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Chapter 12: The Central Nervous System. Central Nervous System Brain and Spinal Cord Body’s supercomputer Cephalization – elaboration towards rostal “towards.

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Presentation on theme: "Chapter 12: The Central Nervous System. Central Nervous System Brain and Spinal Cord Body’s supercomputer Cephalization – elaboration towards rostal “towards."— Presentation transcript:

1 Chapter 12: The Central Nervous System

2 Central Nervous System Brain and Spinal Cord Body’s supercomputer Cephalization – elaboration towards rostal “towards the snout” or anterior portion of CNS Also increase in the number of neurons

3 Brain Adult male – 1600 g (3.5 lbs) Adult female – 1450 g (3.2 lbs) Brain mass per body mass - equal

4 Embryonic Development 1.3 week embryo- ectoderm thickens along dorsal midline of body = neural plate 2.Neural tube invaginates – forms groove flanked by neural folds 3.Groove deepens – superior ridges fuse forming neural tube – detached from ectoderm and sinks into a deeper position 4.Neural tube differentiates into CNS – brain anterior and spinal cord - caudal

5 Embryonic Development 5. Neural crest forms – gives rise to some neurons 6. Neural tube – anterior end expands -3 primary brain vesicles – -1. prosencephalon – forebrain -2. mesencephalon – midbrain -3. rhomben cephalon – hindbrain 7. Week 5 – primary vesicles  secondary vesicles -Forebrain  telencephalon (endbrain) + diencephalon (hindbrain) -Hindbrain constricts – metencephalon “afterbrain” -Metencephalon – “spinal brain”

6 Embryonic Development 8. 5 – secondary vesicles – develop into major structures of adult brain 2 cerebral hemispheres – cerebrum – Diencephalon – hypothalamus – Thalamus – Epithalamus – Retina Mesencephalon = midbrain Metencephalon = pons Myelencephalon = cerebellum Midbrain and hindbrain = spinal cord

7 Figure 12.1, step 1 The neural plate forms from surface ectoderm. 1 Head Tail Surface ectoderm Neural plate

8 Figure 12.1, step 2 The neural plate invaginates, forming the neural groove, flanked by neural folds. 2 Neural folds Neural groove

9 Figure 12.1, step 3 Neural fold cells migrate to form the neural crest, which will form much of the PNS and many other structures. 3 Neural crest

10 Figure 12.1, step 4 The neural groove becomes the neural tube, which will form CNS structures. 4 Surface ectoderm Head Tail Neural tube

11 (a) Neural tube (b) Primary brain vesicles Anterior (rostral) Posterior (caudal) Rhombencephalon (hindbrain) Mesencephalon (midbrain) Prosencephalon (forebrain) Figure 12.2a-b

12 (d) Adult brain structures (c) Secondary brain vesicles Spinal cord Cerebellum Brain stem: medulla oblongata Brain stem: pons Brain stem: midbrain Diencephalon (thalamus, hypothalamus, epithalamus), retina Cerebrum: cerebral hemispheres (cortex, white matter, basal nuclei) Myelencephalon Metencephalon Mesencephalon Diencephalon Telencephalon Central canal Fourth ventricle Cerebral aqueduct Third ventricle Lateral ventricles (e) Adult neural canal regions Figure 12.2c-e

13 Regions of Brain 1.Cerebral Hemispheres 2.Diencephalon 3.Brain stem (pons, midbrain, and medulla)

14 Figure 12.4 Cerebrum Cerebellum Migratory pattern of neurons Cortex of gray matter Inner gray matter Gray matter Outer white matter Central cavity Inner gray matter Gray matter Outer white matter Central cavity Inner gray matter Outer white matter Region of cerebellum Brain stem Spinal cord

15 Pattern Central cavity surrounded by gray matter (neuron cell bodies) External – white matter (myelinated fiber tracts) Outer layer of gray matter – cortex – dissapears as you move down the brain stem

16 Ventricles Arise from expansions of lumen (cavity) of embryonic neural tube Filled with cerebral spinal fluid Lined by ependymal cells

17 Figure 12.5 Anterior horn Interventricular foramen Inferior horn Lateral aperture (b) Left lateral view Lateral ventricle Septum pellucidum Third ventricle Cerebral aqueduct (a) Anterior view Fourth ventricle Central canal Inferior horn Posterior horn Median aperture Lateral aperture

18 Lateral Ventricles Deep in cerebral hemisphere Large C – shaped chambers separated by septum pellucidum Communicate with 3 rd ventricle – in diencephalon Channel – intraventricular foramen 3 rd ventricle continuous with 4 th – canal cerebral aqueduct 4 th ventricle – 3 openings – 2 lateral apertures and median aperture

19 Figure 12.5 Anterior horn Interventricular foramen Inferior horn Lateral aperture (b) Left lateral view Lateral ventricle Septum pellucidum Third ventricle Cerebral aqueduct (a) Anterior view Fourth ventricle Central canal Inferior horn Posterior horn Median aperture Lateral aperture

