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Lecture

ANIMAL SENSORY SYSTEMS AND MOVEMENT-lec 22.docx

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Department
Biology
Course
BIO203H5
Professor
Sanja Hinic- Frlog
Semester
Fall

Description
ANIMAL SENSORY SYSTEMSAND MOVEMENT (lec 22) How do moths and vertebrates hear? • Sensing changes in the environment and moving in response to this information is fundamental to how animals work. • The ability to sense a change in the environment depends on four processes: 1. Transduction, the conversion of an external stimulus to an internal signal in the form of an action potential. 2. Amplification of the signal. 3. Transmission of the signal to the central nervous system (CNS). 4. Integration pr processing with other incoming signals Moths fly through the night sensory neurons will relay info about conditions in/out an animal to the to the CNS. After integrating the info from many sensory neurons the CNS sends signal to the muscle. Integrate sensory input-info from sensory neurons- and respond with motor output via electrical signals, to specific muscle groups (effectors) • Each type of sensory information is detected by a sensory neuron or by a specialized receptor cell that makes a synapse with a sensory neuron. • Transduction requires a sensory receptor cell to convert light, sound, tension, or some other stimulus into an electrical signal. • Sensory receptors are located throughout the body and are categorized by the type of stimulus. Sensory Transduction • Although sensory receptors can detect a remarkable variety of stimuli, they all transduce sensory input—including light, sounds, touch, and odors—to a change in membrane potential. • This change in potential allows different types of stimuli to be transduced to a common type of signal—one that can be interpreted by the brain. • If a sensory stimulus induces a large change in a sensory receptor’s membrane potential, there is a change in the firing rate of action potentials sent to the brain. • The amount of depolarization ( ion flow causes the interior to become more positive) or hyperpolarization ( ion channels cause the cell interior to become more negative than the resting potential ) of the sensory receptor is proportional to the intensity of the stimulus. • Sensory stimulus (large enough)  change in a sensors receptors membrane potential  change in the firing ofAPs sent to the brain • For example, the amount of depolarization that occurs in a sound-receptor cell is proportional to the loudness of the sound. Hearing • Animals have a variety of mechanisms for sensing changes in pressure. • The best-studied type of pressure-sensing is called hearing. • Hearing is the ability to sense sound, which consists of waves of pressure in air or water. • The number of pressure waves that occur in one second is called the frequency of the sound. • We perceive differences in sound frequency as different pitches. • Virtually all animal pressure-sensing systems are based on the same mechanism, a mechanoreceptor cell that responds to pressure. In verterbrates ion channels which respond to pressure are found in hair cells. Hair cells Pressure receptor cells Have many sterocilia( microvilli reinforced by actin filaments) and one kinocilium (true cilium with 9+2 arrangement of microtubules) Sterocilia found in increasing height. If Sterocilia bent in direction of Kinocilium (above right figure), bending opens ion channels If sterocilia other way then K+ channel will close, cell hyperpolarize, results in decrease in neurotransmitter released neuron less likely to trigger action potential The Mammalian Ear The human ear is made up of the outer ear, middle ear, and inner ear, each separated from the others by a membrane. The Outer Ear Reception of sound Outer ear collects pressure waves, propels from head and funneled in tube known as ear canal, end of ear canal wave strikes Tympanic membrane (ear drum) seperates outer and innear ear. The membrane will vibrate bc o air compression. Vibration passed onto ossicles. The Middle Ear Transfers sound wave The vibrations from the eardrum set the ossicles into motion. The ossicles are three tiny bones vibrate against each other one of the bones stapes (stirrup) in the last ossicles which further amplify the sound. The stapes vibrates against membrane known as oval window , the oval window that seperates the middle ear from the inner ear. The Inner Ear The sound waves enter the inner ear and then into the cochlea, a snail shaped organ. The cochlea is filled with a fluid that moves in response to the vibrations from the oval window.As the fluid moves, nerve endings are set into motion. These nerve endings transform the vibrations into electrical impulses that t
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