Page. Ch 11 A CNS. This set. Major Landmarks: Brain size is proportional to body size only and can be divided into three major portions;

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1 1 BIO 211: ANATOMY & PHYSIOLOGY I 1 Ch 11 A CNS This set Ch 11 B Notes: PNS Somatic ANS Ch 11 C ANS Dr. Dr. Lawrence G. G. Altman Some illustrations are courtesy of McGraw-Hill. Some illustrations are courtesy of McGraw-Hill. CHAPTER 11 NERVOUS SYSTEM 2 DIVISIONS General Features of the Central Nervous System Major Landmarks: Brain size is proportional to body size only and can be divided into three major portions; 1. Cerebrum (largest portion: 83% of brain volume) 2. Cerebellum 3. Brainstem 1. Cerebrum consists of 2 cerebral hemispheres. divided each marked by gyri and sulci. into multiple lobes. sulcus: shallow groove fissure: deep groove gyrus: convolutions (ridges) The longitudinal fissure separates the left and right hemispheres, although they remain connected through the corpus callosum. 2

2 Cerebrum General Features of the Central Nervous System Sagittal section b a d Note: Much of the hollow space throughout the entire CNS is filled with cerebrospinal fluid (CSF). c 3 e 2. Cerebellum lies inferior and posterior to the cerebrum; more delicate surface markings. 4 Recall position on the ship brain: arbor vitae etc.?? 3. Brainstem at Base of Brain 2 a. thalamus b. hypothalamus c. midbrain d. pons e. medulla oblongata

3 3 General Features of the Central Nervous System Gray Matter vs. White Matter: Gray matter- consisting of non-myelinated SOMA and DENDRITES White matter- myelinated NERVE FIBERS 5 The gray matter forms an outer cortex in the brain, but as an inner core in the spinal cord. white white gray gray SC Meninges, CSF, Ventricles and Blood Supply A. Meninges 1. The meninges are 3 protective fibrous coverings that separate the brain and spinal cord from the skull and vertebrae The outermost meninx, the dura mater, consists of an periosteal layer and an inner meningeal layer. Within the vertebral canal, the meningeal layer forms a dural sheath. Between the sheath and surrounding bone lies the epidural space. 3. The second meninx, the arachnoid matter adheres to the dura and sends spiderlike extensions out to the # 3 pia mater. The pia mater is highly vascular; closely follows the contour of the brain

4 4 Meninges, CSF, Ventricles and Blood Supply 7 4. Dura and arachnoid are separated by a very small subdural space. Arachnoid and pia mater are separated by the subarachnoid space. scalp Bone Gray matter White matter Dura mater Subdural space (small) Arachnoid (white) Subarachnoid space Pia mater (red) CEREBRUM CEREBRUM Meninges, CSF, Ventricles and Blood Supply B. Cerebrospinal Fluid (CSF) 8 1. Cerebrospinal fluid (CSF) is a clear, colorless liquid that functions to lend buoyancy, for protection, in waste removal, and in providing a stable chemical environment. 2. Cerebrospinal fluid is produced by the choroid plexus within each ventricle (4 total), which consists of capillaries covered by simple cuboidal epithelium. 3. Tight junctions within the choroid plexus form a blood-csf barrier that protects the brain.

5 5 Meninges, CSF, Ventricles and Blood Supply 9 More on Ventricles. Meninges, CSF, Ventricles and Blood Supply C. Ventricles and CSF Circulation 1. The brain has four (4) CSF-filled ventricles. Each cerebral hemisphere houses a large lateral ventricle (total = 2) that communicates with a third ventricle through an interventricular foramen. 10 Recall: Ependymal cells Text typo: Inter- Cerebral aqueduct connects the third ventricle with the fourth ventricle.

6 6 Meninges, CSF, Ventricles and Blood Supply 11 Inter Review the previous plate to clarify orientation! Meninges, CSF, Ventricles and Blood Supply C. Ventricles and CSF Circulation 2. Cerebrospinal fluid (CSF) originates in the choroid plexuses of each ventricle, circulates throughout the ventricles, and makes its way into the central canal of the spinal cord. It exits the fourth ventricle through two apertures (openings) and enters the subarachnoid space Hydrocephalus ("water on the brain") results from blockage of the route of CSF and its absorption.

