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Cell Functions

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by

Lan Yang

on 18 February 2013

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Transcript of Cell Functions

Description of Cells bounded by cell membrane that controls what leaves/enters cell
cytoplasm-liquid like substance inside membrane that contains important functional structures
nucleus-structure in cytoplasm which contains chromosomes (nucleolus makes ribosomes)
what occurs in nucleus:
1. DNA housed in the chromosomes (DNA-RNA-protein)
2. ribosomes part of mechanics; involved w/RNA to make proteins
3. proteins crucial to life; can be used to make enzymes that control chemical reactions in body
mitochondria-makes energy by breaking up nutrients to form ATP (adenosine triphosphate)
endoplasmic reticulum-2 types
1. rough-contains ribosomes-used to make proteins
2. smooth-transports substances within cells
golgi apparatus-wrapper for substances that will be excreted outside cell-hits membrane and NT or hormones are released; contains lysosomes that break down substances no longer needed
microfilaments-give cells shape
microtubules-1. give motive force to cells that move (sperm); 2. transport substances within cells Neurons neurons (nerve cells) process, transmit info w/in nervous system
many types of neurons which differ in diff ares of brain, spinal cord, and PNS
4 basic physiological structures of neurons: body (soma), dendrites, axon, and terminal buttons
soma-cell body, contains nucleus and cytoplasm & varies considerably in types of neurons
dendrites-tree like branches extending from neuron to receive messages from other neurons through other neurons' axons; 2. msgs transported from one neuron to another over junction called synapse
axon-long slender tube carries info away from soma to terminal buttons and then synapse
-covered in myelin sheath (serves as insulation and speeds up transmission; disease like MS destroys myelin and reduces efficiency of neural communication-develop sensory/motor/and cog problems)
-carries msg called "action potential"-electrical or chemical event that starts at axon near soma and travels towards terminal button; action potential always same size and duration (has voltage) Neurons cont. classification of neurons-based on the way their axons and dendrites leave the soma
1. multipolar-one axon, many dendrites
2. bipolar-one axon, one dendrite-opposite ends of soma
3. unipolar-one stalk which divides into axon and dendrites-mostly for sensory purposes
terminal buttons-knob at end of branch
-fx: when action potential travels down axon and reaches terminal button, they secrete NT's and others
-release NT into synapse to be received by other cells dendrites-neural communication
-NTs can either excite or inhibit receiving cells-this determines whether or not receiving cells will start its own action potential and fire
-e.g. DA theory of schizophrenia (meds attempt to reduce NT's and thus communication and firing) Supporting Cells Cell Functions includes description of cells, neurons, & supporting cells 1. 2. 3. axon dendrite Neuron classification images needed in nervous system in both CNS and PNS
neurons don't store energy cuz of their high metabolic rates-supporting cells provide energy for neurons
glia-multiple types exist
1. functions:
-hold neurons in place (nerve glue hold columns in place)
-control supply of chemicals into neurons
-insulation/buffer to neurons-prevent NTs from dispersing
-clean up dead cells-cells divide and clean up dead neurons ( like pacman)and remain in neurons' place to become scar tissue
-frequent cell type for brain tumor (neurons typically don't become tumors)
-smaller and eat up debris of dead neurons
-make myelin: 80% lipid (fat), 20% protein,
myelin insulates axons however there are nodes called nodes of Ranvier that speeds up transmission and aren't insulated Schwann Cells found only in PNS-support in PNS
produces myelin
cleans up dead neurons
a. permit regeneration of neurons in PNS by encapsulating dead end portion of the neuron and allowing the live portion to resprout through it-chemically stimulate "elongation" of dead portion of neuron
b. if dead neuron is too big-neurosurgery can take neurons from other areas of PNS place it in section which will grow under direction of Schwann cells
c. neurons do not regrow in CNS cuz they're stopped by scar tissue & glia cells don't produce chemicals necessary for re-elongation of neurons
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