Neurophysiology Past Paper PDF

Neurophysiology Neurophysiology VER12: The Nervous System: 161- 169 VER15: Autonomic Nervous System: 239-249, The Nervous System: 163- 171...

Neurophysiology Neurophysiology VER12: The Nervous System: 161- 169 VER15: Autonomic Nervous System: 239-249, The Nervous System: 163- 171 Organs with and without dual innervation: 256 Autonomic Nervous System: 244-252 (end at Responses to VER13: adrenergic stimulation), The Nervous System: 163- 171 Organs with and without dual innervation: 258-260 Autonomic Nervous System: 243-252 (end at Responses to adrenergic stimulation), VER16: Organs with and without dual innervation: 258-260 The Nervous System: 160- 170 VER14: Autonomic Nervous System: 242-251 (end at Responses to The Nervous System: 163- 171 adrenergic stimulation), Autonomic Nervous System: 244-252 (end at Responses to Organs with and without dual innervation: 258-260 adrenergic stimulation), Organs with and without dual innervation: 258-260 For any version, extra details beyond what we talk about in class are not needed for Tables 9.2-9.3, Figures 9.2-9.4, 9.6 (though what is in class or on the slides provided is fair game!). 1 2 Introduction to Neurophysiology L e a r n in g O u t c o m e s 1. What is neurophysiology Nervous system structure = Anatomy 2. Functional classification of neurons Nervous system function = Physiology 3. Structural classifications of brain cells 4. Blood brain barrier In this course, to understand physiology, we’ll need to 5. Organization of the nervous system know a little neuroanatomy and microanatomy. 6. Critical Thinking 3 4 Introduction 1  Introduction to Neurophysiology Introduction to Neurophysiology Nervous system structure = Anatomy Nervous system function = Physiology Two main divisions: Brain and spinal cord: Minimal functional “unit” of nervous system = Central Nervous System (CNS) Neuron (This is considered the “Neuron Doctrine” - Peripheral nerves and ganglia: Ramon y Cajal, 1800s) Peripheral Nervous System (PNS) fundamental concept: nervous system is made up of discrete individual cells 5 6 Introduction to Neurophysiology Introduction to Neurophysiology Two functions of the nervous system: Why is physiology so intimately associated with anatomy in the nervous system? 1) Control of movement and some functions = Motor Nerves Neurons really only do 2 (3) things: 2) Detection of external stimuli = Sensory Nerves 1. Conduct “Electrical” Signals (Action Potentials) Motor Sensory 2. Release “Chemical” Signals (Neurotransmitters) Therefore - much of what the nervous system “does” (ie. neurophysiology) depends on where these processes occur (ie. neuroanatomy). 7 8 Introduction 2  Introduction to Neurophysiology Introduction to Neurophysiology Why study neurophysiology? Third function of the nervous system: To understand inherited and acquired diseases 3. Integration of neuronal activity and connections To understand drug modulation (“Circuitry”): Association Neurons Because it is interesting These are the neurons within the CNS responsible for behaviour, thought, emotions etc. 9 10 Neurons and Synapses Neurons and Synapses Neuron: basic functional unit of the nervous system - Cell body, dendrites, axons A neuron performs Dendrites: receive information from sensory receptors the function of moving (or from other cells) and send it to the cell body “information” rapidly by conducting Axons deliver electric signals from the cell body to electrical impulses another neuron or an effector organ (e.g. a muscle) called Action Potentials from one physical location to another, then converting the electrical impulse to a chemical signal at a Synapse. 11 12 Introduction 3  Functional Classification of Neurons Functional Classification of Neurons Functional classification is based on the direction in “ASSOCIATION”, or “INTERNEURONS” are located which they conduct impulses. entirely within the CNS and help integrate CNS functions “SENSORY”, or “AFFERENT” neurons conduct impulses from sensory receptors INTO the CNS… 13 14 Functional Classification of Neurons Functional Classification of Neurons “MOTOR”, or “E FFERENT” neurons conduct impulses Somatic Motor Neurons: reflex & voluntary control of from sensory receptors OUT OF the CNS (to skeletal muscles effector organs like muscles or glands… 15 16 Introduction 4  Functional Classification of Neurons Functional Classification of Neurons Autonomic Motor Neurons: INvoluntary control of Autonomic Neurons: Further subdivided as smooth muscle, cardiac muscle, and glands sympathetic & parasympathetic 17 18 Functional Classification of Neurons Functional Classification of Neurons: Simple Neural Circuit 19 20 Introduction 5  Functional Classification of STRUCTURAL Classification of Neurons 4 types of Neurons: Neurons: Simple Neural Circuit - Pseudopolar (unipolar), sensory, 1 process that splits. 