Perception & Chemical Senses Lecture Notes PDF

# 21/10 W12 Lecture 1 ## Perception - **Sensation:** How your senses transform physical properties of the environment and body into electrical signals relayed to the brain - **Perception:** The process of organizing, selecting, and interpreting these signals ## Six Senses for Humans: 1. Vision 2. H...

# 21/10 W12 Lecture 1 ## Perception - **Sensation:** How your senses transform physical properties of the environment and body into electrical signals relayed to the brain - **Perception:** The process of organizing, selecting, and interpreting these signals ## Six Senses for Humans: 1. Vision 2. Hearing 3. Somatosensation (touch) 4. Taste 5. Smell (Olfaction) 6. Vestibular - Inner ear senses gravity and movement ## Perception is the apprehension of the world by means of our senses - Illusions show how active your brain's constantly information - They provide insight into contexts where the visual system goes beyond the information received. # 22/10 W12 Lecture 2 ## The Chemical Senses ### Dimensionality Problem: - We don't have an infinite amount of receptors to pick up the millions of chemicals that exist, we can only fit things into 5 taste dimensions. ### Taste & Smell are the most individual of our senses ### Taste: Anatomy and Physiology - Papillae, gives tongue bumpy appearance - 4 types of receptors: - Filiform: No taste function, at the tip of tongue. Most numerous bud, acts as an abrasive - Fungiform - Foliate - Circumvallate #### Taste - Sweet - Salt - Bitter - Sour - Umami #### Detection Thresholds - Sweetness: 1 part glucose in 200 - Saltiness: 1 part NaCl in 400 - Sourness: 1 part HCl in 130,000 - Bitterness: 1 part quinine in 2,000,000 ### Super-Tasters - Humans genetically evolve to have more fungiform receptors around the tip and sides of their tongue. - 73% of French are non-tasters - 1.2% of Thaisdians are non-tasters - Differences seen in cultures, genetics, sex, etc. - Taste doesn't always require the presence of the taste. - Experiences: - Miracle fruit: Eilly. - Spice stimulates other parts of face (not flavor pathway). ### Smell (Olfaction) - Distance sense: Olfaction provides information about chemicals suspended in air around us. - Dogs smell 1 part per trillion. 2300 million nerve cells to detect odors - Humans only have 400 channels for smell. - Humans have 5 million. ### Adaptation - We can't escape the smell of ourselves so we are always in a state of olfactory adaptation. ### Sense of smell increases in childhood & early adulthood. But decreases starting in middle age # 24/10 W12 Lecture 3 ## The Somatosensory System - Two major subsystems: - Detection of mechanical stimuli - Detection of pain and temperature ## Mechanosensory Processing: - Detection of external stimuli - Proprioceptors (in muscles, joints, & other deep structures) - All receptors work in the same way: stimuli applied causes the skin to deform or otherwise change nerve endings, action potentials triggered (sensory transduction) - There are lots of variety of receptors, but they can be based into 3 groups - Mechanoreceptors - Nociceptors - Thermoreceptors (temperature) - Quality of a stimulus depends on what receptors respond. Quantity of a stimulus depends on the number of action potentials. ## Mechanoreceptors: - 2 types of foch fibers: - Rapidly adapting (info about change or dynamical ability) - Meissner corpuscles (30-50hz) - Pacinian corpuscles (250-350hz) - Slowly adapting (texture, shape, etc.) - Merkel discs (pressure) - Ruffini organ (unknown) ## Dynamic Sensitivity in Skin Senses: - Tactile afferences (opponent-like after effects) - Tactile adaptation (perceiving spatial patterns on skin) - Active vs passive touch - Consequences of not having either class, not working locally causes local anesthesia, where the absence of sensation is attributed to the world, not the body. ## Nociceptors: - 2 types: - Aδ: myelinated axons (conduct at 20m/s) - C fibers: unmyelinated axons (conduct at 2m/s) - 3 classes: - Aδ mechanosensitive receptors - Aδ mechanothermal nociceptors - Polymodal nociceptors ## Hyperalgesia - Pain is the only sense that exhibits an enhanced sensitivity to stimuli over time. ## Thermoreceptors: - Not well understood. - Physiological zero: internal level of temperature - Below: Cold - Above: Hot ## Proprioceptors - Receptors for "self": - Muscle spindles: Provide info about muscle length - Golgi tendon organ: Provides info about tension - Joint receptors: Provide info on tension in joints.