The Central Nervous System Brain – superiorly Spinal Cord - inferiorly
Figure 12.3
4 Protective Structures of the Brain <ul><li>Cranium  – bony helmet composed of the 8 cranial bones – frontal, parietal(pa...
Figure 12.24
Figure 12.24b
Figure 12.5
Figure 12.26
Figure 12.27
Figure 12.12
The Brain <ul><li>Weight: 3.5Ib ( 1600 g) </li></ul><ul><li>4 major regions: </li></ul><ul><li>Cerebrum </li></ul><ul><li>...
The Cerebrum <ul><li>Superior region of the brain – accounts for 83% of total brain mass  </li></ul><ul><li>Surface marked...
Figure 12.6c, d
Figure 12.6a, b
Figure 12.7
The Sulci in the cerebral hemispheres <ul><li>Central Sulcus –  separates the frontal lobe from the parietal lobe. The gyr...
Figure 12.6a
Figure 12.8a
3 regions in each Cerebral hemisphere <ul><li>Cerebral Cortex –  highly convoluted and 2-4 mm thick; accounts for 40% of t...
Figure 12.11b
3 Functional areas in the Cerebral Cortex  <ul><li>Motor areas  – control voluntary movements. </li></ul><ul><li>consist o...
3 Functional areas in the Cerebral Cortex
The Cerebral Gray Cortex – Motor areas <ul><li>Consists of  4 functional areas: </li></ul><ul><li>Primary motor cortex  – ...
Decussation of the Pyramids
Cerebral White Matter
Cerebral White Matter <ul><li>Second region in the cerebrum deep to the cerebral cortex; consists of myelinated tracts </l...
Basal Nuclei
Projection tracts
Basal Nuclei <ul><li>Islands of gray matter in the cerebral white matter </li></ul><ul><li>3 major Basal Nuclei: </li></ul...
Ventricles
Ventricles <ul><li>Cavities in the brain that contain CSF </li></ul><ul><li>Lateral ventricles – each cerebral hemisphere ...
Diencephalon
Diencephalon <ul><li>Consists of 3 paired structures: </li></ul><ul><li>Thalamus  – the relay station for sensory inputs t...
Brain Stem
Figure 12.15c
Table 12.1.1
Figure 12.14
Brain Stem <ul><li>Composed of an outer white matter and an inner gray matter  </li></ul><ul><li>Consists of 3 regions: </...
Cranial Nerves III - XII
Figure 12.15b
2 pigmented nuclei in the Midbrain
CEREBELLUM
The Arbor Vitae
Cerebellum <ul><li>Composed of outer gray matter and an inner white matter; the cerebellar inner white matter resembles a ...
Table 12.1.2
The Spinal Cord
The Spinal Cord
The Spinal Cord <ul><li>Second part of the CNS inferior to the brain </li></ul><ul><li>Extends from the foramen magnum to ...
3 Protective structures of the Spinal Cord
3 protective structures of the Spinal Cord <ul><li>Vertebral column  –  forms a bony encasement </li></ul><ul><li>Spinal M...
Figure 12.29c
Figure 12.29d
Cervical and Lumbar enlargements <ul><li>Cervical enlargement  – located in the cervical region; spinal cervical nerves fr...
Lumbar Tap
Lumbar Tap <ul><li>CSF is taken from the subarachnoid space for analysis, if meningitis is suspected. </li></ul><ul><li>Th...
Gray Matter and White Matter
The Gray Matter and the White Matter of the Spinal Cord <ul><li>The inner GRAY MATTER  is “H”-shaped or butterfly-shaped; ...
Figure 12.32
Ascending Tracts -  Sensory inputs
Table 12.2.2
Descending Tracts – Motor output
Table 12.3.1
Terminology <ul><li>Paresthesia   – sensory loss </li></ul><ul><li>Paralysis  –  loss of motor function </li></ul><ul><li>...
Amyotrophic Lateral Sclerosis (ALS) =  Lou Gehrig’s disease <ul><li>Involves progressive destruction of ventral horn motor...
