Nervous System Part 1: Basic Structure/function

Front 1

Two types of tissue

Back 1

neurons and neuroglia

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dendrites

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small cellular processes that recieve input for nuerons to react to physical/chemical changes

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axon

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longer process/nerve fiber carries info away from cell in form of bio electric signals.

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impulses

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bioelectric signals that allows neurons to communicate (action potentials)

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axons in peripheral nervous system

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nerves

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axons in the central nervous system

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tracts

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more neurons or neuroglia in the brain?

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neuroglia

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synapse

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small space between nueron and cell used to communicate

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send and recieve chemical messages across______ by nuerotransmitters

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synapse

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CNS (Central Nervous system)

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brain and spinal cord

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PNS (Peripheral nervous system)

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cranial and spinal nerves. connects CNS to other body parts

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three general functions of nervous system

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sensory, integrative, motor

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sensory receptors

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end of nuerons in peripheral nervous system. transduce their info into impulses, then along perpheral nerves to CNS.

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what happen to signals in CNS

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Integrated into thoughts, memories, then decisions are sub consciously made and motor occurs.

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effectors

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carry out motor processes of nervous system. outside nervous system and include muscles and glands that are controlled by nerve activity

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somatic nervous system

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communicates voluntary decisions which originate in the CNS and activate skeletal muscles causing contraction

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autonomic nervous system

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communicates decisions from the CNS that conntrol visceral organs like the heart/glands and smoooth muscle. (subconsious)

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every nueron has

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a cell body, axon, and dendrites

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nuerofilaments

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extend to axon and support the cell body

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chromatophilic substance (Nissl bodies)

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in cytoplasm which consits of rough endoplasmic reticulum

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synyaptic cleft

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a space that seprates cells at the end of an axon

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collaterals

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branches which come off axon

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Schwann cells

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nueroglia that ecase axons in a protective sheath. made of myelin which is lipids/proteins

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nuerilimma

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surrounds mylein sheath of schwann cells

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nodes of ranvier

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narrow gaps in the myelin sheath

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how many types of nuerons

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three. they are different because of structural differences. All have impulses that go in one direction

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multipolar neuron

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-many processes arise from its one cell body.only one process is an axon, the rest dendrites.

- in the brain and spinal cord

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bipolar nueron

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only two processes, one arises from either end. one is axon and the other a dendrite.

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unipolar neuron or pseudounipolar

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single process extends from cell body. start out as two processes that merge into one.had two processes. peripheral and central.

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functional differences of neurons

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carry info to CNS, within the CNS, or out of the CNS

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sensory neurons (afferent)

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conduct impulses from peripheral body parts into the CNS. At their distal ends the dendrites have sensory receptors

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interneurons (Association or internuncial)

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in CNS. multipolar and form links with other neurons.

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motor neurons (efferent neurons)

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multipolar and conduct impulses out of CNS to effectors move body parts

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astrocytes

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star shaped cells found between neurons and blood vessels and provide support/stability. aid in metabolism of substances, regulate concentration of ions (ex. potassium), also respond to brain trauma by making certain type of scar tissue which fills spaces and closes gaps in CNS.

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Oliogodencytes

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resemble astrocytes but smaller and with less processes. form in rows along axons. mylenate them axons brain and spinal cord. can mylenate many axons because of its various branches. Produce nerve growth factors.

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microgilia

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small cells with fewer processes than other types of nueroglia.scattered throughout CNS and support nuerons/phagocytize. (IMMUNE SUPPORT)

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ependyma

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cuboidal/colomnar w/ cilia. Form inner lining of central canal that extends down the spinal cord. Also form a porous membrane in brain that fills ventricles and allows for free exchange between cells.

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interstital fluid

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fluid in brain tissue

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cerebrospinal fluid

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fluid in brain ventricles

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choroid processes

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speacialized capilares in the brain which regulate composition of cerebspinal fluid

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satellite cells

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small cuboidal cells which surround cell bodies of nuerons in ganglia. support ganglia.

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Neurons do not divide. So what happens?

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new tissues arises from stem cells. neural progenitor cells are formed then neurons/neurglia.

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In the adult brain, where are neural stem cells found?

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dentate gyrus/ near fluid filled ventricles.

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presynaptic neuron

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the sender which conducts the impulse

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postsynaptic neuron or cell

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recieves input at the synapse. can also be a muscular or glandular cell.

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synaptic transmission

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process by which impulse in presynaptic nueron signals the postsyanptic cell

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True or False. Is synpatic transmission a one way process?

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True

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synpatic knob

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at terminals of axons (dendrites do not have these) have arrays of membrous sacs filled with nuero transmitter molecules.

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What happens when an impulse reaches a snypatic knob?

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voltage sensitive calcium is released from channels and calcium diffuses inward from extracellular fluid. synaptic vesicles within the cell fuse and then release the nuerotransmitters by exttocytosis.

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Once the nuerotransmitter binds to the postsynaptic cell... the action is either ___ or ___

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excitatory (turning process on) or inhibitory (turning process off)

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True or false. A cell membrane is polarized.

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True! A cell membrane is eletrically charged so that the inside is negativelly charged. It is also more permeable to potassium ions than sodium ions

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potassium ions

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major intracellular cation (positive ion)

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sodium ions

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major extracellular cation (positive)

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sodium/potassium pump

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pumps sodium out and potassium into cell

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anions in cell

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phosphate and sulfate

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potential difference

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-70 milivolts. the amount of negativeness in the cell compared to the outside of the cell.

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membrane potential

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the potential difference across a cell membrane measueed in milivolts (mv)

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resting potential

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neuron not sending impulses or responding to other neurons. -70 MV

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action potential

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rapid change in membrane potential. When a neuron conducts a current, there are a series of these occuring in sequence along the axon

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hyperpolarized

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when membrane becomes more negative than the resting potential

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depolarized

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when membrane becomes less negative than resting potential

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threshold potential

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when neurons are sufficiently depolarized (-55 MV)

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What happens when threshold potential is reached?

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An action potential results