Class Notes (838,994)
Canada (511,159)
BIOB32H3 (80)


11 Pages
Unlock Document

Biological Sciences
Kenneth Welch

Central Nervous System (CNS) Central Nervous System (CNS) • CNS – composed of the brain and spinal cord • Cephalization • Elaboration of the anterior portion of the CNS • Increase in number of neurons in the head • Highest level has been reached in the human brain The Brain • Composed of wrinkled, pinkish gray tissue • Surface anatomy includes cerebral hemispheres, cerebellum, and brain stem Embryonic Development • During the first 26 days of development: • Ectoderm thickens along dorsal midline to form the neural plate • The neural plate invaginates, forming a groove flanked by neural folds • The neural groove fuses dorsally and forms the neural tube Primary Brain Vesicles • The anterior end of the neural tube expands and constricts to form the three primary brain vesicles • Prosencephalon – the forebrain • Mesencephalon – the midbrain • Rhombencephalon – hindbrain Secondary Brain Vesicles • In week 5 of embryonic development, secondary brain vesicles form: • Telencephalon and diencephalon arise from the forebrain • Mesencephalon remains undivided • Metencephalon and myelencephalon arise from the hindbrain Adult Brain Structures • Fates of the secondary brain vesicles: • Telencephalon – cerebrum: cortex, white matter, and basal nuclei • Diencephalon – thalamus, hypothalamus, and epithalamus • Mesencephalon – brain stem: midbrain • Metencephalon – brain stem: pons • Myelencephalon – brain stem: medulla oblongata Adult Neural Canal Regions • Adult structures derived from the neural canal • Telencephalon – lateral ventricles • Diencephalon – third ventricle • Mesencephalon – cerebral aqueduct • Metencephalon and myelencephalon – fourth ventricle Basic Pattern of the Central Nervous System • Spinal Cord • Central cavity surrounded by a gray matter core • External to which is white matter composed of myelinated fiber tracts • Brain • Similar to spinal cord but with additional areas of gray matter • Cerebellum has gray matter in nuclei • Cerebrum has nuclei and additional gray matter in the cortex Ventricles of the Brain • Arise from expansion of the lumen of the neural tube • The ventricles are: • The paired C-shaped lateral ventricles • The third ventricle found in the diencephalon • The fourth ventricle found in the hindbrain dorsal to the pons Cerebral Hemispheres • Form the superior part of the brain and make up 83% of its mass • Contain ridges (gyri) and shallow grooves (sulci) • Contain deep grooves called fissures • Are separated by the longitudinal fissure • Have three basic regions: cortex, white matter, and basal nuclei Major Lobes, Gyri, and Sulci of the Cerebral Hemisphere • Deep sulci divide the hemispheres into five lobes: • Frontal, parietal, temporal, occipital, and insula • Central sulcus – separates the frontal and parietal lobes • Parietal-occipital sulcus – separates the parieto and occipital lobes • Lateral sulcus – separates the parietal and temporal lobes • The precentral and postcentral gyri border the central sulcus Cerebral Cortex • The cortex – superficial gray matter; accounts for roughly 40% of the mass of the brain • It enables sensation, communication, memory, understanding, and voluntary movements • Each hemisphere acts contralaterally (controls the opposite side of the body) • Hemispheres are not equal in function • No functional area acts alone; conscious behavior involves the entire cortex Functional Areas of the Cerebral Cortex • Three types of functional areas are: • Motor areas – control voluntary movement • Sensory areas – conscious awareness of sensation • Association areas – integrate diverse information Cerebral Cortex: Motor Areas • Primary (somatic) motor cortex • Premotor cortex • Broca’s area • Frontal eye field Primary Motor Cortex • Located in the precentral gyrus • Composed of pyramidal cells whose axons make up the corticospinal tracts • Allows conscious control of precise, skilled, voluntary movements • Motor homunculus – caricature of relative amounts of cortical tissue devoted to each motor function Premotor Cortex • Located anterior to the precentral gyrus • Controls learned, repetitious, or patterned motor skills • Coordinates simultaneous or sequential actions • Involved in the planning of movements Broca’s Area and Frontal Eye Field • Broca’s area • Located anterior to the inferior region of the premotor area • Present in one hemisphere (usually the left) • A motor speech area that directs muscles of the tongue • Is active as one prepares to speak • Frontal eye field • Located anterior to the premotor cortex and superior to Broca’s area • Controls voluntary eye movement Sensory Areas • Primary somatosensory cortex • Somatosensory association cortex • Visual areas • Auditory areas • Olfactory cortex • Gustatory cortex • Vestibular cortex Primary Somatosensory Cortex • Located in the postcentral gyrus, this area: • Receives information from the skin and skeletal muscles • Exhibits spatial discrimination • Somatosensory homunculus – caricature of relative amounts of cortical tissue devoted to each sensory function Somatosensory Association Area • Located posterior to the primary somatosensory cortex • Integrates sensory information • Forms comprehensive understanding of the stimulus • Determines size, texture, and relationship of parts Visual Area • Primary visual cortex • Located on the extreme posterior tip of the occipital lobe • Receives visual information from the retinas • Visual association area • Surround the primary visual cortex • Interprets visual stimuli (e.g., color, form, and movement) Auditory Areas • Primary auditory cortex • Located at the superior margin of the temporal lobe • Receives information related to pitch, rhythm, and loudness • Auditory