NUR1112 ANS + NT 2024 Lectures PDF

The autonomic nervous system & neurotransmitters NUR1112 Fundamental Skills and Knowledge for Nursing and Midwifery Practice 1  Lecture slides prepared and delivered by: Dr Natalie Bennett Warning: This material has been reproduced and comm...

The autonomic nervous system & neurotransmitters NUR1112 Fundamental Skills and Knowledge for Nursing and Midwifery Practice 1  Lecture slides prepared and delivered by: Dr Natalie Bennett Warning: This material has been reproduced and communicated to you by or on behalf of Monash University under Part VB of the Copyright Act 1968 (the Act). The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice. Unless otherwise stated, all images are the property of Pearson Education Limited: Marieb & Hoehn, Human Anatomy & Physiology, 10th ed., 2016 Martini, Nath & Bartholomew, Fundamentals of Anatomy & Physiology, 2012 Amerman, Human Anatomy & Physiology, Global ed., 2016 Central nervous system (CNS) Peripheral nervous system (PNS) Central Brain and nervous system (CNS) spinal cord Peripheral Cranial nerves and spinalnervous nerves system Integrative and control centers Communication lines between the CNS and the rest of the body Sensory (afferent) Motor (efferent) division Sensory (afferent) division divisionMotor (efferent) division Somatic and visceral sensory Motor nerve fibers nerve fibers Conducts impulses from the CNS Conducts impulses from to effectors (muscles and glands) receptors to the CNS Somatic nervous Autonomic nervous system system (ANS) Somatic sensory Somatic nervous Autonomic nervous fiber system system (ANS) Somatic motorSympathetic Parasympathetic Visceral motor (voluntary) (involuntary) Skin division division Conducts impulses Conducts impulses from the CNS to from the CNS to skeletal muscles cardiac muscles, Visceral sensory fiber smooth muscles, Stomach and glands Skeletal muscle Motor fiber of somatic nervous system Sympathetic division Parasympathetic Mobilizes body division systems during activity Conserves energy Promotes house- keeping functions during rest Sympathetic motor fiber of ANS Heart Structure Function Parasympathetic Sensory (afferent) division of PNS motor fiber of ANS Bladder Motor (efferent) division of PNS Learning objectives 1. List the divisions of the autonomic nervous system and outline their respective functions. 2. Compare the organisation of the autonomic nervous system with that of the somatic nervous system. 3. Compare sympathetic and parasympathetic motor neurons and map their pathways from the central nervous system to effector tissues. 4. Identify the receptors that bind autonomic neurotransmitters (acetylcholine and noradrenalin) and explain how receptor binding mediates the differential effects of these neurotransmitters. 5. Identify central neurotransmitters and their major effects. Why is this important? This content is foundational for informed clinical practice Many drugs target ANS neurotransmitters receptors, stimulating or inhibiting selected organs or body areas It is important to understand how these drugs affect the ANS and their potential side effects à this determines the physical and mental abilities of your patients Divisions of the ANS Learning Objective 1: List the divisions of the autonomic nervous system and outline their respective functions Peripheral nervous system Sensory (afferent) Motor (efferent) division division Somatic nervous Autonomic nervous system system (ANS) Sympathetic Parasympathetic division division  Dual innervation Most effector organs are innervated by both sympathetic and parasympathetic divisions ANS divisions can work independently or together Divisions generally have opposing effects One division predominates in specific circumstances Divisions counterbalance to control organ function and maintain homeostasis https://png.icons8.com/metro/1600/seesaw.png  Organ Sympathetic response Sympathetic Heart Increased rate and strength of function contraction: blood pressure increases Vasodilation in cardiac & skeletal muscle Blood vessels to increase blood flow; vasoconstriction Prepares the in non-essential areas, e.g. digestive tract Lung Bronchiole (airway) dilation body for heightened Liver Stimulates release of glucose into blood activity, i.e. Sweat glands Stimulates sweating exercise, Salivary glands Stimulates secretion of thick saliva excitement, Stomach Decreased secretion and