Transcript membrane potential

Research and share
Research and share
1. Diagram and describe the path from
visual sensory input to motor response
Research and share
1. Diagram and describe the path from
visual sensory input to motor response
2. Diagram and describe the specific
roles of ions in an action potential
Research and share
1. Diagram and describe the path from
visual sensory input to motor response
2. Diagram and describe the specific
roles of ions in an action potential
3. Diagram and describe how synapses
work, both in combination and in
isolation
Research: utilize and underline vocab
1. Diagram and describe the path from
visual sensory input to motor response
2. Diagram and describe the specific roles of
ions in an action potential
3. Diagram and describe how synapses
work, both in combination and in isolation
4. Why do people enjoy drugs? Pick one and
discuss specifically (see Mouse Party)
5. Why does some pain hurts more than
others (review action potentials)
More:
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Average number of neurons in the human brain= 100 billion
Average number of neurons in an octopus brain= 300 billion
Velocity of a signal transmitted through a neuron= 1.2 to 250 mi./hr.
After age 30, the brain begins to lose about 50,000 neurons per day shrinking the brain ¼ % each year.
The brain can stay alive for 4 to 6 minutes without oxygen. After that
cells begin die.
Your brain is about 2% of your total body weight but uses 20% of
your body's energy
Einstein’s brain weighed 1,230 grams (2.71 lbs), significantly less
then the human average of 1,400g (3 lbs).
More electrical impulses are generated in one day by a single human
brain than by all the telephones in the world.
The energy used by the brain is enough to light a 25 watt bulb.
70,000 is the number of thoughts that it is estimated the human
brain produces on an average day.
LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 48
Neurons, Synapses, and Signaling
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.
NEURON STRUCTURE AND ORGANIZATION
Dendrites
Stimulus
Axon hillock
Nucleus
Cell
body
Presynaptic
cell
Axon
Signal
direction
Synapse
Neurotransmitter
Synaptic terminals
Postsynaptic cell
Synaptic
terminals
Figure 48.5
Dendrites
Axon
Cell
body
Portion
of axon
Sensory neuron
Interneurons
Motor neuron
Venomous cone snail
Figure 48.2
Nerves
with giant axons
Ganglia
Brain
Arm
Eye
Nerve
Mantle
Brain power does not have to be
dedicated to cognitive
functioning:
e.g. cephalopods
3 TYPES OF NEURONS:
• Sensors detect external stimuli and internal
conditions and transmit information along
sensory neurons
• Sensory information is sent to the brain or
ganglia, where interneurons integrate the
information
• Motor output leaves the brain or ganglia via
motor neurons, which trigger muscle or gland
activity
© 2011 Pearson Education, Inc.
Figure 48.3
Sensory input
Integration
Sensor
Motor output
Effector
Peripheral nervous
system (PNS)
Central nervous
system (CNS)
Concept 48.2: Ion pumps and ion channels
establish the resting potential of a neuron
• Every cell has a voltage (difference in electrical
charge) across its plasma membrane called a
membrane potential
• The resting potential is the membrane potential
of a neuron not sending signals
• Changes in membrane potential act as signals,
transmitting and processing information
© 2011 Pearson Education, Inc.
Formation of the Resting Potential
• In a mammalian neuron at resting potential, the
concentration of K+ is highest inside the cell,
while the concentration of Na+ is highest outside
the cell
• Sodium-potassium pumps use the energy of
ATP to maintain these K+ and Na+ gradients
across the plasma membrane
• These concentration gradients represent
chemical potential energy
© 2011 Pearson Education, Inc.
• The opening of ion channels in the plasma
membrane converts chemical potential to electrical
potential
• A neuron at resting potential contains many open
K+ channels and fewer open Na+ channels; K+
diffuses out of the cell
• The resulting buildup of negative charge within the
neuron is the major source of membrane potential
© 2011 Pearson Education, Inc.
Animation: Resting Potential
Right-click slide / select “Play”
© 2011 Pearson Education, Inc.
