Chapter 50 Concept 50 1 Sensory receptors transduce stimulus energy and trsmit signals to the CNS All stimuli represent forms of energy Sensation involves converting energy into a change in the membrane Sensory pathways have four basic functions in common potential of sensory receptors Sensory pathways 1 Sensory Reception 2 Transduction 3 Transmission 4 Integration Sensory reception and transduction Sensations and perceptions begin with sensory reception detection of stimuli by sensory receptor outside the body Sensory Receptors Interact directly with stimuli both inside and Sensory transduction is the conversion of stimulus energy into a change in the membrane potential of a sensory receptor This change in membrane potential is called receptor potential graded potentials their magnitude carries with the strength of the stimulus Transmission After energy has been transduced into a receptor potential some sensory cells generate the transmission of action potentials to the CNS Some sensory receptors are specialized cells that regulate neurons Specialized sensory cells include those used for vision taste and Sensory neurons produce action potentials and their axons extend into the hearing CNS The response of a sensory receptor varies with intensity of stimuli If the receptor is a neuron a large receptor potential results in more frequent action potentials Used in smell pain touch pressure and body position receptors if the receptor is not a neuron but a specialized sensory receptor cell a larger receptor potential causes more neurotransmitters to be released May alter action potential frequency of the sensory neuron that is communicating with the sensory cell Perception Perceptions Are the brains construction of stimuli Stimuli travel as action potentials along dedicated neural pathways Brain distinguishes stimuli from different receptors Types of Sensory receptors as pressure stretch motion and sound 1 Mechanoreceptors Sense physical deformation caused by stimuli such Touch relies on mechanoreceptors Knee jerk response is triggered by the vertebrate stretch receptor detects muscle movement solution 2 Chemoreceptors transmit info about the total solute concentration of a Smell and Taste Specific chemoreceptors respond to individual kinds of molecules When a stimulus molecule binds to a chemoreceptor it becomes more or less permeable to ions changing membrane potential 3 Electromagnetic Receptors detect light electricity and magnetism Photoreceptors detect light 4 Thermoreceptors respond to heat or cold help regulate body temp by signaling surface and core body temp 5 Pain receptors or Nociceptors is a class of naked dendrites in the epidermis damaged or inflamed tissue Respond to excessive hear pressure or chemicals released form Concept 50 2 Mechanoreceptors responsible for hearing and equilibrium detect moving fluid or settling particles Hair Cells detect setting particles or moving fluid Hearing Vibrating objects create percussion waves in the air that cause the tympanic membrane Ear Drum to vibrate 3 bones of the middle ear transmit the vibrations of moving air to the oval window on the cochlea movement of hair cells in the ear Vibrations create pressure waves in the fluid in the cochlea stimulate the Equilibrium balance Several organs of the inner ear detect body movement position and Utricle and saccule contain granules called otoliths that allow us to perceive position relative to gravity or linear movement 3 semicircular canals contain fluid and can detect angular movement in any direction Movement of body causes the otoliths or fluid to lag behind causing movement of hair cells which can then send a signal to the brain in animals tastants Taste in Mammals Smell in Humans cavity Concept 50 3 Visual receptors in diverse animals depend on light absorbing pigment Processing of visual info beings in the retina 2 photoreceptors 1 Rods Lowlight perceive shades of gray 2 Cones Bright light perceive color Red Blue Yellow Concept 50 4 Sense of taste and smell rely on similar sets of sensory receptors Gustation Taste Dependent on detection of chemicals called Olfaction Smell Dependent on detection of odorant molecules Taste buds receptor cells for taste are modified epithelial cells 5 Tastes Sour Salty Bitter Sweet and Umami Olfactory receptor cells are neurons that line the inner portion of the nasal Concept 50 5 They physical interaction of protein filaments is reguired for muscle function Muscle activity is a response to input from the nervous system motor output occurs efferent neurons that are connected to 1 Skeletal muscles 2 Smooth muscles found in internal organs blood vessels 3 Cardiac muscle 4 Glands Action of muscle is always to contract Concept 50 6 Skeletal system transforms muscle contraction into locomotion Skeletal muscles are attached in antagonistic pairs actions are coordinated by nervous system Vertebrate Skeletal Muscle Vertebrate skeletal muscle moves bones and the body and is characterized by a hierarchy of smaller and smaller units A skeletal muscle consists of a bundle of long fibers each a single cell running parallel to the length of the muscle Each muscle fiber is itself a bundle of smaller myofibrils arranged longitudinally Myofibrils are composed of 2 types of myofilaments 1 Thin Filaments consist of 2 strands of actin and 2 strands of a regulatory protein 2 Thick filaments staggered arrays of myosin molecules Skeletal muscle is also called striated muscle because of the regular arrangement of myofilaments creates a pattern of light and dark bands The functional unit of a muscle is called a sarcomere and is bordered by Z lines Thin filaments are anchored to the ends of the sarcomere at the Z Thick filaments are anchored to the middle of the sarcomere at the line M line Sliding filament model of muscle contraction Sliding Filament model filaments slide past each other longitudinally producing more overlap between thin and thick filaments Sliding filaments rely on interaction between actin and myosin Head of myosin molecule bind to an actin filament forming a cross bridge and pulling the thin filament toward the center of the sarcomere Muscle contraction requires repeated cycles of binding and release ATP supports sustained muscle contractions Role of Calcium and Regulatory proteins Regulatory protein Tropomyosin and the tropin complex a set of additional proteins bind to actin strands on thin filaments when a muscle fiber is at rest Prevents actin and
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