Neuron Anatomy

1. Neuron Anatomy

2. The nervous system also allows you to react to a stimulus. Stimulus A stimulus is a change in the environment. Example: A hot stove Or… tripping over a rock

3. Structure of a Vertebrate Neuron

5. Anatomy of a Neuron • Cell body: functional portion • Dendrites: short extensions that receive signals • Axon: long extension that transmits impulses away

6. Many vertebrate peripheral neurons have an insulating sheath around the axon called myelin which (white matter) is formed by Schwann cells. Myelinated Neurons • Myelin sheathing allows these neurons to conduct nerve impulses faster than in non-myelinated neurons (gray matter) • Node of Ranvier is the location where nervous impulses are conducted.

7. Basic Tasks of the Nervous System Sensory Input: Monitor both external and internal environments. Integration: Process the information and often integrate it with stored information. Motor output: If necessary, signal effector organs to make an appropriate response.

8. Nerve Impulse Messages carried throughout the body by nerves.

9. Saltatory Conduction in Myelinated Axons Myelin sheathing has bare patches of axon called nodes of Ranvier Action potentials jump from node to node Fig. 48.11

10. •At rest, the membrane maintains an electrical polarization called the resting membrane potential. –the inside of the membrane is slightly negative with respect to the outside. (approximately -70 millivolts) The Nerve Impulse

11. Depolarization – influx of Na+ ions

12. Repolarization – outflux of K+ ions

14. Nerve Impulse - The Action Potential Threshold potentialwill trigger an action potential or nerve impulse The action potential is an all-or-none response

15. INTEGRATION WITHIN THE CENTRAL NERVOUS SYSTEM • The nervous system gathers and processes information from the external and internal environments and then relays a response to the necessary areas of the body.

16. REFLEX ARC • Neurons allow the nervous system to relay sensory information to the brain and spinal cord for integration, and to produce a response, as needed, by the effectors.

17. How does a signal move from one neuron to another? • A synapse separates 2 neurons • The action potential will not move across the synapse • Neurotransmitters • Released by the signal cell to the receiver cell • Move by diffusion

19. Types of chemical neurotransmitters Excitatory: helps to initiate a response, making the cell membrane receptors more permeable • Acetylcholine: neuromuscular junctions, glands, brain and spinal cord • Norepinepherine: affects brain regions concerned with emotions, dreaming

20. Inhibitory neurotransmitters: is able to breakdown the excitatory neurotransmitters to prevent further action potentials from occuring. Cholinesterase: breaks down acetylcholine.

21. Central Nervous System The Central Nervous System is made of the brain and the spinal cord. The Central Nervous System controls everything in the body.

22. Nerves Sense organs Outer Nervous System The Outer Nervous System is made of the nerves and the sense organs.

23. The Central Nervous System

24. The Central Nervous System 1. The brain 2. The spinal cord * The Central Nervous System controls all of the body’s activities. * The Central Nervous System is made of two main organs.

25. The Spinal Cord * The spinal cord sends messages to the brain. * The spinal cord is the part of the nervous system that connects the brain to the rest of the nervous system.

26. The Brain * The brain controls everything in the body. * The brain is made of more than 10 billion nerves! * The brain is divided into three parts and is protected by the skull.

27. The Three Parts of the Brain * The Brain has three main parts… 1. The Cerebrum 2. The Cerebellum 3. The Brain Stem

28. The Cerebrum * The Cerebrum is the largest part of the brain. 1. The cerebrum controls your thinking. 2. The cerebrum controls your memory. 3. The cerebrum controls your speaking. 4. The cerebrum controls your movement and identifies the information gathered by your sense organs.

30. The right and left halves of the cerebral cortex (cerebrum) are made of four pairs of lobes, each of which is associated with particular functions: • FRONTAL lobes (conscious thought and movements, speech), • PARIETAL lobes (touch, taste), • TEMPORAL lobes (hearing and speech), • OCCIPITAL lobes (vision).

31. The Cerebellum 1. The cerebellum controls you balance. 2. The cerebellum controls your posture. * The cerebellum is below and to the back of the cerebrum.

33. The Brain Stem * The Brain Stem connects the brain to the spinal cord. * The nerves in the brain stem control your heartbeat, breathing, and blood pressure (MEDULLA OBLONGATA and HYPOTHALAMUS).

35. The Vertebrae * The vertebrae are the many bones that protect the nerves in the spinal cord.

36. The Outer Nervous System

37. Outer Nervous System * The outer nervous system carries messages between the central nervous system and the rest of the body. * The Outer Nervous System’s job is to connect the Central Nervous System to the rest of the body.

38. Nerves Eye Skin Ear Tongue Outer Nervous System * The outer nervous system is made of the nerves and the sense organs.

39. Reflex * An automatic reaction that happens without thinking about it. * A reflex happens quickly in less than a second.

41. controls Automatic Nervous System * The outer nervous system controls the body’s activities that you don’t think about. * The outer nervous system controls activities in your small intestine, your breathing, and your heartbeat.

44. Sense Organs Sense organs carry messages about the environment to the central nervous system.

45. Sense Organs The eyes, ears, nose, tongue, and skin are examples of sense organs. The sense organs gather information (light, sound, heat, and pressure) from the environment.

46. Environment The environment is everything outside the body. The sense organs gather information from outside the body, then send the messages to the brain.

47. Vision is your ability to see. Vision Vision involves the eye and the brain.

49. Parts of the Eye Detectors on the Fovea • Rods • light intensity and motion sensitive • Cones • color sensitive The blind spot for the eye is cause by the optic nerve.