Lumbar Myelomeningocele  – Spina Bifida cystica  –  incomplete formation of the vertebral arches
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  • Started here, 3 rd bullet… then lobes, then slide 14
  • Then 19
  • Now here… CEREBRUM – a section through the cerebrum -&gt; 3 regions Outer cerebral cortex Inner cerebral white matter Islands of nuclei called the basal nuclei CEREBRAL CORTEX highly convoluted, appears gray due to the presence of unmyelinated structures = cell bodies, dendrites, supporting cells 2-4 mm thick but it accounts for 40% of the total brain mass composed of 6 layers of billions of neurons has 3 functional areas motor areas sensory areas association areas Motor areas of the cerebral cortex  4 areas (slide 21?) primary motor cortex  located in the PRECENTRAL GYRUS in the frontal lobe neurons in the precentral gyrus called the PYRAMIDAL CELLS have large tracts that descend to the spinal cord to control voluntary precise movements The pyramidal tracts (= coricospinal tracts) decossate (cross over) to control voluntary movements of skeletal muscle on opposites of the body Pyramidal cells in the LEFT precentral gyrus  control voluntary movement of skeletal muscles on the RIGHT side of the body; and vice versa Hence, the cerebral cortex exhibits contralateral control of voluntary movements of the skeletal muscle Damage to the left precentral gyrus will result in loss of voluntary motor function on the RIGHT side of the body – paralysis of the right side of the body; and vica versa premotor cortex  located in the frontal lobe anterior to the precentral gyrus controls voluntary skilled skeletal muscle movements that are patterned or repetitious in nature… ex. Typing Hence, the premotor cortex is referred to as the “memory bank for skilled patterned skeletal muscle activities” broca’s area = speech motor area  located in the frontal lobe and is below the premotor cortex controls skeletal muscles involved in speech production damage to the broca’s area results in the loss of speech located in one hemisphere, mostly in the LEFT cerebral hemisphere **Insult (stroke) involving the left cerebral hemisphere  involves the left precentral gyrus  broca’s area LEADS TO RIGHT SIDE PARALYSIS AND LOSS OF SPEECH frontal eye field (4 th area) located in the frontal lobe of both hemispheres controls skeletal muscles that control eye movements On to slide 21 (we were already on it, just writing stuff there
  • Sensory area of the cerebral cortex primary somatosensory corex  located in the postcentral gyrus (in the parietal lobe) receives sensory info from receptors in the skin, skeletal muscle, joints, for SPATIAL DISCRIMINATION  ability to differentiate areas of the body being stimulated primary visual cortex  located in the occipital lobe of both hemispheres receives sensory input from the retinae in the eyes. The primary somatosensory cortex and the primary visual cortex exhibit contralateral inputs Sensory inputs from the left side of the body received by the RIGHT postcentral gyrus and vice versa Sensory inputs from the retinae (vision) in the left eye go to the RIGHT occipital cortex  right PRIMARY VISUAL CORTEX 3) primary auditory (hearing) cortex is located in the temporal lobes of both cerebral hemispheres 4) primary gustatory (taste) cortex is located in the insula of both cerebral hemispheres 5) primary olfactory (smell) cortex is located in the temporal lobes; emotional aspect in frontal lobe 3 rd functional area in the cerebral cortex association areas  each sensory area has an association area. The association areas integrate/interpret and appreciate the sensory input information
  • 2 nd region of the cerebrum  cerebral white matter  region DEEP to the cerebral cortex cerebral white matter is composed of MYELINATED axons (“whitish”)  bundle to form TRACTS  3 types of tracts Commissural tracts = Commissures connect areas of the 2 cerebral hemispheres ex. CORPUS CALLOSUM which connects to cerebral hemispheres medially Association tracts  connect areas within the same cerebral hemisphere; ex. ARCUATE FASCICULATE which connects the broca’s area to the Wernicke’s area in the left cerebral hemisphere for language acquisition meaning that you have words that make sense in a coherent sentence See next slide
  • 11/10 Cerebral white matter = 3 types of tracts Commissural tracts  commissures Association tracts Projection tracts Run vertically between the cerebral cortex… the lower brain regions (=subcortical regions) and the spinal cord 2 types descending projection tracts – come from cerebral cortex ascending projection tracts – TO the cerebral cortex for interpretation, see next slide for picture… now what opoku said descending projection tracts  motor tracts carrying efferent impulses from the cerebral cortex EX. Pyramidal (corticospinal) tracts descending from the precentral gyri ascending projection tracts  see slide 27 for pictures, sensory inputs = afferent impulses carried TO the cerebral cortex from sensory receptors for interpretation EX. Spinothalamic tract Next slide
