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An Introduction to the Brain and Cranial Nerves
The Adult Human Brain Ranges from 750 cc to 2100 cc Contains almost 97% of the body’s neural tissue Average weight about 1.4 kg (3 lb) Male versus Female
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14-1 The Brain Six Regions of the Brain Cerebrum Cerebellum
Diencephalon Mesencephalon Pons Medulla oblongata
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14-1 The Brain Cerebrum Largest part of brain
Controls higher mental functions Divided into left and right cerebral hemispheres Surface layer of gray matter (neural/cerebral cortex)
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14-1 The Brain Cerebellum Second largest part of brain
Coordinates repetitive body movements Two hemispheres Covered with cerebellar cortex
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Figure 14-1 An Introduction to Brain Structures and Functions
Left cerebral hemisphere Gyri CEREBRUM Sulci • Conscious thought processes, Fissures intellectual functions • Memory storage and processing • Conscious and subconscious regulation of skeletal muscle contractions CEREBELLUM • Coordinates complex Spinal cord somatic motor patterns • Adjusts output of other somatic motor centers in brain and spinal cord 5
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14-1 The Brain Diencephalon Located under cerebrum and cerebellum
Links cerebrum with brain stem Three divisions of the diencephalon Left thalamus Right thalamus Hypothalamus
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14-1 The Brain Diencephalon Thalamus
Relays and processes sensory information Hypothalamus Hormone production Emotion Autonomic function
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14-1 The Brain Diencephalon Pituitary gland Major endocrine gland
Connected to hypothalamus Via infundibulum (stalk) Interfaces nervous and endocrine systems; example, Fight or Flight
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14-1 The Brain The Brain Stem Processes information between:
Spinal cord and cerebrum or cerebellum The brain stem is made up of the following 3 parts: Midbrain Pons Medulla oblongata
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14-1 The Brain Midbrain Pons Also called mesencephalon
Processes sight, sound, and associated reflexes Maintains consciousness; sleep Pons Connects cerebellum to brain stem Is involved in somatic and visceral motor control
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14-1 The Brain Medulla Oblongata Connects brain to spinal cord
Relays information Regulates autonomic functions Heart rate, blood pressure, and digestion
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Figure 14-1 An Introduction to Brain Structures and Functions
DIENCEPHALON THALAMUS • Relay and processing centers for sensory information HYPOTHALAMUS • Centers controlling emotions, autonomic functions, and hormone production MIDBRAIN Brain stem • Processing of visual and auditory data • Generation of reflexive somatic motor responses • Maintenance of consciousness PONS • Relays sensory information to cerebellum and thalamus • Subconscious somatic and visceral motor centers MEDULLA OBLONGATA • Relays sensory information to thalamus and to other portions of the brain stem • Autonomic centers for regulation of visceral function (cardiovascular, respiratory, and digestive system activities) 12
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14-1 The Brain The Brain The brain is a large, delicate mass of neural tissue Containing internal passageways and chambers filled with cerebrospinal fluid Each of the six major brain regions has specific functions Ascending from the medulla oblongata to the cerebrum, brain functions become more complex and variable Conscious thought and intelligence Are produced in the neural cortex of the cerebral hemispheres
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14-3 The Medulla Oblongata
Allows brain and spinal cord to communicate Coordinates complex autonomic reflexes Controls visceral functions: Cardiovascular centers and Respiratory rhythmicity centers Nuclei in the Medulla Autonomic nuclei control visceral activities Sensory and motor nuclei of cranial nerves Relay stations along sensory and motor pathways
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14-4 The Pons The Pons Sensory and motor nuclei of cranial nerves (V, VI, VII, VIII) Nuclei involved with respiration Apneustic center and pneumotaxic center Modify respiratory rhythmicity center activity Nucei that process and relay information to and from cerebellum Ascending, descending, and transverse tracts Transverse fibers (axons) Link nuclei of pons with opposite cerebellar hemisphere
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14-5 The Cerebellum Functions of the Cerebellum
Adjusts postural muscles Fine-tunes conscious and subconscious movements Disorders of the Cerebellum: Ataxia Damage from trauma or stroke Intoxication (temporary impairment) Disturbs muscle coordination
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Table 14-4 Components and Functions of the Midbrain
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14-7 The Diencephalon The Diencephalon
Integrates sensory information and motor commands Thalamus, epithalamus, and hypothalamus The pineal gland Found in posterior epithalamus Secretes hormone melatonin
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14-7 The Diencephalon The Thalamus
Filters ascending sensory information for primary sensory cortex Relays information between basal nuclei and cerebral cortex
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14-7 The Diencephalon Five Groups of Thalamic Nuclei Anterior group
Anterior nuclei Part of limbic system (emotions) Medial group Provides awareness of emotional states Ventral group Relays sensory information
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14-7 The Diencephalon Five Groups of Thalamic Nuclei Posterior group
Pulvinar nucleus (sensory) Lateral geniculate nucleus (visual) Medial geniculate nucleus (auditory) Lateral group Affects emotional states Integrates sensory information
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14-7 The Diencephalon Eight Functions of the Hypothalamus
Provides subconscious control of skeletal muscle Controls autonomic function Coordinates activities of nervous and endocrine systems Secretes hormones Antidiuretic hormone (ADH) by supraoptic nucleus Oxytocin (OT; OXT) by paraventricular nucleus
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14-7 The Diencephalon Eight Functions of the Hypothalamus
