3 4 Autonomic Nervous System and Muscle Physiology (2).ppt

Autonomic

1. Edris A 1
•Autonomic Nervous System (ANS)
–Subdivision of the peripheral nervous system
–It innervate involuntary organs, smooth muscle,
glands, blood vessels
–Regulates body activities not under conscious control
–Can effectively control may activities at a time.
•Help to maintain homeostasis

2. Edris A 2
•ANS controls most visceral body function
–Thus ANS helps to control:-
arterial pressure blood chemistry
respiration immune response
circulation GIT motility,
GIT secretion,
Urinary bladder emptying,
Defecation, sweating, body temperature & others.

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•Autonomic motor use 2 neurons in efferent pathway
(between CNS & target organ).
–Preganglionic neurons and
–postganglionic neurons
•Ganglia is group of cell bodies out side CNS-Contains cell body of
postganglionic neurons & axon terminal of preganglionic neurons.
•It innervates non-skeletal(non-somatic) muscles
–Cardiac muscle (the heart)
–Smooth muscle (walls of viscera and blood vessels)
–Internal organs -Skin
•ANS bring rapid & intense change in visceral functions.
–With in 3-5 seconds it doubles the heart rate
–With in 10-15 sec it doubles the Arterial BP

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•.

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Autonomic & Somatic Motor Systems

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•ANS consists:
–Enteric nervous system
–sympathetic nervous system,
–parasympathetic nervous system and

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Enteric nervous system
–A unique neural system embedded in an unlikely place
(in the gut wall)
•In lining of esophagus, stomach, intestine, pancreas,
gall bladder
–Exist as nerve plexuses (net work)
•an outer plexus-myenteric plexus or Auerbach’s plexus,
–Supply muscularies layer –control movement of food in GIT
•an inner plexus-submucosal plexus or Meissner’s plexus
–Supply submucosa-control GIT secretion, reabsorption
–Has connection with sympathetic & parasympathetic
•Parasympathetic GIT activity but sympathetic GIT activity

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Enteric nervous system
–Contain as many number of neurons as in spinal cord
–Considered as little brain because it can operate with
great deal of independence
–Enteric sensory neurons monitor
•Tension, stretch of GIT walls, chemical status, and
hormone level in the blood
–This information is used to govern motility, mucus
secretion, hydro-electrolyte secretion, blood flow of GIT.

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Sympathetic Nervous System
•The sympathetic nerve fibers
–Originate from in spinal cord gray mater lateral horn
b/n T-1 & L-2to corresponding spinal nerves.
–First pass into the sympathetic chain ganglia
–Then to the target tissues and organs they innervate.
•Thus sympathetic neuron originate from thoracolumbar
region of spinal cord.
•Sympathetic has:
–(1) two paravertebral chains of sympathetic ganglia
–(2) two prevertebral ganglia (celiac& hypogastric) and
–(3) nerves extending from ganglia to different organs.

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•.
ANS -solid lines (preganglionic fibers)
-dashed lines (postganglionic fibers).

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•Sympathetic has short preganglionic & long postganglionic.
–Preganglionic fibers from gray lateral horn
–Contains more gangliathan the parasympathetic division
–Supplies visceral organs & other effectors

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•Sympathetic use neurotransmitter acetylcholine (Ach)at ganglia and
norepinephrine (NE)at the target organ.
–Exception:-Use Ach at sweat gland, piloerector muscle, skeletalM. blood vessels
•Ach or Ach-like substances applied to the ganglia, will excite
postganglionic neurons.
•Sympathetic axons are highly branchedto influences many organs

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•Effects of Sympathetic
–"Fight or Flight" Branch of the ANS
•Used in emergency situations
–where body needs a sudden burst of energy,
–Increase energy production and expenditure
–By increasing energy producing reactions
•It is essential for any stressful situation

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•Thus sympathetic system:-
–cardiac output by raising heart rate & contractility via β-1
–pulmonary ventilation by breathing rate & bronchodilation
(beta-2)
–blood glucose level by glycogenolysis via beta-2
–Free fatty acid level by lipolysis from adipose tissue via β-3
–By constricting arterioles shift (routes) blood flow from GIT, skin,
inactive muscle to active muscles.
–Pupil dilation (by contracting radial/meridian/ smooth M. in iris)
•Slows down digestion, GIT secretion, kidney filtration, defication,
urination, sexual stimualtion &other functions not needed during
emergencies.
•Sweating (cold sweat due to contraction in skin), dry mouth by
saliva secretion, & piloerection.

