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Questions and Answers
What is the primary function of the primary motor cortex?
What is the primary function of the primary motor cortex?
Which type of fibers connect the cortices of the right and left cerebral hemispheres?
Which type of fibers connect the cortices of the right and left cerebral hemispheres?
Which motor planning area is involved in preparing for speech by planning movements of the mouth?
Which motor planning area is involved in preparing for speech by planning movements of the mouth?
What percentage of fibers decussate to form the lateral corticospinal tract?
What percentage of fibers decussate to form the lateral corticospinal tract?
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What role does the sensory association cortex play?
What role does the sensory association cortex play?
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Which area is primarily responsible for executive functions such as behavior control and memory processing?
Which area is primarily responsible for executive functions such as behavior control and memory processing?
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What aspect of motor activity does the supplementary motor cortex focus on?
What aspect of motor activity does the supplementary motor cortex focus on?
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What type of fibers unite the cortex with lower parts of the brain and the spinal cord?
What type of fibers unite the cortex with lower parts of the brain and the spinal cord?
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Study Notes
Cerebral Cortex
- The cerebral cortex is a vast collection of cell bodies, axons, and dendrites covering the surface of the cerebral hemispheres.
Gross Anatomy
- The frontal lobe is involved in motor speech (Broca's area).
- The temporal lobe is involved in processing auditory information.
- The parietal lobe is involved in reading comprehension and sensory speech.
- The occipital lobe processes visual information.
- The cerebellum and brainstem (pons and medulla oblongata) are also important parts of the brain.
Communication
- Commissural fibres connect the right and left cerebral hemispheres, and a major example of this is the corpus callosum.
- Projection fibres connect the cortex to lower brain structures and the spinal cord (afferent and efferent).
- Association fibres connect different regions within one hemisphere.
Inputs/Outputs
- The brain receives inputs and sends outputs.
Localized Function of Cerebral Cortex
- Primary sensory cortex discriminates sensory intensity and quality.
- Sensory association cortex performs complex sensory analysis.
- Primary motor cortex controls motor output (descending).
- Motor planning areas (Broca's, premotor, supplementary motor) control behaviour.
- Frontal association cortex integrates behaviour, emotions, memory.
Functional Areas of the Cerebral Cortex
- Different areas of the cortex are responsible for specific functions, such as primary motor cortex, primary somatosensory cortex, visual association area, etc.
Primary Motor Cortex (PMC)
- Located in the precentral gyrus anterior to the central sulcus.
- Controls contralateral voluntary movement, especially fine movements of the hand and face.
- Hand, foot, and lower face movements are entirely contralateral.
- Muscles active bilaterally are controlled by both sides of the PMC.
Homunculus
- The motor cortex has a map-like representation of the body—the homunculus—where different body parts are allocated different amounts of cortical space.
Sagital Section of Brain
- A sagittal view shows the brain's structure by sectioning it vertically from the front to the back.
Motor Planning Areas
- Supplementary motor cortex initiates internally generated, bimanual, and sequential movements.
- Pre-motor cortex controls trunk and girdle muscles, assisting in externally cued movements.
- Broca's area plans mouth movements for speech.
Pre-frontal Area
- The prefrontal cortex controls the decision to move by accessing and directing various motor centers.
Lateral CST
- Upper motor neurons in the primary motor cortex project down to the spinal cord.
- 90% of fibres decussate (cross over) to form the lateral corticospinal tract.
- Fibres that do not cross form the anterior corticospinal tract.
- Most corticospinal neurons synapse with interneurons, which then connect with motor neurons innervating the muscles.
Anterior CST
- The anterior corticospinal tract connects with trunk and axial muscles.
- Control is both ipsilateral and contralateral.
- Trunk muscles are typically bilaterally innervated.
Motor Unit
- A motor neuron and the muscle fibres it innervates comprise a motor unit.
Pathways
- Motor and sensory pathways exist in the spinal cord.
- Pyramids are parts of the brainstem.
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Description
This quiz covers the structure and functions of the cerebral cortex, including its lobes and their specific roles. Explore the anatomical details and communication pathways within the brain to deepen your understanding of neural functions.