20 Cerebral Hemispheres Superior part of brain 83 % of brain’s mass Cover and obscure diencephalon and top of brain stem Surface – gyri – elevated ridges Sulci – grooves Fissures – deeper grooves Longitudinal fissure – separates cerebral hemispheres Transverse cerebral fissure – separates cerebral from cerebellum

21 Cerebral Hemisphere Divided into 5 lobes by sulci Central sulcus – frontal plane – separates frontal lobe from parietal lobe Percentral gyrus and postcentral gyrus – border – central sulcus Occipital lobe – separate from parietal by parietocciplital sulcus Lateral sulcus – outlines temporal lobe Insula – 5 th lobe – deep in lateral sulcus – forms its floor

22 Figure 12.6a Postcentral gyrus Central sulcus Precentral gyrus Frontal lobe (a) Parietal lobe Parieto-occipital sulcus (on medial surface of hemisphere) Lateral sulcus Transverse cerebral fissure Occipital lobe Temporal lobe Cerebellum Pons Medulla oblongata Spinal cord Cortex (gray matter) Fissure (a deep sulcus) Gyrus Sulcus White matter

23 Figure 12.6b Central sulcus (b) Frontal lobe Temporal lobe (pulled down) Gyri of insula

24 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

25 Figure 12.6d Left cerebral hemisphere Transverse cerebral fissure Cerebellum Brain stem (d)

26 Brain Fits snuggly in skull Frontal lobes – lie in anterior cranial fossa Middle cranial fossa – temporal lobe Each hemisphere – 3 regions 1. cerebral cortex – gray 2. internal white matter 3. basal nuclei

27 Cerebral Cortex “executive suite” of NS conscious mind Enables awareness of ourselves, our sensations, and enables us to communicate, remember, and understand Also voluntary movement Composed of gray matter – neuron cell bodies, dendrites, glial and blood vessels

28 Cerebral Cortex Billions of neurons – arranged in 6 layers 2-4 mm thick – 40 % of total brainmass 52 cortical areas – Broadman areas

29 Cerebral Cortex 3 functional areas – – 1. motor area – 2. sensory area – 3. association area All neurons – interneurons Each hemisphere – sensory and motor functions of opposite sides of body Hemispheres – not entirely equal in function – Lateralization or specialization of cortical functions No functional area acts alone Conscious behavior involves the entire cortex

30 Figure 12.8a Gustatory cortex (in insula) Primary motor cortex Premotor cortex Frontal eye field Working memory for spatial tasks Executive area for task management Working memory for object-recall tasks Broca’s area (outlined by dashes) Solving complex, multitask problems (a) Lateral view, left cerebral hemisphere Motor areas Prefrontal cortex Sensory areas and related association areas Central sulcus Primary somatosensory cortex Somatosensory association cortex Somatic sensation Taste Wernicke’s area (outlined by dashes) Primary visual cortex Visual association area Vision Auditory association area Primary auditory cortex Hearing Primary motor cortex Motor association cortex Primary sensory cortex Sensory association cortex Multimodal association cortex

31 Motor Areas Control voluntary movement Posterior part of frontal lobes: primary motor cortex, premotor cortex, Broca’s area, and frontal eye field

32 Motor Area – Primary Motor Cortex Primary (somatic) motor cortex – Located in precentral gyrus of frontal lobe Large neurons – pyramidal cells Allow control of precise or skilled voluntary movements Long axons – project into spinal cord – pyramidal tracts Somatotrophy – control of body structures mapped to places Muscles controlled by multiple spots

33 Figure 12.9 Toes Swallowing Tongue Jaw Primary motor cortex (precentral gyrus) Motor Motor map in precentral gyrus Posterior Anterior

34 Motor Area – Premotor Cortex Just anterior to precentral gyrus Controls learned motor skills of repetitious pattern or nature Coordinates movements of several muscle groups Memory bank for skilled motor activites

35 Motor Area – Broca’s Area Lies anterior to inferior region of premotor area Considered to be 1. present in one hemisphere only (usually the left) 2. special motor speech area – directs muscles involved in speech production Recently shown to “light up” as we prepare to think or even think about voluntary activities other than speech

36 Motor Area – Frontal Eye Field Located partial in and anterior to premotor cortex and superior to Broca’s area Controls voluntary movement of eyes

37 Damage Damage to areas of primary motor cortex – paralyzes the body muscles controlled by those areas Voluntary control lost, muscles can still contract reflexively Premotor cortex - damage results in a loss in motor skills programmed in that region, but muscle strength and ability to perform movements are not

38 Sensory Areas Occur in parietal lobe, insular, temporal, and occipital lobes 1. Primary Somartosensory Cortex – In post central gyrus of parietal lobe Neurons receive info from general (somatic) sensory receptors in the skin and proprioceptors (position sense receptors) in skeletal muscle, joints and tendons Neurons identify body region being stimulated – spatial discrimination Right hemisphere – receive input from left side of body Face & fingertips – most sensitive – largest part