1) Sensory, Afferent (carry signals to CNS). - Bipolar, retinal and cochlear, 2 processes. 2) Motor or Efferent (carry signals from CNS). - Multipolar, most common, motor & association, many 3) Interneurons dendrites but one axon. - send signals from one neuron to another - Anaxonic, some CNS neurons, no obvious axon Pearson Education Inc 21 22 There are at least as many supporting cells as there are nerve cells in the human brain (1011-1012)…. 23 24 Introduction 6  STRUCTURAL Classification of Neurons STRUCTURAL Classification of Neurons Supporting Cells: PNS Supporting Cells: CNS - Schwann Cells – form myelin sheaths around PNS neuron axons - Oligodendrocytes – form myelin sheaths around CNS neuron axons (like Schwann cells in PNS) - Satellite cells – support neuron cell bodies within ganglia of the PNS - Microglia – migrate through CNS & phagocytose debris - Astrocytes – help regulate external environment of neurons in CNS - Ependymal cells – line the ventricles (cavities) of the brain and spinal cord. 25 26 STRUCTURAL Classification of Neurons STRUCTURAL Classification of Neurons Supporting Cells: CN S Supporting Cells: PN S CN S Successive wrapping of One oligodendrocyte forms Schwann cell membrane around myelin sheaths around several one axon, cytoplasm on outside. axons. 27 28 Introduction 7  Neurons or Nerve cells STRUCTURAL Classification of Neurons Supporting Cells: CNS - Oligodendrocytes – form myelin sheaths around CNS neuron axons (like Schwann cells in PNS) - Microglia – migrate through CNS & phagocytose debris - Astrocytes – help regulate external environment of neurons in CNS - Ependymal cells – line the ventricles (cavities) of the brain and spinal cord. https://www.youtube.com/watch?v=cUGuWh2UeMk 29 30 STRUCTURAL Classification of Neurons STRUCTURAL Classification of Neurons Supporting Cells: CN S Supporting Cells: PN S CN S Successive wrapping of One oligodendrocyte forms Schwann cell membrane around myelin sheaths around several one axon, cytoplasm on outside. axons. 31 32 Introduction 8  STRUCTURAL Classification of Neurons STRUCTURAL Classification of Neurons Supporting Cells: CNS Supporting Cells: CNS 1. Take up K+ from ECF (diffuses from neurons during nerve impulses), may help maintain proper ionic environment for neurons. Astrocytes – most abundant glial cell in the CNS, constituting up to 90% of the nervous tissue in some areas of the brain. Processes terminate in “end feet” at capillaries, others on neurons (axon, cell body, or dendrite) thus they can influence interactions between neurons and blood. 33 34 STRUCTURAL Classification of Neurons STRUCTURAL Classification of Neurons Supporting Cells: CNS Supporting Cells: CNS 3. The “end-feet” surrounding blood capillaries take up 2. Can take up neurotransmitter glutamate and glucose from blood, metabolize it to lactate, then transform it to glutamine, which can be released back release it for use as an energy source by neurons, which into neurons, which can use it to reform the metabolize it aerobically into CO2 & H2O for production neurotransmitter glutamate. of ATP. 35 36 Introduction 9  STRUCTURAL Classification of Neurons STRUCTURAL Classification of Neurons Supporting Cells: CNS Supporting Cells: CNS 4. Astrocytes are needed for the formation of synapses in the CNS. 5. Astrocytes regulate neurogenesis in the adult brain (needed for stem cells to differentiate into both glial cells and neurons). 6. Help with the formation of the blood-brain barrier. 7. Release neurotransmitters (glutamate, ATP, adenosine, D-serine, others) that can stimulate or inhibit activity of neurons. 37 38 Blood Brain Barrier If you inject a green dye into the bloodstream, all the tissues in the body will turn green except for the brain. Capillaries in the brain, UNLIKE those of most other organs, do not have pores between adjacent endothelial cells (the cells that make up the walls of the capillaries). Instead, the endothelial cells of the capillaries are joined by tight junctions. 