7 7 Meninges, CSF, Ventricles and Blood Supply 13 Hydrocephalus Meninges, CSF, Ventricles and Blood Supply D. Blood Supply and the Blood-Brain Barrier 1. The brain is very metabolically active, and has a high demand for oxygen and glucose. Stopping the blood supply to the brain for as little as 4 minutes can cause irreversible damage The CNS is protected by a blood-brain barrier that regulates substances entering the brain. Tight junctions within capillaries and astrocytes comprise this barrier. 3. The blood-brain barrier is absent in areas of the brain (called circumventricular organs) that monitor blood glucose, ph, salinity etc.

8 8 The Spinal Cord A. Spinal Cord: Functions Locomotion, conduction and reflex activity control 15 B. Spinal Cord: Gross Anatomy. 1. The spinal cord begins at the foramen magnum and ends at the first lumbar vertebra. Cervical, thoracic, lumbar, and sacral regions pairs of spinal nerves 3. cervical & lumbar enlargements, nerves ---> appendages arise. 4. cord tapers to a point at the conus medullaris 5. Cauda equina: nerve bundle exits the bottom of the spinal cord Book Typo: should be Cauda The Spinal Cord 16

9 9. The Spinal Cord C. Spinal Cord: Cross - Section 1. The spinal cord has an anterior median fissure and a posterior median sulcus. 2. Gray Matter: region of CNS where fibers generally lack myelin, thereby appearing gray. a. The cord consists of a central area of gray matter divided into regions called horns 2 dorsal or "posterior horns," and 2 ventral or "anterior horns" The right and left halves are connected by the gray commissure; in the center is the central canal. b. Sensory fibers enter the dorsal horn, synapse with an interneuron and somatic motor neurons exit via the ventral root of the spinal nerve. 17 The Spinal Cord Sensory fibers IN 18 (dorsal) (ventral) Somatic motor neurons OUT

10 10 The Spinal Cord KEEPING IT ALL IN PERSPECTIVE 1 19 The Spinal Cord 20 KEEPING IT ALL IN PERSPECTIVE 2

11 11 21 The Spinal Cord C. Spinal Cord: Cross - Section 3. White Matter White matter consists of bundles of myelinated axons that run up and down the SC, to and from the brain. White matter is arranged into: dorsal, lateral, and ventral columns. 22 D. Spinal Cord: SPINAL TRACTS 1. Ascending Tracts carry SENSORY information up the spinal cord; 2. Descending Tracts carry MOTOR information down the spinal cord; Many fibers exhibit decussation: Crossover---> left/right; right/left

12 12 23 Remember: These tracts are axons; The orange shading in the figures is misleading! Tracts are WHITE matter. Students are not responsible for naming the individual tracts at this time. The Spinal Cord 24

13 13 The Hindbrain and Midbrain 25 A. Hindbrain: Medulla Oblongota part of the Brain stem Parts of the medulla oblongota control: coughing, sneezing, hiccuping, sweating, vomiting etc. In addition, the cardiac, vasomotor, and respiratory centers are located here. B. Hindbrain: Pons (part of the Brain stem) Cerebellum 1. The gray matter of the pons contains nuclei (gray matter masses) concerned with sleep, posture, respiration, swallowing, and bladder control. Signals from the cerebrum to the cerebellum pass through the pons. Pons MO The Hindbrain and Midbrain 26 B. Hindbrain: Pons (part of the Brain stem) Cerebellum 2. The cerebellum is the largest part of the hindbrain. The right and left cerebellar hemispheres connect via the by vermis. Three paired cerebellar peduncles (nerve tracts) connect the cerebellum to the brainstem. modulates and coordinates voluntary movement of the limbs, maintains muscle tone and posture, coordinated eye movements, and helps in learning motor skills.

