1. The Nervous System

2. 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 an effector

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

4. The Reflex Arc
Stimulus at distal end of neuron
Skin
Receptor
(a)

5. The Reflex Arc Skin Stimulus at distal end of neuron Sensory neuron
Receptor
Sensory neuron
(a)

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

7. 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

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

9. Simple Reflex Arc
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)

10. Sensory receptors (stretch receptors in the quadriceps muscle)
Spinal cord
(b)

11. Sensory receptors (stretch receptors in the quadriceps muscle)
Sensory (afferent) neuron
Spinal cord
(b)

12. Sensory receptors (stretch receptors in the quadriceps muscle)
Sensory (afferent) neuron
Spinal cord
Synapse in ventral horn gray matter
(b)

13. Sensory receptors (stretch receptors in the quadriceps muscle)
Sensory (afferent) neuron
Spinal cord
Synapse in ventral horn gray matter
Motor (efferent) neuron
(b)

14. 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)

15. Sensory receptors (pain receptors in the skin)
Spinal cord
(c)

16. Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
(c)

17. Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
Inter- neuron
(c)

18. Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
Inter- neuron
Motor (efferent) neuron
(c)

19. Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
Inter- neuron
Motor (efferent) neuron
Effector (biceps brachii muscle)
(c)

20. 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)

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

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

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

24. Central Nervous System (CNS)
Ventricles
Four chambers within the brain
Filled with cerebrospinal fluid

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

26. Cerebrum
Figure 7.14

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

28. Regions of the Brain: Cerebrum
Figure 7.13c

29. 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

30. Cerebrum

31. Regions of the Brain: Diencephalon
Figure 7.16

32. Diencephalon (Interbrain)
On top of the brain stem
Enclosed by the cerebral hemispheres
Made of three parts
Thalamus
Hypothalamus
Epithalamus

33. Diencephalon
Figure 7.12b

34. Diencephalon
Figure 7.16a

35. Diencephalon

36. Diencephalon Thalamus The relay station for sensory impulses
Pleasant vs. unpleasant
Transfers impulses to the sensory cortex

37. Diencephalon Hypothalamus Important autonomic nervous system center
Regulate body temperature
Controls water balance
Regulates metabolism

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

39. Diencephalon Epithalamus Forms the roof of the third ventricle
Houses the pineal body (an endocrine gland)
Choroid plexus—forms cerebrospinal fluid

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

41. Brain Stem
Figure 7.16a

42. 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

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

44. 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

45. 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

46. RETICULAR FORMATION OF THE BRAIN STEM
Figure 7.16b