Download Biol&241 11 Part1

PowerPoint® Lecture Slides
prepared by
Barbara Heard,
Atlantic Cape Community
Ninth Edition
College
Human Anatomy & Physiology
CHAPTER
© Annie Leibovitz/Contact Press Images
11
© 2013 Pearson Education, Inc.
Nervous System Organization
Anatomical:
**Central Nervous System
(brain, spinal cord)
**Peripheral Nervous System
(cranial nerves, spinal nerves,
and beyond)
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
Neuroglia
CNS
A**holes
Owe
Everyone Money
Astrocytes Oligocytes Ependymal Microglia
PNS
So
Satellite
Sucky!!
Schwann
are found in
Central Nervous System
contains
Astrocytes
Oligodendrocytes
-Largest
most #s
-Myelinate CNS
axons
-Maintain blood–brain
barrier
-provide
structural
framework
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Ependymal
-Make CSF
-Help with CSF flow
TANGENT!
Importance CSF Flow
•  Research: why is sleep restorative?
Lulu et al., 2013
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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.
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
Neuroglia
are found in
Peripheral Nervous System
contains
Satellite cells
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Schwann cells
Regulate environment
around neurons
myelination of
peripheral axons;
like Astrocytes
injury repair
Neurons
Neurons
•  Large
•  Conduct impulses
•  Extreme longevity (→ 100 years or more)
•  Amitotic—mostly
•  High metabolic rate
•  lots of O2 and C6H12O6
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Figure 11.4a Structure of a motor neuron.
Collect info
Toward cell body
Dendrites
Two processes:
Dendrites
Axon
Cell body Neurotransmitter synth
excite
inhibit
Axon
Conducting region
Ions move across Axolemma
generates nerve impulses
from cell body
=anterograde
-use Kinesin
Impulse
direction
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Axon hillock
Education, Inc.
Axon
terminals
secretion
…of what?
Neurotransmitters
to cell body
=retrograde
-use dynein
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
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Schwann Cells
Myelin Sheath
in PNS
70% fat
one axon, myelinate segments only
many axons, unmyelinated
Nodes: Spaces between Myelin
Sheath
Myelin Sheath in CNS: Oligodendrocytes
CNS Regeneration is NOT Likely
Oligodendrocytes aren’t dedicated = NO Pathway
Astrocytes release growth inhibitors
Arrangement of CNS
Neuroglia make a
pattern
Cell Bodies and
Dendrites =
Gray Matter
Note myelin presence
Neurons Types
Yes, all neurons are shown like this:
but
butthere
thereisisdiversity
diversity
Two ways to categorize:
1. Structure
2. Function
4 Neuron Types (By Structure)
relationships of the dendrites to the cell body
Two ‘tails’
-dendritic
-axon
continuous
no distinction
dendrites from
axons
Brain
>2 dendrite
clusters
Rare
In sense organs
Sensory of PNS
1 meter long!
Most common CNS
can be as long as uni
3 Neuron Types (By Function)
Sensory(afferent)
Sensory(afferent)
SAME principle
Motor(efferent)
NeuroPhysiology:
Three Types of Potentials
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.
Gated Channels
Lets set up the major players
Na+
Na+
Na+
Na+
Na+
++
++
++ +
+
Na+
Na+
Na+ Na+ Na+
Na+
+
Na
Na+ Na+
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+ >> Na+
K+
K+
K+
K+
K+
K+ >> Na+
K+ >> Na+
Resting Membrane Potential
Announcement
•  Physio Ex – Mastering AP Code
•  10 AM class schedule updated
•  Exams
•  My hat?
© 2012 Pearson Education, Inc.
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.
Resting Potential à Action Potential (AP)
•  If permeability change sends charge below -70mV
•  i.e. cell gets more negative
•  = hyperpolarization
© 2012 Pearson Education, Inc.
Figure 11.9b Depolarization and hyperpolarization of the membrane.
How does this happen?
Let the positively charged ions leave
…for a long time
Inhibits an AP
© 2012 Pearson Education, Inc.
Membrane potential (voltage, mV)
Hyperpolarizing stimulus
+50
0
–50
Resting
potential
–70
–100
Hyperpolarization
0
1
2
3
4
Time (ms)
5
6
7
Resting Potential à Action Potential (AP)
•  If change sends charge above -70mV
•  i.e. cell gets more postive
•  = depolarization
© 2012 Pearson Education, Inc.
