Warm up

1. Warm up • Why are senses important to all living things? • Which sense do you utilize for the following situations: • Eating your favorite food? • Someone is whispering to you? • When using a mirror in the morning? • When purchasing perfume?

2. Peripheral Nervous System • Nerves and ganglia outside the central nervous system • Nerve = bundle of neuron fibers • Neuron fibers are bundled by connective tissue

3. Endoneurium surrounds each fiber • Groups of fibers are bound into fascicles by perineurium • Fascicles are bound together by epineurium Structure of a Nerve

4. Classification of Nerves • Mixed nerves – both sensory and motor fibers • Afferent (sensory) nerves – carry impulses toward the CNS • Efferent (motor) nerves – carry impulses away from the CNS

5. Cranial Nerves • 12 pairs of nerves that mostly serve the head and neck • Numbered in order, front to back • Most are mixed nerves, but three are sensory only

6. Distribution of Cranial Nerves

7. Cranial Nerves • I Olfactory nerve – sensory for smell • II Optic nerve – sensory for vision • III Oculomotor nerve – motor fibers to eye muscles • IV Trochlear – motor fiber to eye muscles

8. V Trigeminal nerve – sensory for the face; motor fibers to chewing muscles • VI Abducens nerve – motor fibers to eye muscles • VII Facial nerve – sensory for taste; motor fibers to the face and scalp • VIII Vestibulocochlear nerve – sensory for balance and hearing Cranial Nerves

9. IX Glossopharyngeal nerve – sensory for taste; motor fibers to the pharynx • X Vagus nerves – sensory and motor fibers for pharynx, larynx, lungs, and viscera • XI Accessory nerve – motor fibers to neck and upper back; and thoracic and abdominal viscera • XII Hypoglossal nerve – motor fibers to tongue Cranial Nerves

10. There is a pair of spinal nerves at the level of each vertebrae for a total of 31 pairs • Spinal nerves are formed by the combination of the ventral and dorsal roots of the spinal cord • Spinal nerves are named for the region from which they arise Spinal Nerves

11. Spinal Nerves

12. Spinal nerves divide soon after leaving the spinal cord • Dorsal rami – serve the skin and muscles of the posterior trunk • Ventral rami – forms a complex of networks (plexus) for the anterior Anatomy of Spinal Nerves

13. Examples of Nerve Distribution

14. Nerves • Somatic – one motor neuron • Autonomic – preganglionic and postganglionic nerves • Effector organs • Somatic – skeletal muscle • Autonomic – smooth muscle, cardiac muscle,and glands Differences Between Somatic and Autonomic Nervous Systems

15. The involuntary branch of the nervous system • Consists of only motor nerves • Divided into two divisions • Sympathetic division • Parasympathetic division Autonomic Nervous System

16. Comparison of Somatic and Autonomic Nervous Systems

17. Sympathetic Pathways

18. Anatomy of the Autonomic Nervous System

19. Autonomic Functioning • Sympathetic – “fight-or-flight” • Response to unusual stimulus • Takes over to increase activities • Remember as the “E” division = exercise, excitement, emergency, and embarrassment

20. Autonomic Functioning • Parasympathetic – housekeeping activities • Conserves energy • Maintains daily necessary body functions • Remember as the “D” division - digestion, defecation, and diuresis

21. Sensory Receptors • Sensory receptors allow the body to respond to stimuli caused by changes in our internal or external environment. • Receptors respond by converting the different stimuli to electrical impulse. • Receptors can adapt to decrease intensity of stimulus

22. Distribution of Receptors • General (Somatic) Senses • Widely distributed around the body in the skin, mucosa, connective tissue, muscles, joints, tendons and viscera • Special Senses (smell, taste, sight, hearing and balance) • Grouped in localized areas of complex organs

23. Classification of Receptors (location) • Exteroreceptor: • located on body surface respond to touch, pressure, temperature and pain • Visceroreceptors: • Located internally, often within body organs, or viscera. Provide body with information about internal environment (e.g., pressure, stretch, chemical changes, hunger, thirst) • Proprioceptors: • Special type of visceroceptor.Location limited to skeletal muscle, joint capsules, and tendons. Provide information on body movement, orientation in space, and muscle stretch

24. Classification of Receptors (Stimuli) • Mechanoreceptors: • activated when “deformed” to generate receptor potential • Chemoreceptors: • activated by amount or changing concentration of certain chemicals (e.g., taste and smell) • Thermoreceptors: • activated by changes in temperature (Figure 15-3) • Nociceptors: • activated by intense stimuli that may damage tissue; sensation produced in pain (Figure 15-2) • Photoreceptors: found only in the eye; respond to light stimuli if the intensity is great enough to generate a receptor potential • Osmoreceptors: • concentrated in the hypothalamus; activated by changes in concentration of electrolytes (osmolarity) in extracellular fluids