motility emergency, Intestine Decreased secretion and motility embarrassment Kidney Reduced blood flow, reduced urine formation → fight-or-flight Urinary bladder Micturition (urination) inhibited Adrenal gland Secretion of adrenalin, noradrenalin Spleen Release of stored blood Rectum Defecation inhibited Iris (pupil) dilates, lens flattens: adjusts for Eye http://pixabay.com/static/uploads/photo/2012/04/13/20/12/runners-33482_150.png distance vision  Organ Parasympathetic response Para- Heart Decreased heart rate: blood pressure sympathetic decreases function Blood vessels - Lung Bronchiole constriction Stimulates abdominal Liver Increases glucose uptake from blood visceral activity, Sweat glands - conserves Salivary glands Increased secretion watery saliva energy à rest Stomach Increased secretion and motility and digest Intestine Increased secretion and motility Increased blood flow, increased urine Kidney formation Urinary bladder Micturition promoted Adrenal gland - Spleen - http://www.publicdomainpictures.net/pictures/40000/t2/child-and-book- 1366361204W0q.jpg Rectum Defecation promoted Iris (pupil) constricts, lens thickens: Eye adjusts for near vision Somatic vs autonomic nervous systems Learning Objective 2: Compare the organisation of the autonomic nervous system with that of the somatic nervous system Both are efferent divisions that distribute motor commands Differ in: 1. Neural (efferent) pathways (i.e. from CNS to effector) 2. Effectors (target organs) 3. Organ response 4. Neurotransmitters (NT)  Somatic Nervous Autonomic Nervous System Overview System Overview Input from: Cerebral cortex Limbic system Postganglionic neuron (Notes on the next slide)  Somatic Nervous Autonomic Nervous System Overview System Overview Control Primary motor cortex Hypothalamus centre (input from cerebellum (input from limbic system and basal nuclei) and cerebrum) Central Upper motor neuron CNS interneuron(s) neurons Peripheral Lower motor neuron Preganglionic neuron motor Postganglionic neuron neurons Target Skeletal muscles Cardiac muscle Smooth muscle Glands Function Voluntary movement Involuntary control of Somatic reflexes Visceral organ function Glandular activity Visceral reflexes Peripheral motor neurons Somatic NS: Lower motor neuron cell body in either: 1. spinal cord motor nucleus (anterior grey horn), axon exits CNS via ventral root of spinal nerve, OR 2. brainstem nucleus, axons exit CNS via cranial nerve Autonomic NS: TARGET SOMATIC Preganglionic neuron cell body Lower motor neuron in either: (myelinated) Skeletal muscle fibers 1. motor nucleus CNS Smooth and (lateral grey Postganglionic motor cardiac muscle AUTONOMIC neuron cells horn/matter), axon exits CNS Glands Preganglionic motor via ventral neuron OR root of spinal nerve OR 2. brainstem Postganglionic nucleus, axons neuron cell body exits CNS via within a peripheral cranial nerve ganglion Peripheral motor neurons neurotransmitters TARGET Acetylcholine SOMATIC released by Lower motor neuron LMN Skeletal muscle (myelinated) fibers (always CNS Smooth and excitatory à Postganglionic motor cardiac muscle à increases AUTONOMIC neuron cells target activity) Preganglionic motor Glands OR neuron Acetylcholine (ACh) released by preganglionic neuron Acetylcholine OR Noradrenalin (always excitatory à stimulates (NA) released by postganglionic an action potential in neuron postganglionic neuron) (may be excitatory à increases target activity OR inhibitory à reduces target activity Summary Somatic NS Autonomic NS Peripheral Lower motor Preganglionic Postganglionic neuron Location of 1. motor nucleus 1. motor nucleus Peripheral cell body in anterior grey in lateral grey ganglion horn of spinal horn or gray cord (axon matter (axon exits CNS via exits CNS via ventral root of ventral root of spinal nerve) spinal nerve) OR OR 2. brainstem 2. brainstem nucleus (axon nucleus (axon exits CNS via exits CNS via cranial nerve) cranial nerve) NT released ACh ACh ACh or NA Effect of NT Always excitatory Always excitatory Excitatory à on target à skeletal muscle à stimulates target activity (target) activity action potential in increases OR increases postganglionic inhibitory à target neuron (target) activity decreases Sympathetic vs parasympathetic NS Learning Objective 3: Compare sympathetic and parasympathetic motor neurons and map their pathways from the central nervous system to effector tissues. Similarities: Serve