  • 3 rd region in the cerebrum  basal nuclei = islands of gray matter in the cerebral white matter (nucleus = a cluster of neuronal cell bodies in the CNS) 3 major basal nuclei (superior  inferior) Caudate Putamen Globus pallidus b&amp;c above = lentiform nucleus All three above = CORPUS STRIATUM As the pyramidal tracts coursing through them give the 3 nuclei a striated appearance (corpus striatum = “striated body”) Function of the basal nuclei  involved in the initiation and monitoring of intensity of voluntary movement  skeletal muscle movement 2 lateral ventricles are located in the 2 cerebral hemispheres  each cerebral hemisphere contains a lateral ventricle 2 lateral ventricles are separated by the septum pellicidum 2 lateral ventricles are connected inferiorly to the 3 rd ventricle by the interventricular foramen (foramen of Monro)
  • 2 nd region of the adult (postnatal) brain  DIENCEPHALON contains the 3 rd ventricle located below the cerebrum consists of 3 pairs of gray matter structures (on next slide)
  • Missed some stuff… thalamus accounts for 80% of the total mass of the diencephalon The cell bodies (gray matter) in the thalamus act as relay centers for sensory info projected to the cerebral cortex. Hence, the thalamus is referred to as the “GATEWAY TO THE CEREBRAL CORTEX” 2 of such relay centers in the thalamus  lateral geniculate nucleus (LGN)  medial geniculate nucleus (MGN) LGN is the visual relay center MGN is the auditory relay center Hypothalamus is located below the thalamus major endocrime gland  9 hormones controls all body functions to maintain homeostasis Epithalamus  dorsal to the thalamus contains an endocrine gland  pineal gland  secretes a hormone called melatonin “sleep inducting chemical” that works with the suprachiasmatic nucleus in the hypothalamus to bring about sleep
  • Midbrain Cerebral peducles Cerebral aqueducts Corpora quadrigemina  superior colliculi and the inferior colliculi Superior cerebellar peduncles which connect the motor tracts passing the midbrain to the cerebellum 2 pigmented nuclei  red nuclei and the substantia nigra Red nuclei – relay centers for descending motor tracts that control limb flexion Substantia nigra  appear black due to high concentration of melanin (melanin used in the production/synthesis of the neurotransmitter DOPAMINE) Hence, the neurons in the substantia nigra are referred to as dopaminergic neurons  project to the BASAL NUCLEI (in the cerebrum) to modulate the activities of the basal nuclei  for the initiation of skilled, coordinated skeletal muscle movements Damage or degeneration of the dopaminergic neurons from the substantia nigra to the basal nuclei result in the symptoms of parkinson’s disease ========================== -resting tremor -masklike facial expression (expressionless) -slow to initiate voluntary movements -shuffling gait -slurred speech The cell bodies of 2 cranial nerves are located in the midbrain  CN III, IV Now, looking at pons
  • Pons  middle region of the brain stem between the midbrain and the medulla oblongata Pons contains conducting tracts  projection tracts between the cerebral cortex and the spinal cord  tracts travel through the middle cerebellar peduncles to the cerebellum Pons also contains the respiratory centers  apneustic center and pneumotaxic center apneustic center  controls the rate of breathing pneumotaxic center  controls the depth of breathing Pons will have cell bodies for 3 cranial nerves  CN V, VI, VII MEDULLA OBLONGATA most inferior region of the brain stem continued by the spinal cord at the level of the Foramen magnum of the skull contains: inferior cerebellar peduncles that connect the medulla to the cerebellum cell bodies for cranial nerves VIII-XII Ventral aspect of the medulla, the descending pyramidal tracts decussate (cross-over) and the point of crossing over is referred to as the DECUSSATION of the PYRAMIDS  explains the contralateral control of voluntary movements in the body  explains why the left precentral gyrus controls the voluntary movements (of skeletal muscles) on the right side and vice versa Medulla is responsible for something and contains these structures… Cardiovascular center  cardiac center = regulates the heart rate and stroke volume vasomotor center  regulates the diameter of blood vessels Cardiovascular center regulates in blood pressure 2) Respiratory center  apneustic center and pneumotaxic center 3) Swallowing center 4) Coughing center 5) Emetic (vomiting) center)
  • 4 th region of the adult (postnatal) brain  CEREBELLUM Accounts for about 11% of the total brain mass Located behind (posterior) to the brain stem and connected to the brain stem via the superior, middle, and inferior cerebellar peduncles Also located inferior to the occipital lobes of the cerebrum (or cerebral hemispheres) The cerebellum is separated from the occipital lobes by the transverse fissure (deep sulcus) Cerebellum  divided into 2 cerebellar hemispheres held together medially by the VERMIS Each cerebellar hemisphere is divided into 3 lobes Anterior lobe Posterior lobe Flocculonodular lobe 1&amp;2 can be viewed on the external surface 3 cannot be viewed on the external surface of the cerebellar hemispheres 3 is located deep to the vermis A section through the cerebellum will reveal 2 regions outer gray matter and inner white matter inner white matter branches into a tree-like pattern referred to as ARBOR VITAE (the tree of life) Function of the cerebellum  well-coordinated smooth, skillful skeletal muscle movements also involved in balance (equilibrium) involved in maintenance of posture Alcohol intoxication affects the cerebellum the most.
