Introduction to Nervous System 2024W1 PDF

Introduction to Nervous System Textbook Chapter: 6 Paige Jackson, MPT, MKIN, CSCS Learning Objectives Describe the functional organization of the nervous system Describe the structural and functional classification of neurons Identify and describe the function of neuroglial cell...

Introduction to Nervous System Textbook Chapter: 6 Paige Jackson, MPT, MKIN, CSCS Learning Objectives Describe the functional organization of the nervous system Describe the structural and functional classification of neurons Identify and describe the function of neuroglial cells Describe the structure, function, and formation of myelin Describe the regeneration of neurons after injury or interference Review the basic characteristics of the plasma membrane Explain the principles underlying the establishment of resting membrane potential and the concept of equilibrium potential Functions of Nervous System Sensing (sensory) Understanding (integration) Action (motor / response) Functional Organization of Nervous System Central Nervous System (CNS) Central nervous system Peripheral nervous system Brain Peripheral Nervous System (PNS) Somatic Sensory Afferent Division Visceral Sensory Special Sensory Subdivisions within PNS all have sensory and motor neurons 1. Somatic Somatic Motor Efferent Division Spinal Cord Autonomic Motor 2. Autonomic Sympathetic Parasympathetic Enteric 3. Enteric* Functional Organization of Nervous System Nervous System Cells Two main types of cells: 1. Neurons 2. Neuroglial Cells Neurons: anatomy Soma – cell body Dendrites Long projections from soma Receive information/signals Dendritic spines increase surface area Axon Long process from soma Relays information/signals out Axon hillock area of neuron that connects soma to axon Electrical signal initiated here Axon terminal End of each branch of the axon Synapses with another cell (communicates via neurotransmitters) Neuron Development Neurogenesis Neuroprogenitor cells Neuroblast Growth cone Neurons: structural classification Unipolar Bipolar Multipolar trigger zone Neurons: functional classification Neurons are classified into 3 groups based on their function: 1. Sensory / Afferent 2. Integrative / Interneurons 3. Motor / Efferent Nerve vs. Neuron Neuron is a single nerve cell Nerve Epineurium Perineurium Endoneurium àendoneurium vs neurolemma Nerve – the “funny bone” Funny bone Neuroglial Cells Neuroglial cells are the support cells of the nervous system. Functions: Neuroglia cells in CNS: astrocytes Astrocytes àblood-brain barrier Neuroglial cells in CNS: microglial Microglia Neuroglial cells in the CNS: ependymal cells Ependymal cells By Martin Hasselblatt MD (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY- SA 2.5-2.0-1.0 (https://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], via Wikimedia Commons Neuroglial cells in the CNS: oligodendrocytes Oligodendrocytes Neuroglial cells in the PNS: Schwann cells Schwann Cells Neuroglial cells in the PNS: satellite cells Satellite cells The picture can't be displayed. Neuroglia Location Function Type Forms blood brain barrier. Regulates composition of ECF in Astrocyte CNS CNS. Guides neuronal development in embryo. Phagocyte that protects CNS from pathogens (immune Microglia CNS functions). Engulfs bacteria/pathogens, debris, dead cells. Epithelial cells that line ventricles of brain and central canal. Ependymal cell CNS Regulates CSF production. Oligodendrocyte CNS Form myelin sheath in CNS. Schwann cell PNS Form myelin sheath in PNS. Protects and cushions neuron bodies of PNS. Helps maintain Satellite cell PNS proper extracellular environment. The picture can't be displayed.  