Download Chapter 49 Worksheet: Nervous Systems The Evolution and

Chapter 49 Worksheet: Nervous Systems
The Evolution and Diversity of Nervous Systems
1. Compare and contrast the nervous systems of the following animals and explain how variation in
design and complexity relate to their phylogeny, natural history, and habitat: hydra, sea star, planarian,
insects, mollusks, and vertebrates.
In the simplest animals with nervous systems, cnidarians, radially symmetrical bodies are organized
around a gastro vascular cavity, with a series of interconnected nerve nets forming a diffuse net. This is
true of the hydra. More complex animals such as the sea star have a set of radial nerves connecting to a
central nerve ring, with the axons of multiple nerve cells bundled together as nerves that channel and
organize information flow along specific routes through the nervous system. Sea stars, like the hydra,
have a nerve net from which a radial nerve links to each arm. The planarian non segmented worm has the
simplest clearly defined central nervous system, with a small brain and longitudinal nerve cords, while
also exhibiting cephalization. More complex invertebrates like insects have many more neurons, more
complicated brains, and by ventral nerve cords around ganglia (segmentally arranged clusters of neurons).
Mollusks have relatively simple organs and little to no cephalization, while the active predatory mollusks
like the squid has the most sophisticated nervous system of invertebrates. Vertebrates have a brain and
spinal cord forming the central nervous system and nerves and ganglia forming the peripheral nervous
system.
Vertebrate Nervous Systems
2. Compare the structures and functions of the central nervous system and peripheral nervous system.
Central Nervous System
Peripheral Nervous System
Structure:
 Composed of brain and spinal cord
 Ganglia present outside spinal cord
 Central canal of spinal cord and ventricles of
brain filled with cerebrospinal fluid.
 Contain gray and white matter
 Segementalization of neurons within spinal
cord.
 Contain different types of glia
Structure:
 Consists of left-right pairs pf cranial and
spinal nerves and their associated ganglia.
 Cranial nerves connect brain with organs in
head and upper body
 Spinal nerves runs between spinal cord and
parts of body below the head
 Most cranial nerves and all spinal nerves
contain both afferent and efferent neurons
 Efferent branch consists of motor system and
automatic nervous system.



Function:
 Spinal cord acts as part of the simple nerve
circuits producing reflexes.
 Spinal cord conveys information to and from
the brain and generates basic patterns of
locomotion.

Function:
 Transmits information to and from the CNS
 Regulates an animal’s movement and internal
environment
3. Distinguish between the functions of the autonomic nervous system and the somatic nervous system.
The function of the automatic nervous system is regulation of the internal environment by generally
involuntary controlling of smooth and cardiac muscles and organs of the digestive, cardiovascular,
excretory, and endocrine systems.
The somatic nervous system, or motor system, carries signals to skeletal muscles via neurons, mainly in
response to external stimuli. It if often considered voluntary because it is subject to conscious control.
4. Describe the embryonic development of the vertebrate brain.
Three anterior bulges of the neural tube-- the forebrain, the midbrain, and the hindbrain-- arise as the
embryo develops, with five brain regions appearing by the 5th week of development. The most profound
changes occur in the epencephalon, which develops from the forebrain and then gives rise to the
cerebrum. From its expansion, the cerebral cortex forms to extend over and around much of the rest of the
brain as the outer portion of the cerebrum. From the diencephalon, which develops form the forebrain,
develops the thalamus, hypothalamus, and epithalamus. From the midbrain develops the mesencephalon,
and from their the midbrain part of the brainstem. From the Hindbrain develops the met encephalon,
which gives rise to the pons part of the brainstem and the cerebellum, and the myelencephalon which
gives rise to the medulla oblongata part of the brainstem.
5. Describe the structures and functions of the following brain regions: medulla oblongata, pons,
midbrain, cerebellum, thalamus, epithalamus, hypothalamus, and cerebrum.
Medulla Oblongata: Lower part of the brain stem. The medulla oblongata helps to coordinate large-scale
body movements and contains centers that control automatic, homeostatic functions such as breathing and
heart and blood vessel activity.
Pons: Middle part of the brain stem. The pons helps to coordinate large-scale body movements and also
participates in some of the activities controlled by the medulla, including regulation of breathing centers
in the medulla.
