Download Chapter 49 Nervous Systems (working2)

Chapter 49
Nervous Systems
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Overview: Command and Control Center
•
The circuits in the brain are more complex than the most powerful
computers
•
Functional magnetic resonance imaging (MRI) can be used to
construct a 3-D map of brain activity
•
The vertebrate brain is organized into regions with different functions
•
Each single-celled organism can respond to stimuli in its environment
•
Animals are multicellular and most groups respond to stimuli using
systems of neurons
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
This imaged produced by functional magnetic resonance imaging (fMRI).
When the brain is scanned with electromagnetic waves, changes in blood
oxygen where the brain is active generate a signal that can be recorded.
Organization of the Vertebrate Nervous System
•
The spinal cord conveys information from the brain to the PNS
•
The spinal cord also produces reflexes independently of the brain
•
A reflex is the body’s automatic response to a stimulus
–
For example, a doctor uses a mallet to trigger a knee-jerk reflex
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 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
Fig. 49-4
Central nervous
system (CNS)
Brain
Spinal
cord
The spinal cord and
brain develop from
the embryonic
nerve cord
Peripheral nervous
system (PNS)
Cranial
nerves
Ganglia
outside
CNS
Spinal
nerves
Fig. 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
Glia in the CNS
•
Glia have numerous functions ( Do not memorize except where noted)
–
Ependymal cells promote circulation of cerebrospinal fluid
–
Microglia protect the nervous system from microorganisms
–
Oligodendrocytes and Schwann cells form the myelin sheaths
around axons (You need to know about Schwann Cells!)
–
Astrocytes provide structural support for neurons, regulate
extracellular ions and neurotransmitters, and induce the formation
of a blood-brain barrier that regulates the chemical environment
of the CNS
–
Radial glia play a role in the embryonic development of the
nervous system
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 49-6
PNS
CNS
VENTRICLE
Neuron
Astrocyte
Ependymal
cell
Oligodendrocyte
Schwann cells
Microglial
cell
Capillary
50 µm
(a) Glia in vertebrates
(b) Astrocytes (LM)
The Peripheral Nervous System
•
The PNS transmits information to and from the CNS and regulates
movement and the internal environment
•
In the PNS, afferent neurons transmit information to the CNS and
efferent neurons transmit information away from the CNS
•
Cranial nerves originate in the brain and mostly terminate in organs of
the head and upper body
•
Spinal nerves originate in the spinal cord and extend to parts of the
body below the head
•
The PNS has two functional components: the motor system and the
autonomic nervous system
•
The motor system carries signals to skeletal muscles and is voluntary
•
The autonomic nervous system regulates the internal environment in
an involuntary manner
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
•
The autonomic nervous system has sympathetic, parasympathetic, and
enteric divisions
•
The sympathetic and parasympathetic divisions have antagonistic
effects on target organs
•
The sympathetic division correlates with the “fight-or-flight” response
•
The parasympathetic division promotes a return to “rest and digest”
•
The enteric division controls activity of the digestive tract, pancreas,
and gallbladder
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 49-7-2
PNS
Afferent
(sensory) neurons
Efferent
neurons
Autonomic
nervous system
Motor
system
Locomotion
Sympathetic
division
Parasympathetic
division
Hormone
Gas exchange Circulation action
Hearing
Enteric
division
Digestion
Fig. 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 genitals
Inhibits emptying
of bladder
Sacral
Synapse
Promotes ejaculation and
vaginal contractions
Concept 49.2: The vertebrate brain is regionally
specialized
•
All vertebrate brains develop from three embryonic regions: forebrain,
midbrain, and hindbrain
•
By the fifth week of human embryonic development, five brain regions
have formed from the three embryonic regions
•
As a human brain develops further, the most profound change occurs
in the forebrain, which gives rise to the cerebrum
•
The outer portion of the cerebrum called the cerebral cortex
surrounds much of the brain
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 49-9
Cerebrum (includes cerebral cortex, white matter,
basal nuclei)
Telencephalon
Forebrain
Diencephalon
Midbrain
Diencephalon (thalamus, hypothalamus, epithalamus)
Mesencephalon
Midbrain (part of brainstem)
Metencephalon
Pons (part of brainstem), cerebellum
Myelencephalon
Medulla oblongata (part of brainstem)
Hindbrain
Diencephalon:
Cerebrum
Mesencephalon