Myelin Formed by neuroglial cells Oligodendrocytes (CNS) Schwann Cells (PNS) Made of lipids and proteins Provides electrical insulation nodes of Ranvier àMyelinated neurons transmit signals much faster than unmyelinated. Gray vs White Matter Myelin in the CNS vs. in the PNS Formation of Myelin Multiple Sclerosis Immune system attacks the myelin sheath and cells that produce it Axonal Injury & Regeneration – in PNS Axonal Injury & Regeneration Central Nervous System Injuries to spinal cord are often crushing rather than cutting. The picture can't be displayed. Basics of cell membrane review Transport across the cell membrane Substrates can cross a cell membrane in a few ways: Active methods Passive methods Na+-K+ Pump (Na+-K+ ATPase) Na+-K+ pump manages the balance of sodium and potassium inside and outside of the cell Pumps Na+ out of cell Pump K+ into cell Form of active transport (requires ATP) NaNa + + Extracellular fluid Extracellular fluid 33 Na 2K+ + Na+ expelled + gradient gradient expelled 2K Na+/K Na + ATPase +/K + ATPase P P Cytosol 3 3Na Na + + Cytosol ATP 2 K2+ K+ K+ K + ATP gradient PP imported imported gradient ADP 11 22 ADP 33 44 Na+-K+ Pump (Na+-K+ ATPase) Helps to establish and maintain an electrochemical gradient across the cell membrane Electrical gradient Chemical/concentration gradient Ion channels: leak channels - passive Ion channels (or leak channels) allow for movement of small, charged particles across the cell membrane. Integral membrane proteins Selective Cell membrane potential (VM) 0 mV –70 mV +70 mV 0 mV –70 mV +70 mV Extracellular Reference Recording fluid electrode microelectrode Extracellular Reference Recording fluid electrode microelectrode Cytosol Cytosol (b) Measurement of the resting membrane potential of a neuron (b) Measurement of the resting membrane potential of a neuron Membrane potential (VM) Separation of electrical charges across the membrane The picture can't be displayed. All cells have resting membrane potentials A- Resting membrane potential Extracellular fluid Plasma membrane Cytosol Extracellular fluid Plasma membrane Cytosol Extracellular Extracellular fluid fluid Chloride ion Chloride ion Sodium ion Sodium ion Na+/K+ ATPase K+ leak channel Na+ leak channel Na+/K+ ATPase K+ leak channel Na+ leak channel 3 Na+ 3 Na+ Resting Resting membrane membrane potential potential Cytosol Cytosol ATP 2 K+ ATP 2 K+ Phosphate ion Phosphate ion ADP ADP Protein Protein Potassium ion Potassium ion Membrane potential (VM) Membrane potential depends on: Concentration gradients of K+ and Na+ High [Na+] Relative permeability of K+ and Na+ Low [K+] Extracellular At rest, the cell membrane is: More permeable to K+ Less permeable to Na+ Low [Na+] Intracellular High [K+] Summary Central vs. peripheral nervous system Nerve cells (neurons) – structure and classifications Where nerve impulses are initiated Direction of nerve impulse conduction Glial cells (CNS and PNS) and their functions Myelin in the CNS vs. PNS Neurophysiology: fundamental concepts Interaction of passive and active factors that establish resting membrane potential Neuronal Signaling and Communication Textbook Chapter: 6 Paige Jackson, MPT, MKIN, CSCS Learning Objectives 1. Define and explain the mechanisms underlying action potentials and their propagation 2. Describe the events at a chemical synapse 3. Explain the concepts of synaptic integration (spatial and temporal summation) 4. Describe the action of some neurotransmitters and their receptor action, and whether they cause EPSPs or IPSPs 5. Define and explain the mechanisms underlying graded potentials Membrane Potential – definitions review Resting membrane potential: the electrical potential difference across the cell membrane of an unstimulated cell (i.e. a cell at “rest”) Polarization: Depolarization: Repolarization: Hyperpolarization: Overshoot: Permeability: the ability of a substance or barrier to allow for molecules to pass through it Equilibrium potential: the membrane potential when the concentration and electrical potential of an ion are equal and opposite in magnitude Current: when charged particles flow in a new direction Definitions cont’d… Membrane potential can change … depolarization repolarization hyperpolarization Action Potentials An action potential is a rapid depolarization of the membrane potential, followed quickly by repolarization and re- establishment of the resting membrane potential. Action potential has 3 phases: Rising Falling After-hyperpolarization Action potential: all-or-none phenomenon -70 mV some stimulus Action potential: all-or-none phenomenon -70 mV some stimulus Action potential: Rising Phase +30 mV peaks at +30 mV Na+ PEN ted cha age-ga ls O nne t vol -55 mV critical threshold -70 mV Action potential: Falling Phase meanwhile … Voltage-gated K+ channels also triggered OPEN at -55 mV (but +30 mV more slowly) voltage-g