  • 11/15 CNS  Superior brain and inferior spinal cord In the adult  the spinal cord is about 42 cm (17 inches) long and it extends from the foramen magnum to the 1 st lumbar vertebra. 3 protective structures bony structure  vertebral column meninges CSF Slide 48
  • Spinal cord extends from the foramen magnum  L1 appears tapered and ends in cone-shaped structure called the CONUS MEDULLARIS (fibrous extensions from the conus medullaris covered by pia mater) the whole thing in parentheses is called the FILUM TERMINALE attaches to the coccyx to anchor the spinal cord vertically 31 pairs of spinal nerves exit through intervertebral foramina into the PNS 8 pairs of vervical nerves 12 pairs of thoracic 5 lumbar 5 sacral 1 coccyx These 31 pairs of spinal nerves innervate structures outside of the CNS  structures in the PNS spinal cord  2 enlargements (slide 52)
  • 49
  • If you look at the vertebral column  C1 to L1 vertebrae provide protection ------------------------- Meninges  3 types Dura mater – outermost meninx, SINGLE-LAYERED and it does not line the internal surface of the vertebrae – there is no contact A space between the verebrae and the dura mater called the EPIDURAL SPACE is present the epidural space contains fat and veins  site for epidural anesthesia to block pain the single layered dura mater of the spinal cord is also referred to as the SPINAL DURAL SHEATH Arachnoid mater – middle meninx  separated from the spinal dural sheath by a space called the SUBDURAL SPACE The arachnoid mater is separated from the pia mater (innermost meninx) by a space called the SUBARACHNOID SPACE  contains CSF Pia mater – innermost meninx  forms lateral structures called DENTICULATE ligaments  anchor the spinal cord laterally to the spinal dural sheath. Pia mater attaches to the surface of the spinal cord (she showed us a picture on slide 50) went back to slide 48 3 rd protective structure is called the Cerebrospinal fluid (CSF)  contained in the subarachnoid space (around the spinal cord) and in the CENTRAL CANAL  runs vertically through the core of the spinal cord (inside the spinal cord) The central canal extends and receives CSF from the 4 th ventricle located in the brain stem Function of CSF  provide nutrients, remove metabolic wastes, fluid cushion Slide 47
  • Cervical enlargement  superior enlargement in the cervical region of the spinal cord Spinal nerves from the cervical enlargements will innervate skeletal muscles in the upper limbs  nerves control voluntary movements of the upper limbs ================= Lumbar enlargement  inferior to cervical enlargement around the lower thoracic and upper lumbar region of the spinal cord spinal nerves from the lumbar enlargement innervate and control voluntary movements of skeletal muscle in the lower limbs Damage or transection of the enlargements will result in paralysis  FLACCID paralysis Transection (cutting) of the spinal cord at or above the cervical enlargement will result in paralysis of all 4 limbs  both upper and lower limbs  quadriplegia Transection of the spinal cord below the cervical enlargement but above the lumbar enlargemnet will only result in paralysis of the lower limbs  paraplegia **note hemiplegia  paralysis of one side of the body is due to damage to the precentral gyri in the cerebral coretex (BRAIN DAMAGE instead of spinal cord damage) Hemiplegia is also referred to as SPASTIC paralysis =========================== The spinal nerves below L1 form a collection of nerve roots called the CAUDA EQUINA as they exit their foramina below the L1 =========================== Slide 56
  • Cross section through the spinal cord  outer white matter and inner gray matter The outer white matter  composed of mainly myelinated tracts that communicate info between area within the spinal cord and the brain Based on orientation we have 3 areas or columns called funiculi These funiculi contain 3 types of tracts  ascending tracts, descending tracts, interneurons Ascending tracts  send sensory information to the brain Descending tracts  send motor information from the brain to the spinal cord Interneurons  communication within the spinal cord Inner gray matter  shaped like an “H” or a butterfly  mirror images connected by the gray commisure  immediately surrounds the central canal Regions with gray matter  dorsal horns central horns lateral horns  spinal cord at the level of the thoracic or L1 region contain cell bodies of the sympathetic fibers of the autonomic nervous system ============ 11/17 Spinal cord Outer white matter