Peripheral Nervous System

1. What are the anatomical components of the peripheral nervous system (PNS)? What is the functional organization of the PNS? In other words, can you schematically explain the organization of the efferent division (somatic nervous system (SNS) and autonomic nervous system (ANS)) and the afferent division of the PNS?

a. Cranial and spinal nerves.

b. There are two divisions of the PNS:

i. Afferent-Sensory (somatosensory, special senses and visceral senses).

ii. Efferent -Somatic (skeletal muscle); Autonomic (cardiac, smooth muscle, glands and adipose)--Sympathetic, parasympathetic and enteric

2. How many pairs of cranial nerves are there? Are these nerves mixed? In other words, do all cranial nerves contain both sensory and motor nerve fibers?

a. 12.

b. Yes, some, but not all, are mixed.

i. Cranial nerves 1, 2, and 8 are sensory.

ii. Cranial nerves 3,.4,.6, 1 and 12 are motor.

iii. Cranial nerves 5, 7, 9, and 10 are sensory and motor.

3. How many pairs of spinal nerves are there? What are the different types of intervertebral disc abnormalities that can occur? How can these issues relate to spinal stenosis?

a. 31; disc deterioration and herniation.

Disc deterioration and herniation can lead to spinal stenosis causes narrowing of the open spaces in your spine. This can put pressure on your spinal cord and the nerves.

4. What is a ventral root composed of? A dorsal root? A dorsal root ganglion? A ventral ramus? A dorsal ramus? Sympathetic chain ganglia? What two components of the PNS combine to form a spinal nerve?

a. Ventral -- motor neurons.

b. Dorsal -- sensory neurons.

c. Dorsal root ganglion --unipolar neurons.

d. Ventral ramus going to the front of the body

e. Dorsal ramus going to the back of the body

f. Sympathetic chain ganglia are bundle of nerve fibers- autonomic nervous system.

g. Ventral and dorsal roots.

5. Can you draw a spinal reflex arc? What are the three neurons involved? How do they communicate with one another? What does ipsilateral mean? Contralateral?

a.

b. Afferent, inter and motor neuron.

c. They communicate through the neurotransmitters that are released in the synaptic clefts between them.

d. During an ipsilateral reflex the response occurs on the side of the body that is stimulated.

e. Contralateral: opposite side.

6. If you touched a hot stove with your hand, you would reflexively remove your hand from the stove. Does the brain regulate this muscle activity required to remove your hand? Do you sense the pain before or after your hand is withdrawn?

a. No.

b. The pain is perceived in the brain after the hand is withdrawn.

7. Sensory information enters the afferent division of the PNS. What are exteroceptors? What type of information do the send to the CNS? What are proprioceptors? What type of information do the send to the CNS? What are interoceptors? What type of information do the send to the CNS?

a. Exteroceptors are sensory receptors that receives external stimuli. Special and somatic senses.

b. Gustatory, visual, olfactory, auditory, equilibrioception, pain, temperature, pressure, etc.

c. Proprioceptors are sensors that provide information about joint angle, muscle length, and muscle tension, which is integrated to give information about the position of the limb in space.

d. Interoceptors are receptors that receives stimuli of internal organs. Visceral sense, as in stomach or heart pain for example.

8. What are mechanoreceptors? What are some general examples? What are the three examples of tactile receptors in the skin? Which receptors detect a gentle touch? The rumble of an earth quake? Someone pressing down firmly on your skin?

a. Mechanoreceptors respond to mechanical stimuli.

b. Tactile receptors, baroreceptors and proprioceptors.

c. Pacinian corpuscles, Meissner's corpuscles and Merkel cells.

d. Merkel cells and Meissner's corpuscles.

e. Meissner's and Pacinian corpuscles.

f. Pacinian corpuscles.

9. Which receptors would inform you of an ice cube that was just placed on your arm? The taste of a cup of coffee? The pain of stepping on a nail?

a. Thermoreceptors.

b. Chemoreceptors.

c. Nociceptors and mechanoreceptors

10. Do tactile receptors undergo receptor or generator potentials? The receptor portion of one of these sensory neurons is literally a modification of what portion of the neuron? What happens to the membrane of the receptor as a result of receiving stimulus? Which ion enters the neuron to generate an AP? Where does this first AP arise? Where is tactile sense processed in the brain?

a. Generator.

b. Dendrite.

c. Mechanically-gated ion channels open.

d. Na+.

e. Initial segment of the axon.

f. Somatosensory cortex.

