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Functions of the Nervous System

Functions of the Nervous System. NERVOUS SYSTEM. CENTRAL NS PERIPHERAL NS. BRAIN SPINAL CORD CRANIAL SPINAL AUTONOMIC. NERVES NERVES NERVES. (12 pairs) (31 pairs). GRAY MATTER WHITE MATTER.

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Functions of the Nervous System

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  1. Functions of the Nervous System

  2. NERVOUS SYSTEM CENTRAL NS PERIPHERAL NS BRAIN SPINAL CORD CRANIAL SPINAL AUTONOMIC NERVES NERVES NERVES (12 pairs) (31 pairs) GRAY MATTER WHITE MATTER SYMPATHETIC PARASYMPATHETIC NERVES NERVES

  3. Section 1 General Function of Neuron and Neuroglia 1. Neuron The structure and function unit of nervous system, including the soma, axon and dendrites

  4. Classification of neuron by function

  5. Function and Classification of Nerve Fiber Nerve Fiber: Axons or Dendrites • Function • Conducting AP • Nerve impulse

  6. Characteristics of Excitement Conduction • Intact • Bidirectional conduction • Not easy to be fatigue • Insulation

  7. The affecting factors of conduction velocity • Diameter of the axon • myelin sheath or no myelin sheath • Thickness of myelin sheath • Temperature

  8. Fiber types Function Avg. fiber diameters (μm) Avg. cond. Velocity (m/s) Aα Primary muscle spindle afferents, motor to skeletal muscle 15 100 (70-120) Aβ Cutaneous touch and pressure afferents 8 50 (30-70) Aγ motor to muscle spindle 5 20 (15-30) Aδ Cutaneous temperature and pain afferents <3 15 (12-30) B Sympathetic preganglionic 3 7 (3-15) C Cutaneous pain afferents sympathetic postganglionic 1 1 (02-2) Erlanger /Gasser classification of nerve fibers

  9. Group Function Avg. fiber diameters (μm) Avg. cond. Velocity (m/s) Ia,Ib Primary muscle spindle afferents and afferents from tendon organs 13 75 (70-120) II Cutaneous mechanoreceptors 9 55 (25-70) III Deep pressure sensors in muscle 3 11(10-25) IV Unmyelinated pain fibers 1 1 Lloyd/Hunt classification of nerve fibers

  10. Axoplasmic transport of nerve fiber Conception::Axoplasm in axon often keep flow, the flow of axoplasm play the role to transport material, it is called axoplasmic transport. Anterograde axoplasmic transport ~ fast ~ slow Retrograde axoplasmic transport

  11. dynein kinesin Fig. Axopasmic transport Fig. The method of horseraidish peroxidase

  12. Trophic action of nerve Conception: Nerve endings often release some trophic factors, continuously to regulate metabolic activity of the tissue that controlled by the nerve, then affecting its the structure, biochemical and physiological changes, this effect is called trophic action of nerve. Mechanism: anxoplasmic transport Phenomenon:

  13. Neurotrophin Conception: a kind of protein molecules that produced by the tissue( such as muscle ) and astrocytes, and is the necessary substance to the neuron survival and growth. Action mode: Neurotrophin enter into the terminal of axon by endocytosis, then reach to cell body by retrograde axoplasmic transport. Significance: to promote protein synthesis in the cell body. so play important roles in supporting neuron growth, development and functional integrity. Types:

  14. Types of Neuroglia Ependymal Cell • CNS • Astrocyte • Microglia • Oligodendrocyte

  15. Characteristics of Neuroglia Quantity Protrusion: Gap junction: Membrane receptor Membrane potential:

  16. Function of Neuroglia 1.Supporting and inducting neuron migration: 2. Repair and. 3: Immune response. 4. Insulation and barrier： 5. Metabolism and nutrition 6. Keeping the stability of potassium concentration 7.Uptaking and secreting the neurotransmitter

  17. Section 2 synaptic transmission 1. Several important synaptic transmission *Classical synaptic transmission *Non-directed synaptic transmission *Electrical synaptic transmission 2. Neurotransmitter and receptor *Neurotransmitter *Receptor *The main transmitter and receptor system

  18. Classical synaptic transmission • Synaptic microstructure • Presynaptic membrane • Voltage-gated Ca2+ channels • Transmitter vesicles • Synaptic cleft • Postsynaptic membrane • Receptors

  19. Classical synaptic transmission • Classification of Synapse • Main: A-D、A-S、A-A • Other: D-D、D-S、D-A、S-D、S-S、S-A

  20. Classical synaptic transmission • Process of synaptic transmission • 1. AP • 2. Ca2+ channel open • 3. Neurotransmitter release • Exocytosis • 4. Neurotransmitter + receptor • 5. Postsynaptic potential (AP) Electric - Chemical - Electric

  21. Synaptic Transmission • AP travels down axon to bouton. • VG Ca2+ channels open. • Ca2+ activates calmodulin, which activates protein kinase. • Protein kinase phosphorylates synapsins. • Synapsins aid in the fusion of synaptic vesicles.

  22. Synaptic Transmission (continued) • NTs are released and diffuse across synaptic cleft. • NT (ligand) binds to specific receptor proteins in postsynaptic membrane. • Chemically-regulated gated ion channels open. • EPSP: depolarization. • IPSP: hyperpolarization. • Neurotransmitter inactivated to end transmission.

