Chapter 14 Lecture & Lab Slides.pptx

BRAIN AND CRANIAL NERVES LEARNING OBJECTIVES FOR CHAPTER 14 Identical or similar figures from the textbook will appear on lecture exams 1. Understand the development of the brain. Page 494 2. Understand the differences between gray matter and white matter. 3. Understand the components of the cerebru...

BRAIN AND CRANIAL NERVES LEARNING OBJECTIVES FOR CHAPTER 14 Identical or similar figures from the textbook will appear on lecture exams 1. Understand the development of the brain. Page 494 2. Understand the differences between gray matter and white matter. 3. Understand the components of the cerebrum. Pages 512-514 4. Know the functions and locations of the functional areas of the cerebrum. Pages 517-521 5. Understand cerebral (hemispheric) lateralization. Pages 521-522 6. Identify and understand the function of cerebral white matter and cerebral nuclei. Page 514-516. 7. Identify and understand the components of the diencephalon and brainstem. Know the functions of the components of the diencephalon and brainstem. Pages 502-505; 509-512 8. Know the functions and components of the limbic system. Know the location and functions of the reticular formation. Pages 505-507; 516-517 9. Identify and understand cranial nerves. Know the functions and components of cranial nerves. Pages 524537 DEVELOPMENT OF THE BRAIN  Three primary brain vesicles develop into five secondary brain vesicles  Five secondary vesicles eventually form all four regions of the adult brain (cerebrum, diencephalon, brainstem & cerebellum) 1. Prosencephalon/forebrain develops into the telencephalon and the diencephalon. The telencephalon forms the cerebrum while the diencephalon forms the epithalamus, thalamus and hypothalamus 2. Mesencephalon/midbrain develops into a secondary brain vesicle but is still called the mesencephalon. The mesencephalon forms the midbrain 3. Rhombencephalon/hindbrain develops into the metencephalon and the myelencephalon. The metencephalon forms the pons and cerebellum while the myelencephalon forms the medulla oblongata TERMINOLOGY 1. Gray matter – derives its color from cell bodies and dendrites of neurons as well as unmyelinated axons that compose it; serves as integrating and processing areas CNS structures that are comprised of gray matter are often designated as: a. Cortex or area – superficial layer of gray matter ex. cerebral cortex b. Nucleus or center – cluster of neuronal cell bodies that are close to the surface or deep within the brain ex. cerebral nuclei 2. White matter – derives its color from the bundles of myelinated axons (tracts) that compose it; relays nerve signals CNS structures that are comprised of white matter are: a. Tracts – share a common origin and destination CEREBRUM The functions of the cerebrum are: 1. Center of intelligence – location of all complex intellectual functions 2. Control of voluntary movement – initiates and coordinates motor output 3. Conscious perception of senses – processes sensory input 4. Memory storage  There are three distinct region of the cerebrum: 1. Cerebral cortex – surface layer of gray matter of the cerebrum 2. Cerebral white matter 3. Cerebral nuclei – internal, deep gray matter within the cerebrum FUNCTIONAL AREAS OF THE CEREBRUM   Specific structural areas of the cerebral cortex have distinct motor and sensory functions Areas that perform more complex processing of sensory or motor information are dispersed over larger areas of cerebral cortex MOTOR AREAS 1. Primary motor cortex – controls voluntary skeletal muscle activity; located within precentral gyrus 2. Broca’s area (motor speech area) – controls muscular movements that are necessary for vocalization; located within the frontal lobe SENSORY AREAS 3. Primary somatosensory cortex – receives, processes and stores somatic sensory information; located within postcentral gyrus 4. Primary visual cortex – receives, processes and stores incoming visual information; located within occipital lobe 5. Primary auditory cortex – receives, processes and stores auditory information; located within temporal lobe 6. Primary olfactory cortex – receives, processes and stores olfactory information; located within temporal lobe FUNCTIONAL AREAS OF THE CEREBRUM ASSOCIATION AREAS 1. Premotor cortex – coordinates learned, skilled motor activities; located within frontal lobe 2. Somatosensory association area – interprets sensations to determine the texture, temperature, pressure and shape of objects; located within parietal lobe 3. Wernicke’s area – recognizes and comprehends spoken or written language; located within parietal and temporal lobes  Wernicke’s area and Broca’s speech area must work together for fluent communication to occur https://www.youtube.com/watch?v=szCeRbiEk6A 4. Prefrontal cortex – associated with many higher intellectual functions like complex thought, judgement, expression of personality, planning future behaviors and decision making; located within frontal lobe HEMISPHERIC LATERALIZATION  Specialization of each cerebral hemisphere for certain tasks LEFT CEREBRAL HEMISPHERE  Categorical hemisphere  Specialized for language abilities - contains Broca’s speech area and Wernicke’s area; damage results in aphasia  Important for performing sequential and analytical reasoning tasks like those required in science and mathematics  Control skeletal muscle on right side of body  Receives somatosensory information from right side of the body RIGHT CEREBRAL HEMISPHERE     Representational hemisphere Seat of imagination and insight Musical and artistic skill Perception of patterns and spatial relationships CEREBRAL WHITE MATTER OF THE  CEREBRUM Composed mainly of myelinated axons that are grouped into bundles called tracts There are three types of white matter tracts: 1. Association tracts – connect different regions of cerebral cortex within the same hemisphere 2. Commissural