Nervous System I PDF Notes - Week 9

Nervous System I November 13, 2023 8:32 AM Super Seven List – Nervous System Part 1: Overview (15 MCQs in all of Neuro I & II) 1. Organization of the nervous system including peripheral nervous system both motor and sensory 2. Neuron, neuroglia and synapse anatomy 3. CSF: function, composition and...

Nervous System I November 13, 2023 8:32 AM Super Seven List – Nervous System Part 1: Overview (15 MCQs in all of Neuro I & II) 1. Organization of the nervous system including peripheral nervous system both motor and sensory 2. Neuron, neuroglia and synapse anatomy 3. CSF: function, composition and circulation 4. CNS structures and basic functions such as cerebrum, diencephalon, brainstem, and cerebellum 5. Organization of spinal cord and major tracts 6. Somatosensory organization including types of sensory receptors 7. Autonomic nervous system - FYI: ○ ○ ○ ○ ○ ○ Mass of 2kg, smallest system 2-3% of total body weight, but requires 20% of O2/glucose despite being almost 75% water Fits in human skull Contains 100 billion neurons and 10-50 times that of glial cells 100 trillion synapses Each neuron can send up to 1000 nerve impulses per second to tens of thousands of other cells at speeds of up to 430 km/hr ○ Potential brain capacity estimated 20 million books(filling 800km bookshelf) Week 9 Page 1 2 major divisions: CNS & PNS CNS: brain and spinal cord PNS: all other nervous tissue Brain and spinal cord have CSF that circulate it to protect it, as well as meninges for protection CNs and Spinal nerves are part of peripheral NS, but start in CNS-->denoted by roman numerals, have sensory and motor fibers - Ganglia- small masses of nervous tissue in peripheral nervous system, to support cell bodies of neurons for optimal envt for function - - Take in stimulus via sensory receptor (ex. There is bear, smell and see), then integration of information in CNS in order to develop a response - Ex. Children may not have this integration response to avoid running on road Week 9 Page 2 - Types of neurons, responsible for sensing, integrating info, and effecting a response - Neuroglia - ensures the optimal envt is available for neurons to function well Classic structure of neuron: - Info comes into cell via dendrites - Soma ○ cell body of neuron, with nucleus, has nissl bodies (specialized RER) ○ if have lots of RER, will make protein ○ have lots of neurofilaments that helps transportation down axon - Most neurons in CNS are post-mitotic--don't reproduce. Ex. With stroke pt, if destroy neurons in one area, another area may repurpose their neurons to take on those "lost" tasks - Axon hillock Week 9 Page 3 - Axon hillock ○ at beginning of axon, integrating center, where you have to meet a threshold - Axon ○ area from cell body to synaptic end ○ transports neurotransmitters to the end - Nodes of Ranvier: ○ PNS neuron in above image ex. Swann cells--wraps myelin sheath around axon to protect and helps with impulses to travel faster ○ Myelin sheath gap - help with quick electrical changes - Synaptic end bulb - meet up with synaptic cleft - Pre and post synaptic neuron - In Schwann cells, have myelin sheath ○ Wraps around axon, up to 150 times ○ It's double layered, thus can get up to 300 layers ○ Insulates electrical activity Week 9 Page 4 - Both PNS and CNS have myelin sheaths - But the cells that deliver the sheaths are different - Swann cells for PNS, and oligodendrocytes in CNS - Ex. With newborn, we have to protect head ○ children learning to walk has a high risk of falling, difficulty coordinating, and with age, they develop better coordination ○ b/c of increasing myelination around the axons, they develop more coordinated and faster responses. ○ Children under 2yo should be given homogenize milk, b/c component of milk promotes myelinization in CNS and PNS. - Antegrade - takes info from cell body to synapse Retrograde info - from synapse to cell body Synapse doesn't make the NTs, it comes from cell body Cell body makes NTs and use microtubules to deliver NTs through axon using motor proteins Week 9 