Table 48.1
Bioflix
• How neurons work
Figure 48.7
Key
Na
K
Sodiumpotassium
pump
OUTSIDE
OF CELL
Potassium
channel
Sodium
channel
INSIDE
OF CELL
Figure 48.8
Inner
chamber
 90 mV
Outer
chamber
140 mM
KCl
5 mM
KCl
Inner
chamber
15 mM
NaCl
 62 mV
Outer
chamber
150 mM
NaCl
Cl
K
Potassium
channel
Cl
Artificial
membrane
(a) Membrane selectively permeable
to K
EK  62 mV
 90 mV
Na
Sodium
channel
(b) Membrane selectively permeable
to Na
ENa  62 mV
 62 mV
Figure 48.10
Stimulus
50
50 Threshold
Resting
potential
Hyperpolarizations
0 1 2 3 4 5
Time (msec)
(a) Graded hyperpolarizations
produced by two stimuli that
increase membrane permeability
to K
50
0
50 Threshold
100
Resting
potential
Depolarizations
0 1 2 3 4 5
Time (msec)
(b) Graded hyperpolarizations
produced by two stimuli that
increase membrane permeability
to Na
Membrane potential (mV)
0
Membrane potential (mV)
Membrane potential (mV)
50
100
Strong depolarizing stimulus
Stimulus
Action
potential
0
50 Threshold
Resting
potential
100
0 1 2 3 4 5 6
Time (msec)
(c) Action potential triggered by a
depolarization that reaches the
threshold
Generation of Action Potentials: A Closer
Look
• An action potential can be considered as a
series of stages
• At resting potential
1. Most voltage-gated sodium (Na+) channels are
closed; most of the voltage-gated potassium
(K+) channels are also closed
© 2011 Pearson Education, Inc.
Figure 48.11-1
Key
Na
K
Membrane potential
(mV)
50
0
Threshold
50
100
OUTSIDE OF CELL
INSIDE OF CELL
Inactivation loop
1 Resting state
Sodium
channel
Potassium
channel
1
Resting potential
Time
• When an action potential is generated
2. Voltage-gated Na+ channels open first and Na+
flows into the cell
3. During the rising phase, the threshold is
crossed, and the membrane potential increases
4. During the falling phase, voltage-gated Na+
channels become inactivated; voltage-gated K+
channels open, and K+ flows out of the cell
© 2011 Pearson Education, Inc.
Figure 48.11-2
Key
Na
K
Membrane potential
(mV)
50
0
50
2 Depolarization
OUTSIDE OF CELL
INSIDE OF CELL
Inactivation loop
1 Resting state
100
Sodium
channel
Potassium
channel
Threshold
2
1
Resting potential
Time
Figure 48.11-3
Key
Na
K
50
Membrane potential
(mV)
3 Rising phase of the action potential
Action
potential
50
2 Depolarization
OUTSIDE OF CELL
INSIDE OF CELL
Inactivation loop
1 Resting state
100
Sodium
channel
Potassium
channel
3
0
Threshold
2
1
Resting potential
Time
Figure 48.11-4
Key
Na
K
Membrane potential
(mV)
Action
potential
OUTSIDE OF CELL
INSIDE OF CELL
Inactivation loop
1 Resting state
100
Sodium
channel
Potassium
channel
3
0
50
2 Depolarization
4 Falling phase of the action potential
50
3 Rising phase of the action potential
Threshold
2
4
1
Resting potential
Time
5. During the undershoot, membrane
permeability to K+ is at first higher than at rest,
then voltage-gated K+ channels close and
resting potential is restored
© 2011 Pearson Education, Inc.
Figure 48.11-5
Key
Na
K
Membrane potential
(mV)
Action
potential
OUTSIDE OF CELL
100
Sodium
channel
3
0
50
2 Depolarization
4 Falling phase of the action potential
50
3 Rising phase of the action potential
Threshold
2
1
4
5
Resting potential
Time
Potassium
channel
INSIDE OF CELL
Inactivation loop
1 Resting state
5 Undershoot
1
BioFlix: How Neurons Work
© 2011 Pearson Education, Inc.
Animation: Action Potential
Right-click slide / select “Play”
© 2011 Pearson Education, Inc.
Figure 48.12-1
Axon
Action
potential
Plasma
membrane
1
Na
Cytosol
Figure 48.12-2
Axon
Plasma
membrane
Action
potential
1
Na
K
2
Cytosol
Action
potential
Na
K
Figure 48.12-3
Axon
Plasma
membrane
Action
potential
1
Na
K
2
Cytosol
Action
potential
Na
K
K
3
Action
potential
Na
K
Evolutionary Adaptation of Axon Structure
• The speed of an action potential increases with
the axon’s diameter
• In vertebrates, axons are insulated by a myelin
sheath, which causes an action potential’s
speed to increase
• Myelin sheaths are made by glia—
oligodendrocytes in the CNS and Schwann
cells in the PNS
© 2011 Pearson Education, Inc.
