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Physiology (Guyton)

Physiology - Guyton Text

QuestionAnswer
synapse junction point from one neuron to the next; signal passes in forward direct; almost all synapses are CHEMICAL in CNS
sensory information 99% is discarded as irrelevant and unimportant
memory storage in cerebral cortex (largest memory storehouse)
spinal cord level of CNS controls walking mvmts & reflexes
lower levels of CNS controls most of subconscious activities of body
neurotransmitters chemical substance secreted by neurons; NOREPINEPHRINE -> excitatory/inhibitory; ACETYLCHOLINE -> excitatory but can inhibit some parasympath. fibres; DOPAMINE & SERATONIN -> inhibitory
chemical synapses ideal for nerve transmission due to unidirectional signal
spatial summation summing postsynaptic potentials by activating multiple terminals on widely spaced areas of membrane; increased signal strength trasmitted by using progressively GREATER NUMBERS of fibres
temporal summation successive discharge from SINGLE presynaptic terminal can summate if they occur rapidly enough; increased signal strength transmitted by increasing FREQUENCY of nerve impulses in each fibre
mechanical sensory receptors detects compression or stretching
thermal sensory receptors detects temperature changes; located under skin in discrete & separate spots
nociceptor sensory receptors detects tissue damage
electro sensory receptors detects light
all receptors are non-responsive to other types of stimuli but a special characteristic is that they adapt to a constant stimulus after a period of time
reciprocal inhibition circuit neurol circuit which controls all antagonistic pairs of muscles, involves output excitatory signal in one direction & at same time w/ inhibitory signal going elsewhere
after discharge signal entering neuronal pool causing prolonged output, lasting after incoming signal is over
somatic senses collect sensory info. from body (ie. mechano, thermo, pain)
special senses vision, hearing, smell, taste & equilibrium
mechano senses type of somatic sense; stimulated by mechanical displacement of tissues
thermo sense type of somatic sense stimulated by heat & cold sensations
pain type of somatic sense stimulated by any factor that damages tissues; cenrtain tactile receptors can depress transmission of pain signals
positional sense detects static position & rate of mvmt
proprioception sense that have to do w/ physical state of body (ie. position, tendon, muscle, equilibrium)
(blank) touch, pressure & vibration are detected by same types of receptors
free nerve endings tactile receptor located in skin & other tissues that detect touch & pressure; pain receptors
Meissner's Corpuscles nerve endings in non-hairy parts of skin (LIPS & FINGERTIPS) that adapt quickly & are sensitive to mvmt of objects against skin
Merkle's Disc expanded tip receptors grouped into units [Iggo Dome] located in hairy & non-hairy parts of skin, slow to adapt, detects steady state signals about continual touch against skin
hair end organ receptor that incl. hair & nerve fibre entwined at bad that adapts readily & detects mvmt of & initial contact of objects on surface of skin
Ruffini's End Organ nerve fibres found in deep layers of skin & jt capsulles that adapt slowly & signal continuous states of deformation of skin/deeper tissues & degree of jt rotation
Pacinian Corpuscle nerve fibres located immediately underneath skin of deep tissue, adapts quickly, are stimulated by rapid mvmt of tissues & are important for detecting tissue vibration
vibration involves detection of ALL different tactile receptors
tickle & itch detected by very sensitive rapidly adapting mechanoreceptive nerve endings found almost exclusively in superficial layers of skin
dorsal column-medial lemniscal (DC-ML) pathway sensory pthwy transmits info w/ temporal & spatial fidelity, mainly transmits discrete types of mechanoreceptive sensations
Anterolater pathway sensory pthwy transmits broad spectrum of snesory modalities (pain, temp., crude tactile, tickle/itch) slower & w/o spatial fidelity
sensory input posterior areas of cerebral cortecx
motor control anterior areas of cerebral cortex
lips represent by largeest areas in somatic cortex
muscle spindle detection of mid-range jt angulation; proprioceptive sensory receptor located in muscle belly regarding length & rate of change of length
pacinian-ruffini detection of EXTREME jt angulation
pacini & muscle spindle detects rate of mvmt
dermotome spinal nerve that carries info. from segmental field of skin
fast pain sharp, prickling, acute, electric; not felt in deep tissues; elicited by thermal or mechanical stimuli