Hypothalamus
Metencephalon
Thalamus
Midbrain
Hindbrain
Forebrain
Diencephalon
Spinal cord
Telencephalon
Pineal gland
(part of epithalamus)
Myelencephalon
Brainstem:
Midbrain
Pons
Pituitary
gland
Medulla
oblongata
Spinal cord
Cerebellum
Central canal
(a) Embryo at 1 month
(b) Embryo at 5 weeks
(c) Adult
Fig. 49-UN1
The Brainstem
• The brainstem coordinates and conducts information
between brain centers
• The brainstem has three parts: the midbrain, the
pons, and the medulla oblongata
• The midbrain contains centers for receipt and
integration of sensory information
• The pons regulates breathing centers in the medulla
• The medulla oblongata contains centers that control
several functions including breathing, cardiovascular
activity, swallowing, vomiting, and digestion
Fig. 49-UN2
The Cerebellum
• The cerebellum is important for coordination and error checking during
motor, perceptual, and cognitive functions
• It is also involved in learning and remembering motor skills
Fig. 49-UN3
The Diencephalon
• The diencephalon develops into three regions:
the epithalamus, thalamus, and hypothalamus
• The epithalamus includes the pineal gland and
generates cerebrospinal fluid from blood
• The thalamus is the main input center for
sensory information to the cerebrum and the
main output center for motor information
leaving the cerebrum
• The hypothalamus regulates homeostasis
and basic survival behaviors such as feeding,
fighting, fleeing, and reproducing
• The hypothalamus also regulates circadian
rhythms such as the sleep/wake cycle
Fig. 49-UN4
The Cerebrum
• The cerebrum has right and left cerebral
hemispheres
• Each cerebral hemisphere consists of a
cerebral cortex (gray matter) overlying white
matter and basal nuclei
• In humans, the cerebral cortex is the largest
and most complex part of the brain
• A thick band of axons called the corpus
callosum provides communication between
the right and left cerebral cortices
• The right half of the cerebral cortex controls
the left side of the body, and vice versa
Fig. 49-13
Left cerebral
hemisphere
Right cerebral
hemisphere
Corpus
callosum
Thalamus
Cerebral
cortex
Basal
nuclei
Vertebrate Skeletal Muscle
Chapter 50 Pages 1105-1110
• Vertebrate skeletal muscle is characterized by a hierarchy of smaller
and smaller units
• A skeletal muscle consists of a bundle of long fibers, each a single cell,
running parallel to the length of the muscle
• Each muscle fiber is itself a bundle of smaller myofibrils arranged
longitudinally
• The myofibrils are composed to two kinds of myofilaments:
– Thin filaments consist of two strands of actin and one strand of
regulatory protein
– Thick filaments are staggered arrays of myosin moleculles
• Skeletal muscle is also called striated muscle because the regular
arrangement of myofilaments creates a pattern of light and dark bands
• The functional unit of a muscle is called a sarcomere, and is bordered
by Z lines
Fig. 50-25
Muscle
Bundle of
muscle fibers
Nuclei
Single muscle fiber
(cell)
Plasma membrane
Myofibril
Z lines
Sarcomere
TEM
M line
0.5 µm
Thick
filaments
(myosin)
Thin
filaments
(actin)
Z line
Z line
Sarcomere
The Sliding-Filament Model of
Muscle Contraction
• According to the sliding-filament model, filaments slide past each
other longitudinally, producing more overlap between thin and thick
filaments
• The sliding of filaments is based on interaction between actin of the
thin filaments and myosin of the thick filaments
• The “head” of a myosin molecule binds to an actin filament, forming a
cross-bridge and pulling the thin filament toward the center of the
sarcomere
• Glycolysis and aerobic respiration generate the ATP needed to sustain
muscle contraction
Fig. 50-26
Sarcomere
Z
M
Relaxed
muscle
Contracting
muscle
Fully contracted
muscle
Contracted
Sarcomere
0.5 µm
Z
• The sliding of filaments is based on interaction between actin of the
thin filaments and myosin of the thick filaments
• The “head” of a myosin molecule binds to an actin filament, forming a
cross-bridge and pulling the thin filament toward the center of the
sarcomere
• Glycolysis and aerobic respiration generate the ATP needed to sustain
muscle contraction
Fig. 50-27-1
Thick filament
Thin
filaments
Thin filament
ATP
Myosin head (lowenergy configuration
Thick
filament
Fig. 50-27-2
Thick filament
Thin
filaments
Thin filament
ATP
Myosin head (lowenergy configuration
Thick
filament
Actin
ADP
Pi
Myosin
binding sites
Myosin head (highenergy configuration
Fig. 50-27-3
Thick filament
Thin
filaments
Thin filament
Myosin head (lowenergy configuration
ATP
Thick
filament
Actin
ADP
Pi
ADP
Pi
Cross-bridge
Myosin
binding sites
Myosin head (highenergy configuration
Fig. 50-27-4
Thick filament
Thin
filaments
Thin filament
Myosin head (lowenergy configuration
ATP
ATP
Thick
filament
Thin filament moves
toward center of sarcomere.
