Post on 16-Mar-2018
Neural Control
Chapter 33 Part 2
33.6 A Smorgasbord of Signals
Different types of neurons release different
neurotransmitters; Parkinson’s disease involves
dopamine-secreting neurons and motor control
Fig. 33-13a, p. 562
Fig. 33-13b, p. 562
Fig. 33-13c, p. 562
Major Neurotransmitters
and Their Effects
The Neuropeptides
Neuromodulators
• Neuropeptides made by some neurons that
influence the effects of neurotransmitters
• Substance P enhances pain
• Enkephalins and endorphins are pain killers
33.7 Drugs Disrupts Signaling
Psychoactive drugs exert their effects by
interfering with the action of neurotransmitters
• Stimulants (nicotine, caffeine, cocaine,
amphetamines)
• Depressants (alcohol, barbiturates)
• Analgesics (narcotics, ketamine, PCP)
• Hallucinogens (LSD, THC)
PET Scan: Effects of Cocaine
Signs of Drug Addiction
33.2-33.7 Key Concepts
How Neurons Work
Messages flow along a neuron’s plasma
membrane, from input to output zones
Chemicals released at a neuron’s output zone
may stimulate or inhibit activity in an adjacent
cell
Psychoactive drugs interfere with the information
flow between cells
33.8 The Peripheral Nervous System
Peripheral nerves carry information to and from
the central nervous system
Nerves are bundled axons of many neurons
Each axon is wrapped in a myelin sheath that
increases transmission speed
Nerve Structure and Function
Nerve Structure and Function
Nerve Structure and Function
Nerve Structure and Function
Fig. 33-15a, p. 564
myelin
sheath
axon
blood vessels
nerve fascicle (a
number of axons
bundled inside
connective tissue)
the nerve’s outer
wrapping
Fig. 33-15b, p. 564
unsheathed node axon
b “Jellyrolled” Schwann
cells of an axon’s myelin
sheath
Fig. 33-15c, p. 564
Na+
action potential resting potential resting potential
Fig. 33-15d, p. 564
K+Na+
resting potential restored action potential resting potential
Divisions of
the Peripheral Nervous System
Somatic nervous system
• Conducts information about the environment to
the central nervous system (involuntary)
• Controls skeletal muscles (voluntary)
Autonomic nervous system
• Conducts signals to and from internal organs and
glands
Divisions of
the Autonomic Nervous System
The two divisions of the autonomic nervous
system have opposing effects on effectors
Sympathetic neurons are most active in times
of stress or danger (fight-flight response)
Parasympathetic neurons are most active in
times of relaxation
Divisions of
the Autonomic Nervous System
Fig. 33-16, p. 565
eyesoptic nerve
midbrain
salivary glandsmedulla
oblongata
cervical
nerves (8
pairs)
heartvagus
nervelarynx
bronchi lungs
stomach
liver spleen
pancreas
thoracic
nerves
(12 pairs)
kidneys
adrenal glands
small intestine
upper colon (all ganglia
in walls of
organs)lower colon
rectum
lumbar
nerves (5
pairs)
(most ganglia
near spinal
cord)
bladder sacral
nerves (5
pairs)uterus pelvic
nerve
genitals
33.9 The Spinal Cord
Spinal cord
• Runs through the vertebral column and connects
peripheral nerves with the brain
• Serves as a reflex center
Central nervous system (CNS)
• The brain and spinal cord
Protective Features
Meninges
• Three membranes that cover and protect the
CNS
Cerebrospinal fluid
• Fills central canal and spaces between meninges
• Cushions blows
White Matter and Gray Matter
White matter
• Bundles of myelin-sheathed axons (tracts)
• Outermost portion of spinal cord
Gray matter
• Nonmyelinated structures (cell bodies, dendrites,
neuroglial cells)
Reflex Pathways
Reflex
• An automatic response to a stimulus
• Stretch reflex, knee-jerk reflex, withdrawal reflex
Spinal reflexes do not involve the brain
• Signals from sensory neurons enter the cord
through the dorsal root of spinal nerves
• Commands for responses go out on the ventral
root of spinal nerves
Stretch Reflex
Fig. 33-18, p. 567
A Fruit being loaded into a bowl puts weight on an arm muscle and stretches it. Will the bowl drop? NO! Muscle spindles in the muscle’s sheath also are stretched.
STIMULUS
Biceps stretches.
B Stretching stimulates sensory receptor endings in this muscle spindle. Action potentials are propagated toward spinal cord.
C In the spinal cord, axon terminals of the sensory neuron release a neurotransmitter that diffuses across a synaptic cleft and stimulates a motor neuron.
D The stimulation is strong enough to generate action potentials that self-propagate along the motor neuron’s axon.
E Axon terminals of the motor neuron synapse with muscle fibers in the stretched muscle.
F ACh released from the motor neuron’s axon terminals stimulates muscle fibers.
RESPONSEBiceps contracts.
G Stimulation makes the
stretched muscle contract.
