HSC1007 Anatomy and Physiology 1 - Introduction to Neuroscience 1 PDF

HSC1007 ANATOMY AND PHYSIOLOGY 1 INTRODUCTION TO NEUROSCIENCE 1 GROSS AND SYSTEM NEUROBIOLOGY ANDY LEE (PHD) ASSISTANT PROFESSOR FACULTY HALL #04-17 OFFICE PHONE: 6592 2524 [email protected] LEARNING OUTCOMES At the end of the lesson, you should be able to:  Describe the anatomical a...

HSC1007 ANATOMY AND PHYSIOLOGY 1 INTRODUCTION TO NEUROSCIENCE 1 GROSS AND SYSTEM NEUROBIOLOGY ANDY LEE (PHD) ASSISTANT PROFESSOR FACULTY HALL #04-17 OFFICE PHONE: 6592 2524 [email protected] LEARNING OUTCOMES At the end of the lesson, you should be able to:  Describe the anatomical and functional divisions of the nervous system  Describe the general structure and functions of the sympathetic and parasympathetic division of the autonomic system  Describe the basic structural and organizational features of the central nervous system CELLS TO SYSTEM Cells of the Nervous System Nervous System Allen, N., Barres, B. Glia — more than just brain glue. Nature 457, 675–677 (2009). NEXT LECTURE TODAY GENERAL FUNCTIONS OF THE NERVOUS SYSTEM  Sensory  Communicative  Integrative  Motor  So as to respond to both internal and external stimuli STRUCTURAL ORGANIZATION OF THE NERVOUS SYSTEM  Structurally, the nervous system is organized into the central and peripheral nervous system  Central nervous system (CNS): brain and spinal cord  Peripheral nervous system (PNS): nerve fibers Fig. 5.28, Sherwood PERIPHERAL NERVOUS SYSTEM (PNS)  12 pairs of cranial nerves Fig. 14-18; Martini et al. PERIPHERAL NERVOUS SYSTEM (PNS)  31 pairs of spinal nerve Fig. 5.23, Sherwood Fig. 2.54, Gray’s PERIPHERAL NERVOUS SYSTEM (PNS)  Subdivided into 2 divisions  Afferent division  Carries information to the CNS  Sensory stimuli and visceral stimuli  Efferent division  Transmits information from the CNS to effector organs Sensory receptors Afferents Effector organs Efferents CNS DIVISIONS OF THE EFFERENT NERVOUS SYSTEM  Functionally, the efferent nervous system can be divided into:  Somatic nervous system  Fibers of the motor neurons that supply the skeletal muscles  Subjected to voluntary control  Autonomic nervous system (ANS)  Fibers that innervate smooth muscle, cardiac muscle, and glands  Involuntary  Sympathetic and parasympathetic nervous system COMPONENTS OF THE NERVOUS SYSTEM Central nervous system (CNS) Peripheral nervous system (PNS) Nerves Afferent Efferent Somatic Autonomic Sympathetic Parasympathetic ORGANIZATION OF THE NERVOUS SYSTEM Figure 5-1; Sherwood human physiology PATHWAYS OF THE AUTONOMIC NERVOUS SYSTEM (ANS)  An autonomic nerve pathway consists of a two-neuron chain  Preganglionic neuron: synapses with the cell body of the postganglionic fiber in a ganglion outside the CNS  Postganglionic neuron: sends axons that end on the effector organ  Nasal Eye Lacrimal (tear) gland mucosa Parotid (salivary) gland PATHWAYS OF THE ANS Sympathetic Parasympathetic Sublingual and  Sympathetic and parasympathetic Trachea submandibular (salivary) glands III Lung VII nervous systems dually innervate IX Cranial nerves most visceral organs T1 T2 X T3 T4  Dual innervation: innervation of a single Spinal nerves T5 T6 Sympathetic T7 organ by both branches of the trunk Heart T8 T9 T10 autonomic nervous system T11 T12 1 Liver Stomach L L2 Splanchnic  Times of sympathetic dominance: “fight- nerves S2 or-flight” response Gall bladder Spleen S3 S4 Adrenal gland Pancreas  Times of parasympathetic dominance: Spinal nerves “rest-and-digest” response Kidney  Advantage? Small intestine Colon Rectum KEY Sympathetic preganglionic fiber Urinary bladder Sympathetic postganglionic fiber Parasympathetic preganglionic fiber Genitalia Figure 7-3; Sherwood human physiology Parasympathetic postganglionic fiber  DISTRIBUTION OF SYMPATHETIC INNERVATION  Preganglionic neurons are located between segments T1 and L2 of the spinal cord.  