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

14-1 The Brain Six Regions of the Brain Cerebrum Cerebellum Diencephalon Mesencephalon Pons Medulla oblongata

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)

14-1 The Brain Cerebellum Second largest part of brain Coordinates repetitive body movements Two hemispheres Covered with cerebellar cortex

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

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

14-1 The Brain Diencephalon Thalamus Relays and processes sensory information Hypothalamus Hormone production Emotion Autonomic function

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

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

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

14-1 The Brain Medulla Oblongata Connects brain to spinal cord Relays information Regulates autonomic functions Heart rate, blood pressure, and digestion

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

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

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

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

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

Table 14-4 Components and Functions of the Midbrain 17

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

14-7 The Diencephalon The Thalamus Filters ascending sensory information for primary sensory cortex Relays information between basal nuclei and cerebral cortex

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

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

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

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

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

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

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

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)

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

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

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

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)

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)

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…

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

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)

Table 14-8 The Cerebral Cortex 36

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

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)

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

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

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

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

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

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