39 40 Introduction 10  Blood Brain Barrier Blood Brain Barrier Nonpolar O2 and CO2 can move through, and organic Astrocytes influence the structure and function of the molecules including alcohol and barbiturates can pass blood brain barrier. through the phospholipid components of the plasma membrane. Other molecules have to go through specific processes (e.g. active transport, endocytosis). 41 42 Blood Brain Barrier Nicotine binds acetylcholine receptors. Other components in tobacco smoke decrease MAO activity 43 44 Introduction 11  Blood Brain Barrier S o w h y d o p e o p le s t ill s m o k e ? CNS depressant, directly affects brain cells. Affects areas involved in inhibiting behaviours (animated, talkative, social). Also altered speech, slowed reaction time, foggy memory. Reactions depend to some part on dose, size, weight, gender, genetics, etc. 45 46 Blood Brain Barrier Blood Brain Barrier Rabies – deadly viral infection – bit by an infected Inhibition of NO through a variety of animal. neurotransmitter receptors including N-methyl-D- aspartate and substance P. 47 48 Introduction 12  Blood Brain Barrier Blood Brain Barrier Virus infects the brain. Immune cells and antibodies can’t enter the brain. Drug treatments and BBB – especially neurological disorders. Brain Cancer Parkinson's Alzheimer's Dementia There is no treatment after symptoms appear, but before, rapid treatment with anti-rabies antibodies can help attenuate the infection. 49 50 R e v ie w Blood Brain Barrier Medscape Medical News > Neurology Astrocytes influence the structure and function of the Blood-Brain Barrier Safely Breached blood brain barrier. November 8, 2015 Doctors at Sunnybrook Health Sciences Centre in Toronto, Ontario, Canada, have noninvasively penetrated the blood-brain barrier to deliver a chemotherapeutic agent directly into ONE patient’s malignant brain tumor. This is the first time that the blood-brain barrier has been safely breached in a human, the researchers say. The Toronto doctors hope that the technique they used, focused ultrasound, will continue to be successful in safely penetrating what has been a persistent obstacle to treating not only brain tumors but also other diseases, such as Alzheimer's disease and Parkinson's disease. 51 52 Introduction 13  Two main divisions: Central Nervous System (CNS): Brain and spinal cord: Peripheral Nervous System (PNS): Peripheral nerves and ganglia: 53 54 Organization of the Nervous System Somatic Nervous System Somatic = have cell bodies in the CNS & send axons to NERVOUS SYSTEM skeletal muscles (usually those under voluntary control). e.g. conduct impulses along a SINGLE axon from the Peripheral NS CNS spinal cord to the neuromuscular junction. Spinal Afferent Efferent Brain cord Somatic Autonomic SNS PSNS 55 56 Introduction 14  Autonomic Nervous System Autonomic = involves TWO neurons in the efferent pathway. 1st - cell body in the CNS gray matter (brain or spinal cord). This axon does not directly innervate the effector organ, but instead synapses with a 2nd neuron in this pathway, called a postganglionic neuron, that has an axon that extends from the autonomic ganglion to an effector organ, where it synapses with the target tissue. Text Table 9.1 57 58 Divisions in the Autonomic Nervous System Autonomic Nervous system helps regulate the activities of glands, smooth muscles, and cardiac muscle. Integral aspect of the physiology of most body systems. ANS further subdivides into: 1. Parasympathetic Division 2. Sympathetic Division 59 60 Introduction 15  Divisions in the Autonomic Nervous Divisions in the Autonomic Nervous Parasympathetic Nervous System (PSNS) System Sympathetic Nervous System (SNS) System “Rest & digest” “Fight or flight” - Reuters 61 62 Divisions in the Autonomic Nervous System Most organs receive input from both systems In general, PSNS and SNS mediate op p os in g responses in effector organ - MJ Mycek Sympathetic= RED Parasympathetic= BLUE Text Fig. 9.5 63 64 Introduction 16  Proof of evolution that you can find on your own body Divisions in the Autonomic Nervous System Organs without dual innervation: - Adrenal medulla - Arrector pili muscles in the skin (muscle associated with hair that makes your hair “stand on end”) - Sweat glands in the skin - Most blood vessels In these cases, regulation is achieved by increases or decreases in the tone (firing rate) of the sympathetic fibers. 