many of the the same organs Involve pre- and post-ganglionic neurons Preganglionic neurons release ACh Presence of ganglia Differences: Both divisions do not innervate all organs Location of preganglionic cell bodies and axon exit points from the CNS Length of the axons Location of the ganglia Parasympathetic Brainstem division Also called the craniosacral division - WHY? Target organs Preganglionic neurons arise Preganglionic from opposite ends of the Neuron (cell body in Postganglionic CNS brainstem neuron motor nucleus) Brain stem à axons exit CNS via cranial nerves Parasympathetic ganglia Sacral region of spinal cord Preganglionic (S2 – S4) à axons exit via Neuron spinal nerves (ventral root) (cell body in motor nucleus in lateral Ganglia located close to, gray matter) or within, the target organ Target Preganglionic axon = long Sacral organs Region Postganglionic axon = short (S2-S4) Postganglionic neuron  Eye CN III Lacrimal gland Cranial pathways: CN VII Nasal mucosa CN III Oculomotor nerve CN VII CN VII Facial nerve CN IX Salivary, nasal and lacrimal CN IX Glossopharyngeal CN X glands Heart nerve CN X Vagus nerve Lung Sacral pathways: Liver and gallbladder sacral spinal cord segments Stomach S2 – S4 Pancreas Innervate: S2 Large Pelvic organs S4 intestine Distal portion of large Small intestine intestine Rectum Urinary bladder Genitalia and ureters Sympathetic division Preganglionic Neuron Also called the (cell body in thoracolumbar division – motor nucleus in WHY? lateral gray horn, T1-L2) All preganglionic fibres arise Cervical within spinal cord segments T1 - L2 Cell bodies in motor nuclei Target of lateral gray horns organs Thoracic Axons exit spinal cord via spinal nerves (ventral root) Ganglia located close to spinal cord Lumbar Sympathetic Preganglionic axon = short ganglia Postganglionic axon = long Postganglionic neuron  Eye Segments T1 – T6 Lacrimal gland Sympathetic innervate the head trunk Nasal mucosa ganglia Blood vessels; skin and thorax (arrector pili muscles and sweat glands) Segments T5 - L2 Salivary glands innervate Heart abdominopelvic T1 Lung organs Liver and Ganglia gallbladder Chain of 23 L2 Stomach connected by Spleen fibres to form Adrenal medulla sympathetic trunk Kidney Flank both sides of Small intestine the vertebral Large intestine column Rectum Preganglionic Postganglionic Extend from neck to pelvis Genitalia (uterus, vagina, and penis) and urinary bladder  Adrenal Gland The Adrenal Medulla Cortex Medulla Kidney A and NA released into the SYMPATHETIC blood à preganglionic neurons – synapse with adrenal effect any medullary cells Thoracic and 1 Preganglionic neuron cell bearing lumbar spinal releases ACh adrenergic cord Noradrenalin (NA) receptors à ACh Adrenalin (A) To target enhance cells throughout and prolong Adrenal medulla (inner region of adrenal body the gland) sympathetic 2 ACh binds to nicotinic receptors on Blood vessel response adrenal medulla cells. 3 ACh stimulates medullary cells to release A and NA into bloodstream Sympathetic effects are widespread Sympathetic activation occurs during exercise, excitement, emergency, embarrassment Sympathetic effects are widespread The adrenal medulla releases A and NA à blood à enhance and prolong sympathetic effects Single preganglionic neuron can synapse with many postganglionic neurons to activate multiple effectors  Neurotransmitters Preganglionic neurons à release ACh Postganglionic neurons: Sympathetic à release NA Parasympathetic à release ACh Always excites target (postganglionic neuron) à action potential Depending on ACh SYMPATHETIC NA target NT receptor type, NT binding will Ganglion either excite target à PARASYMPATHETIC increase ACh ACh activity OR inhibit target à decrease Ganglion activity  Sympathetic Parasympathetic Summary … version 1 Brainstem Preganglionic Preganglionic neuron neuron Cell body in brainstem cell body in motor motor nucleus nucleus T1-L2 long axon, exits CNS via short axon, exits CNS cranial nerve via spinal nerve releases ACh (excites releases ACh (excites target) target) Target organs Cervical Postganglionic Target neuron organs Thoracic cell body Parasympathetic forms ganglia ganglion Close to or short axon within target releases ACh Lumbar (excites or inhibits target) Postganglionic neuron cell body forms ganglion Sacral Target long axon organs Sympathetic (S2-S4) releases NA ganglia Preganglionic neuron (excites or Close