Each preganglionic fiber can synapse with more than one ganglionic neurons Figure 16-2; Martini et al. Fundamentals of anatomy and physiology  DISTRIBUTION OF PARASYMPATHETIC INNERVATION  Innervate organs of 3 main regions: cranial, trunk and pelvic  Long preganglionic and short postganglionic fibers Figure 16-2; Martini et al. Fundamentals of anatomy and physiology EFFECTS OF ANS ON VARIOUS ORGANS Table 7-1; Sherwood human physiology COMPARISON Table 7-3; Sherwood human physiology PATHWAYS OF THE ANS CENTRAL NERVOUS SYSTEM (CNS)  Brain and spinal cord  Gray matter – generic term for collection of cell bodies (soma) in the CNS  White matter – generic term for collection of CNS axons Fig. 1.6, Neuroscience: Exploring the brain PROTECTION OF THE CNS  Major features protect the CNS from injury 1. Cranium and vertebral column 2. Meninges 3. Cerebrospinal fluid 4. Blood–brain barrier PROTECTION OF THE CNS  Meninges  Three meningeal membranes wrap, protect, and nourish the central nervous system  Continuous with spinal meninges  Dura mater, arachnoid mater, and pia mater PROTECTION OF THE CNS  Cerebrospinal Fluid (CSF)  The brain floats in its own special CSF  Shock absorbing fluid  Surrounds and cushions the brain and spinal cord  Formed by choroid plexuses in ventricles (brain)  Functions  Cushions delicate neural structures  Supports brain  Transports nutrients, chemical messengers, and waste products VENTRICLES Fig. 5-5, Sherwood MENINGES AND CSF 1.Produced by ependymal cells of the choroid plexuses 2.Circulate throughout ventricles 3.Exit 4th ventricle 4.Flow in subarachnoid space 5.Reabsorb into venous blood PROTECTION OF THE CNS  Cerebrospinal Fluid (CSF)  Lumbar puncture  Collect CSF from the subarachnoid space Blausen.com staff. "Blausen gallery 2014" PROTECTION OF THE CNS  Blood-brain barrier(BBB)  Isolates CNS neural tissue from general circulation  Formed by network of tight junctions  Between endothelial cells of CNS capillaries  Highly selective blood–brain barrier regulates exchanges between the blood and brain  Allows chemical composition of blood and CSF to differ  Selectively isolate brain from chemicals in blood that might disrupt neural function PROTECTION OF THE CNS  Blood-brain barrier(BBB)  Limits the use of drugs for treatment of CNS Blood Brain Barrier NOURISHMENT OF THE CENTRAL NERVOUS SYSTEM (CNS)  The brain depends on constant delivery of oxygen and glucose by the blood  Only utilizes glucose but does not store it  Cannot produce ATP without O2  2% of body weight but ~ 13% - 15% of cardiac output  Brain damage results if deprived of O2 GENERAL FUNCTIONS OF THE CENTRAL NERVOUS SYSTEM (CNS) 1. Subconsciously regulate homeostatic responses 2. Experience emotions 3. Voluntarily control movements 4. Perception of body and surroundings 5. Engage in other higher cognitive processes COMPONENTS OF THE BRAIN  Brain stem  Cerebellum  Forebrain  Diencephalon  Hypothalamus  Thalamus  Cerebrum  Basal nuclei (Basal ganglia)  Cerebral cortex Fig. 5-7, Sherwood OVERVIEW OF STRUCTURE AND FUNCTION OF THE BRAIN Table 5-1, Sherwood OVERVIEW OF STRUCTURE AND FUNCTION OF THE BRAIN Table 5-1, Sherwood LOBES OF THE CEREBRAL CORTEX  The four pairs of Motor functions lobes in the cerebral Somatosensory processing cortex are specialized for different activities Prefrontal - complex cognitive, decision making, personality, social behavior Memory formation Visual Fig. 5-10, Sherwood SENSORY AND MOTOR HOMUNCULUS  Somatotopic map  Relative proportion of somatosensory cortex devoted to reception of sensory input from each area  Distribution of