39 Figure 12.8a Gustatory cortex (in insula) Primary motor cortex Premotor cortex Frontal eye field Working memory for spatial tasks Executive area for task management Working memory for object-recall tasks Broca’s area (outlined by dashes) Solving complex, multitask problems (a) Lateral view, left cerebral hemisphere Motor areas Prefrontal cortex Sensory areas and related association areas Central sulcus Primary somatosensory cortex Somatosensory association cortex Somatic sensation Taste Wernicke’s area (outlined by dashes) Primary visual cortex Visual association area Vision Auditory association area Primary auditory cortex Hearing Primary motor cortex Motor association cortex Primary sensory cortex Sensory association cortex Multimodal association cortex

40 Sensory Areas 2. Somatosensory Association Cortex – posterior to primary somatosensory cortex Integrates sensory inputs – temp, pressure, etc. – relayed to produce understanding of object being felt – size, texture, relationship

41 Figure 12.9 Genitals Intra- abdominal Primary somato- sensory cortex (postcentral gyrus) Sensory Sensory map in postcentral gyrus Posterior Anterior

42 Sensory Areas 3. Visual Areas – primary visual (striate) cortex Extreme posterior tip of occipital lobe Most buried deep in calcarine sulcus Largest Receives visual input from retina Visual association areas – surround primary – uses past visual experiences to interpret stimuli

43 Sensory Areas 4. Auditory Areas – primary auditory cortex – superior margin of temporal lobe Impulses from ear transmitted here – interpreted as pitch, loudness, location, etc. Auditory Association area – permits perception of sound Memories of past sounds

44 Sensory Areas 5. Olfactory cortex – Medial aspect of temporal lobes Small region – piriform lobe Smell receptors send impulses

45 Sensory Areas 6. Gustatory Cortex – taste stimuli Insula just deep to temporal lobe

46 Sensory Areas 7. Visceral Sensory Area – conscious perception of visceral stimulation Upset stomach, full bladder, lung bursting – holding breath to long

47 Sensory Areas 8. Vestibular (equilibrium) cortex – difficult to find Imaging – shows it in the posterior part of insula and adjacent parietal cortex

48 Figure 12.9 Genitals Intra- abdominal Primary somato- sensory cortex (postcentral gyrus) Sensory Sensory map in postcentral gyrus Posterior Anterior

49 Multimodal Association Areas Cortex – complex Input from multiple senses and outputs to multiple areas Meaning to info we receive, stores memories, ties to previous experiences, and decide actions Sensations, thoughts, and emotions

50 Multimodal Association Areas 1. Anterior Association Areas – frontal lobe – prefrontal cortex Most complicated Intellect, complex learning abilities (cognition), recall, and personality Working memory – abstract ideas, judgment, reasoning, persistence, and planning Abilities develop slowly in children – region of the brain that matures slowly

51 Multimodal Association Areas 2. Posterior Association areas – large region encompassing part of temporal, parietal, and occipital lobes Recognizes patterns and faces

52 Multimodal Association Areas 3. Limbic Association Areas – cingulate gyrus Parahippocampal gyrus Hippocampus Part of limbic system Emotional impact Sense of danger

53 Lateralization of Cortical Functioning Division of labor Each hemisphere has unique abilities not shared by its partner – lateralization Cerebral dominance – designates hemisphere – dominant for language Left hemisphere – 90 % - language, math, and logic Right – more free spirited – visual-spatial skills, intuition, emotion, artistic and musical skills Remaining 10 % of people – roles reversed Typically – male and left handed

54 Cerebral White Matter White matter – deep to cortical gray matter – responsible for communication between cerebral area and cerebral cortex and lower CNS centers Consists of – myelinated fibers classified according to the direction they run – 1. Commissural fibers – connect gray area of 2 hemispheres 2. Association fibers – connect different parts of same hemisphere 3. Projection fibers – cortex to rest of NS

55 Figure 12.10a Corona radiata Projection fibers Longitudinal fissure Gray matter White matter Association fibers Lateral ventricle Fornix Third ventricle Thalamus Pons Medulla oblongata Decussation of pyramids Commissural fibers (corpus callosum) Internal capsule Superior Basal nuclei Caudate Putamen Globus pallidus (a)

56 Cerebral White Matter Basal nuclei - Subcortical nuclei Deep within cerebral white matter Input from entire cerebral cortex Functions overlap with those of cerebellum Part in regulating attention and cognition

57 Figure 12.11a Fibers of corona radiata Corpus striatum (a) Projection fibers run deep to lentiform nucleus Caudate nucleus Thalamus Tail of caudate nucleus Lentiform nucleus Putamen Globus pallidus (deep to putamen)

58 Diencephalon Central core of forebrain Surrounded by cerebral hemispheres 3 parts – thalamus, hypothalamus, and epithalamus

59 Figure Corpus callosum Choroid plexus Thalamus (encloses third ventricle) Pineal gland (part of epithalamus) Posterior commissure Corpora quadrigemina Cerebral aqueduct Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum Septum pellucidum Interthalamic adhesion (intermediate mass of thalamus) Interven- tricular foramen Anterior commissure Hypothalamus Optic chiasma Pituitary gland Cerebral hemisphere Mammillary body Pons Medulla oblongata Spinal cord Mid- brain Fornix

60 Diencephalon - Thalamus Bilateral egg shaped nuclei Superolateral walls of 3 rd ventricle 80 % of diencephalon Relay station for info Nuclei – each functional specialty receives from a specific area Info sorted and edited

