BSCI 201 Review Sheet Final Exam The Nervous System CNS and PNS Define the following o Central nervous system consist of the brain and the spine located in the dorsal body cavity surrounded by meninges o Peripheral nervous system consists of all neural structure outside the CNS including the cranial nerves spinal nerves and sensory receptors o Nissl body well developed rough endoplasmic reticulum protein synthesis o neurofilaments intermediate filaments provides tensile strength o ganglia a cluster of neuron cells bodies in the PNS o nuclei a cluster of neuron cell bodies in the CNS o tract a bundle of axons in the CNS o nerve a bundle of axons in the PNS o neurilemma the cytoplasm and the nucleus of the Schwann cell squeezed outside the myelin sheath o nodes of Ranvier spaces between adjacent myelin sheaths o axon wrapped in connective tissue endoneurium a bundle is called a fascicle each fascicle is wrapped in connective tissue perineurium a bundle of perineurium make up a nerve or tract and is wrapped in a connective tissue epineurium Which part of a neuron is known as the o biosynthetic center cell body contain all the cytoplasmic organelles except centrosomes so they are amitotic can t undergo mitosis o receptive center dendrite they receive and convey electrical signals to cell bodies these are not action potentials Name and describe the function of all 6 types of supporting cells o CNS cell debris Microglia act as macrophages to engulf destroy pathogens and Obligodendrocytes their extensions myelinate axons no neurilemma to guide growth of severed axon because it myleinates with extensions presence of growth inhibiting proteins in the CNS inhibit regeneration of a severed axon microglia poorly clean up area of damage Astrocyctes most abundant helps in forming blood brain barrier selective barrier that regulate the chemicals environment of the brain regulate brain function Ependymal cells ciliated columnar cells that line the ventricles and contain cerebrospinal fluid currents created by cilia circulate the fluid Schwann cells myelinate axons of neurons the immune system can regenerate severed axons by cleaning up cell debris a process known as debridement the neurilemma forms a regeneration tube o PNS Satellite cells surround cell bodies of neurons and control their chemical environment Explain why impulses are conducted faster in a larger myelinated axon than in a smaller unmyelinated axon o Meylinated axons use salutatory conduction where action potentials are generated only at the nodes of ranvier hence the impulses jump from node to node down the axon Unmyelinated axons use continuous conduction where action potentials developed stepwise across the entire axolemma Describe the o Depolarization phase of an action potential entry of sodium ions into the cell sodium influx makes the membrane potential less and less negative Threshold potential an all or nothing phenomenon upshot or spike due to an explosive entry of sodium ions positive membrane potential reached o repolarization phase of an action potential sodium channels close and potassium channels open and potassium ions rush out potassium efflux membrane potential becomes more negative o hyperpolarization phase more potassium ions leave the cell driving the membrane potential below the resting membrane potential o absolute refractory phase of an action potential depolarization phase of the action potential when sodium channels are opened another action potential can t be generated o relative refractory phase of an action potential repolarization phase when sodium channels are closed but an exceptionally strong stimulus can cause sodium channels to open to allow for sodium ion influx leading to depolarization and the generation of another action potential Name and describe the 3 structural classes of neurons o Multipolar has one axon and at least two dendrites most abundant neuron in the human body o Bipolar has 1 axon and 1 dendrite and it is seen in eyes and ears o Pseudounipolar has 1 short process from the cell body and it splits into a central process and peripheral process cell body is in the middle sends signals to the CNS Name and describe the 3 functional classes of neurons o Motor or efferent neuron motor division transmits impulses from the CNS to PNS effector organs glands organs muscles motor nerve fibers o Sensory or afferent neuron sensory division transmits impulses from sensory receptors PNS to the CNS somatic and visceral sensory nerve fibers o Association neurons interneurons located in the CNS between the sensory neurons and the motor neurons most neurons in the body are association neurons Name and describe the 3 categories types of nerve fibers which type has the fastest conduction velocity and why o Group A fibers largest diameter which means less resistance to current flow and conduction velocity is high Highly myelinated which means it is salutatory conduction where the impulse is generated at the nodes of Ranvier and the signal jumps from node to node 150m s o Group B fibers intermediate diameter and has a higher resistance than group A It is myelinated so it is salutatory conductor 15m s o Group c fibers smallest diameter and is unmyelinated It has the highest resistance and uses a continuous conductor where the entire surface of the axon has to be depolarized in order to generate an action potential 1 m s o Axons with larger diameter transmit impulses at a faster rate because they have a smaller resistance than axons with a smaller diameter The Brain Name the 4 structures protecting the brain o Cranium bony helmet composed of the 8 cranial bones frontal parietal 2 temporal 2 occipital sphenoid and the ethmoid bone o Meninges 3 connective membranes surrounding the brain Dura mater outermost layer double layered Periosteal layer outer layer layering the internal surface of the cranium Meningeal layer second layer of the Dura mater Arachnoid mater middle layer web like extensions Pia mater innermost layer that clings and follows all contours of the surface of the brain helps nourish the brain and spinal cord o Cerebrospinal fluid filtered from blood located in the ventricles and also the subarachnoid space inside and outside of the brain acts as a liquid cushion provides buoyancy to the brain provides nutrients and removes metabolic wastes o Blood brain barrier selective barrier that prevents harmful substance in blood from crossing to the brain Give the locations of the lateral third and
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