1. The Nervous System

2. What is a reflex? What is a reflex?
What is meant by the statement that a reflex can be monosynaptic, disynaptic, polysnaptic?
Let’s take a look at a monosynaptic reflex called a “knee-jerk” reflex.
Proprioception: The awareness of your body’s position in space.
How do we sense this? (muscle spindles)
Need a volunteer!!
So this is like a correctional system for our body.

3. What would this reflex look like?
Look at the connection from the SN to the MN
Of course if you contract both the biceps and the triceps at the same time you won’t get any movement. Right?
Look at the connection from the SN to IN to the MN. This synapse is inhibitory – turns off the triceps

4. Time to move!
How come when the doctor taps your patellar tendon you kick in response?
Work with a partner to demonstrate the patellar tendon “knee-jerk” reflex.
Draw out the neural pathway and identify the muscle groups used.

5. The Reflex Arc
Reflex—rapid, predictable, and involuntary response to a stimulus
Occurs over pathways called reflex arcs
Reflex arc—direct route from a sensory neuron, to an interneuron, to a motor neuron of an effector

6. The Reflex Arc Figure 7.11a Stimulus at distal end of neuron Skin
Spinal cord
(in cross section)
Interneuron
Receptor
Effector
Sensory neuron
Motor neuron
Integration center
(a)
Figure 7.11a

7. The Reflex Arc Figure 7.11a, step 1 Skin
Stimulus at distal end of neuron
Skin
Receptor
(a)
Figure 7.11a, step 1

8. The Reflex Arc Figure 7.11a, step 2 Skin
Stimulus at distal end of neuron
Skin
Receptor
Sensory neuron
(a)
Figure 7.11a, step 2

9. The Reflex Arc Figure 7.11a, step 3 Skin Spinal cord
Stimulus at distal end of neuron
Skin
Spinal cord
(in cross section)
Interneuron
Receptor
Sensory neuron
Integration center
(a)
Figure 7.11a, step 3

10. The Reflex Arc Figure 7.11a, step 4 Skin Spinal cord
Stimulus at distal end of neuron
Skin
Spinal cord
(in cross section)
Interneuron
Receptor
Sensory neuron
Motor neuron
Integration center
(a)
Figure 7.11a, step 4

11. The Reflex Arc Figure 7.11a, step 5 Stimulus at distal end of neuron
Skin
Spinal cord
(in cross section)
Interneuron
Receptor
Effector
Sensory neuron
Motor neuron
Integration center
(a)
Figure 7.11a, step 5

12. Simple Reflex Arc Figure 7.11b–c
Sensory receptors (stretch receptors in the quadriceps muscle)
Sensory (afferent) neuron
Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
Synapse in ventral horn gray matter
Inter- neuron
Motor (efferent) neuron
Motor (efferent) neuron
Effector (quadriceps muscle of thigh)
Effector (biceps brachii muscle)
(b)
(c)
Figure 7.11b–c

13. Simple Reflex Arc Figure 7.11b, step 1
Sensory receptors (stretch receptors in the quadriceps muscle)
Spinal cord
(b)
Figure 7.11b, step 1

14. Simple Reflex Arc Figure 7.11b, step 2
Sensory receptors (stretch receptors in the quadriceps muscle)
Sensory (afferent) neuron
Spinal cord
(b)
Figure 7.11b, step 2

15. Simple Reflex Arc Figure 7.11b, step 3
Sensory receptors (stretch receptors in the quadriceps muscle)
Sensory (afferent) neuron
Spinal cord
Synapse in ventral horn gray matter
(b)
Figure 7.11b, step 3

16. Simple Reflex Arc Figure 7.11b, step 4
Sensory receptors (stretch receptors in the quadriceps muscle)
Sensory (afferent) neuron
Spinal cord
Synapse in ventral horn gray matter
Motor (efferent) neuron
(b)
Figure 7.11b, step 4

17. Simple Reflex Arc Figure 7.11b, step 5
Sensory receptors (stretch receptors in the quadriceps muscle)
Sensory (afferent) neuron
Spinal cord
Synapse in ventral horn gray matter
Motor (efferent) neuron
Effector (quadriceps muscle of thigh)
(b)
Figure 7.11b, step 5

18. Simple Reflex Arc Figure 7.11c, step 1
Sensory receptors (pain receptors in the skin)
Spinal cord
(c)
Figure 7.11c, step 1

19. Simple Reflex Arc Figure 7.11c, step 2
Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
(c)
Figure 7.11c, step 2

20. Simple Reflex Arc Figure 7.11c, step 3
Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
Inter- neuron
(c)
Figure 7.11c, step 3

21. Simple Reflex Arc Figure 7.11c, step 4a
Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
Inter- neuron
Motor (efferent) neuron
(c)
Figure 7.11c, step 4a

22. Simple Reflex Arc Figure 7.11c, step 4b
Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
Inter- neuron
Motor (efferent) neuron
Effector (biceps brachii muscle)
(c)
Figure 7.11c, step 4b

23. Simple Reflex Arc Figure 7.11b–c
Sensory receptors (stretch receptors in the quadriceps muscle)
Sensory (afferent) neuron
Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
Synapse in ventral horn gray matter
Inter- neuron
Motor (efferent) neuron
Motor (efferent) neuron
Effector (quadriceps muscle of thigh)
Effector (biceps brachii muscle)
(b)
(c)
Figure 7.11b–c

