The Nervous System ’ s Functional Units

1. Chapter 23 The Nervous System’s Functional Units • Neurons: Structure • Neurons: how are signals transmitted (Action Potentials) • Neurotransmitters

2. Brain Research through Advancing Innovative Neurotechnologies initiative: $100 million project On April 2nd, 2013 President Barack Obama announced the BRAIN project. “ As humans we can identify galaxies light years away, we can study particles smaller than an atom. But we still haven’t unlocked the mystery of the three poinds of matter that sits between our ears.” -President Obama >100 billion neurons in the human brain alone!!

3. Nobel Prize in Physiology or Medicine 2014 for discovering the inner GPS of the brain John O'KeefePrize May-Britt Moser Edvard I. Moser The Nobel Prize in Physiology or Medicine 2014 was "for their discoveries of cells that constitute a positioning system in the brain".

4. FUNCTIONS OF THE NERVOUS SYSTEM The nervous system—present in almost all multicellular animals—has three primary functions. RECEIVE INPUT The nervous system collects information about the internal and external environment. PROCESS INFORMATION The nervous system interprets the incoming stimuli and determines a response. INITIATE RESPONSE The nervous system sends signals to muscles and glands in response to the internal and external environment.

5. Nervous System Functions Pathways of Information Flow • Receive sensory input • Integrate the input • Respond to stimuli Somatic & Autonomic

6. THE VERTEBRATE NERVOUS SYSTEM In vertebrates, the nervous system is divided into the central nervous system and the peripheral nervous system. • CENTRAL NERVOUS SYSTEM • Composed of the neurons and other supporting cells that make up the brain and spinal cord • Brain • Spinal cord PERIPHERAL NERVOUS SYSTEM Composed of neurons that detect stimuli and neurons that transmit signals to the muscles and glands • Neurons (bundled together into nerves)

7. NEURON STRUCTURE Neurons—individual cells that specialize in carrying electrical signals—are the building blocks of the nervous system. They are composed of three distinct elements. Stimulus DENDRITES Sense and respond to stimulation from outside the cell and send that information toward the cell body CELL BODY Contains the nucleus and other cellular machinery AXON Long tube-like projection that extends from the cell body and transmits signals to other cells GLIAL CELLS Support cells that protect, insulate, and nourish the neurons

8. Neurons come in different shapes, but all have some common features DIRECTION OF SIGNAL

9. Axons Cell Body Dendrites Myelinated = 330 mi/hr Unmyelinated ~10 mi/hr

10. SIGNAL Axon Dendrites Nerve signals flow from dendrites to axons One neuron: Two neurons: SYNAPSE

11. Support cells: Glial cellsProtect, insulate and nourish Each bead-like structure that is strung along an axon is a single oligodendrocyte Microglia Microglia process harmful bacteria and act as the brain's immune cells.

12. Astrocytes Astrocytes can release gliotransmitters (like glutamate) by exocytosis to send signals to neighboring neuron End-feet" connect to blood vessels in the brain. And regulate local blood flow to neurons

13. Myelin Sheaths Axons are insulated, by a fatty coating called the myelin sheath, preventing the action potential from weakening as it travels down the axon. • The lack of myelin on an axon can be seen in babies when they first start trying to walk and their gross motor control isn’t very good.

14. Neurons Come in Three Types

15. Three Types of Neurons 1 Sensory Neuron Interneuron 2 3 Motor Neuron

16. You take a sip of coffee, and it’s too hot. The ___ of your __ receive this stimulus A. axons; motor neurons B. dendrites; motor neurons C. axons; sensory neurons D. dendrites; sensory neurons E. axons; interneurons

17. Sensory neurons: from skin and joints are affected by syphilis • Interneurons: affected by Parkinson’s • Motor neurons: affected by polio

18. Drawing of neuronal circuit by Santiago Ramon y Cajal: 1901 Modern day photomicrographs

19. Clarity: See through BrainNature: April 10, 2013 http://www.youtube.com/watch?v=c-NMfp13Uug&feature=youtu.be

20. How a “reflex action” occurs 1 2 3 4 5

21. What is letter G? A. Effector cells B. Interneuron C. Motor neuron D. Sensory receptors E. Synapse Ouch!!

22. How do neurons send “signals”? How does the nerve cell speak Through Action potentials and neurotransmitters

23. Human Connectome Project • Map of the network of connections between neurons in the human brain:Connectomes • Signals are transmitted from one brain region to another • Connectome of roundworm C. elegans has been done (300 neurons and 7000 connections) TED talk: I am my connectome

24. Neurons are excitable cells (their membrane potential can change rapidly) Membrane potential (action potential) depend on ions Resting Potential Action Potential -70 mV +30mV (depolarized)

25. Using Giant Axon of Squid to figure out nerve impulses • Voltage gated channels • Sodium gates • Potassium gates • Pottasium channels (non-gated ion channels) • Sodium potassium pumps

26. Dendrites receive external stimuli.

27. Axon Terminal Buttons

28. Axon Action potential Axonsegment 1 Na+ Action potential K+ 2 Na+ K+ Action potential K+ 3 Na+ K+ The action potential travels along a neuron http://bcs.whfreeman.com/thelifewire/content/chp44/4402s.swf

29. If these channels do not work, disorders can result. • Channelopathies (disorders of ion channels) • Epilepsy: potassium channel mutations • Muscle weakness • Ciguatoxin: Shellfish: blocks sodium channel (numbness, muscle weakness) • Neurotoxin by puffer fish paralyzes