25. Special senses have sensory receptors located within relatively large, sensory organs in the head; Nose –Olfactory (smell) Tongue –Gustatory (taste) Eyes – vision Ears – hearing and equilibrium Special Senses

26. Nose • Smell receptors • Olfactory receptors • Chemoreceptors • Respond to changes in chemical concentrations • Chemicals must be dissolved in the mucus of the noseto activate smell receptors

27. Smell Sensation Smell receptors are activated, they send their information to the olfactory nerves send the information along olfactory bulbs and tracts different areas of the cerebrum cerebrum interprets the information as a particular type of smell

28. Smell undergoes sensory adaptation Same chemical can only stimulate smell receptors for a limited amount of time Smell receptors no longer respond to the chemical and you can no longer smell You smell perfume when you first encounter it but in a few minutes, you no longer smell it. Smell Sensation (cont.)

29. Apply Your Knowledge You notice an odor coming from a classmate when you enter the room. Why would that person not be able to smell it?

30. Apply Your Knowledge-Answer You notice an odor coming from a classmate when you enter the room. Why would that person not be able to smell it After a few minutes, smell receptors no longer respond to the chemical and the persont can no longer smell the odor.

31. Tongue • Taste or gustatory receptors –taste buds • Found on "the bumps" of the tongue (papillae) • Taste buds are microscopic • Also on roof of your mouth and walls of your throat Click for Larger View

32. Tongue (cont.)

33. Taste Sensation • Four types of taste cells - activated by a particular group of chemicals • Sweet - tip of the tongue. • Sour - sides of the tongue. • Salty - tip and sides of the tongue. • Bitter - back of the tongue

35. VISION: THE EYE Accessory structures Eyebrows and eyelashes give some protection against foreign objects entering the eye; cosmetic purposes Eyelids consist of voluntary muscle and skin with a tarsal plate Lined with conjunctiva, a mucous membrane Palpebral fissure: opening between the eyelids Angle or canthus: where the upper and lower eyelids join

38. Eye • Outer layer • Sclera • Cornea • Middle layer • Choroid • Iris • Ciliary body • Inner layer • Retina – contains rods and cones

40. Eye (cont.) Outer layer: • Sclera is the “white of the eye” and does not allow light to enter the eye • Cornea - anterior to the sclera • Allows light to enter the eye (“window of the eye”) • Contains sensory receptors can detect even the smallest of particles

41. Eye (cont.) Middle layer: • Also called vascular and pigmented layer • Richly supplied with blood vessels and pigments • Choroid lines the sclera and absorb extra light • Ciliary body functions to hold and move the lens to focus the eye. • Cloudy areas on the lens are called “cataracts.” • Hole in iris is called the pupil.

42. Eye (cont.) Inner layer: • Also called the retina • Richly supplied with blood vessels and pigments • Contains visual receptors called rods and cones • Rods allow us to detect black, white, and gray shades and images in dim light. • Cones allow us to see images in bright light • Cones allow us to see color.

43. Eye (cont.) • Eyelid- skin, muscle, and dense connective tissue. • Orbicularis oculi muscle and is responsible for blinking • Conjunctivas- mucous membranes • Line the inner surfaces of the eyelids • Fold back onto the anterior surface of each eyeball

44. Eye (cont.) • Vitreous humor • Lens • Choroid • Sclera • Retina • Pupil • Iris • Cornea • Conjunctiva Draw a line to each part of the eye.

46. Lacrimal apparatus consists of lacrimal glands and nasolacrimal ducts. Mostly water but also contain enzymes that can destroy bacteria and viruses Lacrimal glands are on the lateral edge of each eyeball and they produce tears. Outer oily layer that prevents them from evaporating Tears When a person cries, the abundance of tears entering the nose produces the “runny nose” associated with crying.

47. Extrinsic eye muscles are skeletal muscles that move the eyeball Each eyeball has 6 extrinsic eye muscles attached to them that move the eyeball Superiorly Inferiorly Laterally Medially Eye Muscles

48. Eye works like a camera light passes through the cornea, pupil, lens and fluids of the eye, which focuses the light onto the retina The image is projected upside down on the retina Retina converts the light into nerve impulses that are sent to the brain Process of Seeing The brain interprets these impulses, turns the image right-side up and develop a picture of the object.

49. Choroid Absorbs extra light in eye Ciliary Body Holds lens, moves lens for focusing Iris Controls amount of light entering eye Lens Focuses light onto retina Parts of the Eye

50. Retina Contains visual receptors Rods Allow vision in dim light, detect black-and-white images, detect broad outlines of images Cones Allow vision in bright light, detect colors, detect details Optic Nerve Carries visual information from rods and cones toward the brain Parts of the Eye (cont.)