61 Diencephalon - Hypothalamus Below thalamus Caps brain stem and forms infolateral walls of 3 rd ventricle Extends from optic chiasma to mammillary bodies Infundibulum – stalk of hypothalamic tissue connects pituitary Main visceral controlling center of body

62 Diencephalon - Hypothalamus Homeostatic roles – 1.Autonomic Control Center – influences BP, rate and force of heart beat, digestive tract motility, pupil size, etc. 2.Emotional response – perception of pleasure, fear, and rage, biological rhythms and drives 3.Body temperature – monitor blood temperature and other thermoreceptors 4.Food Intake – hunger and satiety in response to changing blood levels 5.Water balance and thirst – osmoreceptors, ADH 6.Sleep – wake Cycles 7.Endocrine System functioning – releasing and inhibiting hormones

63 Diencephalon - Hypothalamus Number of Disorders – Obesity, sleep disturbances, dehydration, emotional impulses Infant failure to thrive – delay child’s growth or development when deprived of a warm, nurturing relationship

64 Diencephalon - Epithalamus Most dorsal Roof of 3 rd ventricle Pineal gland – secrets hormone melanin – sleep signal and antioxidant

65 Figure Corpus callosum Choroid plexus Thalamus (encloses third ventricle) Pineal gland (part of epithalamus) Posterior commissure Corpora quadrigemina Cerebral aqueduct Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum Septum pellucidum Interthalamic adhesion (intermediate mass of thalamus) Interven- tricular foramen Anterior commissure Hypothalamus Optic chiasma Pituitary gland Cerebral hemisphere Mammillary body Pons Medulla oblongata Spinal cord Mid- brain Fornix

66 Brain Stem Midbrain, pons, medulla oblongata 2.5 % of total brain mass Deep gray matter surrounded by white fibers Automatic behaviors Pathway Innervation of head

67 Midbrain 2 cerebral peduncles – “little feet” Cruscerbui – “leg” Fight or flight Reflexive responses – startle response

68 Figure 12.15a Optic chiasma View (a) Optic nerve (II) Mammillary body Oculomotor nerve (III) Crus cerebri of cerebral peduncles (midbrain) Trigeminal nerve (V) Abducens nerve (VI) Facial nerve (VII) Vagus nerve (X) Accessory nerve (XI) Hypoglossal nerve (XII) Ventral root of first cervical nerve Trochlear nerve (IV) Pons Middle cerebellar peduncle Pyramid Decussation of pyramids (a) Ventral view Spinal cord Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Diencephalon Thalamus Hypothalamus Diencephalon Brainstem Thalamus Hypothalamus Midbrain Pons Medulla oblongata

69 Pons Bulging brainstem region Conduction tracts Deep fibers – longitudinal Superficial – transverse and dorsal Cranial nerves

70 Figure 12.15b View (b) Crus cerebri of cerebral peduncles (midbrain) Infundibulum Pituitary gland Trigeminal nerve (V) Abducens nerve (VI) Facial nerve (VII) Vagus nerve (X) Accessory nerve (XI) Hypoglossal nerve (XII) Pons (b) Left lateral view Glossopharyngeal nerve (IX) Diencephalon Brainstem Thalamus Hypothalamus Midbrain Pons Medulla oblongata Thalamus Superior colliculus Inferior colliculus Trochlear nerve (IV) Superior cerebellar peduncle Middle cerebellar peduncle Inferior cerebellar peduncle Vestibulocochlear nerve (VIII) Olive

71 Medulla Oblongata Medulla Inferior part of brain stem Visceral motor nuclei – Cardio center – adjusts heart rate Vasomotor center – changes blood vessel diameter – Respiratory = respiratory rhythm – Various others – vomiting, coughing, swallowing, hiccupping, and sneezing

72 Figure 12.15c View (c) Diencephalon Brainstem Thalamus Hypothalamus Midbrain Pons Medulla oblongata Pineal gland Diencephalon Anterior wall of fourth ventricle (c) Dorsal view Thalamus Dorsal root of first cervical nerve Midbrain Superior colliculus Inferior colliculus Trochlear nerve (IV) Superior cerebellar peduncle Corpora quadrigemina of tectum Medulla oblongata Inferior cerebellar peduncle Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI) Pons Middle cerebellar peduncle Dorsal median sulcus Choroid plexus (fourth ventricle)

73 Cerebellum Cauliflower like 11 % of total brain mass Under occipital lobes Input from – cerebral motor cortex, brain stem, and sensory receptors Coordinated movement – driving, typing, etc

74 Figure 12.17b (b) Medulla oblongata Flocculonodular lobe Choroid plexus of fourth ventricle Posterior lobe Arbor vitae Cerebellar cortex Anterior lobe Cerebellar peduncles Superior Middle Inferior

75 Cerebellum Anatomy – bilateral symmetry 2 apple sized hemispheres Fola – pleat-like gyri Deep fissures Outer cortex – gray matter and deeply situated paired mass of gray matter Neurons – Purkinje cells

