Sensory Reception Chapter 31

Sensation and Perception Sensation is conscious awareness of a stimulus Perception is understanding what a sensation means

Types of Receptors Mechanoreceptors Thermoreceptors Pain receptors Chemoreceptors Osmoreceptors Photoreceptors

Assessing a Stimulus Action potentials don’t vary in amplitude Brain tells nature of stimulus by: Particular pathway that carries the signal Frequency of action potentials along an axon Number of axons recruited

Recordings of Action Potentials

Sensory Adaptation A decrease in response to a stimulus that is being maintained at constant strength

Somatic Sensations Touch Pressure Temperature Pain Motion Position

Somatosensory Cortex

Hearing Ear detects pressure waves Amplitude of waves corresponds to perceived loudness Frequency of waves (number per second) corresponds to perceived pitch

Anatomy of Human Ear stirrup anvil auditory nerve hammer auditory canal eardrum cochlea

Sound Reception Sound waves make the eardrum vibrate Vibrations are transmitted to the bones of the middle ear The stirrup transmits force to the oval window of the fluid-filled cochlea

Sound Reception Movement of oval window causes waves in the fluid inside cochlea ducts

Sound Reception Fluid movement is sensed by the organ of Corti Hair cells are bent against overlying tectorial membrane and fire

Balance and Equilibrium In humans, organs of equilibrium are located in the inner ear Vestibular apparatus

Vision Sensitivity to light does not equal vision Vision requires two components Eyes Capacity for image formation in the brain

Camera Eyes Characteristic of octopuses, squids, and all vertebrates Eye is structured like a camera Interior is dark chamber Light enters through pupil Lens focuses light on photoreceptors

Human Eye sclera retina choroid iris fovea optic lens disk pupil cornea part of optic nerve aqueous humor ciliary muscle vitreous body

Pattern of Stimulation

Visual Accommodation Adjustments of the lens Ciliary muscle encircles lens, attaches to it When this muscle relaxes, lens flattens, moves focal point farther back When it contracts, lens bulges, moves focal point toward front of eye

The Photoreceptors Rods Cones Contain the pigment rhodopsin Detect very dim light, changes in light intensity Cones Three kinds; detect red, blue, or green Provide color sense and daytime vision

To the Visual Cortex (2) Visual cortex

Taste A special sense Chemoreceptors Five primary sensations Sweet, sour, salty, bitter, and umami

Smell A special sense Olfactory receptors Receptor axons lead to olfactory lobe olfactory bulb receptor cell

Sensory Perception Sensory Cortexes; visual, auditory, smell, taste, somatosensory. Register current incoming sensory signals. Sensory Association Areas for each sense store sensory memory and automatically compare current with past to provide meaning.

Common Integrating Area (CIA) Integrates messages from sensory cortexes and association areas to understand. Also known as the gnostic area = knowing CIA capacity is limited = what your looking at and/or listening to.

Memory CIA must Recall memory from the sensory association areas. Facilitated pathways help. The the CIA Remembers (puts the separate sensory messages back together)

Thought Process CIA is in command Sensory Association Areas provide memory Frontal Lobes provide temporary storage, i.e., train of thought Limbic System provides emotional imput