channels ated K+ OPEN -70 mV Action potential: After Hyperpolarization voltage-gated K+ channels also +30 mV slow to close all closed K+ Voltage-gated channels still -70 mV closing … Na+ channels: Resting State Extracellular fluid Plasma membrane Cytosol At resting membrane potential, the Na+ channel activation gate is closed. mV Time Na+ channels: Activation A depolarizing stimulus arrives at the channel – Na+ activation gate opens. Na+ mV Time K+ Na+ channels: Inactivation mV Time Inactivation gate closes Na+ and Na+ entry stops. K+ channel meanwhile has opened. K+ Na+ channels: Resetting Na+ K+ During repolarization, the activation and mV inactivation gates of the voltage-gated Na+ channel reset to their original positions Time Refractory Period larger than normal stimulus is second action potential required to trigger another action cannot be triggered potential absolute relative refractory period refractory period action potentials will action potentials CAN fire NOT fire Refractory Period Membrane potential (mV) Stimulus strength Absolute Relative refractory period refractory period Action potentials do not lose strength with distance Conduction of action potentials  direction of propagation X why doesn’t the action potential propagate backward? refractory period prevents firing of another AP Factors influencing speed of action potentials Two main influences on conduction speed: 1. Axon diameter 2. Myelin (Insulation) Factors influencing conduction speed of action potentials axon diameter ­ diameter à ¯ resistance Myelin: Saltatory Conduction myelinated sections - current flows quickly with minimal leak nodes of Ranvier - depolarization opens Na+ channels and AP is replenished to node ‘leaping’ from node high concentration of Na+ fewer ion channels and K+ channels Factors influencing the speed of conduction diameter myelinated? fastest A fibers 5-20 μm yes B fibers 2-3 μm yes C fibers 0.5-1.5 μm no slowest Graded Potentials Graded potential is a small, local change in membrane potential. Decremental signal strength Graded potentials vary in size the size (amplitude/duration) of a graded/synaptic potential is related to the size of the stimulus Where do graded potentials occur? motor end plates dendrites of interneurons dendrites of motorneurons sensory receptors sensory transduction – dendritic ends of sensory neurons (receptor membrane) To CNS – receptor cells Receptor Afferent Stimulus membrane neuron To CNS Receptor Vesicle containing cell neurotransmitter Cell-to-cell Communication: the Synapse Synapse is the junction between neurons (or between neuron and another cell) neurons can connect with: electrical synapses (gap junctions) chemical synapses Synapses A synapse has three parts: 1. pre-synaptic neuron 2. synaptic cleft 3. post-synaptic cell Convergence: Divergence: Chemical vs. Electrical Synapses Chemical synapses Electrical synapses Chemical Synapse events 1. Action potential arrives at synaptic bulb 2. Voltage-gated Ca2+ channels open 3. Ca2+ enters synaptic bulb and triggers exocytosis of neurotransmitters from synaptic vesicles into the synaptic cleft 4. Neurotransmitters diffuse across the cleft and attach to receptors on postsynaptic membrane 5. Ion channels on postsynaptic membrane open (neurotransmitters removed from cleft) 6. Postsynaptic potential generated Postsynaptic Activation Ionotropic receptors a Metabotropic receptors Synaptic activation is one-way Neurotransmitter is released and diffuses into the cleft Neurotransmitter Neurotransmitter binds removed from to postsynaptic receptors synaptic cleft à post-synaptic potential (PSP Neurotransmitter Removal Neurotransmitters are removed from the synaptic cleft in a variety of ways: 1. 2. 3. 