11. Stimuli can be sensed to varying degrees. Information regarding varying degrees of intensity (for example, visualizing a dim white screen vs. a bright white screen) is coded in the form of varying AP frequencies. What is responsible for generating these differences in AP frequency? In other words, AP frequency is directly proportional to?

a. The frequency at which presynaptic neurons cause EPSPs on that neuron.

12. Are nociceptors tonic or phasic receptors? When you put on your shirt/top/blouse in the mooring you can feel it on your skin, however, several hours later the feeling is "gone." Based on this fact, are tactile receptors tonic or phasic?

a. Tonic (slowly adapting).

b. Phasic (quickly adapting).

13. Which parts of your body have the ability to discern between two separate pin pricks in very close proximity to one another? What does this ability tell you about the size of the nociceptive receptive fields in these regions of the body?

a. Finger tips and toes.

b. Receptor fields are smaller in the hands and feet.

14. There are myriad nociceptive stimuli. What are some of these triggers for pain? If you had a lesion on your arm, what medications could you take to reduce the activity of prostaglandins? Histamine? Substance P? What's another name for endogenous morphine? Exogenous morphine? Does nociceptive information travel to the brain contralaterally or ipsilaterally?

a. Substance P, histamine and prostaglandins.

b. Prostaglandins: aspirin.

c. Histamine: NSAIDs.

d. Substance P: capsaicin.

e. Opiates.

f. Morphine.

g. Contralaterally.

15. The phenomenon of referred pain is thought exist as the result of "cross-talk between neurons." Where is it believed that this cross-talk to occurs? Can you use this information to explain how an individual can experience pain in the arm when they are having chest pain due to a heart attack?

a. Spinal cord gray mater.

b. When a person is having a heart attack the pain fibers in the heart and hand go to the spinal cord and they converge (cross talk) and the pain fibers from the hear can induce action potentials in the pain fiber coming from the arm.

16. What are the five different types of special senses? Based on your list, would you expect these senses to enter the nervous system at the level of the spinal cord or brain?

a. taste (gustation), smell (olfaction), sight (vision), hearing (audition) and balance/equilibrium (equilibrioception)

b. Brain.

17. What are the five different tastes we can perceive? What is/are the tastants(s) for each of these different tastes? Each taste cell uses a single receptor. As tastants have varied signaling mechanisms, do they also trigger the release of different neurotransmitters from the receptor?

a. Five different tastes:

i. Bitter: coffee, beer, unsweetened cocoa, earwax

ii. Sweet: monosaccharides

iii. Umami: glutamate

iv. Sour: protons

v. Salt: Na

b. No, they all result in the release of glutamate from the taste receptor cell.

18. Which type of graded potentials do taste receptors underdo? How many cells are involved in the peripheral processing of gustatory information? In what cell are APs generated?

a. Receptor potentials.

b. 2. The taste receptor cell and the bipolar sensory neuron.

c. The bipolar sensory neuron.

19. Which region of the cortex of your brain determines if something is sour? In which region of the cortex of your brain do you determine if you like the taste of sour or not?

a. Gustatory cortex.

b. Frontal cortex.

20. Which type of graded potentials do odorant receptors underdo? How many cells are involved in the peripheral processing of olfactory information? In what cell are APs generated?

a. Generator potentials.

b. 2. The primary bipolar sensory neuron and the secondary sensory neuron.

c. The secondary neuron.

21. Thinking anatomically, can you explain why smell is the only special sense that does not enter the brain by relaying through the thalamus?

a. Because the primary neurons enter the brain through tiny holes in the floor of the cranium and synapse with the secondary neurons in the olfactory bulbs at the base of the brain.

22. Are odorant receptors phasic or tonic? Can you justify your choice by explaining why we add mercaptan to natural gas?

a. Phasic.

b. Mercaptan a sulfur-containing compound and is a component of garlic. We add it to natural gas so we can smell it since natural gas is odorless.

23. What are the three layers of the eyeball and what composes each layer. Which layer is most visceral? Parietal? Which layer contains photoreceptors? Which layer forms the cornea? Which layer forms the ciliary body? Which layers forms the iris?

i. Sclera: thick connective tissue; "white" of the eyeball

ii. Choroid: blood supply, forms ciliary body & iris.

iii. Retina: photoreceptors (rods and cones), bipolar cells and ganglion cells.

24. What is the relationship between the lens, the ciliary body and suspensory ligaments?

a. The lens is attached to the ciliary body via the suspensory ligaments.

