BIOH111. o Cell Module o Tissue Module o Integumentary system o Skeletal system o Muscle system o Nervous system o Endocrine system

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1 BIOH111 o Cell Module o Tissue Module o Integumentary system o Skeletal system o Muscle system o Nervous system o Endocrine system Endeavour College of Natural Health endeavour.edu.au 1

2 Textbook and required/recommended readings o Spinal cord anatomy: Principles of anatomy and physiology. Tortora et al; 14 th edition: Chapter 13; section 13.1 o Spinal cord physiology: Principles of anatomy and physiology. Tortora et al; 14 th edition: Chapter 13; section 13.3 Endeavour College of Natural Health endeavour.edu.au 2

3 BIOH111 NERVOUS SYSTEM MODULE o Session 15 (Lectures 27 and 28) Organisation and histology of the nervous system o Session 16 (Lectures 29 and 30) Function of neurons: conduction of nerve impulses o Session 17 (Lectures 31 and 32) CNS: Brain anatomy and function o Session 18 (Lectures 33 and 34) Sensations and special senses o Session 19 (Lectures 35 and 36) Spinal cord anatomy and physiology o Session 20 (Lectures 37 and 38) Spinal nerves and somatic sensory and motor pathways o Session 21 (Lectures 39 and 40) Autonomic nervous system: anatomy and function Endeavour College of Natural Health endeavour.edu.au 3

4 BIOH111 Lectures 39 and 40 Autonomic nervous system (ANS): anatomy and function Department of Bioscience endeavour.edu.au

5 Lecture 39: Anatomy of ANS Objectives Describe basic anatomy of ANS Understand the division of ANS Describe structure and function of 2 ANS divisions Integrated and control of autonomic functions Describe autonomic reflexes and autonomic control by higher centers Lecture 40: ANS neuron types, neurotransmitters and receptors Describe differences between cholinergic and adrenergic neurons and receptors Define receptor agonists and antagonists Physiological effects of ANS Describe and understand autonomic tone Define differences between sympathetic and parasympathetic responses Endeavour College of Natural Health endeavour.edu.au 5

6 Nervous System Divisions - revision o Central nervous system (CNS) consists of the brain and spinal cord o Peripheral nervous system (PNS) consists of cranial and spinal nerves that contain both sensory and motor fibers connects CNS to muscles, glands & all sensory receptors 3 subdivisions: 1. Somatic (voluntary) nervous system (SNS) 2. Autonomic (involuntary) nervous systems (ANS) sympathetic and parasympathetic divisions 3. Enteric nervous system (ENS) Endeavour College of Natural Health endeavour.edu.au 6

7 Organization of the Nervous System - revision Sensory component of the PNS Motor component of PNS Effectors (muscles and glands) Endeavour College of Natural Health endeavour.edu.au 7

8 AUTONOMIC NERVOUS SYSTEM o Function: maintains homeostasis and operates without conscious control; regulates activity of smooth muscle, cardiac muscle & certain glands o Structure: operates via reflex arcs; continual flow of sensory afferent input from receptors in organs and efferent motor output to the same effector organs; includes autonomic sensory neurons, integrating centers in the CNS and autonomic motor neurons o Regulation: hypothalamus and brain stem Endeavour College of Natural Health endeavour.edu.au 8

9 SOMATIC vs AUTONOMIC NERVOUS SYSTEM Structure Function Regulation Motor pathways Final effect of motor neuron Somatic Reflex arcs: sensory neurons, integrating centres in spinal cord and motor neurons Innervation of skeletal muscle; voluntary movement Single motor neuron Always excitation Autonomic Reflex arcs: autonomic sensory neurons, integrating centers in spinal cord and autonomic motor neurons Innervation of smooth muscle, cardiac muscle & certain glands; involuntary movement hypothalamus and brain stem Two neurons in a series Excitation or inhibition Endeavour College of Natural Health endeavour.edu.au 9

10 BASIC ANATOMY OF ANS Revision: ganglion is..? o Preganglionic neuron cell body in brain or spinal cord; exits as a cranial or spinal nerve axon is myelinated type B fiber that extends to autonomic ganglion o Postganglionic neuron (forms basis for ANS division) cell body lies outside the CNS in an autonomic ganglion axon is unmyelinated type C fiber that terminates in a visceral effector Revision: session 14 what is the difference between Type B and C fiber? Why is this important in this context? Endeavour College of Natural Health endeavour.edu.au 10

11 AUTONOMIC REFLEX ARCS Components: 1. sensory receptor 2. sensory neuron 3. integrating center 4. pre & postganglionic motor neurons 5. visceral effectors o Autonomic reflex adjusts the activity of a visceral effector, often unconsciously (e.g. changes in blood pressure, filling & emptying of bladder or defecation) o Input: emotions and visceral sensory information (e.g. smell, taste, temperature, osmolarity of blood) Endeavour College of Natural Health endeavour.edu.au 11