Ascending tracts Descending tracts Interneurons = transverse tracts Inner gray matter shapped like the letter “H” or a butterfly  mirror image connected by a band of gray matter called the GRAY COMMISSURE Each side consists of a) DORSAL HORN  houses cell bodies for interneurons b) Ventral horn  houses cell bodies for somatic neurons that innervate the skeletal muscles c) Lateral horn  only present in the spinal cord region of the thoracic and lumbar  houses cell bodies of the sympathetic nerve fibers Damage to the cell body of the somatic neurons in the ventral horns  Anytrophic Lateral sclerosis (Lov Gehrig’s disease) Hence, in ALS, the patient loses the ability to walk, speak, swallow, breathe breathing lost because the diaphragm (a skeletal muscle) is paralyzed Slide 59
  • Slide 62  64
  • PNS slideshow next
  • Cns bss

    1. 1. The Central Nervous System Brain – superiorly Spinal Cord - inferiorly
    2. 2. Figure 12.3
    3. 3. 4 Protective Structures of the Brain <ul><li>Cranium – bony helmet composed of the 8 cranial bones – frontal, parietal(paired), temporal(paired), occipital, sphenoid and the ethmoid bones </li></ul><ul><li>Meninges = 3 connective membranes surrounding the brain: </li></ul><ul><ul><li>Dura mater – outermost meninx; double-layered – outer periosteal layer ining the internal surface of the cranium and the inner meningeal layer separated from the underlying arachnoid mater by the SUDURAL space </li></ul></ul><ul><ul><li>Arachnoid mater – middle meninx separated from the underlying pia mater by the SUBARACHNOID space. Weblike extensions from the archnoid mater to the subarachnoid space gives this meninx its name ( Arachnida = spider family) </li></ul></ul><ul><ul><li>The suabarchnoid space contains CSF </li></ul></ul><ul><ul><li>Pia mater – innermost meninx that clings to the surface of the brain </li></ul></ul><ul><li>Cerebrospinal fluid ( CSF ) – filtered from blood; located in the ventricles and also in the subarachnoid space hence, CSF is found inside and outside of the brain acting as a “liquid” cushion; provides buoyancy to the brain; provides nutrients; removes metabolic wastes </li></ul><ul><li>Blood-Brain barrier – a selective barrier that prevents harmful substance in blood from crossing to the brain. </li></ul>
    4. 4. Figure 12.24
    5. 5. Figure 12.24b
    6. 6. Figure 12.5
    7. 7. Figure 12.26
    8. 8. Figure 12.27
    9. 9. Figure 12.12
    10. 10. The Brain <ul><li>Weight: 3.5Ib ( 1600 g) </li></ul><ul><li>4 major regions: </li></ul><ul><li>Cerebrum </li></ul><ul><li>Diencephalon </li></ul><ul><li>Brainstem </li></ul><ul><li>Cerebellum </li></ul>
    11. 11. The Cerebrum <ul><li>Superior region of the brain – accounts for 83% of total brain mass </li></ul><ul><li>Surface marked by elevated ridges called GYRI and shallow grooves called SULCI ; deeper grooves are called FISSURES </li></ul><ul><li>A median fissure called the LONGITUDINAL FISSURE divides the cerebrum into right and left cerebral hemispheres. </li></ul><ul><li>2 cerebral hemispheres are held together medially by the CORPUS CALLOSUM </li></ul><ul><li>Each cerebral hemisphere is divided into 5 lobes: </li></ul><ul><ul><li>_ Frontal lobe </li></ul></ul><ul><ul><li>Temporal lobe </li></ul></ul><ul><ul><li>Parietal lobe </li></ul></ul><ul><ul><li>Occipital lobe </li></ul></ul><ul><ul><li>Insula </li></ul></ul><ul><ul><li>The frontal, temporal, parietal and occipital lobes can be viewed externally and are named for the overlying cranial bones </li></ul></ul><ul><ul><li>The insula can not be viewed externally and located deep to the lateral sulcus, covered by the frontal, temporal and parietal lobes </li></ul></ul>
    12. 12. Figure 12.6c, d
    13. 13. Figure 12.6a, b
    14. 14. Figure 12.7
    15. 15. The Sulci in the cerebral hemispheres <ul><li>Central Sulcus – separates the frontal lobe from the parietal lobe. The gyrus in the frontal lobe located immediately in front of the central sulcus is called the PRECENTRAL GYRUS; the gyrus in the parietal lobe immediately behind the central sulcus is called the POSTCENTRAL GYRUS </li></ul><ul><li>Lateral Sulcus – separates the temporal lobe from the parietal and frontal lobes </li></ul><ul><li>Parieto-occipital Sulcus – separates the parietal lobe from the occipital lobe </li></ul>
    16. 16. Figure 12.6a
    17. 17. Figure 12.8a