Figure 48.13
Node of Ranvier
Layers of myelin
Axon
Schwann
cell
Axon
Myelin sheath
Nodes of
Ranvier
Schwann
cell
Nucleus of
Schwann cell
0.1 m
Saltatory
conduction
Schwann cell
Depolarized region
(node of Ranvier)
Cell body
Myelin
sheath
Axon
Animation: Synapse
Right-click slide / select “Play”
© 2011 Pearson Education, Inc.
Bioflix #2
• How synapses work
Figure 48.15
Presynaptic
cell
Postsynaptic cell
Axon
Synaptic vesicle
containing
neurotransmitter
1
Postsynaptic
membrane
Synaptic
cleft
Presynaptic
membrane
3
K
Ca2 2
Voltage-gated
Ca2 channel
Ligand-gated
ion channels
4
Na
• Postsynaptic potentials fall into two categories
– Excitatory postsynaptic potentials (EPSPs)
are depolarizations that bring the membrane
potential toward threshold
– Inhibitory postsynaptic potentials (IPSPs) are
hyperpolarizations that move the membrane
potential farther from threshold
© 2011 Pearson Education, Inc.
• After release, the neurotransmitter
– May diffuse out of the synaptic cleft
– May be taken up by surrounding cells
– May be degraded by enzymes
© 2011 Pearson Education, Inc.
Figure 48.16
Synaptic
terminals
of presynaptic
neurons
5 m
Postsynaptic
neuron
Summation of postsynaptic potentials
Terminal branch
of presynaptic
neuron
E1
E2
E1
E2
Postsynaptic
neuron
Membrane potential (mV)
E1
E1
E2
E2
Axon
hillock
I
I
I
I
0
Action
potential
Threshold of axon of
postsynaptic neuron
Action
potential
Resting
potential
70
E1
E1
(a) Subthreshold, no
summation
E1 E1
(b) Temporal summation
E1  E2
(c) Spatial summation
E1
I
E1  I
(d) Spatial summation
of EPSP and IPSP
• If two EPSPs are produced in rapid succession,
an effect called temporal summation occurs
© 2011 Pearson Education, Inc.
Table 48.2
How sharp is your brain?
Messing with your perception
Getting to the bottom of it…
• Why are we so easily duped by optical
illusions?
Review
• Bozeman: Nervous System
• Bozeman: the brain (less important)
• Crash Course: the Nervous System
LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 49
Nervous Systems
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.
Figure 49.2
Radial
nerve
Nerve net
Nerve
ring
Eyespot
Brain
Nerve
cords
Transverse
nerve
Brain
Ventral
nerve cord
Segmental
ganglia
(a) Hydra (cnidarian)
(b) Sea star
(echinoderm)
(c) Planarian
(flatworm)
(d) Leech (annelid)
Brain
Brain
Ventral
nerve cord
Segmental
ganglia
(e) Insect (arthropod)
Ganglia
Anterior
nerve ring
Brain
Longitudinal
nerve cords
Ganglia
(f) Chiton (mollusc)
(g) Squid (mollusc)
Spinal
cord
(dorsal
nerve
cord)
(h) Salamander
(vertebrate)
Sensory
ganglia
Figure 49.3
Quadriceps
muscle
Cell body of
sensory neuron in
dorsal root
ganglion
Gray
matter
White
matter
Hamstring
muscle
Spinal cord
(cross section)
Sensory neuron
Motor neuron
Interneuron
Figure 49.4
Central nervous
system (CNS)
Brain
Peripheral nervous
system (PNS)
Cranial nerves
Spinal cord
Ganglia outside
CNS
Spinal nerves
Figure 49.5
Gray matter
White
matter
Ventricles
• The central canal of the spinal cord and the
ventricles of the brain are hollow and filled with
cerebrospinal fluid
• The cerebrospinal fluid is filtered from blood and
functions to cushion the brain and spinal cord as
well as to provide nutrients and remove wastes
© 2011 Pearson Education, Inc.
Glia
• Glia have numerous functions to nourish,
support, and regulate neurons
– Embryonic radial glia form tracks along which
newly formed neurons migrate
– Astrocytes induce cells lining capillaries in the
CNS to form tight junctions, resulting in a
blood-brain barrier and restricting the entry of
most substances into the brain
© 2011 Pearson Education, Inc.