65 66 Neurotransmitters in the Autonomic AUTONOMIC OUTFLOW TRACTS Nervous System Parasympathetic Outflow Autonomic nerves classified based on primary CNS Ganglion Preganglionic Axon Postganglionic Axon neurotransmitter released across the synapses ACh ACh Effector Cell (Cholinergic) (Cholinergic) Acetylcholine (ACh) Neuroeffector Junction Norepinephrine (NE) Sympathetic Outflow Cholinergic neurons = release ACh CNS Ganglion Adrenergic neurons = release NE (or E) Preganglionic Axon Postganglionic Axon ACh NE Effector Cell (Cholinergic) (Adrenergic) ACh and NE bind different receptors to mediate Neuroeffector Junction target organ response 67 68 Introduction 17  Notes to previous slide: 1. ACh is the neurotransmitter for all PREganglionic fibers (both sympathetic & parasympathetic). Since they use Ach, transmission is said to be cholinergic. 2. ACh is also the transmitter released by most parasympathetic postganglionic fibers at their synapses with effector cells. Transmission at these synapses is thus said to be cholinergic. 3. The neurotransmiter relased by most sympathetic nerve fibers is NE. Transmission at these synapses is said to be adrenergic. 69 70 ANS Dysfunction ANS Dysfunction ANS controls a number of functions in the body, such as HR, BP, digestive tract peristalsis, sweating, etc. Dysfunction of the ANS can involve any of these functions. “Lyme Disease” Deer ticks carrying Borrelia burgdorferi Dysautonomia may also be caused by brain injury, diabetes, genetics, etc…. 71 72 Introduction 18  ANS Dysfunction ANS Dysfunction Bit by infected tick, substances in tick saliva disrupt the local immune response. Spirochetes multiply in the skin. Immune response causes the characteristic circular lesion, but neutrophils which are necessary to eliminate the infection fail to appear. Bacteria spread via the bloodstream to joints, heart, nervous system, and distant skin sites. 73 74 SUMMARY: Organization of the Nervous System NERVOUS SYSTEM Peripheral NS CNS Spinal Afferent Efferent Brain cord Somatic Autonomic SNS PSNS HR, BP 75 76 Introduction 19  A common form of synesthesia (grapheme, or color synesthesia, or color-graphemic synesthesia) letters or numbers are perceived as inherently colored 77 78 S y n a e s t h e s ia : W h e n c o lo u r e d s o u n d s t a s t e s w e e t Nature 434, 38 (2005). Beeli, Esslen, Jäncke “ S o m e m u s ic ia n s h a v e c h r o m o t h e s ia - a f o r m o f “Here we describe the case of a musician who experiences different tastes in response to hearing different musical tone s y n e s t h e s ia w h e r e t h e y h e a r m u s ic a s c o lo r s. intervals….” Table 1 Tastes triggered by tone M ozart … intervals Tone interval Taste experienced Minor second Sour - D M ajor had a w arm "orangey" sound Major second Bitter - B f la t m in o r w a s b la c k is h. Minor third Salty - A m a j o r w a s a r a in b o w o f c o lo r s. Major third Sweet Fourth (Mown grass) Tritone (Disgust) Fifth Pure water Minor sixth Cream Major sixth Low-fat cream Minor seventh Bitter Major seventh Sour Octave No taste Tastes experienced by synaesthete E.S. in response to different musical 79 80 Introduction 20  Synaesthesia: The average person can hold about 7 digits in working memory at any given time. 5 5 5 -1 2 1 2 π is a mathematical number - It is the ratio of a circle's circumference to its diameter. - 3.14159 81 82 A Japanese mathematician and a U.S. grad student smashed the world record for calculating the value of Pi. After a manic 371 days of computing, Shigeru Kondo and Alexander Yee reached 10 trillion decimal places, doubling the previous record. To give you a sense of how big that is: It would take an average person 158,000 years to recite every last digit. New York-based interdisciplinary designers TWO-N, Inc. wanted to pay homage to the mathematicians’ remarkable discovery, so they decided to visualize a subset of Pi as pixel art. They took Pi’s first 4 million decimals and assigned each digit a different color.” 