slow pain slow, burning, aching, throbbing, nauseous, chronic & can lead to prolonged unbearable suffering; is associated w/ tissue destruction; can occur in skin & deep tissues; elicited by mechanical, thermal & chemical stimuli
pain receptors adapt very little & sometimes not at all
hyperalgesia increased sensitvity of pain receptors (keeps person apprised of tissue damage)
intensity of pain correlated w/ rate of tissue damage
muscle spasm can cause pain, possibly due to direct stimulation of pain receptors or indirect effects (ie. ischemia)
fast-sharp pain apprises person rapidly of damaging influence for reaction of immediate removal of stimulus
slow-chronic pain gets greater over time, person continues to relieve cause of pain
analgesia capability of brain to suppress input of pain signals; morphine suppress pain signals entering from peripheral nrv
referred pain felt in body part considerably remote from tissue causing pain; occurs because some signals from viscera conducted thru same neurons that conduct pain signals from skin
headache pain referred to head from deep head structures; can be caused by emotional tension which causes spasm of head/neck muscles
migraine special type of headache result from abnormal vascular phenomena
anterior motor neurons (specifically alpha motor neurons) leave spinal cord & innervate skeletal muscles
proper control of muscle fx requires continuous sensory feedback from each muscle
Golgi tendon organ (GTO) proprioceptive sensory receptor located in muscle tendon, detects tendon tension & rate of change of tension; causes inhibition of motor neurons; neutralizes contractile force on separate muscle fibres
contraction trigger involving muscle stretch reflex involves stretch of muscle (by muscle spindles)
stretch reflex prevents oscillation or jerkiness of body mvmt providing DAMPENING effect or smoothing fx
voluntary movements initiated by cerebral cortex by activating PATTERN of fx stored in lower centres which signal muscles
primary motor area topographical representation of muscles in body w/ more than 1/2 concerned w/ control of hands & speech; excitation of single neuron excites specific mvmt (not single muscle)
anterior part of premotor cortex generates MOTOR IMAGE for muscle mvmt, then excites complex patterns of mvmt
supplementary motor cortex stimulate BILATERAL mvmt
corticospinal tract most import pthwy, aka DIRECT PYRAMIDAL PTHWY, carries motor signals directly from primary motor cortex down sp. cord
direct pathways aka corticospinal tract; controls discrete & detailed mvmts esp. of distal segments of limb
extra pyramidal system include all motor pthwys in brain that are NOT part of pyramidal system
brain stem provides special control fx (ie. respiration, arterila pressure, cardiovasc., equilibrium & stereotyped mvmts of body); acts w/ cerebellum to control mvmts & maintain equilibrium
vestibular apparatus sensory organ detects sensation of equilibrium
semicircular ducts detect rate & direction of rotation of head in all 3 planes of space
utricle & sacculae responsible for informing brain of position of head w/ respect to gravity
cerebellum major role in timing of motor activities & in rapid smooth progression of mvmts
basal ganglia works with corticosp. syst. to plan & control complex patterns of muscle mvmts
spinal level of motor cortex programmed local patterns of mvmt
hind brain maintenance & axial body tome for standing & maintaining equilibrium
motor cortex complex patterns of mvmt & can bypass programmed patterns
cord patterns determined at birth, "hard-wired"
cerebral cortex all areas have extensive to-&-fro connections w/ deeper structures of brain; two halves of brain have INDEPENDANT capabilities for consciousness, memory storage, communcation & motor activity control
thalamus excitation of thalamus is necessary for almost all cortical activity; almost all pthwys from sensory organs pass thru thalmus to cortex
association areas of cerebral cortex receives & analyzes signals from multiple regions of brain
Wernicke's an association area responsible for language comprehension
pre-frontal association area helps plan complex patterns & sequences of motor mvmt
working memory ability of brain to store many pieces of info on short term basis, used to analyze new thoughts entering brain
Broca's association area responsible for motor patterns for word formation by exciting larynx, resp. syst & mouth muscles
limbic system association area concerned w/ behaviour, emotions & motivation
corpus callosum AND anterior commisure makes info stored in cortex of one hemisphere available to corresponding cortical areas of opposite hemisphere
