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Copyright © 2010 Pearson Education, Inc. Chapter 12 The Central Nervous System.

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Presentation on theme: "Copyright © 2010 Pearson Education, Inc. Chapter 12 The Central Nervous System."— Presentation transcript:

1 Copyright © 2010 Pearson Education, Inc. Chapter 12 The Central Nervous System

2 Copyright © 2010 Pearson Education, Inc. Central Nervous System (CNS) CNS consists of the brain and spinal cord Cephalization Evolutionary development of a head and CNS Increased number of neurons in the head Highest level is reached in the human brain

3 Copyright © 2010 Pearson Education, Inc. Regions and Organization of the CNS Adult brain regions 1.Cerebral hemispheres 2.Diencephalon 3.Brain stem (midbrain, pons, and medulla) 4.Cerebellum

4 Copyright © 2010 Pearson Education, Inc. Regions and Organization of the CNS Spinal cord Central cavity of gray matter core External white matter composed of myelinated fiber tracts

5 Copyright © 2010 Pearson Education, Inc. Ventricles of the Brain Connected to one another and to the central canal of the spinal cord Lined by ependymal cells

6 Copyright © 2010 Pearson Education, Inc. Ventricles of the Brain Contain cerebrospinal fluid Two C-shaped lateral ventricles in the cerebral hemispheres Third ventricle in the diencephalon Fourth ventricle in the hindbrain, above the pons, develops from the lumen (opening) of the neural tube

7 Copyright © 2010 Pearson Education, Inc. Cerebral Hemispheres Surface markings Ridges (gyri), shallow grooves (sulci), and deep grooves (fissures) Five lobes Frontal Parietal Temporal Occipital Insula

8 Copyright © 2010 Pearson Education, Inc. Cerebral Hemispheres Surface markings Central sulcus Separates the precentral gyrus of the frontal lobe and the postcentral gyrus of the parietal lobe Longitudinal fissure Separates the two hemispheres Transverse cerebral fissure Separates the cerebrum and the cerebellum

9 Copyright © 2010 Pearson Education, Inc. Figure 12.6c Parietal lobe Frontal lobe Right cerebral hemisphere Occipital lobe Left cerebral hemisphere Cerebral veins and arteries covered by arachnoid mater Longitudinal fissure Posterior (c) Anterior

10 Copyright © 2010 Pearson Education, Inc. Figure 12.6d Left cerebral hemisphere Transverse cerebral fissure Cerebellum Brain stem (d)

11 Copyright © 2010 Pearson Education, Inc. Cerebral Cortex Thin (2–4 mm) superficial layer of gray matter 40% of the mass of the brain Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding Each hemisphere connects to contralateral side of the body There is lateralization of cortical function in the hemispheres

12 Copyright © 2010 Pearson Education, Inc. Functional Areas of the Cerebral Cortex The three types of functional areas are: Motor areas—control voluntary movement Sensory areas— conscious awareness of sensation Association areas— learning, decision making, complex movements Conscious behavior involves the entire cortex

13 Copyright © 2010 Pearson Education, Inc. Motor Areas Primary (somatic) motor cortex Frontal lobe Consciously control precise/skilled movements Spatial representation Premotor cortex Learned motor skills (repetitions, patterns) Planned movement Broca’s area Usually only in one hemisphere Motor speech area (thinking, planning, and performing) Frontal eye field Voluntary eye movement

14 Copyright © 2010 Pearson Education, Inc. Sensory Areas Primary somatosensory cortex Somatosensory association cortex Visual areas Auditory areas Olfactory cortex Gustatory cortex Visceral sensory area Vestibular cortex

15 Copyright © 2010 Pearson Education, Inc. Primary Somatosensory Cortex Located just behind the primary motor cortex In the postcentral gyri Receives sensory information from the skin, skeletal muscles, and joints Capable of spatial discrimination: identification of body region being stimulated

16 Copyright © 2010 Pearson Education, Inc. Somatosensory Association Cortex Posterior to the primary somatosensory cortex Integrates sensory input from primary somatosensory cortex – pressure, temperature, etc. Determines size, texture, and relationship of parts of objects being felt

17 Copyright © 2010 Pearson Education, Inc. Visual Areas - Sight Primary visual (striate) cortex Extreme posterior tip of the occipital lobe Receives visual information from the retinas Visual association area Surrounds the primary visual cortex Uses past visual experiences to interpret visual stimuli (e.g., color, form, and movement)