12 ANS DIVISION Sympathetic postganglionic neuron Parasympathetic postganglionic neuron Spinal cord Effectors Spinal cord Effectors Autonomic ganglion Autonomic ganglion o Output (efferent) part of the ANS is divided into two principal parts: 1. Sympathetic Division functions in the situation of energy consumption (e.g. E situations ; fright-or-flight) 2. Parasympathetic Division - functions in the situation of energy conservation and restoration (e.g. rest-and-digest) o Dual innervation: organs can receive impulses from both sympathetic and parasympathetic fibers where one speeds up organ and one slows down organ (e.g. sympathetic NS increases heart rate while parasympathetic NS decreases heart rate) Endeavour College of Natural Health endeavour.edu.au 12

13 Examples of autonomic arcs Endeavour College of Natural Health endeavour.edu.au 13

14 Sympathetic division Parasympathetic division Look at the spatial separation of the 2 divisions. Why do you think this is? Endeavour College of Natural Health endeavour.edu.au 14

15 Sympathetic trunk SYMPATHETIC GANGLIA o Sites of synaptic connection between pre- and post ganglionic synaptic neurons. 2 types: 1. sympathetic trunk or vertebral chain: lie in a vertical row on either side of the vertebral column 2. prevertebral or collateral ganglia that lie anterior to the spinal column and close to large abdominal arteries (5 ganglia: coeliac, superior mesenteric, inferior mesenteric ganglia, aorticorenal and renal) Preverterbral ganglia Endeavour College of Natural Health endeavour.edu.au 15

16 POSTGANGLIONIC SYMPATHETIC FIBERS Above the diaphragm from sympathetic trunk: 1. out same level: e.g. spinal nerve route 2. up chain & out spinal nerve; e.g. sympathetic chain route 2 1 Below the diaphragm from prevertebral ganglia: 3. collateral ganglion route; e.g. out splanchnic nerve to collateral ganglion 3 Endeavour College of Natural Health endeavour.edu.au 16

17 PARASYMPATHETIC GANGLIA o Sites of synaptic connection between pre- and post ganglionic parasympathetic neurons o Parasympathetic ganglia are the terminal or intramural ganglia located very close to or actually within the wall of a visceral organ. Terminal ganglia o Terminal ganglia of the head have specific names (ciliary, pterygopalatine, submandibular and otic ganglia) Endeavour College of Natural Health endeavour.edu.au 17

18 AUTONOMIC PLEXUSES o Structure: tangled networks of sympathetic and parasympathetic neurons; lie along major arteries; named for its undelaying artery: major autonomic plexuses are in 3 anatomic locations: thorax, abdomen and pelvis (cardiac, pulmonary, celiac, superior mesenteric, inferior mesenteric, renal and hypogastric) o Function: maintain spatial and localized homeostasis of organs; maintaining feedback of information Endeavour College of Natural Health endeavour.edu.au 18

19 o Hypothalamus overall control and integration CONTROL OF THE ANS o Cerebral cortex, limbic lobe, hypothalamus and brain stem different inputs (e.g. limbic lobe- emotions) o Conscious (originates in hypothalamus) and subconscious control (mostly sympathetic output) Endeavour College of Natural Health endeavour.edu.au 19

20 Lecture 39: Anatomy of ANS Objectives Describe basic anatomy of ANS Understand the division of ANS Describe structure and function of 2 ANS divisions Integrated and control of autonomic functions Describe autonomic reflexes and autonomic control by higher centers Lecture 40: ANS neuron types, neurotransmitters and receptors Describe differences between cholinergic and adrenergic neurons and receptors Define receptor agonists and antagonists Physiological effects of ANS Describe and understand autonomic tone Define differences between sympathetic and parasympathetic responses Endeavour College of Natural Health endeavour.edu.au 20

21 ANS NEUROTRANSMITTERS o Postganglionic neurons are classified based on the neurotransmitter they release. 2 types: 1. Adrenergic 2. Cholinergic Endeavour College of Natural Health endeavour.edu.au 21

22 NEUROTRANSMITTERS - revision o Acetylcholine (ACh) released by many PNS neurons & some CNS Function: learning and memory; activates muscle action; awakening and attention excitatory on NMJ but inhibitory at others inactivated by acetylcholinesterase o Norepinephrine or noradrenaline (NE) Structure: monoamine, synthesized from dopamine Released by CNS and ANS neurons Function: regulates mood, dreaming, awakening from deep sleep Excitatory and inhibitory Enzymatically inactivated by monoamine oxidase (MAO) or catechol-o-methyltransferase (COMT) Endeavour College of Natural Health endeavour.edu.au 22

23 ADRENERGIC NEURONS o Adrenergic neurons release NE and are only postganglionic sympathetic neurons o Excites or inhibits organs depending on receptors expressed on effector cells; 2 types of receptors o Long lasting: NE lingers in synaptic gap and is additionally released by the adrenal gland Endeavour College of Natural Health endeavour.edu.au 23