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•During fright, fear, rage or severe pain Sympathetic
responds by Mass Discharge
–large portions of sympathetic activated at a time
–Known as Alarm” or “Stress” Response
–Results widespread reaction throughout body
•Thus :
•1. arterial pressure
•2. blood flow to active muscles –
•3. flow to GIT, some organs, skin, inactive muscle
•4. rates of cellular metabolism throughout the body
•5. glycogenolysis in the liver and in muscle
•6. blood glucose level 7. muscle strength
•8. mental activity 9. rate of blood coagulation

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•Adrenal Medullae
•Adrenal medullae is endocrine gland at the core of adrenal gland on
top of each kidney.
•Preganglionic sympathetic nerve directly supply the two adrenal
medullae with out synapsing in ganglia.
•It contain modified neuronal cells that secrete epinephrine (80%) &
norepinephrine (20%) into the blood stream.
•These secretory cells are embryologically derived from nervoustissue
& act as postganglionic neurons.
•It bring effect of sympathetic nervous system.

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•The adrenal medulla isconsidered assympathetic
ganglion where postganglionic neurons have lost
their axons and become secretory cells.
•The cells secrete when stimulated bysympathetic
preganglionic nerve fibers via splanchnic nerves.
•Adrenal medullary hormones are essential during
emergencieslike sympathetic nerve .

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•Special sympathetic supply to adrenal medullae

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•Parasympathetic Nervous System
•Originate from cranial and sacral region (Craniosacral).
•It has long preganglionic nerve that synapse near or in the
target organ & very short postganglionic nerve.
–except few cranial parasympathetic nerves
•It use neurotransmitter acetylcholine (Ach) both at ganglia
& target organ.
•Out of 12 pairs of cranial nerves only 4 are parasympathetic
(Cranial nerves III, VII, IX, & X)
•Parasympathetic fibers from sacral emerge between S2 –S3
& rarely from S1& S4

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•Effects of parasympathetic
•It is referred as “Rest & Digest”.
•Used when the environment is stable & controlled.
•To conserve energy by reducing energy expending reaction.
•Also help to release energy from food by enhancing GIT
activity.
Cranial outflow
•CN-III(oculomotor) -pupils constrict
•CN-VII (facial nerve) -tears, nasal mucus, saliva
•IX (glossopharengeal) -parotid salivary gland
•X (Vagus) -visceral organs of thorax & abdomen.

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Effects of Parasympathetic
Vagus nerve (X)
Heart: inhibits contractility, rhythmicity (SA-node),
conductivity in atria
Bronchi and bronchioles: bronchoconstriction and
mucous secretion from bronchial glands
•Increase pulmonary vascular compliance through NO
mechanism. This is important at high altitude
Hepatobilary system-increase secretion and release of
bile

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•PSNS on Gastrointestinal system:
•Increase motor activity of GIT wall & secretion of glands,
while inhibitory to the sphincters
•Distal colon, rectum and anal canal: defecation
•Pancreas: increase acinar and islets secretions
Blood vessels: vasodilatation of arterioles except where there is
poor innervations as in renal and visceral arterioles plus the whole
veins
Urinary bladder:
•Motor to detrusor and inhibitory to the sphincters (Micturition)
•Ureters: increases motility and tone
•.

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Genital organs:
•Erection a hydraulic process triggered and sustained
by PSNS.
•PSNS activity gets it going and keeps it going.
•But orchestrated shift to SNS is necessary to stop it.
•The attendant of anxiety and worry, SNS, inhibit
erection and promote ejaculation
•Impotence and premature ejaculation is the complaint
of over stressed boy.

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•Dual Innervations with SNS & PSNS
•Homeostatic ability (internal balance) depend on this dual
innervations (balance b/n SNS & PSNS)
•Antagonistic dual innervations
–Eg. In heart –SNS heart rate, contractility
–PSNS heart rate, contractility, conduction
•Complementary Dual Innervations
–Eg. Digestion. PSNS enzyme, saliva, mucus secretion
SNS secretion rate &concentrate secretion
•Cooperative dual innervations
–Eg. Coitus where PSNS bring arousal (erection)
SNS bring orgasm (ejaculation),

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ANS neurotransmitters
•The neurotransmitter in ANS are:-
–Acetylcholine (Ach) from cholinergic neuron or
–norepinephrine (NE) from adrenergic neruon
•Ach is parasympathetic transmitter.
•NE is sympathetic transmitter.