4. Excitatory Post Synaptic Potentials (EPSP) Inhibitory Post Synaptic Potentials (IPSP) Excitatory and inhibitory synapses EPSPs Depolarizing/excitatory activity IPSPs Hyperpolarizing/inhibitory activity Synaptic Integration Spatial summation of post-synaptic potentials is one way threshold is achieved. Synaptic Integration Temporal summation also contributes to reaching threshold potential. Integration of Graded Potentials/Synaptic Integration Integration of Graded Potentials: https://www.youtube.com/watch?v=ZnC8v9Dl_O4 Drug and Disease Modification of Synaptic Transmission Some Neurotransmitters Acetylcholine (ACh) Neurons that release ACh are called cholinergic neurons Catecholamines Group of neurotransmitters that contain specific molecular structure Dopamine: Norepinephrine: Epinephrine: Serotonin Excitatory pathways Inhibitory pathways Glutamate Gamma-aminobutyric acid (GABA): Resetting the Na+/K+ balance after an AP The Na+-K+ ATPase channels continuously work to maintain ‘proper’ or resting levels of sodium and potassium on either side of the cell membrane After an AP passes through, there is more Na+ inside at the cell membrane and more K+ outside at the cell membrane than there was prior to the AP passing These active transport pumps move Na+ and K+ against the concentration gradient and back to their initial resting state locations (i.e. Na+ outside and K+ inside) Na + Extracellular fluid gradient 3 Na+ expelled 2K+ Na+/K+ ATPase P 3 Na+ Cytosol K+ ATP 2 K+ gradient ADP P imported 1 2 3 4 Resetting the Na+/K+ balance after an AP Sodium enters the protein, ATP binds at a specific binding site on the protein that hydrolyzes it with ATPase into its components of ADP + Pi + Energy The energy causes the protein to change shape and ‘open the gate’ on the extracellular side of the membrane, thus releasing the Na+ back out Potassium then enters the protein channel and triggers it to rest back to it’s original position, thereby opening the gate on the inside of the cell, where the potassium can return to the intracellular fluid Initial concentration gradient is re-established and ready for next AP Na+ Extracellular fluid These pumps can gradient Na+/K+ ATPase 3 Na+ expelled 2K+ catch up with the [Na] because the voltage- gated Na ion channels have closed so no new sodium is coming in P 3 Na+ Cytosol (peak of AP) K+ ATP P 2 K+ gradient 1 2 ADP 3 4 imported Summarized steps of AP: 1. Adequate summation of graded potentials at axon hillock causes the membrane potential to shift from -70mV to the critical threshold of -55mV 2. At -55mV voltage-gated sodium channels open and positively-charged sodium floods into the cell causing a rapid depolarization of the cell membrane 3. Voltage-gated potassium channels are also triggered open, but they do so more slowly. They fully open by the time the membrane potential reaches +30mV 4. The escape of positively-charged potassium from inside the cell causes a rapid repolarization of the cell membrane 1. At the same time, the inactivation gates in the sodium channels have closed, blocking more sodium from crossing into the cell 5. The potassium channels are slow to close, and the cell membrane is more permeable to potassium (aka lots of potassium can leave the cell) so the cell membrane is hyperpolarized momentarily à during this time a stronger signal is required for another action potential to fire 1. Sodium channels are reset by this time, ready for the next AP 6. Active Na+-K+ ATPase pumps work to reset the initial, resting concentrations of Na+ and K+ on the outside and inside of the cell, respectively.  Na+ Extracellular fluid 2K+ 3 Na+ expelled gradient Na+/K+ ATPase P Cytosol 3 Na+ K+ ATP 2 K+ 1 2 ADP 3 P 4 imported gradien t Central Nervous System & Sub-cortical Areas Textbook Chapter: 10 Paige Jackson, MPT, MKIN, CSCS Nerve vs Neuron (review) Nerve is a group of axons plus connective tissue wrappings and blood vessels. Neurons are the functional unit/cell of the nervous system. Pathways/tracts: àcommissures: The Central Nervous System The central nervous system is comprised of the brain and the spinal cord. Brain has 3 major divisions: 1. Forebrain Cerebrum Diencephalon 2. Midbrain 3. Hindbrain Pons Medulla oblongata Cerebellum Cerebrum The cerebrum is the largest part of the brain. gyri (or gyrus, sing.): sulci (sulcus, sing.) fissures Cerebrum The cerebrum is divided into four lobes: 1. Frontal 2. Parietal 3. Occipital 4. Temporal  central sulcus precentral postcentral gyrus gyrus [ [ parieto-occipital sulcus Lateral cerebral sulcus  muscles, movement control sensation vision ‘executive’ functions Insula - taste, smell hearing, memory acquisition different brain regions perform different functions Cerebral Cortex - function àfunctions of cortex can be mapped primary motor area primary somatosensory area Primary areas: mediate