Cerebral Cortex PDF

12/29/20 Cerebral Cortex Cerebral Cortex Assist. Prof. Dr. Cenk Serhan ÖZVEREL [email protected] • The cerebral cortex consists of folded bulges called gyri that create deep furrows or fissures called sulci. • Most highly developed part of brain • 80% of weight • thinking, perceiving,...

12/29/20 Cerebral Cortex Cerebral Cortex Assist. Prof. Dr. Cenk Serhan ÖZVEREL [email protected] • The cerebral cortex consists of folded bulges called gyri that create deep furrows or fissures called sulci. • Most highly developed part of brain • 80% of weight • thinking, perceiving, producing and understanding language. • Contains sensory and motor areas Cerebral Cortex • Sensory à receives inputs from thalamus à • visual cortex of the occipital lobe, • the auditory cortex of the temporal lobe, • the gustatory cortex, • the somatosensory cortex of the parietal lobe. • Most “voluntary” movements initiated by the cerebral cortex • Lower brain areas—the cord, brain stem, basal ganglia, and cerebellum. • Between 14 billion and 16 billion neurons are found in the cerebral cortex. • send specific control signals to the muscles. • Motor areas, including the primary motor cortex and the premotor cortex, regulate voluntary movement. 1 12/29/20 Motor Cortex and Corticospinal Tract • For a few types of movements, however, the cortex has almost a direct pathway to the anterior motor neurons of the cord, bypassing some motor centers on the way. • This is especially true for control of the fine dexterous movements of the fingers and hands. • Functional areas of the cerebral cortex • The motor cortex itself is divided into three subareas 1. primary motor cortex, 2. premotor area, 3. the supplementary motor area. Primary Motor Cortex • Different muscle areas of the body in the primary motor cortex 2 12/29/20 Some Specialized Areas of Motor Control Found in the Human Motor Cortex Broca’s Area and Speech. • Damage to it does not prevent a person from vocalizing but makes it impossible for the person to speak whole words rather than uncoordinated utterances or an occasional simple word such as “no” or “yes.” Wernicle’s Area • General Interpretative area • Highly developed • Greatest role in comprehension levels of brain function • INTELLIGENCE • When damaged, person may be unable to arrange words into coherent thought. • Dominant Hemispehere-à Wernickles area and angular gyrus are well developed. As well as the speech and motor control areas. (In one hemisphere) • 95% left hemisphere • Carpus Callosum Connect 2 hemispheres 3 12/29/20 • NONDOMINANT brain may be important for understanding, ınterpreting music, nonverbal visual experiences, significance of body language. “Voluntary” Eye Movement Field. Head Rotation Area. • premotor area • above Broca’s area • Slightly higher in the motor association area • Damage to this area prevents a person from voluntarily moving the eyes toward different objects. • electrical stimulation elicits head rotation 4 12/29/20 Area for Hand Skills. Transmission of Signals from the Motor Cortex to the Muscles • In the premotor area • immediately anterior to the primary motor cortex • when tumors or other lesions cause destruction in this area, hand movements become uncoordinated and nonpurposeful, a condition called motor apraxia. • Motor signals are transmitted directly from the cortex to the spinal cord through the corticospinal tract and indirectly through multiple accessory pathways that involve the basal ganglia, cerebellum, and various nuclei of the brain stem. Transmission of Signals from the Motor Cortex to the Muscles Role of the Brain Stem in Controlling Motor Function • Motor signals are transmitted directly from the cortex to the spinal cord through the corticospinal tract and indirectly through multiple accessory pathways that involve the basal ganglia, cerebellum, and various nuclei of the brain stem. • Consists of the medulla, pons, and mesencephalon. Discrete and detailed movements, especially of the distal segments of the limbs, particularly the hands and fingers. • it is an extension of the spinal cord upward into the cranial cavity because it contains motor and sensory nuclei that perform motor and sensory functions for the face and head regions in the same way that the spinal cord performs these functions from the neck down. 5 12/29/20 • But in another sense, the brain stem is its own master because it provides many special control functions, such as the following: 1. 2. 3. 4. 5. 6. • The brain stem serves as a way station for “command signals” from higher neural centers. Control of respiration Control of the cardiovascular system Partial control of gastrointestinal function Control of many stereotyped movements of the body Control of equilibrium Control of eye movements Support of the Body Against Gravity—Roles of the Reticular and Vestibular Nuclei • Excitatory-Inhibitory Antagonism Between Pontine and Medullary Reticular Nuclei • The reticular nuclei are divided into two major groups: • (1) pontine reticular nuclei, • (2) medullary reticular nuclei, • Two sets of nuclei à function antagonistically • Pontine exciting the antigravity muscles and the medullary relaxing these same muscles. 6 12/29/20 Vestibular Sensations and Maintenance of Equilibrium • Vestibular Apparatus • sensory organ for detecting sensations of equilibrium. • encased in a system of bony tubes and chambers located in the petrous portion of the temporal bone, called the bony labyrinth. • Within this system are membranous tubes and chambers called the membranous labyrinth. à functional part of the vestibular apparatus. Functions of Brain Stem Nuclei in Controlling Subconscious, Stereotyped Movements Functions of Brain Stem Nuclei in Controlling Subconscious, Stereotyped Movements • Rarely, a baby is born without brain structures above the mesencephalic region, a condition called anencephaly. • In addition, • Some of these babies have been kept alive for many months. They are able to perform some stereotyped movements forà • feeding, • such as suckling, • extrusion of unpleasant food from the mouth, • moving the hands to the mouth to suck the fingers. • they can yawn and stretch. • They can cry • They can follow objects with movements of the eyes and head. • Also, placing pressure on the upper anterior parts of their legs causes them to pull to the sitting position. • It is clear that many of the stereotyped motor functions of the human being are integrated in the brain stem. 7 12/29/20 The End 8