Human Anatomy & Physiology

Transcription

1 PowerPoint Lecture Slides prepared by Barbara Heard, Atlantic Cape Community College Ninth Edition Human Anatomy & Physiology C H A P T E R 11 Annie Leibovitz/Contact Press Images 2013 Pearson Education, Inc.

2 Nervous System Organization Anatomical: **Central Nervous System (brain, spinal cord) **Peripheral Nervous System (cranial nerves, spinal nerves, and beyond)

3 Nervous System Organization Functional: PNS organized into: **Afferent (towards CNS) aka sensory -Somatic sensory (skin, skel. m., joints) -Visceral sensory (organs) **Efferent (away from CNS) aka motor -Somatic nervous system (skeletal m.) -Autonomic nervous system (visceral motor system) -sympathetic, parasympathetic Nervous tissue made up of : ½ Neurons ½ Neuroglia

4 Neuroglia CNS A**holes Owe Everyone Money Astrocytes Oligocytes Ependymal Microglia PNS So Satellite Sucky!! Schwann

5 Central Nervous System contains Astrocytes -Largest most #s -Maintain blood brain barrier Oligodendrocytes -Myelinate CNS axons -provide structural framework Ependymal -Make CSF -Help with CSF flow TANGENT! 2012 Pearson Education, Inc.

6 Importance CSF Flow Research: why is sleep restorative? Lulu et al., Pearson Education, Inc.

7 Importance CSF Flow Amyloid-β (plaques) protein found in high quantities in Alzheimer s build up b/c no lymphatic connection During sleep neuroglia ramp up activity CSF flow é é Clears out wastes So, sleep drives the brain s metabolic trash service 2012 Pearson Education, Inc.

8 are found in Central Nervous System contains Astrocytes Oligodendrocytes -Largest most #s -Myelinate CNS axons -Maintain blood brain barrier -provide structural framework -Recycle NeuroTrans 2012 Pearson Education, Inc. Ependymal -Make CSF Microglia -least #s -Help with CSF flow -phagocytosis

9 Neuroglia are found in Peripheral Nervous System contains Satellite cells Regulate environment around neurons like Astrocytes Schwann cells myelination of peripheral axons; injury repair 2012 Pearson Education, Inc.

10 Neurons

11 Neurons Large Conduct impulses Extreme longevity ( 100 years or more) Amitotic mostly High metabolic rate lots of O 2 and C 6 H 12 O Pearson Education, Inc.

12 Collect info Toward cell body Dendrites Cell body Figure 11.4a Structure of a motor neuron. Neurotransmitter synth excite inhibit Two processes: Dendrites Axon Axon Conducting region Ions move across Axolemma generates nerve impulses from cell body =anterograde -use Kinesin 2013 Pearson Axon hillock Education, Inc. Impulse direction Axon terminals secretion of what? Neurotransmitters

13 to cell body =retrograde -use dynein

14 A little bit more about axons Conduct impulses myelin sheath helps this protein lipoid 70% fat insulates fibers = myelinated à rapid impulses no/low gap-junctions if non-insulated = non-myelinatedà slow impulses 2012 Pearson Education, Inc.

15 70% fat Schwann Cells Myelin Sheath in PNS one axon, myelinate segments only many axons, unmyelinated

16 Nodes: Spaces between Myelin Sheath

17 Myelin Sheath in CNS: Oligodendrocytes

18 CNS Regeneration is NOT Likely Oligodendrocytes aren t dedicated = NO Pathway Astrocytes release growth inhibitors

19 Arrangement of CNS Neuroglia make a pattern white matter Cell Bodies and Dendrites = Gray Matter Note myelin presence

20 Neurons Types

21 Yes, all neurons are shown like this: but there is diversity Two ways to categorize: 1. Structure 2. Function

22 4 Neuron Types (By Structure) relationships of the dendrites to the cell body no distinction dendrites from axons Two tails -dendritic -axon continuous >2 dendrite clusters Brain Rare In sense organs Sensory of PNS 1 meter long! Most common CNS can be as long as uni

23 3 Neuron Types (By Function) Sensory(afferent) Sensory(afferent) Motor(efferent) SAME principle

24 NeuroPhysiology: Three Types of Potentials

25 What does it mean to have potential? think of a dam water behind dam has lots of energy (mass, gravity, etc) water below less energy theoretical difference of energy between both sides cellular potential measured in Volts measuring differences in electrical charge one side of cell more positive, one side more negative How do we set up charge differences? plasma membrane, ports, ions 2012 Pearson Education, Inc.

26 Gated Channels

27 Lets set up the major players

28 Na + Na + Na + Na Na + + Na + Na + Na + Na + Na + Na Na + + Na + Na K + K + K + Na + K + K + K + K K + + K + K + K + K + >> K + >> Na + K + >> Na + K + K + K +

29 Resting Membrane Potential

30 Announcement Physio Ex Mastering AP Code 10 AM class schedule updated Exams My hat? 2012 Pearson Education, Inc.

31 Resting Potential à Action Potential (AP) If we change membrane permeability (i.e. let more ions in) à Graded potential à Action potential Membrane permeability impact is measured relative to the resting potential value which is??? -70 mv 2012 Pearson Education, Inc.