the actual function Secondary areas: apply meaning (also called association areas) primary visual area primary gustatory area primary auditory area primary olfactory area Cerebrum Primary Somatosensory Areas primary somatosensory area somatosensory association area Somatosensory Association Area Cerebrum Primary Motor Area primary motor area motor association area (premotor cortex) Motor Association Area (premotor cortex) Cerebrum Primary Auditory Area primary visual area Auditory Association Area visual association area primary auditory area Primary Visual Area auditory association area Visual Association Area Cerebrum Primary Olfactory Area Secondary Olfactory Area Primary Gustatory Area primary gustatory area primary olfactory area Secondary Gustatory Area Cerebrum Prefrontal Cortex (prefrontal association area) prefrontal association area  old/young lady identical visual input but 2 different perceptions Control of Movement in the Cerebrum PRIMARY MOTOR AREA motor execution PREMOTOR AREA motor planning (association area) Homunculus Homunculus https://learnsomatics.ie/how-your-brain-sees-your-body/ Basal Nuclei Basal nuclei are subcortical structures. Main functions: Basal Nuclei – understanding function Parkinson Disease Hypokinetic movement disorder Treatment: L-Dopa Basal Nuclei – understanding function Huntington’s Disease Hyperkinetic movement disorder Limbic System The limbic system is a functional system. Comprised of: Nuclei in different parts of the brain and the tracts that connect them Hippocampus Amygdala Thalamus Hypothalamus Main Functions: Thalamus (part of diencephalon) Thalamus is a cluster of nuclei that sends and receives information to/from the cortex Flow of info: Diencephalon Hypothalamus (part of diencephalon) Hypothalamus is the master command centre for neural and endocrine coordination. Connects to the pituitary gland Brainstem Brainstem consists of four parts: 1. Medulla oblongata 2. Pons Midbrain 3. Midbrain 4. Reticular formation* General functions of brainstem: Brainstem: Medulla (oblongata) Medulla Control centres found in the medulla: Cardiovascular centres Respiratory rhythmicity centres Reflex centre Brainstem: the pons Pons Brainstem: midbrain Midbrain Brainstem: Reticular Formation Reticular formation is a network of cells extending through the brainstem. Reticular Activating System Reticular activating system is an aspect of the reticular formation. When we are awake: When we are asleep: Damage leads to prolonged coma. Cerebellum Cerebellum Key Functions: Balance control Movement Coordination Damage to cerebellum Ataxia: Dysmetria Dysdiadochokinesia Spinal Cord Spinal cord extends from the brain and relays signals between the brain and the PNS. 31 pairs of nerves, from each segment Divided into five sections: Cervical (8 segments) Thoracic (12 segments) Lumbar (5 segments) Sacral (5 segments) Coccygeal (1 segment) Spinal Cord Conus medullaris = Filum terminale = Cauda equina = http://www.nlm.nih.gov/medlineplus/ency/imagepages/19504.htm Spinal Cord Contains white matter and gray matter Spinal nerves Posterior ramus Anterior ramus POSTERIOR ANTERIOR Sensory (ascending) tracts Motor (descending) tracts Dermatomes & Myotomes Dermatomes = Myotomes = Spinal Cord Injuries C1 Cervical segment C7 T1 Thoracic segment T8 T9 Lumbar segment T11 T12 Sacral segment L2  Protecting the Central Nervous System Textbook Chapter: 6 Paige Jackson, MPT, MKIN, CSCS © Pia McDonell of McDonell Media Protecting the Central Nervous System 3 main ways CNS is protected: 1. Meninges 2. Cerebrospinal Fluid 3. Blood Brain Barrier other ways… Meninges Meninges Three Layers: 1. Dura mater 2. Arachnoid Mater 3. Pia Mater àsubarachnoid space Meninges Dura mater Arachnoid mater Pia mater Meninges at the spinal cord Meningeal Extensions falx cerebri tentorium cerebelli Falx cerebri Falx cerebelli Tentorium cerebelli falx cerebelli Meningitis Meningitis Head Bleeds Head Bleeds Epidural hematoma Subdural hematoma Subarachnoid hemorrhage Cerebrospinal Fluid (CSF) Cerebrospinal fluid (CSF) àchoroid plexus Functions: CSF Flow Superior sagittal sinus (CSF drainage) LATERAL VENTRICLES interventricular foramina of Monro cerebral aqueduct THIRD VENTRICLE SUBARACHNOID SPACE (surrounding brain) lateral aperture (to subarachnoid