Midbrain: Topmost part of the brain stem. The midbrain contains centers for receiving and integrating
several types of sensory information and sends coded sensory information along neurons to specific
regions of the forebrain. In no mammalian vertebrates, portions of the midbrain form prominent optic
lobes that in some cases are the animal’s only visual centers. In mammals, the midbrain instead
coordinates visual reflexes.
Cerebellum: Coordinates movement and balance, while also receiving sensory information about the
position of joints and the length of muscles, as well as input from the auditory and visual systems. It also
monitors commands issued by the cerebrum, from where information first passes through the pons. The
cerebellum integrates this information as it carries out coordination and error checking during motor and
perceptual functions.
Thalamus: Main input center for sensory information going to the cerebrum, where incoming
information from all the senses is sorted and sent to the appropriate cerebral centers for further
processing. Receives input from the cerebrum and other parts of the brain that regulate emotion and
arousal. Formed by two masses.
Epithalamus: Includes the pineal gland, the source of melatonin, and once of several clusters of
capillaries that generate cerebrospinal fluid from the blood.
Hypothalamus: One of the most important brain regions for the control of homeostasis. Contains the
body’s thermostat and centers for regulating hunger, thirst, and many other basic survival mechanisms.
The source of posterior pituitary hormones and of releasing hormones that act on the anterior pituitary.
Plays a role ins sexual and mating behavior, the fight-or-flight response, and pleasure.
Cerebrum: Center of information processing. Divided into right and left cerebral hemispheres, with each
containing an outer covering of gray matter; the cerebral cortex; internal white matter; and the basal
nuceli. The cerebral cortex in mammals is vital for perception, voluntary movement, and learning.
6. Describe the specific function of the reticular system.
The specific function of the reticular system is to act as a sensory filter, determining which incoming
information reaches the cerebral cortex and thereby controlling how alert or aware a person is.
7. Relate the specific regions of the cerebrum to their functions.
The cerebral cortex in mammals is vital for perception, voluntary movement, and learning. The corpus
callosum enables communication between the right and left cerebral cortices. The cerebral hemispheres
are the centers of information processing.
8. Distinguish between functions of the left and right hemispheres of the cerebrum.
The to hemispheres work together, trading information back and forth through the fibers of the corpus
callosum. Each hemisphere had sensory and motor connections to the opposite side of the body. The left
side is dominant with regard to language and more adept at math and logical operations. The right is
dominant in recognition of faces and patterns, spatial relations, and nonverbal thinking.
9. Describe the specific functions of the brain regions associated with language, speech, emotions,
memory, and learning.
Broca’s area in the front part of the primary motor cortex that controls muscles in the face, is active
during speech generation. Wernicke’s area of the left temporal lobe is active in the understanding of
speech. The limbic system, among many other regions of the brain, is involved in the genration and
experience of emotions. Structures within the limbic system have divers functions that include emotion,
motivation, olfaction, behavior, and memory. The limbic system often interacts with parts of the brain
outside of itself for emotions. Information storage in the cerebral cortex leads to the retaining of
memories. The hippocampus is essential for acquiriing but not marinating long-term memories, with
links in the hippocampus replaced by a more permanent connection within the cerebral cortex itself upon
the making of long-term memories. The focus of emotional memory is the amygdala.
10. Distinguish between long-term depression and long-term potentiation.
Long-term depression is major depressive disorder, where affected individuals undergo periods often
lasting months at a time of depression and lack of interest or pleasure. Long-term potentiation is a lasting
increase in rhe strength if synapse transmission, the alter to a synaptic connection that makes the flow of
communication more efficient and thereby crucial to the storage of memories and learning.
11. Describe our current understanding of the human consciousness.
Recent years have seen increased study of consciousness using brain-imaging techniques such as fMRI
and PET scans, making it possible to compare activity in the human brain during different states of
consciousness. Support is growing for the hypothesis that consciousness is an emergent property of the
brain involving many activities in the cerebral cortex. No “conscious center” has been found in the brain,
but described instead are how neuronal activity correlates with conscious experience.
12. Explain how research on stem cells and neutral development may lead to new treatments for injury
and disease.