corpus callosum required for boh sides of brain to operate
anterior commisure important role in unifying EMOTIONAL responses of 2 sides of brain
holistic theory a thought results from "pattern" of stimulation of many parts of nerv. syst. at the same time
consciousness continuing stream of awareness of either our surroundings or our sequential thoughts
memory traces memories caused by changes in sensitivity of synaptic tranmission <-> neurons as a result of prev. neural activity, forms new or facilitated pthwy; once established, can activate "thinking" to reproduce memories
short-term memory caused by continual neuronal activity resulting from nerve signals travelling around temporary memory trace thru circuit of reverberating neurons
intermediate memory temporary chemical &/or physical changes
long-term memory result of actual structural changes instead of only chemical changes
short- term to long-term memory must be consolidated for conversion; consolidation happens when actively repeating something, initiating chemical, physical & anatomical changes in synapes
reticular area of brain stem main part of nerv. syst. which controls excitation of cerebral cortex
positive feedback loop activation of cerebrum excites brain stem which activates cerebrum more leading "awake mind"
hypothalamus major part of limbic syst for its ability to control vegetative fx of brain closely related to behaviour
autonomic nervous system (ANS) activated by centres of spinal cord, brain stem & hypothalamus
sympathetic nerve fibres originate <-> T1 to L2 of sp. cord
parasympathetic nerve fibres originate from cranial & sacral nerves of sp. cord; 75% originate from CN X (vagus)
norepinephrine neurotransmitter released by most SNS fibres that supply blood vessels; vasoconstrictor
acetylcholine neurotransmitter released by most PNS fibres; stimulates all types of gastric glands to release secretions
sympathetic nervous system (SNS) pupil dilation, increased heart activity, blood vessel constriction
parasympathetic nervous system (PNS) pupil constriction, increased peristalsis, decreased heart rate
adrenal medulla releases epineph. & norepineph. into blood upon sympathetic stimulation; effects last 5-10x longer than direct sympathetic stimulation
mass discharge all portions of SNS discharge simultaneously; aka STRESS RESPONSE, allows person to perform greater stenuous physical act. otherwise possible
right side of heart pumps blood to lungs
left side of heart pumps blood to all body except lungs
ventricles supplies main forces of contraction
heart composed of atrial & ventricular muscle tissues & specialized excitatory & conductive fibres; cardiac muscle contraction lasts 15x longer than skeletal
intercalated discs cell membranes separating individual cardiac muscle cells
gap junction diffusion of ions from one cardiac muscle cell to the next
syncytium when one cell is excited, the action potential spreads to all
calcium unique to cardiac muscles for prolonged contractions
diastole period of relaxation when heart fills w/ blood; 75% of blood flows from atria to ventricles; AV valves open, during atrial systole they open, during ventricular systole they close
systole period of contraction when heart expels blood; 25% of blood pushed into ventricle when atria contracts; semilunar (SL) valves closed, atrial diastole they close, ventricular diastole they open
atrioventricular (AV) valves tricuspid & mitral valves; 1st heart sound which sounds low & long
semilunar (SL) valves pulmonary & aortic valves; edges of SL valves subject to greater mechanical stress than AV valves; 2nd heart sound which sounds short snap due to closing
papillary muscles & chordae tendinae prevent AV valves from bulging back into atrium during ventricular systole
Frank-Starling Mechanism the greater the stretch of heart during filling, the greater the contraction
ventricle relaxed AV open, SL closed
ventricle contracted AV closed, SL open
sinus node located in superior posterolateral wall of right atrium; sets rhythm of heart because it emits new impulses FASTER than AV or Purkinje; aka pacemaker
internodal pathways bundles of specialized fibres that connect sinus node & AV node
cardiac impulse delay delayed @ AV node due to fewer gap junctions <-> cells; also allows atria to contract & finish filling ventricles before ventric. contraction
atrialventricular (AV) bundles fibres that conduct impulse from AV node to ventricles
Purkinje fibres conduct impulse from AV bundle to all parts of ventricles 6x faster & 150x faster than AV node
cardiac output quantity of blood pumped into aorta per minute; mainly controlled by venous return
