فيزياء حيوية Ch02 PDF
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An-Najah National University
Jehad Ahmed ALSHANTY
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This document discusses electricity in the nervous system, focusing on the role of sodium-potassium pumps and the generation of nerve impulses. It also touches upon EEG (electroencephalography), a method for recording the brain's electrical activity.
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Sec.2.1: Electricity in Nervous System Ch.2: Electricity in Human Body 3 النخاع الشوكي Jehad Ahmed ALSHANTY 5 Jehad Ahmed ALSHANTY 6 ...
Sec.2.1: Electricity in Nervous System Ch.2: Electricity in Human Body 3 النخاع الشوكي Jehad Ahmed ALSHANTY 5 Jehad Ahmed ALSHANTY 6 & - ) O & 4 · i ① ② ③ ⑪ "Soma" c) &T I bit "messages - 2nd ge / M 15! 6-8144). - E winF is &... 5 %, - siJ F... Soma /188 & - 4 - · jigs zigns 154/ : wit - - D ⑧ sig ------ S &19 ↳ - - 119 I "message" & I s 95938 Th Jehad Ahmed ALSHANTY 7 Dendrites: هي امتدادات بروتوبالزمية متفرعة لخلية عصبية تنشر التحفيز الكهروكيميائي المستلم من الخاليا العصبية األخرى إلى جسم الخلية. يمكن أن ينشأ هذا االمتداد من جسم الخلية وفي هذه الحالة يسمى التشعبات الحقيقية ،أو يمكن أن يتفرع من المحور العصبي. Jehad Ahmed ALSHANTY 8 Jehad Ahmed ALSHANTY 9 Jehad Ahmed ALSHANTY 10 الخلية العصبية مثل أي خلية أخرى ،لها نواة وميتوكوندريا وعضيات أخرى تطفو جميعها في سائل خاص يسمى السيتوبالزم ،وتحيط بها غشاء بالزما يتكون من طبقة ثنائية الفوسفوليبيد مع بروتينات مدمجة. يفصل غشاء الخلية بين البيئات المائية داخل الخاليا وخارجها في جسم اإلنسان. Jehad Ahmed ALSHANTY 11 Na+ K+ 12 Jehad Ahmed ALSHANTY 13 - 1 = n - 1 Sj Jjm)1s-51 ↑ 2 = , 1 "21 Q ② - -- - T - Jehad Ahmed ALSHANTY 14 Jehad Ahmed ALSHANTY 15 O # is ↑ j S Jw & ⑨ & Boj - Si is D I, i gi 15 ms - - -1&I & & jaqis assed why ? because S - 59- S -& - Q - - Jehad Ahmed ALSHANTY 16 يعد الحفاظ على فرق الجهد هذا ضروريًا للحفاظ على الحالة العصبية للخلية ،كما أنه مهم نظرا ألن الماء ينتقل إلى منطقة ذات تركيز أعلى من األيونات. أيضًا للحفاظ على شكل الخلية ً Jehad Ahmed ALSHANTY 17 It has been estimated that Jehad Ahmed the sodium-potassium pump expends as much as 70% of the total amount of metabolic ALSHANTY 18 energy by the brain. Jehad Ahmed ALSHANTY 19 20 21 22 23 14 25 Jehad Ahmed ALSHANTY 29 Jehad Ahmed ALSHANTY 13 31 اﻟﺤﻮﯾﺼﻼت Vesicles : اﻷﺧﺮاج اﻟﺨﻠﻮي 32 Detecting Neurons Activity EEG MEG Jehad Ahmed ALSHANTY 33 EEG Definition Electroencephalography (EEG) is a functional imaging tool that used to record the brain’s spontaneous electrical activity along the scalp..) ھﻮ أداة ﺗﺼﻮﯾﺮ وظﯿﻔﯿﺔ ﺗُﺴﺘﺨﺪم ﻟﺘﺴﺠﯿﻞ اﻟﻨﺸﺎط اﻟﻜﮭﺮﺑﺎﺋﻲ اﻟﺘﻠﻘﺎﺋﻲ ﻟﻠﺪﻣﺎغ ﻋﻠﻰ طﻮل ﻓﺮوة اﻟﺮأسEEG) ﺗﺨﻄﯿﻂ ﻛﮭﺮﺑﯿﺔ اﻟﺪﻣﺎغ EEG measures voltage fluctuations associated with nerve impulse movements along brain neurons , especially the cortex القشرة الدماغية Hans Berger recorded the first human EEG in 1924. Jehad Ahmed ALSHANTY EEG Signal Sources EEG measures voltages generated by the currents that flow during excitation of the dendrites of many pyramidal neurons in the cerebral cortex, which lies right under the skull and makes up 80% of the brain’s mass. But the electrical contribution of any single cortical neuron is extremely small, and the signal must penetrate several layers of non-neural tissue, including fluid, bones of the skull, and skin, to reach the electrodes. بما في، يجب أن تخترق اإلشارة عدة طبقات من األنسجة غير العصبية. للوصول إلى األقطاب الكهربائية، ذلك السوائل وعظام الجمجمة والجلد Therefore, it takes many thousands of underlying neurons, activated together, to generate an EEG signal big enough to see at all. pyramidal neurons are a type of multipolar neuron found in areas of the brain Video Recording EEG Signal In neuroscience experiments, we are often less concerned with the activities of single neurons than with understanding the activity of a large population of neurons. The EEG is a measurement techniques that enables us to overview the generalized activity of the cerebral cortex. غير جراحي Recording an EEG is relatively simple. The method is usually non-invasive, and it is painless. معجون موصل The electrodes are wires taped to the scalp, along with conductive paste to ensure a low-resistance connection. جنبًا، األقطاب الكهربائية عبارة عن أسالك مثبتة على فروة الرأس.