25. Where is aqueous humor located? Vitreous humor? What are the functions of these humors? What is glaucoma?

a. In the anterior chamber of the eye.

b. In the posterior chamber of the eye.

c. The aqueous humor plays an essential role in nourishing the cornea and the lens by supplying nutrition such as amino acids and glucose. It also maintains intraocular pressure. The vitreous humor (or body) allows the light to pass through the lens to the retina and helps to keep the eye in its round shape.

d. Glaucoma is the term applied to a group of eye diseases that gradually result in loss of vision by permanently damaging the optic nerve. This disease can occur due to high pressure in the eye due to an overaccumulation of fluid (aqueous humor).

26. If you were to stand straight and look straight ahead, where would most light entering your pupil light fall on your retina? What is the visual axis (i.e., principal optical axis)? What is the optic disc? Why is it also known as the blind spot? Can you find your blind spot?

a. Fovea centralis.

b. The visual axis is an imaginary straight line that passes through both the center of the pupil and lands on the center of the fovea centralis.

c. The optic disc optic is the point of exit for ganglion cell axons leaving the eye. There are no photoreceptors in this area. Therefore, is known as the blind spot.

d. Use the diagram in the slides to find your blind spot.

27. You are looking at a red ball. Which colors (wavelengths) of visible light are absorbed by the ball? Reflected? What does it mean the reflected photons are pixels of the image of the ball that forms on your retina?

a. All but red.

b. Red.

c. Photons reflect form every point of an object. So, the photons reveal not only the color or an object, but also its shape, photon by photon (or pixel by pixel).

28. What is refraction? What is a refractive index? What is the refractive index of air? Water? The cornea? The lens? If light passes from a medium with a refractive index of 2.0 into a medium with a refractive index of 1.0, what will happen to the light rays?

a. Refraction: bending of light rays as they pass through different refractive media.

b. A number that reflects the degree to which a particular medium bends light rays. Larger numbers bend light more than smaller numbers.

c. 1.00.

d. 1.33.

e. 1.38.

f. 1.41.

g. They will diverge. If light comes from a medium with a lower refractive index and enters a medium with a higher refractive index, then the light rays will converge.

29. The human lens is concave or convex? Does it converge or diverge light rays? What do converging and diverging mean in reference to the visual axis? What is the focal length? Focal point? A diopter is a unit of converging or diverging power? Which structure of the eye plays the most important role in focusing light on the retina?

a. Convex.

b. Converge.

c. Converge = towards the visual axis and diverge = away from the visual axis.

d. The distance between the center of the lens and the focal point.

e. Where the light rays converge after passing through the lens.

f. Converging.

g. Cornea (it has the highest converging power).

30. The refractive index of the cornea is 1.38 while that of water is 1.33. If the two indices are so similar, why don't humans have clear vision underwater? How do swimming goggles help improve your underwater vision?

a. The problem is that they are too similar, so light rays don't converge much. This causes the focal point to form behind the retina. It is sort of like being hyperopic.

b. Restores the air-corneal interface.

31. What are the ways in which the image formed on your retina is different than the object itself?

a. Inverted (up and down and right to left) and a fraction of the actual size of the obect.

32. When is the triad of near reflex employed? What is lens accommodation? What is the state of the ciliary body, suspensory ligaments and lens when and object is more than 20 feet away? Less than 20 feet away?

a. The triad of near reflex is employed in response to focusing on a near object (closer than 20 ft. from the eye).

b. Lens accommodation = eye increasing its converging power by making lens more convex.

c. More than 20 feet away:

i. Ciliary muscles are relaxed, suspensory ligaments are taut and the lens is flattened out.

d. Less than 20 feet away:

i. Ciliary muscles are contracted, suspensory ligaments are loose and the lens is bulged (or very convex).

33. If the ciliary muscles of the eye are relaxed, which receptor must be activated? What neurotransmitter(s) is binding to the receptor?

a. B2 receptors.

b. Norepinephrine.

34. Suppose the suspensory ligaments are loose, which receptor must be activated in the ciliary muscle? Which neurotransmitter is causing this response?

a. M3.

b. Acetylcholine

35. What is miosis? Mydriasis? What are the muscles of the iris that control the diameter of the pupil? Which dilate it? Which constrict it? The pupil is not an anatomical structure. How can it be likened to a black hole of the universe?

a. Pupillary constriction.

b. Pupillary dilation.

c. Pupillary constrictor (sphincter) muscles and pupillary dilator (radial) muscles.

d. Pupillary constrictor (sphincter) muscles.

e. Pupillary dilator (radial) muscles.

f. All light enters the pupil, but none exits it. That is why it appears black.

