ANPH111 Nervous Tissue Midterm PDF

ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES ○ Contraction of skeletal CHAPTER 12: NERVOUS TISSUE...

ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES ○ Contraction of skeletal CHAPTER 12: NERVOUS TISSUE muscle. Not always A OVERVIEW OF NERVOUS SYSTEM voluntary (conscious decision) FUNCTION OF NERVOUS SYSTEM ○ Reflexes ★ Sensation - receiving Often happens information without conscious ★ Integration - combining decision. sensory information with AUTONOMIC higher cognitive functions. ★ Involuntary ○ Association areas ○ For the sake of accomplish this function. homeostasis ★ Response - motor functions ★ Cardiac Muscle, Smooth carried out by effectors. Muscle and Glands. ★ Both conscious and ○ Contraction of smooth unconscious nervous muscle linings, intestines, pathways exist. and changes in respiration rate. MOTOR DIVISION ★ Control the actions of the organ systems of the body to CLASSIFICATION OF PERIPHERAL preserve homeostasis. NERVOUS SYSTEM AUTONOMIC NS DIVISION SOMATIC ★ Voluntary ★ Sympathetic Division EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES ○ fight and flight ★ Glial Cells - cells that provide ★ Parasympathetic Division structure and support to ○ rest and digest neurons. ○ Glue cells ○ Replicates B NERVOUS TISSUE AND CELLS ○ Incapable of communication THE CENTRAL AND PERIPHERAL ANATOMY OF NEURONS NERVOUS SYSTEMS ★ Responsible for CENTRAL NERVOUS SYSTEM communication within the ★ Brain and spinal cord nervous system. ★ Housed within the cranial ★ Cell Body - houses organelles cavity and vertebral like nucleus, nucleolus, cavity. ribosomes, and endoplasmic PERIPHERAL NERVOUS SYSTEM reticulum. ★ Nervous outside the ○ Endoplasmic Reticulum - brain and spinal cord manufactures protein. ★ Outside of bony Where protection. neurotransmitters NERVOUS TISSUE AND CELLS are found. ★ Dendrites - receives signals ★ Neurons - capable of from other neurons. communication. ★ Axon - begins at axon hillock ○ Do not replicate ○ Send signals to other neurons. EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES ○ Each neuron has one ○ Most sensory neurons axon. ★ Bipolar Neuron - two ★ Axon hillock - portion before processes. the axon. ○ One dendrite, one axon ★ Myelin Sheath - fatty ○ Extends from the cell insulation that wraps the axon. body. ★ Node of Ranvier (Neurofibril ○ For smell and vision Node) - gaps between the ○ Rare myelin coverings. ★ Multipolar Neurons - many ★ Synapse - junctions where dendrites and one axon neurons communicate with ○ Majority of neurons in the other cells. body. ★ Axon Terminals - multiple ○ Common axon branches. ○ Allows a single neuron to FUNCTIONAL DIVISIONS OF NERVOUS communicate with SYSTEM OF NERVOUS TISSUE multiple cells. ★ Presynaptic Terminal - where ★ Sensory - sends information the signals are from towards CNS ★ Post-synaptic Terminal - ○ AFFERENT (SENSORY) receiver of the signal NEURONS ★ Integration - occurs in brain and spinal cord CLASSIFICATION OF NEURONS ○ Interneurons ★ Unipolar Neurons - single ★ Response - communicates process that splits into an axon with effectors and dendrites. 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SALES ○ Effector - muscle or FUNCTIONAL CLASSIFICATION OF organs that responds NEURONS ○ Achieved via efferent ★ Sensory Neurons (motor neurons) ○ Afferent neurons ○ collect and send SENSORY DIVISION information to the Central Nervous System. ★ Send information toward the ○ Transmit impulses from integration location, and sensory receptors responses are sent out. toward the central ★ Integration - occurs in the nervous system. brain and spinal cord. ○ Mostly unipolar NEURONS ★ Interneurons ○ Association neurons ★ Sensory neurons that bring ○ Impulse moves between sensory information. sensory and motor ★ Afferent - to, or