Presentation is loading. Please wait.

Presentation is loading. Please wait.

Nervous Tissue. Nervous System CNS (brain and spinal cord) CNS (brain and spinal cord) PNS (peripheral nervous system) PNS (peripheral nervous system)

Similar presentations


Presentation on theme: "Nervous Tissue. Nervous System CNS (brain and spinal cord) CNS (brain and spinal cord) PNS (peripheral nervous system) PNS (peripheral nervous system)"— Presentation transcript:

1 Nervous Tissue

2 Nervous System CNS (brain and spinal cord) CNS (brain and spinal cord) PNS (peripheral nervous system) PNS (peripheral nervous system)

3 Types of Cells Neurons – structural units Neurons – structural units Supporting cells – protect and myelinate neurons Supporting cells – protect and myelinate neurons

4 Structure of Neurons Cell body – contains nucleus and cytoplasm Cell body – contains nucleus and cytoplasm

5

6 Structure of Neuron Dendrites – receptive regions Dendrites – receptive regions

7

8 Structure of Neuron Axons – nerve impulse generators Axons – nerve impulse generators

9

10 Structure of Neuron Axoplasm – cytoplasm of neuron Axoplasm – cytoplasm of neuron

11

12 Structure of Neuron Axolema – plasma membrane Axolema – plasma membrane

13

14 Structure of Neuron Collaterals – axon branches Collaterals – axon branches

15

16 Structure of Neuron Axon hillock – an enlarged cell body structure, which is the beginning of the axon Axon hillock – an enlarged cell body structure, which is the beginning of the axon

17

18 Structure of Neuron Axon terminals – The axon and its collaterals end divide into fine processes Axon terminals – The axon and its collaterals end divide into fine processes

19

20 Structure of Neuron Synaptic end bulbs – tips of axon terminals that contain the synaptic vessicles Synaptic end bulbs – tips of axon terminals that contain the synaptic vessicles

21

22 Structure of Neuron Synaptic cleft – gap between two neurons Synaptic cleft – gap between two neurons

23 Structure of Neuron Supporting cells wrap themselves around the axons of some neurons like a jelly role Supporting cells wrap themselves around the axons of some neurons like a jelly role

24 Structure of Neuron Myelin sheath – A tight core of plasma membrane material around the axon Myelin sheath – A tight core of plasma membrane material around the axon

25

26

27 Structure of Neuron Neurilemma – The peripheral part of the schwann cell and the exposed plasma membrane Neurilemma – The peripheral part of the schwann cell and the exposed plasma membrane

28

29 Structure of Neuron Nodes of Ranvier – Since the myelin sheath is composed of several schwann cells there are gaps or indentations called nodes of ranier Nodes of Ranvier – Since the myelin sheath is composed of several schwann cells there are gaps or indentations called nodes of ranier

30

31 Classification by Structure 1. Unipolar 2. Bipolar 3. Multipolar

32 Unipolar Have only one process that extends from the cell body Have only one process that extends from the cell body

33

34 Unipolar Conduct impulses toward the CNS Conduct impulses toward the CNS

35 Bipolar Have two processes that extend from the cell body (one axon and one dendrite) Have two processes that extend from the cell body (one axon and one dendrite)

36

37 Bipolar Found in the eye, ear, and olfactory mucosa Found in the eye, ear, and olfactory mucosa

38 Multipolar Have several processes that extend from the cell body (several dendrites and one axon) Have several processes that extend from the cell body (several dendrites and one axon)

39

40 Multipolar Most neurons in CNS and neurons that carry impulses away from the CNS Most neurons in CNS and neurons that carry impulses away from the CNS

41 Classification by Function 1. Sensory 2. Motor

42 Sensory or Afferent Neurons Carry impulses away from sensory receptors in the skin, skeletal muscle, and internal organs. Carry impulses away from sensory receptors in the skin, skeletal muscle, and internal organs.