venous return quantity of blood flowing from veins into right atrium per minute; sum of all local blood flow from individual tissue segments of peripheral circulation
heart less efficient factors that increase total peripheral resistance increases cardiac output
heart more efficient factors that decrease total peripheral resistance would increase cardiac output; nerv. stimulation & hypertrophy of heart muscles -> better pump
systemic circulation supplies blood to all tissues except lungs
arteries transport blood under high pressure to tissues; contains 13% of total blood volume; control of pressure independant of local bl. flow & cardiac output
arterioles act as control conduits that release blood into capillaries
capillaries exchange of substances <-> blood & interstitial fluids
venules have pores only permeable to H2O & small molecular substances; collects blood directly from capillaries
veins transport blood from tissues back to heart; major reservoir of blood (64%)
pulmonary circulatory system contains 9% of total blood vol.; 25/8 mmHg (sys/dia)
blood pressure force exerted by blood against any unit area of vessel wall
resistance impediment to blood flow in vessel
total peripheral resistance resistance of entire systemic circulation
viscosity of blood determined by red blood cells
hematocrit %age of blood composed of cells
arterial compliance pulse pressure of heart affected by stroke volume output
spleen specific blood reservoir & destroys old blood red blood cells
red pulp area of spleen where RBC stored
microcirculation transport of nutrients to tissues & removal of cellular excreta
metaarterioles structure <-> arteriole & capillary
precapillary sphincter smooth muscle fibre around metaarteriole to control entrance of blood into capillary
intercellular cleft thin passageway <-> adjacent endothelial cells of capillaries
vasomotion on/off flow of blood thru capillaries; controlled by oxygen
diffusion means of substance transport in/out of capillaries
water smallest substance passes thru capill. pores
plasma proteins larger than capillary pores
interstitium spaces <-> cells of body; low concentrations of proteins
interstitial fluid fluid that fills spaces <-> cells of body
collagen long, strong structures in interstitium, provides tensional strength to tissues
proteoglycan filaments aka "brush pile", thin, coiled & form a mat of fine filaments
tissue gel combination of solid structures of interstitium & trapped fluid
collotid osmotic pressure osmotic pressure caused by plasma proteins
lymphatic system accessory route from interstitial space into blood & carries proteins & large particulate matter away from tissue spaces; 1/10 fluid filters into interstitium from capilliaries NOT reabsorbed & is returned to circulation
thoracic duct lymph flow from lower body, left head, left arm & chest
right lymph duct lymph flow from right neck & head, right arm & thorax
lymphatic endothelial cells overlap & act like valves pushed open by pressure & pushed closed by backflow
oxygen-lack theory of local blood flow inadequate levels of oxygen & nutrients cause blood vessels to relax & dilate
reactive hyperemia increased blood flow to tissues recently suffered of blood supply deprivation
active hyperemia increased blood flow to tissues highly active
nitric oxide vasodilating substance due to shear stress from increased blood flow
angiogenic vascular growth factors involved in reconstructing tissue vascularity in response to long-term changes in blood flow
angiotensin powerfully constricts all arterioles & mainly involved in arterial pressure regulation
vasopressin an antidiuretic hormone secreted by hypothalamus & acts to increase reabsorption of water by kidneys
histamine vasodilater substance released when tissues are damaged or inflamed but also involved in allergic reactions; causes bronchiolar constriction; secreted by gastric glands
increased arterial pressure constriction of arterioles & veins & increase cardiac pumping when occuring simultaneously
baroreptor nervous reflex initiated by stretch receptors which then send signals to CNS about changes in arterial pressure; when person stands after lying down baroreceptor maintains arterial pressure in upper body; located in large systemic arteries
chemoreceptors nerv. reflex involve receptos sensitive to oxygen lack, carbon dioxide & hydrogen ion excess; located in large systemic arteries; involved in maintaining arterial pressure at pressure lower than normal range
fx of red blood cells transports hemoglobin to deliver oxygen to tissues; do not rupture when squeezed thru capillaries due to excess of cell membrane
