Untitled

Chapter 1: Introduction

• Overview of the senses and their modalities.

  • Modality is the type of sensory signal being processed.

  • Mapping is the location of sensory information in the brain.

• Receptor Types:

  • Vision:

  • Type: Electromagnetic energy.

  • Receptors: Rods and cones (G protein receptors).

  • Mapping: Retinotopic mapping, relating to the retina’s structure.

  • Auditory System:

  • Type: Mechanoreceptors (hair cells in the cochlea).

  • Receptors: Hair cells that open ion channels when moved.

  • Mapping: Tonotopic mapping for pitch.

  • Taste:

  • Type: Chemoreceptors.

  • Function: Respond to miscible chemicals (dissolved in water or saliva).

  • Receptors: Different types include metabotropic (G protein coupled) and ion channels.

  • Smell:

  • Type: Chemoreceptors for volatile chemicals in the air.

  • Mapping: Projects to the piriform cortex (direct to amygdala and thalamus).

  • Touch:

  • Type: Mechanoreceptors.

  • Function: Movement opens ion channels, mapped somatotopically.

  • Pain:

  • Includes: Mechanical receptors, free nerve endings, temperature receptors.

  • Mapped: Approximately to body locations.

• Resources on Canvas:

  • Availability of class PowerPoints and review slides for exams.

  • Suggested printing or saving materials for reference.

• Questions about sensory systems or taste discussed.

Chapter 2: A Sweet Taste

• Definition of Taste:

  • Taste is derived from chemicals recognized in the mouth (miscible).

• Structure of Taste Buds:

  • Visible structures known as papillae, but taste receptors are within taste buds.

  • Cross-Section of Tongue:

  • Taste buds lie in grooves on the tongue surface.

  • Contains supporting cells alongside different taste receptors.

• Taste Transduction:

  • Chemicals dissolve in saliva and transmit signals to the brain.

  • Each taste cell transduces specific chemical types into electrical signals.

• Types of Tastes and Receptors:

  • Sweet: receptors for sugars; uses metabotropic receptors (T1R2 and T1R3).

  • Umami: specific to amino acids, activates umami receptors (T1R1, T1R3).

  • Bitter: uses T2R receptors; often relates to toxic plant compounds.

  • Salt: sodium channels, directly activates via ion channels.

  • Sourness: activates proton channels sensing acidity (e.g., citric acid).

• Taste Mapping:

  • Minimal geographic mapping on the tongue; receptors can be found anywhere but concentration varies.

  • Unique areas process different tastes within the gustatory cortex.

Chapter 3: Touch And Pain

• Systems of Sensation:

  • Somatosensory System: Relates to perception of body position and external contact.

  • Types of sensory systems:

  • Exteroceptive: External sensations (touch).

  • Proprioceptive: Body position and balance.

  • Interoceptive: Internal body condition (e.g., temperature).

• Cutaneous Receptors:

  • Mechanoreceptors under the skin; each detects different types of touch.

  • Types of Receptors:

  • Free Nerve Endings: Temperature and pain.

  • Pacinian Corpuscles: Indentation and sudden pressure.

  • Meissner's Corpuscles: Light touch.

  • Merkel's Discs: Deep static touch.

  • Ruffini Endings: Skin stretch.

• Receptive Fields:

  • Area of the body covered by a receptor; affects touch perception.

  • Two-point discrimination is influenced by the size of the receptive fields.

• Adaptation of Sensory Receptors:

  • Rapidly Adapting: Fire in response to changing stimuli.

  • Slowly Adapting: Maintain response to steady stimuli.

• Stereognosis: Ability to identify objects by touch alone.

Chapter 4: Dorsal Columns

• Neural Pathways for Touch and Pain:

  • Sensory information enters the dorsal horn of the spinal cord.

  • Two main pathways in the spinal cord:

  • Dorsal Column Medial Lemniscus System: Touch and proprioceptive sensations.

  • Anterolateral System: Pain and temperature sensations.

• Dorsal Column Pathway:

  • Sensory info enters, ascends, synapses in the medulla, crosses over, and goes to the somatosensory cortex.

• Anterolateral Pathway:

  • Similar entries but crosses immediately upon entering the spinal cord.

  • Includes spinothalamic tract: specifically processes pain and itch signals.

Chapter 5: Pain Perception

• Types of Pain Fibers:

  • A-beta Fibers: Myelinated and fast; for touch sensation.

  • A-delta Fibers: Myelinated; for sharp pain, slower than A-beta.

  • C Fibers: Unmyelinated; responsible for dull, throbbing pain.

• Pain Reflexes:

  • Reflexes allow quick withdrawal from pain before conscious perception.

• Somatosensory Homunculus:

  • Mapped representation of the body in the sensory cortex, distorted by receptor density.

Chapter 6: Descending Pain Modulation

• Pain Modulation:

  • Nociceptors detect pain, responding to various stimuli (touch, temp, injury).

  • Blocked activation of nociceptors reduces pain perception.

• Nerve Pathways:

  • Pain's ascending pathway mainly via A-delta and C fibers.

• Lidocaine Effect:

  • Blocks sodium channels, preventing action potentials, resulting in numbness and reduced pain perception.

• Descending Control:

  • Involves the periaqueductal gray (PAG); mediates signals down the spinal cord to inhibit pain.

  • Opioids work through this system to relieve pain such as morphine.

• Types of Pain:

  • Nociceptive pain (external damage) vs Neuropathic pain (nerve damage).

Chapter 7: Neuropathic Pain

• Types of Neuropathic Pain:

  • Allodynia: Pain from typically harmless stimuli (hypersensitivity).

  • Phantom Limb Pain: Sensation of pain in a limb not present (e.g., after amputation).

• Potential Treatment:

  • Mirror therapy tricks visual perception to alleviate phantom pain.

• Empathic Response to Pain:

  • Shared experience of pain can evoke empathy; has social implications.

Chapter 8: Attention

• Types of Attention:

  • Endogenous Attention: Focused and deliberate.

  • Exogenous Attention: Reactive and stimulus-driven.

  • Selective Attention: Active focus on certain stimuli while ignoring others.

• Cognitive Load and Pain:

  • Higher focus on pain during quiet times can exacerbate the perception of pain.

• Change Blindness:

  • Inability to perceive changes in the visual field when attention is focused elsewhere.

• Conclusion: Discussion of sensory information supporting behavior processes and the transition to motor outputs, to be discussed in future classes.

• Key Concepts to Remember:

  • Attend to the types of receptors and their functions, pathways of sensory signals, and the correlation between sensory systems and their psychological impacts on perception and emotion.