association area • Located posterior to the primary auditory cortex • Stores memories of sounds and permits perception of sounds Association Areas • Prefrontal cortex • Language areas • General (common) interpretation area • Visceral association area Prefrontal Cortex • Location – anterior portions of the frontal lobe • Involved with intellect, cognition, recall, and personality • Necessary for judgment, reasoning, persistence, and conscience • Closely linked to the limbic system (emotional part of the brain) Language Areas • Located in a large area surrounding the left (or language-dominant) lateral sulcus • Major parts and functions: • Wernicke’s area – involved in sounding out unfamiliar words • Broca’s area – speech preparation and production • Lateral prefrontal cortex – language comprehension and word analysis • Lateral and ventral temporal lobe – coordinate auditory and visual aspects of language General (Common) Interpretation Area • Ill-defined region including parts of the temporal, parietal, and occipital lobes • Found in one hemisphere, usually the left • Integrates incoming signals into a single thought • Involved in processing spatial relationships Visceral Association Area • Located in the cortex of the insula • Involved in conscious perception of visceral sensations Lateralization of Cortical Function • Lateralization – each hemisphere has abilities not shared with its partner • Cerebral dominance – designates the hemisphere dominant for language • Left hemisphere – controls language, math, and logic • Right hemisphere – controls visual-spatial skills, emotion, and artistic skills Cerebral White Matter • Consists of deep myelinated fibers and their tracts • It is responsible for communication between: • The cerebral cortex and lower CNS center, and areas of the cerebrum • Types include: • Commissures – connect corresponding gray areas of the two hemispheres • Association fibers – connect different parts of the same hemisphere • Projection fibers – enter the hemispheres from lower brain or cord centers Basal Nuclei • Masses of gray matter found deep within the cortical white matter • The corpus striatum is composed of three parts • Caudate nucleus • Lentiform nucleus – composed of the putamen and the globus pallidus • Fibers of internal capsule running between and through caudate and lentiform nuclei Functions of Basal Nuclei • Though somewhat elusive, the following are thought to be functions of basal nuclei: • Influence muscular activity • Regulate attention and cognition • Regulate intensity of slow or stereotyped movements • Inhibit antagonistic and unnecessary movement Diencephalon • Central core of the forebrain • Consists of three paired structures – thalamus, hypothalamus, and epithalamus • Encloses the third ventricle Thalamus • Paired, egg-shaped masses that form the superolateral walls of the third ventricle • Connected at the midline by the intermediate mass • Contains four groups of nuclei – anterior, ventral, dorsal, and posterior • Nuclei project and receive fibers from the cerebral cortex Thalamic Function • Afferent impulses from all senses converge and synapse in the thalamus • Impulses of similar function are “sorted out,” edited, and relayed as a group • All inputs ascending to the cerebral cortex pass through the thalamus • Plays a key role in mediating sensation, motor activities, cortical arousal, learning, and memory Hypothalamus • Located below the thalamus, it caps the brainstem and forms the inferolateral walls of the third ventricle • Mammillary bodies: • Small, paired nuclei bulging anteriorly from the hypothalamus • Relay station for olfactory pathways • Infundibulum – stalk of the hypothalamus; connects to the pituitary gland • Main visceral control center of the body Hypothalamic Function • Regulates blood pressure, rate and force of heartbeat, digestive tract motility, rate and depth of breathing, and many other visceral activities • Is involved with perception of pleasure, fear, and rage • Controls mechanisms needed to maintain normal body temperature • Regulates feelings of hunger and satiety • Regulates sleep and the sleep cycle Endocrine Functions of the Hypothalamus • Releasing hormones control secretion of hormones by the anterior pituitary • The supraoptic and paraventricular nuclei produce ADH and oxytocin Epithalamus • Most dorsal portion of the diencephalon; forms roof of the third ventricle • Pineal gland – extends from the posterior border and secretes melatonin • Melatonin – a hormone involved with sleep regulation, sleep-wake cycles, and mood • Choroid plexus – a structure that secretes cerebral spinal fluid (CSF) Brain Stem • Consists of three regions – midbrain, pons, and medulla oblongata • Similar to spinal cord but contains embedded nuclei • Controls automatic behaviors necessary for survival • Provides the pathway for tracts between higher and lower brain centers • Associated with 10 of the 12 pairs of cranial nerves Midbrain • Located between the diencephalon and the pons • Midbrain structures include: • Cerebral peduncles – two bulging structures that contain descending pyramidal motor tracts • Cerebral aqueduct – hollow tube that connects the third and fourth ventricles • Various nuclei Midbrain Nuclei • Nuclei that control cranial nerves III (oculomotor) and IV (trochlear) • Corpora quadrigemina – four domelike protrusions of the dorsal midbrain • Superior colliculi – visual reflex centers • Inferior colliculi – auditory relay centers • Substantia nigra – functionally linked to basal nuclei • Red nucleus – largest nucleus of the reticular formation; red nuclei are relay nuclei for some descending motor pathways Pons • Bulging brainstem region between the midbrain and the med
More Less

Related notes for BIOB32H3

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.