24. Types of Reflexes and Regulation
Somatic reflexes
Activation of skeletal muscles
Example: When you move your hand away from a hot stove

25. Types of Reflexes and Regulation
Autonomic reflexes
Smooth muscle regulation
Heart and blood pressure regulation
Regulation of glands
Digestive system regulation

26. Types of Reflexes and Regulation
Patellar, or knee-jerk, reflex is an example of a two-neuron reflex arc
Figure 7.11d

27. Central Nervous System (CNS)
CNS develops from the embryonic neural tube
The neural tube becomes the brain and spinal cord
The opening of the neural tube becomes the ventricles
Four chambers within the brain
Filled with cerebrospinal fluid

31. Central Nervous System (CNS)
Figure 7.12a

32. Regions of the Brain Cerebral hemispheres (cerebrum) Diencephalon
Brain stem
Cerebellum

33. Regions of the Brain: Cerebrum
Figure 7.12b

34. Regions of the Brain: Cerebrum
Cerebral Hemispheres (Cerebrum)
Paired (left and right) superior parts of the brain
Includes more than half of the brain mass
The surface is made of ridges (gyri) and grooves (sulci)

35. Regions of the Brain: Cerebrum
Figure 7.13a

36. Regions of the Brain: Cerebrum
Lobes of the cerebrum
Fissures (deep grooves) divide the cerebrum into lobes
Surface lobes of the cerebrum
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe

37. Regions of the Brain: Cerebrum
Figure 7.13b

38. Regions of the Brain: Cerebrum
Specialized areas of the cerebrum
Primary somatic sensory area
Receives impulses from the body’s sensory receptors
Located in parietal lobe
Primary motor area
Sends impulses to skeletal muscles
Located in frontal lobe
Broca’s area
Involved in our ability to speak

39. Regions of the Brain: Cerebrum
Figure 7.13c

40. Regions of the Brain: Cerebrum
Figure 7.14

41. Regions of the Brain: Cerebrum
Cerebral areas involved in special senses
Gustatory area (taste)
Visual area
Auditory area
Olfactory area

42. Regions of the Brain: Cerebrum
Interpretation areas of the cerebrum
Speech/language region
Language comprehension region
General interpretation area

43. Regions of the Brain: Cerebrum
Figure 7.13c

44. Regions of the Brain: Cerebrum
Layers of the cerebrum
Gray matter—outer layer in the cerebral cortex composed mostly of neuron cell bodies
White matter—fiber tracts deep to the gray matter
Corpus callosum connects hemispheres
Basal nuclei—islands of gray matter buried within the white matter

45. Regions of the Brain: Cerebrum
Figure 7.15

46. Regions of the Brain: Diencephalon
Figure 7.16

47. Regions of the Brain: Diencephalon
Sits on top of the brain stem
Enclosed by the cerebral hemispheres
Made of three parts
Thalamus
Hypothalamus
Epithalamus

48. Regions of the Brain: Diencephalon
Figure 7.12b

49. Regions of the Brain: Diencephalon
Figure 7.16a

50. Regions of the Brain: Diencephalon
Figure 7.16b

51. Regions of the Brain: Diencephalon
Thalamus
Surrounds the third ventricle
The relay station for sensory impulses
Transfers impulses to the correct part of the cortex for localization and interpretation

52. Regions of the Brain: Diencephalon
Hypothalamus
Under the thalamus
Important autonomic nervous system center
Helps regulate body temperature
Controls water balance
Regulates metabolism

53. Regions of the Brain: Diencephalon
Hypothalamus (continued)
An important part of the limbic system (emotions)
The pituitary gland is attached to the hypothalamus

54. Regions of the Brain: Diencephalon
Epithalamus
Forms the roof of the third ventricle
Houses the pineal body (an endocrine gland)
Includes the choroid plexus—forms cerebrospinal fluid

55. Regions of the Brain: Brain Stem
Attaches to the spinal cord
Parts of the brain stem
Midbrain
Pons
Medulla oblongata

56. Regions of the Brain: Brain Stem
Figure 7.16a

57. Regions of the Brain: Brain Stem
Midbrain
Mostly composed of tracts of nerve fibers
Has two bulging fiber tracts— cerebral peduncles
Has four rounded protrusions— corpora quadrigemina
Reflex centers for vision and hearing
(for generating reflexive responses to help the organism avoid tissue damage.)

58. Regions of the Brain: Brain Stem
Pons
The bulging center part of the brain stem
Mostly composed of fiber tracts
Includes nuclei involved in the control of breathing

59. Regions of the Brain: Brain Stem
Medulla Oblongata
The lowest part of the brain stem
Merges into the spinal cord
Includes important fiber tracts
Contains important control centers
Heart rate control
Blood pressure regulation
Breathing
Swallowing
Vomiting

60. Regions of the Brain: Brain Stem
Reticular Formation
Diffuse mass of gray matter along the brain stem
Involved in motor control of visceral organs
Reticular activating system (RAS) plays a role in awake/sleep cycles and consciousness

61. Regions of the Brain: Reticular Formation of the Brain Stem
Figure 7.16b

62. Regions of the Brain: Cerebellum
Two hemispheres with convoluted surfaces
Provides involuntary coordination of body movements

63. Regions of the Brain: Cerebellum
Figure 7.16a