14 14 The Hindbrain and Midbrain 27 C. Midbrain: Mesencephalon (part of the Brain stem) Tectum 1. Mesencephalon connects the hindbrain to the forebrain. 2. Tectum consists of 4 nuclei called the corpora quadrigemina:. these nuclei function in visual attention, tracking objects, and visual reflexes. Light Green (artists s interpretation) in figure D. Reticular Formation a group of 100 nuclei scattered throughout the medulla, midbrain, and pons that function in somatic motor control, autonomic control, arousal, and pain modulation. Thalamus, Hypothalamus and Epithalamus 28 A. Thalamus (part of the Brain stem) 1. The thalamus consists of two oval masses of gray matter, underneath each cerebral hemisphere, and a narrow intermediate mass near the third ventricle. 2. The thalamus is the "gateway to the cerebral cortex"; nearly all information heading to the cerebrum passes through the thalamus, except for sensory input from smell. B. Hypothalamus (Brain stem) major control center for ANS and endocrine; also, homeostasis. Nuclei: (gray covered by white) regulate food-water intake, thermoregulation, cardiovascular regulation, sleep/waking, emotions

15 15 Thalamus, Hypothalamus and Epithalamus C. Epithalamus Cone - shaped gland, best known for synthesis of melatonin from serotinin. Role in light - sensitive Circadian rhythms. No need to know the location; if curious, see your text. 29 The Cerebrum A. Cerebral White 1. The white matter of the cerebrum does not make decisions, but comprises most of the cerebral volume. 2. This area houses projection tracts, commissural tracts, and association tracts. (no need to know) B. Cerebral Cortex: Gross Anatomy 1. The cerebral cortex (40% of brain mass) is a layer of gray matter, (2-3 mm thick), covering the cerebral hemispheres lobe regions: frontal, parietal, occipital, and temporal. The Cerebrum C. Basal Nuclei 1. The basal nuclei are masses of gray matter buried deep in the cerebral hemispheres. atypical? why?? 2. involved in motor control and the thought process. 30 D. Limbic System 1. is a loop of cortical structures surrounding the corpus callosum and thalamus. It is the oldest part of the cerebral cortex. 2. Many important facets of an individual's personality depend on an intact limbic system. 3. important for emotions, such as fear, anger, love, and others.

16 16 Cerebral Cortex: Functions A. Brain Waves (see Clinical Application, Hole) 1. Brain waves are rhythmic voltage changes resulting from synchronized postsynaptic potentials in the cerebral cortex. 2. They can be recorded as an electroencephalogram (EEG). An EEG is often used as a legal criterion for death. B. Sleep 1. Sleep is a temporary state of unconsciousness (can be aroused) Coma: person cannot be aroused. 2. Control: hypothalamus & brain stem 3. 4 stages: 4th- deep (slow wave sleep) 4. Several times per night, the sleeper "backtracks" to stage 1 and enters rapid eye movement (REM) sleep. It is also called paradoxical sleep because of the difficulty with which a sleeper can be aroused. Most dreams occur during this period. As sleep continues, periods of REM sleep get longer. Not required to know different types

17 17 Cerebral Cortex: Functions 33 C. Motor Control Voluntary muscle contractions are initiated in the motor association (premotor) area of the frontal lobes. The impulse is then sent to the precentral gyrus (primary motor area). D. Somatic Control The postcentral gyrus functions as the primary sensory area or somesthetic. Here neurons receive sensory information. E. Special Senses Input from the special senses does not enter the postcentral gyrus but instead travels to other specialized areas of the brain. Cerebral Cortex: Functions 34 F. Association Areas Various association areas are located in the cerebral cortex including the somatosensory association area, the visual association area, the auditory association area, and the frontal association area. G. Cerebral Lateralization the assignment of different tasks to different hemispheres, and is correlated with handedness. Most Americans are right-handed (left hemisphere). Males show more lateralization than females. H. Language Language includes several abilities and is assigned to different regions of the cerebral cortex.

18 18 Cerebral Cortex: Functions I. Memory Memory is the storage and retrieval of acquired information or skills. Memory is estatblished in phases. 1. Short-term memory lasts up to a few hours and is limited to 7-12 bits of information. 2. Long-term memory last longer, and can store an unlimited amount of information. Images of the Brain 1. Positron emission tomography (PET) employs radioactive oxygen to pinpoint areas of the brain with the greatest activity (greatest blood flow). 2. Magnetic resonance imaging (MRI) depends on the fact that neurons employ anaerobic fermentation during heightened activity. Changes in brain circulation can be detected using MRI A link to the Cranial Nerves may be found on the Bio 211 Lecture page at You are responsible for their numbers, names and functions as listed in the link.

19 19 Review 37 Review 38

20 20 Review 39 Last Plate Review 40