toward neurons. ○ Sensory Division ○ Mostly multipolar ★ Efferent - away or exiting ○ integrate and process ○ Exits the brain to information from sensory peripheral section neurons. ○ Motor Division ★ Motor Neurons ★ Effector - muscle or organ that ○ Efferent neurons responds ○ Impulse moves from the CNS to the rest of the body. EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES ○ communicate with ★ Star-shaped effectors to make them ★ Most abundant perform an action. ★ Form blood brain barrier (BBB) ○ Mostly multipolar ○ Keeps molecules (e.g., H2O, O2, CO2) from getting into the central GLIAL CELLS nervous system. ★ Supportive cells found ○ Neurons to capillaries throughout the nervous ○ Block substances system. needed for brain tissue ★ Can multiple and divide healing that usually ★ Glial cells of the central cause tumors. nervous system. ○ Glucose or amino acids ○ Astrocyte can pass through the ○ Oligodendrocytes BBB. ○ Microglia MICROGLIAL CELLS ○ Ependymal Cells ★ Immune defense against ★ Glial Cells of The Peripheral invading microorganisms. Nervous System ★ Helps remove bacterias and ○ Satellite Cells cell debris from the central ○ Schwann Cells nervous system. ★ Originate from macrophages (leukocyte) GLIAL CELLS EPENDYMAL CELLS CENTRAL NERVOUS SYSTEM ★ Create, secrete, and circulate cerebrospinal fluid. ASTROCYTE EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES ○ Ventricles - where ★ Allows axon to conduct cerebrospinal fluids are electrical signals faster produced. ★ Oligodendrocytes in CNS OLIGODENDROCYTE ○ Multiple processes ★ Produce an insulating barrier myelinate in different called myelin sheath. areas. ★ Insulates axons ★ Schwann (Neurilemma) cells in PNS ○ Singular cells myelinate GLIAL CELLS each section. PERIPHERAL NERVOUS SYSTEM ★ Nodes of Ranvier ○ Gaps in myelin sheath SATELLITE CELLS where action potentials ★ Regulate extracellular develop. environment. ★ Saltatory Conduction ★ Cluster around cell bodies ○ Jumping of action ★ Similar in function to astrocytes potentials of CNS. ★ Myelinated axons conduct SCHWANN CELLS action potentials more quickly ★ Myelination (3-15 meters/sec) than ★ Similar in function to unmyelinated axons due to the oligodendrocytes of CNS. Nodes of Ranvier. ○ Multiple Sclerosis - MYELIN SHEATH disease of myelin sheath that causes loss of ★ Insulation for axons muscle function. EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES ★ IMPULSE -> INFORMATION -> ○ Different charges can EFFECTOR CELL build up inside and outside of neurons. ★ Sodium-potassium pumps C NEUROPHYSIOLOGY play a key role. ○ Pumps 3 sodium out of COMMUNICATION WITHIN THE the cell and 2 NERVOUS SYSTEM potassium ions inside the cells. ★ Once a stimulus is detected, ○ Creates a relatively communication depends on negative internal electrical signaling. environment of neuron ○ Occurs due to the ○ Membrane becomes movement of ions polarized. ○ Ion movements In and out of the generate action cell have potentials. different ○ Action potentials lead to charges. release of neurotransmitters. RESTING MEMBRANE POTENTIAL Chemicals that relay messages ★ Resting membrane potential from neurons. of neuron is -70 mV ★ Established by: MEMBRANE POTENTIALS ○ Unequal distribution of ★ The cell membrane is a Na+ and K+ ions barrier to ionic movement. across cell membrane EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES From activities of CHANGES IN RESTING MEMBRANE sodium/potassiu POTENTIAL m pumps. ★ As ions flow into and out of ○ Negatively charged neurons , membrane proteins inside of cell potential changes. Make the interior ○ Depolarizing - charge of the neuron difference decrease more negative. ○ Hyperpolarizing - ○ Exit of K+ ions due to charge difference leak channels. increase Further loss of ★ Repolarization positive charges ○ Occurs if from the interior depolarization is of the cell. followed by a return to a polarized state. THE SODIUM-POTASSIUM PUMP ○ Changes can be caused by ion ★ Plays a critical role in resting channels that allow membrane potential of ions to move. neurons. ○ Some channels are ★ Pumps 3 sodium ions out of open and allow ion to the cell and 2 potassium freely move. ions into the cell. ○ Some channels open ○ Build chemical and and close in response electrical gradients to various stimuli. across membranes. EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES CLASSES OF MEMBRANE CHANNELS GRADED POTENTIALS ★ Ligand-gated channels - ★ Small changes in resting open and close due to membrane potential varies binding of a molecule in size. (ligand). ★ Caused by ★ Mechanically-gated mechanically-gated and channels - open and close ligand-gated membrane in response to pressure. channels. ○ Detected by ★ Occur along dendrites and distortions in cell the cell body. membranes. ★ Membrane channels open to ★ Voltage-gated channels - allow sodium ions to enter open and close in response neurons. to changes in electric ★ Depolarization occurs as the potential. inside of the neuron ○ A change in becomes more positively membrane potential charged. can open or close ★ Summation voltage-gated ○ Graded potentials are channels. additive. ★ Leak channels - always ○ smaller graded open or randomly opened potential can add and closed. together. ○ No single stimulus ★ Depolarization influences their ○ Move membrane activity. toward threshold. EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES ○ Sodium or Calcium ○ Inhibitory (IPSP) - usually enters neurons. moves membrane ★ Hyperpolarization away from threshold ○ Move membrane Decreases away from threshold voltage ○ Potassium may exit or E.g., GABA (Cl-) Chlorine enters neuron Hyperpolarizes ★ If threshold is reached, membrane action potential is guaranteed to move down SUMMATION OF GRADED the axon. POTENTIALS ★ Threshold value: -55 mV ★ Spatial Summation - TYPES OF GRADED POTENTIALS graded potentials occurring ★ Post-synaptic potential at several different synapses (PSP) - graded potentials over a short time frame. occurring in neurons that ★ Temporal Summation - received signals. graded potentials occur at ○ Excitatory (EPSP) - one synapse over a short moves membrane time frame. toward threshold. Increases THE ACTION POTENTIALS voltage E.g., Glutamate ★ Begins at axon hillock and (Na, K) travels down the axon Depolarizes terminals. membrane EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES ★ Membrane channels in ★ At +30 mV, sodium-voltage dendrites and cell body gated channels close and respond to stimuli potassium-voltage gated ○ Produced gated channels no longer enter the potentials neuron and potassium ○ Depolarizing graded begins to exit. potentials allow ○ Begins repolarization. positively charged ★ Repolarization reestablishes sodium ions to enter resting membrane potential. neurons. ○ Potassium exits via ★ Depolarization occurs as potassium-voltage sodium ions make the gated channels. interior of neurons more ○ Membrane potential positively charged. becomes more ★ If graded potentials negative as a result of depolarize the cell body to loss of potassium. threshold, action potentials ○ Membranes may are generated. hyperpolarize as ○ Threshold is -55 mV excess potassium ★ Once the threshold is exits. reached, voltage-gated ★ Sodium-potassium pumps sodium and potassium will bring membrane channels open. potential back to -70 mV by ○ Sodium enters rapidly removing sodium from the and depolarizes cell and pumping potassium neurons. back into the cell. EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES REFRACTORY PERIOD ○ Sodium voltage-gated channels open and ★ Period after an action sodium ions flow into