NERVOUS SYSTEM - Warner Pacific Universityclasspages.warnerpacific.edu/BDuPriest/BIO 102/Lecture 15...
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NERVOUS SYSTEM
Transcript of NERVOUS SYSTEM - Warner Pacific Universityclasspages.warnerpacific.edu/BDuPriest/BIO 102/Lecture 15...
NERVOUS SYSTEM
Primary Functions
Monitor changes
External / internal
Integrate input
Process, interpret, make decisions, store information
Initiate a response
E.g., movement, hormone release, stimulate/inhibit
organ function, etc.
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NERVOUS SYSTEM
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Cells of the Nervous System
Neuron
Primary functional cell
of the nervous system
Receive & relay
information
Neuroglial cells
Support neurons
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General Neuron Structure
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General Neuron Structure
Myelin sheath
Speeds rate of impulse transmission
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Types of Neurons
Functional classes
Sensory neurons
Bring information TOWARD the brain or spinal cord
Interneurons
Pass information BETWEEN two neurons
Motor neurons
Send information AWAY from brain or spinal cord
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Nerves
Bundles of axons
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Quick Quiz: A neuron receives input
from other neurons, other cells, or the
environment mostly at its __________.
A) Axon
B) Axon ending (axon terminus)
C) Cell body (soma)
D) Dendrites
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Quick Quiz: The purpose of a myelin
sheath around an axon is to…
A) Speed up transmission of signals.
B) Slow down transmission of signals.
C) Send multiple copies of signals.
D) Prevent transmission of signals.
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Nerve Impulses
Electricity basics
Voltage (V, V= volts)
driving force
Current (I, A=amperes)
flow of charged particles
Resistance (R, W=ohms)
Impedence to current flow
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Nerve Impulses
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Nerve Impulses
Electrical potential (voltage) created by ion
concentration gradients across the plasma
membrane
Sodium (Na+)
At rest, highest concentration OUTSIDE membrane
Potassium (K+)
At rest, highest concentration INSIDE membrane
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Nerve Impulses
Ion flow (current) across the membrane
dependent on ion channels and pumps
Na+/K+ ion pump (builds concentration gradients)
Leak channels (Na+ leaks IN, K+ leaks OUT)
Voltage-gated channels
Open/close in response to changes in voltage across
membrane
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Nerve Impulses
Like the “ideal toilet”…
Threshold stimulus
All or nothing response
Refractory (“reset”) period
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Transmitting a Nerve Impulse
Membrane at rest (resting potential)
All voltage-gated channels CLOSED
Membrane polarized
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Transmitting a Nerve Impulse
Stimulus initiates impulse (action potential) to
reach threshold
Voltage-gated Na+ channels open
Na+ rushes IN
Membrane potential reversed (depolarized)
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Transmitting a Nerve Impulse
Membrane potential reset (repolarization)
Voltage-gated Na+ channels INACTIVATED
Voltage-gated K+ channels OPEN
K+ rushes OUT
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Transmitting a Nerve Impulse
Return to resting state
Ions redistributed to original original locations
Na+/K+ ion pump
Na+ & K+ channels closed
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Neuron / Action Potential Review
Threshold stimulus
“pushing the handle”
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Neuron / Action Potential Review
All or nothing (action potential)
“bowl is draining”
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Neuron / Action Potential Review
Refractory period (reset)
“tank is refilling”
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Quick Quiz: A nerve impulse (action
potential) requires all of the following
EXCEPT:
A) Sodium-potassium pump
B) Potassium leak channels
C) Voltage-gated sodium channels
D) Calcium channels
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Transfer of Stimulus
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axon of a
motor
neuron
muscle fiber
axon terminal
Transfer of Stimulus
Synaptic cleft
Electrical signal converted to chemical signal
Neurotransmitter
Activate ion channels on effector cell membrane
Changes membrane potential of effector
synapse_function 25
Quick Quiz: In order to cross a
synapse, an electrical signal in the first
neuron must…
A) be converted into light energy