43 Sensory or Afferent Neurons Most are unipolar Most are unipolar

44 Sensory or Afferent Neurons Cell bodies lie outside the CNS Cell bodies lie outside the CNS

45

46 Motor or Efferent Neurons Carry impulses away from the CNS Carry impulses away from the CNS

47 Motor or Efferent Neurons Most are multipolar Most are multipolar

48 Motor or Efferent Neurons Cell bodies lie within the CNS Cell bodies lie within the CNS

49

50 Neuroglia Supporting cells Supporting cells

51 Neuroglia Half the volume in the CNS Half the volume in the CNS

52 Neuroglia Smaller than neurons Smaller than neurons

53 Neuroglia Five to fifty times more numerous Five to fifty times more numerous

54 Neuroglia Can divide Can divide

55 Neuroglia Do not generate or propogate action potentials Do not generate or propogate action potentials

56 Brain Tumors Derived from glia called gliomas Derived from glia called gliomas Highly malignant Highly malignant Grow fast Grow fast

57 Myelin sheath Some axons are covered by a myelin sheath produced by neuroglia Some axons are covered by a myelin sheath produced by neuroglia

58 Myelin sheath Increases speed of nerve impulse production Increases speed of nerve impulse production

59 Neuroglia Two types of neuroglia produce myelin sheath Two types of neuroglia produce myelin sheath 1. Schwann cells (PNS) 2. Oligodendrocytes (CNS)

60

61 Schwann Cells Helps in regeneration of PNS axons Helps in regeneration of PNS axons

62 Oligodendrocytes Inhibits axon regrowth after injury Inhibits axon regrowth after injury

63 Gray and White Matter In the brain and spinal cord some parts appear gray while other appear white In the brain and spinal cord some parts appear gray while other appear white

64 White Matter Contains the myelinated and unmyelinated axons of neurons Contains the myelinated and unmyelinated axons of neurons

65

66 Gray Matter Contains cell bodies, dendrites, and unmyelinated axons of neurons Contains cell bodies, dendrites, and unmyelinated axons of neurons Also contains neuroglia Also contains neuroglia

67

68 Organization of Nervous System 1. CNS 2. PNS

69 Organization of Nervous System PNS Somatic nervous system Somatic nervous system Autonomic nervous system Autonomic nervous system

70 Somatic Nervous System 1. Sensory neurons convey information from receptors in the body wall, limbs, head, and special senses

71 Somatic Nervous System 2. Motor neurons conduct impulses to skeletal muscles

72 Autonomic Nervous System 1. Sensory Neurons convey information from organs such as the lungs and stomach to the CNS

73 Autonomic Nervous System 2. Motor Neurons conduct impulses from the CNS to smooth muscle, cardiac muscle, and glands

74 Autonomic Nervous System The motor part can be subdivided further into the sympathetic and parasympathetic divisions The motor part can be subdivided further into the sympathetic and parasympathetic divisions

75 Synapses The functional junction between a neuron and an effector or between two neurons. The functional junction between a neuron and an effector or between two neurons.

76 Synapses Presynaptic neuron – The neuron sending the signal Presynaptic neuron – The neuron sending the signal

77 Synapses Postsynaptic neuron – the neuron receiving the message Postsynaptic neuron – the neuron receiving the message

78 Types of Synapses 1. Electrical 2. Chemical

79 Electrical Synapses Action potentials or nerve impulses are conducted directly between adjacent cells through gap junctions. Action potentials or nerve impulses are conducted directly between adjacent cells through gap junctions.

80

81 Electrical Synapses Ions flow from one cell to the next through the connexons thus the action potential is spread from one cell to the next. Ions flow from one cell to the next through the connexons thus the action potential is spread from one cell to the next.

82

83 Chemical Synapses Nerve impulses cannot be conducted across the synaptic cleft Nerve impulses cannot be conducted across the synaptic cleft

84 Chemical Synapses - Summary The presynaptic neuron converts an electrical signal (nerve impulse) into a chemical signal (neurotransmitter release). The presynaptic neuron converts an electrical signal (nerve impulse) into a chemical signal (neurotransmitter release).

85 Chemical Synapses - Summary Then the postsynaptic neuron converts the chemical signal back into an electrical signal (postsynaptic potential). Then the postsynaptic neuron converts the chemical signal back into an electrical signal (postsynaptic potential).

