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The Central Nervous System

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The Central Nervous System THE CENTRAL NERVOUS SYSTEM The Brain & Spinal Cord Review: Nervous System Parallel Distributed Processing Composition of the CNS Nuclei: Clusters of neurons in the CNS (“neighborhoods”) Fiber Tracts/Pathways: Bundles of axons that travel together (“highway”) The Spinal Cord Receives signals from the senses & relays them to the brain. Neurons in the SC also carry signals from the brain to the muscles. Sensory Neurons: Afferent neurons that carry signals TO the brain (arrive) Motor Neurons: Efferent neurons that carry information FROM the brain. (exit) Spinal Cord Also direct simple behaviors called reflexes: simple, automatic movements. Interesting facts about the CNS! The adult human brain weighs about 3 lbs. The human spinal cord is 45 cm long in men and 43 cm long in women. 3 Major Divisions of the Brain The The The Hindbrain Midbrain Forebrain Cerebral Cortex The Hindbrain The Hindbrain • Lies just inside the skull • Continuation of the SC & makes up part of the brain stem. Location • Signals coming from the SC reach the hindbrain first. • Nuclei in the HB control vital autonomic functions. • Including blood pressure, heart rate & breathing. Function • Medulla (Oblongata), Reticular Formation, Locus Associated Coeruleus, Cerebellum & Pons. Parts Hindbrain: The Medulla (Oblongata) • Lies below the Pons Location • Controls automatic functions • BP, HR, breathing, digestion, Function etc. Hindbrain: Reticular Formation • Network of cells threaded Location throughout the HB & MB. • Responsible for consciousness, awareness, arousal, attention. Function • Filters sensory input. Hindbrain: Locus Coeruleus “Blue Spot” • Small nucleus Location located in the R.F. • Involved in Function directing attention. Hindbrain: Cerebellum (“little brain”) • Connected by the brain stem to the SC at the base of the skull. Location • Coordination of movement & balance. • Related to other behaviors not directly related to physical movement. Function Hindbrain: Pons (“bridge”) • Directly below the midbrain. • Connects the medulla to the cerebral cortex & Location cerebellum. • Helps send information to other parts of the brain. • Involved in sleep & arousal. Function • Manufactures chemicals involved in sleep. The Midbrain The Midbrain • Very small structure directly above the HB and below the forebrain. Location • Along with parts of the HB, the MB makes up the brain stem. • Integrates sensory information w/ simple, reflexive movements. Function • Substantia Nigra Associated Parts Midbrain: Substantia Nigra (“Black Substance”) • Area of pigmented cells at the top of the midbrain region. • Connected to the striatum in the Location forebrain. • Produces & uses dopamine (a NT involved in movement & other functions). • Along with the striatum, helps smoothly begin movement. Function • May be linked to mood & addiction. The Forebrain The Forebrain • Upper region of the brain. • The largest & most complex part of the brain, which folds Location back over & completely covers other parts of the brain. • Responsible for the most complex aspects of behavior. Function • Striatum, hypothalamus, thalamus, suprachiasmatic nuclei, amygdala, hippocampus. Associated • Some of these parts are part of the limbic system. Parts The Limbic System Located under the cortex region of the brain and above the brain stem. Responsible regulating: Memories Motivation (hunger, sex, thirst) Emotion Forebrain: Thalamus Forebrain: Thalamus • Above the brain stem. Location • “Relay station” for all sensory information (except smell). • Processes sensory info from SC & Function sends the info to the cerebral cortex. Forebrain: Hypothalamus Forebrain: Hypothalamus • Lies underneath the thalamus & connects to many other brain regions. Location • “Regulator of biological needs.” • Regulates hunger, thirst, body temp, sex drive, etc. • Links to the endocrine system & controls the Function pituitary gland. • Contains the suprachiasmatic nuclei: the brain’s “time piece.” Establishes a 24 hour Function clock that maintains biological rhythms. Forebrain: Amygdala • An almond shaped structure that lies within the temporal lobe of the brain a few Location inches from the ear. • Emotional and social processing. Particularly fear. • Memory processing & decision Function making. Forebrain: Hippocampus Forebrain: Hippocampus • Located deep within the temporal lobe. • Extends from the Location amygdala. • Associated with the formation of new memories. • Also appears to send memories into the cerebral Function cortex for long term storage. Cerebral Cortex Cerebral Cortex & Hemispheres • Outermost part of the brain. • Organized into two halves: Left & Right Cerebral Hemispheres Location • Analyzes all sensory information. • Control of voluntary movements & other complex actions (higher order thought). Function • Organized into lobes & and various cortical regions. Associated Parts Corpus Collosum • Bundle of nerves which connects the cerebral hemispheres and the Location various lobes. • Allows the brain to operate as one unified whole. Function Gyri & Sulci • Gyri: Make up the ridges of the cortex. • Sulci: Make up the fissures Location (valleys) of the cortex. • Help identify the major cortex Function areas. Anatomical Areas: Lobes Frontal Lobe • Top front part of the brain, Location behind the eyes. • Creativity, problem solving, attention, initiative, physical Function reaction, sense of smell & libido. Parietal Lobe • Top to the back of the brain. Location • Touch, sensory & spatial comprehension, language & Function reading functions. Functions Temporal Lobe • Behind the temple region. Location • Auditory & visual memory, fear, sense of identity, some hearing & Function speech. Occipital Lobe • Back of the brain. Location • Vision & some reading. Function Functional Areas: Cortices & Areas Sensory Cortex Visual Auditory Cortex Somatosensory Cortex Cortex Receives touch, pain, Receives visual Receives and temperature auditory information information Monitors information Proprioception Made up of Made up of Made up of cells cells in the cells in the in the Parietal Occipital Lobe Temporal Lobe. Lobe. Somatosensory Cortex Allows people to interpret a wide range of sensations. Network of specialized cells on the skin fire & travel to the thalamus. The thalamus relays the info to the somatosensory cortex. Each area of the cortex corresponds with the specialized cells in the skin. Sensory Homunculus The link between skin locations & locations in the som. cortex have been demonstrated during brain surgery. Research shows particular sensory inputs can be changed by experience. The Motor Cortex Located in the Frontal Lobe. Create voluntary movements in specific parts of the body. Specialized neurons control movement of the hand, foot, etc. Translates locations in space relative to your body & which muscles to activate at what force. Motor Homunculus The Association Cortex Multiple A.C.’s throughout the brain. Perform complex cognitive tasks (such as associating words w/ images). Broca’s Area: Located in the F.L. Controls the muscles which produce speech. Wernicke’s Area: Located in the T.L. Involved in the interpretation of speech & the ability to understand word meaning. Association Cortex Damage Broca’s Aphasia Results in difficulty speaking. Mental organization of speech suffers. Speech is often grammatically incorrect. Words come slowly (perhaps stuttering) Wernicke’s Aphasia Also disrupts the ability for the person to Disrupts ability to understand the meaning speak understandably (word organization, of words. context, etc.).
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