إلى جنب مع معجون موصل لضمان اتصال منخفض المقاومة Jehad Ahmed ALSHANTY 5) sig - Waves : Amplitude , frequency - -- &o j9/ L 39 Recording EEG Signal Some two dozen electrodes are fixed to standard positions on the head and connected to banks of amplifiers and recording devices. Small voltage fluctuations, few tens μV in amplitude, are measured between selected pairs of electrodes, usually to a reference. The typical EEG record is a set of many simultaneous wavy lines, indicating voltage changes between pairs of electrodes with time. The horizontal axis represents time and the vertical axis indicates the voltage of the signal. Jehad Ahmed ALSHANTY EEG Signal Types In healthy adults, the amplitudes and frequencies of such signals change from one state of a human to another, such as waking and sleeping. The characteristics of the waves also change with age. There are four major brain waves distinguished by their different frequency ranges. These frequency bands from low to high frequencies, respectively, are called delta (δ), theta (θ), alpha (α), beta (β). It good to know than analysis of an EEG will never tell us what a person is thinking, it can help us know if a person is thinking. Jehad Ahmed ALSHANTY Brain Waves Characteristics 1. Delta waves lie within the range less than 4 Hz. These waves are primarily associated with deep sleep (non-dreaming). 2. Theta waves lie within the range of 4–7.5 Hz. Theta waves appear as consciousness slips towards drowsiness..تظهر موجات ثيتا عندما ينزلق الوعي نحو النعاس 3. Alpha waves appear in the posterior half of the head. Its frequency lies within the range of 8–13 Hz. Alpha waves have been thought to indicate both a relaxed awareness without any attention or concentration.. يُعتقد أن موجات ألفا تشير إلى استرخاء الوعي دون أي انتباه أو تركيز. هرتز13-8 يقع ترددها في نطاق.تظهر في النصف الخلفي من الرأس 1. Beta wave are the fastest, is anything greater than 14+ Hz. Its is the usual rhythm of the brain associated with active thinking, attention, focus on the outside world, or solving concrete problems, and is found in normal adults. Some references called high frequencies beta wave (>30 Hz) as Gamma wave > - / -03 MEG EEG Il g 2 Definition Signal detection Applications MEG vs. EEG Egg Jehad Ahmed ALSHANTY 44 Gr Video # j8 53 ⑤ - w MEG Definition Magnetoencephalography (MEG) is a functional imaging tool - - sen 3154. that used T to record of the weak magnetic fields produced by electrical currents occurring naturally in the brain, using very sensitive magnetometers. L & s Y - 19 & --i join j j - & % % 0. The magnetic signals emitted by the brain are on the order of a few femto-teslas, which caused delaying in the discovery until 1968 , when David Cohen find a suitable method to isolate the environmental magnetic noise and invent a proper shielding technique. J3 Sitis us Jehad Ahmed ALSHANTY · J * ⑧ T & "T" Jo -- g T # unit 1) & 0 MEG 11 * - MEG Signal Source An electric current is always associated with a magnetic field perpendicular to its direction. The magnetic permeability of biological tissues is almost the same as that وبالتالي فإن المجال المغناطيسي ال يتشوه بفروة الرأس أو الجمجمة، النفاذية المغناطيسية لألنسجة البيولوجية هي نفسها تقريبًا مثل نفاذية الفضاء الفارغ of empty space and so the magnetic field is not distorted by scalp or skull. Which allow the detection of this magnetic fields by MEG outside the head. Jehad Ahmed ALSHANTY & S - =n = ,59326100524/ / MEG Signal Detection These neuromagnetic signals generated by the brain are extremely small. Therefore, MEG - - scanners require superconducting sensors called SQUID (superconducting quantum - ↳..1 Dis y interference device). & = 2 , 5 % 6/ impedance: اعاقة ↳ The SQUID sensors are bathed in a large liquid helium cooling unit E at approximately -269 degrees C. Due to low impedance at this temperature, the SQUID device can detect and amplify magnetic gay fields generated by neurons a few centimetres away from the sensors. jadise راس المريض Jehad Ahmed ALSHANTY Goi 3 log Induced Current Jehad Ahmed ALSHANTY 49 MEG Signal Detection Example of a real MEG signal. This signal is filtered to found a net signal that correspond to a specific brain activity. Jehad Ahmed ALSHANTY MEG vs. EEG a. Both EEG and MEG use the same underlying signal but generate different output. However MEG fields pass through the head without any distortion which provides a high spatial and temporal resolution عبر الرأس دون أي تشويه مماMEG تمر حقول، ومع ذلك. نفس اإلشارة األساسية ولكنهما يولدان مخرجات مختلفةMEG وEEG يستخدم كل من يوفر دقة مكانية وزمنية عالية a. Both are a functional neuroimaging technique for mapping brain. Jehad Ahmed ALSHANTY MEG vs. EEG c. Since SQUIDS are very sensitive vector magnetometers. Thus MEG can measured action field from particular direction only. Also, sometime currents associated with action potentials in some neurons flow in opposite directions and the magnetic fields cancel out. While EEG measure signals from all the neurons. Jehad Ahmed ALSHANTY 54 55 إيجابيات وسلبيات 56