The Nervous System Dont get nervous about the nervous system.
Nervous System 1 2013
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Transcript of Nervous System 1 2013
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GENERAL FUNCTIONS:
detects environmental changes (inside andoutside body)
interprets changes responds in order to maintain normal or sufficient
function (homeostasis)
SENSORY INPUT (sensory neurons)(gathers information from internal and external environment)
INTEGRATION (interneurons)
(interprets sensory input)
MOTOR OUTPUT (motor neurons)(responds via effector organs)
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ORGANIZATION:
2 Main Divisions:
1. Central Nervous Systemstructures located indorsal body cavityintegration and commandcentreinterprets sensory input
a) Brain
b) Spinal Cord
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2. Peripheral Nervous Systemstructures locatedoutside CNScontains nerves (bundles of axons) which
extend from brain and spinal cord; connects all parts ofbody (tissue beds) to CNS
i) sensory (afferent) divisionconveys impulses to CNSfrom sensory receptors located in different organs and
tissuesii) motor (efferent) divisionconveys impulses from CNSto effector organsmotor responses and secretion byglands in response to sensory information
a) Cranial Nervescarry impulses directly to and frombrain
b) Spinal Nervescarry impulses to and from spinalcord
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motor division is further sub-divided into:
a) somatic nervous systemvoluntary motor
controlb) autonomic nervous systeminvoluntary motorcontrol
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1. Somatic Nervous System
governs voluntary(conscious) actions
involves the brain and cranial or spinal nerves
effectors skeletal muscles2.Autonomic Nervous System
governsinvoluntary(unconscious)activity
involves the brain/brain stem, cranial and spinalnerves
effectors: glands, smooth muscle and cardiacmuscle
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Divisions of the Autonomic Nervous System
SYMPATHETIC PARASYMPATHETIC
Fight or Flight Responses Rest and Digest Responses
Mobilizes body during increased Conserves energy
activity
these systems work in oppositionto each other manyinvoluntarily controlled organs/effectors are
innervated by both sympathetic and parasympatheticnerve fibres(dual innervationbut not allwe will look at
the more significant exceptions to this and what thewisdom is in this arrangement) with dual innervation, end effect at level of organ is the
sum of opposing commands
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NEURAL TISSUE
98% of neural tissue is found in brain and spinal cord;
balance is found peripherally
1. Neuron - main cell type of nervous system
Characteristics of Neurons:
irritablerespond to stimuli
conductivesend impulses along axonviaproductionof action potential and its propagation
amitoticneurons located in CNS dont dividecant
be replaced if destruction/death of cell occurs longevitydesigned to last entire life of organism
(because of the above point)
high metabolic raterequire large oxygen and glucosesupplycells die/cease to function adequately rapidly
if supply is poor or absent
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Basic Neuronal Structure
a)soma(cell body)spherical nucleuscontainsall the same organelles as other cells, but lackscentrioles (no cellular division); soma is focal point
for extension of processes(see below); producesproteins and membranes required formaintenance of neuron
b)processesextend from soma; brain and spinal
cord (CNS) contain cell bodies and their processes;peripheral nervous system (PNS) consists mainlyofprocesses (dependent upon motor division inquestion)
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2 types of processes:
i) axon
each neuron has 1 axonarises from axonhillock, thennarrows to form the diameter of the
process; some neurons lack axons or are very short,while others have significant length (long axonsareknown as nerve fibres)
- at their distal ends, axons almost always branch
into several terminal branches(often thousands);at the ends of these branches aresynaptic knobs(AKA - axon terminalsor boutons)
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- axon is conducting region, with impulses usuallybeing transmitted away from cell body
- axon terminalsare thesecretory regionsof theneuron site of release of neurotransmitters forexcitation orinhibitionof target tissue (effectorcellsex. muscle tissue at neuromuscular junction;
may also allow communication with other neurons)
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ii) dendrite
each neuron has several dendrites(hundreds); they
are the main input regions(receive signals/impulsesfrom other neurons) responsible for conduction of
impulses toward cell body
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Other Neuronal Structures
c) myelin sheathlong or large-diametered nervefibres are covered by segmented sheath made ofprotein-lipid substance(layers of plasmamembrane)
- protects and insulates fibres and allows fasterimpulse transmission
- fibres lacking myelin sheaths (unmyelinated) areslower conductorsare usually thinner in diameter
(dendrites lack myelin)
- gaps left between segments of myelin are calledNodes of Ranvier
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- small axons in the CNS are also unmyelinated- myelinated fibresform white matterin the CNS;unmyelinated fibres andcell bodiesform the greymatterof the CNS
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Classification of Neurons by Function
a) Sensory (Afferent) Neurons
- impulses travel from receptors (dendrites) at level
of organs toward the CNS- processes are generally quite long; distal branchacts as receptorregion
- cell body is usually located outside the CNSin
sensory ganglia(cluster of cell bodies, oftenlocated close to spinal cord)
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c) Interneurons
- communication (links) between sensory andmotor neurons within the CNSintegration/interpretationoccurs here based onimpulse received from sensory neuron, thensynapse occurs between interneuron and motor
neuron
b) Motor(Efferent) Neurons
- impulses travel from CNS to effectors(ex. musclesand glands) in the peripheral regions; cell bodiesare located in CNS
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***Of greater interest for us regarding this basic pathway: monitoring of
the internal (physiological) environment, with subsequent involuntary
responses via smooth and cardiac muscle effectors (autonomic nervous
system).