83 84 Introduction 21  L e a r n in g O u t c o m e s high-functioning autism, savant syndrome, numerical synesthesia 1. What is neurophysiology T h e M a n W h o M e m o r iz e d P i ( A p r. 2 0 0 5 ) 2. Functional classification of neurons - sensory, afferent, associating, interneurons, motor, efferent 3. Structural classifications of brain cells - Central vs. peripheral types of cells NEW YORK--When Daniel Tammet set the European record for pi memorization last year, memorizing 22,514 digits in just over 5 4. Blood brain barrier hours, he attributed the feat to his ability to see numbers as complex, 3-dimensional landscapes, complete with color, texture, 5. Organization of the nervous system and sometimes even sound. 6. Critical Thinking 85 86 ELECTRICAL ACTIVITY: Electrical Activity in Axons Ver 12: Pages 53 (fluid mosaic model); Pages 170 - 182 (nervous system) Ver 13: Pages 53 (fluid mosaic model); Pages 172 - 185 (nervous system) Ver 14: Pages 53 (fluid mosaic model); Pages 172 – 185 (nervous system) Ver 15: Pages 53 (fluid mosaic model); Pages 172 – 185 (nervous system) Ver 16: Pages 51-52 (fluid mosaic model); Pages 170 – 182 (nervous system) 87 88 Introduction 22  The Cell Membrane L e a r n in g O u t c o m e s Cell membrane is j u s t 2 m o le c u le s 1. Cell Membranes t h i ck. 2. Electrical Activity in Axons 3. Action Potentials 2 phospholipid 4. Synapses m o le c u le s t h i c k. 5. Critical Thinking 89 90 The Cell Membrane – The Cell Membrane – Fluid Phospholipid Bilayer Mosaic Model Extracellular O u t s i d e ( E X T R A C E LLU LA R ) Glycolipid Glycoprotein Phospholipid Heads & tails I n s i d e (I N T R A C E LLU LA R ) Cholesterol Proteins Intracellular 91 92 Introduction 23  The Cell Membrane – Fluid Mosaic Model The Cell Membrane M o le c u le s c a n n o t g e t a c r o s s t h e c e ll m e m b r a n e very easily- it is a barrier. But some still have to cross. How? A. B y S I M P LE D I F F U S I O N – a p r o ce ss t h a t d o e s no t co nsu m e e ne r g y http://www.youtube.com/watch?v=Qqsf_UJcfBc 93 94 The Cell Membrane The Cell Membrane Simple diffusion (passive) Simple diffusion (passive) Small uncharged molecules (relatively lipid soluble) can Small charged molecules (ions) can diffuse through diffuse through the lipid bilayer (e.g. steroid water-filled pores hormones) OUT OUT IN IN 95 96 Introduction 24  The Cell Membrane The Cell Membrane Simple diffusion (passive) Simple diffusion (passive) Ion Channels – some are “leaky”, ions flow in or out as Ion Channels – others are VOLTAGE GATED – can needed. only be opened or closed by gates. OUT OUT IN IN 97 98 A CTI V E t r a nspor t The Cell Membrane The Cell Membrane So, there are other mechanisms to move substances in and out of End ocy t osis, e xocy t osis, ph a gocy t osis…. a nd so on cells, against gradients, active transport needs metabolic energy (usually ATP). - e.g. Na +/K + ATPase - Moves Na+ ( ) out of cell - Moves K+ ( ) into cell OUT IN Primary active transport (Direct consumption of ATP) ATP ADP 99 100 Introduction 25  The Cell Membrane Summary Electrical Activity in Axons Cell membranes act as barriers to chemical movement All cells in the body have a potential difference – or voltage – across the membrane. This is called the Integral membrane proteins can act as transporters resting membrane potential. Movement of substances across the membrane can be The inside of the cell is negatively charged compared to passive (diffusion) or active (consumes energy) the outside. + + + + + + + + + Active transport of Na+/K+ is important in In neurons, it is -70mV. establishing the electrochemical gradient. Ion channels are especially important in the nervous system because they help produce electrical impulses that transmit information rapidly. - - - - - - - - - - - 101 102 Electrical Activity in Axons Electrical Activity in Axons Voltage gated ion channels are important for electrical So the channels are initially closed, they open, this activity in axons because when the channels open they allows the ions (whatever they are – Na+, K+, Ca2+ etc) can change the membrane potential of the cell. to move across the membrane. This is what we need to happen to conduct an electrical N a + s t a r t s o u t s id e , signal in neurons. K + in s id e + + + + + + + + + A t s t a r t o f a c t io n + + + + + + + + + p o t e n t ia ls - - - - - - - - - - - - - - - - - - - - - - 103 104 Introduction 26  Action Potentials Action potentials are signals that go along the nerves, taking the signal from one place to another place. Nervous System preserved using Dr von Hagens' controversial "plastination" technique. — at O2 Areana London. 