24 ADRENERGIC RECEPTORS GPCR G-protein coupled receptor; signals transmitted into the cell; 2 types differentially expressed: alpha and beta receptors. Same trigger Differential expression of receptors Different signalling pathways Different outcomes Endeavour College of Natural Health endeavour.edu.au 24

25 CHOLINERGIC NEURONS o Cholinergic neurons release acetylcholine; they are: all preganglionic neurons all parasympathetic postganglionic neurons few sympathetic postganglionic neurons (to most sweat glands) o Excites or inhibits organs depending on receptors expressed on effector cells; 2 types of receptors: nicotinic and muscarinic Endeavour College of Natural Health endeavour.edu.au 25

26 CHOLINERGIC RECEPTORS 1. Nicotinic receptors Ionotropic receptors: ion channel Nicotinic receptors are found on dendrites & cell bodies of autonomic sympathetic neurons and at NMJ Activation leads to excitation of the postsynaptic cell. Types Structure Function Endeavour College of Natural Health endeavour.edu.au 26

27 CHOLINERGIC RECEPTORS 2. Muscarinic receptors Metabotropic receptors: GPCR Muscarinic receptors are found on plasma membranes of all parasympathetic effectors Activation leads to either excitation or inhibition depending on the differential receptor expression Types Structure Function Endeavour College of Natural Health endeavour.edu.au 27

28 Effector side of nerve conduction REVISION EXCITATORY & INHIBITORY POTENTIALS o The effect of a neurotransmitter on the postsynaptic terminal/effector can be either excitatory or inhibitory: 1. Excitatory postsynaptic potentials (EPSP) Structure: mediated by ionotropic receptors; net effect: results from the opening of ligand-gated cation channels Function: depolarizing postsynaptic cell is more likely to reach threshold Endeavour College of Natural Health endeavour.edu.au 28

29 Effector side of nerve conduction REVISION EXCITATORY & INHIBITORY POTENTIALS 2. Inhibitory postsynaptic potential (IPSP) Structure: mediated by ionotropic and metabotropic receptors; net effect: results from the opening of ligand-gated Cl- or K+ channels Function: postsynaptic cell becomes more negative or hyperpolarized postsynaptic cell is less likely to reach threshold Endeavour College of Natural Health endeavour.edu.au 29

30 REVISION Endeavour College of Natural Health endeavour.edu.au 30

31 Autonomic vs somatic nerves - summary Endeavour College of Natural Health endeavour.edu.au 31

32 RECEPTOR AGONISTS AND ANTAGONISTS What would drugs in red be? In green? From your own experiences can you name any others? o Agonist: substance that binds to and activates a receptor, mimicking the effect of a natural neurotransmitter or hormone. o Antagonist: substance that binds to and blocks receptor, preventing natural neurotransmitter or hormone from exerting its effect. o Pharmacology agents and natural products can serve as agonists or antagonists to selectively activate or block ANS receptors. Endeavour College of Natural Health endeavour.edu.au 34

33 PHYSIOLOGICAL EFFECTS OF ANS o Most body organs receive dual innervation; hypothalamus regulates balance (tone) between sympathetic and parasympathetic activity levels o Some organs have only sympathetic innervation sweat glands, adrenal medulla and many blood vessels controlled by regulation of the tone of the sympathetic system Sympathetic: heart and respiratory rate digestion and elimination Parasympathetic: heart and respiratory rate digestion and elimination Endeavour College of Natural Health endeavour.edu.au 35

34 SYMPATHETIC RESPONSES o Dominance caused by 2 types of activities: 1. physical/emotional stress: E situations (emergency, embarrassment, excitement, exercise) 2. alarm reaction: flight-or-fight response o Response examples: dilation of pupils; increase of heart rate, force of contraction & BP; decrease in blood flow to nonessential organs Endeavour College of Natural Health endeavour.edu.au 37

35 PARASYMPATHETIC RESPONSES o Dominance caused by rest-anddigest activities o Helps conserve and restore body energy during times of rest; dominate over sympathetic impulses o SLUDD type responses = salivation, lacrimation, urination, digestion & defecation and 3 decreases --- decreased HR, diameter of airways and diameter of pupil Endeavour College of Natural Health endeavour.edu.au 38

36 Clinical application: DISORDERS o Raynaud s phenomenon is due to excessive sympathetic stimulation of smooth muscle in the arterioles of the digits as a result the digits become ischemic after exposure to cold or with emotional stress. Endeavour College of Natural Health endeavour.edu.au 39

37 Clinical application: AUTONOMIC DYSREFLEXIA o Exaggerated response of sympathetic NS in cases of spinal cord injury above T6 o Certain sensory impulses trigger mass stimulation of sympathetic nerves below the injury o Result vasoconstriction which elevates blood pressure parasympathetic NS tries to compensate by slowing heart rate & dilating blood vessels above the injury pounding headaches, sweating warm skin above the injury and cool dry skin below can cause seizures, strokes & heart attacks Endeavour College of Natural Health endeavour.edu.au 40

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