to spinal Cell body in motor nucleus in lateral gray matter inhibits target) cord (chain) long axon, exits CNS via spinal nerve releases ACh (excites target) Summary … version 2 Preganglionic Postganglionic neuron neuron short axon, cell body Sympathetic exits CNS via forms ganglion (thoracolumbar division) spinal nerve long axon releases ACh releases NA Thoracic and lumbar spinal cord (T1-L2) Ganglion Close to spinal Target cell cord (chain) Parasympathetic (craniosacral division) Ganglion Close to or Brainstem within target or sacral spinal cord (S2-S4) Target cell Preganglionic Postganglionic neuron neuron long axon, exits CNS via cell body forms ganglion cranial or spinal nerve short axon releases ACh releases ACh Neurotransmitter receptors Learning Objective 4: Identify the receptors that bind autonomic neurotransmitters (acetylcholine and noradrenalin) and explain how receptor binding mediates the differential effects of these neurotransmitters. Peripheral motor neurons release either acetylcholine (ACh) or noradrenalin (NA) Receptors that bind acetylcholine are called cholinergic receptors (term is also used for neurons that release ACh or synapses where ACh is used) Receptors that bind noradrenalin (and adrenalin) are called adrenergic receptors (term is also used for neurons that release NA or synapses where NA is used)  Receptors that bind acetylcholine are called cholinergic receptors – 2 subtypes: nicotinic and muscarinic Receptors that bind noradrenalin are called adrenergic receptors – 2 subtypes: a and b (also bind adrenalin) Sympathetic Parasympathetic Preganglionic neuron à releases ACh Postganglionic neuron dendrites and cell body bear cholinergic receptors (subtype: nicotinic) that bind ACh Axon terminal releases: NA ACh Target cell NT receptors: Adrenergic Cholinergic (subtype: a or b) (subtype: muscarinic)  Cholinergic receptors bind ACh Two subtypes of cholinergic receptors (named after drugs – nicotine and muscarine) 1. Nicotinic – always excitatory à à increases target activity 2. Muscarinic – excitatory or inhibitory à à increases or decreases target activity respectively M&H: Table 14.3 Receptor Type Location Effect of NT binding All ANS postganglionic neurons Excitation à increased Nicotinic Adrenal medullary cells activity of target Skeletal muscles Excitation of most targets à increased activity All parasympathetic Muscarinic Inhibition of cardiac target organs muscle à decreased activity  Adrenergic receptors bind NA and A Two major subtypes of adrenergic receptors 1. Alpha (a; subtypes a1, a2) Excitatory or inhibitory 2. Beta (b; subtypes b1, b2, b3) Refer to M&H: Table 14.3 Receptor Major locations Effect of NT binding Excitatory à increases heart rate and b1 Heart force of contraction Airways, blood vessels Inhibitory à decreased activity, i.e. (in heart, liver, skeletal relaxes smooth muscle à dilates b2 muscle), digestive tract, airways and blood vessels, relaxes urinary organs muscles in digestive and urinary organs Blood vessels (except in Excitatory à increased activity, i.e. heart, liver, skeletal a1 constricts blood vessels and visceral muscles), all organ sphincters, dilates pupils sympathetic targets Differential effects of NT on targets The response of a target organ to a NT (i.e. increased or decreased activity) depends on the NT receptor – i.e. what subtype of cholinergic or adrenergic receptor, the target bears How does the binding of NT to different receptors increase or decrease target activity? Ø Review synaptic transmission Ø Extend our knowledge of graded potentials … Synaptic transmission … 1. Action potential arrives at axon terminal 2. Voltage-gated Ca2+ channels open and Ca2+ Mitochondrion Ca2+ enters Ca2+ Ca2+ Ca2+ 3. Ca2+ entry triggers Synaptic neurotransmitter Axon cleft (NT) release terminal 4. NT diffuses across cleft à Synaptic binds receptors vesicles (chemically-gated ion channels) on postsynaptic membrane Postsynaptic neuron Ion movement Enzymatic degradation Graded potential Reuptake Diffusion away from synapse 5. Binding of NT opens ion channels à graded potential à threshold à action potential in postsynaptic cell 6. NT effects terminated Postsynaptic potentials A graded potential = postsynaptic potential Excitatory postsynaptic Inhibitory postsynaptic potential (EPSP): potential (IPSP) 1. NT binds receptors on 1. NT binds receptors on postsynaptic membrane postsynaptic membrane 2. Opens