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2. Neuroglial Cells (other supporting cells of thenervous system)
- characteristics:
a) no irritabilitydo not respond to stimuli
b) no conductivity
c) no release of neurotransmitters
d) mitoticare capable of division
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- sometypes of neuroglial cells of interest for us:
a) astrocyteslocated in CNS- star-shaped and cling to neurons and capillariesof CNS- allow transfer of nutrients, dissolved gases andions between neurons and blood- control blood flow through capillaries- absorb and recycle some neurotransmitters- extensions of astrocytes, in part, contribute tostructure of blood-brain barrier (assist in making
capillaries less permeable in CNS); well look at thismore closely later- provide structural framework for neurons in brain
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b) ependymal cells
- located in CNS
- cuboidal or columnar with processes whichcontact other glial cells
- may have cilia or microvilli; some producecerebrospinal fluid (CSF); line central cavity(ventricle) of brain and spinal cord well look at thismore closely later
- form barrier between CSF and fluid surroundingnerve cells
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NERVES
located in the PNS; contain nerve fibres(axons)and blood vesselswrapped in connective tissue
a) sensory nervessensory receptors of manyneurons, wrapped in connective tissue; cell bodies
are located in ganglion(cluster of cell bodies)outside of CNSb) motor nervesaxons of many neurons,wrapped in connective tissue; cell bodies are notcontained in the nerve, but in the spinal cord
(CNS)c) mixed nerveboth sensory receptors and axonsof many different neurons, wrapped in connectivetissue
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TRACTS
bundles of axons(nerve fibres) located inside theCNS; similar to nerves, but without the connectivetissue wrapping
a) Ascending Tractscarry sensory impulses from
spinal cord to brainb) Descending Tractstransmit motor impulsesfrom the brain to the spinal cord
FACTORS AFFECTING SPEED OF NERVE IMPULSES
1. myelin sheathincreased speed if myelinated2. size of fibreslarge diameter fibres conductimpulses faster
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SYNAPSE
synapse= area where 2 neurons meet (axon ofone neuroncommunicates with a dendrite of asecond)
pre-synaptic neuronis neuron conducting the
impulse toward the synapse; post-synaptic neuroncarries signal away from synapse post-synaptic cellsmay be neurons or effector
cells (ex. muscle cell or glandular cell) area where neuron meets effector(muscle or
gland) is neuroeffector junction(ex. neuromuscularjunction)
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SYNAPSES and IMPULSE CONDUCTION
- chemical synapsesuse release and reception of
neurotransmitters for communication
consist of 2 parts:
i) pre-synaptic axon terminalwhich contains
neurotransmitter substance (insynaptic vesicles)ii) post-synaptic receptorregion on dendriteofpost-synaptic neuron (or at effector cellmembrane)
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What Occurs at the Chemical Synapse?
pre and post-synaptic membranes are separatedby thesynaptic cleftfluid filled space acrosswhich chemical signal must travel
signal starts as electrical signal at pre-synapticmembrane (nerve impulse)impulse stimulatescalcium (Ca2+) channels on the synaptic bulb toopencalciumenters the pre-synapticmembranestimulatesneurotransmitter to bereleased into synaptic cleftneurotransmittercrosses the cleft neurotransmitter binds to
receptor on post-synaptic membrane andchemical signal is convertedback into electricalsignal at post-synaptic membrane post-synapticmembrane depolarizes, initiating an actionpotential (nerve impulse)
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napse h drive winter
2006
16
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TYPES OF SYNAPSES BY STIMULATED ACTIVITY
neurotransmitters can activateor inhibit cellactivities
1. Excitatory Synapses
neurotransmitter-receptor combination causessodium channels to open, allowing diffusion ofmassive amounts of sodium ions inside the cellDEPOLARIZATIONof membrane; cell polaritychanges from being negative to being positiveinside the cell membrane (does this sound familiar?I think you can expect to see some impulseactivation here!)
