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Central Nervous System Basic Setup of the Nervous System Nervous Tissue Peripheral Nervous System Spinal and Cranial Nerves Central Nervous System: Integration and Command Brain Spinal Cord Sensory Sensory Skin, skeletal muscle and joints Motor Visceral Visceral Organs Somatic: Control of skeletal muscles Autonomic: Regulates smooth muscle, cardiac muscle and glands Sympathetic: Fight or Flight Parasympathetic Rest and Digest Basic Setup of the Nervous System Nervous Tissue Central Nervous System: Integration and Command Brain Spinal Cord The Brain • The brain is divided into 5 main areas based originally on development but also on function. The Brain • The brain is divided into 5 main areas based originally on development but also on function. Forebrain Midbrain Hindbrain Development Starting with the Ventricles • There are four ventricles: – The paired Cshaped lateral ventricles – The third ventricle found in the diencephalon – The fourth ventricle found in the hindbrain dorsal to the pons Ventricles of the Brain: Another View 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 longitudinal fissure Gyri sulci fissures Major Lobes, Gyri, and Sulci of the Cerebral Hemisphere • Deep sulci divide the hemispheres into five lobes: – Frontal – Parietal – Temporal – Occipital – Insula The Insula is deep under temporal lobe The Insula Major Lobes, Gyri, and Sulci of the Cerebral Hemisphere • Parieto-occipital sulcus – separates the parietal and occipital lobes • Lateral sulcus – separates the parietal and temporal lobes • The precentral and postcentral gyri border the central sulcus Cerebral Hemispheres • The cerebral hemispheres have three basic regions: cortex, white matter, and basal nuclei Midbrain Cerebral Cortex • The cortex – superficial gray matter; accounts for 40% of the mass of the brain • It enables sensation, communication, memory, understanding, and voluntary movements Cerebral Cortex • 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 This is not a political statement . Functional Areas of the Cerebral Cortex • The three types of functional areas are: – Sensory areas – conscious awareness of sensation – Association areas – integrate diverse information (swat, just ate or whatever it takes, I love chicken) – Motor areas – control voluntary movement Functional Areas of the Cerebral Cortex Motor Association Sensory Functional Areas of the Cerebral Cortex Motor Association Sensory Functional Areas of the Cerebral Cortex Motor Association Sensory PET scans Functional MRI • Finger pressing a button. • Which finger? • Free will discussion 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 • Actually signals muscles Primary Motor Cortex • Motor homunculus – A caricature of location and relative amounts of cortical tissue devoted to each motor function – When you use scissors, you move your jaw. Premotor Cortex • Located anterior to the precentral gyrus • Controls learned, repetitious, or patterned motor skills • Involved in the planning of movements Broca’s Area • 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 – A logical forward expansion of the area of the motor homonculus for mouth muscles. Frontal Eye Field • Frontal eye field – Located anterior to the premotor cortex and superior to Broca’s area – Controls voluntary eye movement – Another logical expansion of the area of the motor homunculus that controls the hand. This increases hand-eye coordination. Sensory Areas • Primary somatosensory cortex • Somatosensory association cortex • Visual and auditory areas • Olfactory, gustatory, and vestibular cortices Sensory Areas Primary Somatosensory Cortex • Located in the postcentral gyrus: – 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 Primary Somatosensory Cortex • Somatosensory homunculus – caricature of location and relative amounts of cortical tissue devoted to each sensory function Somatosensory Association Cortex • Located posterior to the primary somatosensory cortex • Integrates sensory information • Forms comprehensive understanding of the stimulus • Determines size, texture, and relationship of parts An example: The secondary sensory association area determines “what just hit me in the face?” Visual Areas • Primary visual (striate) cortex – Simple interpretations (lines) – Most of it is buried in the calcarine sulcus – Receives visual information from the retinas • Visual association area – Surrounds the primary visual cortex – Interprets visual stimuli (e.g., color, form, and movement) Striate Cortex Auditory Areas • Primary auditory cortex – Located at the superior edge of the temporal lobe – Interprets pitch, rhythm, and loudness • Auditory association area – Located posterior to the primary auditory cortex – Stores memories of sounds and permits perception of sounds – Let’s music affect mood and cause you to dance. Association Areas • Prefrontal cortex • Language areas – Widely distributed • General (common) interpretation area • Visceral association area Prefrontal Cortex • Involved with intellect, cognition, recall, and personality • Responsible for planning, complex ideas, behaviors, concentration and the ability to focus. This area is also responsible for emotional traits, judgment and inhibition. • Closely linked to the limbic system (emotional part of the brain) Prefrontal Cortex: Phineas Gage Language Areas • 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 Language Areas • Language is highly distributed. • There are many parts to language. – articulation, fluency, names, comprehension, reading, writing – Others • Patients may lose parts of their language abilities. 