Ongoing stimulations
and contractions hold the bowl steady.
muscle
spindle
neuromuscular
junction
33.8-33.9 Key Concepts
Vertebrate Nervous System
The central nervous system consists of the brain
and spinal cord
The peripheral nervous system includes many
pairs of nerves that connect the brain and spinal
cord to the rest of the body
The spinal cord and peripheral nerves interact in
spinal reflexes
33.10 The Vertebrate Brain
The brain is the body’s main information
integrating organ, part of the CNS
During development, the brain is organized as
three functional regions: forebrain, midbrain and
hindbrain
Hindbrain and Midbrain
The hindbrain includes the medulla oblongata,
the pons, and the cerebellum
The midbrain in mammals is reduced
The brain stem (pons, medulla, and midbrain) is
involved in reflex behaviors
The Forebrain
Cerebrum
• Main processing center in humans
• Evolved as an expansion of the olfactory lobe
Thalamus and hypothalamus
• Important in thirst, temperature regulation, and
other responses related to homeostasis
Development of the Human Brain
Fig. 33-19 (a-c), p. 568
Fig. 33-19 (a-c), p. 568
forebrain midbrain
hindbrain
Protection at the Blood-Brain Barrier
Blood-brain barrier
• Protects the CNS from harmful substances
• Tight junctions form a seal between adjoining
cells of capillary walls
• Some toxins (nicotine, alcohol, caffeine, mercury)
are not blocked
The Human Brain
Cerebellum
• Has more interneurons than other brain regions
• Involved in balance, motor skills and language
Cerebrum
• Divided into two hemispheres, coordinated by
signals across the corpus callosum
• Each hemisphere deals with the opposite side of
the body
Major Brain Regions of Vertebrates
Fig. 33-20a, p. 569
olfactory
lobe
forebrain
midbrain
hindbrain
FISH AMPHIBIAN REPTILE BIRD
shark frog alligator goose
Fig. 33-20b, p. 569
Fig. 33-20b, p. 569
corpus
callosum
hypothalamus thalamus pineal
gland
locationpart of
optic
nerve
midbrain
cerebellum
pons
medulla oblongata
33.11 The Human Cerebrum
Each cerebral hemisphere is divided into frontal,
temporal, occipital and parietal lobes
Cerebral cortex
• Outermost gray matter of the cerebrum
• Controls voluntary activity, sensory perception,
abstract thought, language and speech
• Distinct areas receive and process signals
Lobes of the Brain
Fig. 33-21, p. 570
frontal lobe
(planning of
movements,
aspects of
memory,
inhibition of
unsuitable
behaviors)
primary
motor
cortex
primary
somatosen
sory cortex
parietal
lobe
(visceral
sensations)
Wernicke’s
area
Broca’s area
temporal lobe (hearing,
advanced visual processing)
occipital lobe
(vision)
Functions of the Cerebral Cortex
Specific areas of the cerebral cortex correspond
to specific body parts or functions
Examples:
• The body is spatially mapped out in the primary
motor cortex of each frontal lobe
• Association areas are scattered throughout the
cortex, but not in motor or sensory areas
The Primary Motor Cortex
Association Areas Integrate Inputs
Fig. 33-23, p. 570
Motor cortex activity
when speaking
Prefrontal cortex activity
when generating words
Visual cortex activity when
seeing written words
Connections With the Limbic System
The cerebral cortex oversees the limbic system
Limbic system
• Governs emotions, assists in memory, correlates
emotional-visceral responses
• Includes the hypothalamus, hippocampus,
amygdala, and cingulate gyrus
Limbic System Components
Fig. 33-24, p. 571
(olfactory
tract)
cingulate gyrus thalamus hypothalamus
amygdala
hippocampus
Making Memories
The cerebral cortex receives information and
processes some of it into memories
Memory forms in stages
• Short-term memory lasts seconds to hours
• Long-term memory is stored permanently
• Skill memory involves the cerebellum
• Declarative memory stores facts and impressions
Stages in Memory Processing
Fig. 33-25, p. 571
Sensory stimuli, as from
the nose, eyes, and ears
Temporary storage in
the cerebral cortexInput forgotten
SHORT-TERM MEMORY
Emotional state, having time
to repeat (or rehearse) input,
and associating the input with
stored categories of memory
influence transfer to long-term
storage
Recall of
stored
input
LONG-TERM MEMORYInput irretrievable
Fig. 33-25, p. 571
Sensory stimuli, as from
the nose, eyes, and ears
Temporary storage in
the cerebral cortex
SHORT-TERM MEMORY
Emotional state, having time
to repeat (or rehearse) input,
and associating the input with
stored categories of memory
influence transfer to long-term
storage
LONG-TERM MEMORYInput irretrievable Stepped Art
Input forgotten
Recall of
stored
input
33.12 The Split Brain
Investigations by Roger Sperry into the
importance of information flow between the
cerebral hemispheres showed that the two
halves of the brains have a division of labor
Typically, math and language skills reside in the
left hemisphere; the right hemisphere interprets
music, spatial relationships, and visual inputs
Visual Information and the Brain
Fig. 33-26, p. 572
Left Half of
Visual FieldRight Half of
Visual FieldCOWBOY COW BOY
pupil
optic
nervesretina
optic
chiasm
corpus
callosum
left
visual
cortex
right
visual
cortex
Split-Brain Studies
33.13 Neuroglia—
The Neurons’ Support Staff
Neuroglial cells make up the bulk of the brain
The adult brain has four types of neuroglial cells
• Oligodendrocytes make myelin
• Microglia have immune system functions
• Astrocytes secrete various substances, take up
neurotransmitters, assist in immune defenses,
and stimulate formation of the blood-brain barrier
• Ependymal cells line brain cavities
Astrocytes
About Brain Tumors
Unlike neurons, neuroglia continue to divide in
adults, and can be a source of primary brain
tumors (gliomas)
Exposure to ionizing radiation such as x-rays, or
to chemical carcinogens, increases risk
33.10-33.13 Key Concepts
About the Brain
The brain develops from the anterior part of the
embryonic nerve cord
A human brain includes evolutionarily ancient
tissues and newer regions that provide the
capacity for analytical thought and language
Neuroglia make up the bulk of the brain