The document summarizes sensory and motor mechanisms in the human body. It describes how sensing, analysis, and action are ongoing and overlapping processes in the brain. Sensory receptors convert stimulus energy like pressure, chemicals, light, and temperature into action potentials. The limbic region determines the importance of sensory input. Hearing and balance both use hair cells in the inner ear that detect fluid movements. Taste and smell receptors detect chemicals and signal the brain. Vision uses rods and cones in the retina that contain photopigments to detect light. Muscle contraction occurs via the sliding filament model as myosin cross-bridges pull actin fibers toward the center of the sarcomere.

1. Sensory and Motor Mechanisms AP Chapter 50

10. Hearing http://msjensen.cehd.umn.edu/1135/Links/Animations/Flash/0019-swf_effect_of_soun.swf The three small bones transmit vibrations To the inner ear which contains fluid-filled canals.

11. Air pressure vibrates fluid in canals which vibrate the basilar membrane, bending the hairs of its receptor cells against the tectorial membrane which opens ion channels and allows K+ to enter the cells and cause a depolarization and releases neurotransmitters to continue to the auditory nerve to the brain.

12. Frequency (pitch) determined by areas of basilar membrane that vibrate at different frequencies; areas are thick and thin

20. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.24

24. Light hits the retina and then comes back through the cells to the optic nerve.

25. Photoreceptors

26. Rods and cones have visual pigments embedded in a stack of folded membranes or disks in each cell. Retinal is the light-absorbing pigment and is bonded to a membrane protein – opsin . Combo – rhodopsin.

27. When retinal absorbs light, it changes shape and separates from opsin. In the dark, the retinal is converted back to its original shape.

29. Notice in the light, the Na + channels are closed.

32. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.24

34. Locomotion and muscle action

35. How the muscle cell is organized Animations This is ONE muscle cell, called a muscle fiber. for energy The muscle fiber (cell) is made up of many myofibrils which in turn are made up of sarcomeres, the units of contraction.

37. The contracting unit is the sarcomere. Fig. 50-25b TEM Thick filaments (myosin) M line Z line Z line Thin filaments (actin) Sarcomere 0.5 µm

38. The sliding filament model When the sarcomere contracts, the filaments slide over each other. They do not change length.

45. Mechanism of Filament Sliding at the Neuromuscular Junction Mechanism of Filament Sliding

49. Protein models of muscle action