76 Cerebellum Cerebellar Processing – functional scheme 1.Cerebral cortex motor areas notify cerebellum of intent to initiate voluntary muscle control 2.Receives info from proprioceptors throughout the body – body position and momentum 3.Cerebellar cortex – calculated best way to coordinate force, direction, and extent 4.Superior peduncles – dispatches “blue print” for coordinated movement

77 Functional Brain Systems Network of neurons that work together but span large distances in brain Cannot be localized to specific regions

78 Limbic System Group of structures located in medial aspect of each cerebral hemisphere and diencephalon Cerebral structures that encircle upper part of brain stem Emotional or affective (feelings) brain Odors – trigger emotional reactions – rhinencephalon – “smell brain” Interacts with prefrontal lobes – intimate relationship between feelings and thoughts

79 Reticular Formation Extends central core of medulla oblongata, pons, and midbrain Loosely clustered neurons 1.Midline raphe neuclei 2.Medial (large cell) group 3.Lateral (small cell) group -flung axonal connections -Reticular activating system (RAS) – impulses from great ascending sensory tracts – keep them active and enhance effect on cerebrum -Filter sensory inputs -Inhibited sleep centers -Depressed by alcohol, sleep aid drugs, and tranquilizers

80 Higher Mental Functions Brainwaves reflect the electrical activity of higher mental functions Electroencephalogram – record some aspects of activity Electrodes on scalp measure potential energy differences Brainwaves – generated by synaptic activity at surface of cortex

81 Figure 12.20a (a) Scalp electrodes are used to record brain wave activity (EEG).

82 Brain Waves –4 categories 1.Alpha Waves – 8-13 Hz -Regular rhythmic -Low amplitude -Synchronous waves -Brain – ‘idling’ – calm, relaxed state of wakefulness

83 Brain Waves 2. Beta Waves – 14-30Hz – rhythmic, but not as regular, occur when mentally alert 3. Theta Waves – 4-7 Hz – irregular, common in children, uncommon in adults 4. Delta Waves – 4 Hz or less – high amplitude waves, deep sleep – reticular activating system is damped – anesthesia - Indicated brain damage in awake adults

84 Brain Waves Change with age, sensory stimuli, brain disease and chemical state of body Flat EEG – clinical evidence of brain death Epilepsy – seizures – torrent of electrical charges of groups of brain neurons Uncontrolled activity – no other messages can get through

85 Figure 12.20b Alpha waves —awake but relaxed Beta waves —awake, alert Theta waves —common in children Delta waves —deep sleep (b) Brain waves shown in EEGs fall into four general classes. 1-second interval

86 Consciousness Encompass conscious perception of sensations, voluntary initiation and control of movements and capabilities associated with higher mental functioning Defined by behavior in response to stimuli – Alertness – Drowsiness or lethargy – Stupor – coma

87 Consciousness Difficult to determine Current suppositions – 1.Simultaneous activity of large areas of cerebral cortex 2.It is superimposed on other types of neural activity 3.Is it holistic and totally interconnected

88 Consciousness Fainting or Syncope – brief loss of consciousness Most often from inadequate cerebral blood flow due to low BP Coma – total unresponsiveness Not deep sleep – oxygen level lower than deep sleep Blows to head – widespread cerebral or brain stem trauma Tumors or infections, hypoglycemia, drug overdose, kidney failure Brain Death – irreparable damage to brain

89 Sleep and Sleep Wake Cycles Sleep – state of partial unconsciousness from which a person can be aroused by stimulation Coma – cannot be aroused

90 Types of Sleep 2 major types that alternate throughout the sleep cycle 1.Non-rapid eye movement (NREM) 2.Rapid Eye movement (REM) - Defined by EEG patterns

91 Sleep 1 st minutes – 2 stages of NREM Then stage 3 and 4 – NREM- slow wave sleep Deeper sleep – EEG wave declines – amplitude increase 90 minutes – NREM stage 4 – changes rapidly – appears to backtrack until alpha waves appear – onset of REM sleep – Increase in heart rate – Increase respiratory rate – Increase in blood pressure – Decrease in gastrointestinal activity – Increase in oxygen use – Eyes move rapidly, skeletal muscles limp, dreams

92 Figure 12.21a Awake (a) Typical EEG patterns REM: Skeletal muscles (except ocular muscles and diaphragm) are actively inhibited; most dreaming occurs. NREM stage 1: Relaxation begins; EEG shows alpha waves, arousal is easy. NREM stage 2: Irregular EEG with sleep spindles (short high- amplitude bursts); arousal is more difficult. NREM stage 3: Sleep deepens; theta and delta waves appear; vital signs decline. NREM stage 4: EEG is dominated by delta waves; arousal is difficult; bed-wetting, night terrors, and sleepwalking may occur.