105 106 Action Potentials Action Potentials A p r im a r y f u n c t io n o f n e r v e c e lls is t o r e c e iv e , c o n d u c t , a n d t r a n s m it s ig n a ls. l Action potentials are momentary discharges (depolarizations) of the resting membrane potential caused by a rapid influx of Na+ caused by the opening of sodium ion channels l Once initiated they move along the axon membrane toward the synapse N e u r o n s p r o p a g a t e s ig n a ls in t h e f o r m o f a c t io n p o t e n t ia ls. 107 108 Introduction 27  Action Potentials Ion Gating in Axons This can happen as the ions Na+ and K+ move across l Signals have to go a long way without weakening the plasma membrane. l So the signals have to be continuously reamplified They move through gated channels. along the way. l To do this, they use voltage- gated ion channels 109 110 Ion Gating in Axons A B Ion Gating in Axons I f a p p r o p r ia t e s t im u la t io n c a u s e s p o s it iv e c h a r g e s t o f lo w in t o t h e c e ll, s o t h e c e ll b e c o m e s m o r e P O S I T I V E t h e n t h e r e s t in g p o t e n t ia l, t h is c h a n g e is A. C h a n n e l c lo s e d a t c a lle d d e p o la r iz a t io n (o r H Y P O p o la r iz a t io n). r e s t in g m e m b r a n e p o t e n t ia l. B. G ated channel C o p e n s in r e s p o n s e t o d e p o la r iz a t io n C. G ated channel c lo s e s (b a ll & c h a in ). 111 112 Introduction 28  Action Potentials Action Potentials Na+ channels open lThe explosive increase in Na+ permeability N a+ (remember, Na+ starts outside) results in a rapid reversal of membrane potential in that region, from -70 mV to -------++------------------------------------- +30 mV. The axon is depolarizing. +++++--++++++++++++++++++++++++++++++++++ N a+ Na+ channels open lAt that point, the Na+ channels close. There is a rapid decrease in Na+ permeability. ----------------++----------------------------- ++++++++++++++--+++++++++++++++++++++++++++ Na+ Na+ channels open -------------------------++------------------ +++++++++++++++++++++++ +--+++++++++++++++++ 113 114 Action Potentials Action Potentials T he N a+ and K+ p u m p s a r e c o n s t a n t ly lTo help compensate, the cell needs to w o r k in g in t h e p la s m a repolarize. m em brane. T hey pum p out the N a+ that entered the lTo do this, K+ which is also positively a x o n d u r in g a n a c t io n charged will diffuse out of the cell, making p o t e n t ia l a n d p u m p in the inside of the cell less positive (or more t h e K + t h a t h a d le f t. negative) again, restoring the original resting membrane potential. 115 116 Introduction 29  Action Potentials Voltage Gated Channels Because opening the gated Na+ and K+ channels is stimulated by depolarization, these ion channels in the axon membrane are said to be voltage-regulated channels, or voltage-gated channels. https://www.youtube.com/watch?v=mKalkv9c 2iU 117 118 How Action Potentials are Action Potentials Propagated Membrane potential does not normally become more positive than 30 mV because the Na+ channels quickly close and the K+ channels open. The amplitude (size) of actions potentials is therefore ALL or NONE. If depolarization reaches the threshold, the maximum potential https://www.youtube.com/watch?v=Sa1wM750Rvs change is reached. 119 120 Introduction 30  Action Potentials Action Potentials – Non-myelinated vs. Saltatory conduction APs are sometimes In non-myelinated axons, the action potential passes called smoothly along the axon, and all parts of the membrane “Spike” are depolarized. potentials. N a+ -------++------------------------------------- +++++--++++++++++++++++++++++++++++++++++ 121 122 Action Potentials – Non-myelinated vs. Action Potentials – Saltatory conduction Saltatory conduction In myelinated axons, the action potential jumps between the non-insulated nodes [of Ranvier] by saltatory conduction. Allows more rapid movement of the action potentials, and needs less energy to restore the membrane after Refractory period (here or in the action potential has been transmitted. unmyelinated neuron) helps ensure the AP only goes in one direction down the axon to it’s end 123 124 Introduction 31  The Synapse The Synapse Axons end close to or contacting Once action potentials reach the end of the another cell. axon, they stimulate the next cell. Postsynaptic neuron Presynaptic neuron 125 126 The Synapse The Synapse D ir e c t io n a l: P R E s