The Nervous System

1. The Nervous System

2. OUTLINE • Nervous System • Central Nervous System • Peripheral Nervous System • Effects of Aging • Homeostasis

3. Part I – Nervous System

4. NERVOUS SYSTEM • Objectives • Description of the three functions of the nervous system. • Description of the structure of a neuron. • Description of the three types of neurons and their functions. • How the nerve impulse is conducted along a nerve and across a synapse.

5. The Three Functions of the Nervous System Functions Descriptions • Sensory Input Example: Temperature sensors in the skin may signal to the brain that the air surrounding the body is cold. • Sensory receptors in skin and organs respond to external and internal stimuli by generating nerve signals that travel to the brain and spinal cord.

6. The Three Functions of the Nervous System Functions Descriptions • Integration Example: Sensory information from temperature receptors is sent to the hypothalamus, the brain center that controls body temperature. • The brain and spinal cord interpret the data received from sensory receptors all over the body, and signal the appropriate nerve responses.

7. The Three Functions of the Nervous System Functions Descriptions • Motor Output Example: To adjust the body temperature, the hypothalamus triggers shivering – skeletal muscles contract rhythmically, producing heat that warms the body. • The nerve impulses from the brain and spinal cord go to the effectors, which are muscles, glands, and organs. Muscle contractions, gland secretions, and changes in organ function are responses to stimuli received by sensory receptors.

8. The Structure of a Neuron • The neurons have three parts: • Cell Body – contains the nucleus and other organelles • Dendrite – are shorter, branched extensions that receive signals from sensory receptors or other neurons. Their signals can result in nerve impulses that are then conducted away from the cell body by an axon. • Axon – May be grouped together in bundles. If they are in the peripheral nervous system they are called NERVE. On the other hand if they are in the (PNS) central nervous system (CNS) they are called TRACT.

9. The Structure of a Neuron The Axon may be covered by myelin. The myelin is a lipid coating that insulates the nerve. The NERVE covered by myelin is called Schwann Cells or Neurolemmocytes. The TRACT covered by myelin is called Oligodendrocytes.

10. The Structure of a Neuron

11. The Three Types of Neurons and their Functions Types of neurons description • Motor Neurons (They are multipolar because they have many dendrites and a single axon) • Take the nerve impulses from the CNS to muscles, organs, or glands. They cause the muscles fibers to contract, glands to secrete and organs to modify their functions.

12. The Three Types of Neurons and their Functions • Motor Neurons

13. The Three Types of Neurons and their Functions Types of neurons description • Sensory Neurons (have a structure that is termed as unipolar). • Take nerve impulses from sensory receptors to the CNS. The extension from the cell body divides into a branch that comes to the peripheral and another that goes to the CNS.

14. The Three Types of Neurons and their Functions • Sensory Neurons

15. The Three Types of Neurons and their Functions Types of neurons description • Interneurons or Association Neurons (Are typically multipolar, convey nerve impulses between various parts of the CNS) • Occur entirely within the CNS. Lie between Sensory and Motor neurons and some take messages from one side of the spinal cord to the other or from the brain to the cord or vice versa. Also form complex pathways in the brain where thinking, memory and language occur.

16. The Three Types of Neurons and their Functions • Interneurons or Association Neurons

17. The Nerve Impulse • http://www.google.com/url?sa=t&rct=j&q=how%20the%20nerve%20impulse%20is%20conducted%20along%20a%20nerve%20and%20across%20a%20synapse%20ppt&source=web&cd=3&cad=rja&ved=0CEEQFjAC&url=http%3A%2F%2Fhighered.mcgraw-hill.com%2Fsites%2F0072495855%2Fstudent_view0%2Fchapter14%2Fanimation__the_nerve_impulse.html&ei=UHDvUI35Go2o8AS7moGAAw&usg=AFQjCNHdXeK0pUahGyB8Ykq0unfTye7Bdw&bvm=bv.1357700187,d.eWU

18. Part II – Central Nervous System

19. CENTRAL NERVOUS SYSTEM • Objectives • Description and functions of the major parts of the brain. • Description and functions of the major parts of the lobes of the cerebral cortex. • Structure and functions of the spinal cord. • Description and functions of the three layers of meninges. • Location and function of cerebrospinal fluid.

20. Description and Functions of the Major Parts of the Brain Parts of the Brain Function 1. Cerebrum • Is the largest portion of the brain. • Is the last center to receive sensory input and carry out integration before commanding voluntary motor responses.

21. Description and Functions of the Major Parts of the Brain Parts of the Brain Function 1. Cerebrum (function continuation) • Communicates with and coordinates the activities of the other parts of the brain. • Carries out the higher thought processes required for learning and memory and for language and speech.

22. Description and Functions of the Major Parts of the Brain Parts of the Brain Description 1. Cerebrum • Has two halves: • Right Cerebral Hemisphere • Left Cerebral Hemisphere • Both Cerebral Hemispheres are connected by the Corpus Callosum (white matter)

23. Description and Functions of the Major Parts of the Brain Parts of the Brain Description 1. Cerebrum (description continuation) • Both hemisphere are divided into lobes: • Frontal Lobe. • Occipital Lobe. • Parietal Lobe. • Temporal lobe. • Insula Lobe. • The cerebral cortex is covered by the gray matter.