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•Molecular structures of acetylcholine & norepinephrine.

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•Neuro-Transmitters and Receptors.

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•Types of Receptors in ANS
•Cholinergic Receptors:respond to transmitter molecule
Acetycholine (ACh).
•Based on their sensitivities to extrinsic compounds
cholinergic receptors classified as Nicotinicand Muscarinic.
•NicotinicReceptors.
–Stimulated by ACh and nicotine,
–Not stimulated by muscarine.
–Found at all ganglionic synapses.
–Also found at neuromuscular junctions of skeletal muscle
–Blocked by hexamethonium.

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•MuscarinicReceptors.
–Stimulated by ACh and muscarine, not stimulated by
nicotine.
–Found at target organs where ACh is released by post-
ganglionic neurons (all parasympathetic & some
sympathetic).
–Stimulated selectively by Muscarine, Bethanechol.
–Blocked by Atropine.

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•Muscarinic receptor stimulation causes:
–Increased sweating.
–Tearing and salivation.
–Urination and defecation.
–Engorgement of genitalia.
–Decreased heart rate.
–Decreased blood pressure due to decreased cardiac output.
–Bronchoconstriction and increased bronchosecretion.
–Contraction of pupils & contraction of ciliary body for near vision.
–Increased motility and secretions of the GI system.

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•Adrenergic Receptorsare those stimulated by Epinephrine
Norepinephrineand Isoproterenol(extrinsic drug) .
•Adrenergic receptors classified Alpha and Beta receptors.
•
Alpha Receptors
•Epinephrine (EPI) and norepinephrine stimulate about equally well,
•Two subclasses of alpha receptor alpha-1 and alpha-2:
•Alpha1 Predominant form of alpha receptor in the body.
•Found primarily in the smooth muscles of arterioles, eye, gut, skin,
veins, etc., as well as in some other cell types (like salivary glands).
•Usually causes contraction of smooth muscle cells.
•Alpha2 Found at pre-synaptic terminals of adrenergic nerves.
Functions as an autoreceptor. If stimulated, it decreases the
subsequent release of transmitter.

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•Beta Receptors
•Isoproterenol stimulates best, epinephrine is also effective,
and norepinephrine is often weaker.
•Blocked by propranalol.
•Several subclasses of beta receptor ( β-1, β-2. β-3):
•Beta1
•Found in heart muscle, and in the kidney.
•Causes increased heart rate and contractility.
•Promotes release of renin from the kidney.
•Epinephrine (EPI) and Norepinephrine (NE) are about
equally effective in their ability to stimulate beta1 receptors.

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•Beta-2 Found in smooth muscle that relaxes upon stimulation, and in
metabolic tissues.
•Decrease in GIT motility.
•Bronchodilation.
•Vasodilation in skeletal and cardiac muscle.
•Glycogenolysis in the liver.
•EPI is much more effective than NE. EPI can also stimulate beta2
receptors at lower concentrations than required to stimulate alpha
receptors.
•Beta-3
•Found in adipose tissue (fat cells).
•Stimulates lipolysis, increasing fatty acids in the blood.
•EPI and NE are about equally effective in their ability to stimulate
beta3 receptors.

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Physiology of Muscle
•Muscleis contractiletissueof the body.
•It is derived from mesodermal layerof embryonic germ cells.
•Muscle contraction develop tension (force) used for various activities
and contraction consume ATP energy
•Thus muscles convert chemical energy of ATPinto mechanical work.
•This tissue combined with nerves, blood vessels, and connective
tissues.
•Muscle comprises the largest of body. Skeletal musclealone makes
up about 40% of body weight in men and 32% in women, while
smooth and cardiac musclemaking up 10% of the total weight.