86 Chemical Synapses – 7 Steps 1. An action potential arrives at a synaptic end bulb of a presynaptic neuron

87

88 Chemical Synapses – 7 Steps 2. Voltage-gated calcium channels open and calcium flows into the synaptic end bulb of the presynaptic neuron

89

90 Chemical Synapses – 7 Steps 3. The increase in calcium concentration inside the synaptic end bulb signals the synaptic vessicles to release the neurotransmitters via exocytosis into the synaptic cleft

91

92 Chemical Synapses – 7 Steps 4. The neurotransmitters bind to receptors on the postynaptic neuron

93

94 Chemical Synapses – 7 Steps 5. Once the neurotransmitters bind to the receptors, ions flow across the membrane

95

96 Chemical Synapses – 7 Steps 6. As the ions flow across the membrane the voltage across the membrane changes (postsynaptic potential)

97

98 Chemical Synapses – 7 steps If sodium flows across the membrane it causes depolarization If sodium flows across the membrane it causes depolarization

99 Chemical Synapses – 7 steps If chlorine flows across the membrane it causes hyperpolarization If chlorine flows across the membrane it causes hyperpolarization

100 Chemical Synapses – 7 steps 7. Once a depolarizing postsynaptic potential reaches threshold, an action potential is triggered

101

102 Chemical Synapses Synaptic delay – The length of time between the arrival of the action potential at a presynaptic axon terminal and the membrane potential change on the postsynaptic membrane. Synaptic delay – The length of time between the arrival of the action potential at a presynaptic axon terminal and the membrane potential change on the postsynaptic membrane.

103 Chemical Synapses Due to the synaptic delay electrical synapses are faster than chemical synapses Due to the synaptic delay electrical synapses are faster than chemical synapses

104 Excitatory postsynaptic potential Depolarizing postsynaptic potential caused by the influx of sodium, potassium, and calcium Depolarizing postsynaptic potential caused by the influx of sodium, potassium, and calcium

105 Excitatory postsynaptic potential Once it reaches threshold an action potential is triggered Once it reaches threshold an action potential is triggered

106 Inhibitory postsynaptic potential A hyperpolarizing postsynaptic potential caused by the influx of chlorine or efflux of potassium A hyperpolarizing postsynaptic potential caused by the influx of chlorine or efflux of potassium

107 Inhibitory postsynaptic potential Makes it difficult for the generation of an action potential Makes it difficult for the generation of an action potential

108 Neurotransmitters 1. Small-Molecule Neurotransmitters 2. Neuropeptides

109 Small-Molecule Neurotransmitters 1. Acetylcholine  Released by PNS and CNS neurons  Can act as an excitatory (neuromuscular junction) or inhibitory neuron (heart)

110 Small-Molecule Neurotransmitters 2. Amino acid  CNS  Glutamate has excitatory effects (important for memory)  Gamma aminobutyric (GABA) has inhibitory effects

111 Small-Molecule Neurotransmitters 3. Biogenic amines  Amino acids that are modified and decarboxylated  Can be inhibitory or excitatory depending on the receptor  Norepinephrine, epinephrine, dopamine, and serotonin

112 Small-Molecule Neurotransmitters 3. Biogenic Amines continued  NE and Epinephrine play roles in arousal, dreaming, and regulating mood

113 Small Molecule-Neurotransmitters 3. Biogenic Amines continued  Dopamine are active during emotional responses, addictive behaviors, and pleasurable experiences

114 Small Molecule-Neurotransmitters 3. Biogenic Amines continued  Serotonin involved in sensory reception, temperature regulation, control of mood, appetite, and the induction of sleep

115 Parkinson disease Due to degeneration of neurons that release dopamine Due to degeneration of neurons that release dopamine

116 Schizophrenia Due to accumulation of excess dopamine Due to accumulation of excess dopamine

117 Small-Molecule Neurotransmitters 4. ATP and other Purines  CNS and PNS  Excitatory  Usually released with another neurotransmitter

118 Small-Molecule Neurotransmitters 5. Nitric Oxide  Simple gas  Plays a role in memory and learning  Causes vasodilation

119 Viagra Enhances the effect of NO Enhances the effect of NO

120 Neuropeptides 3-40 amino acids linked by peptide bonds 3-40 amino acids linked by peptide bonds CNS and PNS CNS and PNS Excitatory and Inhibitory actions Excitatory and Inhibitory actions Substance P enhances pain Substance P enhances pain Enkephalins and Endorphins inhibit pain (also morphine and heroin receptors) Enkephalins and Endorphins inhibit pain (also morphine and heroin receptors)


Download ppt "Nervous Tissue. Nervous System CNS (brain and spinal cord) CNS (brain and spinal cord) PNS (peripheral nervous system) PNS (peripheral nervous system)"

Similar presentations


Ads by Google