24. Cerebrum

25. Description and Functions of the Major Parts of the Brain Parts of the Brain Function 2. Diencephalon • Is the part of the forebrain that contains such important structures as the thalamus, hypothalamus and the posterior portion of the pituitary gland

26. Description and Functions of the Major Parts of the Brain Parts of the Brain Description 2. Diencephalon • Is a region that encircles the third ventricle • The hypothalamus forms the floor of the third ventricle. • Maintains homeostasis by regulating hunger, sleep, thirst, body temperature and water balance.

27. Description and Functions of the Major Parts of the Brain Parts of the Brain Description 2. Diencephalon (description continuation) • The hypothalamus is the link between the nervous and endocrine system. • The thalamus consists of two masses of gray matter located in the sides and roof of the third ventricle.

28. Description and Functions of the Major Parts of the Brain Parts of the Brain Description 2. Diencephalon (description continuation) • Is on the receiving end for all sensory input with the exception of smell. • The pineal gland is also located in the diencephalon and secretes the hormone melatonin and regulates our body’s daily rhythms.

29. Diencephalon

30. Description and Functions of the Major Parts of the Brain Parts of the Brain Function 3. Cerebellum • Receives sensory input from the eyes, ears, joints, and muscles about the present position of body parts. • Also receives motor inputs from the cerebral cortex about where these parts should be located.

31. Description and Functions of the Major Parts of the Brain Parts of the Brain Function 3. Cerebellum (function continuation) • After integrating this information, the cerebellum sends motor impulses by way of the brain stem to the skeletal muscles. • This way the cerebellum maintains posture and balance.

32. Description and Functions of the Major Parts of the Brain Parts of the Brain Function 3. Cerebellum (function continuation) • Also ensures that all of the muscles work together to produce smooth, coordinated voluntary movements. • In addition assists the learning of new motor skills like playing the piano.

33. Description and Functions of the Major Parts of the Brain Parts of the Brain Description 3. Cerebellum • It is separated from the brain stem by the fourth ventricle. • Has two hemispheres, which are joined by a narrow median portion. • Each portion is primarily composed of white matter, which in longitudinal section has a treelike pattern.

34. Description and Functions of the Major Parts of the Brain Parts of the Brain Description 3. Cerebellum (description continuation) • Overlying the white matter is a thin layer of gray matter that forms a series of complex folds.

35. Cerebellum

36. Description and Functions of the Major Parts of the Brain Parts of the Brain Function 4. Brain Stem • The brainstem plays a role in conduction. That is, all information relayed from the body to the cerebrum and cerebellum and vice versa, must traverse the brain stem.

37. Description and Functions of the Major Parts of the Brain Parts of the Brain Description 4. Brain Stem • Contains: • Midbrain • Pons • Medulla Oblongata • Reticular Formation • Midbrain acts as a relay station for tracts passing between the cerebrum and the spinal cord or cerebellum.

38. Description and Functions of the Major Parts of the Brain Parts of the Brain Description 4. Brain Stem (description continuation) • Pons contains bundles of axons traveling between the cerebellum and the rest of the CNS. • Medulla Oblongata contains a number of reflex centers for regulating heartbeat, breathing and vasoconstriction.

39. Description and Functions of the Major Parts of the Brain Parts of the Brain Description 4. Brain Stem (description continuation) • Reticular Formation assists the cerebellum in maintaining muscle tone. Also assists the pons and medulla in regulating respiration, heart rate and blood pressure.

40. Brain Stem

41. Description and Functions of the Major Parts of the Lobes of the Cerebral Cortex Parts of the Cerebral Cortex Lobes description 1. Frontal Lobe 2. Parietal Lobe 3. Occipital Lobe 1. Lies under the frontal bone. 2. Posterior to the Frontal Lobe. 3. Is deep to the occipital bone.

42. Description and Functions of the Major Parts of the Lobes of the Cerebral Cortex Parts of the Cerebral Cortex Lobes description 4. Temporal Lobe 5. Insula 4. Is the lateral portion of the cerebral hemisphere. 5. Very small lobe, directly deep to the lateral sulcus

43. Description and Functions of the Major Parts of the Lobes of the Cerebral Cortex Parts of the Cerebral Cortex Lobes Functions 1. Frontal Lobe • Control the functioning of sequencing events, which is the ability to plan a series of movements needed to perform a multi-step task. • Spontaneity of facial expression and of interaction with others.

44. Frontal Lobe

45. Description and Functions of the Major Parts of the Lobes of the Cerebral Cortex Parts of the Cerebral Cortex Lobes Functions 2. Parietal Lobe • Can be divided into two functional regions. • sensation and perception • integrating sensory input, primarily with the visual system.

46. Parietal Lobe

47. Description and Functions of the Major Parts of the Lobes of the Cerebral Cortex Parts of the Cerebral Cortex Lobes Functions 3. Occipital Lobe • The primary function of the occipital lobe is controlling vision and visual processing.

48. Occipital Lobe

49. Description and Functions of the Major Parts of the Lobes of the Cerebral Cortex Parts of the Cerebral Cortex Lobes Functions 4. Temporal Lobe • Plays an important role in organizing sensory input, auditory perception, language and speech production, as well as memory association and formation.

50. Temporal Lobe