    18. 18. 3 regions in each Cerebral hemisphere <ul><li>Cerebral Cortex – highly convoluted and 2-4 mm thick; accounts for 40% of total brain mass; composed of gray matter = cell bodies, dendrites; location of our conscious mind </li></ul><ul><li>Cerebral White Matter – deep to the cerebral cortex; composed of tracts with myelinated axons which have a “whitish” appearance </li></ul><ul><li>Basal Nuclei – islands of nuclei(clusters of neuron cell bodies) within the cerebral White Matter </li></ul>
    19. 19. Figure 12.11b
    20. 20. 3 Functional areas in the Cerebral Cortex <ul><li>Motor areas – control voluntary movements. </li></ul><ul><li>consist of the primary motor cortex, Premotor cortex, Broca’s area, fronta l eye field. All located in the frontal lobes </li></ul><ul><li>Sensory areas – for the conscious awareness of sensation ; consist of the Primary somatosensory cortex, Primary visual cortex, Primary auditory cortex, Primary olfactory cortex, Primary g ustatory cortex </li></ul><ul><li>Association areas – integrate and interpret sensory inputs from the sensory areas hence, each primary sensory area above has an associated area </li></ul>
    21. 21. 3 Functional areas in the Cerebral Cortex
    22. 22. The Cerebral Gray Cortex – Motor areas <ul><li>Consists of 4 functional areas: </li></ul><ul><li>Primary motor cortex – Controls the voluntary movements of skeletal muscles; located in the precentral gyrus of the frontal lobe in each cerebral hemisphere where the large neurons called PYRAMIDAL CELLS are located. The axons of the pyramidal cells bundle to form the PYRAMIDAL or CORTICOSPINAL TRACTS which cross over on the ventral side of the medulla oblongata ( DECUSSATION OF THE PYRAMIDS) – this explains the contralateral control of voluntary movements of skeletal muscles by the cerebral hemispheres: voluntary movements on the left side of the body are controlled by the right cerebral hemisphere and voluntary movements on the right side are controlled by the left hemisphere </li></ul><ul><li>Premotor Cortex – controls learned motor skills that are patterned or repetitious such as typing </li></ul><ul><li>Broca’s Area – controls skeletal muscles involved in speech production hence, referred to as the “motor speech area”. Present in only the frontal lobe in the left cerebral hemisphere. Arcuate fasciculate connects the Broca’s area to the Wernicke’s area located in the left temporal lobe to produce language </li></ul><ul><li>Frontal Eye Field – controls voluntary movements of the skeletal muscles that position the eyes </li></ul>
    23. 23. Decussation of the Pyramids
    24. 24. Cerebral White Matter
    25. 25. Cerebral White Matter <ul><li>Second region in the cerebrum deep to the cerebral cortex; consists of myelinated tracts </li></ul><ul><li>3 types of tracts based on direction : </li></ul><ul><li>Commissural tracts = Commissures – connect corresponding areas in the two cerebral hemispheres. Corpus callosum is a commissure that connects the right and left cerebral hemispheres. </li></ul><ul><li>Projection tracts – connect the cerebrum to lower brain areas and the spinal cord. Pyramidal or corticospinal tracts are projection tracts </li></ul><ul><li>Association tracts – connect areas within the same cerebral hemisphere. Arcuate fasciculate is an association tract </li></ul>
    26. 26. Basal Nuclei
    27. 27. Projection tracts
    28. 28. Basal Nuclei <ul><li>Islands of gray matter in the cerebral white matter </li></ul><ul><li>3 major Basal Nuclei: </li></ul><ul><li>Caudate nucleus </li></ul><ul><li>Putamen </li></ul><ul><li>Globus pallidus </li></ul><ul><ul><li>Putamen + globus pallidus = LENTIFORM NUCLEUS </li></ul></ul><ul><ul><li>Lentiform nucleus + caudate = CORPUS STRIATUM </li></ul></ul><ul><li>Basal nuclei are associated with nuclei in the brain stem and are involved in initiating and stopping movements; they inhibit unnecessary movements </li></ul>
    29. 29. Ventricles
    30. 30. Ventricles <ul><li>Cavities in the brain that contain CSF </li></ul><ul><li>Lateral ventricles – each cerebral hemisphere contains a lateral ventricle; the 2 lateral ventricles are connected by a median membrane called the septum pellucidum; 2 lateral ventricles are connected to the third ventricle below by a channel called the interventricular foramen. </li></ul><ul><li>Third ventricle – located in the diencephalon; connected to the fourth ventricle below via the cerebral aqueduct </li></ul><ul><li>Fourth ventricle – located in the brain stem </li></ul>
    31. 31. Diencephalon
