TABLE OF CONTENTS
KEY CONCEPTS IN THIS LECTURE 1. The nervous system consists of neurons which communicate information and glia which support and protect the neurons in various ways. The nervous system is divided in to the central nervous system, consisting of the brain and spinal cord which are responsible for integration, and the peripheral nervous system which transmits sensory input and executes central commands. 2. Development of the nervous system occurs following gastrulation with the formation of the neural tube, a derivative of the ectoderm. The anterior portion of the neural tube differentiates into the forebrain, midbrain, and hindbrain. Founder cells around the ventricle divide and eventually produce neurons, which migrate outward to the cortex, and differentiate into neuroblasts. They send out axons and then dendrites. Eventually they form numerous synapses, but only those forming useful connections survive. Neural circuitry, as is found in the columns of the primary visual cortex, is strongly influenced by use. 3. The central nervous system is protected by the skull, meninges, and fluid filled cavities containing cerebrospinal fluid. This fluid originates in the ventricular system of the brain. 4. The brain is highly organized with regard to function. Specific areas of the cerebrum are involved with processing sensory information and motor output. Many aspects of the cerebral cortex are mapped for function in a precise manner. Other parts of the cerebrum modulate motor output from the cerebral cortex while others, such as the limbic system, are involved in mediation of behavior and memory. 5. Integration of sensory input and motor output occurs in the brain stem as well. For example, the midbrain integrates auditory input and motor responses in the eye. The brain stem also contains specific pathways which move information from the spinal up to the brain and other descending pathways from the brain. 6. Although the cerebellum does not initiate motor commands, it is involved in modifying motor commands which arise from the motor cortices of the cerebrum. 7. The spinal cord also consists of specific ascending and descending nerve pathways which communicate information between the body and the brain. This structure is also involved in reflexes which are simple behaviors, such as the withdrawal reflex. 8. Although the general organization of the brain is similar in all vertebrates, there are wide differences between taxa in ability, and brain structure often reflects these functional differences. LECTURE OUTLINE I. GENERAL INTRODUCTION
A. The Nervous and Endocrine System
1. Some functions of the Nervous System
a. Regulation of physiology
b. Sensory input and motor output
c. Emotions, memory, reasoning, perceptions, etc.
B. Organization of the nervous system
1. Central Nervous System (CNS)/Peripheral Nervous System (PNS)
a. Afferents, interneurons, and efferents
C. Tissue Types in the Nervous System
1. Neurons--communication of information via action potentials
2. Glia--nutrition, support, insulation, phagocytosis, CSF production,
and neural development
II. EARLY DEVELOPMENT OF THE NERVOUS SYSTEM
A. Three germ layers form following gastrulation (endoderm, mesoderm,
ectoderm)
1. The neural plate forms from ectoderm and becomes the neural tube
a. Nervous system contains a fluid filled opening (to become
ventricles)
2. Early brain consists of forebrain, midbrain, and hindbrain
a. Further differentiation occurs into telencephalon, etc
B. Early Development of the CNS
1. Neuronal growth occurs from the ventricles outward to the cortex
2. Cell Division. Role of founder cells (stem cells) and radial glia
3. Migration of cells
4. Differentiation and formation of neurites via growth cones
5. Many synapses form but only those which are used survive
6. Pruning of many synapses and cell death occurs
C. Role of genes and environment in neural development
1. The mature neural network depends on use
a. Example: Development of wiring in the lateral geniculate
nucleus and primary visual cortex
2. There is some fluidity in neural development, especially during
early development
a. Example: Visual cortex is relocated following early ablation
3. Critical periods during development are also important
a. Imprinting is a narrow critical period
1) Example: Studies on geese by Lorenz
4. Both nature (genes) and nuture (environmental factors) program
neural development
III. PROTECTION AND NOURISHMENT OF THE CNS
A. CNS is well-protected from internal/external change
1. Blood brain barrier (BBB)--protection from toxins, etc.
2. Skull and vertebrae--protection from physical insults
3. Meninges--nourishment from blood and protection
4. Cerebrospinal Fluid (CSF)
IV. FUNCTIONAL ORGANIZATION OF THE BRAIN AND SPINAL CORD
A. Introduction: The CNS regulates physiology and is responsible
for behavior.