y n a p t ic – t o – P O S T s y n a p t ic. I n t h e C N S , t h e 2 nd c e ll is a ls o a n e u r o n. I n t h e P N S , it m a y b e a n e u r o n , o r a n e f f e c t o r c e lls w it h in a m u s c le o r g la n d. Neuron: neuron Neuromuscular junction 127 128 Introduction 32  The Synapse The Synapse Presynaptic nerve ending releases neurotransmitters that stimulate APs in the postsynaptic cell. Presynaptic neuron ends in a terminal bouton (because of it’s swollen appearance) and it is separated from the postsynaptic cell by a tiny cleft ~10nm in size. contain neurotransmitters 129 130 The Synapse The Synapse O n t h e P O S T s y n a p t ic s id e , t h e n e u r o t r a n s m it t e r b in d s t o it s r e c e p t o r o n t h e d e n d r it e. T h is c a u s e s io n c h a n n e ls o n t h e p o s t s y n a p t ic d e n d r it e m em brane to open. N o t e , t h e s e g a t e s a r e c h e m ic a lly r e g u la t e d (i.e. n o t v o lt a g e - r e g u la t e d a s in t h e a x o n s ). A n d t h is s t im u la t e s t h e c e ll t o p r o d u c e A P... http://www.georgiapainphysicians.com/l2_edu_pharma_mod1_s es.htm 131 132 Introduction 33  The Synapse EPSP = excitatory postsynaptic potential (depolarization in the post-synaptic neuron) C. Nicolay 133 134 Myotonia n e u r o m u s c u la r d is o r d e r s c h a r a c t e r iz e d b y d e la y e d r e la x a t io n o f s k e le t a l m u s c le a f t e r v o lu n t a r y c o n t r a c t io n o r e le c t r ic a l s t im u la t io n. C an b e caused by mutations in muscle Cl- channel (human, dog, etc) à channel gates do not open properly à repolarization delayed, several APs fire instead of just one 135 136 Introduction 34  Myotonic "Fainting" Goats http://www.youtube.com/watch?v=j5kKoBOfPJk 137 138 Myotonia Goats: when startled or excited it causes a very temporary stiffening of the muscles. When the muscles relax after a few seconds the animal jumps up and continues on it’s way. “ A s p e t s , m y o t o n ic g o a t s a r e p o o r c lim b e r s (e a s ily c o n t a in e d ) a n d h a v e a w o n d e r f u l d is p o s it io n. T h e y t a m e e a s ily w h e n f e d a n d h a n d le d r e g u la r ly a n d c a n b e v e r y lo v in g p e t s.” N o t s u p p o s e d ly p a in f u l in g o a t s. 139 140 Introduction 35  “This myotonic syndrome produces a higher meat-to- S um m ary: bone ratio (3:1 instead of 2:1) and a thicker L e a r n in g O u t c o m e s musculature with a more tender nature that has earned myotonic goats a place on the Slow Food Ark of Taste.” 1. Cell Membranes 2. Electrical Activity in Axons 3. Action Potentials 4. Synapses 5. Critical Thinking The US Ark of Taste is a catalog of over 1319 delicious foods in danger of extinction 141 142 T h e p r e s e n t t h a t y o u r b r a in c o m p r e h e n d s is a r o u n d 5 0 0 m illis e c o n d s b e h in d w h a t is a c t u a lly “ h a p p e n in g ,” a s y o u r b r a in s c r a m b le s f r a n t ic a lly t o k e e p u p a n d m a in t a in c o h e r e n c e. Everything we perceive is in the past 143 144 Introduction 36  CENTRAL NERVOUS SYSTEM: CENTRAL NERVOUS SYSTEM: Ver12: Ver15: Spinal Nerves p. 232, images p. 234, 235; Brain 204- 208 (exclude Figure Spinal Nerves p. 236, images p. 236, 238; Brain 207- 212 (exclude Figure 8.7); Cerebral lateralization: 212-214 (up to language); Brain Function, 8.7, 8.8); Cerebral lateralization: 216-217 (up to language); Brain 221-224; Midbrain: 191, 225-226; Hindbrain, Medulla : 226-227 Function, 224-228 (Start at Emotion and Memory, end at Midbrain); Midbrain: 193, 228-230; Hindbrain, Medulla : 230-231 Ver13: Ver16: Spinal Nerves p. 236, images p. 238, 239; Brain 207- 212 (exclude Figure Spinal Nerves p. 234-236; Brain 205- 214 (exclude Figure 8.2, 8.7, 8.8); Cerebral lateralization: 217-218 (up to language); Brain 8.4, 8.7, 8.8); Cerebral lateralization: 214-216 (up to language); Function, 224-228; Midbrain: 193, 229-230; Hindbrain, Medulla : 230-231 Brain Function, 223-227 (Start at Emotion and Memory, end at Midbrain); Midbrain: 191, 227-228; Hindbrain, Medulla : 228-229 Ver14: Spinal Nerves p. 236, images p. 236, 238; Brain 207- 212 (exclude Figure 8.7, 8.8); Cerebral lateralization: 216-217 (up to language); Brain Function, 224-228 (Start at Emotion and Memory, end at Midbrain); Midbrain: 193, 229-230; Hindbrain, Medulla : 230-231 145 146 L e a r n in g O u t c o m e s The Central Nervous System 1. Protection of the CNS The CNS is composed of gray matter and white matter. 