93 Sleep Patterns Alternating patterns of sleep and wakefulness Natural circadian, or 24 hour, rhythm Hypothalamus response Suprachaismatic nucleus – biological clock regulates preoptic nucleus – sleep inducing center

94 Sleep Patterns Young/middle aged adult – 4 stages of NREM then alternate with occasional partial analysis REM ~ every 90 minutes 1 st REM – 5-10 minutes long Final REM – minutes long Wake – hypothermic neurons release peptides (exins) “wakeup” chemical

95 Figure 12.21b (b) Typical progression of an adult through one night’s sleep stages Awake REM Stage 1 Stage 2 Non REM Stage 3 Stage 4 Time (hrs)

96 Importance of Sleep Slow wave sleep – restorative – neural activity winds down REM – deprived – moody and depressed – Analyze days events – Get rid of meaning less communication Alcohol and sleep meds – suppress REM but not slow wave sleep Tranquilizers – suppress slow wave more than REM

97 Importance of Sleep Requirements – infant – 16 hrs 7 ½  8 ½ - early adulthood REM – ½ sleep time in infants – declines until 10 years old Stabilizes ~ 25% Stage 4 – declines steadily – often disappears by age 60

98 Sleep Narcolepsy – lapse into REM from an awake state Lasts ~ 15 min, can occur at any time, most often triggered by a pleasurable event – Fewer cells in hypothalamus that secrete orexins Insomnia – inability to obtain amount or quantity of sleep needed to adequately function – Varies – 4 -9 hrs/day Sleep Apnea – temporary cessation of breathing during sleep – Victim wakes due to hypoxia – Associated with obesity – Made worse by alcohol – Must wear a mask when sleeping

99 Language Involves almost all of association cortex on left side 2 important areas – 1.Broca’s area – can’t speak, but can understand 2.Wericke’s area – can speak but can’t understand - Areas work together to form a single implementation system

100 Memory Storage and retrieval of information essential for learning and incorporating experiences Stages 1.Short term Memory (STM) – working memory -Limited to 7 or 8 chunks of information 2. Long term Memory (LTM) – limitless capacity -Can be forgotten -Memory bank changes with time -Ability to store and retrieve information declines with age

101 From STM to LTM - 1.Emotional state – we learn when surprised, alert, motivated, or aroused -Norephinephrine released when excited 2. Rehearsal – repetition – enhances memory 3. Association – tying new info to old info already stored 4. Automatic Memory – not all impressions are consciously formed - Memory consolidation – fitting new facts into knowledge already stored

102 Figure Outside stimuli General and special sensory receptors Data transfer influenced by: Excitement Rehearsal Association of old and new data Long-term memory (LTM) Data permanently lost Afferent inputs Retrieval Forget Data selected for transfer Automatic memory Data unretrievable Temporary storage (buffer) in cerebral cortex Short-term memory (STM)

103 Categories of Memory Declarative (fact) memory – learning explicit info – names, faces, dates Non-declarative memory – less conscious Procedural (skills) memory – ex. Playing the piano Motor Memory – riding a bike Emotional memory – pounding heart when see a rattlesnake

104 Brain Structures Visual memories – stored in occipital cortex Music – temporal cortex Damage to hippocampus and medial temporal lobe result in slight memory loss Bilateral destruction - amnesia

105 Protection of Brain Nervous tissue – soft and delicate Brain – protected by bone, membranes, and CSF Harmful substances – blood-brain barrier

106 Figure Skin of scalp Periosteum Falx cerebri (in longitudinal fissure only) Blood vessel Arachnoid villus Pia mater Arachnoid mater Dura mater Meningeal Periosteal Bone of skull Superior sagittal sinus Subdural space Subarachnoid space

107 Meninges 3 connective tissue membranes that lie external to CNS organs Functions: – Cover and protect CNS – Protect blood vessels and enclose venous sinuses – Contain cerebral spinal fluid – Form partitions in skull

108 Meninges Dura Matter “tough mother’ Strongest meninx Surround brain – 2 layered sheet of fibrous CT Dura septa –dura matter extends into brain, limit excessive movement of brain Arachnoid Matter Middle meninx Loose brain covering

109 Figure Skin of scalp Periosteum Falx cerebri (in longitudinal fissure only) Blood vessel Arachnoid villus Pia mater Arachnoid mater Dura mater Meningeal Periosteal Bone of skull Superior sagittal sinus Subdural space Subarachnoid space

110 Figure 12.25a Falx cerebri Superior sagittal sinus Straight sinus Crista galli of the ethmoid bone Pituitary gland Falx cerebelli (a) Dural septa Tentorium cerebelli

111 Meninges Pia Mater – “gentle matter” Delicate connective tissue Clings to brain Meningitis – inflammation of meninges Serious threat – can spread to CNS Encephalitis – brain inflammation

112 Cerebrospinal Fluid CSF – found in and around the brain Liquid cushion Prevents brain from crushing itself Protects against trauma Watery “broth” similar to blood plasma – less proteins and plasma CSF contains more Na, Cl, and H, and less Ca and K

113 Figure 12.26a Superior sagittal sinus Arachnoid villus Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater Right lateral ventricle (deep to cut) Choroid plexus of fourth ventricle Central canal of spinal cord Choroid plexus Interventricular foramen Third ventricle Cerebral aqueduct Lateral aperture Fourth ventricle Median aperture (a) CSF circulation CSF is produced by the choroid plexus of each ventricle. 1 CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord. 2 CSF flows through the subarachnoid space. 3 CSF is absorbed into the dural venous sinuses via the arachnoid villi

