Neurology Notes PDF

 At the end of this lecture the student would be able to:  Recognize the types of nervous system.  Know the parts of C.N.S  Know the parts of P.N.S  Identify the areas of cerebral cortex.  Describe the motor system.  Recognize the difference between UMNL & LMNL. ...

 At the end of this lecture the student would be able to:  Recognize the types of nervous system.  Know the parts of C.N.S  Know the parts of P.N.S  Identify the areas of cerebral cortex.  Describe the motor system.  Recognize the difference between UMNL & LMNL.  Identify the stretch reflex arc. The nervous system is a complex collection of nerves and specialized cells known as neurons that transmit signals between different parts of the body. It is essentially the body’s electrical wiring. *(1)Structurally, the nervous system has 2 components: the (CNS) central nervous system and the(PNS) peripheral nervous system. CNS PNS 31 SPINAL 12 Pairs Pairs BRAIN Cranial CORD spinal n. n. CNS I- Intracranial Part II- Spinal Part B- Brain A- Spinal B- Cauda A- Cerebrum C- Cerebellum Stem Cord Equina 1) ( the brain is protected in the skull and the spinal cord is protected in the vertebral canal). 2) The C.N.S. is the part of the N.S. which. Pia mater is covered by 3 coverings called meninges. Arachnoid mater dura mater. *(2)Functionally, the nervous system has 2 main subdivisions: the somatic, or voluntary, component; and the autonomic, or involuntary, component. The somatic system : consists of nerves that connect the brain and spinal cord with muscles and sensory receptors in the skin. The autonomic nervous system (sympathatic & parasymathatic): regulates certain body processes, such as blood pressure and the rate of breathing, that work without conscious effort.  Figure 16.3a Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings *The sympathetic system is activated during a “fight or flight” situation in which great mental stress or physical danger is encountered Neurotransmitters as noradrenaline & adrenaline are released, which increases heart rate and blood flow in certain areas like muscles, *Parasympathetic nervous system] Primarily using the neurotransmitter acetylcholine (ACh) as a mediator, the parasympathetic system allows the body to function in a “rest and digest” state. Consequently, when the parasympathetic system dominates the body, there are increases in salivation and activities in digestion, while heart rate and other sympathetic response decrease The autonomic nervous system  As The peripheral nervous system consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves. Some of those nerve pairs are: 1-Exclusively sensory cells, such as cells that detect information like smell and vision. 2-Others are exclusively motor cells, like the eyeballs and hearing. 3-Also, there are nerve pairs that have both sensory and motor cells, such as those involved in taste and some aspects of swallowing the nervous system is formed of One axon (called a “nerve “units” called “neurons” fiber”) one or many dendrites What is neuron? A neuron is a nerve cell and … its processes. Transmission of nerve impulses A nerve impulse is essentially an electrical stimulus that travels over the cell's membrane. It passes through the axons and dendrites of the neurons. It travels via the dendrites from the skin and then reaches the cell body, axon, axon terminals and the Synapse of the neuron. The Synapse is the junction between two neurons where the impulse moves from one to the other. As the synapse neurotransmitters are present THE NEURONE Cerebral Cortex - The outermost layer of gray matter making up the superficial aspect of the cerebrum. Cerebral Cortex Cerebral Cortex http://www.bioon.com/book/biology/whole/image/1/1-6.tif.jpg  Cerebral Features: Gyri – Elevated ridges “winding” around the brain. Sulci – Small grooves dividing the gyri – Central Sulcus – Divides the Frontal Lobe from the Parietal Lobe Fissures – Deep grooves, generally dividing large regions/lobes of the brain – Longitudinal Fissure – Divides the two Cerebral