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2. Inhibitory Synapses
neurotransmitter-receptor combination causespotassium and chloride channelsto open, causingpotassium ions to leave the cell and chloride ions(which are negatively charged) to enter the cellHYPERPOLARIZATIONof membranecell polaritychanges, becoming more negative inside the cellmembrane(therefore, is it going to be more
difficult to cause an impulse if the inside of the cellis more negative? I bet it will be!)
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NERVE IMPULSE EXCITATION
purpose of impulse is to carry message from sense
organ to brain or from brain to effector; impulse isan electrical disturbance traveling down the lengthof a neuron; the movement of sodium andpotassium ions in and out of a neuron creates thedisturbance
1. Neurons at REST are POLARIZED
sodium ions are found on outside of neuron,potassium ions on inside; therefore, inside ofmembrane is negatively charged relative to theoutside because membrane is more permeable topotassium with constant leakage outof themembrane; the gradient for sodium to enter cell isgreater due to its concentrations on both sides ofthe membrane, but membrane is relativelyimpermeable to sodium; normal resting potential fornerve cells is approx. -70 mV
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2. DEPOLARIZATION of Neuron
when stimulus is applied (neurotransmitter), sodiumchannels open, and sodium enters themembraneelectrical potential is reversed; inside of
membrane becomes positive relative to outsidethreshold for potentialto cause impulse is approx.
-55 to -50 mV(potential often over shoots to +30mV, causing an initial spike in electrical activity)
in myelinated axons, the voltage-regulated sodium
channelsare concentrated at the Nodes ofRanvier
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3. Nerve IMPULSE is Carried
relatively negative charge outsideof membranestimulates next point on membrane to depolarizeand so on down the length of membrane
4. REPOLARIZATION of Neuron
reversal of charge lasts fractions of a second;sodium channels close, stopping the flow of
sodium ions and potassium channels open,allowing potassium ions to leave the insideof themembranereturns charge on outside to beingmore positive than inside again
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5. Neuron at Rest or POLARIZED
active transport mechanisms (Na+/K+-ATPasepumps) return membrane potential to restingpotential (remember, 2 potassium ions in, 3 sodium
ions out)
6. REFRACTORY Period
until resting potential is restored by active transport,stimulation with the creation of an impulse cannotoccur
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Neurotransmitters Messenger Molecules
chemical messenger molecules of nervous system
synthesized in cytoplasm of axon terminal; neuronsare limited in terms of types of transmitters theysynthesize by enzyme systems located in a specific
neuron once synthesized, neurotransmitters are stored in
synaptic vesicles(each terminal may containthousands of vesicles; each vesicle may contain upto 100,000 transmitter molecules)
nerve impulse causes vesicles to be moved into thecell membrane with release of transmitters into thesynaptic cleft
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action of transmitters is exerted on specific proteinsexisting on the post-synaptic membrane
RECEPTORSprecisely match size and shape ofspecific transmitter (lock and key theory)
the interaction of the transmitter with the receptorresults in a specific physiological response; theresponse may be excitatory or inhibitory in nature
if excitatory neurotransmitter is released at effectorcell (example: skeletal muscle cell), musclecontraction occurs
if inhibitory neurotransmitter is released at effectorcell (example: smooth muscle cell), muscle
contraction is inhibited receptors are named according to the type of
neurotransmitter with which they bind (ex.cholinergic receptors bind with acetylcholine)
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Basic Receptor Theory Direct vs. Indirect Receptorand Neurotransmitter Mechanisms
A. Direct Mechanismbinding of neurotransmitter tocell membrane receptors, causing opening ofmembrane ion channels (ex. seen with ACh onskeletal muscle cell membrane)
B. Indirect Mechanism- proteins on inner surface of plasma membrane ofeffector cells are activated by binding ofneurotransmitter to transmembrane receptors- the inner surface proteins (G-proteins) are then
activated to:a) open or close membrane ionchannelsor b)produce second messengermolecules which stimulate a series of enzymaticactivities inside effector cells; these series ofactivities then modify activities of other proteins(ex. channel proteins)
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examples of second messengers used via indirect
neurotransmitter and receptor mechanisms include:cyclic AMP, cyclic GMP, Ca2+and diacylglycerol
