LE 12 -1 Dendrites Dendritic branches Nissl bodies (RER and free ribosomes) Perikaryon Cell body Nucleus Axon Mitochondrion Regions of a neuron Axon hillock Initial segment of axon Axolemma Axon Telodendria Golgi apparatus Neurofilament Nucleus Nucleolus Dendrite PRESYNAPTIC CELL Synaptic terminals See Figure 12 -2 Structural components of a neuron POSTSYNAPTIC CELL
LE 12 -1 a Dendrites Perikaryon Cell body Nucleus Axon Regions of a neuron Telodendria
LE 12 -1 b-1 Dendritic branches Nissl bodies (RER and free ribosomes) Mitochondrion Axon hillock Initial segment of axon Golgi apparatus Neurofilament Nucleus Nucleolus Dendrite PRESYNAPTIC CELL
LE 12 -1 b-2 Axolemma Axon Telodendria Synaptic terminals See Figure 12 -2 POSTSYNAPTIC CELL
LE 12 -2 Telodendrion Endoplasmic reticulum Synaptic knob Mitochondrion Synaptic vesicles Presynaptic membrane Postsynaptic membrane Synaptic cleft
LE 12 -2 -1 Telodendrion Endoplasmic reticulum Synaptic knob Mitochondrion Synaptic vesicles Presynaptic membrane Postsynaptic Synaptic cleft membrane
LE 12 -2 -2
LE 12 -3 Dendrites Initial segment Dendrites Axon Synaptic terminals
LE 12 -3 -2 Dendrites Axon Synaptic terminals
LE 12 -3 -3 Dendrites Initial segment Axon Synaptic terminals
LE 12 -3 -4 Dendrites Axon Synaptic terminals
LE 12 -4 are found in Peripheral Nervous System Central Nervous System Satellite cells Surround neuron cell bodies in ganglia; regulate O 2, CO 2, nutrient, and neurotransmitter levels aound neurons in ganglia contains Schwann cells Surround all axons in PNS; responsible for myelination of peripheral axons; participate in repair process after injury contains Oligodendrocytes Myelinate CNS axons; provide structural framework Astrocytes Maintain blood–brain barrier; provide structural support; regulate ion, nutrient, and dissolvedgas concentrations; absorb and recycle neurotransmitters; form scar tissue after injury Ependymal cells Line ventricles (brain) and central canal (spinal cord); assist in producing, circulating, and monitoring cerebrospinal fluid Microglia Remove cell debris, wastes, and pathogens by phagocytosis
LE 12 -4 -1 are found in Peripheral Nervous System Satellite cells Surround neuron cell bodies in ganglia; regulate O 2, CO 2, nutrient, and neurotransmitter levels aound neurons in ganglia contains Schwann cells Surround all axons in PNS; responsible for myelination of peripheral axons; participate in repair process after injury
LE 12 -4 -2 are found in Central Nervous System contains Oligodendrocytes Myelinate CNS axons; provide structural framework Astrocytes Maintain blood–brain barrier; provide structural support; regulate ion, nutrient, and dissolvedgas concentrations; absorb and recycle neurotransmitters; form scar tissue after injury Ependymal cells Line ventricles (brain) and central canal (spinal cord); assist in producing, circulating, and monitoring cerebrospinal fluid Microglia Remove cell debris, wastes, and pathogens by phagocytosis
LE 12 -5 Ependymal cells Central canal Gray matter CENTRAL CANAL Ependymal cells Gray matter Neurons Microglial cell Myelinated axons Internode Myelin (cut) White matter Axon Nodes Astrocyte Oligodendrocyte Axolemma Unmyelinated axon Basal lamina Capillary
LE 12 -5 a Ependymal cells Central canal Gray matter
LE 12 -5 b-1 CENTRAL CANAL Ependymal cells Gray matter Neurons Microglial cell
LE 12 -5 b-2 Myelinated axons Internode Myelin (cut) White matter Axon Oligodendrocyte Astrocyte Axolemma Nodes Unmyelinated axon Basal lamina Capillary
LE 12 -6 Nucleus Axon hillock Axon Myelinated internode Initial segment (unmyelinated) Nodes Schwann cell nucleus Axon Neurilemma Dendrite Schwann cell nucleus Node Neurilemma Axons Axon Axolemma Myelin covering internode Schwann cell nucleus Axons Neurilemma Axons Myelinated axon Unmyelinated axon