18 Copyright © 2010 Pearson Education, Inc. Auditory Areas - Hearing Primary auditory cortex Superior margin of the temporal lobes Interprets information from inner ear as pitch, loudness, and location Auditory association area Located posterior to the primary auditory cortex Stores memories of sounds and permits perception of sounds

19 Copyright © 2010 Pearson Education, Inc. OIfactory Cortex - Smell Medial aspect of temporal lobes Region of conscious awareness of odors

20 Copyright © 2010 Pearson Education, Inc. Gustatory Cortex - Taste In the insula just below the temporal lobe Involved in the perception of taste

21 Copyright © 2010 Pearson Education, Inc. Visceral Sensory Area – Physical Feeling Posterior to gustatory cortex Conscious perception of visceral sensations, e.g., upset stomach or full bladder, lungs bursting

22 Copyright © 2010 Pearson Education, Inc. Vestibular Cortex - Balance Posterior part of the insula and adjacent parietal cortex Responsible for conscious awareness of balance (position of the head in space)

23 Copyright © 2010 Pearson Education, Inc. Multimodal Association Areas Receive inputs from and sends outputs to multiple sources Give meaning to information received Store it as memory compare it to previous experience, and decide on action to take Area where sensations, thoughts, and emotions become conscious Three parts Anterior association area (prefrontal cortex) Posterior association area Limbic association area

24 Copyright © 2010 Pearson Education, Inc. Anterior Association Area (Prefrontal Cortex) Most complicated cortical region Involved with intellect, cognition, recall, and personality Contains working memory needed for judgment, reasoning, persistence, and conscience Development depends on feedback from social environment

25 Copyright © 2010 Pearson Education, Inc. Posterior Association Area Large region in temporal, parietal, and occipital lobes Plays a role in recognizing patterns and faces and localizing us in space Wernicke’s area - Involved in understanding written and spoken language

26 Copyright © 2010 Pearson Education, Inc. Limbic Association Area Part of the limbic system Provides emotional impact that helps establish memories Tells you if something is dangerous or pleasant with a situation

27 Copyright © 2010 Pearson Education, Inc. Lateralization of Cortical Function Lateralization Division of labor between hemispheres Cerebral dominance Designates the hemisphere dominance (left hemisphere in 90% of people) Left hemisphere Controls language, math, and logic Right hemisphere Insight, visual-spatial skills, intuition, and artistic skills Left and right hemispheres communicate via fiber tracts in the cerebral white matter

28 Copyright © 2010 Pearson Education, Inc. Cerebral White Matter Responsible for communication Commissures (in corpus callosum)—connect gray matter of the two hemispheres Association fibers — connect different parts of the same hemisphere Projection fibers — (corona radiata) connect the hemispheres with lower brain or spinal cord

29 Copyright © 2010 Pearson Education, Inc. Diencephalon Three paired structures Thalamus Hypothalamus Epithalamus Encloses the third ventricle Diencephalon Thalamus HypothalamusPineal Gland (part of epithalamus)

30 Copyright © 2010 Pearson Education, Inc. Thalamus 80% of diencephalon Superolateral walls of the third ventricle Sorts, edits, and relays information Mediates sensation, motor activities, cortical arousal, learning, and memory

31 Copyright © 2010 Pearson Education, Inc. Hypothalamus Forms the inferolateral walls of the third ventricle Main visceral control center Center for emotional response: Involved in perception of pleasure, fear, and rage and in biological rhythms and drives

32 Copyright © 2010 Pearson Education, Inc. Brain Stem Three regions Midbrain Pons Medulla oblongata

33 Copyright © 2010 Pearson Education, Inc. Brain Stem Similar structure to spinal cord Controls automatic behaviors necessary for survival Contains fiber tracts connecting higher and lower neural centers Associated with 10 of the 12 pairs of cranial nerves

34 Copyright © 2010 Pearson Education, Inc. Midbrain Located between the diencephalon and the pons Visual reflex centers Auditory relay centers Relay centers for some of the motor pathways

35 Copyright © 2010 Pearson Education, Inc. Pons Forms part of the anterior wall of the fourth ventricle Fibers of the pons Connect higher brain centers and the spinal cord Relay impulses between the motor cortex and the cerebellum Origin of cranial nerves V (trigeminal), VI (abducens), and VII (facial) Some nuclei of the reticular formation Nuclei that help maintain normal rhythm of breathing

