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An Introduction to the Brain and Cranial Nerves
The Adult Human Brain Volume ranges from 750 mL to 2100 mL Contains almost 97 percent of the body’s neural tissue Average weight about 1.4 kg (3 lb)
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14-1 The Brain Six Regions of the Brain Cerebrum Cerebellum
Diencephalon Midbrain Pons Medulla oblongata
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Cerebellum Cerebrum Left cerebral hemisphere Gyri Sulci
Figure 14-1 An Introduction to Brain Structures and Functions (Part 1 of 2). Left cerebral hemisphere Gyri Cerebrum Sulci • Conscious thought processes, intellectual functions • Memory storage and processing • Conscious and subconscious regulation of skeletal muscle contractions Fissures Cerebellum • Coordinates complex somatic motor patterns • Adjusts output of other somatic motor centers in brain and spinal cord Spinal cord
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Diencephalon Midbrain Pons Medulla oblongata Thalamus
Figure 14-1 An Introduction to Brain Structures and Functions (Part 2 of 2). 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 date • 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)
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Figure 14-2a Ventricles of the Brain.
Cerebral hemispheres Lateral ventricles Interventricular foramen Third ventricle Cerebral aqueduct Fourth ventricle Pons Medulla oblongata Spinal cord Central canal Ventricles, lateral view a
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Figure 14-2b Ventricles of the Brain.
Cerebral hemispheres Ventricles of the Brain Lateral ventricles Interventricular foramen Third ventricle Cerebral aqueduct Fourth ventricle Central canal Cerebellum Ventricles, anterior view b
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Figure 14-3a The Relationship among the Brain, Cranium, and Cranial Meninges.
Dura mater (periosteal layer) Cranium Dural sinus Dura mater (meningeal layer) Subarachnoid space Pia mater Subdural space Arachnoid mater Cerebral cortex Cerebrum Cerebellum Medulla oblongata Spinal cord a A lateral view of the brain, showing its position in the cranium and the organization of the meninges
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Interstitial Fluid in thalamus Cerebrospinal Fluid in third ventricle
Figure 14-4 Formation and Circulation of Cerebrospinal Fluid (Part 1 of 3). Nutrients, O2 Interstitial Fluid in thalamus Capillaries Waste products, CO2 Neuron Astrocyte 1 The choroid plexus produces and maintains CSF. Two extensive folds of the choroid plexus originate in the roof of the third ventricle and extend through the interventricular foramina. These folds cover the floors of the lateral ventricles. In the inferior brain stem, a region of the choroid plexus in the roof of the fourth ventricle projects between the cerebellum and the pons. Choroid plexus ependymal cells Ependymal cells Removal of waste Production of CSF Cerebrospinal Fluid in third ventricle Tight junction Choroid plexus
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Figure 14-4 Formation and Circulation of Cerebrospinal Fluid (Part 2 of 3).
Choroid plexus of third ventricle Choroid plexus of fourth ventricle 2 The CSF circulates from the choroid plexuses through the ventricles and fills the central canal of the spinal cord. As it circulates, materials diffuse between the CSF and the interstitial fluid of the CNS across the ependymal cells. 3 The CSF reaches the sub- arachnoid space through two lateral apertures and a single median aperture in the roof of the fourth ventricle. Spinal cord Central canal 4 Cerebrospinal fluid then flows through the subarachnoid space surrounding the brain, spinal cord, and cauda equina. Dura mater Cauda equina Arachnoid mater Filum terminale
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Superior sagittal sinus
Figure 14-4 Formation and Circulation of Cerebrospinal Fluid (Part 3 of 3). Dura mater (periosteal layer) Arachnoid granulation Arachnoid trabecula Cranium CSF fluid movement Superior sagittal sinus Dura mater (meningeal layer) Subdural space Arachnoid mater Cerebral cortex Subarachnoid space Pia mater 5 Fingerlike extensions of the arachnoid membrane, called the arachnoid villi, penetrate the meningeal layer of the dura mater and extend into the superior sagittal sinus. In adults, these extensions form large arachnoid granulations. CSF is absorbed into the venous circulation at the arachnoid granulations.
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Figure 14-5a The Diencephalon and Brain Stem.
Cerebral peduncle Thalamus Lateral geniculate nucleus Optic tract Medial geniculate nucleus Cranial nerves Midbrain N II Superior colliculus Inferior colliculus N III N IV Cerebellar peduncles Superior cerebellar peduncle N V Pons Middle cerebellar peduncle N VI N VII Inferior cerebellar peduncle N VIII N IX N X Medulla oblongata N XI N XII Spinal nerve C1 Spinal nerve C2 Spinal cord a Lateral view
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Figure 14-5b The Diencephalon and Brain Stem.
Optic chiasm Infundibulum Cranial nerves Thalamus N II Optic tract N III Cerebral peduncle N IV Mammillary body N V Pons N VI N VII N VIII N IX N X N XI N XII Medulla oblongata Ventral roots of spinal nerves C1 and C2 Spinal cord Anterior view b
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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 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
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Figure 14-13a The Brain in Lateral View.
Central sulcus Frontal lobe Parietal lobe Occipital lobe Lateral sulcus Temporal lobe Cerebellum Pons Medulla oblongata a Lateral view, cadaver brain
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Figure 14-13b The Brain in Lateral View.
Precentral gyrus Central sulcus Postcentral gyrus Frontal lobe Parietal lobe Occipital lobe Temporal lobe Lateral sulcus Cerebellum Pons Medulla oblongata b Lateral view
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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 White Matter of the Cerebrum Association fibers
Connections within one hemisphere Commissural fibers Bands of fibers connecting two hemispheres Projection fibers Connect cerebrum with lower areas
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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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Table 14-3 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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14-10 Cranial Nerves Cranial Nerves
12 pairs connected to brain Four Classifications of Cranial Nerves Sensory nerves: carriers of somatic sensory information, including touch, pressure, vibration, temperature, and pain Special sensory nerves: carriers of sensations such as smell, sight, hearing, and balance Motor nerves: axons of somatic motor neurons Mixed nerves: mixture of motor and sensory fibers
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14-10 Cranial Nerves Cranial Nerves
Are classified by primary functions May also have important secondary functions Distributing autonomic fibers to peripheral ganglia The 12 cranial nerve groups are identified by: Primary function Origin Pathway Destination
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Summary of Function of Cranial Nerves
Some Say Money Matter But My Brother Says Big Brains Matter Most Figure 13.5b
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Table 14-4 Cranial Nerve Branches and Functions (Part 1 of 2).
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Table 14-4 Cranial Nerve Branches and Functions (Part 2 of 2).
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