11.13 Exercises for Lesson 11

1. Two types of nervous tissues are _____ and  _____ .

What role does the first play in the nervous system?

What role does the second play?

2. Nervous tissues are specialized to:

a.  _____ stimuli.

b.  _____ information.

c.  _____ information.

3. A neuron is a nerve cell body and all of its  _____s.

4. A dendrite carries impulses (toward) (away from) the cell body.

5. What is an axon?

6. Each item below indicates the number of poles for a type of neuron. Give the name which corresponds to each.

a. More than two poles:  _____

b. Two poles:  _____

c. One pole:  _____

7. Each item below refers to the thickness of the myelin surrounding an axon. Give the letter indicating the type of neuron.

a. Thickest:  _____ .

b. Medium:  _____ .

c. Thinnest: . _____

8. Each item below indicates the route over which impulses are transmitted. Give the type of neuron corresponding to each route.

a. From receptor organs to the CNS:  _____ .

b. From the CNS to muscles and glands: _____  .

c. From one neuron to another: _____  .

9. What is meant by the term "continuity without contact" as related to neuron "connections"?

10. What is a synapse?

An axon terminates in tiny branches. What is at the end of each branch? Where is neurotransmitter stored?

What is the presynaptic membrane? What is the synaptic cleft?

What is the postsynaptic membrane?

11. What is a neuromuscular junction?

Compare the neuromuscular junction to a synapse.

12. The major divisions of the human nervous system are the  _____ nervous system ( _____  ), the  _____ nervous system (  _____ ), and the  _____ nervous system ( _____  ). The CNS is made up of the  _____ and the  _____ .

13. The three major subdivisions of the human brain are the  _____ , the  _____ , and the  _____

What is the brainstem?

14. The cerebellum is a spherical mass of nervous tissue attached to and covering the  _____ . Its three major parts are the  _____ and right and left  _____ hemispheres. In addition, the cerebellum has three pairs of stem-like connecting parts called  _____ . The outer cortex is composed of  _____ matter, which is the  _____ s of neurons. More central is the _____ matter, which is the myelinated processes of  _____ . The cerebellum is the primary  _____ / _____  of motor actions of the body.

15. The cerebrum consists of two very much enlarged  _____ s connected to each other by a special structure called the c_____  c_____  . Each cerebral hemisphere is connected to the brainstem by a c_____  p_____  . The surface of each cerebral hemisphere is subdivided into areas known as l_____  . The names of the four lobes are f _____ , p_____  , o_____  , and t_____  .

16. The space separating the two cerebral hemispheres is called the longitudinal  _____ . The shallow grooves in the surface of the cerebrum are called  _____ . The ridges outlined by the grooves are called  _____ .

17. The gray outer layer of each hemisphere is the  _____ . Deeper within the cerebral hemispheres, the tissue is colored  _____ . The "gray matter" represents the  _____  _____s of the neurons. The "white matter" represents the  _____ .

18. Groups of related functions are associated with specific areas of the cerebral cortex. For example, centers of speech and hearing are located along the lateral  _____. Vision is centered in the _____  lobe. Sensory and motor functions are located along the central _____ .

19. The ventricles of the brain are interconnected hollow spaces filled with  _____ . The right and left lateral ventricles are found in the cerebral  _____s. The lateral ventricles are connected to the third ventricle by the i _____  f _____  . The third ventricle is located in the f _____  . The third and fourth ventricles are connected by the c_____  a_____  . The fourth ventricle is located in the h_____  . The fourth ventricle is continuous with the part of the spinal cord known as the c_____  c_____  .

20. The spinal cord, located within the spinal l, is continuous with the b . The spinal cord has two enlargements. One, associated with nerves for the upper members, is called the enlargement. The other, associated with the nerves for the lower members, is called the enlargement. Nerves arising from the spinal cord are called nerves.

There are how many pairs of spinal nerves?

21. In the cross section of the spinal cord, one can see a central region of gray matter shaped like an  _____. Each arm of this figure is called a  _____ . The connecting link is called the gray  _____ . These horns are actually sections of the gray  _____s. Since a column of white matter is a large bundle of processes, it is called a  _____.

22. The skeletal covering for the brain is provided by bones of the  _____ . The overall skeletal structure covering the spinal cord is the  _____ column (spine).

23. The brain and spinal cord have three different membranes surrounding them called  _____ . The tough outer covering for the CNS is the  _____ . Beneath it is the _____ space. The fine second membrane is called the  _____ . Beneath it is the  _____ space, which is filled with  _____ . The delicate membrane applied directly to the surface of the brain and spinal cord is called the  _____ .

