AP Bio – 3/19/13

1. AP Bio – 3/19/13 The Nervous System, Chp.48 Body Systems Test Thursday (Chp.40, 43 (Immune), 45 (Endocrine), & 48 (Nervous)

2. Animals have nervous systems that detect external and internal signals, transmit and integrate information, and produce responses. The Nervous System

3. What trends do you notice?

4. Noteworthy Trends In Development • Increase in ganglia • Increase in sensory reception • Increase in cephalization • Cephalization is the concentration of nervous tissue in the anterior region of the organism.

5. Human Nervous System

8. Neuron = nerve cells • The neuron is the basic structure of the nervous system that reflects function. • Neuron structure allows for the detection, generation, transmission, and integration of signal information.

10. Neuron Anatomy • A typical neuron has a cell body, axon and dendrites.

11. Myelin Sheath • Axon coated with Schwann cells • insulates axon • speeds signal • signal hops from node to node • saltatory conduction

12. action potential saltatory conduction Na+ myelin + – axon + + + – + Na+ • Multiple Sclerosis • immune system (T cells) attack myelin sheath • loss of signal

13. dendrite  cell body  axon signal direction • Structure fits function • many entry points for signal • one path out • transmits signal dendrites cellbody axon signal direction synaptic terminal myelin sheath synapse

14. EvolutionaryAdaptations of Axon Structure • The speed of an action potential increases with the axon’s diameter • In vertebrates, axons are insulated by a myelin sheath, which causes an action potential’s speed to increase

15. Node of Ranvier Layers of myelin Axon Schwanncell Schwanncell Nodes ofRanvier Nucleus ofSchwann cell Axon Myelin sheath 0.1 m

16. Saltatory Conduction • Saltatory conduction. Notice that the conduction along a myelinated axon can occur quickly as large spaces can be skipped and impulse propagation occurs only at the nodes of Ranvier. Schwann cell Depolarized region(node of Ranvier) Cell body Myelinsheath Axon

17. Describe a Resting Potential: • What is the charge inside the neuron at rest? • Membranes of neurons are polarized by the establishment of electrical potentials across the membranes

18. Source of Charge Differences:

19. Action Potential • Action potentials propagate impulses along neurons. • In response to a stimulus, Na+ and K+ gated channels sequentially open and cause the membrane to become locally depolarized. • Na+/K+ pumps, powered by ATP, work to maintain membrane potential.

20. Figure 48.11a 1 2 3 4 5 1 50 Actionpotential 0 Membrane potential(mV) Threshold 50 Resting potential 100 Time

21. Action potential graph • Resting potential • Stimulus reaches threshold potential • DepolarizationNa+ channels open; K+ channels closed • Na+ channels close; K+ channels open • Repolarizationreset charge gradient • UndershootK+ channels close slowly 40 mV 4 30 mV 20 mV Depolarization Na+ flows in Repolarization K+flows out 10 mV 0 mV –10 mV 3 5 Membrane potential –20 mV –30 mV –40 mV Hyperpolarization (undershoot) Threshold –50 mV –60 mV 2 –70 mV 1 6 Resting Resting potential –80 mV

22. 1 1 • At resting potential • Most voltage-gated sodium (Na+) channels are closed; most of the voltage-gated potassium (K+) channels are also closed Key Na K 50 0 Membrane potential(mV) Threshold 50 Resting potential 100 Time OUTSIDE OF CELL Sodiumchannel Potassiumchannel INSIDE OF CELL Inactivation loop Resting state

23. 2 1 1 2 • When an action potential is generated • Voltage-gated Na+ channels open first and Na+ flows into the cell 50 Depolarization OUTSIDE OF CELL Sodiumchannel Potassiumchannel 0 Membrane potential(mV) Threshold 50 INSIDE OF CELL Resting potential Resting state 100 Inactivation loop Time

24. 3 2 1 3 1 2 Key Na K Actionpotential 50 Rising phase of the action potential • During the rising phase, the threshold is crossed, and the membrane potential increases to and past zero 0 Membrane potential(mV) 50 Depolarization 100 Time OUTSIDE OF CELL Sodiumchannel Potassiumchannel INSIDE OF CELL Inactivation loop Resting state

25. 4 3 2 1 4 3 1 2 Key Na K • 4. During the falling phase, voltage-gated Na+ channels become inactivated; voltage-gated K+ channels open, and K+ flows out of the cell Falling phase of the action potential Rising phase of the action potential 50 Actionpotential 0 Membrane potential(mV) Threshold 50 Depolarization Resting potential 100 Time OUTSIDE OF CELL Sodiumchannel Potassiumchannel INSIDE OF CELL Inactivation loop Resting state

26. 5. During the undershoot, membrane permeability to K+ is at first higher than at rest, then voltage-gated K+ channels close and resting potential is restored ***Action potentials travel in only one direction: toward the synaptic terminals

