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21 Cards in this Set
- Front
- Back
FUNCTIONS OF NERVOUS SYSTEM *all cells exhibit irritability or responsiveness *because of this, all organisms are sensitive to changes or stimuli which may come from within the body or outside the body
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function: to communicate, integrate & coordinate functions of diff. Organs
*this system works in conjunction w/ endocrine system as controlling system |
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Con..Nervous system in animals is capable of : 1.SENSORY INPUT: perceiving stimuli (sensory neurons) 2.INTEGRATION:(interneurons) 3.MOTOR OUTPUT:(motor neruons |
1.sensory receptors monitor changes inside & outside the body. The changes are called STIMULI & the info. gathered sensory input 2.analyzing sensory input ,stores info & makes decisions about what should be done. 3.activating effector, causing muscle contraction or glands to secrete. |
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Nervous System Terminology-Stimulus/Response *STIMULUS: -EXTERNAL: -INTERNAL: |
*any physical or chemical change capable of exciting organism. -temperature, moisture, light, gravity, touch salt concentrations, odors. -temperature, results from amount of food, O2, water, wastes, fatigue, pain, disease. |
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cont. -stimulus is received by receptor=sense organ =a cell or organ having special sensitivity to a certain type of stimulus (energy ). |
2 types of receptors : 1.Exteroreceptors- receptors that sense External stimuli outside body 2. Interceptors: receptors that sense internal stimuli within the body EFFECTOR OR TARGET ORGAN-organ that brings about response. Ex. Muscle or Glands |
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NERVOUS TISSUE:CELLS OF THE NERVOUS SYST. 1.NEURONS=NERVE CELLS 2.GLIAL CELLS(NEUROGLIA)
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1. Carry nerve impulses & are electrically excitable. -A nerve= a bundle of neurons. 2.DO NOT carry nerve impulses, not electrically excitable. FUNCTIONS OF GLIAL CELLS: 1.supportive of neurons (nerve glue) like c.t. 2important in neuron nutrition 3. One type -schwann cell synthesizes myelin 4. phagocytic |
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3 TYPES OF NEURONS 1.SENSORY 2. MOTOR 3.INTERNEURONS |
1.serve to bring the impulse or info. toward brain (if animal has one) 2.carry info. out &away from the brain 3.connect sensory to motor neurons * 99% of the neurons of the human body interneurons. |
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Cont. *neurons differ anatomically *not all neurons look alike *use motor neuron as "typical" neuron |
FLOW OF INFORMATION IN NERVOUS SYSTEM 1.STIMULUS > 2.RECEPTOR> 3.SENSORY NEURON> 4. INTERNEURON> 5. MOTOR NEURON> 6. EFFECTOR ORGAN (MUSCLE) |
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TYPICAL NUERON STRUCTURE *NEURONS=NERVE CELLS serve to carry electrical impulses. They are electrically excitable.
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cont. many types of nerve cells are found in the body. A typical neuron possesses the following characteristic features: 1.dendtrite 2. Cell body w/ nucleus 3.axon 4.axon terminal |
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MYELINATED AXONS *some axons are myelinated (myelin)=increases speed of impulse *myelin is produced by schwann cell, a type of glial cell. *myelin= |
*myelinated neurons=white matter nonmyelinated =gray matter (outer cortex) |
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SALTATORY CONDUCTION & MYELINATED AXONS *myelin causes impulse to jump from one node of ranvier to the next instead of traveling along the nerve cell membrane ion by ion. *the jumping of the impulse is known as SALTATORY CONDUCTION & carries info. much faster than nonmyelinated neurons=CONTINUOUS CONDUCTION. |
*the greater the diameter of the myelinated neuron , the faster the velocity of conduction -up to 120 meters per second. |
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GENERALIZED NERVE CELL (NEURON) COMPONENTS PARTS & FUNCTION 4.AXON TERMINAL is the neuron ending -it contains synaptic vesicles that contain neurotransmitter (chemical messenger) -it carries the message from one neuron to the next across gap called =synapse -or from one neuron to a muscle cell across cap called myoneural junction |
THE NEROVUS SYSTEM MESSAGE *the nervous system message Is ELECTROCHEMICAL in nature . 1. The nerve impulse passes through the neuron as electrical message & 2. Across the synapse as a chemical message *the chemical carries the message across the synapse |
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cont. *the chemical carries the message across the synapse =neurotransmitter = ACh or norepinephrine *the electrical message (120m/sec) along the neuron travels much faster than the chemical message(0.5-1.0 m/sec) across synapse |
CONT. -the nervous system message travels along distinct pathways =nerves unlike endocrine system where the message travels through blood * a nerve is a bundle of neurons bound together by c.t. like wire strand in electrical cable. |
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NEURON COMMUNICATION-THE SYNAPSE *SYNAPSE: *ELECTRICAL SYNAPSES:
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*a gap between neurons or neuron & effector (muscle cell or gland) *nerve impulse travels directly from presynaptic neuron to postsynaptic cell (no chemical neurotransmitter) -can transmit impulse in both directions. (fish) quick response! no chemical to slow down message |
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Cont. *CHEMICAL SYNAPSES: |
*chemical (neurotransmitter) carries message to postsynaptic cell. -neurotransmitter (ACh,norepinephrine)carries slower message in one direction only. -neurotransmitters can be mimicked or effected by drugs or toxins! |
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EFFECTS OF DRUGS/TOXINS *once produced at synapse, ACh continuously broken down by enzyme =ACh esterase to halt message. -neurotoxin parathion(flea spray) prevents breakdown of ACH-flea dies from continual incorrect messages. |
cont. *other neurotoxins bind to neurotransmitter receptor so no messages pass. -ex. pufferfish toxin -people die from paralysis, curare darts *some drugs/toxins mimic neuro. so message is sent but not from brain.(ACH mimic NE=Norep) *" " cause constant Neuro. Release or prevent release of neurotransmitter |
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SIDE NOTE-DRUG ADDICTION *unlike acetylcholine(ACh) , norepinephrine(NE) is recycled *cocaine prevents transport proteins from recycling NE (cocaine blocks recycling) neurotransmitter rises & the firing rate increases. |
cont. *tolerance -the receiving neuron "turns down the volume" by lowering the numbers of receptors.so firing rate returns to normal. *addiction- if cocaine is removed, the level of neurotransmitters falls to normal, too low to fire the reduced number of receptors. |
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NERVOUS SYSTEM *GENERAL TREND-
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*the more complex the organism, the more detailed the nervous system. |
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INVERTEBRATE NERVOUS SYSTEM *UNICELLULAR ANIMALS: *MULTICELLULAR ANIMALS: |
*show irritability, but NO NERVOUS SYSTEM. *(sponges)- cells around openings contract, but is a local response, no message to other cells. Therefore NO NERVOUS SYSTEM. |
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cont. 1. NERVE NET- |
1. Simplest form of nervous system(seen in cnidarians) -more complex nerve nets are found in echinoderms. *both of these groups are radially symmetrical |
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cont. 2. Cephalization & Ganglia 3.BILATERAL NERVE CORDS |
2.aggregations of nerve cells (ganglia) are found in the head region of FLATWORMS & round worms. *appears in bilaterally symmetrical animals 3.(flatworms) |
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Cont. 4. NERVE CORD+SMALL BRAIN +PERIPHERAL GANGLIA 5.NERVE CORD +LARGER BRAIN W/ MORE INTERNEURONS +BILATERAL GANGLIA |
4.-crustaceans,segmented worms, & arthropods 5. cephalopods (octopus, squid) w./ behavior as complex as fish |