Chapter 12 Fundamentals of the Nervous System and Nervous Tissue Exam II Study Guide Functional Anatomy and Physiology Figueroa PET3322 Nervous system o Sensory function receptors o Integrative Function To sense changes in the internal and external environment through sensory To analyze the sensory information store some aspects and make decisions regarding appropriate behaviors o Motor Function To respond to stimuli by initiating action o Central Nervous System CNS Consists of the brain and spinal cord o Peripheral Nervous System Consists of cranial and spinal nerves that contain both sensory and motor fibers also connects the CNS to muscles glands and all sensory receptors Peripheral Nervous System o Sensory Motor Sensory afferent Somatic Fibers o Fibers that send impulses from skin skeletal muscles and joints to the brain Visceral Fibers o Fibers that send impulses from visceral organs to the brain Motor efferent Impulses from the CNS to effector organs o Motor Division Somatic Nervous System How the brain controls the skeletal muscles mostly voluntary Autonomic Nervous System How the brain stimulates muscles other than skeletal smooth muscle cardiac glands o Neurons Nerve Cells Structure Cell body Soma Axon o Receives signals and action potentials from previous neurons and contains nucleus of the neuron o Longest projection of the neuron propagates action potential from soma to the axon terminals can be myelinated Dendrites Axon Hillock Axon Terminals o Receive signals and action potentials from previous neurons also have ligand receptors o Point where the soma and axon connect with each other o Axon terminals store neurotransmitters in vesicles when action potential reaches them calcium enters and the neurotransmitter vesicles are released to the next neuron s dendrites or soma Neurotransmitters are stored in the axon terminals of neurons They are secreted to the next neuron when an action potential reaches the axon terminal and allows calcium to enter forcing the neurotransmitter into the synaptic cleft and binding to ligand gated receptors Can be either excitatory or inhibitory Neurotransmitter Function of Neurons Functional unit of nervous system Have the capacity to produce action potentials Communicate with 2 types of electric signals o Action potentials can travel long distances o Flow of ions through ion channels in cell membrane Schwann cells myelineate wrap around axons in the PNS Myeline increases the speed of nerve impulse transmission down Myelin Sheath the axon Unmyelinated Axons These do not contain Schwann cells The speed of nerve impulse transmission down the axon is slower compared to myelineated axons The Action Potential o Resting Membrane Potential Mostly negative ions inside cell membrane positive ions on outside Resting membrane potential at rest is 70mv Resting potential exists because Extracellular fluid rich in Na and Cl Cytosol full of K organic phosphate and amino acids Stimulus chemical or mechanical causes cell to reach 55mV or Na channels open and Na rushes into the cell 20 000 Na enter cell and change membrane potential to 30mV causing depolarization o 1 Depolarization threshold o 2 Repolarization Na channels close and K channels open K outflow returns potential to 70mV o 3 Hyperpolarization Hyperpolarization can occur if K leaves the cell quickly cell potential K channels then close and the cell returns to 70mV resting membrane Axons of the Central Nervous System o Tracts Axons of different neurons that travel together in bunches are known as Synapses o Presynaptic and Postsynaptic Neurons Presynaptic neurons form synapses with Postsynaptic neurons and have 2 can reach 90mV potential tracts in the CNS types of synapses Electrical Chemical o Axodentric from axon to dendrite o Axosomatic from axon to soma o Synaptic Cleft o Ca2 at axon terminal Gap formed at the synapse between presynaptic and postsynaptic neurons Ca2 enters axon terminal when action the action potential reaches it this causes the axon terminal to release neurotransmitters into the synaptic cleft o Neurotransmitter binding to postsynaptic neuron Effect of neurotransmitter can be excitatory or inhibitory Inhibitory polarizing caused by opening of ligand gated Cl or K channels Excitatory depolarizing caused by opening of ligand gated Na channels o Removal of neurotransmitter Diffusion Move down concentration gradient Enzymatic Degradation Acetylcholinesterase Uptake by neurons Neurotransmitter transporters Chapter 15 The Central Nervous System Central Nervous System Components o Brain and Spinal Cord Cerebral Cortex o Motor Areas o Sensory Areas Primary motor area in precentral gyrus of frontal lobe Control voluntary movements Larger cortical areas exist for detailed motor control Primary somatosensory area is in the postcentral gyrus of the parietal lobe Body regions are mapped to specific brain regions Larger cortical regions represent extensive sensory input from some regions o Primary Motor Cortex Voluntary Movement Motor systems o Carry signals from the CNS to effectors and makes sure that motor output is coordinated for efficient responses Motor Homunculus Larger body parts pictured on the homunculus represent extensive motor output from brain regions Somatic Motor Pathway Skeletal muscles innervated by lower motor neurons located in either the spinal cord or brain stem Direct motor pathways descend from the cerebral cortex to lower The left side of the body is controlled by the right cerebral vertex and vise o Motor Tracts motor neurons Decussation of pyramids versa 1 side of the brain controls mobility of opposite half of the body because 80 of axons cross to the other side only 20 remain on the same side they cross in the decussation of pyramids of the medulla oblongota Corticospinal Pathway o Function o Pathway Control voluntary movement motor control Direct motor pathway that descends from the cerebral cortex to the lower motor neurons Peripheral Distribution of Spinal Nerves o Sensory systems Respond to stimuli by sending signals to the CNS o Integrative Systems within the CNS process and evaluate the sensory information in a process called integration o Motor Systems Carry signals from the CNS to effectors and makes sure that motor output is coordinated for efficient responses Chapter 10 Muscles and Muscle Tissue Structure of Skeletal Muscle o Sarcolemma Plasma membrane o Sarcoplasm cytoplasm o Tendon o Epimysium o Endomysium o Perimysuim o Fasicle o Muscle fiber o
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