Hemispheres – Transverse Fissure – Separates the Cerebrum from the Cerebellum – Sylvian/Lateral Fissure – Divides the Temporal Lobe from the Frontal and Parietal Lobes  Gyri (ridge) Sulci (groove) Fissure (deep groove) http://williamcalvin.com/BrainForAllSeasons/img/bonoboLH-humanLH-viaTWD.gif Specific Sulci/Fissures: Central Sulcus Longitudinal Fissure Sylvian/Lateral Fissure Transverse Fissure http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg http://www.dalbsoutss.eq.edu.au/Sheepbrains_Me/human_brain.gif  Lobes of the Brain (4) Frontal Parietal Occipital Temporal http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg * Note: Occasionally, the Insula is considered the fifth lobe. It is located deep to the Temporal Lobe.  Frontal Lobe 1) Motor Area (area 4):. Function: initiation of voluntary motor activity of the opposite side of the body through the pyramidal (Δ) tract. In this area the body is represented upside down. Lesion: Contralateral paralysis 2)Premotor Area (area 6): Function: This area inhibits the muscle tone & the deep reflexes on the opposite side of the body. Lesion: contralateral hypertonia & exaggerated deep reflexes 3)Area of Voluntary Conjugate Eve Movements (area 8): Function: voluntary conjugate eye movement to the opposite side Lesion: paralysis of conjugate eye movement to the opposite side of the lesion.  Frontal Lobe(Cont. 4)Broca's Area (area 44): Function: motor center for speech. Lesion; motor (expressive) Aphasia; the patient cannot express his ideas in spoken words 5)Exner's Area (area 45): Function: center for writing. Lesion: Agraphia; the patient cannot express his ideas in written words.  Frontal Lobe(Cont. 6)Pre-Frontal Area: Function: 1- higher center for mentality, personality & behavior. 2- inhibition of primitive reflexes which are present in the newborn, e.g. grasp, reflexes. Lesion: 1- mentality, personality & behavioral changes: lack of attention & Judgment, disinterest in people & surroundings, lack of personal hygiene, ending in dementia. 2- Reappearance of primitive reflexes. 7)Paracentral Lobule: Function: cortical inhibition (control) of bladder & bowel voiding Lesion: incontinence of urine & faeces.  Parietal Lobe 1)Cortical Sensory Area (areas 1. 2. 3):post-central gyrus :Function: Perception of cortical sensations from the opposite side of the body; like in the motor area, the body is represented upside down. Lesion: contralateral cortical sensory loss. 2)Angular Gvrus (area 39): Function: in the DOMINANT hemisphere, it is concerned with reading i.e. The recognition & recall of letters & numbers. Lesion: Alexia; the patient who could read before the lesion, becomes unable to do because he cannot understand the letters & numbers which he sees. Parietal Lobe (Cont.)  Temporal Lobe 1)Auditory Sensory Area (area 41, 42): Function: auditory sensory area Lesion: Slight hearing impairment, never deafness as hearing is bilaterally represented. 2)Auditory Associative Area (area 22): Function: recognition & recall of sounds. Lesion: Auditory Agnosia: the patient hears but does not understand (recognize) what he hears.  Occipital Lobe 1)Visual Sensory Area (area 17): for the reception of visual images. 2)Visual Associative Area (area 18.19): anterior to area 17. Function: 1- recognition & recall of images. 2- center for reflex conjugate eye movement to the opposite side e.g. while reading, following the words of a line, one after the other; this movement is usually slow & is termed "pursuit." Lesion to the visual areas results in: 1-Visual Agnosia: the patient sees (e.g. a familiar face) but does not recognize what he sees. 2-Paralysis of reflex conjugate eye movements. Primary Motor Cortex-Area 4/ Somatosensory Precentral Gyrus area 3 2 1-post- central Gyrus Conjugate eye- Area 8 Visual 18 19 Premotor Association Area Area 6 Broca’s Primary 17 Area Visual Cortex Prefrontal Primary 41 42 area Auditory Cortex Wernike’s Exiner’ s Ancus Area 22 Area Area writing Korbinian Broadmann - Learn about the man who divided the Cerebral Cortex into 52 distinct regions: http://en.wikipedia.org/wiki/Korbinian_Brodmann Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings B- Brain Stem The different parts of the “brain stem” seen from in front. The cerebellum is formed of 2 main parts: 1) A midline central structure, known as the vermis. 