24. The two main pairs of arteries supply oxygenated blood to the brain are the  _____ internal and _____  arteries. Beneath the brain, branches of these arteries join to form a circle, called the  _____ circle (of  _____ ). The main pair of veins carrying blood back toward the heart is the internal  _____ veins. The blood supply of the spinal cord is by way of a combination of three l_____  arteries running along its length and reinforced by s_____  arteries from the sides.

25. Found in the cavities of the CNS is a clear fluid called   _____ fluid (  _____  ). This fluid is found in the   _____s of the brain, the sub_____  space, and the spinal cord's  _____  canal. Special collections of arterial capillaries found in the roofs of the third and fourth ventricles are called choroid   _____s. These structures continuously produce CSF from the   _____ of the blood.

26. As CSF is produced by the choroid plexuses, it flows into all four   _____s. CSF from the lateral ventricles flows into the   _____ ventricle, and then through the  _____ aqueduct into the ventricle. By passing through three small holes in the roof of the fourth ventricle, CSF enters the subarachnoid   _____ . From here, the CSF is transported through the arachnoid   _____ into the venous sinuses.

27. The peripheral nervous system is that portion of the nervous system which generally provides commands for   _____ muscles and other   _____ muscles and carries   _____y information from the p _____  of the body. A nerve is a collection of neuron   _____s, together and  _____  the CNS.

28. The 12 pairs of nerves attached to the right and left sides of the brainstem are called   _____ nerves. Each such nerve is identified by a   _____ in order from  _____  to  _____  and an individual name. Attached to the sides of the spinal cord are 31 pairs of   _____ nerves. For each, the region is designated by a  _____  ; within each region, a nerve pair is identified by an  _____  .

29. Like a tree, a typical spinal nerve has   _____s, a  _____  , and branches (called  _____ ). Coming off of the posterior and anterior sides of the spinal cord are the posterior and anterior  _____  of the spinal nerve. An enlargement on the posterior root is the   _____ . A ganglion is a collection of   _____ , together, outside the CNS. Laterally, the posterior and anterior roots of the spinal nerve join to form the spinal nerve   _____ . The spinal nerve trunk of each spinal nerve is located in the corresponding intervertebral   _____ of the vertebral column. As the nerve trunk emerges laterally, it divides into the anterior and posterior   _____ .

30. If it carries information from the periphery to the CNS, it is an   _____t(  _____  ) neuron. If it carries information from the CNS to a muscle or gland, it is an   _____t (   _____ ) neuron.

31. An automatic reaction to a stimulus is referred to as a   _____ .The pathway from the receptor organ to the reacting muscle is called the   _____ .

32. The pathway of a general reflex arc involves a minimum of   _____ structures. The stimulus is received by a   _____ organ. That information is transmitted to the CNS by the   _____t (   _____ ) neuron. Within the spinal cord, there is a special neuron connecting the afferent neuron to the efferent neuron; this special connecting neuron is called the   _____ . Carrying the appropriate command from the spinal cord to the reacting muscle is the   _____t (   _____ ) neuron. The reacting muscle is called the e _____  organ.

33. The autonomic nervous system is that portion of the nervous system generally concerned with commands for s _____  muscle, c _____  muscles, and   _____s.

34. In the ANS, the number of neurons connecting the CNS with a visceral organ is always   _____ . The cell bodies of the second neuron form a collection outside the CNS, called a   _____ . The first neuron extends from the CNS to the ganglion and is therefore called the  _____  neuron. Cell bodies of the second neurons make up the   _____ . The second neuron's processes extend from the ganglion to the  _____  . Thus, the second neuron is called the  _____ neuron.

35. The efferent pathways of the ANS fall into two major divisions. The one most active during a "fight-or-flight" reaction is the   _____- _____  outflow (  _____ nervous system). The other is the   _____- _____ outflow (   _____ nervous system).

36. The intermediolateral gray columns from the T-1 to the L-2 levels of the spinal cord are made up of the cell bodies of the   _____-ganglionic sympathetic neurons. The sympathetic ganglia are made up of the cell bodies of the   _____-ganglionic sympathetic neurons. The sympathetic NS activates those visceral organs needed to  _____.  It deactivates those which are   _____ .

37. Four pairs of nuclei in the brainstem and the intermediolateral gray columns at the S-2 through S-4 levels of the spinal cord are made up of the cell bodies of the p _____  p _____  neurons. The intramural ganglia within the walls of the   _____ organs are made up of the cell bodies of the p _____  p _____  neurons. As compared to that of the sympathetic NS, the parasympathetic NS has the (same) (opposite) effect on visceral organs.