Produces emotions and behavioral drives The feeding center (hunger) The thirst center (thirst) Coordinates voluntary and autonomic functions Regulates body temperature Preoptic area of hypothalamus Controls circadian rhythms (day–night cycles) Suprachiasmatic nucleus
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14-8 The Limbic System Is a functional grouping that:
Establishes emotional states Links conscious functions of cerebral cortex with autonomic functions of brain stem Facilitates memory storage and retrieval Stimulation or inhibition affects emotions (rage, fear, pain, sexual arousal, pleasure) Amygdaloid body: Acts as interface between the limbic system, the cerebrum, and various sensory systems
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14-9 The Cerebrum The Cerebrum Is the largest part of the brain
Controls all conscious thoughts and intellectual functions Processes somatic sensory and motor information
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14-9 The Cerebrum Three Functional Principles of the Cerebrum
Each cerebral hemisphere receives sensory information from, and sends motor commands to, the opposite side of the body The two hemispheres have different functions, although their structures are alike Correspondence between a specific function and a specific region of cerebral cortex is not precise
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14-9 The Cerebrum Functions of Basal Nuclei Involved with:
The subconscious control of skeletal muscle tone The coordination of learned movement patterns (walking, lifting)
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14-9 The Cerebrum Motor and Sensory Areas of the Cortex
Central sulcus separates motor and sensory areas Motor areas Precentral gyrus of frontal lobe Directs voluntary movements Primary motor cortex Is the surface of precentral gyrus Pyramidal cells Are neurons of primary motor cortex
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14-9 The Cerebrum Motor and Sensory Areas of the Cortex Sensory areas
Postcentral gyrus of parietal lobe Receives somatic sensory information (touch, pressure, pain, vibration, taste, and temperature) Primary sensory cortex Surface of postcentral gyrus
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14-9 The Cerebrum Special Sensory Cortexes Visual cortex
Information from sight receptors Auditory cortex Information from sound receptors Olfactory cortex Information from odor receptors Gustatory cortex Information from taste receptors
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14-9 The Cerebrum Association Areas Sensory association areas
Monitor and interpret arriving information at sensory areas of cortex Somatic sensory association area Interprets input to primary sensory cortex (e.g., recognizes and responds to touch)
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14-9 The Cerebrum Sensory Association Areas Visual association area
Interprets activity in visual cortex Auditory association area Monitors auditory cortex Somatic motor association area (premotor cortex) Coordinates motor responses (learned movements)
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14-9 The Cerebrum Integrative Centers
Are located in lobes and cortical areas of both cerebral hemispheres Receive information from association areas Direct complex motor or analytical activities like consequences, pro’s and con’s, action versus reaction, predictions, etc…
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14-9 The Cerebrum General Interpretive Area
Also called Wernicke’s area Present in only one hemisphere Receives information from all sensory association areas Coordinates access to complex visual and auditory memories Where spoken language is understood
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14-9 The Cerebrum Other Integrative Areas Speech center
Is associated with general interpretive area Coordinates all vocalization functions Prefrontal cortex of frontal lobe Integrates information from sensory association areas Performs abstract intellectual activities (e.g., predicting consequences of actions)
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Table 14-8 The Cerebral Cortex
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14-9 The Cerebrum Hemispheric Lateralization
Functional differences between left and right hemispheres Each cerebral hemisphere performs certain functions that are not ordinarily performed by the opposite hemisphere
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14-9 The Cerebrum The Left Hemisphere The Right Hemisphere
In most people, left brain (dominant hemisphere) controls: Reading, writing, and math Decision making Speech and language The Right Hemisphere Right cerebral hemisphere relates to: Senses (touch, smell, sight, taste, feel) Recognition (faces, voice inflections)
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Figure 14-16 Hemispheric Lateralization
Left Cerebral Hemisphere LEFT HAND Prefrontal cortex Speech center C O R P U S Writing C A Auditory cortex L L O S U M General interpretive center (language and mathematical calculation) Visual cortex (right visual field) 39
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Figure 14-16 Hemispheric Lateralization
Right Cerebral Hemisphere RIGHT HAND Prefrontal cortex Anterior commissure C O R P U S Analysis by touch C A Auditory cortex L L O S U M Spatial visualization and analysis Visual cortex (left visual field) 40
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Monitoring Brain Activity
Brain activity is assessed by an electroencephalogram (EEG) Electrodes are placed on the skull and then patterns of electrical activity (brain waves) are printed out Four Categories of Brain Waves Alpha waves Beta waves Theta waves Delta waves
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14-9 The Cerebrum Alpha Waves Beta Waves
Found in healthy, awake adults at rest with eyes closed Beta Waves Higher frequency Found in adults concentrating or mentally stressed
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14-9 The Cerebrum Theta Waves Delta Waves Found in children
Found in intensely frustrated adults May indicate brain disorder in adults Delta Waves During sleep Found in awake adults with brain damage
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14-9 The Cerebrum Synchronization Seizure A pacemaker mechanism
Synchronizes electrical activity between hemispheres Brain damage can cause desynchronization Seizure Is a temporary cerebral disorder Changes the electroencephalogram Symptoms depend on regions affected
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