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•Characteristics of Muscle Tissue
•1. Excitability
–The ability to receive and respond to a stimulus
•In skeletal muscle, the stimulus is a neurotransmitter (chemical signal)
•In smooth muscle, the stimulus could be a neurotransmitter, a hormone,
stretch, pH, Pco2, or Po2. (the symbol means “a change in”)
•In cardiac muscle, the stimulus could be a neurotransmitter, a hormone, or
stretch.
–The response is the generation of an electrical impulse that travels
along the plasma membrane of the muscle cell.
•2. Contractility, The ability to shorten forcibly when
adequately stimulated..
•3. Extensibility, The ability to be stretched
•4. Elasticity,The ability to recoil and resume original length
after being stretched.
•.

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•Functions of Muscle
•Production of Movement
–Movement of body parts and of the environment
•blood through the heart and the circulatory vessels.
•lymph through the lymphatic vessels
•food ( food waste) through GI tract &newborn in birth canal
•urine through urinary tract, & semen through reproductive tract
–Movement of bile out of the gallbladder and into the digestive tract
•Maintenance of posture
–Muscle contraction is constantly allowing us to remain upright.
–The muscles of your neck are keeping your head up right now.
–As you stand, your leg muscles keep you on two feet.
•Thermogenesis: Generation of heat. Occurs via shivering –an
involuntary contraction of skeletal muscle.
•Stabilization of joints: keep the tendons that cross joint maintaining
the integrity of the joint.

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•II. Types of Muscle Tissue
•categorized by location, histology, and modes of control.
•3 types of muscle: skeletal, cardiac and smooth muscle
•A. Skeletal muscle:
•attached to bones & moves skeleton
•striated muscle-stripe appearnace (alternating dark and
light bands) due to its regularly arranged thin and
thick filaments in sacromere
•Voluntary muscle -innervated by the somatic nervous
system and so subject to voluntary control
•Large multi nucleated & large sarcoplasmic reticulum
•Has T-tubule (transverse tubule where sarcolerma go deep
in to muscle and come up)
–T –tubule let A.P. go deep in to muscle

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Structure of skeletal muscle.
•Each muscle cells consist long protein molecules called myofilaments.
•There are two types of myofilaments:
–Thick myofilaments (myosin) and
–Thin myofilaments(actin).

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•The myofilaments(actin & myosin) are arranged in unit called
sarcomeres.
•Sarcomers are subunits of muscle cells lined up end-to-end.
–It is space between two Z-line or
–It is structural and functional unit of muscle.
•In skeletal muscle myofilaments ( actin & myosin) are arranged in a
very regular pattern in sarcomeres units.
–thick myofilaments (myosin) are always surrounded by 6 thin
myofilaments (actin)..

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•In each sarcomere, thin myofilaments (actin) extend
in from each end of sarcomere (Z-line) to center of
sarcomere.
•Thick myofilaments (myosin) are found in the
middle of the sarcomere and do not extend to the
ends of sarcomere.
•Because of this myofibril arrangement, skeletal
muscle has alternating light and dark areas.
–This gives stripe appearance to skeletal muscle (striated
muscle)..

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Muscle Contraction: Occurs by sliding of thin filaments
over the thick filaments.
Myosin head holds actin & pull to the M-line (center of sarcomere

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•Interaction between actin & myosin.

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Note the relationship between the thin and thick filaments

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•Neuro-Muscular Junction

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Neuro-Muscular Junction

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•Motor unit is a somatic motor neuron and all the skeletal
muscle fibers it innervates.
•When this neuron is stimulated, all the muscle fibers it
controls will be stimulated & contract as a unit.
•The number of muscle fibers per motor unitcan be 4 or
more.
•Small motor unit, is for fine movement requiring accuracy
•Few muscle per motor neuron
–Eg. Extraocular muscles typically have small motor units
•Large motor units in legs, trunk for gross movement.
•Many muscle per motor neuron
•.

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•Rigor Mortis
•Upon death, muscle cells are unable to prevent
calcium entry.
•This allows myosin to bind to actin.
•Since there is no ATP made postmortem, the myosin
cannot unbind and the body remains in a state of
muscular rigidity for almost the couple days.
•This phenomena is known as rigor Mortis..