motor output from the primary motor cortex to different parts of body  Precise distribution is unique for each individual  Use-dependent modification Fig. 5-12, Sherwood SPINAL CORD  Long, slender cylinder of nerve tissue  Extends from the brain stem  Extends through the vertebral canal and is connected to the spinal nerves  Enclosed by the protective vertebral column  The white matter is organized into tracts  Bundles of nerve fibers with a similar function SPINAL CORD DERMATOMES  Area of skin supplied by a single spinal cord level, or on one side, by a single spinal nerve  Can be used to localized lesions to a specific spinal nerve or specific spinal level  Knowledge useful for neurological examination DERMATOMES MYOTOMES  Portion of a skeletal muscle innervated by a single spinal cord level, or on one side, by a single spinal nerve  Each skeletal muscle usually innervated by nerves from more than one spinal cord level  Testing movements at successive joints to help in localizing nerve or spinal cord lesions  Eg, shoulder joint innervated by C5 & C6 spinal nerves Fig. 1.38, Grey’s Anatomy for Students SPINAL NERVES T1 – L2  Ramus – branch  Anterior ramus – anterior branch of spinal nerve Sensory Motor Fig. 13.8, Martini SPINAL NERVES T1 – L2  Ramus – branch  Anterior ramus – anterior branch of spinal nerve Sensory Motor Fig. 13.8, Martini NERVE PLEXUSES  Simple distribution pattern of posterior and anterior rami applies to spinal nerves T1 – L2 (Previous 2 slides)  Network of nerves that come together and then redistribute themselves out with a different distribution of nerves into the limbs Fig. 13-9, Martini NERVE PLEXUSES  Either somatic or visceral  Combine fibers from different sources or level to form new nerves with specific targets or destinations  Each nerve exiting the plexus may contain fibers from different spinal nerves  Damage to a single spinal nerve is less likely to result in total paralysis of a muscle innervated by nerves from that plexus Fig. 16-6, Martini NERVE PLEXUSES Fig. I-40; Moore’s Clinically oriented anatomy REFERENCES  Chapter 5 Sherwood, L. (2016) Human Physiology: From Cells to Systems. 9th edition. Cengage  Chapter 13, 14, 16 Martini, F. H., Nath, J.L., & Bartholomew, E. F. (2018). Fundamentals of Anatomy and Physiology. 11th Global Edition. Pearson.  Chapter 1 Drake et al. (2015) Grey’s Anatomy for Students 3rd Edition. Elseiver.  Moore et al. (2015) Moore’s Clinically Oriented Anatomy 7th Edition. Elseiver. HSC1007 ANATOMY AND PHYSIOLOGY 1 INTRODUCTION TO NEUROSCIENCE 2 MOLECULAR AND CELLULAR NEUROBIOLOGY ANDY LEE (PHD) ASSISTANT PROFESSOR FACULTY HALL #04-17 OFFICE PHONE: 6592 2524 [email protected] LEARNING OUTCOMES At the end of the lesson, you should be able to:  Describe the structure and function of neurons and glial cells  Explain the generation and maintenance of the resting membrane potential  Describe the generation and propagation of an action potential  Explain the significance of the myelin sheath  Describe the structure of the synapse and synaptic transmission  Appreciate the major neurotransmitters and their effects on post synaptic membranes NEURON STRUCTURE AND FUNCTION NEURONS  The basic functional units of the nervous system  Conducting cells of the nervous system Axon  Processes and transmit information (electrical and chemical)  Structure of neurons Cell Body  Cell body (soma) Dendrite  Contain organelles essential for their survival (nucleus, mitochondria, RER etc)  Short, branched dendrites  Highly branched  Receive information from other neurons  Long, single axon  Carries electrical signal (action potential) to target Fig. 12-2; Martini et al. NEURONS Fig. 12-3; Martini et al. PERIPHERAL NERVES Fig. 13-6; Martini et