32 Resting Potential à Action Potential (AP) If permeability change sends charge below -70mV i.e. cell gets more negative = hyperpolarization 2012 Pearson Education, Inc.

33 Figure 11.9b Depolarization and hyperpolarization of the membrane. Hyperpolarizing stimulus How does this happen? Let the positively charged ions leave for a long time Inhibits an AP Membrane potential (voltage, mv) Resting potential Hyperpolarization Time (ms) 2012 Pearson Education, Inc.

34 Resting Potential à Action Potential (AP) If change sends charge above -70mV i.e. cell gets more positive = depolarization 2012 Pearson Education, Inc.

35 Figure 11.9a Depolarization and hyperpolarization of the membrane. How does this happen? Let the positively charged ions enter fast Facilitates an AP Membrane potential (voltage, mv) Depolarizing stimulus Inside positive Inside negative Resting potential Depolarization Time (ms) 2012 Pearson Education, Inc.

36 Graded Potentials Hyperpolarizations or depolarizations can happen at local regions Sometimes they are strong Sometimes they are week So like in a continuous scale a graded scale 2012 Pearson Education, Inc.

37 Figure 11.10a The spread and decay of a graded potential. Depolarized region Stimulus Plasma membrane Stimulus applied artificial or ECF 2012 Pearson Education, Inc.

38 Figure 11.10b The spread and decay of a graded potential. local currents develop 2012 Pearson Education, Inc.

39 Figure 11.10c The spread and decay of a graded potential. Membrane potential (mv) 70 Active area (site of initial depolarization) Resting potential Since localized they dissipate quickly Distance (a few mm) 2012 Pearson Education, Inc.

40 Graded Potentials Two types of Graded Potentials: 1. Receptor potential a receptor is affected e.g. a sensory neuron in the retina 2. Postsynaptic potential neurotransmitter à synapse à neuron#2 neuron#2 is after the synapse postsynaptic Graded potentials can be additive (back to this later) 2012 Pearson Education, Inc. à AP

41 Action Potentials Characteristics APs do not weaken over distance Regional: One AP happens in an area of an axolemma AP will generate currents of + charge that will affect adjacent areas APs move down axon in one direction Main way neurons send signals Main long-distance neural communication Let s set up the key players 2012 Pearson Education, Inc.

42 Voltage-gated Na + channels Two gates Activation gate Inactivation gate Closed Opened Inactivated 2013 Pearson Education, Inc.

43 So, how do these two interact? Voltage-gated K + channels Just one gate Closed 2013 Pearson Education, Inc. Opened

44 The events Sodium channel Potassium channel Inactivation gate Activation gates 2013 Pearson Education, Inc. 1 Resting state

45 The events 2013 Pearson Education, Inc. 2 Depolarization

46 The events 2013 Pearson Education, Inc. 3 Repolarization

47 The events 2013 Pearson Education, Inc. 4 Hyperpolarization

48 1 Resting state. No ions move through voltage-gated channels. Membrane potential (mv) Action potential Threshold Time (ms) 2013 Pearson Education, Inc.

49 1 Resting state. No ions move through voltage-gated channels. 2 Depolarization is caused by Na + flowing into the cell. Membrane potential (mv) Action potential Threshold Time (ms) 2013 Pearson Education, Inc.

50 2b Inactivation/Activation Na + inactivation/ K + activated 1 Resting state. No ions move through voltage-gated channels. 2 Depolarization is caused by Na + flowing into the cell. Membrane potential (mv) Action potential Threshold Time (ms) 2013 Pearson Education, Inc.

51 1 Resting state. No ions move through voltage-gated channels. 2 Depolarization is caused by Na + flowing into the cell. 3 Repolarization is caused by K + flowing out of the cell. Membrane potential (mv) Action potential Threshold Time (ms) 2013 Pearson Education, Inc.

52 1 Resting state. No 2 Depolarization ions move through is caused by Na + voltage-gated flowing into the cell. channels. 3 Repolarization is caused by K + flowing out of the cell. Membrane potential (mv) Action potential 4 Threshold 1 4 Hyperpolarization is caused by K + continuing to leave the cell Time (ms) 2013 Pearson Education, Inc.

53 1 Resting state. No 2 Depolarization ions move through is caused by Na + voltage-gated flowing into the cell. channels. 3 Repolarization is caused by K + flowing out of the cell. Membrane potential (mv) Action potential 4 Threshold 1 1 Need to re-establish this Time (ms) 2013 Pearson Education, Inc.

54 Na K Pumps Repolarization resets electrical conditions, not ionic conditions Na + /K + pumps restore ionic conditions 3 Na + out 2 K + in 2013 Pearson Education, Inc.

55 Resting Membrane Potential

56 Refractory Periods So, can a the AP curve be stimulated a second time to fire a 2 nd AP? It depends 2013 Pearson Education, Inc.