36 Copyright © 2010 Pearson Education, Inc. Medulla Oblongata Joins spinal cord at foramen magnum Forms part of the ventral wall of the fourth ventricle Relay center for information from muscles and joints to cerebellum Mediates responses to help with equilibrium Other relay centers for sensory information

37 Copyright © 2010 Pearson Education, Inc. Medulla Oblongata Autonomic reflex centers Cardiovascular center Cardiac center adjusts force and rate of heart contraction Vasomotor center adjusts blood vessel diameter for blood pressure regulation

38 Copyright © 2010 Pearson Education, Inc. Medulla Oblongata Respiratory centers Generate respiratory rhythm Control rate and depth of breathing, with pontine centers

39 Copyright © 2010 Pearson Education, Inc. The Cerebellum 11% of brain mass Dorsal to the pons and medulla Subconsciously provides precise timing and appropriate patterns of skeletal muscle contraction

40 Copyright © 2010 Pearson Education, Inc. Cognitive Function of the Cerebellum Recognizes and predicts sequences of events during complex movements Plays a role in nonmotor functions such as word association and puzzle solving

41 Copyright © 2010 Pearson Education, Inc. Functional Brain Systems Networks of neurons that work together and span wide areas of the brain Limbic system Reticular formation

42 Copyright © 2010 Pearson Education, Inc. Limbic System Emotional or affective brain Amygdala — recognizes angry or fearful facial expressions, assesses danger, and elicits the fear response Cingulate gyrus — plays a role in expressing emotions via gestures, and resolves mental conflict Puts emotional responses to odors Example: skunks smell bad Cingulate gyrus Admygdala

43 Copyright © 2010 Pearson Education, Inc. Reticular Formation: RAS and Motor Function RAS (reticular activating system) Sends impulses to the cerebral cortex to keep it conscious and alert Filters out repetitive and weak stimuli (~99% of all stimuli!) Severe injury results in permanent unconsciousness (coma)

44 Copyright © 2010 Pearson Education, Inc. Language Language implementation system Broca’s area and Wernicke’s area (in the association cortex on the left side) Analyzes incoming word sounds Produces outgoing word sounds and grammatical structures Corresponding areas on the right side are involved with nonverbal language components

45 Copyright © 2010 Pearson Education, Inc. Memory Storage and retrieval of information Two stages of storage Short-term memory (STM, or working memory)—temporary holding of information; limited to seven or eight pieces of information Long-term memory (LTM) has limitless capacity

46 Copyright © 2010 Pearson Education, Inc. Transfer from STM to LTM Factors that affect transfer from STM to LTM Emotional state—best if alert, motivated, surprised, and aroused Rehearsal—repetition and practice Association—tying new information with old memories Automatic memory—subconscious information stored in LTM

47 Copyright © 2010 Pearson Education, Inc. Categories of Memory 1.Declarative memory (factual knowledge) Explicit information Related to our conscious thoughts and our language ability Stored in LTM with context in which it was learned 2.Nondeclarative memory Less conscious or unconscious Acquired through experience and repetition Best remembered by doing; hard to unlearn Includes procedural (skills) memory, motor memory, and emotional memory

48 Copyright © 2010 Pearson Education, Inc. Protection of the Brain Bone (skull) Membranes (meninges) Watery cushion (cerebrospinal fluid) Blood-brain barrier

49 Copyright © 2010 Pearson Education, Inc. Meninges Cover and protect the CNS Protect blood vessels and enclose venous sinuses Contain cerebrospinal fluid (CSF) Form partitions in the skull Three layers Dura mater Arachnoid mater Pia mater

50 Copyright © 2010 Pearson Education, Inc. Cerebrospinal Fluid (CSF) Composition Watery solution Less protein and different ion concentrations than plasma Constant volume Functions Gives buoyancy to the CNS organs Protects the CNS from blows and other trauma Nourishes the brain and carries chemical signals

51 Copyright © 2010 Pearson Education, Inc. Blood-Brain Barrier Composition Continuous endothelium of capillary walls Basal lamina Astrocytes Helps maintain a stable environment for the brain Separates neurons from some bloodborne substances

52 Copyright © 2010 Pearson Education, Inc. Blood-Brain Barrier: Functions Selective barrier Allows nutrients to move by facilitated diffusion Allows any fat-soluble substances to pass, including alcohol, nicotine, and anesthetics Absent in some areas, e.g., vomiting center and the hypothalamus, where it is necessary to monitor the chemical composition of the blood