most amino acid based neurotransmitters, when they
bind with membrane receptors on effector cells, exert
their effects via second messenger systems these types of neurotransmitter/receptor interactions
tend to result in slower, longer-lasting and broader
physiological effects (ex.smooth and cardiac muscle
contraction stimulation or inhibition)
a well known and wide spread example of a secondmessenger system is the cyclic-AMP(c-AMP)
mechanism
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Cyclic-AMP Second Messenger Mechanism:
First Messenger Neurotransmitterbinds with
Target Cell Membrane Receptor
Receptor Configuration is modifiedand binds alternatively with
G Protein(plasma membrane protein) which moves freely through plasma
membrane until it binds with
Adenyl Cyclase(effector enzyme) which catalyzes
ATP (adenosine triphosphate) Cyclic-AMP(cyclic-adenosine monophosphate= ringshaped molecule)
C- AMP = second messenger
Activates further enzymatic cascades (by activating protein kinases), causingspecific cellular response, depending upon tissue target and enzymes
present at the effector site
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- stimulated enzymatic cascades from abovemechanism may result in:
a) altering cell membrane permeability(ex. opens orcloses cell membrane channels) to promote orprevent entry of substances into effector cells (ex.increased or decreased Ca2+entry into vascular orbronchiolar smooth and cardiac muscle cells)b) stimulation of smooth and cardiac muscle cellcontraction- ex. as more calcium ion enters vascularsmooth, bronchiolar smooth or cardiac muscle cells,muscle contraction occurs more readily or to a greater
degreec) inhibition of smooth and cardiac muscle cellcontraction- ex. as less calcium ion enters vascularsmooth, bronchiolar smooth or cardiac muscle cells,muscle contraction is inhibited
http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors__g_proteins__and_ca2__channels.htmlhttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors__g_proteins__and_ca2__channels.htmlhttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors__g_proteins__and_ca2__channels.html -
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neurotransmitters must be quickly removed afterexerting their effects on the post-synaptic
membrane or effector cell membrane in one of 3ways:
a) broken downby specific enzymes(ex.rememberacetylcholine is broken down by
acetylcholinesteraseat neuromuscular junction)
b) taken back up(reabsorbed) into the pre-synaptic neuron or axon terminal
c) diffuses/migrates away from synaptic cleft-concentration of neurotransmitter becomes toolow to exert further effects on post-synapticreceptor sites
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Major Classifications of Neurotransmitters and Their
Receptors
1. Acetylcholine(ACh) and Cholinergic Receptors
a) ACh released by all neurons that stimulateskeletal musclesvoluntary control (somatic)
- released at neuromuscular junction
- specific type of ACh receptor on skeletal muscle
cell membrane is called NICOTINICreceptor- neurotransmitter/receptor combination results inexcitatory response skeletal muscle contraction
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b) ACh released by motor neurons of theAUTONOMIC NERVOUS SYSTEM (ANS)- released specifically by all preganglionic axons(ganglion = cluster of cell bodies; so, released atregion where 2 or more neurons meet pre-ganglionic neuron and post-ganglionic neuron; orwhere pre-ganglionic neuron meets a gland)- receptors for ACh are located at all ANS ganglia
(sympathetic motor pathways andparasympathetic pathways) and on adrenalmedulla (gland on kidney)- these receptors are also specifically NICOTINICreceptors
- this neurotransmitter/receptor combination isalways excitatory results is impulse conductionto post-ganglionic neuron or release of hormonefrom a gland (adrenal gland)
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c) ACh released by all post-ganglionicparasympathetic
neurons
- receptors are located on all parasympathetic targetcells (involuntarily controlled tissues); ex. cardiac
muscle, pupillary muscle, bronchial smooth muscle,
gastrointestinal tract
- this specific type of receptor is called a MUSCARINIC
RECEPTOR
- may be inhibitory (inhibits smooth/cardiac muscle
contraction) or excitatory (stimulates smooth/cardiac
muscle contraction)
- whether inhibition or excitation occurs is dependentupon enzyme systems located in specific cell type (tend
to be indirect receptor mechanisms)
- ex. release of ACh at bronchial smooth muscle causes
excitation (bronchial smooth muscle contraction)
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Acetylcholine Site of Release Target Organ Effect
Cholinergic Receptor
Type
Nicotinic Neuromuscular junction Skeletal muscle Excitatory(voluntary)
By Pre-Ganglionic
Neuron at All ANS
ganglia (PNS)
Ganglia Excitatory(involuntary)
By Pre-GanglionicNeuron at Adrenal
