Download Chapter 40

40
Neural Regulation
Lecture Outline
I.
Invertebrate nervous systems
A. Cnidarians have a nerve net
B. Echinoderms have a radial nervous system
C. Bilaterally symmetric animals have a bilateral nervous system
1. Increased number of nerve cells
2. Concentration of nerve cells into ganglia and brains, nerves, and nerve
cords
3. Specialized function into peripheral afferent and efferent nerves,
connecting to the CNS
4. An increased number of association neurons and other synaptic
connections
5. Cephalization, with a concentration of nervous (including sensory) tissue
at the head end
D. Flatworms have cerebral ganglia that serve as a brain
1. Two ventral solid nerve cords extend to the posterior of the worm
E. Annelid and arthropod nervous systems have single, ventrally located nerve
cords
1. The brain of the earthworm is not necessary for survival
F. Mollusks typically have 3 pairs of ganglia: cerebral, visceral, and pedal
ganglia
1. The octopus has a very well developed nervous system and is capable of
learning
II.
The vertebrate nervous system has two main divisions: CNS and PNS
A. The CNS consists of the brain and spinal cord
B. The PNS is made up of sensory receptors and nerves
1. Afferent nerves are sensory
2. Efferent nerves innervate muscles or glands and are motor
a) The PNS can be divided into the somatic and autonomic divisions
b) Further, the autonomic division has two pathways, the sympathetic
and parasympathetic nerves
III.
The evolution of the vertebrate brain is marked by increasing complexity
A. All vertebrates have similar brain structures, with specializations of different
parts in different classes
1. The embryonic neural tube develops into the brain and spinal cord
2. The brain differentiates into the hindbrain, midbrain, and forebrain
B.
The hindbrain develops into the medulla, pons, and cerebellum
1. The hindbrain divides to form the metencephalon (which forms the
cerebellum and pons), and the myelencephalon (which forms the medulla)
2. The medulla, pons, and midbrain compose the brain stem, which holds up
the cerebrum
3. The medulla is primarily composed of tracts that connect the spinal cord
with the rest of the brain
a) Centers in the medulla regulate respiration, heartbeat, and vasomotor
activities
4. The cerebellum is a motor control center
5. In mammals, the pons connects the spinal cord and medulla to the higher
portions of the brain and regulates respiration
C. The midbrain is most prominent in fish and amphibians
1. The midbrain is a primary associative area in fishes and amphibians
a) The optic lobes are specialized for visual interpretation
2. In reptiles, birds, and mammals, the midbrain forms the superior and
inferior colliculi, and the red nucleus
D. The forebrain gives rise to the thalamus, hypothalamus, and cerebrum
1. The forebrain forms the telencephalon and diencephalon
2. The diencephalon forms the thalamus and hypothalamus
a) The thalamus is a relay center for sensory message
b) The hypothalamus contains olfactory centers, and integrates the
autonomic system, controls temperature, emotions, and many other
functions
3. The telencephalon gives rise to the cerebrum and the olfactory bulbs in
most vertebrates
a) The cerebrum is divided into two hemispheres, and is made of white
matter (axons) and gray matter (cell bodies)
b) In fish and amphibians, the cerebrum is primarily adapted for
interpretation of olfactory information
c) In birds, the corpus striatum is highly developed and is involved in
the complex behaviors characteristic of birds
d) Some reptiles and all mammals have the neocortex, an important
associative area
(1) In mammals, most of the cerebral cortex is neocortex
e) The cortex is highly folded in large complex mammals into
convolutions, separated by shallow furrows called sulci and deep
furrows called fissures
IV.
The human central nervous system is remarkably complex
A. The brain and spinal cord are covered by three layers of connective tissue, the
meninges
1.
2.
3.
4.
The outer layer is the dura mater, the middle layer is the arachnoid, and
the inner layer is the pia mater
Between the arachnoid and pia mater is the subarachnoid space, which
contains cerebrospinal fluid
CSF is produced by choroid plexi located in the ventricles
CSF nourishes and protects the brain
B.
The spinal cord transmits impulses to and from the brain
1. The spinal cord extends from the medulla to the beginning of the lumbar
vertebrae
2. The spinal cord is composed of gray matter in the shape of an H in cross
section (the horns)
a) The gray matter is the location of the cell bodies
b) The white matter is on the periphery, and is composed of myelinated
axons arranged in tracts
(1) Sensory tracts conduct information toward the brain
3. Reflexes are fixed responses to simple stimuli
a) Many unconscious activities are reflexes
b) A withdrawal reflex is a neural circuit only involving three neurons
(1) The sensory neuron synapses with an association neuron in the
gray matter of the spinal cord, which immediately synapses with
a motor neuron
C. The most prominent part of the human brain is the cerebrum
1. Sensory areas receive information from sense organs
a) The primary motor areas are located in the frontal lobes just anterior to
