Transcript Unit One: Introduction to Physiology: The Cell and General

Chapter 57: Cerebral Cortex, Intellectual
Functions of the Brain, Learning, and Memory
Guyton and Hall, Textbook of Medical Physiology, 12 edition
Physiologic Anatomy of the Cerebral Cortex
• Three Types of Neurons
a. Granular (stellate)
1. Short axons
2. Function as interneurons
3. Excitatory with glutamate as neurotransmitter
4. Inhibitory with GABA as neurotransmitter
5. Found in the sensory areas of the cortex
6. Found in association areas between sensory
and motor areas
Physiologic Anatomy of the Cerebral Cortex
• Three Types of Neurons
b. Fusiform and Pyramidal
1. Give rise to almost all output fibers from the cortex
2. Pyramidal are larger and more numerous than
fusiform
3. Pyramidal-source of nerve fibers that go all the way
to the spinal cord
Physiologic Anatomy of the Cerebral Cortex
Fig. 57.1 Structure of the cerebral cortex, showing: I, molecular layer;
II, external granular layer; III, pyramidal layer; IV, internal granular
layer; V, large pyramidal cell layer; VI, layer of fusiform or polymorphic cells
Physiologic Anatomy of the Cerebral Cortex
• Anatomical and Functional Relations of the
Cerebral Cortex to the Thalamus and Other
Lower Centers
Fig. 57.2 Areas of the cerebral cortex that connect with specific
portions of the thalamus
Functions of Specific Cortical Areas
Fig. 57.3 Functional areas of the human cerebral cortex as determined by
electrical stimulation during neurological surgery or examination
Functions of Specific Cortical Areas
• Association Areas (see Fig. 57.4)
a. Parieto-occipitotemporal association area
1. Analysis of the spatial coordinates of the body
2. Wernicke’s Area-important for language
comprehension
3. Angular gyrus area-needed for reading
4. Area for naming objects
Functions of Specific Cortical Areas
• Association Areas (see Fig. 57.4)
b. Pre-frontal association area
1. Broca’s area-neural circuitary for word formation
c. Limbic association area-behavior, emotions, and
motivation
d. Area for recognition of faces
Functions of Specific Cortical Areas
Fig. 57.6
Functions of Specific Cortical Areas
• Comprehensive Interpretative Function of Wernicke’s
Area
Fig. 57.7
Functions of Specific Cortical Areas
• Comprehensive Interpretative Function of Wernicke’s
Area
a. Angular gyrus-interpretation of visual information
•
Concept of the Dominant Hemisphere
•
Role of Language in the Function of Wernicke’s Area
•
Functions of the Parieto-occipitotemporal Cortex in
the Nondominate Hemisphere
Functions of Specific Cortical Areas
• Higher Intellectual Functions of the Prefrontal
Association Areas
a. Decreased aggressiveness and inappropriate social
behavior
b. Inability to progress toward goals or carry through
sequential thoughts
c. Elaboration of thought-concept of a “working memory”
1. Functions of a working memory
Function of the Corpus Callosum
• Cutting the Corpus Callosum:
a. Blocks transfer of information from the dominant
hemisphere to the motor cortex on the opposite side
b. Prevents transfer of somatic and visual info from the
right to left hemisphere
c. Person would have two entirely separate conscious
portions of the brain
Thoughts, Consciousness, and Memory
• Memory-Roles of Synaptic Facilitation and Synaptic
Inhibition
a. Positive and negative memory—sensitization or
habituation of synaptic transmission
b. Classification of memories
1. Declarative
2. Skill
Thoughts, Consciousness, and Memory
• Declarative Memory- memory of the various details of
integrated thought (i.e. memory of surroundings,
time relationships, causes of experiences, meaning
of an experience)
• Skill Memory- associated with motor activities based
on previous learning (i.e. hitting a tennis ball)
Thoughts, Consciousness, and Memory
• Short-Term Memory
• Intermediate Long-Term Memory
a. Memory based on chemical changes in the presynaptic
terminal or postsynaptic neuronal membrane
Fig. 57.9
Thoughts, Consciousness, and Memory
• Molecular Mechanism of Intermediate Memory
a. Mechanism of habituation-role of calcium channels
b. Mechanism of facilitation-role of serotonin release
and cAMP activity
Thoughts, Consciousness, and Memory
• Long-Term Memory
a. Structural changes in synapses during the development
of long-term memory
1. Increase in vesicle release site for secretion of
transmitters
2. Increase in number of transmitter vesicles released
3. Increase in the number of presynaptic terminals
4. Changes in the structure of dendritic spines that
permit transmission of stronger signals
Thoughts, Consciousness, and Memory
• Long-Term Memory
b. Number of neurons and their connectivities change during
learning
•
Consolidation of Memory
a. Rehearsal enhances the transference of short-term memory
into long-term memory
b. New memories are codified during consolidation
Thoughts, Consciousness, and Memory
•
Consolidation of Memory
c. Roles of specific parts of the brain in the memory process
1. Hippocampus promotes storage of memories
2. Hippocampi not important in reflexive learning