Medulla
Hormone producing cells Excitatory (epinephrineand NErelease)
Muscarinic By Post-Ganglionic
Parasympathetic Motor
Neuron at target organ
Heart Inhibitory(decreased rate
of contraction)
By Post-GanglionicParasympathetic Motor
Neuron at target organ
Bronchioles Excitatory(bronchialsmooth muscle
contraction); increased
airways secretion
production
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2. Biogenic Amines and Adrenergic Receptors
a) Catecholamines and Adrenergic Receptors
in the PNS, norepinephrineis the mainneurotransmitter released by post-ganglionicneurons (so, released at involuntarily controlledtarget tissues) in thesympatheticnervous system- epinephrine(really a hormone) is released by theadrenal medulla (gland on kidneysite of largeganglion) in response tosympathetic nervoussystem stimulation
norepinephrine is also a hormone secreted here(in smaller amounts than epinephrine - very similarin chemical structure to epinephrine)
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- hormones exert their effects via circulation(releasedinto blood) at distal target organs
- both epinephrine or norepinephrine may be excitatory
or inhibitory, depending upon the target organ and the
receptor sub-types that they bind with at the target
organ; dopamine is also released by some sympatheticpost-ganglionic neurons (also very similar structurally to
NEmissing the hydroxyl group)
- the receptors on target organs for these transmitters
and/or hormones are known as adrenergic receptors
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ADRENERGIC RECEPTOR SUB-TYPES:
a) alpha adrenergic receptors ()- alpha-1(1)adrenergic receptorsfound onsmooth muscle cell membranes - binding withnorepinephrine or epinephrine is excitatory,causing smooth muscle contraction inperipheralarterioles (excitatory); RESULT= vasoconstriction- alpha-2(2)adrenergic receptorsfound onmembranes of sympathetic motor axon terminalsstimulation of these receptors inhibitsnorepinephrine release, causing less smoothmuscle contraction in peripheral arterioles(inhibitory) ; RESULT= relative vasodilation
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b) beta adrenergic receptors ()-beta-1 (
1
) receptorscardiac musclebinding withnorepinephrine or epinephrine is excitatory, increasingheart rate (chronotropy) and strength of contraction(inotropy)
- beta-2(2)receptorsbronchial smooth musclebinding with epinephrine (released by adrenal medulla)
causes bronchodilation (inhibitory action on bronchialsmooth muscleless contraction); binding withepinephrine at arterioles serving skeletal muscle andheart (coronary arterioles) causes less smooth musclecontraction and relative dilationof these blood vessels;(inhibitory)
- beta-3(3) receptors on tissue cells like fat tissueand liver; epinephrine stimulates increased glucoserelease by the liver and fatty acid mobilization fromadipose tissue cell into blood (metabolic fuels are mademore readily available)
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Receptor Site Sympathetic (adrenergic) Parasympathetic (muscar in ic)
Cardiovascular System
heart rate(chron otropic ef fect
rate of contraction)
1: increases
Via NE and E
Decreases
Via ACh
cardiac muscle contractility
(ino t rop icstrength of
contractility)
1: increases
Via NE and E
Decreases
Via ACh
vascular smooth muscle 1= contracts(decreases
peripheral blood supply skin,
GI tract, kidney, non-vital organs
via NE and E)
2= relaxes (increases
coronary and skeletal muscleblood supply via E)
no effect (no parasympathetic
innervation to blood vessels)
NE = norepinephrine; E = epinephrine; ACh = acetylcholine
Receptor Site Sympathetic (adrenergic ) Parasympathetic (muscar in ic)
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Receptor Site Sympathetic (adrenergic) Parasympathetic (muscar in ic)
Respiratory System
smooth muscle in bronchioles 2: relaxes (bronchodilation)
Via E
(no direct sympathetic
innervation to bronchial
smooth muscle)
Contracts(bronchoconstriction)
Via ACh
Other
pupil of eye 1: relaxes(dilates pupils)
Via NE and E
Contracts (constricts pupils)
Via ACh
Secretions (saliva) : decreased secretions (via
NE and E)
Stimulates watery secretions
Via ACh
adrenal medulla Nicotinic* - stimulatesincreased secretion of
epinephrine and
norepinephrinesee all
above effects
NE = norepinephrine; E = epinephrine; ACh = acetylcholine
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Target Site Sympathetic(adrenergic) Parasympathetic(musc arin ic)
Liver 3: increased release of
stored glucose intocirculation
Via E
No effect (no parasympathetic
innervation)
Fat (Adipose) Tissue 3: increased lipolysis
(increased release of fatty
acids into circulation for
metabolism by cells more
ATP production)Via E
No effect (no parasympathetic
innervation)
Cellular Metabolism increased metabolic rate:
Via E (see above effects ie:
blood flow to vital regions and
fuel release into circulation,
etc.)