    32. 32. Diencephalon <ul><li>Consists of 3 paired structures: </li></ul><ul><li>Thalamus – the relay station for sensory inputs to the cerebral cortex hence, the thalamus is referred to as the “Gateway to the cerebral cortex”. Visual relay center in the thalamus is the lateral geniculate nucleus (LGN); auditory relay center is the medial geniculate nucleus (MGN ). Thalamus contains the third ventricle </li></ul><ul><li>Hypothalamus – located below the thalamus; controls </li></ul><ul><ul><li>Activities of the Autonomic Nervous System </li></ul></ul><ul><ul><li>Emotional response </li></ul></ul><ul><ul><li>Core body temperature as it contains the body’s thermostat </li></ul></ul><ul><ul><li>Food intake as it contains the satiety center </li></ul></ul><ul><ul><li>Water intake as it contains the thirst center </li></ul></ul><ul><ul><li>Sleep-wake cycles </li></ul></ul><ul><ul><li>Endocrine function as it produces 9 hormones </li></ul></ul><ul><li>Epithalamus – forms the roof of the third ventricle; contains the pineal gland, an endocrine gland that secretes the hormone, melatonin, the sleep-inducing chemical. </li></ul>
    33. 33. Brain Stem
    34. 34. Figure 12.15c
    35. 35. Table 12.1.1
    36. 36. Figure 12.14
    37. 37. Brain Stem <ul><li>Composed of an outer white matter and an inner gray matter </li></ul><ul><li>Consists of 3 regions: </li></ul><ul><li>Midbrain – contains the cerebral aqueduct; corpora quadrigemina = 4 nulei called colliculi – 2 superior colliculi act as the visual reflex center and the 2 inferior colliclui act as auditory reflex center; CN III, IV issue from nuclei in the midbrain. </li></ul><ul><li>Midbrain contains 2 pigmented nuclei – red nuclei and the substantia nigra </li></ul><ul><li>Red nuclei regulate limb flexion; substantia nigra contain dopamine-releasing neurons (=dopaminergic hormone) which project and modulate activities of the basal nuclei – degeneration of these dopaminergic neurons to the basal nulei causes Parkinson’s disease </li></ul><ul><li>Pons – located between the midbrain and the medulla oblongata; 3 pairs of cranial nerves issue from nuclei in the pons ( CN V, VI, VII); connect the motor cortex and the cerebellum hence, involved in the control of skeletal muscle movements. Contains respiratory centers </li></ul><ul><li>Medulla oblongata – most inferior region that blends in with the spinal cord at the level of the foramen magnum. Decussation of the pyramids on its ventral surface,; CN VII, VIII, IX, X, XI, XII issue from the medulla. </li></ul><ul><li>Contains autonomic reflex centers: Cardiovascular center, respiratory center, emetic center, swallowing center, coughing reflex center </li></ul>
    38. 38. Cranial Nerves III - XII
    39. 39. Figure 12.15b
    40. 40. 2 pigmented nuclei in the Midbrain
    41. 41. CEREBELLUM
    42. 42. The Arbor Vitae
    43. 43. Cerebellum <ul><li>Composed of outer gray matter and an inner white matter; the cerebellar inner white matter resembles a branching tree referred to as the “Arbor Vitae”. </li></ul><ul><li>Cerebellum consists of two cerebellar hemispheres connected medially by the VERMIS </li></ul><ul><li>Each cerebellar hemisphere is composed of three lobes: </li></ul><ul><ul><li>Anterior lobe </li></ul></ul><ul><ul><li>Posterior lobe </li></ul></ul><ul><ul><li>Flocculonodular lobe – cannot be viewed on the external surface of the cerebellum </li></ul></ul><ul><li>Function: For posture, balance(equilibrium) and smooth, coordinated skeletal muscle movements </li></ul><ul><li>Cerebellar function is affected by alcohol intoxication hence tandem gait which indicates proper balance, is lost </li></ul>
    44. 44. Table 12.1.2
    45. 45. The Spinal Cord
    46. 46. The Spinal Cord
    47. 47. The Spinal Cord <ul><li>Second part of the CNS inferior to the brain </li></ul><ul><li>Extends from the foramen magnum to the level of the first lumbar vertebra where it terminates in a tapering cone-shaped structure called CONUS MEDULLARIS </li></ul><ul><li>Contains two enlargements – cervical and lumbar enlargements </li></ul><ul><li>The length of the spinal cord = 42cm(17in) long </li></ul><ul><li>Composed of an outer white matter and an inner gray matter which appears like the letter “H” or a butterfly in cross-section; the CENTRAL CANAL passes through the center of the gray matter </li></ul><ul><li>31 pairs of spinal nerves exit the spinal cord. </li></ul><ul><li>Collection of nerve roots inferior to the conus medullaris is called the CAUDA EQUINA </li></ul>
    48. 48. 3 Protective structures of the Spinal Cord
