Functional Anatomy PDF

Assafa College Department of Physiology NERUROPHYSIOLOGY Dr. Rayan Khalid, MBBS, M.Sc, MD Lecture No (1)   Course contents Applied Anatomy Basic anatomical & physiological concepts Sensory system Pain R...

Assafa College Department of Physiology NERUROPHYSIOLOGY Dr. Rayan Khalid, MBBS, M.Sc, MD Lecture No (1)   Course contents Applied Anatomy Basic anatomical & physiological concepts Sensory system Pain Reflex & motor system Higher Functions ( 1& 2) Limbic system Sleep & EEG Special senses  REFERENCES Ganong Review of Medical Physiology. The core of medical physiology. Guyton and Hall Textbook of Medical Physiology DIVISIONS OF NERVOUS SYSTEM  Some General Terminology for CNS o Folds found in the cerebrum and the cerebellum Gyri = raised areas Sulci = fissures between the gyri o Gray matter = thin myelin; mostly cell bodies dendrites & synapses: Outer layer of brain = cortex Inner layer of spinal cord o Nuclei: small areas of gray matter deeper inside the brain. o White matter = thick insulation; mostly axons o Nerve tracts = bundles of axons that interconnect various parts of the brain: Inner layers of brain. Outer layer of spinal cord.  BRAIN One of the largest organs in body: men: 1,600 g , women: 1,450g Brain size is proportional to body size not intelligence!!!! One of most metabolically active organs in body (15% of blood, consumes 20% of oxygen need at rest (more when mentally active). 1-2 min interruption of blood flow may impair brain cells > 4 min w/o oxygen > permanent damage Brain must get continuous supply of glucose Decrease in glucose: Dizziness, Convulsions, unconsciousness Brain’s storage capacity - based in number of neurons and number of synapses- is 1 Million Gigabytes (impressive !!!) Brain consist of Brain stem (medulla, pons, midbrain): basic bodily functions = vegetative functions Diencephalon(thalamus & hypothalamus) : moods, memory, manages internal environment Cerebellum: coordinating movement and balance Cerebrum: thought, creativity, communication  BRAIN STEM Medulla: Contains important nuclei control several vital functions: cardiac center, vasomotor center, respiratory center. Contains other centers: speech, swallowing, vomiting, coughing sneezing, hiccupping. Most tracts cross over as they pass through the medulla  Pons: Connecting spinal cord with brain and parts of brain with each other contains respiratory centers and nuclei affect sleep and bladder control. Midbrain control centers for some visual & auditory reflexes contains substantia nigra nucleus: suppresses unwanted muscle contractions ❖Reticular Formation Diffuse system of interconnecting fibers extending through several areas of brain including brain stem Comprises a large portion of entire brainstem ,extends into spinal cord and diencephalon. Functions of RAS: Maintains sleep and consciousness Helps control muscle tone, balance and posture during body movements Filters flood of sensory input (habituation)  DIENCEPHALON Thalamus: Main relay station for sensory impulses that reach cerebral cortex, eg. taste, touch, heat, cold, pain, etc Hypothalamus: Controls and integrates many autonomic activities Regulates body temperature Regulates food and water intake Epithalamus: Includes pineal gland (an endocrine gland that controls cyclic activities) Limbic System : The emotional brain CEREBELLUM Below and posterior to cerebrum only other part of brain , highly folded. Consists of 2 hemispheres. grey matter outside white matter inside. Functions of Cerebellum: helps to coordinate voluntary muscles Diseases of cerebellum produce Ataxia CEREBRUM 2 cerebral hemispheres joined by nerve tracts (corpus callosum). Surface: gyri and sulci folding allows greater area of cortex in smaller space Each hemisphere: Outer gray matter ( cerebral cortex) “functional part” of the cerebrum. Inner white matter (tracts):connects various functional parts of the cerebrum. Nuclei (gray matter in the interior of brain) eg. basal nuclei (basal ganglia).  Function of Cerebral Cortex: Responsible of most “human” traits: conscious mind, abstract thought, memory, awareness. Contains some more basic functional areas: Motor areas: that control voluntary motor functions Sensory areas provide conscious awareness of sensations Association areas Each hemisphere is mainly concerned with sensory and motor functions of the opposite side of the Body eg. left hemisphere controls right hand.  Each hemisphere takes on complementary functions: Left Hemisphere: Language: processes many aspects of language. More involved in analytical skills eg, math, logic Right Hemisphere: Nonverbal communication: reading facial expressions, recognizing faces. Mainly concerned with visuospatial tasks the “artistic” duties of the brain  Hemispheric Dominance: 90% of population : left hemisphere are dominant more verbal, analytical are right handed. 7% of population : right hemisphere are dominant visuospatial tasks are left handed , more likely to be males. 3% of population: functions are shared equally.  