Transcript CHAPTER 28 Nervous Systems

CHAPTER 28
Nervous
System
28.1 Nervous systems receive
sensory input, interpret it, and
send out appropriate commands
• The nervous system has three
interconnected functions
– Sensory input: receptors-structures
specialized to detect certain stimuli
– Integration: through the spinal cord & brain
– Motor output: effectors-respond to a
stimulus such as muscles or glands
28.1 Nervous systems receive sensory input,
interpret it, and send out appropriate
commands II
Nervous System
cerebrum
cerebellum
spinal cord
• Central nervous system
– brain & spinal chord
• Peripheral nervous system
– nerves from senses
– nerves to muscles
cervical
nerves
thoracic
nerves
lumbar
nerves
femoral
nerve
sciatic
nerve
tibial
nerve
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Three types of neurons
correspond to the nervous
system’s three main functions
– Sensory neurons convey signals from
sensory receptors into the CNS
– Interneurons integrate data and relay
signals
– Motor neurons convey signals to effectors
Types of neurons
sensory neuron
(from senses)
interneuron
(brain & spinal chord)
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motor neuron
(to muscle)
28.2 Neurons are the functional
units of nervous systems
• Neurons are cells specialized to transmit nervous
impulses
• They consist of
– a cell body ~contains the nucleus
– dendrites (highly branched fibers) stimulus toward cell body
– an axon (long fiber) carries impulses away from cell body
Myelin
coating
signal
direction
 Axon coated with insulation
made of myelin cells

speeds signal
 signal hops from node to node
(Nodes of Ranvier)

330 mph vs. 11 mph
myelin coating
Multiple Sclerosis
2003-2004
 immune system (T cells) attacks myelin coating
 loss of signal
Supporting cells protect, insulate,
and reinforce neurons
• The myelin sheath is the insulating material in vertebrates
– It is composed of a chain of Schwann cells linked by nodes of
Ranvier
– It speeds up signal transmission
– Multiple sclerosis (MS) involves the destruction of myelin sheaths
by the immune system
NERVE SIGNALS AND THEIR TRANSMISSION
28.3 A neuron maintains a membrane
potential across its membrane
• The resting potential of a
neuron’s plasma membrane
is caused by the cell
membrane’s ability to
maintain
– Polarity
– outside axon membrane +
– Inside axon membrane -
• Resting potential is
generated and maintained
with help from sodiumpotassium pumps
– These pump K+ into the cell
and Na+ out of the cell
28.4 A nerve signal begins as a
change in the membrane potential
•
A stimulus alters the permeability of a portion of the plasma
membrane
– Ions pass through the plasma membrane, changing the membrane’s
voltage
– It causes a nerve signal to be generated
•
An action potential is a nerve signal
– It is an electrical change in the plasma membrane voltage from the
resting potential to a maximum level and back to the resting potential
28.5 The action potential propagates
itself along the neuron
• An action potential
is an all-or-none
event
28.6 Neurons communicate at
synapses
– It is a junction or relay
point between two
neurons or between a
neuron and an effector
cell
• Synapses are either
electrical or chemical
– Action potentials pass
between cells at
electrical synapses
– At chemical synapses,
neurotransmitters cross
the synaptic cleft to bind
to receptors on the
surface of the receiving
cell
28.9 Connection: Many drugs act
at chemical synapses
• Drugs act at synapses
and may increase or
decrease the normal
effect of
neurotransmitters
–
–
–
–
Caffeine
Nicotine
Alcohol
Prescription
and illegal drugs
28.12 The peripheral nervous system
of vertebrates is a functional hierarchy
Peripheral
nervous system
Motor
division
Sensory
division
Sensing
external
environment
Sensing
internal
environment
Autonomic
nervous system
(involuntary
Sympathetic
division
Somatic
nervous system
(voluntary
Parasympathetic
division
28.13 Opposing actions of sympathetic and
parasympathetic neurons regulate the
internal environment
– The
parasympathetic
division primes the
body for activities
that gain and
conserve energy
– The sympathetic
division prepares
the body for intense,
energy-consuming
activities
28.15 The structure of a living
supercomputer: The human brain
28.15 The structure of a living
supercomputer: The human brain II
Primitive brain
• The “lower brain”
– medulla oblongata
– pons
– cerebellum
• Functions
– basic body functions
• breathing, heart, digestion, swallowing,
vomiting (medulla)
– homeostasis
– coordination of movement (cerebellum)
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Higher brain
• Cerebrum
– 2 hemispheres
– left = right side of
body
– right = left side of
body
• Corpus callosum
– connection
between 2 hemispheres
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Division of Brain Function
• Left hemisphere
– “logic side”
– language, math, logic operations, vision &
hearing details
– fine motor control
• Right hemisphere
– “creative side”
– pattern recognition, spatial
relationships, non-verbal
ideas, emotions, multi-tasking
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Cerebrum specialization
• Regions specialized for different functions
• Lobes
parietal
frontal
– frontal
• speech,
control of emotions
– temporal
• smell, hearing
– occipital
• vision
– parietal
• speech, taste
reading
temporal2003-2004
occipital
Limbic system
Controls basic emotions (fear, anger), involved in emotional bonding,
establishes emotional memory
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Simplest Nerve Circuit
 Reflex, or automatic response
rapid response
 automated
 signal only goes to
spinal cord
 no higher level
processing
 advantage
 essential actions
 don’t need to think or
make decisions about
 blinking
 balance
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 pupil dilation
 startle

cerebrum
cerebellum
spinal cord
cervical
nerves
thoracic
nerves
lumbar
nerves
femoral
nerve
Any Questions??
sciatic
nerve
tibial
nerve
2003-2004