  23. Classical synaptic transmission • Postsynaptic Potential • Excitatory postsynaptic potential(EPSP) • Inhibitory postsynaptic potential(IPSP) depolarization hyperpolarization

  24. Excitatory postsynaptic potential (EPSP) • No threshold. • Decreases resting membrane potential. • Closer to threshold. • Graded in magnitude. • Have no refractory period. • Can summate.

  25. Inhibitory postsynaptic potential (IPSP) • No threshold. • Hyperpolarize postsynaptic membrane. • Increase membrane potential. • Can summate. • No refractory period.

  26. Summation of EPSP or IPSP The processes by which the multiple EPSPs (IPSPs) from presynaptic neurons summate over time and space are called temporal and spatial summation

  27. Classical synaptic transmission • Excitation and inhibition of postsynaptic neuron

  28. Classical synaptic transmission • Modulation of synapse • Regulating NT release Ca2+ inflow, AP frequency or amplitude, presynaptic receptor. • Regulating the uptake and inactivation • Regulating the receptors • Synaptic Plasticity

  29. Classical synaptic transmission • The types of synaptic plasticity • Posttetanic potentiation • Habituation • sensitization • long-term potentiation( LTP) • long-term depression(LTD)

  30. Non-directed synaptic transmission The postganglionic autonomic neuron innervate the smooth muscle and cardiac muscle . The multiple branches are beaded with enlargements (varicosity) that are not covered by Schwann cells and contain synaptic vesicles; Fig. : Ending of postganglionic autonomic neurons on smooth muscle

  31. Electrical synaptic transmission • Structure: Gap junctions: • Each gap junction is composed of 12 connexin proteins. • The 12 connexin proteins form a water channel. • the charged small molecules and the local current are allowed through. • Distribution

  32. Electrical synaptic transmission • Functional characteristics: • the charged small molecules and the local current are allowed through the channel. • low resistance • Rapid • Bidirectional transmission • significance:

  33. Chemical Synapse Electrical Synapse

  34. Neurotransmitter Conception: small molecules that synthesized by the neurons, can be released from presynaptic terminals into the synaptic cleft and combined with the receptor of postsynaptic membrane, cause postsynaptic potential.

  35. Conception of neuromodulator: In addition to neurotransmitter, neuron can synthesize and release some chemical substances, they are not directly transmit information between neurons, but can enhance or impair neurotransmitter effects, this kind of substance is called neuromodulator. Neurotransmitter coexistence : Two or more than two (including neuromodulator) have been found in the same neuron, this phenomenon is called neurotransmitters coexistence.

  36. Neurotransmitter Neurotransmitter metabolism: • Synthesis • Storage • Release • Degradation • Reuptake

  37. Receptor Subtype of receptor: each receptor has multiple subtypes Cholinergic receptor：muscarinic receptor (M receptor) and nicotinic receptor (N receptor), N1 and N2 Adrenergic receptor: α (α1, α2) and β (β1, β2, β3)

  38. Receptor Presynaptic receptor: also called autoreceptor Usually, the presynaptic receptor activation can inhibit neurotransmitter release, realize the negative feedback control. noradrenergic receptor noradrenalin

  39. Receptor Mechanism of receptor : • Activation : Binding with the neurotransmitter • Signal transduction pathways • Biological effects(changing postsynaptic neuron activity or making target cells to produce effects Classification of receptor : • Ion channel receptors • G protein-coupled receptor : most

  40. Main neurotransmitter and receptor system Acetylcholine(Ach) : Cholinergic neuron: widely distributed in the CNS Somatic motor nerve fibers All autonomic preganglionic fibers Most parasympathetic postganglionic fibers A few sympathetic postganglionic fibers Cholinergic fiber

  41. The Life Cycle of Acetylcholine Choline acetyltransferase Acetylcholinesterase

  42. Acetylcholine(Ach) receptor: According to pharmacological properties, acetylcholine receptor can be divided into two categories • Muscarinic receptors(M receptor): • M1 to M5, G protein-coupled receptor • Nicotinic receptors(N receptor): • N1 and N2, ion channel receptor

  43. G protein-coupled receptor M receptor

  44. Ion channel receptor N Receptor

  45. Acetylcholine(Ach) receptor:

  46. Noradrenaline(NA) or norepinephrine(NE): • Noradrenergic neuron: In both PNS and CNS • PNS: Smooth muscles, cardiac muscle and glands. • CNS: General behavior. • Adrenergic fibers: most sympathetic postganglionic fibers • Adrenergic receptors: G protein-coupled receptor

  47. Distribution and antagonist of adrenergic receptor in the peripheral nervous system Distribution Antagonist

  48. Mechanism of Action ( receptor)

  49. Dopamine and receptor: • Dopaminergic neuron: • Distributed in the CNS: • Dopaminergic receptors: 1.Nigrostriatal system, participate in the movement regulation. 2.Mesolimbic system,participate in the mental activities. 3.Tuberoinfundibular system, involved in neuroendocrine regulation.

  50. Serotonin and receptor: • Serotonergic neuron : • mainly in the raphe nucleus of the lower brainstem • Receptors: There are 7 types of serotonin receptor: Serotonin1-7. There are 14 subtypes of Serotonin receptors: Histamine and receptor: • Histaminergic neuron : • mainly in the tuberomammillary nucleus of posterior hypothalamus, its fiber projection is very wide, almost reach all parts of CNS. • Receptors: Histamine system has three kinds of receptors, H1,H2, and H3 All receptors are a G- protein-coupled receptor

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