2) Two cerebellar hemispheres lateral. The cerebellum can also be divided in the following manner: 1. Flocculo-nodular lobe. 2. Anterior lobe. 3. Posterior lobe.  2) Spinal Cord Somatic sensation  Figure 16.1 Ascending (Sensory) Pathways and Tracts in the Spinal Cord Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Figure 16.4b Locations of major descending motor tracts that contain axons of upper motor Copyright © 2009 Pearson Education, Inc., publishing as neurons Pearson Benjamin Cummings The representation of the body in the motor of the cerebral cortex  a) Originates at the primary motor cortex – corticobulbar tracts end at the motor nuclei of CNs on the opposite side of the brain - most fibers crossover in the medulla and enter the lateral corticospinal tracts - rest descend in the anterior corticospinal tracts and crossover after reaching target segment in the SC Figure 16.4a Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Pathway of voluntary motor impulse U.M.N. & L.M.N. This is a spontaneous local axon stretch reflex. The length of any skeletal muscle is shorter than the distance between its origin & insertion. This puts the muscle in a state of constant slight stretch. This stretch stimulates some muscle spindles which send excitatory impulses through the afferent sensory nerve & the dorsal root to the A.H.C. This results in continuous reflex subtetatinic contraction of the muscle; this constitutes the Muscle Tone which is important for the nourishment of the muscles & the posture of the body. The Muscle Tone receives higher control, mainly inhibitory, through the pyramidal & extrapyramidal systems. Therefore: U.M.N.L. (A lesion) results in loss of A inhibition of the intact reflex arc leading to increased muscle tone (spasticity) below the level of the lesion with no wasting of the muscle. L.M.N.L. results in interruption of the reflex arc leading to decreased muscle tone (flaccidity) at the level of the lesion, with wasting of the muscles. This is an induced local axon stretch reflex. It is induced by tapping the tendon of the muscle with a hammer. This tap stretches the muscle with synchronous stimulation of all muscle spindles & activation of the local axon reflex (as in Muscle Tone), resulting in a brief contraction of the muscle. The pyramidal system also exerts an inhibitory effect on this stretch reflex. Therefore: *U.M.N.L. (A lesion) results in exaggeration of deep reflexes (hyperreflexia) below the level of the lesion. *L.M.N.L. results in diminution of deep reflexes (hyporeflexia) at the level of the lesion.  U.M.N.L. L.M.N.L. 1. Paralysis Paralysis or weakness below the Paralysis or weakness at the level level of the lesion. of the lesion. 2. State of muscles NO wasting & if present it is Early & marked wasting due to late & due to disuse. loss of muscle tone. 3. Muscle tone Hypertonia (spasticity) below Hypotonia (flaccidity) at the level the level of the lesion of the lesion. 4. Fasciculations Absent. May be present in irritative lesions of A.H.C. 5. Deep reflexes Hyperreflexia below the level. Hyporeflexia at the level. 6. Pathological May be present. Absent. deep reflexes e.g. patellar & adductor reflex 7. Clonus May be present. Absent. 8. Superficial Lost if lesion is above the Lost if lesion involves the reflexes e.g. abdominals segmental supply of the reflex. segmental supply of the reflex. 9. Plantar reflex + ve, i.e. dorsiflexion of big toe Plantar flexion of toes or no (Babinski) + fanning of other toes. response (never say -ve Babinski). http://study.com/academy/lesson/autonomic-nervous-system-function-definition- divisions.html Video https://www.verywell.com/what-is-the-autonomic-nervous-system-2794823 https://www.researchgate.net/publication/280650893_Autonomic_nervous_system Thank You