36. Can you list a few drugs that would cause miosis? What receptors are responsible for miosis? Neurotransmitter? Can you list a few drugs that would cause mydriasis? What receptors are responsible for mydriasis? Neurotransmitter(s)?

a. Opiates (such as heroin or morphine) and other central nervous system depressants such as benzodiazepines and barbiturates will give you small pupils while under the influence of the drug.

b. M3.

c. Acetylcholine.

d. Stimulant drugs like cocaine, amphetamines, methamphetamines and ecstasy will give you big pupils - along with cannabis (marijuana) - and hallucinogenic drugs like LSD and ketamine.

e. alpha 1.

f. Noradrenaline.

37. If you were being chased by a bear in the woods, would your eyes undergo miosis or mydriasis? Which part of the ANS is elicited?

a. Mydriasis.

b. Sympathetic.

38. What is convergence? How would you compare eye motions during convergence for an object more than 20 feet away? Less than 20 feet away?

a. Convergence is the ability of the eye to focuses light at a focal point. It can also be considered the bending of light rays towards the visual axis.

b. More than 20 feet away:

i. Ciliary muscles are relaxed, suspensory ligaments are taut and the lens is flattened out.

c. Less than 20 feet away:

i. Ciliary muscles are contracted, suspensory ligaments are loose and the lens is bulged (or very convex).

39. If an individual has an eyeball that is longer than normal, which refractive defect would they likely have? Where does the focal point form in this condition? Which type of lenses are used to correct for this refractive defect?

a. Myopia.

b. In front of the retina.

c. Concave, or diverging lenses.

40. If an individual has an eyeball that is shorter than normal, which refractive defect would they likely have? Where does the focal point form in this condition? Which type of lenses are used to correct for this refractive defect?

a. Hyperopia.

b. Behind the retina.

c. Convex, or converging lenses.

41. What is presbyopia? How does the amplitude of accommodation of the lens change over time?

Lens accommodation decreases with age. As a result, the lens cannot bulge as much = essentially farsighted.

42. What is an astigmatism? Cataract? LASIK?

a. Astigmatism is an egg shaped lens

b. Cataract: lens build up pigments and over time vision becomes blurry

c. LASIK: cornea is reshaped with a laser to change the way it bends light rays.

43. An elderly person's vision has gotten increasingly worse over the last decade. They were informed by their ophthalmologist that the elasticity of their lenses has markedly decreased and decades of light bombarding their lenses induced the generation of pigments in them. What visual defect(s) does this person have? Can you explain each of the conditions to better support your answer? Is this person a good candidate for LASIK surgery? Why or why not?

a. Presbyopia and cataracts.

b. Presbyopia is the loss if elasticity of the lens over time and therefore lens accommodation is impaired. Cataracts result from the build up of pigments in the eye.

c. Potentially. Reshaping the cornea could help with the farsightedness due to presbyopia. However, it will not help the cataracts.

44. What is the Snellen chart? What does 20/20 vision literally mean? 20/40? If the Snellen chart reveals that your visual acuity is 20/20, does this mean you have perfect vision?

a. A Snellen chart is an eye chart that can be used to measure visual acuity.

b. 20/20 vision is considered "normal" vision. You can read at 20 feet a letter that most human beings should be able to read at 20 feet.

c. If your visual acuity is 20/40, you are myopic.

d. No, it just means perfect visual acuity.

45. A person's eyeglass prescription is -2.5. What are the units of this prescription? Is this a prescription for negative or positive diopters? Can diopters be converted into Snellen chart numbers?

a. Diopters.

b. Negative.

c. No.

46. What are the three layers of cells of the retina? Which layer of cells process the photons (i.e., are the photoreceptor cells)? What is the macula of the retina? Fovea centralis?

a. Layers of retina:

i. Innermost (closest to the vitreous body) - ganglion cell layer.

ii. Middle - bipolar cell layer.

iii. Rearmost - photoreceptor cell layer (rod and cone cell layer.

b. The macula of the retina is an indentation in the retina off-center from the optic disc.

c. The fovea centralis is a region of the retina in the center of the macula that has the highest concentration of cone photoreceptor cells. The visual axis normally falls on this location.

47. In phototransduction, electromagnetic radiation gets transduced into electrical impulses. Which retinal cells are responsible for firing action potentials? Which cells have axons that comprise the optic nerve?

a. Ganglion cells.

b. Ganglion cells.