38. What is a pathway?

39. What is the neuraxis?.

40. What is a sensory pathway?.

41. What is a motor pathway?.

42. The human nervous system has several levels of control. The lowest level is the   _____ . The highest level is the   _____ level. Between, there are several progressively  _____  levels. All information input and all information output are   _____d and   _____d.

43. The right half of the brain controls the   _____ side of the body. The left half of the brain controls the   _____ side of the body.

44. A pyramidal pathway is primarily concerned with   _____ (   _____ ) control of body parts, particularly the   _____ movements of   _____s. These pathways are called pyramidal because their neuron processes help to make up structures in the base of the brain called  _____  .

45. An extrapyramidal pathway is primarily concerned with  _____  (   _____ ) control of body parts for purposes of   _____ .

46. Name examples of general senses.

a.  _____ . b.  _____ . c.  _____ . d.  _____ .

47. Name examples of special senses.

a.  _____ . b.  _____ . c.  _____ . d.  _____ . e. _____.

48. The general sensory pathway is from the   _____ organ, via the  _____  nerves, to the   _____ . This general pathway then ascends fiber tracts in the  _____  . The pathway ends in the central area of the opposite  _____  hemisphere.

49. The receptors for the sense of smell are special hair cells called c_____s. These are found in the o _____  e  _____ , high in the n_____  c _____ s in the head. The information received is transmitted by way of the o _____  nerves to the  _____ y bulbs and then into the opposite   _____l hemisphere.

50. Describe the sensory receptors for the special sense of taste.

The information received is transmitted to the opposite side of the brain by three   _____ nerves.

51. What is the eyeball?

The eyeball is shaped like a   _____ .

52. The outermost layer of the eyeball is colored   _____ and is made up of very dense  _____  ; it is known as the   _____ . Its anterior portion is called the   _____ . The major focusing device for the eyeball is the   _____ .

53. The middle layer of the wall of the eyeball is known as the  _____  . This layer is richly supplied with   _____ and pigmented with a   _____ material.

54. The inner layer of the wall of the eyeball is known as the  _____  . The actual photoreceptor elements are located at the  _____  and the  _____ s. These elements are the   _____s and the   _____s.

55. The elements which register colors are the   _____ . However,  _____  require more intense light than do  _____  . Rods register only   _____ .

56. What are the fovea centralis and macula lutea?

57. What is the blind spot?

58. The thickening of the choroid layer around the edge of the lens is called the  _____. It includes radial muscle fibers making up the   _____ muscle.

59. Describe the lens and the process of accommodation.

60. The space between the cornea and the iris is called the  _____   _____  . The space between the iris and the lens is called the   _____ . Together, these make up the space between the cornea and the lens, called the   _____ and filled with the  _____  . This drains into the encircling  _____ , located in the angle between the  _____  and the  _____  . Behind the lens is a jellylike material called the   _____ . It fills the   _____ cavity of the eyeball.

61. The orbit is the cavity in the upper facial skull which contains the   _____ and its  _____ . The orbit is shaped roughly like a  _____ .

62. Examples of the adnexa are the:

a.  _____ . b.  _____ . c.  _____ . d.  _____ . e. _____.

63. Of the six extrinsic ocular muscles, four are called   _____ muscles. Two are  _____ muscles. The lateral rectus M. is on the   _____ side of the eyeball. The superior rectus M. is   _____ the eyeball. The medial rectus M. is on the   _____ side of the eyeball. The inferior rectus M. is the   _____ eyeball. The superior oblique and inferior oblique muscles approach the eyeball from the   _____ side.

64. Attached to the margins of the orbit are the upper and lower  _____  . These have special hairs called   _____ . The inner lining of the eyelids is continuous with the   _____ , a membrane over the anterior surface of the eyeball.

65. In the upper outer corner of the orbit is a lacrimal   _____d, which secretes a lacrimal   _____d, which is ultimately collected and delivered into the nasal chamber by the   _____ duct.

66. Neurons carry information from the photoreceptors located in the nervous  _____ . They leave the eyeball at the  _____  . Passing to the rear of the orbit, the neurons now belong to the   _____ nerve (cranial nerve ). The optic nerve enters the cranial cavity by passing through the   _____ canal. Beneath the brain, the optic nerves from both sides join to form the   _____ , in which half of the neurons from each optic nerve   _____ . From the optic chiasma, the right and left optic   _____s proceed to the brain proper.

67. The human ear has two major special sensory functions:   _____ (   _____y) and (   _____e). The three parts of the human ear are the   _____ (  _____  ) ear, the   _____ ear, and the   _____ (  _____  ) ear.