NE = norepinephrine; E = epinephrine; ACh = acetylcholine
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CNS PNS EFFECTORS
Somatic Cell Body Skeletal Muscle (Ach - Nicotinic)
Sympathetic Cell Body Ganglion Smooth/Cardiac Muscle and Glands(ACh - Nicotinic) (Norepinephrine - Adrenergic)
Cell Body Adrenal Medulla Smooth/Cardiac Muscle and Glands(ACh - Nicotinic) (Epi/NorepiAdrenergic)
Para- Cell Body Ganglion Smooth/Cardiac Muscle and GlandsSympathetic (ACh/Nicotinic) (AChMuscarinic)
Pre-ganglionic Axon
Post-ganglionic Axon
Release of Hormones Directly into Circulation (Epinephrine and Norepinephrine)
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B/Indolamines
a) serotonin(feel good neurotransmitterreleased
in response to pain)b)histamineis released in the CNS (hypothalamus,but its affects are poorly understood) and by mastcells during inflammatory process (really amediator in this case, not a neurotransmitter) andacts as a powerful vasodilator(decreases smooth
muscle contractioninhibitory in the case of bloodvessels)- basophils and mast cells(found in tissuescontain mediators for inflammationa lot found inlung tissue) can release histamine during antigen-antibody (allergic) reactions and in response to
drugs and toxic products; histamine release causesbronchiolar smooth muscle contraction- H1and H2receptors for histamine are foundwidely throughout the body at target effectororgans
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Effects of Histamine
Receptor H1 H2
Heart Slowing of conduction - positive inotropic effect
(increased strength of
contractility)
- positive chronotropic effect(increased rate of contraction)
Blood Vessels (smooth
muscle)
Dilation Dilation
Bronchial (smooth muscle) Contraction
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3. Amino Acid Neurotransmitters
found only in CNS
GABA (gamma-aminobutyric acid)
- inhibitoryneurotransmitter that is very widelydistributed in the neurons of the brain (close to 40%of the synapses in the human brain work with GABAand therefore have GABA receptors)
- GABA receptors are channel receptors
- when GABA binds to them, they change shapeslightly to allow ions to pass through their centralchannel
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- allows mainly negatively charged chloride ions toenter the neuron, causing hyperpolarization of the
membrane, thus reducing its excitability- sedative drugs and agents used for the inductionof general anesthesia (hypnotics) enhance thenatural effect of GABA; in other words, they helpGABA to reduce neural activity even further
- classes of medications which enhance GABAbinding to receptors or mimic the effects of GABAinclude benzodiazepines (examples of commonagents include: midazolamAKA Versed and
lorazepamAKA Ativan) and hypnotic agents(examples of common agents include: propofol,ketamine, etomidate and barbituratesthiopentalis a common barbiturate)
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4. Peptides
A. endorphins and enkephalins(inhibitory)
- found in CNS (brain and spinal cord)- bind with opiate receptors: (mu), (delta), (kappa) and (sigma) and hyperpolarize neuronalcell membranes to inhibit pain reception- endorphins and enkephalins are known as naturalopiates (endogenous controllers of pain)- narcotic analgesics bind to opiate receptors inthe brain and spinal cord to mimicendorphin/enkephalin activity (specific drugs:codeine, morphine, Demerol, Dilaudid, fentanyl,oxycodone)
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B. Substance P
- found in PNS
- allows pain transmission (excitatory)
***See Tables in Marieb, Chapter 11 -Neurotransmitters