Research on stem cells and neutral development may lead to new treatments for injury and disease, as the
identification of genes that cause or contribute to the disorders of the nervous system may help identify
causes, predict outcomes, and develop effective treatments. The possibility of repairing a damaged or
diseased brain with new nerve cells has launched a major current research effort to find ways to replace
brain tissue that has ceased to function properly and thereby offer cures to irreversible diseases like
Alzhemier’s.
Key Terms:
Nerve net  Weblike system of a series of interconnected nerve cells and neurons that controls the
contraction and expansion of the gastrovascular cavity in radially symmetrical animals like the hydra and
other cnidarians (the simplest animals with nervous systems).
Cephalization  Evolutionary trend toward the concentration of sensory neurons and interneurons at the
front end of the body, often with one or more nerve cords extending to the back end of the body
connecting these structures with nerves elsewhere in the body. Since nervous system organization within
an animal group often correlates with lifestyle, animals with elongated, bilaterally symmetrical bodies and
specialized nervous systems exhibit cephalization.
Nerve cords  Single tract of nerve tissue (made up of nerves, the axons of multiple nerve cells bundled
together) that constitutes the central nervous system of chordates (vertebrates or one of closely related
invertebrates) and develops into the spinal cord and brain in vertebrates.
Central Canal  Narrow cavity at the center of the spinal cord that is continuous with the fluid-filled
ventricles of the brain. Developed from the hollow cavity of the embryonic nerve cord during
development.
Ventricle  Space in the vertebrate brain that is filled with cerebrospinal fluid. Developed from the
hollow cavity of the embryonic nerve cord during development.
Cerebrospinal Fluid  Fluid formed by filtration of arterial blood in the brain that surrounds, nourishes,
and cushions the brain and spinal cord, protecting them from infection.
White matter  Tracts of axons within the central nervous system that consists of bundled up axons that
have myelin sheaths, giving the axons a whitish appearance. In the spinal cord, white matter lies on the
outside and functions in linking the CNS to sensory and motor neurons of the peripheral nervous system.
In the brain, it is located on the inside and functions in signaling between neurons of the brain in learning,
feeling emotions, processing sensory information, and generating commands.
Gray matter  Regions of dendrites and clustered neuron bodies within the central nervous system,
consisting mainly of neuron cell bodies, dendrites, and unmediated axons.
Cranial nerves  A nerve that originates in the brain and connects it to an organ of the head or upper
body. Most contain afferent and efferent neurons, though some are afferent only.
Spinal nerve  A nerve that carries signals to or from the spinal cord in the vertebrate peripheral nervous
system. Contains both afferent and efferent neurons.
Sensory division  Afferent PNS neurons that conduct action potentials toward the central nervous
system, bringing information from the peripheral nervous system to the CNS.
Motor Division  Efferent PNS neurons that conduct action potentials away from the CNS, sending
instructions from the CNS to muscles, glands, and endocrine cells.
Somatic nervous system  Portion of the nervous system responsible for voluntary body movement
(though much skeletal muscle activity is actually controlled by the brain stem or by reflexes mediated by
the spinal cord) and for sensing external stimuli, controlling the five senses. It consists of neurons that
carry signals to skeletal muscles. Also called the motor system.
Automatic nervous system  Portion of the nervous system responsible for regulation of the internal
environment by controlling the smooth and cardiac muscles and organs of the digestive, cardiovascular,
excretory, and endocrine systems. The control is generally involuntary. Consists of the sympathetic,
parasympathetic, and enteric divisions
Sympathetic division  One of the three divisions of the automatic nervous system of vertebrates;
generally increases energy expenditure and prepares the body for action.
Parasympathetic division  One of the three divisions of the automatic nervous system of vertebrates;
generally enhances body activities that gain and conserve energy, such as digestion and reduced heart
rate.
Forebrain  One of three ancestral and embryonic regions of the vertebrate brain; develops into the
thalamus, hypothalamus, and cerebrum.
Midbrain  One of three ancestral and embryonic regions of the vertebrate brain; develops into sensory
integrating and relay centers that send sensory information to the cerebrum.
Hindbrain  One of three ancestral and embryonic regions of the vertebrate brain; develops into the
medulla oblongata, pons, and cerebellum.
Cerebrum  The dorsal portion of the vertebrate forebrain, composed of right and left hemispheres; the
integrating center for memory, learning, emotions, and other highly complex functions of the central
nervous system.