FOURTH VENTRICLE space) CENTRAL CANAL median aperture (to central canal) SUBARACHNOID SPACE (surrounding spinal cord) (c) Frontal section of brain and spinal cord CSF Drainage Superior sagittal sinus Frontal plane Skin Parietal bone of Periosteal layer cranium CRANIAL MENINGES Meningeal layer Arachnoid villi Dura mater Subarachnoid space Arachnoid mater Arachnoid villus Pia mater Cerebral cortex Falx cerebri (a) Anterior view of frontal section through skull showing the cranial meninges Spinal taps / Lumbar punctures  http://www.nlm.nih.gov/medlineplus/ency/presentations/100123_2.htm Hydrocephalus Hydrocephalus is a condition where CSF accumulates. https://njpediatricneurosurgery.com/services-specialties/hydrocephalus-center/ Blood Brain Barrier Functions: Blood Brain Barrier tight junctions endothelium (blood vessel wall) astrocyte It is the features of the microvasculature in the brain that creates the BBB à is it ‘leaky’ anywhere? http://commons.wikimedia.org/wiki/File:Astrocyte_endothel_interaction_01.png  Peripheral Nervous System Sensory Physiology (General) & Spinal Reflexes Chapter 7.1,7.2,7.5 Peripheral Nervous System The peripheral nervous system is the nervous tissue outside of the brain and the spinal cord. https://step1.medbullets.com/neurology/113074/muscles-innervated-by-cranial-nerves Peripheral Nervous System It can be divided into: Afferent pathways Somatic sensory Visceral sensory Special sensory Efferent pathways Somatic motor Autonomic motor Sensory Receptors Sensory receptors detect information from our internal and external environments. Sensory Receptors Categorized by: Source of stimulus Exteroceptors – Proprioceptors – Enteroceptors – Mode of detection Chemoreceptors Thermoreceptors Photoreceptors Mechanoreceptors Nociceptors General vs Special Sensory Receptors General senses: Special Senses: Sensory Transduction: receptor potentials Sensory transduction is the translation of a stimulus into a potential (electrical signal). Sensory Transduction Magnitude of receptor potential determines the frequency of action potentials, but not the amplitude. Frequency = Factors that affect magnitude of receptor potential: Sensory Receptors Receptors display adaptation. Fast adapting receptors aka phasic receptors Slow adapting receptors aka tonic receptors The Sensory Unit Central nervous system Skin sensory unit receptive field Flow of information Sensory Coding Sensory coding https://www.childoftheredwoods.com/articles/blindfold-activity Sensory Coding: type Type/modality Sensory Coding: location Overlapping receptive fields Lateral inhibition Convergence Action potentials in postsynaptic cell Postsynaptic cell Axons of afferent neurons A B C Action potentials in afferent neuron Sensory Coding: intensity The intensity of sensory information is determined by frequency and population Frequency coding Population coding General Senses: touch Mechanoreceptors in the skin allow for the sensation of touch and pressure. General senses: touch Touch & Pressure Receptors (6): 1. Meissner’s corpuscles 2. Merkel cells 3. Pacinian corpuscles 4. Ruffini corpuscles General senses: touch 5. Free nerve endings 6. Root hair plexuses General Senses: pain Stimulation of nociceptors activated by real or potential tissue damage Myelinated type A fibres Unmyelinated type C fibres Referred pain? General senses: temperature Thermoreceptors respond to heat or cold. General senses: proprioception Proprioception is our awareness or perception of our body’s position and movement. General senses: proprioception Muscle spindle stretch receptors are located in skeletal muscles. General Senses: proprioception Golgi tendon organs are located in tendons of muscles. Muscle and tendon receptors: Spinal reflexes Spinal reflexes are automatic motor responses to a sensory stimulus. Stretch Reflex Stimulus: Receptor: Effects: GTO Reflex: tension-monitoring system Stimulus: Receptor: Effect: Muscle Cramps Are muscle cramps due to reduced GTO inhibition? Calf cramp while swimming Muscle cramps Passive stretching to treat cramps? Flexor (withdrawal) and crossed extensor reflex To brain Stimulus: Afferent nerve fiber from Receptor: nociceptor Effects: Ipsilateral extensor muscle Contralateral relaxes flexor muscle relaxes Ipsilateral Contralateral flexor muscle extensor muscle contracts contracts Begin Nociceptor  Peripheral Nervous System: Autonomic Nervous System Chapter 6.18 https://www.christopherreeve.org/todays-care/living-with-paralysis/health/secondary-conditions/autonomic-dysreflexia/ Autonomic Nervous System The autonomic nervous system is part of the PNS. Divided into three components: 1. 