red blood cells (RBC) produced in bone marrow; matures from proerythroblast to reticulocyte stage gains hemoglobin & lose their nucleus; excess may impede blood flow; survives 120 days in bl. stream
RBC formation rate not controlled by concentration in blood stream but by their ability to transport oxygen
erythropoietin released from kidneys & liver triggered by low oxygen levels to produce more RBC
Vit B12 & Folic Acid critical for RBC maturatoin
interaction between hemoglobin & oxygen loose & reversible; hemoglobin helps to maintain oxygen pressure in tissues regardless of fluctuations of O2 concentration in alveoli (Buffer System)
iron important for formation of hemoglobin; free iron in blood -> "transferrin"; iron stored in cells -> "ferratin"; iron lost during blood loss; when RBC bursts iron release for storage in liver
hemoglobin transported by RBCs for delivery of oxygen; is broken down & converted into bilirubin when RBC cells burst; enhances transport of oxygen 30-100x
anemia deficiency of hemoglobin
white blood cells (WBC) combats infectious & toxic agents, specifically transported to areas of infection; recruited during inflammation
granulocytes are neutrophils, eosinophils & basophils; formed in bone marrow
phagocytosis are granulocytes & monocytes which help protect body & cellular ingests foreign invaders
lymphogenous tissues where lymphocytes & plasma cells are formed
neutrophils WBC capable of phagocytosing bacteria in circulating blood; already mature when it enters tissues, can only ingest small # of bacteria before dying; 2nd line of defence few hrs after inflammation (enters tissue via diapedesis)
monocytes inactive while in blood steam, only become activated once they enter tissues; formed in bone marrow
macrophage derived from monocytes; able to ingest many & large particles, can survive many months; actions of macrophages can injure healthy living tissues around injured area; responsible for presenting antigens to B & T cells
diapedesis cell squeezing thru small opening by sliding only a small portion of itself thru
chemotaxis mvmt of cells towards source of chemical sign; draws neutrophils & monocytes towards tissues in inflamed state
tissue macrophage first line of defence of tissue injury; phagocytic cells attached to tissues & remain after inflammation subsides
sinusoids of liver macrophage lined structure where inaders entering via GI tract enters portal blood & must pass thru
inflammation dramatic 2ndary changes observed after injury to tissue
margination sticking of cells to capillary walls near areas of inflammation
pus mixture of necrotic tissues, dead phagocytes, tissue fluids, etc found in areas of inflammation
eosinophils involved in specifically targeting parasitic invaders
basophils involved in allergic reactions & are similar to mast cells by liberating heparin (anticoagulant) & histamine (vasodilator) into blood
immunity ability to resist different types of organisms & toxins
acquired immunity doesn't develop until after body first attacked by disease/toxin; B & T cells basic types activated when exposed & reacts w/ specific antigens
innate immunity general processes for killing invaders
humoral cells aka B lymphocytes, acquired immunity that secretes antibodies which bind attacking agent; formed in bone marrow; secrete antibodies which bind antigen
cell-mediated cells T lymphocytes, type of acquired immunity that directly attack & destroy foreign agents; formed in thymus; directly bind to antigens using receptors
antigens specific chemical compounds that makes organism different from all others
lymph nodes contains majority of lymphocytes
spleen & bone marrow 2 types of lymph tissues that play important role in intercepting agents in circulating blood
helper T cells contributes to activation of B cells; most numerous type of T cells; regulates all immune fxs, destroyed/inactivated by AIDS virus
plasma activated B cells that have differentiated & producing antibodies
memory cells activated B & T cells circulated to & remain dormant in various lymph tissues to provide faster & potent response if body exposed to same antigen again
antibodies immunoglobin compounds that bind specific antigens
IgG most common immunoglobin
IgE immunoglobin primarily involved in allergic response
complement system grp of proteins that aid in destruction of antigens by promoting opsonization, phagocytosis, agglutination& activation of basophils & inflam. response
cytotoxic T cells directly attacks & kills microorganisms
suppressor T cells suppresses fx of other T cells
immunization process which acquired immunity is induced by injecting dead/attenuated organisms &/or altered toxins