LE 12 -6 a Nucleus Axon hillock Axon Myelinated internode Initial segment (unmyelinated) Nodes Schwann cell nucleus Dendrite Axon Neurilemma Axon Axolemma Myelin covering internode Neurilemma Axons Myelinated axon
LE 12 -6 a-1 Nucleus Axon hillock Axon Myelinated internode Initial segment (unmyelinated) Nodes Schwann cell nucleus Axon Neurilemma Axon Axolemma Myelin covering internode Dendrite
LE 12 -6 a-2 Neurilemma Axons Myelinated axon
LE 12 -6 b Schwann cell nucleus Node Neurilemma Axons Schwann cell nucleus Axons Neurilemma Axons Unmyelinated axon
LE 12 -6 b-1 Schwann cell nucleus Node Neurilemma Axons Schwann cell nucleus Axons
LE 12 -6 b-2 Schwann cell nucleus Axons Neurilemma Axons Unmyelinated axon
LE 12 -7 Fragmentation of axon and myelin occurs in distal stump. Axon Myelin Proximal stump Distal stump Site of injury Schwann cells form cord, grow into cut, and unite stumps. Macrophages engulf degenerating axon and myelin. Schwann cell Macrophage Axon continues to grow into distal stump and is enclosed by Schwann cells. Axon sends buds into network of Schwann cells and then starts growing along cord of Schwann cells.
LE 12 -7_1 Fragmentation of axon and myelin occurs in distal stump. Axon Myelin Proximal stump Distal stump Site of injury
LE 12 -7_2 Schwann cells form cord, grow into cut, and unite stumps. Macrophages engulf degenerating axon and myelin. Schwann cell Macrophage
LE 12 -7_3 Axon sends buds into network of Schwann cells and then starts growing along cord of Schwann cells.
LE 12 -7_4 Axon continues to grow into distal stump and is enclosed by Schwann cells.
LE 12 -8 Presynaptic neuron Postsynaptic cell may produce pti ca cti vit y triggers na Resting stimulus potential produces Action potential Sy Graded potential Information processing
LE 12 -8 -1 Presynaptic neuron may produce Graded potential Resting stimulus potential produces Action potential
LE 12 -8 -2 Postsynaptic cell na pti ca cti vit y triggers Sy Action potential Information processing
LE 12 -9 y KEY ivit Action potential act Sodium ion (Na+) tic Graded potential Sy nap Resting potential Potassium ion (K+) Information processing Chloride ion (Cl–) EXTRACELLULAR FLUID K+ leak channel 2 Sodium– potassium exchange pump Plasma membrane 2 2 Protein CYTOSOL Na+ leak 3 channel 3 3
LE 12 -9 -1 KEY Sodium ion (Na+) Chloride ion (Cl–) Potassium ion (K+) EXTRACELLULAR FLUID K+ leak channel 2 Sodium– potassium exchange pump Plasma membrane 2 2 Protein CYTOSOL Na+ leak 3 channel 3 3
LE 12 -10 EXTRACELLULAR FLUID Potassium chemical electrochemical – 70 m. V gradient (net) EXTRACELLULAR FLUID Sodium chemical – 70 m. V gradient Sodium electrical gradient Sodium electrochemical gradient (net) Na+ K+ K+ CYTOSOL At the normal resting potential, an electrical gradient opposes the chemical gradient for potassium ions (K+). The net electrochemical gradient tends to force potassium ions out of the cell. – 90 m. V Potassium chemical electrical gradient At the normal resting potential, chemical and electrical gradients combine to drive sodium ions (Na+) into the cell. +66 m. V K+ Sodium chemical gradient Sodium electrical gradient Na+ K+ CYTOSOL If the plasma membrane were freely permeable to potassium ions, the outflow of K+ would continue until the equilibrium potential was reached. CYTOSOL If the plasma membrane were freely permeable to sodium ions, the influx of Na+ would continue until the equilibrium potential was reached. The chemical and electrical gradients would then be equal and opposite in direction, and no net movement of Na+ would occur across the membrane.