Figure 11.9a Depolarization and hyperpolarization of the membrane.
How does this happen?
Let the positively charged ions enter
fast
Facilitates an AP
© 2012 Pearson Education, Inc.
Membrane potential (voltage, mV)
Depolarizing stimulus
+50
Inside
positive
0
Inside
negative
Depolarization
–50
–70
–100
Resting
potential
0
1
2
3
4
Time (ms)
5
6
7
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.
Figure 11.10a The spread and decay of a graded potential.
Stimulus
Depolarized region
Plasma
membrane
Stimulus applied
artificial or ECF
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Figure 11.10b The spread and decay of a graded potential.
local currents develop
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Membrane potential (mV)
Figure 11.10c The spread and decay of a graded potential.
Active area
(site of initial
depolarization)
–70
Resting potential
Distance (a few mm)
© 2012 Pearson Education, Inc.
Since localized
they dissipate
quickly
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)
à AP
© 2012 Pearson Education, Inc.
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
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Voltage-gated Na+ channels
Inactivation
gate
Activation
gate
Closed
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Two gates
Opened
Inactivated
So, how do these two interact?
Voltage-gated K+ channels
Closed
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Opened
Just one
gate
The events
Sodium
channel
Potassium
channel
Activation
gates
Inactivation
gate
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1 Resting state
The events
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2 Depolarization
The events
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3 Repolarization
The events
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4 Hyperpolarization
1 Resting state. No
Membrane potential (mV)
ions move through
voltage-gated
channels.
+30
0
Action
potential
Threshold
–55
–70
1
0
© 2013 Pearson Education, Inc.
1
1
2
3
Time (ms)
4
1 Resting state. No
2 Depolarization
Membrane potential (mV)
ions move through
voltage-gated
channels.
is caused by Na+
flowing into the cell.
+30
0
Action
potential
2
Threshold
–55
–70
1
0
© 2013 Pearson Education, Inc.
1
1
2
3
Time (ms)
4
2b
Inactivation/Activation
Na+ inactivation/ K+ activated
1 Resting state. No
2 Depolarization
Membrane potential (mV)
ions move through
voltage-gated
channels.
is caused by Na+
flowing into the cell.
+30
0
Action
potential
2
Threshold
–55
–70
1
0
© 2013 Pearson Education, Inc.
1
1
2
3
Time (ms)
4
1 Resting state. No
2 Depolarization
Membrane potential (mV)
ions move through
voltage-gated
channels.
is caused by Na+
flowing into the cell.
3 Repolarization is
caused by K+ flowing
out of the cell.
+30
3
0
Action
potential
2
Threshold
–55
–70
1
0
© 2013 Pearson Education, Inc.
1
1
2
3
Time (ms)
4
1 Resting state. No
2 Depolarization
Membrane potential (mV)
ions move through
voltage-gated
channels.
is caused by Na+
flowing into the cell.
3 Repolarization is
caused by K+ flowing
out of the cell.
+30
3
4 Hyperpolarization is
0
Threshold
–55
–70
1
0
© 2013 Pearson Education, Inc.
caused by K+ continuing to
leave the cell.
Action
potential
2
1
4
1
2
3
Time (ms)
4
1 Resting state. No
2 Depolarization
Membrane potential (mV)
ions move through
voltage-gated
channels.
is caused by Na+
flowing into the cell.
3 Repolarization is
caused by K+ flowing
out of the cell.
+30
3
0
Action
potential
2
Threshold
–55
–70
1
0
© 2013 Pearson Education, Inc.
1
4
1
2
3
Time (ms)
4
1
Need to re-establish this
Na – K Pumps
•  Repolarization resets electrical conditions,
not ionic conditions
•  Na+/K+ pumps restore ionic conditions
–  3 Na+ out
–  2 K+ in
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Resting Membrane Potential
Refractory Periods
•  So, can a the AP curve be stimulated a
second time to fire a 2nd AP?
•  It depends…
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Refractory Periods
Absolute:
- Na+ channels open
- Can not respond to another
stimulus
- no backwards flow!
- one direction
Relative:
- most Na+ channels @ resting
- 2nd stronger stimulus à AP