53 Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of the Brain Traumatic brain injuries Concussion—temporary alteration in function Contusion—permanent damage Subdural or subarachnoid hemorrhage—may force brain stem through the foramen magnum, resulting in death Cerebral edema—swelling of the brain associated with traumatic head injury

54 Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of the Brain Cerebrovascular accidents (CVAs)(strokes) Blood circulation is blocked and brain tissue dies, e.g., blockage of a cerebral artery by a blood clot Typically leads to hemiplegia, or sensory and speed deficits Transient ischemic attacks (TIAs)—temporary episodes of reversible cerebral ischemia Tissue plasminogen activator (TPA)

55 Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of the Brain Degenerative brain disorders Alzheimer’s disease (AD): a progressive degenerative disease of the brain that results in dementia Parkinson’s disease: degeneration of the dopamine- releasing neurons of the substantia nigra Huntington’s disease: a fatal hereditary disorder caused by accumulation of the protein huntingtin that leads to degeneration of the basal nuclei and cerebral cortex

56 Copyright © 2010 Pearson Education, Inc. Spinal Cord Location Begins at the foramen magnum Ends as conus medullaris at L 1 vertebra Functions Provides two-way communication to and from the brain Contains spinal reflex centers

57 Copyright © 2010 Pearson Education, Inc. Spinal Cord: Protection Bone, meninges, and CSF Cushion of fat and a network of veins in the epidural space between the vertebrae and spinal dura mater CSF in subarachnoid space

58 Copyright © 2010 Pearson Education, Inc. Spinal Cord Spinal nerves 31 pairs Cervical and lumbar enlargements The nerves serving the upper and lower limbs emerge here Cauda equina The collection of nerve roots at the inferior end of the vertebral canal

59 Copyright © 2010 Pearson Education, Inc. Cross-Sectional Anatomy Two lengthwise grooves divide cord into right and left halves Ventral (anterior) median fissure Dorsal (posterior) median sulcus Gray commissure— connects masses of gray matter; encloses central canal

60 Copyright © 2010 Pearson Education, Inc. Gray Matter Dorsal horns—interneurons that receive somatic and visceral sensory input Ventral horns—somatic motor neurons whose axons exit the cord via ventral roots Lateral horns (only in thoracic and lumbar regions) –sympathetic neurons Dorsal root (spinal) gangia—contain cell bodies of sensory neurons

61 Copyright © 2010 Pearson Education, Inc. White Matter Consists mostly of ascending (sensory) and descending (motor) tracts Transverse tracts (commissural fibers) cross from one side to the other Tracts are located in three white columns (funiculi on each side—dorsal (posterior), lateral, and ventral (anterior) Each spinal tract is composed of axons with similar functions

62 Copyright © 2010 Pearson Education, Inc. Spinal Cord Cross Section

63 Copyright © 2010 Pearson Education, Inc. Spinal Cord Trauma Functional losses Parasthesias Sensory loss Paralysis Loss of motor function Palsy Weakness that is reversible

64 Copyright © 2010 Pearson Education, Inc. Spinal Cord Trauma Flaccid paralysis—severe damage to the ventral root or ventral horn cells Impulses do not reach muscles; there is no voluntary or involuntary control of muscles Muscles atrophy Spastic paralysis—damage to upper motor neurons of the primary motor cortex Spinal neurons remain intact; muscles are stimulated by reflex activity No voluntary control of muscles

65 Copyright © 2010 Pearson Education, Inc. Spinal Cord Trauma Transection Cross sectioning of the spinal cord at any level Results in total motor and sensory loss in regions inferior to the cut Paraplegia—transection between T 1 and L 1 Quadriplegia—transection in the cervical region

66 Copyright © 2010 Pearson Education, Inc. Poliomyelitis Destruction of the ventral horn motor neurons by the poliovirus Muscles atrophy Death may occur due to paralysis of respiratory muscles or cardiac arrest Survivors often develop postpolio syndrome many years later, as neurons are lost

67 Copyright © 2010 Pearson Education, Inc. Amyotrophic Lateral Sclerosis (ALS) Also called Lou Gehrig’s disease Involves progressive destruction of ventral horn motor neurons and fibers of the pyramidal tract Symptoms—loss of the ability to speak, swallow, and breathe Death typically occurs within five years Linked to glutamate excitotoxicity, attack by the immune system, or both

68 Copyright © 2010 Pearson Education, Inc. Other Spinal Cord Disorders Cerebral Palsy Poor control of voluntary muscles May be due to a lack of oxygen during development Spina bifida Incomplete formation of vertebral arches Lumbar myelomenigocele


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