57 Refractory Periods Absolute: - Na+ channels open - Can not respond to another stimulus - no backwards flow! - one direction Relative: - most Na+ resting - 2 nd stronger stimulus à AP

58 Propagation Recap: APs happen in one place then spread Spread = propagation Two ways to propagate 1. continuous 2. saltatory

59 Stimulus Voltage-gated ion channel Continuous In nonmyelinated cells Slow 2013 Pearson Education, Inc.

60 Figure 11.15c Action potential propagation in nonmyelinated and myelinated axons. Myelin sheath Stimulus Myelin sheath Myelin sheath gap 1 mm Saltatory In myelinated cells Fast 2013 Pearson Education, Inc. What else besides myelination affects speed of APs?

61 Axon diameter Diameter also affects propagation of AP Think of a 6-lane highway vs. 2-lane highway: -large areaà fast flow -large diameter à low resistance Group A -large diameter, lots myelin -fast!, >268 MPH -position, balance, delicate touch Group B -medium diamter, little myelin -slower, 30 MPH -temp, touch, pain Group C -smallest diameter, nonmyelinated -slowest, <2 MPH -temp, touch, pain

62 Propagation APs are going somewhere Synapses

63 Figure Chemical synapses transmit signals from one neuron to another using neurotransmitters. Presynaptic neuron Postsynaptic neuron Presynaptic neuron 1 Action potential arrives at axon terminal. 2 Voltage-gated Ca 2+ channels open and Ca 2+ enters the axon terminal. Mitochondrion 3 Ca 2+ entry causes synaptic vesicles to release neurotransmitter by exocytosis Axon terminal Synaptic vesicles Synaptic cleft 4 Neurotransmitter diffuses across the synaptic cleft and binds to specific receptors on the postsynaptic membrane. Postsynaptic neuron Ion movement Graded potential Reuptake Enzymatic degradation 5 Binding of neurotransmitter opens ion channels, resulting in graded potentials. Diffusion away from synapse 6 Neurotransmitter effects are terminated by reuptake through transport proteins, enzymatic degradation, or diffusion away from the synapse Pearson Education, Inc.

64 Figure 11.16a Synapses. Axodendritic synapses Axosomatic synapses Dendrites Cell body Axoaxonal synapses Axon 2013 Pearson Education, Inc.

65 Postsynaptic Potentials Signals leaving the synapse are graded potentials Can be excitatory inhibitory 2013 Pearson Education, Inc.

66 Figure 11.18a Postsynaptic potentials can be excitatory or inhibitory. Membrane potential (mv) Stimulus Threshold Time (ms) EPSP can lead to threshold à depolarize à lead to AP. Excitatory postsynaptic potential (EPSP) 2013 Pearson Education, Inc.

67 Figure 11.18b Postsynaptic potentials can be excitatory or inhibitory. Membrane potential (mv) Stimulus Threshold IPSP leads to hyperpolarization Neuron driven away from AP threshold. Neurotransmitter binding opens K + or Cl channels Time (ms) Inhibitory postsynaptic potential (IPSP) 2013 Pearson Education, Inc.

68 Postsynaptic Potentials EPSP and IPSP can be additive summate by time by area 2013 Pearson Education, Inc.

69 Figure 11.19b Neural integration of EPSPs and IPSPs. E 1 Membrane potential (mv) Resting potential E 1 E 1 Time Threshold of axon of postsynaptic neuron Temporal summation: 2 excitatory stimuli close in time cause EPSPs that add together. Excitatory synapse 1 (E 1 ) Excitatory synapse 2 (E 2 ) 2013 Pearson Education, Inc. Inhibitory synapse (I 1 )

70 Figure 11.19c Neural integration of EPSPs and IPSPs. E 1 E 2 Membrane potential (mv) Resting potential E 1 + E 2 Time Threshold of axon of postsynaptic neuron Spatial summation: 2 simultaneous stimuli at different locations cause EPSPs that add together. Excitatory synapse 1 (E 1 ) Excitatory synapse 2 (E 2 ) 2013 Pearson Education, Inc. Inhibitory synapse (I 1 )

71 Figure 11.19d Neural integration of EPSPs and IPSPs. E 1 l 1 Membrane potential (mv) Threshold of axon of postsynaptic neuron Resting potential l 1 Time E 1 + l 1 Spatial summation of EPSPs and IPSPs: Changes in membane potential can cancel each other out. Excitatory synapse 1 (E 1 ) Excitatory synapse 2 (E 2 ) 2013 Pearson Education, Inc. Inhibitory synapse (I 1 )

72 Until now have focused on ACh Actetylcholine -Type of receptor: Cholinergic -Sometimes excitatory (i.e. generates an AP) -Sometimes Inhibitory (i.e. blocks an AP) -how do you block AP? -hyperpolarization -contrast hyperpolarization vs. depolarization Another neurotransmitter: Norepinephrine (aka. noradrenaline ) -Type of receptor: Adrenargic -typically excitatory Another neurotransmitter: GABA -inhibitory Another neurotransmitter: Nitric Oxide (gas) Think erections Neurotransmitters Many more