B) be converted into a chemical signal
C) be amplified
D) Be reduced
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Organization of the Nervous System
Nerve net
Simplest nervous system
E.g., cnidarians
Loose mesh of nerve cells
Associated with epithelial
tissue
Reflex pathways
(stimulus response)
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Organization of the Nervous System
Bilateral nervous systems
Ganglia
Localized cluster of nerve
cell bodies
Coordinate & integrate
sensory & motor signals
Brain
Larger or master
integration center
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Quick Quiz: True or false: Simple
animals cannot respond to their
environment because they do not have
brains
A) True
B) False
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Vertebrate Nervous System Organization
Functional divisions
Central nervous system
Brain & spinal cord
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Vertebrate Nervous System Organization
Functional divisions
Peripheral nervous
system
Efferent division
Motor (output)
Afferent division
Sensory (input)
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Vertebrate Nervous System Organization
Functional divisions
Peripheral nervous
system - Efferent
Somatic division
“Voluntary”
Motor activity
Autonomic division
“Automatic”
Visceral function
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Vertebrate Nervous System Organization
Functional divisions
Autonomic division
Sympathetic nerves
“Fight or flight”
4-E’s
Parasympathetic
nerves
“Rest & digest”
3-D’s
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Quick Quiz: The autonomic nervous
system is part of the…
A) Central nervous system
B) Somatic nervous system
C) Afferent nervous system (sensory)
D) Efferent nervous system (motor)
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Central Nervous System (CNS)
The vertebrate brain 3 primary divisions
Hindbrain
Reflex centers, sensory integration, coordinated movement, sleep/wake cycles
Midbrain
Coordination of reflex responses to external stimuli
Forebrain
Higher brain functions (memory, learning, critical thinking)
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Human Brain
Hindbrain
Pons
Autonomic reflex
centers
Medulla oblongata
Autonomic reflex
centers
Cerebellum
Coordinated
movement
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Human Brain
Midbrain
Relay center
Other vertebrates
Birds, reptiles, fish
Well developed
optic lobes
Part of brain stem
Midbrain, pons, medulla
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Human Brain
Forebrain
Diencephalon
Thalamus
Directs sensory input to cerebrum
“switchboard”
Hypothalamus
Visceral control center
Cerebrum
Association, learning, memory, speech, vision, hearing, personality, etc.
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Quick Quiz: The hypothalamus is part
of the…
A) Cerebrum
B) Diencephalon
C) Brainstem
D) Cerebellum
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Cerebrum
Cerebral hemispheres
83% of total brain mass
Ridges = gyri
Grooves = sulci
Connected by nerve
tracts
Corpus callosum
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Cerebral Cortex
Functional divisions
Frontal lobes
Reasoning, personality,
learned repetitive
functions, somatic output
Parietal lobes
Sensory
Temporal lobes
Hearing, speech
Occipital lobes
Vision
“Localization” of motor,
sensory & association
areas of the brain
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Motor & Sensory Cortex
Primary somatosensory cortex
Neurons controlling sensory input
from somatic areas
Primary motor cortex
Neurons controlling
motor output
Contralateralization
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Limbic System
“Emotional brain”
Associations with emotions & organs
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Spinal Cord
Vertebral foramen
Meninges
Ganglia
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Spinal Cord
Organization of gray & white matter
dorsal
ventral
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Quick Quiz: True or False: The spinal
cord is part of the central nervous
system
A) True
B) False
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Spinal Reflexes
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Peripheral Nervous System
12 pr cranial nerves
31 pr spinal nerves
All carry both
autonomic and
somatic signals
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Sympathetic Division
“Fight or flight”
Nerves exit from
thoracic & lumbar
areas
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Parasympathetic Division
“Rest & digest”
Nerves exit from cranial
& sacral areas
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Quick Quiz: True or False: The
sympathetic nerves exit the spinal
cord in the thoracic and lumbar
regions.
A) True
B) False
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