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Nervous System – Sensory Systems

Nervous System – Sensory Systems. Biol 105 Lecture 11 Chapter 9. Concepts to Know:. Depolarization is caused by ______ ions entering or leaving (which one) the axon The gap in between two neurons is called the ________.

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Nervous System – Sensory Systems

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  1. Nervous System – Sensory Systems Biol 105 Lecture 11 Chapter 9

  2. Concepts to Know: • Depolarization is caused by ______ ions entering or leaving (which one) the axon • The gap in between two neurons is called the ________. • What is the name for the chemicals that are held in vesicles and released from one neuron, and bind to receptors of the next neuron? • What part of the autonomic nervous system stimulates digestion? • What is the thin outer layer of the cerebrum where most of the higher thinking and processing takes place called • The part of the brain that processes sensory information (except smell) is called the ______.

  3. Outline • Senses • Sensory receptors • Touch • Vision • Hearing and balance • Smell

  4. Senses • Major senses – touch, hearing, smelling, taste, and seeing. • All the sensory nerves are routed through the thalamus except the nerves for smell.

  5. Sensory receptor cells • Sensory receptors are specialized structures that detect stimuli (stimulus) • Sensory receptor cells change the stimulation into an electrical response that is transmitted through the nerves • If a sensory receptor is continuously stimulated, it will stop responding = sensory adaptation

  6. 12.2 The Central Nervous System 12-18

  7. 12-28

  8. Touch • We can sense different things through touch: • Thermal • Tactile • Pain • Vibration

  9. Figure 9.2 Sense receptors of the skin

  10. Figure 9.2 Sense receptors of the skin

  11. Types of receptors in the skin • Free nerve endings • Merkel disks • Meissner’s corpuscles • Pacinian corpuscles • Ruffini corpuscles • Thermoreceptors

  12. Free Nerve Endings • Free nerve endings – tips of dendrites of sensory neurons (free nerve endings may be wrapped around hair), detect touch and pain

  13. Figure 9.2 Free nerve endings

  14. Figure 9.2 Free nerve endings

  15. Merkel Disks • Merkel disks – comprised of free nerve endings and Merkel cells, detect touch

  16. Merkel disk

  17. Meissner’s corpuscles • Meissner’s corpuscles – encapsulated nerve endings - detect light touch, tell us exactly where we were touched

  18. Meissners corpuscle

  19. Pacinian corpuscles • Pacinian corpuscles – layers of tissues surround the nerve ending, detects pressure when first applied, important in sensing vibration

  20. Pacinian corpuscle

  21. Ruffini corpuscles • Ruffini corpuscles – encapsulated nerve endings in deep layers that respond to continuous pressure

  22. Ruffini corpuscle

  23. Thermoreceptors • Thermoreceptors – specialized nerve endings, detects changes in temperature.

  24. Vision • Sight is complex: • Light enters the eye, it is focused, then the light has to be transformed into it into an electrical signal that then has to be processed.

  25. Vision • Light enters through the cornea • The lens focuses it to the back of the eye • The retina is a layer at the back of the eye where light is transformed into electrical signals

  26. Optic nerve Optic disk (blind spot) Fovea Sclera Choroid Retina Vitreous humor (fills the posterior chamber) Lens Ciliary body Aqueous humor (fills the anterior chamber) Cornea Pupil Iris Sclera Figure 9.4

  27. Layers of the Eye – Outer layer • The sclera • Protects and shapes the eye • Provides attachment for muscles • The cornea • Allows light to enter

  28. Outer Layer of Eye Table 9.1 (1 of 4)

  29. Middle Layer of Eye • The choroid • Contains blood vessels that supply nutrients and oxygen. • Contains melanin, absorbs light reflected from the retina • The ciliary body • A ring of muscle that functions to focus the lens on the retina

  30. Middle Layer of Eye • The iris • The colored portion of the eye • Contains smooth muscle that dilates or constricts to regulate the amount of light entering the eye • The pupil • The opening in the center of the iris that lets light into the eye

  31. Middle Layer of the Eye Table 9.1 (2 of 4)

  32. Inner Layer of Eye • Contains: • Retina • Photoreceptors - Rods and Cones • Fovea

  33. Inner Layer of Eye - Retina • The retina contains photoreceptors • Rods • Cones – detect color • The fovea is a pit in the retina with a high concentration of cones

  34. Vision Depends on the Eye Table 9.1 (3 of 4)

  35. Structures of the Eye • Optic Nerve • Fluid • Aqueous humor • Vitreous humor • Lens

  36. Optic Nerve • The optic nerve • Carries visual information to the brain • Forms a blind spot where it leaves the retina

  37. Fluid in the Eye • There are two fluid filled chambers in the eye • Vitreous humor – jelly like fluid in posterior chamber. Holds retina against the wall of the eye • Aqueous humor – clear fluid in anterior chamber. Supplies nutrients and oxygen to cornea and lens, removes the waste. Creates pressure in eye to maintain shape of eye.

  38. Lens • The lens can change shape to focus on near and far objects. • Focuses the light onto the retina • Ciliary muscles are attached to lens by ligaments

  39. Vision Depends on the Eye Table 9.1 (4 of 4)

  40. Photoreceptors • Cones and Rods have pigments that absorb • Cones work best in bright light and provide color vision • Rods work in low light situations but can only provide black and white vision

  41. Photoreceptors • The photoreceptors (rods and cones) have pigments that absorb light • When there is no light coming in, they are releasing neurotransmitters (opposite of most receptors) • When they absorb light they stop releasing neurotransmitters

  42. Photoreceptors • The neurotransmitters are inhibitory • When the neurotransmitters diminish, cells that process the information are stimulated • This information from these cells (bipolar and ganglion cells) is transmitted to the optic nerve to the thalamus to the visual cortex

  43. Light Choroid Sclera Retina Blind spot (a) Light enters the left eye and strikes the retina. Figure 9.8a

  44. Light Vitreous humor Ganglion cell layer Electrical signals Bipolar cell layer Retina Cone Photoreceptor cells Rod Pigment layer Axons Choroid Sclera Figure 9.8b

  45. Light Retina Optic nerve Visual cortex (c) The axons of the ganglion cells leave the eye at the blind spot, carrying nerve impulses to the brain (viewed from below) by means of the optic nerve. Figure 9.8c

  46. Rods and Cones Rod cell Cone cell Figure 9.9 (2 of 2)

  47. Which part of the human eye detects colored light? • Pupil • Rods • Cones • Cornea

  48. A ring of muscle that functions to focus the lens on the retina is the: • Iris • Choroid • Ciliary body • Sclera

  49. Figure 9.10 A standard test for color blindness

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