1. Principles of Communication
Neural and Hormonal
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2. Enodcrine System
Ductless glands
Hormones
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3.
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http://www.cartage.org.lb/en/themes/Sciences/
LifeScience/GeneralBiology/Physiology/Endocrin
eSystem/NervousEndocrine/endocrorgs.gif
4. Neural and Endocrine Control
Release chemical messengers
Communicate with target cells
Maintain stable internal environment
Work together to control digestive and
circulatory systems
6.
Property
Anatomy
Chemical
messenger
Method of travel
by chemical
messenger
Distance traveled
by chemical
messenger
Speed of
Response
Duration of
Action
Specificity
Function
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Nervous
System
Structural
continuity
Endocrine
System
Glands and
targets widely
dispersed
Neurotransmitters Hormones
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Diffusion across
synapse
Distribution by
circulatory system
Short
Long
Rapid –
milliseconds
Brief milliseconds
Close anatomical
proximity
Rapid, precise
responses
Slow – minutes to
hours
Long – minutes to
months
Cell binding
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Activities of long
duration
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7. Nervous
Rapid, precise response
Brief, easily ended, easily altered
Target
Muscles
Glands (exocrine)
Endocrine
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Duration
Organic metabolism
Water balance
Electrolyte balance
Growth and development
Reproduction
8. Nervous Tissue
Neurons
Glia
Oligodendrocytes
Astrocytes
Ependymal cells
Microglia
Schwann cells
Satellite cells
9 - 12. Neurons
Gather and transmit information by:
Responding to stimuli
Producing and sending electrochemical
impulses
Releasing chemical messages
http://www.enchantedlearning.com/subjects/an
atomy/brain/gifs/Neuron.GIF
Cell body
Nucleus
Synthesis of macromolecules
Dendrites
Receive & convey information to cell body
Axon
conduct impulses away from cell body
Special transport systems
Axoplasmic flow
soluble compounds move toward nerve
endings
rhythmic contractions of axon
Axonal transport
large, insoluble compounds
bidirectional
microtubules
anterograde transport
moves materials away from cell
body
retrograde transport
moves materials toward cell body
13. Functional Classification of Neurons
Pseudounipolar:
single process
sensory neurons
Bipolar:
two major processes
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retinal neurons
Multipolar:
many dendrites and a single axon
motor neurons
14. Structural Classification of Neurons
Pseudounipolar:
single process
sensory neurons
Bipolar:
two major processes
retinal neurons
Multipolar:
many dendrites and a single axon
motor neurons
15. Terminology
Myelinated
Unmyelinated
16. Terminology
Ganglia
Nuclei
Nerves
Tracts
17. Nervous System
CNS
Brain
Spinal cord
PNS
Nerves
Ganglia
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18. Nervous System
Somatic
Sensory
Information arising from body surface
Motor
Skeletal muscles
Visceral
Sensory
Information arising viscera
Motor
Cardiac muscle, smooth muscles, glands
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19. Function of Nervous System
Input of sensory information
Integration
Motor output
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20. Synapse
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Specialized junction between a neuron and
another cell
Chemical
Synaptic transmission via neurotransmitters
(NT)
Electrical synapses
Rare in nervous sytem
http://www.mirrorservice.org/sites/home.ubalt.
edu/ntsbarsh/Business-stat/opre/neurons.gif
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21. Electrical Synapse
Ions move through gap junctions
Found in smooth and cardiac muscles,
brain, and glial cells
22. Chemical Synapse
http://universe-review.ca/I10-40-synapse.jpg
26. Resting Potential
27. Electrical Potential
http://regentsprep.org/Regents/physics/phys03
/apotdif/battery.gif
28. Leak Channels
Chemical Gradient
Concentration
High to low
Electrical Gradient
+ and - charges held apart by membrane
Potential difference
32. Definitions
Transmembrane potential
Potential difference
Measured across cell membrane
Expressed in millivolts (mV)