27. 1 5 4 3 2 1 5 4 3 1 2 Key Na K Falling phase of the action potential Rising phase of the action potential 50 Actionpotential 0 Membrane potential(mV) Threshold 50 Depolarization Resting potential 100 Time OUTSIDE OF CELL Sodiumchannel Potassiumchannel INSIDE OF CELL Inactivation loop Resting state Undershoot

28. Sequence the following in order of occurrence • Depolarization • Resting state • Repolarization • Hyperpolarization

29. Sequenced in order of occurrence • Resting state • Depolarization • Hyperpolarization • Repolarization • Resting state

30. 1 2 3 4 5 1 50 ? • Resting state • Depolarization • Hyperpolarization • Repolarization • Resting state 0 Membrane potential(mV) ? 50 ? 100 Time

31. Adding a poison that specifically disables the Na+/K+ pumps to a culture of neurons will cause a. the resting membrane potential to drop to 0 mV. b. the inside of the neuron to become more negative relative to the outside. c. the inside of the neuron to become positively charged relative to the outside. d. sodium to diffuse out of the cell and potassium to diffuse into the cell.

32. How does the nerve re-set itself? • Sodium-Potassium pump • active transport protein in membrane • requires ATP • 3 Na+ pumped out • 2 K+ pumped in • re-sets chargeacross membrane ATP

33. Name three specific adaptions of the neuron membrane that allow it to specialize in conduction

34. What happens when the impulse reaches the end of the axon?

35. Synapses • Transmission of information between neurons occurs across synapses. • A chemical synapse is a junction between two nerve cells consisting of a narrow gap across which impulses pass by means of a neurotransmitter

36. Cell To Cell Communication Events • Action potential depolarized the membrane of synaptic terminal, this triggers an influx of Ca2+. • That causes synaptic vesicles to fuse with the membrane of the pre-synaptic neuron. • Vesicles release neurotransmitter molecules into the synaptic cleft. • Neurotransmitters bind to the receptors of ion channels embedded in the postsynaptic membrane.

37. Note the structural features that allow the cell to cell communication to occur in the synaptic region: • Calcium gated channels in the synaptic knob • Sodium channels in the post-synaptic membrane • Fluidity of the lipid bi-layer allows for exocytosis of the neurotransmitter

39. Exocytosis Neurotransmitter release is a form of exocytosis. In exocytosis, internal vesicles fuse with the plasma membrane to secrete macromolecules out of the cell.

40. Neuron Transmitter Binds With A Receptor On The Postsynaptic Membrane

41. The neurotransmitter will then be released from the postsynaptic membrane and degraded.

42. Response Transmission of information along neurons and synapses results in a response. The response can be stimulatory or inhibitory.

44. ***There are more than 100 neurotransmitters 1 neurotransmitter may have more than a dozen different receptors • Acetylcholine • transmit signal to skeletal muscle • Epinephrine (adrenaline) & norepinephrine • fight-or-flight response • Dopamine • widespread in brain • affects sleep, mood, attention & learning • lack of dopamine in brain associated with Parkinson’s disease • excessive dopamine linked to schizophrenia • Serotonin • widespread in brain • affects sleep, mood, attention & learning

45. Neurotransmitters • Weak point of nervous system • any substance that affects neurotransmitters or mimics them affects nerve function • gases: nitrous oxide, carbon monoxide • mood altering drugs: • stimulants • amphetamines, caffeine, nicotine • depressants • quaaludes, barbiturates • hallucinogenic drugs: LSD, peyote • SSRIs: Prozac, Zoloft, Paxil • poisons

46. Injecting ethylene glycol tetraacetic acid (EGTA), a chelating agent that prevents calcium ions from moving across membranes, to a synaptic region would likely a. increase the release of neurotransmitters by the presynaptic neuron. b. decrease the release of neurotransmitters by the presynaptic neuron. c. result in neurotransmitters being released, but could not bind to its receptors on the post synaptic neuron. d. result in the lack of calcium ions keeping the ligand-gated ion channels open on the post synaptic neurons.

47. Ex - Nervous and muscular The contraction of a muscle is a typical response generated by the nervous system. Muscle contraction demonstrates the interdependence of the nervous and muscle systems.

48. Motor cortex(control ofskeletal muscles) Somatosensory cortex(sense of touch) Frontal lobe Parietal lobe Prefrontal cortex(decision making,planning) Sensory associationcortex (integration ofsensory information) Visual associationcortex (combiningimages and objectrecognition) Broca’s area(forming speech) Temporal lobe Occipital lobe Auditory cortex (hearing) Visual cortex(processing visualstimuli and patternrecognition) Cerebellum Wernicke’s area(comprehending language)