68. The external flap of the ear is called the   _____ (   _____ ). It directs airborne sound waves into the canal called the external auditory   _____ , which extends into the   _____ portion of the skull.

69. Where is the tympanic membrane?

On the medial side of the tympanic membrane, there is a space within the temporal bone called the   _____ .

What are the auditory ossicles?

The auditory ossicles respond to a sound stimulus by  _____ . From the lateral to the medial ends, the names of the ossicles are:   _____ ,  _____ , and   _____ . The auditory tube connects the middle ear cavity with the  _____

70. What is the bony labyrinth?

It has three   _____ canals, a  _____  (hallway), and a snail-shaped   _____ portion.

What is the membranous labyrinth?

71. Where is the endolymph found?

Where is the perilymph found?

72. The cochlea is a   _____ structure associated with   _____ing. It has   _____ turns. Its outer boundaries are formed by the snail-shaped portion of the   _____ .

73. The central column of the cochlea is called the m _____  . Extending from this central column is a spiral shelf of bone called the s _____  l  _____  . Connecting this shelf with the outer bony wall is a fibrous membrane called the b _____  membrane. This membrane forms the floor of the spiral portion of the membranous labyrinth called the c _____  d _____  . This contains a structure with hairs, sensory receptors of hearing; this structure is called the organ of  _____ .

74. Within the bony cochlea, the space above the cochlear duct is known as the  _____   _____ and the space below is known as the   _____ . Between the middle ear cavity and the upper space is an oval window called the fenestra . Between the middle ear cavity and the lower space is a round window called the fenestra   _____ .

75. A sound stimulus is transferred from the stapes to the fluid   _____ of the  _____. In response, the b _____  membrane of the cochlea vibrates. The hair cells of the   _____ of  _____  are mechanically stimulated. This stimulation is transferred to the neurons of the   _____ nerve, which passes out of the modiolus into the internal auditory   _____ of the temporal bone. From here, the nerve enters the
  _____ cavity and goes to the   _____ .

76. The two sac-like portions of the membranous labyrinth are the   _____ and the   _____ . They are filled with  _____  . On the wall of each sac is a collection of special hair cells known as the   _____ , which serves as a receptor organ for  _____ and linear   _____ gravitational forces. The saccular macula and the utricular macula are oriented at more or less  _____ ° angles to each other.

77. Extending from and opening into the utriculus are three hollow structures called the   _____ ducts. The utriculus completes the circle for each   _____ . The three ducts are all oriented at   _____ ° angles to each other. Where it opens into the utriculus, each semicircular duct ends in an enlargement called an  _____  . Movement of the fluid endolymph bends the hairs of the   _____ in specific directions. These are responses to   _____ and/or   _____ kinetic gravitational forces.

78. Carrying the information from the maculae and the cristae to the brain is the  _____ nerve. Contained in the same fibrous sheath from the membranous labyrinth to the brain are the v _____  and a _____  nerves.

79. The simplest and lowest level of control is the  _____   _____ . Producing wider reactions to stimuli are s_____  reflexes. A number of nuclei in the hindbrain monitor and control v_____l functions of the body, including r _____  and h _____b _____ . The facilitatory and inhibitory areas of the reticular formation monitor and control general body functions, including  _____ . The thalamus is a primary relay for information going to and from the  _____ and  _____  . One of the most important integrators of motor activity of the body is the  _____  .

80. In humans, the highest level of control is in the   _____ . Here, we can clearly designate three levels of control:

a. The first level is concerned with   _____ activities of the body, as related to   _____ , fear, and other emotions.

b. At the second level, activities of the body are s_____d and repetitive in nature. An example is the sequence of muscle actions involved in w _____ing.

c. At the third level, brand new solutions can be created. This is the v _____  level.

Answers to Exercises for Lesson 11

1. Two types of nervous tissues are neurons (nerve cells) and glia (neuroglia). The neuron is the basic structural unit of the nervous system. The glia are cells of supporting tissue for the nervous system.

2. Nervous tissues are specialized to:

a. Receive stimuli.

b. Transmit information.

c.. Store information.

3. A neuron is a nerve cell body and all of its processes.

4. A dendrite carries impulses toward the cell body.

5. An axon is a neuron process which transmits information from the cell body to the next unit.

6. More than two poles: multipolar neuron.

 Two poles: bipolar neuron.

One pole: unipolar neuron.

7. Thickest: A.

Medium: B.

Thinnest: C.

8. From receptor organs to the CNS: sensory neurons.

From the CNS to muscles and glands: motor neurons.

From one neuron to another: interneurons.