potential is generated and neurons. before another can begin. ○ Each section of the ○ Absolute Refractory axon depolarizes in Period - no action sequence. potential possible. ○ Relative Refractory Period - second action PROPAGATION OF AN ACTION potential possible with POTENTIAL DOWN A MYELINATED strong stimulus. AXON Membrane ★ Propagation is saltatory potential must conduction be -55 mV AND ★ Faster than continuous -70 mV. conduction ★ Sodium ions gather at axon PROPAGATION OF AN ACTION hillock POTENTIAL DOWN AN ★ Sodium ions move toward UNMYELINATED AXON axon terminals ★ Only depolarize neurofibril ★ All or nothing event nodes ★ Propagation in ○ Myelinated areas lack unmyelinated axons is voltage-gated continuous conduction. channels. ○ Sodium ions gather at axon hillock EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES ★ Myelin insulates sections of SYNAPSES axon, preventing loss of ★ Areas where neurons sodium ions. communicate. ○ Chemical synapses - SPEED OF ACTION POTENTIAL release PROPAGATION neurotransmitters ○ Electrical synapses - ★ Speed of action potential direct connections movement is influenced by where ions move from ○ Myelination one cell to another. Faster Less common in conduction in the human myelinated than nervous system. unmyelinated axons. COMPONENTS OF A CHEMICAL ○ Size of electrochemical SYNAPSE gradient ★ Presynaptic cell ○ Diameter of axon ★ Neurotransmitter Faster in larger ★ Synaptic cleft axons ★ Receptors for Larger axons neurotransmitter have less ★ Post-synaptic cell resistance to ion ★ A system for clearing movement. neurotransmitters from synapse. C COMMUNICATION BETWEEN NEURONS EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES SYNAPTIC EVENT ★ Categories of neurotransmitters: ★ Action potential reaches ○ Cholinergic - axon terminal. acetylcholine ★ Calcium-voltage gated ○ Amino acid - channels open glutamate, GABA ★ Calcium enter synaptic bulb (inhibitory), glycine ★ Calcium causes synaptic ○ Biogenic amines - vesicles to fuse with synaptic serotonin, dopamine, end bulbs. epinephrine, ★ Neurotransmitter is released. norepinephrine. ○ Neurotransmitter binds ★ Effects depends on receptor to receptors in ○ Same neurotransmitter postsynaptic neurons can have different Causes graded effects on different potential cells. ○ Neurotransmitter eliminated from synapse by: CHOLINERGIC Diffusion Reuptake ★ acetylcholine is released by Breakdown cholinergic neurons. ★ Acts on two types of receptors: NEUROTRANSMITTER ○ Nicotinic receptors - found at NMJ, adrenal ★ Each neuron only releases medulla, and some one neurotransmitter. autonomic synapses. EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES ○ Muscarinic receptors ★ GABA leads to IPSPs - found at autonomic ○ Receptors are Cl- synapses. channels that ★ Elimination by hyperpolarize acetylcholinesterase membranes. ○ Enzyme that breaks down acetylcholine. BIOGENIC AMINE ★ Decrease in ACh = Alzheimer’s disease ★ Made from amino acids ○ Serotonin - appetite and digestion AMINO ACIDS regulation, mood, etc. ★ Include: SSRIs - used to ○ Glutamate - learning treat anxiety and and memory depression. ○ Gamma-aminobutyri ○ Dopamine - reward c acid - principal system inhibitory ○ Norepinephrine - neurotransmitter of mood and regulation the nervous system of organ function ○ Glycine - spinal cord ○ Epinephrine ★ Released by glutamatergic, ○ Each has its own GABAergic, and glycinergic membrane receptors neurons. ○ Elimination from ★ Each has its own receptors synapse by reuptake ★ Eliminated from synapses by ★ Serotonin reuptake can be reuptake. blocked by selective EVEN IF YOU GO SLOWLY, IT’S OKAY! : )  ANATOMY & PHYSIOLOGY MIDTERM ANPH111 JENNIFER A. SALES serotonin reuptake inhibitors (SSRIs) ○ Used in treatment of depression and anxiety. EVEN IF YOU GO SLOWLY, IT’S OKAY! : )