2. Reflexes The gray matter, containing neuron cell bodies and 3. Brain Development dendrites, is found in the cortex (surface layer) of the 4. Major Brain Regions brain and deeper within the brain in aggregations known – cerebrum, cerebral cortex, thalamus, epithalamus, as nuclei. hypothalamus, midbrain, hindbrain (cerebellum, medulla). 5. Critical Thinking White matter consists of axon tracts (myelin sheaths produce white color) that underlie the cortex, and that surround the nuclei. 147 148 Introduction 37  The Central Nervous System Protection of the CNS: Meninges of the Scalp brain Skull Dura mater (“tough mother”) [two layers] Gray matter Arachnoid mater (think…webby/spidery) Pia mater (innermost White matter membrane, clings to surface of Brain brain/spinal cord, follows every fold. The brain is encased in the skull; it is also protected by several tough layers of connective tissue (the meninges), the dura mater, the arachnoid mater, and the pia mater …. “P”… “A”…. “D”…. “S”…. 149 150 Protection of the CNS: Meninges of the Protection of the CNS: Spinal Cord Cerebrospinal fluid Skull Pia mater Outer Inner fluid fluid Arachnoid mater cushion cushion Brain Dura mater In addition to the skull and meninges, the brain The same meningeal layers protect the is protected by two fluid cushions that give spinal cord (PADS!!!) some protection for the brain against head traumas 151 152 Introduction 38  Protection of the CNS: The Central Nervous System Cerebrospinal fluid The cavities (ventricles) of the brain and spinal cord are SA S filled with cerebrospinal fluid (CSF). SSS B r a in The outer cavity is the superior sagittal sinus (SSS)(sits under dura mater) the inner cavity is the subarachnoid space (SAS) (space between arachnoid and pia mater) 153 154 Protection of the CNS: Cerebrospinal fluid CS F tap The fluid that provides the protection also - sample of CSF can be fills the spinal cord - it is called examined for signs of disease cerebrospinal fluid (CSF) (bacteria, virus, similar in composition to blood plasma inflammatory cells, abnormal products of degeneration as in Multiple sclerosis) medscape.com 155 156 Introduction 39  The Spinal Cord The spinal cord and peripheral nervous system (PNS) There are 31 pairs of spinal nerves. The spinal cord extends from S p ina l co r d the brain stem, to the pelvic Each nerve is a mixed region, ending before the end of nerve composed of sensory and motor the vertebral column fibers, packed together. Nerves enter or leave the spinal But they separate near cord in between the vertebrae the attachment of the nerve to the spinal cord. Spinal nerves 157 158 The link between the spinal cord and The link between the spinal cord and peripheral nervous system (PNS) peripheral nervous system (PNS): The interneurons also communicate (1) (2) Reflexes with one another along the length (3) (4) of the spinal cord An afferent sensory stimulus can For example, the “simple” withdrawal reflex be translated up or down the spinal response to a painful stimulus involves the cord by the interneurons contraction of several muscles, the relaxation of other muscles, and it may also involve responses that are initiated in the brain 159 160 Introduction 40  Upper vs. lower motor neuron damage C r it ica l Th ink ing Distinguishing between upper and lower motor neuron damage (UMN vs. LMN damage) 161 162 Upper vs. lower motor neuron damage Upper vs. lower motor neuron damage Myotatic (stretch) reflex: e.g. knee-jerk reflex Myotatic (stretch) reflex: e.g. knee-jerk reflex With LMN damage reflex will be: With UMN damage reflex will be: 1) exaggerated 1) exaggerated 2) normal 2) normal 3) diminished 3) diminished Loss of inhibitory inputs 163 164 Introduction 41  The Brain “The study of brain physiology is The basic “plan” is established embryonically. the process of the brain studying itself.” By the middle of the 4th week after conception, 3 distinct swellings are evident at the anterior end of the neural tube, which is going to form the brain. 165 166 The Brain The Brain During the 5 th week, these areas become modified to form These regions subsequently become greatly modified to 5 regions. form the general regions of the adult brain. 167 168 Introduction 42  169 170 171 172 Introduction 43  The Brain