the central sulcus
2. Motor areas control voluntary movement
a) The primary sensory areas are located in the parietal lobes, just
posterior to the central sulcus
3. Association areas lend meaning to what is sensed; they allow thought,
learning, and personality
4. The occipital lobe contains the visual centers
5. The temporal lobe contains the auditory centers
6. The central sulcus separates the frontal and parietal lobes
7. The corpus callosum connects the right and left hemispheres, and is
composed of tracts of white matter
8. Basal ganglia are areas of gray matter buried deep in the white matter of
the cerebral hemispheres
a) The substantia nigra is one of the basal ganglia
D. Brain activity cycles in a sleep-wake pattern
1. An EEG is a recording of electrical potentials and indicates what areas of
the brain are active
2. Alpha waves come from the occipital lobes when the eyes are closed
3. Beta waves occur when the eyes are open
4. Delta and theta waves occur during deep sleep
5. The RAS (reticular activating system) acts as an arousal center and keeps
the brain alert
6. Sleep is an unconscious period when a person can be aroused
a) REM sleep is characterized by beta waves and dreaming
b) Non-REM sleep is characterized by delta waves
c)
The raphe nuclei in the pons and medulla are involved in producing
sleep
E. The limbic system affects emotional aspects of behavior
1. The limbic system is composed of several structures of the cerebrum and
diencephalon
2. Dopamine is an important neurotransmitter of the limbic system, and is
involved in mood as well as several neurologic disorders
F. Learning involves the storage of information and its retrieval
1. Learning is a long-lasting change in behavior based on experience, and
involves both implicit and explicit memory
2. Information processing involves short- and long-term memory
a) Short-term memory can hold about 7 pieces of information, may last
about 20 seconds, and may involve reverberating circuits
b) Long-term memory involves encoding information and then
consolidating, a process that depends on the hippocampus and
involves the expression of genes
c) Memory circuits are formed throughout the brain
d) No particular area can be labeled as the site of memory, rather
memories may be stored in various associative areas, the limbic
system, thalamus, and hypothalamus
e) Wernicke’s area is important in complex thought processes and
language
3. Neurophysiological changes occur during learning
a) Short-term memory involves changes in the neurotransmitter
receptors of postsynaptic neurons
b) Long-term memory involves slower, but longer-lasting changes in
synaptic connections
(1) Activated receptors linked to G proteins
(2) Cyclic AMP activates a protein kinase, which in turn
phosphorylates a transcription factor known as CREB
(3) Synaptic enhancement may occur in presynaptic terminals
(4) Potentiation is a longer form of synaptic enhancement and may
last for several minutes
4. Experience affects development and learning
a) Environmental experiences may affect neural development
b) During early life, certain critical or sensitive periods of nervous system
development occur that are in influenced by environmental stimuli
V.
The peripheral nervous system includes somatic and autonomic divisions
A. The somatic division helps the body adjust to the external environment
1. In humans, 12 pairs of cranial nerves and 31 pairs of spinal nerves
innervate the body
2. Each spinal nerve has a dorsal (sensory) root and a ventral (motor) root
B.
VI.
The autonomic system regulates the internal environment
1. The autonomic system maintains homeostasis
2. The efferent portion is subdivided into the sympathetic and
parasympathetic systems
a) The sympathetic system primarily stimulates organs
b) The parasympathetic system tends to act after sympathetic stimulation
and in contrasting ways
3. The autonomic system has two efferent neurons acting in sequence
4. The sympathetic ganglia are located in the paravertebral ganglion chain,
located on each side of the spinal cord, or collateral ganglia near the aorta,
or major arteries in the abdomen
5. The parasympathetic ganglia are located in terminal ganglia near the
organs they innervate
6. The sympathetic neurons secrete acetylcholine or norepinephrine; the
parasympathetic neurons only secrete acetylcholine
7. Biofeedback allows a person some control over the autonomic system
Many drugs affect the nervous system
A. Many prescribed drugs alter psychological conditions
B. Habitual use may result in psychological dependence
1. Tolerance may result in the need for higher dosages
C. Use of some drugs may result in addiction
Research and Discussion Topics

Investigate various reflexes, such as the patellar, corneal, and Babinski’s reflexes.
Describe the neural circuits that result in these reflexes.

Draw the brains of a shark, fish, frog, bird, cat, and human. Analyze the relative
sizes of the various parts of the brain and relate those to the differences between the
animals.

Describe a disorder of the brain, and relate the anatomy and physiology of the brain
to the disease symptoms and treatment for the disorder. Possible topics:
Alzheimer’s or Parkinson’s disease, cerebral palsy, multiple sclerosis.