Page 5 VIDEO: - MTs constantly being formed and unformed, carrying the NTs - Ex. Alzheimer's: amyloid plaques and tau phosphorylation--the tau stabilizes the MTs, and if stabilization process is dysfunctional thus the NTs won't be able to get from cell body to synapse, thus losing connections, and over time atrophy of cerebrum and memory issues - Retrograde transport: taking degraded products from synaptic cleft back into cell to manipulate and remake NTs. - Some of the viruses like to be stored in nerve cells - ex. Shingles - patient has to have prior chicken pox infection, and virus is stored in cell. With reactivation and when exposed to a trigger, (common in older population, and more severe), it is housed in the ganglia, which will present on a single dermatome - Ex. Cold sores - HSV - come back in the same area, tingling, and over time the clusters can grow and implicate other nervous tissue. Activation of that virus, usually brought on by stress. This is retrograde transport - Lifespan of a neuron: an avg human lifespan - Structure looking at number of processes --looking at number of processes - Can classify according to function Week 9 Page 6 - Multipolar - lots of processes coming to cell body via dendrites - Bipolar - usually associated with special senses - Unipolar Week 9 Page 7 - Multipolar are the most numerous in body, major type in CNS - Bipolar found in special organs ex. Retina - Unipolar - associated with ganglia and clusters of tissues, associated with PNS Week 9 Page 8 - Can be sensory, motor, both - Multipolar: ○ CNS interneurons ○ CNS motor efferent neurons ○ neurons need to quickly integrate information, mostly motor, but some sensory - Bipolar - most often sensory ○ Located in special sensory organs? - Unipolar - takes info from sensory envt ○ usually sensory afferent fibers to CNS Week 9 Page 9 - See the complexity Week 9 Page 10 - 4 types of neuroglia in CNS & 2 in PNS - CNS: ○ Astrocytes ○ Most abundant ○ Star-shaped ○ Associated with capillaries ○ Prevents substances from crossing BBB ○ Picks up NTs and takes nutrients to be recycled ○ Microglial cells ○ Similar to macrophages - goes around and takes up debris and dysfunctional neurons ○ Smaller than astrocytes ○ Tries to play role in preventing infections in brain ○ Ependymal cells ○ Arranged in single layer ○ Line the ventricles in brain--where CSF is made ○ Have cilia at top to promote movement of brain ○ Oligodendrocytes: ○ Form myelin sheaths ○ Protect axon ○ Helps impulses move faster - PNS: ○ Swann cells: ○ Lays down myelin around axon to protect it ○ Satellite cells: ○ Around in ganglion, around cell body to support it and ensure sufficient nutrients Week 9 Page 11 - oligo and swann cells do same thing, but in diff sites (CNS vs PNS) - Sensory input (afferent neurons) from external stimuli towards CNS - Motor output - taking info from CNS, down to body wherever it needs to go ○ Somatic nervous system - skeletal, voluntary, thus can control that ○ ANS ○ sympathetic/parasympathetic ○ Enteric NS - in GI tract  Ex. Secretion of glands, SM etc Week 9 Page 12 - - Everything on R side (special senses), we will not get to in this course Week 9 Page 13 1. Start with a receptor in joint, muscle, free nerve ending in skin ○ Unique receptors, where there are types of information that is transmitted to CNS 2. Travels through circuit and is processed via these ascending pathways to reticular formation and thalamus ○ Major area of integration for sensory information = thalamus 3. Info sent to CNS, and processes info in cortical sensory centers, and it then responds to that information, and causes an effect Week 9 Page 14 - A depiction of the real estate that these body areas show on brain Large area of sensory receptors of face We have a wide range of sensations Information on L side of brain is displayed on the R side of body = contralateral Neuroplasticity of brain - we have a set area in brain that gives us information re: motor movement ○ Ex. If lose sight as an adult, there is real estate for visual sensation, and if can no longer see, no