1. Example of how the brain controls behavior
2. General brain organization
a. Major divisions are the forebrain, midbrain, and hindbrain
b. Relationship to the human brain
B. The Brain: Form and Function
1. Cerebrum
a. Overall structure of the cerebrum (sulci and lobes)
b. Functional organization of the cortex (cortical lobes)
1) Spatial relationships reflect functional interaction
a) Broca's area is projects to the premotor cortex
b) Wernicke's area receives sensory input from visual
and auditory cortices as well as other brain areas
c) Example: Language involves many brain areas
2) Functional organization is conserved in mammals
a) What are the differences between these species?
c. Topographical mapping in somatomotor cortex, etc.
d. Basal ganglia (=basal nuclei) and how they function
1) Caudate, putamen, and globus pallidus
a) Caudate and putamen are also called the striatum
2) Pathways for the motor loop
2) Dysfunction: DA and Parkinson's Disease
e. Limbic system -- Emotions (e.g., aggression and fear), memory
acquisition, pleasure, etc.
1) Pathways of limbic system
2. Diencephalon (Thalamus and Hypothalamus)
a. Thalamus is a relay point (ascending paths)
b. Hypothalamus is important in homeostasis, reproduction,
and various behaviors
Example 1: Blood osmoticity--roles for the PVN and SON
Example 2: Hypothalamic-Hypophyseal Axis: Control of
reproduction
Example 3: Biological clock rests in the SCN
3. Cerebellum
a. Functional organization
1) Vestibulocerebellum (important in balance and eye/
head movements)
2) Spinocerebellum (monitoring and adjustment of voluntary behaviors)
3) Cerebrocerebellum (voluntary behavior; assists in planned
movements via the premotor cortex; behaviors that work
or don't work; ballistic behaviors)
b. Arbitrator of motor events
c. A general topographic map exists for control of motor events
1) Homunculi exist in the cerebellum **
4. Brainstem (Midbrain, Pons, and Medulla oblongata)
a. Site of Reticular Formation (RF)
1) Affects state of arousal (sleep-wake cycle,
hibernation cycle)
b. Midbrain acts as a relay station, as a point of integration for
sensory input (=tectum), and in perception of pain
1) Overlapping maps for visual, auditory, and somatosensory input
2) Multisensory neurons integrate more than one sensory input
c. Pons and Medulla -- relay station; site of regulatory centers *
d. Cranial nerves
1) Convey sensory inputs to and motor outputs from the brain
C. Spinal Cord
1. General organization: An extension of the brain
a. Organization of the spinal cord/Relationship to spinal nerves
2. Functions
a. Relays information to and from brain (more on this later)
1) Ascending and decending paths in the spinal cord
b. Spinal cord is also involved in various reflexes
1) Example 1: Withdrawal reflex (see Text)
2) Example 2: Crossed-extensor reflex
3) Example 3: Micturition reflex involves control from higher
centers ** **
V. FORM AND FUNCTION IN THE VERTEBRATE BRAIN (Skip 2008)
A. Introduction
1. Structural differences reflect functional differences--Darwin
a. Differences in mammalian forelimbs--a theme with variations
2. Basic organization of the vertebrate brain
a. Brain and spinal cord dorsally located, hollow.
b. Bilaterally symmetrical, but function can be confined to a
hemisphere
c. Hierarchical control
d. Localization of function
e. Layering of function
3. Quantitative differences in size often reflect functional differences
a. Comparison of human, cat, and rat brain
B. Evolution of the Vertebrate Brain
1. General evolution of vertebrates
2. Differences in brain form/function in the vertebrate classes
a. Aquatic verses terrestrial vertebrate classes
b. Birds and mammals--separate evolutionary lines
Anatomy
of the CNS. Beautiful, labelled photographs of the the Central Nervous
System from the University of Utah Medical School.
Early
Development of the CNS. A slide show that provides the highlights
of neural development. Go to: |