Figure 49.6
CNS
PNS
Neuron
VENTRICLE
Cilia
Astrocyte
Oligodendrocyte
Schwann cell
Microglial cell
Ependymal cell
50 m
Capillary
LM
Figure 49.7
Central Nervous
System
(information processing)
Peripheral Nervous
System
Efferent neurons
Afferent neurons
Sensory
receptors
Autonomic
nervous system
Motor
system
Control of
skeletal muscle
Internal
and external
stimuli
Sympathetic Parasympathetic Enteric
division
division
division
Control of smooth muscles,
cardiac muscles, glands
Figure 49.8
Sympathetic division
Parasympathetic division
Action on target organs:
Action on target organs:
Constricts pupil
of eye
Dilates pupil of eye
Stimulates salivary
gland secretion
Inhibits salivary
gland secretion
Constricts
bronchi in lungs
Cervical
Sympathetic
ganglia
Relaxes bronchi
in lungs
Slows heart
Accelerates heart
Stimulates activity
of stomach and
intestines
Inhibits activity of
stomach and intestines
Thoracic
Stimulates activity
of pancreas
Inhibits activity
of pancreas
Stimulates
gallbladder
Stimulates glucose
release from liver;
inhibits gallbladder
Lumbar
Stimulates
adrenal medulla
Promotes emptying
of bladder
Promotes erection
of genitalia
Inhibits emptying
of bladder
Sacral
Synapse
Promotes ejaculation
and vaginal contractions
Figure 49.9a
Figure 49.9b
Brain structures in child and adult
Embryonic brain regions
Telencephalon
Cerebrum (includes cerebral cortex, white
matter, basal nuclei)
Diencephalon
Diencephalon (thalamus, hypothalamus,
epithalamus)
Forebrain
Midbrain
Mesencephalon
Midbrain (part of brainstem)
Metencephalon
Pons (part of brainstem), cerebellum
Myelencephalon
Medulla oblongata (part of brainstem)
Hindbrain
Cerebrum
Mesencephalon
Midbrain
Hindbrain
Metencephalon
Diencephalon
Diencephalon
Midbrain
Myelencephalon
Pons
Medulla
oblongata
Spinal
cord
Forebrain
Telencephalon
Embryo at 1 month
Embryo at 5 weeks
Cerebellum
Spinal cord
Child
Figure 49.9c
Left cerebral
hemisphere
Right cerebral
hemisphere
Cerebral cortex
Corpus callosum
Cerebrum
Basal nuclei
Cerebellum
Adult brain viewed from the rear
Figure 49.9d
Diencephalon
Thalamus
Pineal gland
Hypothalamus
Brainstem
Midbrain
Pituitary gland
Pons
Medulla
oblongata
Spinal cord
THE LIMBIC SYSTEM
Thalamus
Hypothalamus
emotion requires interaction between the
limbic system and sensory areas of the
cerebrum
The structure most important to the storage
of emotion in the memory is the
amygdala, a mass of nuclei
Olfactory
bulb
Amygdala
Hippocampus
Concept 49.3: The cerebral cortex controls voluntary movement and cognitive functions
Frontal lobe
Motor cortex
(control of
skeletal muscles)
Somatosensory cortex
(sense of touch)
Parietal lobe
Prefrontal cortex
(decision making,
planning)
Sensory association
cortex (integration of
sensory information)
Visual association
cortex (combining
images and object
recognition)
Broca’s area
(forming speech)
Temporal lobe
Occipital lobe
Auditory cortex (hearing)
Wernicke’s area
(comprehending language)
Cerebellum
Visual cortex
(processing visual
stimuli and pattern
recognition)
What are the differences?
How do we know what parts of the
brain control which functions?
• Effect of injury
• Electrical stimulation
– Also provides treatments for certain
disorders
• Functional Magnetic Resonance
Imaging (fMRI)
Figure 49.16
Max
Hearing
words
Seeing
words
Min
Speaking
words
Generating
words
Lateralization of Cortical Function
© 2011 Pearson Education, Inc.
Lateralization of Cortical Function
© 2011 Pearson Education, Inc.
Videos that answer questions
• Could you survive with half a brain?
• What would happen if you severed your
corpus collosum?
Body part representation in the primary motor and primary somatosensory cortices.
Frontal lobe
Parietal lobe
Jaw
Tongue
Leg
Hip
Trunk
Neck
Head
Knee
Hip
Genitalia
Toes
Tongue
Pharynx
Primary
motor cortex
Abdominal
organs
Primary
somatosensory
cortex
Frontal Lobe Function –
characterizes the “self”
• Frontal lobe damage may impair decision
making and emotional responses but leave
intellect and memory intact
• The frontal lobes have a substantial effect on
“executive functions”
• How do we know what the frontal lobe does?
© 2011 Pearson Education, Inc.
