brain.

  • Different types of receptor cells work together to provide a comprehensive sensory experience, adapting the body's response to varying stimuli.