Nervous System

1. Nervous System Honors Biology Powerpoint #3 Unit 8 – Chapter 35 pg. 897-904 The Senses Activities

2. Function of Nervous System: • Coordinates the body’s response to changes in its internal and external environments.

3. Neurons • Messages carried by nervous system are electrical impulses • Cells that transmit impulses are called NEURONS • 3 types of neurons: • Sensory: carry impulse from sense organ to spinal chord and brain • Motor: carry impulse from brain and spinal chord to muscles and glands • Interneurons: connect sensory and motor and carry impulses in between

4. Neurons Pyramidal neurons forming a network in the brain

5. Neurons: Structure • Cell Body (Soma): Cell’s “life support” center • Dendrites- conducts “signal” toward the cell body -- [input zone] • Receives signal from sensory cell or neighboring neuron

6. Axon - usually a single fiber -- [conducting zone] • conducts signal away from cell body to another neuron or effector cell • Axon Ending- a cluster of branches (100’s to 1000’s) that relays signal to next neuron / effector cell

7. Myelin Sheath • Covers the axon of some neurons • Allows signal to travel faster because impulse “jumps” from node of Ranvier to node of Ranvier (with myelin sheath (225 mph / without 11 mph)

8. Multiple Sclerosis • Immune System attacks Myelin in brain and spinal chord

9. Loss of motor functions Multiple Sclerosis (MS)

11. How a nerve impulse is transmitted 1) At Rest - The neuron is POLARIZED(-70mV) There is a slightly negative charge on the inside, and a positive charge on the outside….. Why? • balance is maintained by the sodium-potassium pump (active transport) • Pumps Na+ (sodium) outside & Pumps K+ (potassium) inside • Membrane leaks and some K+ goes back out • Resting Potential= -70mV because overall postive charge outside and negative charge inside

12. How a nerve impulse is transmitted 2) Depolarization • Stimulus causes opening of Na+ gates, allowing Na+ to rush in (facilitated diffusion) • changes the neuron from polarized to de-polarized then to + 30mV • Reversal of charges = Nerve impulse aka Action Potential

13. How a nerve impulse is transmitted 2) Depolarization • This is all-or-none, meaning a stimulus must exceed a threshold for the action potential to occur • Intensity of the stimulus is based on the number of neurons that exhibit an action potential. • Speed of impulse based on diameter of axon & amount of myelination.

14. How a nerve impulse is transmitted 3) Repolarization • After inside flooded with NA+, K+ gates open and let K+ out (while NA+ gates close) • The inside becomes –while outside become + and this repolarizes membrane

15. How a nerve impulse is transmitted 4) Refractory period • When the Na+/K+ balance returns to normal (K+ on inside and Na+ outside) • During this time the neuron will not respond to new impulses

17. Nerve Impulse Transmission

18. The Synapse • Action potential happens • Neurotransmitter is released by axon ending • Neurotransmitter is a chemical that sends a signal • Neurotransmitter binds to dendrite membrane of next neuron • Excitation or inhibition of the membrane occurs • Neurotransmitter is ‘recycled’ • Neurons DON’T touch • The gap between the axon of one neuron, and the dendrites of another is called the SYNAPSE

19. The Synapse

20. Divisions of the Nervous System: • Central Nervous System (CNS) • Peripheral Nervous system (PNS)

21. 1. The Central Nervous System (CNS) • Relays messages, processes information and analyzes information. • Includes: • Brain • Spinal Cord

22. Parts of the Brain • Cerebrum’s Purpose: • Controls voluntary activities of the body • Cite of intelligence, learning, and judgment • Made up of frontal, parietal, occipital, and temporal lobes

24. Phineus Gage

25. Parts of the brain • Cerebellum: coordination and balance • Brain stem: regulates blood pressure, heart rate, breathing, and swallowing

26. Parts of Brain • Thalamus: relays sensory input to proper region of cerebrum • Hypothalamus: control center for recognition and analysis of hunger, thirst, fatigue, anger, and body temperature

27. 2. Peripheral Nervous System: everything outside of CNS • Sensory Division: transmits impulses from sense organs to central nervous system • What are sense organs? • Organs designed to pick up stimuli (name 5 sense organs) • Motor Division:Transmits impulses from CNS to the muscles or glands

28. Quick Quiz: Which is sensory which is motor? Sensory Motor • Seeing • Raising your hand • Tasting • Blinking when a ball is thrown past your face Sensory Sensory when you see the ball, motor when you blink

29. Motor Division of PNS • 2 parts • Somatic Nervous system • Regulates activities under conscious control (ex. Moving skeletal muscles) • Some involved with reflexes and can act without conscious control (see next slide) • Autonomic Nervous System • Regulates activities that are automatic or involuntary • Example: when running, speeds up heart and blood flow, stimulates sweat glands and slows down digestion • Divided into sympathetic and parasympathetic

30. Reflex Arc • Sensory neuron interneuron motor neuron • Without brain processing

31. Reflex Arc

33. Parkinson’s Disease

34. Cause • Parkinson's disease is a disorder of the brain that leads to shaking (tremors) and difficulty with walking, movement, and coordination. • Caused by loss of dopamine producing cells in brain (substantianiagra) • Dopamine helps control muscle movement by releasing inhibitory function of substantianiagraso things are not moving when not specifically told to do so • Without dopamine,it takes more effort for each motion and movements are shaky

35. DON’T DO DRUGS!!!!!