information is coming in, and in the brain, these areas that are not being used atrophy, and the other areas take over that dead space ○ However, we can expand physical sensation to read brail ○ However, we can expand auditory sensation to hear external environment better ○ Ex. Fine motor movements for precise artistic work, requires more specificity, and will expand this area - Homunculus is not same for every person, but unique to what individuals use and do Week 9 Page 15 - Each sensory receptor gives a different type of information ○ Mechano- detects mechanical pressure ex. Touch, push down, vibration, stretch, itch ○ Thermo - info re: temperature, cold receptors more superficial ○ Chemo - in nose for smell, taste ○ Photo- work in retina in eyes ** wont talk about this ○ Nociceptors - receptors for pain, all of these receptors with enough of a noxious stimuli can become a pain receptor….thus mechano receptors can become pain receptors if enough pressure added, same with thermo receptors, hot enough and will turn into pain - Exteroceptors - superficial areas - Interoceptors - visceral organs, blood vessels, muscles - Proprioceptors - around muscles, tendons, joints - Structural complexity ○ Simple - most general sensory info is simple ○ Complex - associated with special senses, thus don’t need to know** Week 9 Page 16 - Don't need to know all these types of receptors - Know the terminology ○ What the exterior/interior receptors are - Ex. Hair follicle Week 9 Page 17 - A variety of simple receptors types on skin to give us information Week 9 Page 18 - Have to have receptors to give us information, but also need receptor field - Have different areas that combine and converge the information and send signal to brain - Different parts of body have more discrimination and able to locate where specific information is coming from, but back won't have has much discriminating information--more vague ○ Large receptive fields = no two-point discrimination ○ Small receptive fields = two-point discrimination - Ex. Monofilament test for diabetics - can feel 2 diff points on fingers, but on back there is a larger receptor field that covers that information, so not as sensitive, but face and extremities will have smaller receptor fields Week 9 Page 19 - SNS: ○ E situations = fight or flight: Embarrassments, emergency ○ Activation - profound, widespread ○ Responses: pupils dilate, liver releases glucose to ensure enough sugar source to deal with situation - PNS ○ Rest and digest ○ Role in restorative component ○ SLUDD (inc salivation, lacrimation, urination, digestion, defecation) increases ○ 3 dec responses: HR, airway diameter (bronchoconstriction), pupil - Don't want overdrive of SNS - leads to complications - Want PNS and SNS to be balanced - Started in CNS and then move to PNS - Have pre ganglionic cell--> autonomic ganglion --> postganglionic cell --> target tissue Week 9 Page 20 - PNS: ○ Ganglion cells close to target organ ○ So long pre-ganglionic neuron, and short postganglionic cells - In SNS opposite: ○ ganglions close to pre-ganglionic neuron - PNS - cranio- sacral - SNS - thoracolumbar Week 9 Page 21 - Both pathways have ANS - SNS: ○ Preganglion neuron releases Ach as NT, which binds to cholinergic-R ○ 2 types of cholinergic R  Nicotinic  Muscarinic ○ Post ganglionic neuron, releases NE (adrenergic), which binds to adrenergic -R ex. Alpha and beta receptors - PNS ○ Preganglionic neurons release Ach-->binds to nicotinic R (cholinergic) ○ Post ganglionic neurons release Ach--> binds to muscarinic R (cholinergic) Week 9 Page 22 - SNS releases lots of Epi Week 9 Page 23 - With SNS and PNS, there is dual innervation-- body have majority of information has innervation - SNS will cause inc in responses ○ Ex. Lung bronchodilation - PNS will decrease the responses ○ Lung bronchoconstriction - Kidney doesn't have dual innervation, has SNS that releases renin, but not PNS - Adrenal medulla, only SNS innervation, no PNS - Ex. a-bungarotoxin Toxin blocks nicotinic Ach R --blocks the preganglionic SNS response The somatic response, using