9. The term "continuity without contact" refers to the fact that neurons do not actually touch. Thus, there is no electrical transmission of impulses from one neuron to the next. In fact, information is transferred across the synaptic cleft by chemicals called neurotransmitters

10. A synapse is a "connection" between two neurons. An axon terminates in tiny branches. At the end of each branch is a terminal bulb. Neurotransmitters are stored in bundles called synaptic vesicles located within each terminal bulb. The presynaptic membrane is the thickened layer of the terminal bulb which faces the synaptic cleft and through which pass the neurotransmitters before entering the synaptic cleft. The synaptic cleft is the space between the terminal bulb of the first neuron and the dendrite or cell body of the second neuron. The postsynaptic membrane is that portion of the membrane of the second neuron which lies near the terminal bulb of the first neuron.

11. A neuromuscular junction is a "connection" between the terminal of a motor neuron and a muscular fiber. Comparison: The neuromuscular junction has an organization identical to a synapse. However, the bulb is larger and protrudes into the surface of the muscle fiber. The postsynaptic membrane is also larger and has foldings.

12. The major divisions of the human nervous system are the central nervous system (CNS), the peripheral nervous system (PNS), and the autonomic nervous system (ANS). The CNS is made up of the brain and the spinal cord.

13. The three major subdivisions of the human brain are the brainstem, the cerebellum, and the cerebrum. The brainstem is that part of the brain remaining after removal of the cerebrum and cerebellum. It is the basal portion. Together with the spinal cord, it is known as the neuraxis.

14. The cerebellum is a spherical mass of nervous tissue attached to and covering the hindbrainstem. Its three major parts are the vermis and right and left cerebellar hemispheres. In addition, the cerebellum has three pairs of stem-like connecting parts called peduncles. The outer cortex is composed of gray matter, which is the cell bodies of neurons. More central is the white matter, which is the myelinated processes of neurons. The cerebellum is the primary coordinator/ integrator of motor actions of the body.

15. The cerebrum consists of two very much enlarged hemispheres connected to each other by a special structure called the corpus callosum. Each cerebral hemisphere is connected to the brainstem by a cerebral peduncle. The surface of each cerebral hemisphere is subdivided into areas known as lobes. The names of the four lobes are frontal, parietal, occipital, and temporal.

16. The space separating the two cerebral hemispheres is called the longitudinal fissure. The shallow grooves in the surface of the cerebrum are called sulci. The ridges outlined by the sulci are called gyri.

17. The gray outer layer of each hemisphere is the cerebral cortex. Deeper within the cerebral hemispheres, the tissue is colored white. The "gray matter" represents the cell bodies of the neurons. The "white matter" represents the axons.

18. Groups of related functions are associated with specific areas of the cerebral cortex. For example, centers of speech and hearing are located along the lateral sulcus. Vision is centered in the occipital lobe. Sensory and motor functions are located along the central sulcus.

19. The ventricles of the brain are interconnected hollow spaces filled with CSF. The right and left lateral ventricles are found in the cerebral hemispheres. The lateral ventricles are connected to the third ventricle by the interventricular foramen. The third ventricle is located in the forebrainstem. The third and fourth ventricles are connected by the cerebral aqueduct. The fourth ventricle is located in the hindbrainstem. The fourth ventricle is continuous with the part of the spinal cord known as the central canal.

20. The spinal cord, located within the spinal canal, is continuous with the brainstem. The spinal cord has two enlargements. One, associated with nerves for the upper members, is called the cervical enlargement. The other, associated with nerves for the lower members, is called the lumbosacral enlargement. Nerves arising from the spinal cord are called spinal nerves. There are 31 pairs of spinal nerves.

21. In the cross section of the spinal cord, one can see a central region of gray matter shaped like an H. Each arm of this figure is called a horn. The connecting link is called the gray commissure. These horns are actually sections of the gray columns. Since a column of white matter is a large bundle of processes, it is called a funiculus.

22. The skeletal covering for the brain is provided by bones of the cranium. The overall skeletal structure covering the spinal cord is the vertebral column (spine).

23. The brain and spinal cord have three different membranes surrounding them called meninges. The tough outer covering for the CNS is the dura mater. Beneath it is the subdural space. The fine second membrane is called the arachnoid mater. Beneath it is the subarachnoid space, which is filled with CSF. The delicate membrane applied directly to the surface of the brain and spinal cord is called the pia mater.

24. The two main pairs of arteries supplying oxygenated blood to the brain are the internal carotid and the vertebral arteries. Beneath the brain, branches of these arteries join to form a circle, called the cerebral circle (of Willis). The main pair of veins carrying blood back toward the heart is the internal jugular veins. The blood supply of the spinal cord is by way of a combination of three longitudinal arteries running along its length and reinforced by segmental arteries from the sides.

