1. Nervous System

2. Responds to stimuli to maintain homeostasis. Stimulus (Stimuli) = a signal to which an organism reacts Response = some action or movement of an organism brought on by a stimulus

3. Nerve cells The cells of the nervous system are called neurons. Neurons carry messages called impulses Nerves = send messages to the spinal cord, muscles, and glands for response

5. The Neuron Cell body (cyton): contains nucleus, cell organelles; site of metabolic activities Nucleus : contains the genetic material Dendrite: receives impulses from other neurons and carries them toward the cell body

6. The Neuron Axon: carries impulses away from the cell body Schwann cell nucleus Schwann cell: surrounds the axon; produces the myelin sheath

7. The Neuron node of Ranvier: gap between neighboring Schwann cells Myelin sheath: insulation that increases the speed at which the impulse can travel

8. The Neuron Terminal branches the axon terminates (ends) with the terminal branches Synaptic knobs: release neurotransmitters into the synapse

9. The Neuron Synapse: small gap between two successive neurons ***Neurotransmitters are chemicals used to transmit an impulse from the axon of one neuron to the dendrites of the next neuron

10. Types of Neurons Sensory Neurons: transmit impulses from sensory organs (receptors) to the spinal cord and brain Sensory organs: eyes, ears, nose, mouth, skin

11. Types of Neurons Motor Neurons: transmit impulses from the spinal cord and brain to muscles and glands (effectors)

12. Types of Neurons Interneurons: connect sensory and motor neurons Found ONLY in the Central Nervous System (brain and spinal cord)

13. Reflex Arc Receptor  sensory neuron  interneuron  motor neuron  effector

14. Reflexes Automatic responses to stimuli  We do not have to think about the response They are inborn  All connections have been formed by the time we are born They are fast  They take the shortest path  The speed of the response is protective reflex arc animation

15. Central Nervous System Part of the nervous system that contains the brain and spinal cord.

16. The Brain Coordinates all of your body activities The brain is made of 100 billion neurons Interprets stimuli, sends impulses to the body

17. Cerebrum Largest part of the brain Thinking takes place here Controls:  Memory  Movement  Thinking

18. Cerebellum Coordinates voluntary muscle movement Maintains muscle tone Maintains balance Receives stimuli from eyes, ears, muscles, and tendons.

19. Brain Stem Located at the base of the brain Connects the brain to the spinal cord Contains:  Midbrain and Pons = pathways connecting various parts of the brain with each other  Medulla = controls involuntary actions

20. Spinal Cord Extension of the brain stem Made of bundles of neurons that carries impulses to all parts of the body

21. The peripheral nervous system (PNS) All the nerves that extend out of the brain an spinal cord Most of the PNS is under your direct control

22. THE PNS Autonomic Nervous System: controls body activities that are involuntary  Contractions of heart muscle  Movement of smooth muscles

23. Disorders of the Nervous System Alzheimer's Diseases  A progressive disease that destroys memory and other important mental functions  Brain cell connections and the cells themselves degenerate and die  There is no cure

24. Disorders of the Nervous System Amyotrophic Lateral Sclerosis (ALS)  Weakens muscles and impacts physical function  Nerve cells break down, which reduces the function of muscles.  There is no cure for ALS

25. Disorders of the Nervous System Epilepsy  A disorder in which nerve cell activity in the brain is disturbed, causing seizures  Can be caused by genetics or a brain injury  Treated by medications, surgery, devices, or dietary changes

26. Disorders of the Nervous System Meningitis  Infection and inflammation of the membranes surrounding the brain or spinal cord  Vaccines can prevent some forms of meningitis  Depending on the cause, it may get better on its own, or it can be life-threatening

27. Disorders of the Nervous System Multiple Sclerosis  Our WBCs attack and destroy Schwann cells  This slows down the impulses from neurons