Cerebral cortex  The surface of the cerebrum; the largest and most complex part of the mammalian
brain, containing nerve cell bodies of the cerebrum; the part of the vertebrate brain most changed during
evolution.
Medulla oblongata  The lowest part of the vertebrate brain, commonly called the medulla; a swelling of
the hindbrain in the front of the spinal cord that controls the autonomic, homeostatic functions, including
breathing, heart and blood vessel activity, swallowing, digestion, and vomiting.
Medulla  Term for the medulla oblongata. /See above/
Pons  Portion of the brain that participates in certain automatic, homeostatic functions, such as
regulating the breathing centers in the medulla.
Reticular formation  A diffuse network in the core of the brainstem that acts as a regulator controlling
arousal and sleep. Acting as a sensory filter, it determines which incoming information reached the
cerebral cortex and thereby controls how alert and aware a person is.
Electroencephalogram (EEG)  A record of the electrical impulses that travel through heart muscle
during the cardiac cycle.
Cerebellum  Part of the vertebrate hindbrain located dorsally; functions in unconscious coordination of
movement and balance.
Epithalamus  One of the three adult brain regions that developed from the earliest evolved forebrain
division the embryonic diencephalon. It includes the pineal gland, the source of melatonin, and also
contains one of several clusters of capillaries that generate cerebrospinal fluid from blood.
Thalamus  The main input center for sensory information going to the cerebrum and one of two major
integrating centers of the vertebrate forebrain, formed by to masses. The thalamus sorts incoming
information from all the senses and sends them to the appropriate cerebral centers for further processing,
while also receiving input from the cerebrum and other parts of the brain that regulate emotion and
arousal.
Hypothalamus  The ventral part of the vertebrate forebrain; functions in maintaining homeostasis,
especially in coordinating the endocrine and nervous systems; secretes hormones of the posterior pituitary
and releasing factors that regulate the anterior pituitary. The hypothalamus contains the body’s
thermostat, centers for regulating hunger, thirst, and many other basic survival mechanisms; and plays a
role in sexual and mating behaviors, the fight-or-flight response, and pleasure.
Biological clock  Molecular mechanism that directs periodic gene expression and cellular activity,
acting as an internal timekeeper controlling an organism’s biological rhythms. The biological clock,
crucial to circadian rhythm in mammals, is typically synchronized to cycles of light and dark in the
environment but maintains a roughly 24-hour cycle even in the absence of environmental cues.
Suprachiasmatic nuclei (SCN)  A group of neurons in the hypothalamus that acts as a pacemaker in
response to transmission of sensory information by the eyes, synchronizing the biological clock in cells
throughout the body to the natural cycles of day length and thus coordinating circadian rhythms.
Cerebral hemispheres  The right or left side of the cerebrum of the brain.
Basal nuclei  A group of neurons that are located deep within the white matter of a cerebral hemisphere
and function as important center for planning and learning movement sequences.
Neocortex  The outermost part of the cerebral cortex in humans, consisting of six parallel layers of
neurons arranged tangential to the brain surface.
Corpus callosum  The thick band of nerve fibers and axons that connects the right and left cerebral
hemispheres in mammals, enabling the hemispheres to process information together and communicate.
Limbic system  A group of structures surrounding the brainstem in mammals and is contained in a
region of the brain that is involved in the generation and experience of emotions. The limbic system
includes the amygdala, the hippocampus, and parts of the thalamus. Structures within it have different
functions including emotion, motivation, olfaction, behavior, and memory.
Short-term memory  The ability to hold information, anticipations, or goals for a time and then release
them if they become irrelevant.
Long-term memory  The ability to hold, associate, and recall information over one’s lifetime.
Long-term depression (LTD)  Chronic major depressive disorder that may last for many months
characterized by a depressed mood and abnormalities in sleep, appetite, and energy level.
Long-term potentiation (LTP)  An enhanced responsiveness to action potential (nerve signal) by a
receiving neuron, resulting in a lasting increase in the strength of synapse transmission and making the
flow of communication more efficient.
Growth cone  A highly motile specialized structure at the tip of the extending axon that explore the
extra cellular environment, determines the direction of growth, and then guides the extension of the axon
in that direction.