Warm-Up

1. Warm-Up • What is the function of: • Cone cells? • Rod cells? • The perceived pitch of a sound is dependent on… ? • What is the difference between perception and sensation?

2. Warm-Up • What is the function of: • Cone cells? Color • Rod cells? Light • The perceived pitch of a sound is dependent on… ? wavelength (λ) • What is the difference between perception and sensation?

3. Chapter 50 Campbell Biology – 9th Edition Sensory and Motor Mechanisms

4. You must know • The location and function of several types of sensory receptors • How skeletal muscles contract • Cellular events that lead to muscle contraction

5. Sensory Receptors • Mechanoreceptors: physical stimuli – pressure, touch, stretch, motion, sound • Thermoreceptors: detect heat/cold • Chemoreceptors: transmit solute conc. info – taste (gustatory), smell (olfactory) • Electromagnetic receptors: detect EM energy – light (photoreceptors), electricity, magnetism • Pain receptors: respond to excess heat, pressure, chemicals

6. Chemoreceptors: antennae of male silkworm moth have hairs sensitive to sex phermones released by the female Eye Infrared receptor This rattlesnake and other pit vipers have a pair of infrared receptors, one between each eye and nostril. The organs are sensitive enough to detect the infrared radiation emitted by a warm mouse a meter away. Some migrating animals, such as these beluga whales, apparently sense Earth’s magnetic field and use the information, along with other cues, for orientation.

7. Reception: receptor detects a stimulus • Sensation = action potentials reach brain via sensory neurons • Perception: information processed in brain

8. Structure of the Human Ear Middle ear Outer ear Inner ear Semicircular canals Stapes Skull bones Middle ear Incus Auditory nerve, to brain Malleus Tympanic membrane Pinna Auditory canal Eustachian tube Cochlea Oval window Round window Tympanic membrane Eustachian tube Tectorial membrane Hair cells Bone Cochlea duct Auditory nerve Vestibular canal Tympanic canal Basilar membrane Axons of sensory neurons To auditory nerve Organ of Corti

9. Equilibrium in the inner ear: Semicircular canals (fluid-filled chambers) detect head movements through hairs of receptor cells Semicircular canals Ampulla Flow of endolymph Flow of endolymph Vestibular nerve Cupula Hairs Hair cell Vestibule Nerve fibers Utricle Body movement Saccule

10. Structure of the Vertebrate Eye(also some invertebrates) Choroid Sclera Retina Ciliary body Fovea (center of visual field) Suspensory ligament Cornea Iris Optic nerve Pupil Aqueous humor Lens Central artery and vein of the retina Vitreous humor Optic disk (blind spot)

11. Vision Retina Optic nerve To brain Compound eyes: several thousand ommatidia (light detectors) with its own lens; insects & crustaceans Vertebrates: • Rods: sense light • Cones: color vision • Rhodopsin: light-absorbing pigment that triggers signal transduction pathway that leads to sight Retina Photoreceptors Neurons Cone Rod Amacrine cell Horizontal cell Optic nerve fibers Ganglion cell Bipolar cell Pigmented epithelium

12. Types of Skeletons • Hydrostatic: fluid held under pressure in closed body compartment • Hydra, nematodes, annelids • Exoskeletons: hard encasements on surface of animal • Insects, mollusks, crustaceans • Endoskeleton: hard supporting elements buried within soft tissues • Human bony skeleton

13. Key Head of humerus Axial skeleton Skull Examples of joints Appendicular skeleton Scapula Clavicle Shoulder girdle Scapula Sternum Ball-and-socket joints, where the humerus contacts the shoulder girdle and where the femur contacts the pelvic girdle, enable us to rotate our arms and legs and move them in several planes. Rib Humerus Vertebra Radius Humerus Ulna Pelvic girdle Carpals Ulna Phalanges Metacarpals Hinge joints, such as between the humerus and the head of the ulna, restrict movement to a single plane. Femur Patella Tibia Fibula Ulna Radius Pivot joints allow us to rotate our forearm at the elbow and to move our head from side to side. Tarsals Metatarsals Phalanges

14. Human Grasshopper Extensor muscle relaxes Biceps contracts Tibia flexes • Muscles always contract • Muscles work in antagonistic pairs to move parts of body Flexor muscle contracts Forearm flexes Triceps relaxes Biceps relaxes Extensor muscle contracts Tibia extends Forearm extends Flexor muscle relaxes Triceps contracts

15. Skeletal Muscle Structure Muscle Bundle of muscle fibers • Attached to bones by tendons • Types of muscle: • smooth (internal organs) • cardiac (heart) • Skeletal (striated) • 1 long fiber = single muscle cell • Each muscle fiber = bundle of myofibrils, composed of: • Actin: thin filaments • Myosin: thick filaments Nuclei Single muscle fiber (cell) Plasma membrane Myofibril Light band Z line Dark band Sarcomere TEM 0.5 µm I band A band I band M line Thick filaments (myosin) Thin filaments (actin) Z line H zone Z line Sarcomere

16. Sarcomere: basic contractile unit of the muscle 0.5 µm Z H I A Sarcomere Relaxed muscle fiber Contracting muscle fiber Fully contracted muscle fiber Z lines – border I band – thin actin filaments A band – thick myosin filaments

17. Muscle Contraction: 0.5 µm Z H I A Sarcomere Relaxed muscle fiber Contracting muscle fiber Fully contracted muscle fiber • Sarcomere relaxed: actin & myosin overlap • Contracting: • Muscle fiber stimulated by motor neuron • Length of sarcomere is reduced • Actin slides over myosin • Fully contracted: actin & myosin completely overlap Sliding-filament model: thick & thin filaments slide past each other to increase overlap (Note: Filaments do NOT shorten!)

18. Muscle fibers only contract when stimulated by a motor neuron Motor neuron axon Mitochondrion Synaptic terminal T tubule Sarcoplasmic reticulum Ca2+ released from sarcoplasmic reticulum Myofibril Sarcomere Plasma membrane of muscle fiber

19. Synaptic terminal of motor neuron releases acetylcholine Muscle fiber depolarizes Ca2+ released Initiate sliding of filaments Synaptic terminal of motor neuron PLASMA MEMBRANE Synaptic cleft T TUBULE ACh SR Ca2+ CYTOSOL Ca2+

20. Depolarization of muscle cell releases Ca2+ ions  binds to troponin expose myosin sites on actin Tropomyosin Ca2+-binding sites Troponin complex Actin Myosin-binding sites blocked. Ca2+ Myosin- binding site Myosin-binding sites exposed.

21. Hydrolysis of ATP by myosin  cross-bridge formed  thin filament pulled toward center of sarcomere Thick filament Thin filaments Thin filament Myosin head (low-energy configuration) Thick filament Cross-bridge binding site Thin filament moves toward center of sacomere. Actin Myosin head (low- energy configuration) Myosin head (high- energy configuration) Cross-bridge

22. Speed of muscle contraction: • Fast fibers – brief, rapid, powerful contractions • Slow fibers – sustain long contractions (posture)

23. Problems • ALS (Lou Gehrig’s disease): degeneration of motor neurons, muscle fibers atrophy • Botulism: block release of acetylcholine, paralyzes muscles • Myasthenia gravis: autoimmune disorder, produce antibodies to acetylcholine • Calcium deficiency: muscle spasms and cramps • Rigor mortis (after death): no ATP to break actin/myosin bonds; sustained muscle contraction until breakdown (decomposition)