Actin
ADP
Myosin head (lowenergy configuration
ADP
+ Pi
Pi
ADP
Pi
Cross-bridge
Myosin
binding sites
Myosin head (highenergy configuration
Muscle Fiber Contraction
•
•
•
•
•
http://www.youtube.com/watch?v=EdHzKYDxrKc
http://www.youtube.com/watch?v=WRxsOMenNQM
http://www.youtube.com/watch?v=0kFmbrRJq4w
http://www.youtube.com/watch?v=70DyJwwFnkU&NR=1
http://bcs.whfreeman.com/thelifewire/content/chp47/4702001.html
The Role of Calcium and
Regulatory Proteins
• A skeletal muscle fiber contracts only when stimulated by a motor
neuron
• When a muscle is at rest, myosin-binding sites on the thin filament are
blocked by the regulatory protein tropomyosin
• For a muscle fiber to contract, myosin-binding sites must be uncovered
• This occurs when calcium ions (Ca2+) bind to a set of regulatory
proteins, the troponin complex
• Muscle fiber contracts when the concentration of Ca2+ is high; muscle
fiber contraction stops when the concentration of Ca2+ is low
Fig. 50-28
Tropomyosin
Actin
Troponin complex
Ca2+-binding sites
(a) Myosin-binding sites blocked
Ca2+
Myosinbinding site
(b) Myosin-binding sites exposed
Fig. 50-29
Motor
neuron axon
Synaptic
terminal
T tubule
The stimulus
leading to
contraction of a
muscle fiber is
an action
potential in a
ACh
motor neuron
that makes a
synapse with
the muscle fiber
Mitochondrion
Sarcoplasmic
reticulum (SR)
Myofibril
Plasma membrane
of muscle fiber
Ca2+ released from SR
Sarcomere
Synaptic terminal
of motor neuron
T Tubule
Synaptic cleft
Plasma membrane
SR
Ca2+
ATPase
pump
Ca2+
ATP
CYTOSOL
Ca2+
ADP
Pi
Fig. 50-29a
The synaptic terminal of the motor neuron releases the neurotransmitter
acetylcholine
Acetylcholine depolarizes the muscle, causing it to produce an action
potential
http://www.youtube.com/watch?v=ZscXOvDgCmQ (neuromuscular
Motor
Synaptic
junction)
terminal
T tubule
neuron axon
Mitochondrion
Sarcoplasmic
reticulum (SR)
Myofibril
Plasma membrane
of muscle fiber
Sarcomere
Ca2+ released from SR
Fig. 50-29b
Synaptic terminal
of motor neuron
T Tubule
Synaptic cleft
ACh
Plasma membrane
SR
Ca2+
ATPase
pump
Ca2+
ATP
CYTOSOL
Ca2+
ADP
Pi
• Action potentials travel to the interior of the muscle fiber along
transverse (T) tubules
• The action potential along T tubules causes the sarcoplasmic
reticulum (SR) to release Ca2+
• The Ca2+ binds to the troponin complex on the thin filaments
• This binding exposes myosin-binding sites and allows the cross-bridge
cycle to proceed
• Amyotrophic lateral sclerosis (ALS), formerly called Lou Gehrig’s
disease, interferes with the excitation of skeletal muscle fibers; this
disease is usually fatal (don’t memorize)
• Myasthenia gravis is an autoimmune disease that attacks acetylcholine
receptors on muscle fibers; treatments exist for this disease (don’t
memorize)
•
Nervous Control of Muscle
Tension
Contraction of a whole muscle is graded, which means that the extent
and strength of its contraction can be voluntarily altered
• There are two basic mechanisms by which the nervous system
produces graded contractions:
– Varying the number of fibers that contract
– Varying the rate at which fibers are stimulated
•
In a vertebrate skeletal muscle, each branched muscle fiber is
innervated by one motor neuron
•
Each motor neuron may synapse with multiple muscle fibers
•
A motor unit consists of a single motor neuron and all the muscle
fibers it controls
Fig. 50-30
Spinal cord
Motor
unit 1
Motor
unit 2
Synaptic terminals
Nerve
Motor neuron
cell body
Motor neuron
axon
Muscle
Muscle fibers
Tendon
Other Types of Muscle
• In addition to skeletal muscle, vertebrates have cardiac muscle and
smooth muscle
• Cardiac muscle, found only in the heart, consists of striated cells
electrically connected by intercalated disks
• Cardiac muscle can generate action potentials without neural input
• In smooth muscle, found mainly in walls of hollow organs,
contractions are relatively slow and may be initiated by the muscles
themselves
• Contractions may also be caused by stimulation from neurons in the
autonomic nervous system
Concept 50.6: Skeletal systems
transform muscle contraction into
locomotion
• Skeletal muscles are attached in antagonistic pairs, with each member
of the pair working against the other
• The skeleton provides a rigid structure to which muscles attach
• Skeletons function in support, protection, and movement
Fig. 50-32
Human
Grasshopper
Extensor
muscle
relaxes
Biceps
contracts
Biceps
relaxes
Triceps
contracts
Flexor
muscle
contracts
Forearm
flexes
Triceps
relaxes
Tibia
flexes
Extensor
muscle
contracts
Forearm
extends
Tibia
extends
Flexor
muscle
relaxes