LE 12 -10 ab EXTRACELLULAR FLUID Potassium chemical electrochemical gradient – 70 m. V gradient (net) gradient K+ K+ CYTOSOL At the normal resting potential, an electrical gradient opposes the chemical gradient for potassium ions (K+). The net electrochemical gradient tends to force potassium ions out of the cell. – 90 m. V Potassium chemical electrical gradient K+ CYTOSOL K+ If the plasma membrane were freely permeable to potassium ions, the outflow of K+ would continue until the equilibrium potential was reached.
LE 12 -10 cd EXTRACELLULAR FLUID Sodium chemical – 70 m. V gradient Sodium electrical gradient Sodium electrochemical gradient (net) Na+ CYTOSOL At the normal resting potential, chemical and electrical gradients combine to drive sodium ions (Na+) into the cell. +66 m. V Sodium chemical gradient Sodium electrical gradient Na+ CYTOSOL If the plasma membrane were freely permeable to sodium ions, the influx of Na+ would continue until the equilibrium potential was reached. The chemical and electrical gradients would then be equal and opposite in direction, and no net movement of Na+ would occur across the membrane.
LE 12 -11 Chemically gated channel Voltage-gated channel – 70 m. V Resting state Channel closed Mechanically gated channel Activation gate Inactivation gate Channel closed Presence of ACh Channel closed Binding site Gated channel – 60 m. V Channel open Applied pressure Channel open +30 m. V Channel open Channel inactivated Pressure removed Channel closed
LE 12 -11 a Chemically gated channel Resting state Presence of ACh Channel closed Channel open Binding site Gated channel
LE 12 -11 b Voltage-gated channel – 70 m. V Channel closed – 60 m. V Channel open +30 m. V Channel inactivated Activation gate Inactivation gate
LE 12 -11 c Mechanically gated channel Channel closed Applied pressure Channel open Pressure removed Channel closed
Sy na pti Resting potential Initial segment cti vit Action potential ca Graded potential y LE 12 -12 Information processing Resting membrane with closed chemically gated sodium ion channels – 70 m. V Stimulus applied here EXTRACELLULAR FLUID CYTOSOL Membrane exposed to chemical that opens the sodium ion channels – 65 m. V Spread of sodium ions inside plasma membrane produces a local current that depolarizes adjacent portions of the plasma membrane Local current – 60 m. V – 65 m. V Local current – 70 m. V
LE 12 -12 -1 Resting membrane with closed chemically gated sodium ion channels – 70 m. V EXTRACELLULAR FLUID CYTOSOL
LE 12 -12 -2_1 Membrane exposed to chemical that opens the sodium ion channels – 65 m. V
LE 12 -12 -3_2 Spread of sodium ions inside plasma membrane produces a local current that depolarizes adjacent portions of the plasma membrane Local current – 60 m. V – 65 m. V Local current – 70 m. V
LE 12 -13 ab – 60 Transmembrane potential (m. V) – 70 Chemical stimulus Chemical removed stimulus applied Repolarization Resting Depolarization – 80 Chemical stimulus applied removed potential Hyperpolarization Time Return to resting potential
LE 12 -14 Axon hillock ivit Action potential Sy nap tic Resting potential act Graded potential y Initial segment Activation of sodium channels and rapid depolarization Depolarization to threshold – 70 m. V Information processing +10 m. V – 60 m. V Local current The return to normal permeability – 90 m. V Inactivation of sodium channels and activation of potassium channels +30 m. V
LE 12 -14 -1 – 70 m. V