114 Blood Brain Barrier Protective mechanism that helps maintain a stable environment for brain If brain exposed to chemical variations in blood – neurons would fire uncontrollably Blood born substances must pass through 3 layers before they reach neurons – 1. epithelium of capillary walls 2. relatively thick basal lamina surrounding capillaries 3. bulbous “feet” of astrocytes clinging to capillaries - Barrier is selective – nutrients pass, wastes can not

115 Figure 11.3a (a) Astrocytes are the most abundant CNS neuroglia. Capillary Neuron Astrocyte

116 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

117 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) is the only approved treatment for stroke

118 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

119 The Spinal Cord: Embryonic Development By week 6, there are two clusters of neuroblasts – Alar plate—will become interneurons; axons form white matter of cord – Basal plate—will become motor neurons; axons will grow to effectors Neural crest cells form the dorsal root ganglia sensory neurons; axons grow into the dorsal aspect of the cord

120 Figure White matter Neural tube cells Central cavity Alar plate: interneurons Dorsal root ganglion: sensory neurons from neural crest Basal plate: motor neurons

121 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

122 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

123 Spinal Cord: Protection Denticulate ligaments: extensions of pia mater that secure cord to dura mater Filum terminale: fibrous extension from conus medullaris; anchors the spinal cord to the coccyx

124 Figure Ligamentum flavum Supra- spinous ligament Lumbar puncture needle entering subarachnoid space Filum terminale Inter- vertebral disc T 12 L5L5 Cauda equina in subarachnoid space Dura mater L5L5 L4L4 S1S1 Arachnoid matter

125 Figure 12.29a Cervical enlargement Dura and arachnoid mater Lumbar enlargement Conus medullaris Cauda equina Filum terminale Cervical spinal nerves Lumbar spinal nerves Sacral spinal nerves Thoracic spinal nerves (a) The spinal cord and its nerve roots, with the bony vertebral arches removed. The dura mater and arachnoid mater are cut open and reflected laterally.

126 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

127 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

128 Figure 12.31a (a) Cross section of spinal cord and vertebra Epidural space (contains fat) Pia mater Spinal meninges Arachnoid mater Dura mater Bone of vertebra Subdural space Subarachnoid space (contains CSF) Dorsal root ganglion Body of vertebra

129 Figure 12.31b (b) The spinal cord and its meningeal coverings Dorsal funiculus Dorsal median sulcus Central canal Ventral median fissure Pia mater Arachnoid mater Spinal dura mater Gray commissure Dorsal horn Gray matter Lateral horn Ventral horn Ventral funiculus Lateral funiculus White columns Dorsal root ganglion Dorsal root (fans out into dorsal rootlets) Ventral root (derived from several ventral rootlets) Spinal nerve

130 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

131 Figure Somatic sensory neuron Dorsal root (sensory) Dorsal root ganglion Visceral sensory neuron Somatic motor neuron Spinal nerve Ventral root (motor) Ventral horn (motor neurons) Dorsal horn (interneurons) Visceral motor neuron Interneurons receiving input from somatic sensory neurons Interneurons receiving input from visceral sensory neurons Visceral motor (autonomic) neurons Somatic motor neurons

132 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

133 Pathway Generalizations Pathways decussate (cross over) Most consist of two or three neurons (a relay) Most exhibit somatotopy (precise spatial relationships) Pathways are paired symmetrically (one on each side of the spinal cord or brain)

134 Figure Ascending tractsDescending tracts Fasciculus gracilis Dorsal white column Fasciculus cuneatus Dorsal spinocerebellar tract Lateral spinothalamic tract Ventral spinothalamic tract Ventral white commissure Lateral corticospinal tract Lateral reticulospinal tract Ventral corticospinal tract Medial reticulospinal tract Rubrospinal tract Vestibulospinal tract Tectospinal tract Ventral spinocerebellar tract

135 Ascending Pathways Consist of three neurons First-order neuron – Conducts impulses from cutaneous receptors and proprioceptors – Branches diffusely as it enters the spinal cord or medulla – Synapses with second-order neuron

136 Ascending Pathways Second-order neuron – Interneuron – Cell body in dorsal horn of spinal cord or medullary nuclei – Axons extend to thalamus or cerebellum

137 Ascending Pathways Third-order neuron – Interneuron – Cell body in thalamus – Axon extends to somatosensory cortex

138 Ascending Pathways Two pathways transmit somatosensory information to the sensory cortex via the thalamus – Dorsal column-medial lemniscal pathways – Spinothalamic pathways Spinocerebellar tracts terminate in the cerebellum

139 Dorsal Column-Medial Lemniscal Pathways Transmit input to the somatosensory cortex for discriminative touch and vibrations Composed of the paired fasciculus cuneatus and fasciculus gracilis in the spinal cord and the medial lemniscus in the brain (medulla to thalamus)

140 Figure 12.34a (2 of 2) Medulla oblongata Fasciculus cuneatus (axon of first-order sensory neuron) Fasciculus gracilis (axon of first-order sensory neuron) Axon of first-order neuron Muscle spindle (proprioceptor) Joint stretch receptor (proprioceptor) Cervical spinal cord Touch receptor Medial lemniscus (tract) (axons of second-order neurons) Dorsal spinocerebellar tract (axons of second-order neurons) Nucleus gracilis Nucleus cuneatus Lumbar spinal cord (a)Spinocerebellar pathway Dorsal column–medial lemniscal pathway