25. Found in the cavities of the CNS is a clear fluid called cerebrospinal fluid (CSF). This fluid is found in the ventricles of the brain, the subarachnoid space, and the spinal cord's central canal. Special collections of arterial capillaries found in the roofs of the third and fourth ventricles are called choroid plexuses. These structures continuously produce CSF from the plasma of the blood.

26. As CSF is produced by the choroid plexuses, it flows into all four ventricles. CSF from the lateral ventricles flows into the third ventricle and then through the cerebral aqueduct into the fourth ventricle. By passing through three small holes in the roof of the fourth ventricle, CSF enters the subarachnoid space. From here, the CSF is transported through the arachnoid villi into the venous sinuses.

27. The peripheral nervous system is that portion of the nervous system which generally provides commands for skeletal muscles and other striated muscles and carries sensory information from the periphery of the body. A nerve is a collection of neuron processes, together and outside the CNS.

28. The 12 pairs of nerves attached to the right and left sides of the brainstem are called cranial nerves. Each such nerve is identified by a Roman numeral in order from I to XII and an individual name. Attached to the sides of the spinal cord are 31 pairs of spinal nerves. For each, the region is designated by a letter; within each region, a nerve pair is identified by an Arabic numeral.

29. Like a tree, a typical spinal nerve has roots, a trunk, and branches (called rami). Coming off of the posterior and anterior sides of the spinal cord are the posterior and anterior roots of the spinal nerve. An enlargement on the posterior root is the posterior root ganglion. A ganglion is a collection of neuron cell bodies, together, outside the CNS. Laterally, the posterior and anterior roots of the spinal nerve join to form the spinal nerve trunk. The spinal nerve trunk of each spinal nerve is located in the corresponding intervertebral foramen of the vertebral column. As the nerve trunk emerges laterally, it divides into the anterior and posterior rami.

30. If it carries information from the periphery to the CNS, it is an afferent (sensory) neuron. If it carries information from the CNS to a muscle or gland, it is an efferent (motor) neuron.

31. An automatic reaction to a stimulus is referred to as a reflex. The pathway from the receptor organ to the reacting muscle is called the reflex arc.

32. The pathway of a general reflex arc involves a minimum of five structures. The stimulus is received by a receptor organ. The information is transmitted to the CNS by the afferent (sensory) neuron. Within the spinal cord, there is a special neuron connecting the afferent neuron to the efferent neuron; this special connecting neuron is called the interneuron (or internuncial neuron). Carrying the appropriate command from the spinal cord to the reacting muscle is efferent (motor) neuron. The reacting muscle is called the effector organ.

33. The autonomic nervous system is that portion of the nervous system generally concerned with commands for smooth muscle, cardiac muscle, and glands.

34. In the ANS, the number of neurons connecting the CNS with a visceral organ is always two. The cell bodies of the second neurons form a collection outside the CNS, called a ganglion. The first neuron extends from the CNS to the ganglion and is therefore called the preganglionic neuron. Cell bodies of the second neurons make up the ganglion. The second neuron's processes extend from the ganglion to the visceral organ. Thus, the second neuron is called the post- ganglionic neuron. (para 11-16b)

35. The efferent pathways of the ANS fall into two major divisions. The one most active during a "fight-or-flight" reaction is the thoracolumbar outflow (sympathetic nervous system). The other is the craniosacral outflow (parasympathetic nervous system.

36. The intermediolateral gray columns from the T-1 to the L-2 levels of the spinal cord are made up of the cell bodies of the preganglionic sympathetic neurons. The sympathetic ganglia are made up of the post- ganglionic sympathetic neurons. The sympathetic NS activates those visceral organs needed to mobilize energy for action. It deactivates those which are not needed.

37. Four pairs of nuclei in the brainstem and the intermediolateral gray columns at the S-2 through S-4 levels of the spinal cord are made up of the cell bodies of the preganglionic parasympathetic neurons. The intramural ganglia within the walls of the central visceral organs are made up of the cell bodies of the post-ganglionic parasympathetic neurons. As compared to that of the sympathetic NS, the parasympathetic NS has the opposite effect on visceral organs.

38. A pathway is the series of nervous structures utilized in the transmission of an item of information.

39. The neuraxis is the brainstem and the spinal cord, considered together as one structure.

40. A sensory pathway is a series of nervous structures used to transmit information from the body to the CNS.

41. A motor pathway is a series of nervous structures used to transmit information from the CNS to the body.

42. The human nervous system has several levels of control. The lowest level is the simple reflex arc. The highest level is the conscious level. Between, there are several progressively higher levels. All information input and all information output are monitored and evaluated. The right half of the brain controls the left side of the body. The left half of the brain controls the right side of the body.