LE 12 -14 -2_1 Depolarization to threshold – 60 m. V Local current
LE 12 -14 -3_2 Activation of sodium channels and rapid depolarization +10 m. V
LE 12 -14 -4_3 Inactivation of sodium channels and activation of potassium channels +30 m. V
LE 12 -14 -5_4 The return to normal permeability – 90 m. V
LE 12 -15 Initial Axon segment hillock 1 2 3 As an action potential develops in the initial segment, the transmembrane potential depolarizes to +30 m. V Action potential EXTRACELLULAR FLUID +30 m. V A local current depolarizes the adjacent portion of the membrane to threshold Graded depolarization – 60 m. V – 70 m. V Na+ 1 2 3 Plasma membrane CYTOSOL A local current depolarizes the adjacent portion of the membrane to threshold, and the cycle is repeated – 60 m. V Loca l current An action potential develops at this location, and the initial segment enters the refractory period Repolarization (refractory) +30 m. V Na+ Loca l current – 70 m. V
LE 12 -15_1 As an action potential develops in the initial segment, the transmembrane potential depolarizes to +30 m. V Action potential EXTRACELLULAR FLUID +30 m. V – 70 m. V Na+ 1 2 Plasma membrane 3 CYTOSOL
LE 12 -15_2 A local current depolarizes the adjacent portion of the membrane to threshold Graded depolarization – 60 m. V Local current – 70 m. V
LE 12 -15_3 An action potential develops at this location, and the initial segment enters the refractory period Repolarization (refractory) +30 m. V Na+ – 70 m. V
LE 12 -15_4 A local current depolarizes the adjacent portion of the membrane to threshold, and the cycle is repeated – 60 m. V Loca l current
LE 12 -16 Initial segment Node 2 1 Action potential at initial segment EXTRACELLULAR FLUID +30 m. V – 70 m. V Na+ Myelinated Internode – 70 m. V Myelinated Internode 1 Myelinated Internode 2 Plasma membrane CYTOSOL Depolarization to threshold at node 1 – 60 m. V – 70 m. V Local current Action potential at node 1 Repolarization (refractory) +30 m. V – 70 m. V Na+ Depolarization to threshold at node 2 – 60 m. V 1 2 Local current
LE 12 -16 -1 Initial segment Node 1 2
LE 12 -16 -2_1 Action potential at initial segment Depolarization to threshold at node 1 EXTRACELLULAR FLUID +30 m. V – 70 m. V Na+ Myelinated Internode 1 Plasma membrane Myelinated Internode 2 Myelinated Internode CYTOSOL
LE 12 -16 -3_2 Depolarization to threshold at node 1 – 60 m. V Local current – 70 m. V
LE 12 -16 -4_3 Action potential at node 1 Repolarization (refractory) +30 m. V Na+ – 70 m. V
LE 12 -16 -5_4 Depolarization to threshold at node 2 – 60 m. V 1 2 Local current
LE 12 -17 ER Synaptic knob ivit act Action potential pti c Resting potential na Synaptic vesicles Graded potential Sy EXTRACELLULAR FLUID Action potential PRESYNAPTIC NEURON y An action potential arrives and depolarizes the synaptic knob Action potential at initial segment Initial segment ACh. E POSTSYNAPTIC NEURON CYTOSOL Extracellular Ca 2+ enters the synaptic cleft triggering the exocytosis of ACh Ca 2+ Synaptic cleft Ca 2+ Chemically regulated sodium channels ACh binds to receptors and depolarizes the postsynaptic membrane Initiation of action potential if threshold is reached Receptor Na+ Na+ Na+ Action potential at node 1 ACh is removed by ACh. E (acetylcholinesterase) Propagation of action potential (if generated) Information processing
LE 12 -17_1 An action potential arrives and depolarizes the synaptic knob PRESYNAPTIC NEURON Synaptic vesicles EXTRACELLULAR FLUID Action potential ER Synaptic knob Initial segment ACh. E POSTSYNAPTIC NEURON CYTOSOL