Lobes of the cerebrum: divided by fissures Frontal Parietal Occipital Temporal  FRONTAL LOBE prefrontal: Elaboration of thought, intelligence, Motivation, Personality, abstract ideas, Judgement, planning “civilizing behaviors” Damage: Wide mood swings, loss of attentiveness, careless about personal appearances. Olfactory Cortex : Small area just above orbits, perception of odors, smells. Motor Cortex Directs conscious control of muscle contraction, coordinates groups of muscles. Damaged cause paralysis or trouble directing learned muscular coordination eg typing, tying shoes.  PARIETAL LOBE Sensory Cortex: At the front of the parietal lobe. Receives information from muscle, tendon and joint sensations, and touch. Gustatory Cortex Conscious awareness of taste stimuli TEMPORAL LOBE Auditory Cortex Interprets sounds: pitch, rhythm, loudness (hearing) Area for balance and equilibrium Awareness of position and orientation.  OCCIPITAL LOBE The entire lobe is devoted to visual processing image (visual cortex) Based on nerve impulses received from the eyes, image is analyzed in terms of its elementary features: Orientation Color Texture Depth, presence of movement  SPINAL CORD Located in the spinal canal of the vertebral column 17 – 18 inches long Extends from foramen magnum to lower border of 1st lumbar vertebrae Subdivided into cervical, thoracic, lumbar, sacral regions Spinal cord terminates in a bundle of nerves = cauda equina White matter: myelinated, divided into columns and tracts. Numerous tracts can be identified in the spinal cord  ASCENDING TRACTS OF SPINAL CORD o Carry the impulses of various sensations to the brain. three groups of neurons, which are: First order neurons: from the receptors to sensory neurons in the posterior nerve root ganglion. Second order neurons: form the ascending tracts of spinal cord to different subcortical areas such as thalamus. Third order neurons: from subcortical areas to cerebral cortex.  PROTECTION OF CNS ❑Both brain and spinal cord are heavily protected: Bone: skull and vertebral column Adipose cushion around spinal cord Meninges: tough flexible covering Liquid cushion: cerebrospinal fluid CSF mainly in: brain ventricles and ducts, central canal of spinal cord, in subarachnoid space of the meninges space between arachnoid layer and pia mater  MENINGES Dura mater :strong fibrous connective tissue, outer layer in skull is periosteum of cranial bones Arachnoid layer: delicate cobwebby layer subarachnoid space = between arachnoid layer and pia mater Pia mater: Transparent , adheres to outer surface of brain and cord, contains blood vessels o 3 extensions of the meninges form partitions between various parts of the brain: Falx cerebri: largest partition, between cerebral hemispheres Falx cerebelli: separates cerebellar hemispheres. Tentorium cerebelli :separates cerebrum from cerebellum. ❑Meninges continues around spinal cord and extends beyond the end of the spinal cord > safer site for lumbar puncture to get CSF ❑Meningitis : inflammation of arachnoid, pia and CSF usually; may lead to encephalitis ❑Encephalitis: inflammation of brain tissue itself  CEREBRO SPINAL FLUID Brain actually “floats” in CSF (140 ml) Ventricles are fluid filled cavities inside brain: 1st & 2nd inside cerebral hemispheres (lateral ventricles) 3rd small slit inside diencephalon (mainly thalamus) 4th diamond shaped expansion of central spinal canal in brainstem Choroid plexuses are capillary beds found in each of the 4 ventricles of the brain where they secrete CSF.  PERIPHERAL NERVOUS SYSTEM PNS = nerves, ganglia & nerve plexuses sensory and motor neurons 10% of all neurons in body are in PNS PNS is our link to the outside world Some Terminology: CNS : bundle of axon : track , cell bodies : nuclei PNS: bundle of axon : nerve , cell bodies : ganglia  PNS consists of 43 pairs of nerves branching from the brain & spinal cord: 12 pairs of cranial nerves 31 pairs of spinal nerves A) Cranial Nerves Most cranial nerves originate from the brainstem which contains most of the automatic (vegetative) functions of the body Some cranial nerves are sensory nerves, some are motor and some are mixed nerves ❑Sensory cranial nerves ❑Mixed cranial nerves I. Olfactory [sense of smell] IX. Glossopharyngeal II. Optic [sense of sight] [sense of taste, VIII. Vestibulocochlear swallowing] [senses of hearing and XII. Hypoglossal [tongue] balance] V. Trigeminal [cutaneous senses of head and face, chewing muscles] ❑Motor cranial nerves VII. Facial [sense of taste, III. Oculomotor facial expression] IV. Trochlear [eye X. Vagus [sensory and movements] motor to larynx, heart, VI. Abducens lungs, digestive system] XI. Accessory [shoulder and head]  B) Spinal Nerves 31 pairs all are mixed nerves all but 1st pass through intervertebral foramina They are named and numbered according to the level of the vertebral column from which they arise:8 cervical & 12 thoracic& 5 lumbar & 5 sacral& 1 coccygeal  Each spinal nerve is attached to spinal cord by two roots: Dorsal (posterior) root: sensory neurons and a ganglion Ventral (anterior) root: motor neurons The two roots joint to form a mixed, spinal nerve. DERMATOMES Sensory neurons of each spinal nerve innervate the skin and skeletal muscles in the roughly same order in which they emerge from the spinal cord, Segmental arrangement of spinal nerves This is clinically useful since physicians can determine the site of spinal damage by simple pinprick exam