30. The action potential is an“all-or-nothing” spike Action potential is triggered only when threshold potential is reached - Always the same size http://bcs.whfreeman.com/thelifewire/content/chp44/4402s.swf

31. The presence of myelin allows an axon to ___ • Produce more frequent action potentials • Conduct impulses more rapidly • Produce action potentials of larger amplitude • Produce action potentials of longer duration

32. How are powerful stimuli sensed? The intensity of the sensation depends on the number the number of neurons that fire. Action potentials become more frequent for a strong signal

33. Pick the term that describes the membrane potential changes from -80mV to -70mV • Hyperpolarize • Depolarize • Repolarize

34. Action potentialstravel WITHIN neurons. How do neurons pass information? A junction between a neuron and another cell is called a synapse. Signals are passed between neurons mostly by Chemical signals (neurotransmitters) in humans Neurotransmitters travel BETWEEN neurons (at synapses).

35. THE SYNAPSE Action potential Presynaptic membrane Positively charged ions Vesicles Neurotransmitter molecules Synaptic cleft Postsynaptic membrane Receptor proteins Ion channels This causes a channel to open, allowing ions to flow into the cell, stimulating or inhibiting it. neurotransmitters are then released from the receptors, and either taken back in and recycled by the initial axon , or are broken down by enzymes 1 2 Neurotrans-mitters bind to receptor on the adjacent cell membrane 3 4 Vesicles release neurotransmitters into the synapse

36. Neurotransmitters must be removed from the synapse • They are either destroyed by enzymes, or.. • Re-absorbed by the neuron that released them Medications and recreations drugs can interfere with these processes

37. At the Synapse, Several Things Occur… • The action potential in a pre synaptic neuron triggers calcium to enter the neuron. Calcium causes sacs called vesicles to release neurotransmitters into the synaptic cleft. 2. The neurotransmitter diffuses to nearby receptor sites of a post synaptic neuron. 3.The neurotransmitter attaches to postsynaptic receptors. 4. Gates open in the postsynaptic cell membrane.

38. At the Synapse, Several Things Occur… 5.Open gates enable the signal to pass to the postsynaptic cell. 6. Neurotransmitter is released from the postsynaptic cell receptors. 7. Neurotransmitter is recycled by being taken back into the pre-synaptic neuron or broken down by enzymes.

39. 5 1 What is labeled as #4 ? • Transporter • Neurotransmitter • Vesicles • Receptor 2 3 4 6

40. Neurotransmitters Excitatory: increases membrane potential and increases chance for threshold to be reached Inhibitory: decreases membrane potential and decreases chance for threshold to be reached Examples 1. Acetylcholine: stimulates muscle contraction 2. Dopamine : feeling good 3. Serotonin: feeling good, Sleep, appetite and mood, pain 4. Endorphins: decrease pain 5. Glutamate: Excitatory NT 6. GABA: Inhibitory NT

41. Acetylcholine • Acetylcholine is the neurotransmitter released by motor neurons at the point where they synapse with muscle cells. • When enough acetylcholine binds to a muscle cell, the muscle contracts. • Deficiency: Alzheimers Autoimmune disease: destroy Ach receptors: Myasthenia gravis

42. Curare is a poison that works by blocking the receptor sites where acetylcholine binds to muscle cells Botox

43. Glutamate and GABA (work together) • Glutamate: excitatory NT and over half of all brain synapses release glutamate. It starts action potential or keeps it going. • GABA: inhibitory NT. Released by 30-40% of brain synapses and it stops action potentials. • Caffeine ____ glutamate and _____ GABA activity

44. Dopamine controls movement and posture. Also chief happiness NT. Dopamine Deficiency causes Parkinsons. • Serotonin generally is an inhibitory NT. • It affects appetite, sleep, anxiety, pain, mood and produces feelings of contentment and satiation • Problems: anxiety disorders, OCD, and depression

45. Drugs can hijack pleasure pathways Our nervous system can be tricked by chemicals Drugs—whether recreational or therapeutic, whether found in nature or made in the laboratory—can work by mimicking neurotransmitters Examples of Drugs • Cocaine • Morphine and Heroin • Nicotine • Prozac, Zoloft • Ritalin

46. Cocaine, Prozac, and Zoloft

47. Morphine and Heroin • Mimic endorphins and bind to their receptor sites. Nicotine Mimics acetylcholine. Fooled by the nicotine binding to acetylcholine receptors, cells release adrenaline and other stimulating chemicals, including pleasure-causing dopamine. Rapid surges, then rapid depletions.

48. Do human drug addictions and dependencies reflect differences in our genes? The allele of the DRD4 gene found among one-third of the smokers in a study was the same one that appears to cause individuals to exhibit a variety of personality traits associated with risk-taking and novelty-seeking behavior.

49. Alcohol interferes with many different neurotransmitters. Alcohol fools at least four different receptor molecules. • Blocks glutamate receptors • Blocks dopamine reuptake • Releases endorphins • Increases efficiency of serotonin receptors

50. Alcohol interferes with many different neurotransmitters. Dopamine, serotonin, gaba, glutamate Alcohol ___ GABA activity and ___ Glutamate activity. • Increases ; Increases • Increases; Decreases • Decreases; Increases • Decreases; Decreases