al. NEUROGLIA  Supporting neuronal function  ~50% of total cell population in the nervous system  Astrocytes  Regulating chemical content of the extracellular space  Myelinating glia  Oligodendrocytes (CNS) and Schwann cells (PNS)  Microglia  Phagocytic role (remove cell debris, wastes etc)  Ependymal cells  Production of CSF INTRODUCTION TO NEURAL COMMUNICATION  Nerve and muscle cells are excitable tissues  Produce electrical signals when excited  Neurons use these electrical signals to receive, process, initiate, and transmit messages  Muscles cells – electrical signals initiate contraction  Electrical signals are critical to the function of the nervous system and all muscles INTRODUCTION TO NEURAL COMMUNICATION  Membrane potential becomes less negative during +20 depolarization and more +10 Depolarization (decrease in potential; negative during 0 membrane less negative) hyperpolarization Membrane potential (mV) –10  Polarization: membrane Repolarization (return to resting potential –20 potential is not 0 mv after depolarization) –30  Depolarization: potential –40 Hyperpolarization (increase in becomes less polarized than –50 potential; membrane more negative) resting potential –60  Repolarization: potential returns –70 Resting potential to resting potential after having –80 been depolarized –90  Hyperpolarization: potential becomes more polarized than Time (msec) resting potential Fig. 4-1; Sherwood RESTING MEMBRANE POTENTIAL Fig. 3-22; Sherwood INTRODUCTION TO NEURAL COMMUNICATION  Electrical signals are produced by changes in ion movement across the plasma membrane Voltage gated  An event triggers a change in Leaky channels Membrane Chemically membrane potential (triggering channels gated event) Gated channels Mechanically  Alters the membrane gated permeability and consequently alters ion flow across the Thermally gated membrane GRADED POTENTIALS  Graded potentials are local changes in membrane potential  Occur in varying grades or degrees of magnitude or strength  The stronger a triggering event, the larger the resultant graded potential  Spread by passive current flow  Current: any flow of electrical charges  Resistance: hindrance to electrical charge movement  Die out over short distances Fig. 12-11; Martini ACTION POTENTIALS ACTION POTENTIALS  Action potentials: brief, rapid, large (100-mV) changes in membrane potential  Potential actually reverses  Inside of the excitable cell transiently becomes more positive than the outside  Marked changes in membrane permeability and ion movement lead to an action potential  Voltage-gated Na+ and K+ channels  Changes in permeability and ion movement during an action potential Fig. 4-4; Sherwood IONS CHANNELS INVOLVED IN THE GENERATION OF ACTION POTENTIALS Fig. 4-4, 4-5; Sherwood ACTION POTENTIALS Fig. 4-6; Sherwood ACTION POTENTIALS 1 Resting potential: all voltage-gated channels closed. 2 At threshold, Na+ channel opens (activated) and PNa+ rises. Na+ enters cell, causing explosive depolarization to +30 mV, which 3 generates rising phase of action potential. At peak of action potential, Na+ channel inactivated, PNa+ falls, ending net 4 movement of Na+ into cell. At the same time, K+ channel opens and PK+ rises. K+ leaves cell, causing its repolarization to resting potential, which 5 generates falling phase of action potential. On return to resting potential, Na+ channel resets to “closed but capable of 6 opening” state , ready to respond to another depolarizing triggering event. Further outward movement of K+ through still-open K+ channel briefly 7 hyperpolarizes membrane, which generates after hyperpolarization. 