gated ion channels 2. Opens gated ion channels 3. Graded depolarization (i.e. 3. Graded hyperpolarization Na+ ions enter the cell) (i.e. K+ ions exit the cell) 4. Postsynaptic cell EXCITED - 4. Postsynaptic cell INHIBITED - membrane potential closer to membrane potential further threshold, therefore … from threshold, therefore … 5. Action potential more likely 5. Action potential less likely to to occur occur 6. Overall effect ► increased 6. Overall effect ► decreased target activity target activity  Sympathetic Parasympathetic Preganglionic neuron à releases ACh Postganglionic neuron Nicotinic cholinergic receptors à always excitatory à action potential à message transmitted Axon terminal releases: NA ACh Target cell NT receptors: Adrenergic Muscarinic Excitatory or inhibitory Target cell response to a NT is determined by whether the NT receptor is a chemically-gated ion channel that depolarises or hyperpolarises the target cell membrane: Excitatory receptor à EPSP depolarises membrane à action potential more likely à increases target activity Inhibitory receptor à IPSP hyperpolarises cell membrane à action potential less likely à decreases target activity  Many drugs target NT receptors … Various drugs will bind to cholinergic or adrenergic receptors and effect ANS function Agonists – drugs that mimic the action of the NT à promote normal response Antagonists – drugs that bind the receptor and block the action of the NT à prevent normal response Adrenergic receptors β1 receptors β2 receptors Receptor location Cardiac muscle Smooth muscle in airways Normal response to Increased cardiac activity Dilation of airways à binding of NA à increase blood pressure increase airflow Enhance normal response Enhance normal response Agonist drug à increase airflow (e.g. à increase BP asthma puffers) Block normal response à Block normal response à Antagonist drug prevents increase in BP prevents airway dilation (effectively decreases BP) (effectively reduces airflow) Neurotransmitters Learning Objective 5: Identify central neurotransmitters and their major effects NT (and electrical signals) are the language of the nervous system Some neurons make only 1 NT Most neurons make 2 or more NT Induce excitatory or inhibitory responses in postsynaptic membranes More than 50 NT identified (M&H Table 11.5) Many neuropsychological disorders (e.g. depression) traditionally thought to be caused by NT imbalances – this theory now questionable http://commons.wikimedia.org Acetylcholine Motor control outside the CNS Within the CNS: Region Involved in: Cerebral cortex Cognition Hippocampus Memory Brainstem Consciousness Low levels in Alzheimer’s patients http://www.malonie.com/health/Alzheimer/  https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSq5Q_vtNBr8qfbLHHPuVjRoeE8R61Wt5d43O2Rm1FYDFhub60BHg Biogenic amines Broadly distributed in the brain Emotional behaviour Regulate biological clock Imbalances associated with mental illness??? (no consistent evidence to support this!!) drugs that enhance NT release or block reuptake associated with relief of symptoms of anxiety and depression in some people à how do they work??? Noradrenaline Dopamine Serotonin stimulates brain stimulates brain mood regulation, reward and reward and sleep, appetite, pleasure centres pleasure centres nausea, migraine (“feel good” NT) (“feel good” NT) headaches involved in high levels noted reducing stress and with schizophrenia enhancing deficient in attention Parkinson’s disease Amino acids GABA (g-aminobutyric acid) Main inhibitory NT in the brain Helps to regulate sleep/wakefulness Involved in motor control à helps to regulate skeletal muscle tone by dampening activity GABA blockers (i.e. no dampening) à convulsions Alcohol increases dampening effect → impaired motor coordination Glutamate Involved in learning and memory Excessive release à excitotoxicity (kills surrounding neurons), e.g. CVA, Alzheimer’s disease http://www.publicdomainpictures.net https://cdn.pixabay.com/photo/2018/02/04/21/40/silhouette-3130960__340.png  Neuropeptides Substance P Produced by damaged tissue Stimulates peripheral nociceptors Mediates pain transmission to the CNS Endorphins Includes endorphins and enkephalins Inhibits perception of pain in the CNS Natural opiates – chemically similar to morphine (agonist) à analgaesia, sleepiness, wellbeing https://cdn.pixabay.com/photo/2015/10/31/12/30/pain-1015574_960_720.jpg