    49. 49. 3 protective structures of the Spinal Cord <ul><li>Vertebral column – forms a bony encasement </li></ul><ul><li>Spinal Meninges – 3 types: </li></ul><ul><li>Spinal dura mater = spinal dural sheath –outer meninx; single-layered and does not line the internal surface of the vertebrae; space between the vertebral column and the spinal dural sheath is called the EPIDURAL SPACE filled with fat and veins; anesthesia to block pain is injected into the epidural space </li></ul><ul><li>Arachnoid mater – middle meninx; separated from the spinal dural sheath by the subdural space; separated from the pia mater by the subarachnoid space which contains CSF </li></ul><ul><li>Pia mate r – inner meninx; forms the DENTICULATE LIGAMENTS which secure the spinal cord laterally to spinal dural sheath; covers the FILUM TERMINALE - a fibrous extension of the conus medullaris - which anchors the spinal cord to the coccyx. </li></ul><ul><li>Cerebrospinal fluid(CSF) – located in the central canal and the subarachnoid space acting as a liquid cushion, provides nutrients and removes metabolic wastes </li></ul>
    50. 50. Figure 12.29c
    51. 51. Figure 12.29d
    52. 52. Cervical and Lumbar enlargements <ul><li>Cervical enlargement – located in the cervical region; spinal cervical nerves from the cervical enlargement control voluntary movements of the upper limbs. </li></ul><ul><li>Transection of the spinal cord in/above the cervical enlargement leads to QUADRIPLEGIA – loss of voluntary movements of all four limbs. </li></ul><ul><li>Lumbar enlargement – located around lumbar region; nerves from the lumbar enlargement control voluntary movements of the lower limbs. </li></ul><ul><li>Transection of the spinal cord below the cervical enlargement but above the lumbar enlargement leads to PARAPLEGIA – loss of voluntary movements of the lower limbs. </li></ul>
    53. 53. Lumbar Tap
    54. 54. Lumbar Tap <ul><li>CSF is taken from the subarachnoid space for analysis, if meningitis is suspected. </li></ul><ul><li>The lumbar tap is performed around the fifth lumbar vertebra, definitely below the spinal cord to avoid potential damage to the spinal cord. </li></ul>
    55. 55. Gray Matter and White Matter
    56. 56. The Gray Matter and the White Matter of the Spinal Cord <ul><li>The inner GRAY MATTER is “H”-shaped or butterfly-shaped; the two masses of gray matter are connected by the gray commissure, which surrounds the central canal. </li></ul><ul><li>Consists of the DORSAL HORNS, VENTRAL HORNS and the LATERAL HORNS </li></ul><ul><li>Dorsal Horns – consist of interneurons </li></ul><ul><li>Ventral Horns – house the cell bodies of somatic motor neurons </li></ul><ul><li>Lateral Horns – house sympathetic neurons that innervate organs </li></ul><ul><li>The outer WHITE MATTER – composed of mostly myelinated axons that allow communication between different parts of the spinal cord and between the spinal cord and the brain </li></ul><ul><li>3 types of fiber tracts: </li></ul><ul><ul><li>Ascending tracts – run vertically; sensory inputs from sensory receptors to the spinal cord and then to the brain; the axons decussate and the left cerebral hemisphere receives sensory inputs from the right side of the body and vice versa </li></ul></ul><ul><ul><li>Descending tracts – run vertically; motor output coming down from the brain or within the cord to lower levels </li></ul></ul><ul><ul><li>Transverse tracts = commissural tracts – run horizontally from one side of the spinal cord to the other </li></ul></ul>
    57. 57. Figure 12.32
    58. 58. Ascending Tracts - Sensory inputs
    59. 59. Table 12.2.2
    60. 60. Descending Tracts – Motor output
    61. 61. Table 12.3.1
    62. 62. Terminology <ul><li>Paresthesia – sensory loss </li></ul><ul><li>Paralysis – loss of motor function </li></ul><ul><li>Flaccid paralysis – indicates damage to the ventral horns in the spinal cord </li></ul><ul><li>Spastic paralysis – damage to the precentral gyri which results in hemiplegia , paralysis on one side of the body; damage to the left precentral gyrus results in right side paralysis and vice versa </li></ul>
    63. 63. Amyotrophic Lateral Sclerosis (ALS) = Lou Gehrig’s disease <ul><li>Involves progressive destruction of ventral horn motor neurons and the pyramidal tracts – loss of skeletal muscle movements = loses the ability to walk or move the arms( quadriplegia), to speak, to swallow and to breathe </li></ul><ul><li>(due to paralysis of the diaphragm) </li></ul>
    64. 64. Lumbar Myelomeningocele – Spina Bifida cystica – incomplete formation of the vertebral arches

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