8 K+ channel closes, and membrane returns to resting potential. ACTION POTENTIALS  Na+–K+ pump gradually restores concentration gradients disrupted by action potentials  At the completion of an action potential, membrane potential has been restored to resting  Ion distribution has been altered slightly  Action potentials are propagated from the axon hillock to the axon terminals Fig. 3-16; Sherwood ACTION POTENTIALS ACTION POTENTIALS Fig. 4-7; Sherwood ACTION POTENTIALS  Once initiated, action potentials are conducted throughout a nerve fiber  Refractory period ensures one- way propagation of action potentials and limits their frequency  Action potential cannot be initiated in a region that has just undergone an action potential Fig. 4-9; Sherwood REFRACTORY PERIOD Fig. 12-13; Martini ACTION POTENTIALS  Occur in all-or-none fashion  Discrimination of stimuli  Weak stimuli do not initiate AP  Strength of a stimulus is coded by the frequency of action potentials  Remember that magnitude of each AP is the same  Myelination increases the speed of conduction of action potentials  Fiber diameter influences the velocity of action potential propagation MYELINATION  Myelin – thick layer of lipids  Act as an insulation to “electrical transmission” along the axon Fig. 4-11; Sherwood SALTATORY CONDUCTION Contiguous conduction Saltatory conduction Fig. 4-8, 4-12; Sherwood SYNAPSES  Synapse: junction between neurons  Electrical synapses: neurons connected directly by gap junctions  Chemical synapses: chemical messenger transmits information one way across a space separating the two neurons  Most synapses in the human nervous system are chemical synapses SYNAPSES  ANATOMY OF A CHEMICAL SYNAPSE Fig. 5.4, Neuroscience: Exploring the brain 1. Presynaptic terminal | 2. Synaptic cleft | 3. Postsynaptic terminal SYNAPTIC TRANSMISSION 1. Depolarization 3. Docking 2. Influx of calcium 4. Release of neurotransmitter 5. Binding of nt to receptor EXAMPLE OF A CHOLINERGIC SYNAPSE Fig. 12-16; Martini SYNAPSES AND NEURONAL INTEGRATION Fig. 4-13, 4-7; Sherwood SYNAPSES AND NEURONAL INTEGRATION +30 Membrane potential (mV) in postsynaptic neuron  Neurotransmitter carries the signal across a 0 synapse Activation of synapse Threshold –50  Receptor channels: combined receptor and channel EPSP potential –70 units 5 15 25 35 45  Some synapses excite, whereas others inhibit, Time (msec) (a) Excitatory synapse the postsynaptic neuron  Excitatory synapses – generation of EPSP +30 Membrane potential (mV) in postsynaptic neuron  Inhibitory synapses – generation of IPSP 0  Neurotransmitter–receptor combinations always –50 Activation of synapse Threshold potential produce the same response –70 IPSP 5 15 25 35 45 Time (msec) (b) Inhibitory synapse Fig. 4-15; Sherwood SYNAPSES AND NEURONAL INTEGRATION  Drugs and diseases can modify synaptic transmission  Most drugs that influence the nervous system function by altering synaptic mechanisms  Neurons are linked through complex converging and diverging pathways  Convergence: given neuron may have many other neurons synapsing on it  Divergence: branching axon terminals so a single cell synapses and influences other cells SOME NEUROTRANSMITTERS Neurotransmitters Functions Acetylcholine Many varied effects and functions. PNS: Neuromuscular junctions, parasympathetic nerves CNS: Muscarinic and ionotropic (ligand gated ion channels; EPSP) Dopamine Involved in many pathways (such as muscle movement and reward pathway) in CNS Glutamate Primary excitatory neurotransmitter in CNS (EPSP) Gamma- Primary inhibitory neurotransmitter in CNS (IPSP) aminobutyric acid (GABA) REFERENCES  Chapter 3 and 4 Sherwood, L. (2016) Human Physiology: From Cells to Systems. 9th edition. Cengage  Chapter 12 Martini, F. H., Nath, J.L., & Bartholomew, E. F. (2018). Fundamentals of Anatomy and Physiology. 11th Global Edition. Pearson.