141 Figure 12.34a (1 of 2) Primary somatosensory cortex Axons of third-order neurons Thalamus Cerebrum Midbrain Cerebellum Pons (a)Spinocerebellar pathway Dorsal column–medial lemniscal pathway

142 Anterolateral Pathways Lateral and ventral spinothalamic tracts Transmit pain, temperature, and coarse touch impulses within the lateral spinothalamic tract

143 Figure 12.34b (2 of 2) Axons of first-order neurons Temperature receptors Lateral spinothalamic tract (axons of second-order neurons) Pain receptors Medulla oblongata Cervical spinal cord Lumbar spinal cord (b)Spinothalamic pathway

144 Figure 12.34b (1 of 2) Primary somatosensory cortex Axons of third-order neurons Thalamus Cerebrum Midbrain Cerebellum Pons (b)Spinothalamic pathway

145 Spinocerebellar Tracts Ventral and dorsal tracts Convey information about muscle or tendon stretch to the cerebellum

146 Figure 12.34a (2 of 2) Medulla oblongata Fasciculus cuneatus (axon of first-order sensory neuron) Fasciculus gracilis (axon of first-order sensory neuron) Axon of first-order neuron Muscle spindle (proprioceptor) Joint stretch receptor (proprioceptor) Cervical spinal cord Touch receptor Medial lemniscus (tract) (axons of second-order neurons) Dorsal spinocerebellar tract (axons of second-order neurons) Nucleus gracilis Nucleus cuneatus Lumbar spinal cord (a)Spinocerebellar pathway Dorsal column–medial lemniscal pathway

147 Figure 12.34a (1 of 2) Primary somatosensory cortex Axons of third-order neurons Thalamus Cerebrum Midbrain Cerebellum Pons (a)Spinocerebellar pathway Dorsal column–medial lemniscal pathway

148 Descending Pathways and Tracts Deliver efferent impulses from the brain to the spinal cord – Direct pathways—pyramidal tracts – Indirect pathways—all others

149 Descending Pathways and Tracts Involve two neurons: 1.Upper motor neurons Pyramidal cells in primary motor cortex 2.Lower motor neurons Ventral horn motor neurons Innervate skeletal muscles

150 The Direct (Pyramidal) System Impulses from pyramidal neurons in the precentral gyri pass through the pyramidal (corticospinal)l tracts Axons synapse with interneurons or ventral horn motor neurons The direct pathway regulates fast and fine (skilled) movements

151 Figure 12.35a (1 of 2) Primary motor cortex Internal capsule Cerebral peduncle Midbrain Cerebellum Cerebrum Pons (a) Pyramidal cells (upper motor neurons) Pyramidal (lateral and ventral corticospinal) pathways

152 Figure 12.35a (2 of 2) Medulla oblongata Cervical spinal cord Skeletal muscle Pyramids Decussation of pyramid Lateral corticospinal tract Ventral corticospinal tract Lumbar spinal cord Somatic motor neurons (lower motor neurons) (a)Pyramidal (lateral and ventral corticospinal) pathways

153 Indirect (Extrapyramidal) System Includes the brain stem motor nuclei, and all motor pathways except pyramidal pathways Also called the multineuronal pathways

154 Indirect (Extrapyramidal) System These pathways are complex and multisynaptic, and regulate: – Axial muscles that maintain balance and posture – Muscles controlling coarse movements – Head, neck, and eye movements that follow objects

155 Indirect (Extrapyramidal) System Reticulospinal and vestibulospinal tracts— maintain balance Rubrospinal tracts—control flexor muscles Superior colliculi and tectospinal tracts mediate head movements in response to visual stimuli

156 Figure 12.35b (1 of 2) Midbrain Cerebellum Cerebrum Red nucleus Pons Rubrospinal tract(b)

157 Figure 12.35b (2 of 2) Medulla oblongata Cervical spinal cord Rubrospinal tract (b)

158 Spinal Cord Trauma Functional losses – Parasthesias Sensory loss – Paralysis Loss of motor function

159 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

160 Spinal Cord Trauma 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

161 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

162 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

163 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

164 Developmental Aspects of the CNS CNS is established during the first month of development Gender-specific areas appear in both brain and spinal cord, depending on presence or absence of fetal testosterone Maternal exposure to radiation, drugs (e.g., alcohol and opiates), or infection can harm the developing CNS Smoking decreases oxygen in the blood, which can lead to neuron death and fetal brain damage

165 Developmental Aspects of the CNS The hypothalamus is one of the last areas of the CNS to develop Visual cortex develops slowly over the first 11 weeks Neuromuscular coordination progresses in superior-to-inferior and proximal-to-distal directions along with myelination

166 Developmental Aspects of the CNS Age brings some cognitive declines, but these are not significant in healthy individuals until they reach their 80s Shrinkage of brain accelerates in old age Excessive use of alcohol causes signs of senility unrelated to the aging process


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