Functions of the Nervous System Receiving sensory input Chapter 11 Nervous System o Monitor internal and external stimuli o what leads to signaling a receptor and call for homeostatic activity o Brain and spinal cord process sensory input and initiate responses Integrating information Controlling muscles and glands Maintaining homeostasis o Regulate and coordinate physiology Establishing and maintaining mental activity o Consciousness thinking memory emotion Divisions of the Nervous System Components o Brain o Spinal cord o Nerves o Sensory Receptors Subdivisions o Central nervous system CNS brain and spinal cord o Peripheral nervous system PNS sensory receptors and nerves contains both sensory and motor fibers Peripheral Nervous System Sensory receptors o ending of neurons or separate o f x specialized cells that detect such things as temperature pain touch pressure light sound odors Nerve muscles and glands o a bundle of axons and their sheaths that connects CNS to sensory receptors o Cranial nerves originate from the brain 12 pairs o Spinal nerves originate from spinal cord 31 pairs o Collection of neuron cell bodies o Located outside CNS o Extensive network of axons and neuron cell bodies Ganglion Plexus Located outside CNS Divisions of Peripheral Nervous System Sensory afferent o transmits action potentials from receptors to CNS receptor to Control Center Motor efferent o Somatic fibers impulses from skin skeletal muscles and joints to the brain o Visceral fibers impulses from visceral organs to the brain o transmits action potentials from CNS to effectors o Effectors muscles glands control center to effectors Motor efferent Divisions of Peripheral Nervous System Somatic nervous system from CNS to skeletal muscles o Voluntary o Single neuron system VERY IMPORTANT TO KNOW o Synapse junction of a nerve cell with another cell you decide when to contract muscle Example neuromuscular junction and certain glands o Subconscious or involuntary control o Two neuron system First from CNS to ganglion Second from ganglion to effector o Divisions of ANS Autonomic nervous system ANS from CNS to smooth muscle cardiac muscle synapse between a neuron skeletal muscle cell as digesting food or emptying of the urinary bladder Sympathetic Prepares body for physical activity Parasympathetic Regulates resting or vegetative functions such Enteric Plexuses within the wall of the digestive tract Parasympathetic and sympathetic neurons that contribute to the plexi Cells of the Nervous System Neuroglia Support and protect neurons Neurons nerve cells o Functional unit of the nervous system o receive stimuli and transmit action potentials o Organization Parts of a Neuron Cell body soma single nucleus with prominent nucleolus Dendrites input Axons output Neuron Cell Body Soma Dendrites short often highly branched o Everything within Nucleus Nissl substance o rough E R primary site of protein synthesis o Dendritic spines o input of the neuron where axons synapse with dendrite Axons o F x send signal out o Can branch to form collaterals o Axon hillock where the axon begins o Initial segment initial part of the axon o Trigger zone site where action potentials are generated Found in axon hillock When neuron has to send a signal it ll start in trigger zone Signal will always be electrical in nature o Axoplasm plasma of axon o Axolemma tissue that surrounds axon o Presynaptic terminals end of axon o Synaptic vesicles goublets that contain neurotransmitter that will take action potential to CNS Organization of Nervous Tissue Gray matter o unmyelinated axons o FIND THE SOMA cell bodies Dendrites neuroglia White matter o Integrative functions o myelinated axons o FIND THE AXONS In brain to another o Outer gray o Inner white o Outer white o Inner gray In Spinal Cord Nerve tracts propagate action potentials from one area in the CNS PNS gray matter is groups of cell bodies called ganglia KEY Electrical Signaling Action Potential electrical signal produced by cells Transfer of information from one part of body to another o Sensory receptor receives information action potential o Action potential propagates to Sensory neuron ganglia o Sensor Neuron to Control Center o Control center integrates information decides what to do and sends signal to o Action Potential action is preformed on OPPOSITE SIDE effector Electrical properties result from ionic concentration differences across plasma So to write with right hand signal comes from the left membrane and permeability of membrane Permeability of Plasma Membrane Proteins decide what can enter o Synthesized inside cell Large don t dissolve in phospholipids of membrane Proteins are negatively charged Cl are repelled by proteins o Negative in nature Gated ion channels Stimulus will open and close o open they change the permeability of the cell membrane o Ligand gated molecule that binds to a receptor protein or glycoprotein EX Ach Binding Acetylcholine binds to acetylcholine receptor on a Na channel o Voltage gated open or close in response to small voltage changes across Channel opens Na enters the cell the cell membrane gated ion channels either open or close At rest membrane negative inside and positive outside When cell is stimulated that relative charge changes and voltage Most common voltage gated are Na and K MAINTAINS ACTION POTENTIAL In cardiac and smooth muscle Ca2 important Touch receptors respond to mechanical stimulation of the skin Temperature receptors respond to temperature changes in the skin Establishing Resting Membrane Potential Negative inside of cell membrane Positive ions along outside Potential energy difference at rest is 70 mV Resting potential exists because o 1 Concentration of ions different inside outside o 2 membrane permeability differs for Na and K Extracellular fluid rich in Na and Cl Cytosol full of K organic phosphate amino acids negative 50 100 greater permeability for K Inward flow of Na can t keep up with outward flow of K Na K pump removes Na as fast as it leaks in Changing Resting Membrane Potential Depolarization Potential difference becomes smaller or less polar o 70mv to 0 MORE POSITIVE o Increase of Sodium in axon Hyperpolarization Potential difference becomes greater or more polar o More Negative inhibit action potential o Increase of Potassium in axon increase negativity Action Potential is All or Nothing All or none principle Must be greater than threshold for action potential to occur Threshold 55 mv doesn t matter how strong
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