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4/12/11Chapter 49 Sensory and Motor Organisms

1. Overview: Sensing and Actinga. Date Back to appearance in prokaryotesb. Became diverse mechanisms

c. Provides physiological basis for all behaviord. Sensation the different forms of energy detected by the sensory receptorse. Perception- the interpretation of a sensation

2. Introduction to Sensory Receptiona. Exteroreceptors detect stimuli outside the body such as heat, light, pressure and

chemicalsb. Interoreceptors detect stimuli inside the body including blood pressure.c. Sensory Transduction

i. Conversion of stimulus into membrane potential or receptor potential1. Result from opening or closing of ion channel

ii. Amplification Strengthening of stimulus energy by cells in the pathwaysiii. Transmission conduction of impulses to the CNSiv. Integration the processing of the stimuli by the CNS

1. Sensory Adaptation decrease in responsiveness to continuedstimulation.

d. Types of Sensory Receptorsi. Mechanoreceptors respond to mechanical energy such as pressure, touch and

sound1. Muscle spindles respond to stretching of skeletal muscle

ii. Chemoreceptors respond to chemical stimuli1. Osmoreceptors detect changes in blood solute concentration

iii. Electromagnetic Receptors 1. Photoreceptors take in light, and are often referred to as eyes2. Some fish may use electroreceptors3. Thermoreceptors react to heat or cold, signaling surface and body

core temp.iv. Pain receptors or nociceptors

1. Naked dendrites in the epidermis2. Specialized to detect damage to body

3. Hearing and Equilibriuma. Hearing and balance are related functionsb. Produce potentials by the movement of fluidc. Statocysts function as an invertebrates sense of equilibrium

i. Uses layer of ciliated cells around statolithsd. Sound in insects depends on body hair that can respond to sound waves or a tympanic

membranee. Some moths can hear bat sonar

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4/12/11f. In mammals the ear serves both hearing and balance purposes

i. Outer ear- collects sound waves and channels them to the tympanic membraneii. Middle Ear Contains the malleus, incus, and stapes, and transmit vibrations to

the oval window and inner eariii. The Eustachian tube connects the inneriv. Inner Ear many fluid filled channels

1. Cochlea concerned with hearinga. Filled with liquidb. Organ of Corti contains the ear s mechano receptors, which are

hair cellsc. Sound vibrates the hairs which is then interpreted by the brain

v. As a hearing organ1. Vibrating waves go into the ear, and the bones of the middle ear send

vibrations to the oval window, a membrane on the cochlea2. The round window dissipates vibrations3. Vibrations in the cochlear fluid cause membranes to vibrate.4. Pitch is detected based on the location of the depolarized hair cells5. Volume is determined by level of displacement

vi. As a balance organ1. Two chambers, the utricle, and saccule responds to changes in head

direction2. Hair cells are arranged in a gel that moves with the head.3. These are specialized statocysts

g. In other vertebrates the skeleton functions as an outer ear, funneling sounds to a

primitive version of the inner ear.i. The lateral line system detects low-pressure waves that are generated from

water flowing past pores to determines velocity and positionii. Birds have cochleas

4. Senses of taste and smell are closely relateda. In insects, the taste chemoreceptors are located on the feet and are responsive to

certain classes of stimulib. In humans, the receptors are organized into taste buds which are on the tongue, and

are responsive to a wide array of chemicalsi. Saltiness and Sourness are detected by ion channels

ii. Bitter substances close off channelsiii. Umami binds glutamate to Na+ channels, and sweetness is detected by sugar

receptorsc. Odorant binding to olfactory receptors triggers signal-transduction pathways involving

G-protein and often adenylyl cyclase and cAMP.i. This depolarizes the membrane and generates an action potential, there are

more than 1,000 odorant receptor genes.

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4/12/11ii. Each receptor cell only expresses a few receptor genes