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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


function: to communicate, integrate & coordinate functions of diff. Organs



*this system works in conjunction w/ endocrine system as controlling system

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.

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.

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
2 types o

NERVOUS TISSUE:CELLS OF THE NERVOUS SYST.


1.NEURONS=NERVE CELLS


2.GLIAL CELLS(NEUROGLIA)


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

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.

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)

TYPICAL NUERON STRUCTURE


*NEURONS=NERVE CELLS serve to carry electrical impulses. They are electrically excitable.


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

MYELINATED AXONS


*some axons are myelinated (myelin)=increases speed of impulse


*myelin is produced by schwann cell, a type of glial cell.


*myelin=


=segmented sheath of fatty tissue, spaces between schwann cells are called nodes of rainier.


*myelinated neurons=white matter


nonmyelinated =gray matter (outer cortex)

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.

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

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.

NEURON COMMUNICATION-THE SYNAPSE


*SYNAPSE:


*ELECTRICAL SYNAPSES:


*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

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!

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

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.

NERVOUS SYSTEM


*GENERAL TREND-


*the more complex the organism, the more detailed the nervous system.

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.

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

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)

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