goals of respiration to provide oxygen to & to remove carbon dioxide, from tissues
pulmonary pressure inflow/outflow of air <-> atmosphere & lung alveoli
lungs expansion/contraction 2 ways: upward & downward, elevation & depression
abdominal muscles provides additional force for expiration during heavy breathing
exernal intercostals muscles that raise rib cage (inspiration)
internal intercostals muscles that pull down on rib cage (expiration)
muscles of inspiration external intercostals, SCM, serratus anter., scalenes
muscles of expiration internal intercostals, abdom. recti
pleura fluid w/in which lungs "float" & provides lubrication for mvmts of lungs
pleural pressure pressure of fluid in space <-> lung & chest wall normally maintained at slightly negative value
lveolar pressure pressure of air inside alveoli of lung; alv. pres. of O2 & CO2 determined by rate they pass in/out of blood & alveoli (alveolare ventilation)
air to flow INTO lungs pressue inside alveoli need to be less than atmospheric pressure
transpulmonary pressure difference <-> alveolar pressure & pleural pressure
elastic forces of lungs 1/3 of total lung elasticity & mainly due to presence of elastin & collagen fibres; 2/3 try to collapse alveoli by surface tension
surfactant fluid lining alveoli greatly reduce surface tension, helps to reduce amount of pressure required to keep lungs expanded
respiration major limitation to intensity of exercise a person can perform
tidal volume volume of air inspired/expired w/ each normal breath (500 mL)
total lung capacity maximum volume which lungs can be expanded w/ greatest possible effort (5800 mL)
alveolar ventilation rate at which new air reaches gas exchange areas of lungs
dead air space air that never reaches gas exchange areas of lungs (air in nose, pharynx, trachea)
cartilage rings structures help keep trachea & bronchi open allowing easy passage of air thru them
bronchioles no cartilage & is composed of smooth muscle, only kept from collapsing by transpulm. pressure
mucus coats resp. passageways helping to keep the moist & trap small particles
nasal cavities part of resp. passageways first to warm, humidify & filter air
turbulent precipitation larger particles in air filtered by hairs located @ entrance of nostrils
alveolar macrophages removes very small particles settled in alveoli
partial pressure rate of diffusion of each resp. gases directly proportional to pressure caused by each gas alone; exerted when gases dissolved in water or body tissues; greater for oxygen in alveoli than pulm. capillaries
carbon dioxide more soluble in water; by-product as a reaction of oxygen w/ foodstuffs; contributes most to acid-based balance of body fluids
respiratory membrane where gas exchange in lungs must pass thru; comprised of capillary, interstitial space & alveoli wall; rate of mvmt of material thru resp. membrane can be affected by changes to membrane itself (increased thickness/decrease surface area)
ventilation of perfusion ratio balance <-> alveolar ventilation & blood flow
deoxygenated blood flow inadequate VENTILATION to area of lungs receiving adquate blood flow
inadequate blood flow to lungs receiving adequate ventilation oxygen will be breathed back out
partial pressure of oxygen greatest in alveoli, less in blood stream, even less in tissue; lower in capillaries because O2 used by cells to create energy
partial pressure of carbon dioxide greatest in tissue, less in blood, even less in alveoli
pressure difference to move carbon dioxide less than those needed to move oxygen
interaction of oxygen with hemoglobin loose & reversible; binding of oxygen to hemoglobin displaces carbon dioxide, CO2 released from blood stream in lungs because binding of O2 makes hemoglobin a stronger acid
arterial blood saturated w/ 97% oxygen
venous blood saturated w/ 75% oxygen
Buffer system fx of hemoglobin helping maintain oxygen pressure in tissues regardless of fluctuations of oxygen concentration in alveoli
carbon anhydrase enzyme present in accelerated conversion of carbon dioxide & water into carbonic acid
bicarbonate form of carbon dioxide (approx 70%) transported in blood; excess CO2 causes kidneys to release bicarbonate to readjust hydrogen ion concentration; also secreted by pancreas to neutralize stomach acid & pH of chyme
medulla & pons areas of brain stem where respiratory centre mainly located
dorsal respiratory group of respirator centre mainly causes inspiration & generates basic rhythm of respiration
ventral respiratory group of respiratory centre mainly causes expiration & inspiration; inactive during normal quiet breathing, is important when high levels of pulm. vent. required (during exercise)