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 – Like right now, your GIA is saying “man, this lecture is soooo cool.” • Involved in processing spatial relationships – Of outside world, one’s body, and even sentence structure. Visceral Association Area • Located in the cortex of the insula • Involved in conscious perception of visceral sensations Lateralization • Lateralization – each hemisphere has abilities not shared with its partner • 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, the lower CNS center, and areas of the cerebrum Cerebral White Matter • Types include: – Association fibers – connect different parts of the same hemisphere – Commissures – connect corresponding gray areas of the two hemispheres – Projection fibers – enter the hemispheres from lower brain or cord centers Basal Ganglia Midbrain Basal Nuclei Midbrain • Masses of gray matter found deep within the cortical white matter • Composed of several different groups of cells; caudate, putamen, nucleus accumbens, globus pallidus, substantia nigra, subthalamic nucleus, and historically the claustrum and the amygdala. • The function is generally motor. Basal Nuclei Basal Nuclei Basal Ganglia • The BG is the master of the motor system. • It coordinates many different motor area from brainstem to cortex, to cerebellum. Basal Ganglia: Brake Hypothesis • The function of the basal ganglia is often described in terms of a "brake hypothesis". – To sit still, you must put the brakes on all movements except those reflexes that maintain an upright posture. – To move, you must apply a brake to some postural reflexes, and release the brake on voluntary movement. • Deficits in the BG tend to fall into one of two categories: – the presence of extraneous unwanted movements – an absence or difficulty with intended movements. Huntington’s Basal Ganglia Hemiballismus Parkinson’s Hemiballismus Parkinson’s Disease Huntington’s Chorea Hit Dunn Seconday motor: coordinates muscles of the arm Primary motor: moves individual muscles Basal Ganglia: Starts and Stops Also “manages” All the other inputs. Amygdala: What is my emotional intent (good job, joking, anger Cerebellum: Has “instructions” on how to throw a punch. Many parts of the brain would contribute to the decision to hit Dunn. The Basal Ganglia will coordinate these inputs. The Diencephalon Forebrain Midbrain Hindbrain Diencephalon • Central core of the forebrain • Consists of three paired structures – – Thalamus – Hypothalamus – Epithalamus Thalamus • Paired, egg-shaped masses that connected at the midline by the intermediate mass • Contains four groups of nuclei – anterior, ventral, dorsal, and posterior • Can be thought of as Grand Central Station for sensory information. Thalamus limbic language emotion auditory vision Integrates thalamic motor Coordinates BG with somatosensory Thalamic Function • Afferent impulses from all senses (except olfaction) converge and synapse in the thalamus • Impulses are sorted out, edited, and relayed as a group • Some motor information • Plays a key role in mediating sensation, motor activities, cortical arousal, learning, and memory Thalamic Function • Hearing your name in a crowd • Picking out what sensory information is important (the tv when there is a lot of bacground noise) • Autism Hypothalamus • Hypothalamic Nuclei • 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 Hypothalamus • Hypothalamic Nuclei • Mammillary bodies • Infundibulum Hypothalamic Nuclei Hypothalamic Nuclei Lack of hunger Sleep Obesity 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 posterior pituitary releases ADH and oxytocin Epithalamus • Pineal gland – extends from the posterior border and secretes melatonin – Melatonin – a hormone involved with sleep regulation, sleepwake cycles, and mood • Choroid plexus – a structure that secretes cerebral spinal fluid (CSF) The Brainstem Forebrain Midbrain Hindbrain Brain Stem • Consists of three regions – Midbrain – Pons, – Medulla oblongata • Similar to spinal cord but contains embedded nuclei Brain Stem • Controls automatic behaviors necessary for survival (respiration, heart rate, etc.) • Provides the pathway for tracts between higher and lower brain centers • Associated with 10 of the 12 pairs of cranial nerves Brain Stem Midbrain • Located between the diencephalon (thalamus) 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 Brain Stem Midbrain Nuclei • Corpora quadrigemina – four dome like protrusions of the dorsal midbrain • Superior colliculi – visual reflex centers • Inferior colliculi – auditory reflex centers • Substantia nigra – functionally linked to basal nuclei (Parkinson’s) • Red nucleus – largest nucleus of the reticular formation; red nuclei are relay nuclei for some descending motor pathways Midbrain Nuclei: Colliculi • Corpora quadrigemina – four domelike protrusions of the dorsal midbrain • Superior colliculi – visual reflex centers • Inferior colliculi – auditory reflex centers Midbrain Nuclei Pons • Bulging brainstem region between the midbrain and the medulla oblongata • Fibers of the pons: – Connect higher brain centers and the spinal cord – Relay impulses between the motor cortex and the cerebellum • Location of the Reticular Formation Medulla Oblongata • Most inferior part of the brainstem • Pyramids – two longitudinal ridges formed by corticospinal tracts • Decussation of the pyramids – crossover points of the corticospinal tracts Medulla Nuclei • Inferior olivary nuclei – gray matter that relays sensory information • Cranial nerves X, XI, and XII are associated with the medulla • Vestibular nuclear complex – synapses that mediate and maintain equilibrium • Ascending sensory tract nuclei, including nucleus cuneatus and nucleus gracilis Medulla Nuclei • Cardiovascular control center – adjusts force and rate of heart contraction • Respiratory centers – control rate and depth of breathing