LE 12 -17_2 Extracellular Ca 2+ enters the synaptic cleft triggering the exocytosis of ACh Ca 2+ Synaptic cleft Ca 2+ Chemically regulated sodium channels
LE 12 -17_3 ACh binds to receptors and depolarizes the postsynaptic membrane Initiation of action potential if threshold is reached Receptor Na+ Na+ Na+
LE 12 -17_4 ACh is removed by ACh. E (acetylcholinesterase) Propagation of action potential (if generated) Action potential at node 1
LE 12 -18 Examples: ACh, glutamate, aspartate Direct effects ACh Indirect effects via intracellular enzymes Binding site Nitric oxide Opens ion channels Gated channel Indirect effects via G proteins Examples: E, NE, dopamine, histamine, GABA Neurotransmitter Receptor G protein (inactive) G protein (active) ATP Opens ion channels Examples: Nitric oxide, carbon monoxide Adenylate cyclase c. AMP Activates enzymes that change cell metabolism and activity Production of secondary messengers Changes in cell metabolism and activity Activation of enzymes
LE 12 -18 a Examples: ACh, glutamate, aspartate Direct effects Binding site ACh Gated channel
LE 12 -18 b Examples: E, NE, dopamine, histamine, GABA Indirect effects via G proteins Neurotransmitter Receptor G protein (active) G protein (inactive) ATP Opens ion channels Adenylate cyclase c. AMP Activates enzymes that change cell metabolism and activity
LE 12 -18 c Indirect effects via intracellular enzymes Examples: Nitric oxide, carbon monoxide Nitric oxide Opens ion channels Production of secondary messengers Changes in cell metabolism and activity Activation of enzymes
Action potential Sy nap tic Resting potential act Graded potential ivit y LE 12 -19 FIRST STIMULUS Initial segment SECOND STIMULUS Threshold reached ACTION POTENTIAL PROPAGATION Information processing TWO SIMULTANEOUS STIMULI Threshold reached ACTION POTENTIAL PROPAGATION
LE 12 -19 a FIRST STIMULUS Initial segment SECOND STIMULUS Threshold reached ACTION POTENTIAL PROPAGATION
LE 12 -19 b TWO SIMULTANEOUS STIMULI Threshold reached ACTION POTENTIAL PROPAGATION
LE 12 -20 Time 2: Hyperpolarizing stimulus applied EPSP – 70 m. V (resting potential) Time 1: Depolarizing stimulus applied Resting potential Stimulus removed IPSP Time 3: Hyperpolarizing stimulus applied Resting potential Time 3: Depolarizing stimulus applied Stimulus removed Time Stimuli removed
LE 12 -21 Action potential arrives GABA release Inactivation of calcium channels Action potential arrives Serotonin release Activation of calcium channels Ca 2+ 2. More calcium enters 2. Less calcium enters 1. Action potential arrives 3. Less neurotransmitter released Presynaptic inhibition 4. Reduced effect on postsynaptic membrane 1. Action potential arrives 3. More neurotransmitter released Presynaptic facilitation 4. Increased effect on postsynaptic membrane
LE 12 -21 a Action potential arrives GABA release Inactivation of calcium channels Ca 2+ 2. Less calcium enters 1. Action potential arrives 3. Less neurotransmitter released Presynaptic inhibition 4. Reduced effect on postsynaptic membrane
LE 12 -21 b Action potential arrives Serotonin release Activation of calcium channels Ca 2+ 2. More calcium enters 1. Action potential arrives 3. More neurotransmitter released Presynaptic facilitation 4. Increased effect on postsynaptic membrane
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12_EditableImages.ppt Lab Nervous tissue