pneumotaxic centre of respiratory centre mainly controls rate & pattern of breathing; switches off inspiration
oxygen does not have direct effect on resp. centre, mainly acts to control resp. thru peripheral chemoreceptors
inspiration controlled by dorsal resp. group of resp. centre; CO2 & hydrogen ions increase strength of inspiration
peripheral chemoreceptors responds rapidly to excess CO2 at onset of exercise
strenuous exercise up to 20x increase in O2 consumption & CO2 formation --> alveolar ventilation increases, arterial PO2, PCO2 & pH remain the same; increase in resp. mainly due to stimulation by higher brain centre & body mvmt eliciting proprioceptive reflexes
smooth muscles found in wall of GI tract
GI muscle fibres are of smooth muscles; less excitable during sympathetic stimulation; excitable by stretching of muscle
enteric nervous system (ENS) intrinsic nervous system of GI
myenteric plexus of enteric nerv. syst controls mvmts in GI system
submucosa plexus of ENS controls secretion & local blood flow in GI system
movements in GI tract propulsive & mixing
peristalsis basic type of propulsive mvmt in GI, involves formation of contractile ring in gut then moves forward which moves material in front, forward; stimulated by distension
mixing formation of intermittent constrictive contraction every few centimeters along the gut
splanchnic circulation supplies gut, spleen, pancreas & liver
portal vein vessel of which blood from gut, spleen & pancreas flow into liver
GI bacterial removal running of venous blood from GI tract thru sinusoids of liver
non-fat / water soluble nutrients absorption absorbed from gut into blood stream & sent to liver for storage/processing; final products of carb digestion from sm. intestine absorbed into portal blood
fat based nutrients absorption absorbed from gut into lymphatic syst., then into bloodstream by-passing liver
blood flow of GI increases when gut becomes active (after meal); decreased to GI by SNS
mucous for lubrication & protection of GI tract; mainly secreted in esophagus to provide lubrication for swallowing; mucous secreted by stomach has alkaline pH which protect underlying wall from acidic & proteolytic stomach secretions; regulated by local nerv sy
trigger of GI secretions mechanical pressure of food, various hormones & nervous reflexes
saliva contains mucous & digests carbs by ptyalin enzyme; also helps maintain health of oral tissue by washing away / destroying bacteria; released by PNS
hydrochloride needed for activation of pepsinogen into pepsin & thus needed for proper protein digestion in stomach
intrinsic factor a gastric secretion essential for vit B12 absorption in small intestine
stomach secretes hydrochloric acid, pepsinogen, intrinsic factor, gastrin & mucous
hydrochloric acid stimulated by gastrin & histamine
substances released when meat or protein foods enter stomach Gastrin -> histamine -> HCl -> pepsin
chyme in duodenum, main stimulus for pancreatic secretions
pancreas secretes digestive enzymes for carbs, protein & fat; also secretes bicarbonate; secretion stimulated by acetylcholine, cholecystokinin & secretin; secretes amylase enzyme after chyme enters duodenum for starch digestion completion (15-30 min)
secretin secreted by upper small intestine in response to presence of stomach acid which causes pancreas to release bicarbonate ions
cholecystokinin (CCK) released in duodenum in presence of fats, protein digestion & long-chain fatty acids in chyme which in turn, triggers release of bile
cholesterol used to make bile salts
small intestine responsible for nutrient absorption
cellulose undigestible form of carbs by humans
ptyalin salivary enzyme involving carb digestion in mouth
enterocytes enzymes splitting various disaccharides (sucrose, lactose, maltose)
pepsin secreted by stomach important for protein digestion
protein digestion must be in di & tri peptides &/or amino acids before being absorbed into enterocytes of sm. intest.
pepsidase digests peptides into amino acids then absorbed into bloodstream
emulsification critical for proper fat digestion, involves fat globules broken into wee sizes; bile is emulsifier
sodium absorption creates electrochemical gradient across intestinal epithelial cells which promotes chloride absorption
sodium co-transport process which most products of protein digestion is absorbed; galactose & glucose require sodium as co-transp.; fructose does not
colon bacteria capable of producing vit B12, thiamine, riboflavin & vit K
Created by: LInda_J on 2006-06-03



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