Phinaes Gage
Neural Plasticity
• Neural plasticity describes the ability of the
nervous system to be modified after birth
• Changes can strengthen or weaken signaling at
a synapse
© 2011 Pearson Education, Inc.
Figure 49.19
N1
N1
N2
N2
(a) Synapses are strengthened or weakened in response to
activity.
(b) If two synapses are often active at the same time, the
strength of the postsynaptic response may increase at
both synapses.
Memory and Learning
• The formation of memories is an example of
neural plasticity
• Short-term memory is accessed via the
hippocampus; also plays a role in forming longterm memory, which is stored in the cerebral
cortex
– See story of HM
• Some consolidation of memory is thought to
occur during sleep
© 2011 Pearson Education, Inc.
Figure 49.20
Ca2
PRESYNAPTIC
NEURON
Na
Mg2
Glutamate
NMDA receptor (open)
NMDA
receptor
(closed)
Stored
AMPA
receptor
POSTSYNAPTIC
NEURON
(a) Synapse prior to long-term potentiation (LTP)
1
2
3
(b) Establishing LTP
3
1
2
Depolarization
(c) Synapse exhibiting LTP
4
Action
potential
Stem Cells in the Brain
• The adult human brain contains neural stem
cells
• In mice, stem cells in the brain can give rise to
neurons that mature and become incorporated
into the adult nervous system
• Such neurons play an essential role in learning
and memory
© 2011 Pearson Education, Inc.
Newly
born
neurons
in the
hippocampus
of an
adult
mouse
NEUROLOGICAL DISORDERS
Schizophrenia
• About 1% of the world’s population suffers from
schizophrenia
• Schizophrenia is characterized by hallucinations,
delusions, and other symptoms
– TOO MUCH STIMULATION OF CERTAIN
NEURONS, CONFUSING PATHWAYS
• Available treatments focus on brain pathways
that use dopamine as a neurotransmitter
© 2011 Pearson Education, Inc.
Figure 49.22
Genes shared with relatives of
person with schizophrenia
12.5% (3rd-degree relative)
25% (2nd-degree relative)
50% (1st-degree relative)
100%
40
30
20
Child
Fraternal
twin
Identical
twin
Full sibling
Parent
Half sibling
0
Uncle/aunt
Nephew/
niece
Grandchild
10
Individual,
general
population
First cousin
Risk of developing schizophrenia (%)
50
Relationship to person with schizophrenia
Parkinson’s Disease
• Parkinson’s disease is a motor disorder
caused by death of dopamine-secreting
neurons in the midbrain; characterized by
muscle tremors, flexed posture, and a shuffling
gait, drugs can help
• Treatment with Deep Brain Stimulation (DBS)
surgery video
• Treatment case study video
© 2011 Pearson Education, Inc.
Alzheimer’s Disease
• Alzheimer’s disease is a mental deterioration
characterized by confusion and memory loss
• Alzheimer’s disease is caused by the formation
of neurofibrillary tangles and amyloid plaques in
the brain
• There is no cure for this disease though some
drugs are effective at relieving symptoms
© 2011 Pearson Education, Inc.
Figure 49.24
Amyloid plaque
Neurofibrillary tangle
20 m
Treatment with pharmaceuticals
• How are medications used to treat
depression, schizophrenia?
Drug Addiction and the Brain’s Reward
System
• The brain’s reward system rewards motivation
with pleasure
• Some drugs are addictive because they
increase activity of the brain’s reward system
• These drugs include cocaine, amphetamine,
heroin, alcohol, and tobacco
• Drug addiction is characterized by compulsive
consumption and an inability to control intake
© 2011 Pearson Education, Inc.
• Addictive drugs enhance the activity of the
dopamine pathway
• Drug addiction leads to long-lasting changes in
the reward circuitry that cause craving for the
drug
• How substances affect brain function –
interactive MOUSE PARTY
© 2011 Pearson Education, Inc.
Figure 49.23
Nicotine
stimulates
dopaminereleasing
VTA neuron.
Inhibitory neuron
Dopaminereleasing
VTA neuron
Opium and heroin
decrease activity
of inhibitory
neuron.
Cocaine and
amphetamines
block removal
of dopamine
from synaptic
cleft.
Cerebral
neuron of
reward
pathway
Reward
system
response
Parting ideas
• What would be needed to cure
quadriplegic conditions?
• Is it possible to cure all
neurodegenerative disorders? How?
• How does Mindflex Duel work?
Preview/Review
• Bozeman: the sensory system