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Types of skeletal muscle fibers
•Slow Fibers-red fibers /Type I fibers/.
•(1) Smaller diameter fibers.
•(2) Also innervated by smaller nerve fibers.
•(3) More extensive blood vessel and capillaries to supply O2.
•(4) Many mitochondria, for oxidative metabolism.
•(5) Many myoglobin, an ironcontaining protein similar to hemoglobin
–to store O2.
•Fatigue resistant-work for long hours
•Generate small force but for long hours
–For maintaining body posture, walking.

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•Fast Fibers-white fibers/Type II fibers/.
•(1) Large fibers for great strength of contraction.
•(2) Extensive SR for rapid Ca++ release
•(3) Many glycolytic enzymes for rapid release of energy by
anaerobic
•(4) Less extensive blood supply
•(5) Fewer mitochondria
•(6) Not fatigue resistant
•(7) Can generate large force in short time
–For weight lifting
–For short distance race

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Muscle disorders
•1. Myasthenia gravis is a disease characterized by
progressive fatigue and generalized weakness of the skeletal
muscles, especially those of the face, neck, arms, and legs,
•It is caused by impaired transmission of nerve impulses
following an autoimmune attack on acetylcholine receptors.
•Results in progressive weakening of the skeletal muscles.
•Treated with anticholinesterases such as neostigmine or
physostigmine.
•These decrease the activity of acteylcholinesterase.

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•2. Muscle Atrophyis a general physiological
process of reabsorption and breakdown of tissues.
•It is the partial or complete wastingaway of a part of
the body.
•Causes of atrophy include
–poor nourishment,
–poor circulation,
–loss of hormonalsupport,
–loss of nervesupply to the target organ,
–disuse or lack of exerciseor
–disease intrinsic to the tissue itself

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•Smooth Muscle:
•Involuntary muscle since innervated by the Autonomic Nervous
System (visceral efferent fibers)
•Found primarily in the walls of hollow organs & tubes (uterus, GIT,
artery, vein, bladder, ureter….etc)
•Spindle shaped cells typically arranged in sheets
•Have no T-tubules & has very little sarcoplasmic reticulum.
•It is non-striated (thick and thin filaments in smooth muscle are not
regularly arranged).
•Smaller, uninucleate, indistinct cells.

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•Smooth muscle contraction
•1. Signal to initiate contraction is increase in intracellular
Ca++ concentration which enters from extracellular
fliud and released from Sarcoplasmic reticulaum.
•2. Calcium binds to calmodulin
•3. Calcium calmodulin complex activates myosin light chain
kinase(MLC kinase)
•4. MLC kinase activates myosin ATPase by
phosphorylating light proteins in myysin head
•5. When the myosin ATPase is active actin bonding and
cross bridge formation can occur
•6. Contraction of smooth muscle takes place.

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•Smooth muscle relaxtation
•Ca+2 is removed by actions of the Na+/Ca+2 exchager and
Ca+2 ATPase.
•Myosin light chain phosphatese removes the phosphate
group from myosin.
•This inhibits ATPase activity and contraction.
•Dephosphorylated myosin does not relax immediately, thus
remain bound to actin for extended periods of time called
“latch state”.
•Latch state maintain tension in the smooth muscle with out
using extra ATP.
•.

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•Excitation-contraction coupling in smooth muscle

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•C. Cardiac muscle:
•Muscle of the heart (found in heart wall).
•Involuntary as controlled by Autonomic NS.
•Its cells are striated, short, branched & uninucleate.
•Tightly connected by intercalated disks by
desmosome and gap junction.
•The gap junction provide electrical connection.

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•Cardiac Muscle
•It shows features of both skeletal & smooth muscle.
•Like skeletal muscle;
•1. It is striated having thick & thin filaments highly
organized into regular banding pattern.
•2. Thin filaments contain actin, troponin and tropomysin,
which constitute the site of Ca++ action in turning on cross-
bridge activity
•3. Contracts according to the sliding-filament mechanism
and has a clear-cut length-tension relationship.

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•4. Cardiac muscle cells have an abundance of
mitochondria and myoglobin (like the oxidative
skeletal-muscle fibers)
•5. Also possess T tubules and moderately well-
developed Sarcoplsamic reticulumR
•As in smooth muscle;
•Ca++ enters cardiac muscle cytosol from both SR & ECF
during cardiac excitation
•Cardiac muscle Involuntary as innervated by autonomic NS

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•Excitation-contraction coupling in cardiac muscle