44. A pyramidal motor pathway is primarily concerned with volitional (voluntary) control of body parts, particularly the fine movements of hands. These pathways are called pyramidal because their neuron processes help to make up structures in the base of the brain called pyramids.

45. An extrapyramidal pathway is primarily concerned with automatic (nonvolitional) control of body parts for purposes of coordination.

46. Examples of general senses are:

a. Pain.
b. Temperature (warm and cold).
c. Touch (light and deep).
d. Proprioception ("body sense").

47. Examples of special senses are:

a. Smell (olfaction).
b. Taste (gustation).
c. Vision.
d. Hearing (auditory).
e. Equilibrium.

48. The general sensory pathway is from the receptor organ, via the PNS nerves, to the CNS. This general pathway then ascends fiber tracts in the neuraxis. The pathway ends in the central area of the opposite cerebral hemisphere.
(para 11-21e)

49. The receptors for the sense of smell are special hair cells called chemoreceptors. These are found in the olfactory epithelium, high in the nasal chambers in the head. The information received is transmitted by way of the olfactory nerves to the olfactory bulbs and then into the opposite cerebral hemisphere.

50. Special hair cells (chemoreceptors) are found in the taste buds, scattered over the tongue and the rear of the mouth. These cells, which react to dispersed or dissolved food molecules, are the sensory receptors for the special sense of taste. The information received is transmitted to the opposite side of the brain by three cranial nerves.

51. The eyeball is the sense organ containing the receptor tissues for the special sense of vision. The eyeball is shaped like a bulb (or sphere).

52. The outermost layer of the eyeball is colored white and is made up of very dense FCT; it is known as the sclera, scleral coat, or fibrous tunic. Its anterior portion is called the cornea. The major focusing device for the eyeball is the cornea.

53. The middle layer of the wall of the eyeball is known as the choroid, choroid coat, or vascular tunic. This layer is richly supplied with blood vessels and pigmented with a black material.

54. The inner layer of the wall of the eyeball is known as the retina, retinal coat, or internal tunic. The actual photoreceptor elements are located at the back and the sides. These elements are the rods and the cones.

55. The elements which register colors are the cones. However, cones require more intense light than do rods. Rods register only black and white.

56. The fovea centralis is a small depression at the posterior end of the eyeball opposite the pupil. The macula lutea is a small yellow area of the retina where vision is sharpest. It includes the fovea centralis.

57. The blind spot is the point of exit of the optic nerve, at the posterior end of the eyeball where there are no rods and cones.

58. The thickening of the choroid layer around the edge of the lens is called the ciliary body. It includes radial muscle fibers making up the ciliary muscle.

59. The lens is biconvex. The anterior surface is flatter than the posterior surface. The lens is transparent and elastic. Its thickness varies with contraction or relaxation of the ciliary muscle. Accommodation is the process in which close objects are seen more clearly; it involves contraction of the ciliary muscle, reduction in pupil size, and convergence of the lines of sight.

60. The space between the cornea and the iris is called the anterior chamber. The space between the iris and the lens is called the posterior chamber. Together, these make up the space between the cornea and the lens called the anterior cavity and filled with the aqueous humor. This drains into the encircling canal of Schlemm, located in the angle between the cornea and the iris. Behind the lens is a jellylike material called the vitreous body. It fills the posterior cavity of the eyeball.

61. The orbit is the cavity in the upper facial skull which contains the eyeball and its adnexa. The orbit is shaped roughly like a cone.

62. Examples of the adnexa are the:

a. Extrinsic ocular muscles.
b. Eyelids.
c. Lacrimal apparatus.
d. Eyebrow.
e. Optic nerve.

63. Of the six extrinsic ocular muscles, four are called recti muscles. Two are oblique muscles. The lateral rectus M. is on the outer side of the eyeball. The superior rectus M. is above the eyeball. The medial rectus M. is on the inner side of the eyeball. The inferior rectus M. is below the eyeball. The superior oblique and inferior oblique muscles approach the eyeball from the medial side.

64. Attached to the margins of the orbit are the upper and lower eyelids. These have special hairs called eyelashes. The inner lining of the eyelids is continuous with the conjunctiva, a membrane over the anterior surface of the eyeball.

65. In the upper outer corner of the orbit is a lacrimal gland, which secretes a lacrimal fluid, which is ultimately collected and delivered into the nasal chamber by the nasolacrimal duct.