Results from uneven distribution of + and –
ions across membrane
Resting potential
Transmembrane potential under
homeostatic conditions
34. Graded Potential.
35 -38. Change in Membrane Potential
Passive
Leak channels
Widespread
Always open
Active
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Gated channels
Closed at rest
Types
Chemical - widespread
Voltage - axon
(Mechanical)
(Temperature)
States
Closed but able to open
Open (activated)
Closed and not able to open
(inactivated)
39. Definitions
Depolarization
Transmembrane potential moves toward
zero or toward a more positive value
Hyperpolarization
Transmembrane potential moves away from
resting potential and toward a more
negative value
Repolarization
Transmembrane potential moves away from
a positive value and toward the resting
potential
Restoring resting transmembrane potential
41 - 48. Graded Potential
Open sodium channels
Influx of Na+
Depolarization
Open potassium channels
Efflux of K+
Hyperpolarization
Graded Potential
Local changes
Limited spread
Trigger cell functions
Trigger action potential
Types
Postsynaptic
Receptor
End-plate
Pacemaker
49 - 51. Action Potentials
Triggered by graded potentials
All-or-none phenomenon
Threshold
http://www.learner.org/channel/courses/biolog
y/archive/images/1968.html
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53 – 56. Handout
57 - 59. Action Potential
60 - 63. Refractory Period
Absolute
Opening of sodium activation gates to
closing of inactivation gates
Relative
Requires greater than normal stimulus
Sodium gates closed but able to open
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64. Comparison of Potentials
Graded Potentials
Depolarizing or hyperpolarizing
No threshold
Intensity of stimulus determines polarization
Effect on membrane potential decreases
with distance
No refractory period
Most cells
Action Potentials
Depolarizing
Requires depolarization to threshold
All-or-none
Propagates along entire membrane without
change in strength
Refractory period
Excitable membranes of neurons, muscles
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65. Rate of Impulse Conduction
Nerve diameter
Myelination
Saltatory conduction
Multiple sclerosis
Factors that influence excitability
pH
electrolytes
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66. Conduction in an Unmyelinated Axon
Axon hillock reaches threshold
AP occurs
Na+ influx depolarizes adjacent regions to
threshold
new AP
Slow
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67. Conduction in Myelinated Axon
Ions can't cross myelin
APs occur only at nodes of Ranvier
Voltage-gated Na+ channels are present
only at nodes
Fast
Saltatory conduction
68. Propagation of Action Potentials
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Action potential is generated at each new
membrane patch
Continuous - unmyelinated
Transmembrane potential becomes
positive
Local currents established
Can only move in one direction, away
from stimulus
Saltatory- myelinated
Local current skips internodes, jumping
from node to node
69. Synaptic Terminology
Presynaptic
Postsynaptic
Synaptic knob
Synaptic vesicles
Synaptic cleft
Subsynaptic membrane
71-74. Sequence of Events
1. Action potential reaches synaptic knob
2. Local change in potential opens voltage
gated Ca2+ channels
3. Ca2+ enters synaptic knob
4. Release of neurotransmitter from synaptic
vesicles by exocytosis
5. Neurotransmitter diffuses across synaptic
cleft
6. Neurotransmitter binds to receptors on
postsynaptic membrane
7. Binding to receptor triggers opening of
chemically-gated ion channels in subsynaptic
membrane
71. Neurotransmitters
76. Excitatory Synapses
Neurotransmitter binding opens a chemicallygated channel that permits passage of Na+ and
K+
Net movement of cations (Na+) into the cell
Small depolarization
Excitatory postsynaptic potential - EPSP
78. Inhibitory Synapses
Neurotransmitter binding opens a chemicallygated channel that permits passage of Cl- or
K+
Net movement of anions (Cl-) into the cell or
net movement of cations (K+) out of the cell
Small hyperpolarization
Inhibitory postsynaptic potential - IPSP
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80. Synapses
Always excitatory or always inhibitory
Same neurotransmitter is always released
Synaptic delay
Removal of neurotransmitters from cleft
Diffusion
Inactivated by enzymes
Taken up into axon terminal
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83. Grand Synaptic Potential
GSPS
Composite of all ESPSs and ISPSs occurring at
approximately the same time
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84. How Is Threshold Reached?
Temporal Summation
Time
A presynaptic neuron firing repeatedly in a
very short period of time can bring the
postsynaptic membrane to threshold
Amount of neurotransmitter released is
related to frequency of Aps
More NT = more open channels = more ion
movement = greater depolarization
87. How Is Threshold Reached?
Spatial Summation
Different points in space
Multiple presynaptic neurons firing
simultaneously can bring the postsynaptic
membrane to threshold
Amount of neurotransmitter released is
related to number of presynaptic neurons
More NT = more open channels = more ion
movement = greater depolarization
92. Information processing
94.
http://www.mfi.ku.dk/ppaulev/chapter1/images
/n1-6ok.jpg
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