Ach R, not able to move muscles The PNS - preganglionic uses Ach-R --> toxin binds to all areas--leads to paralysis, resp failure, death Week 9 Page 24 - SNS and PNS have opposing effects on target areas - Cerebrum - brain matter on L controls R body, contralateral information Week 9 Page 25 - Cerebrum - brain matter on L controls R body, contralateral information - Basal ganglia - deep within hemispheres, coordinates autonomic movement and muscle tone - Ex. Drug that gives you EPS side effects = haldol & EPS ○ EPS - uncontrolled skeletal muscle movement, non-purposeful motor movement - Limbic systems - system associated with emotion, feelings - Left hemisphere - R hemisphere - Most people are dominant to one site - Geniuses utilize both sides of brain really well; able to be creative and make logical changes Week 9 Page 26 - Frontal ○ Skilled movement ○ executive functioning ○ personality ○ Motor cortex ○ Ex. Frontal lobe injury - disinhibition, personality changes - Parietal ○ Sensory cortex - Occipital ○ Visual - Temporal ○ Memory ○ auditory ○ Wernicke's? - Cerebellum ○ Balance ○ Equilibrium ○ coordination Week 9 Page 27 - Skull - protects brain - Meninges - support brain ○ Dura - thick ○ Arachnoid - spider-like projections, vascular area ○ Pia - innermost layer that lines the cerebrum through gyri and grooves - CSF - we're constantly producing it and need to be equally reabsorbing ○ Problems if build up or not enough - BBB ○ Specific to what goes in ○ Protective but also problem for medication to enter and take effect in brain Week 9 Page 28 ** know this for NCLEX - Some Say Marry Money But My Brother Says Big Brains Matter More… - **know for NCLEX Week 9 Page 29 - Thalamus - relaying incoming sensory impulses - Hypothalamus - critical for homeostasis ○ ANS functions, water balance via ADH, stress response - Pituitary ○ Posterior - oxytocin and ADH ○ Anterior - several endocrine hormones - Pineal gland ○ Releases melatonin Week 9 Page 30 - Midbrain - relaying information Pons- fine tune breathing Medulla oblongata - resp center, CVS center RAS - arousal, sleep regulation - helps to regulate sleep cycle ○ Relay sensory info to cerebrum through thalamus ○ Continuous sensory stimuli keeps cerebrum aroused and alert Week 9 Page 31 - SC starts in foramen magnum, all the way to L1/L2 - White matter is usually myelinated - Grey matter- unmyelinated - Functions ○ White matter ○ Grey matter - interconnections and integrates excitatory post synaptic potentials and inhibitory post-synaptic potentias, and integrates this ○ Spinal nerves come off spinacl cord and connect CNS to sensory **don't need to know** - 31 pairs Week 9 Page 32 - 31 pairs ○ 8, 12, 5, 5, 1 ○ Unique organization **don't need to know** - Information impt for epidurals in pregnancy ○ Monitor mobility of these dermatomes - Spinal cord injuries- level of dysfunction - Shingles - comes out along a dermatome, doesn't cross midline, only on one side **don't need to know** - Highways though spinal cord - Descending tracts - motor, taking infor from CNS to body - Sensory tracts - take info outside body and send to CNS (afferent) - Blue tracts = sensory Week 9 Page 33 - Blue tracts = sensory - Both sensory and motor tracts are on both sides of spinal cord - Sensory ○ Fine touch, proprioception, vibration - Spinocerebellar tract: ○ Motor control, position, balance - Spinothalamic ○ Sensory about pain and temperature taken up to be integrated Motor: - Corticospinal - conscious control of skeletal muscle, major tract - "other" subconscious regulation of movement and balance - Sensory receptor, takes info to spinal cord, interneuron, and effector response through motor neuron - Ex. Riding bike - sensory info about balance, peddling, sends to spinal cord and get response, over time with practice, these responses become reflexive…learned activities ex. Gymnasts - We can test reflexes to see if parts of spinal cord is still working ○ Babinski for babies (looking for toes to flail not curl) ○ Knee reflex - patellar tendon ○ Brachiradial ○ Tricep STOP HERE Week 9 Page 34