66. Neurons carry information from the photoreceptors located in the nervous retina. They leave the eyeball at the blind spot. Passing to the rear of the orbit, the neurons now belong to the optic nerve (cranial nerve II). The optic nerve enters the cranial cavity by passing through the optic canal. Beneath the brain, the optic nerves from both sides join to form the optic chiasma, in which half of the neurons from each optic nerve cross to the opposite side. From the optic chiasma, the right and left optic tracts proceed to the brain proper.

67. The human ear has two major special sensory functions: hearing (auditory) and equilibrium (balance). The three parts of the human ear are the external (outer) ear, the middle ear, and the internal (inner) ear.

68. The external flap of the ear is called the auricle (pinna). It directs airborne sound waves into the canal called the external auditory meatus, which extends into the temporal portion of the skull.

69. The tympanic membrane is between the external auditory meatus and the middle ear cavity. On the medial side of the tympanic membrane, there is a space within the temporal bone called the middle ear cavity. The auditory ossicles are three very small bones linking the tympanic membrane to the medial wall of the middle ear cavity. The auditory ossicles respond to a sound stimulus by vibrating (mechanically oscillating). From the lateral to the medial ends, the names of the ossicles are: malleus, incus, and stapes. The auditory tube connects the middle ear cavity with the nasopharynx.

70. The bony labyrinth is a complex cavity within the temporal bone. It has three semi-circular canals, a vestibule (hallway), and a snail- shaped cochlear portion. The membranous labyrinth is a hollow tubular structure suspended within the bony labyrinth.

71. The endolymph fills the space within the membranous labyrinth. The perilymph fills the space between the membranous labyrinth and the bony labyrinth.

72. The cochlea is a spiral structure associated with hearing. It has 2-1/2 turns. Its outer boundaries are formed by the snail-shaped portion of the bony labyrinth.

73. The central column of the cochlea is called the modiolus. Extending from this central column is a spiral shelf of bone called the spiral lamina. Connecting this shelf with the outer bony wall is a fibrous membrane called the basilar membrane. This membrane forms the floor of the spiral portion of the membranous labyrinth called the cochlear duct. This contains a structure with hairs, sensory receptors of hearing; this structure is called the organ of Corti.

74. Within the bony cochlea, the space above the cochlear duct is known as the scala vestibuli and the space below is known as the scala tympani. Between the middle ear cavity and the upper space is an oval window called the fenestra vestibuli. Between the middle ear cavity and the lower space is a round window called the fenestra cochleae.

75. A sound stimulus is transferred from the stapes to the fluid perilymph of the scala vestibuli. In response, the basilar membrane of the cochlea vibrates. The hair cells of the organ of Corti are mechanically stimulated. This stimulation is transferred to the neurons of the acoustic nerve, which passes out of the modiolus into the internal auditory meatus of the temporal bone. From here, the nerve enters the cranial cavity and goes to the brain.

76. The two sac-like portions of the membranous labyrinth are the sacculus and the utriculus. They are filled with endolymph. On the wall of each sac is a collection of special hair cells known as the macula, which serves as a receptor organ for static and linear kinetic gravitational forces. The saccular macula and the utricular macula are oriented at more or less 90° angles to each other.

77. Extending from and opening into the utriculus are three hollow structures called the semicircular ducts. The utriculus completes the circles for each duct. The three ducts are all oriented at 90° angles to each other. Where it opens into the utriculus, each semicircular duct ends in an enlargement called an ampulla.

Movement of the fluid endolymph bends the hairs of the crista in specific directions. These are responses to linear and/or angular kinetic gravitational forces.

78. Carrying the information from the maculae and the cristae to the brain is the vestibular nerve. Contained in the same fibrous sheath from the membranous labyrinth to the brain are the vestibular and auditory nerves.

79. The simplest and lowest level of control is the reflex arc. Producing wider reactions to stimuli are segmental reflexes. A number of nuclei in the hindbrain monitor and control visceral functions of the body, including respiration and heartbeat. The facilitatory and inhibitory areas of the reticular formation monitor and control general body functions, including sleep. The thalamus is a primary relay for information going to and from the cerebrum and cerebellum. One of the most important integrators of motor activity of the body is the cerebellum.

80. In humans, the highest level of control is in the cerebrum. Here, we can clearly designate three levels of control.

a. The first level is concerned with visceral activities of the body, as related to fight-or-flight, fear, and other emotions.

b. At the second level, activities of the body are standardized and repetitive in nature. An example is the sequence of muscle actions involved in walking.

c. At the third level, brand new solutions can be created. This is the volitional level.