2. 3. Somatic Nervous System vs Autonomic Nervous System Somatic vs Autonomic Nervous System Somatic (SNS) - motor Autonomic – motor Sympathetic Division: fight or flight The sympathetic division of the ANS readies our bodies to react to stress or a threat. Response: Stimuli Parasympathetic Division: rest & digest The parasympathetic division of the ANS facilitates rest and recovery. Response Stimuli Dual Innervation Sympathetic Response Parasympathetic Response Pupils Dilation Constriction Digestion Inhibited Activated Metabolism Catabolism Anabolism Cardiovascular (HR & BP) Increased Decreased Muscle Tone Increased Decreased Respiration Increased Decreased Temp & Sweating Increased Decreased Urinary Function Decreased Increased Alertness Increased Decreased Sympathetic Nervous System Preganglionic neurons superior cervical ganglion sympathetic trunk middle cervical ganglion inferior cervical ganglion sympathetic chain cervical ganglia T1-L2 Sympathetic chain/trunk Sympathetic Cervical Ganglia Superior cervical ganglion Middle cervical ganglion Inferior cervical ganglion àproject to structures in the head and neck, as well as the heart & lungs Parasympathetic: Craniosacral division ciliary ganglion Preganglionic neurons pterygopalatine ganglion submandibular CN X ganglion otic ganglion Ganglia are located near or on the wall of the target organs. 4 pairs in the head 3 pairs in the sacrum Parasympathetic ganglia The 4 pairs in the head are closely connected to certain cranial nerves. Ciliary ganglion Pterygopalatine ganglion Submandibular ganglion Otic ganglion Parasympathetic: CN X – vagus nerve Vagus nerve (CN X) makes up 75% of parasympathetic NS. Autonomic vs Somatic Nervous System: activation Somatic NS acts on skeletal muscle cells with acetylcholine. Parasympathetic neurons release acetylcholine. Autonomic vs. Somatic Nervous System: activation Preganglionic neurons release acetylcholine in the sympathetic nervous system. Postganglionic neurons in sympathetic NS release norepinephrine. Autonomic vs Somatic NS: Activation Sympathetic neurons also synapse with the adrenal medulla. Endocrine response in sympathetic system Epinephrine released from the adrenal medulla causes: Neuroplasticity: a quick look  Frontal plane through recall: homunculus postcentral gyrus Hip Trunk Nec d Hea ulder Shorm A Fore t Elbo rm k W and Leg ris H Li a Foot w Ri ttle Toes M ng i In ddle Genitals de Th x um Eye b No se Fac e Upp er li p Lips Low er li p Teeth , gum s, and jaw n g ue To ryn x inal Pha abdom a Intr (a) Frontal section of primary somatosensory area in right cerebral hemisphere plasticity following injury L face R face L hand R upper arm L upper arm (R arm amputated below elbow) Ramachandran, Plasticity and functional recovery in neurology. Clin Med 2005 Ramachandran & Rogers-Ramachandran. Phantom limbs and neural plasticity. Arch Neurol 2000 plasticity with training Einstein’s brain the ‘knob’ or ‘Omega sign’ – 𝛀 indicative of motor cortical representation of the hand Falk et al. Brain 2013 Corey Rich Productions/Novus Select https://www.si.com/edge/2017/05/16/the-push-book-rock-climber-tommy-caldwell-finger free study tip: exercise promotes learning Break: or: exercise break OR non-exercise break OR no break mind-wandering (MW) “Which of the following responses best characterizes your questionnaire: mental state just before this screen appeared?” (1) on task (2) intentionally mind wandering (3) unintentionally mind wandering free study tip: exercise promotes learning “Which of the following responses best characterizes your mental state just before this screen appeared?” (1) on task (2) intentionally mind wandering (3) unintentionally mind wandering Test score 48-hrs later compared to immediately after Midterm info: Friday Nov 8 12pm 45 minutes MC/Short written Same general rules as before (re: no hats, bags front, no smart devices, etc.) Bring pencil and student ID