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

cochlea

auditory nerve

eardrumauditory canal

hammer

anvilstirrup

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

choroid

iris

lens

pupil

cornea

aqueoushumor

ciliary muscle

vitreous body

retina

fovea

opticdisk

part ofopticnerve

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 – 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

olfactorybulb

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