tracts – extend between the cerebral hemispheres. Ex. corpus callosum, anterior commissure and posterior commissure 3. Projection tracts – link the cerebral cortex to both the inferior brain regions and the spinal cord. Ex. internal capsule CEREBRAL NUCLEI  Also called basal nuclei/corpus striatum a. help regulate initiation and termination of movements b. inhibit unwanted movements c. regulate muscle tone DIENCEPHALON  Has three parts called the epithalamus, thalamus and hypothalamus EPITHALAMUS 1. Pineal gland – secretes melatonin which helps to regulate the body’s circadian rhythms 2. Habenular nuclei – involved in visceral and emotional responses to odors THALAMUS a. Principal and final relay point for incoming sensory information that is processed and then projected to the appropriate lobe of the cerebral cortex b. Maintains consciousness DIENCEPHALON HYPOTHALAMUS a. Controls the autonomic nervous system b. Controls the endocrine system c. Establishes circadian rhythms d. Regulation of body temperature e. Control of food and water intake f. Control of emotional behavior 1. Mammillary bodies – direct sensations related to olfaction BRAINSTEM  The midbrain, pons and medulla oblongata form the brainstem MIDBRAIN  Houses the nuclei of cranial nerves III and IV  Cerebral peduncles are motor tracts  Corpora quadrigemina (tectum or tectal plate) contains two pairs of sensory nuclei called the superior colliculi and inferior colliculi 1. Superior colliculi – visual reflex centers that help visually track moving objects, scan stationary objects and control reflexes such as turning eyes and head in response to a visual stimulus https://www.youtube.com/watch?v=T2zjlB4 2. Inferior colliculi – auditory reflex centers that control reflexive turning of the eyes and head in the direction of a sound (startle reflex) BRAINSTEM PONS  Houses the nuclei of cranial nerves V, VI, VII and VIII  Houses the pontine respiratory center 1. Pontine respiratory center – regulates breathing rate MEDULLA OBLONGATA  Houses the nuclei of cranial nerves VIII, IX, X, XI and XII  Pyramids are motor tracts  The decussation of the pyramids results in each cerebral hemisphere controlling the voluntary movements of the opposite side of the body 1. Cardiovascular center – regulates heart rate and force of contraction of the heart; controls CEREBELLUM  Second largest part of the brain; little brain  Has surface folds comprised of gray matter called folia  Has an internal region of white matter called the arbor vitae Functions of the Cerebellum a. Helps maintain posture and balance b. Fine tunes skeletal muscle contractions c. May play a role in cognition and language processing FUNCTIONAL BRAIN SYSTEMS  The brain has two functional brain systems  They are considered functional brain systems because their structures are not confined to one major region of the brain  The limbic system and the reticular formation are functional brain systems LIMBIC SYSTEM  Also called the emotional brain  Comprised of olfactory bulbs, olfactory tracts, mammillary bodies, habenular nuclei, fornix (a thin white matter tract) and many other structures a. Governs emotional behavior FUNCTIONAL BRAIN SYSTEMS RETICULAR FORMATION  Netlike arrangement of tracts and nuclei located in the brainstem  Contains a motor component a. helps regulate muscle tone  Contains a sensory component called the reticular activating system (RAS) Functions of the RAS a. keeps us in a state of mental alertness (consciousness) b. arouses us from sleep c. prevents sensory overload CRANIAL NERVES  There are twelve pairs of cranial nerves  Cranial nerves are designated with both a number (roman numerals) and a name (generally has some relation to its function)  The names of the cranial nerves are remembered by the mnemonic, Oh Oh Oh To Touch And Feel Very Green Vegetables AH! The components of the cranial nerves are remembered by the mnemonic, Some Say Money Matters But My Brother Says Better Brains Matter More https://www.youtube.com/watch?v=GJBnwZQ60  Ss CRANIAL NERVES CN I – OLFACTORY NERVE  Olfaction – conducts smell sensation from nose to brain  Sensory CN II – OPTIC NERVE  Vision – conducts visual information from the retina of the eye to the brain  Sensory CRANIAL NERVES CN III – OCULOMOTOR NERVE  Eyeball movement – innervates four (out of six) extrinsic eye muscles (superior rectus, inferior rectus, medial rectus and inferior oblique)  Pupillary constriction  Lens accommodation  Motor CN IV – TROCHLEAR NERVE  Eyeball movement – innervates one of the six extrinsic eye muscles (superior oblique)  Motor CN VI – ABDUCENS NERVE  Eyeball movement – innervates one of the six extrinsic eye muscles (lateral rectus)  Motor CRANIAL NERVES CN V – TRIGEMINAL NERVE  Receives touch, pain and thermal sensations from face, scalp and oral cavity  Chewing – innervates muscles of mastication  Mixed CN VII – FACIAL NERVE  Receives taste sensations from anterior two-thirds of tongue  Innervate the muscles of facial expression  Increases secretion of tears and saliva  Mixed CRANIAL NERVES CN VIII – VESTIBULOCOCHLEAR NERVE  Equilibrium – transmits information about balance from inner ear to brain  Hearing – transmits auditory sensations from inner ear to brain  Sensory CN IX – GLOSSOPHARYNGEAL NERVE  Transmits taste sensations from posterior onethird of the tongue  Swallowing – innervates pharynx  Increases secretion of saliva  Mixed CRANIAL NERVES CN X – VAGUS NERVE Transmits taste sensations from epiglottis  Relays sensory information from thoracic and abdominal viscera  Control smooth muscle in thoracic and abdominal organs  Controls cardiac muscle of the heart  Swallowing – innervates muscles of pharynx  Vocalizing - innervates muscles of larynx  Mixed  CN XI – ACCESSORY NERVE Movement of head and pectoral girdle – innervates trapezius and sternocleidomastoid muscles  Motor  CN XII – HYPOGLOSSAL NERVE THE END