Unit 3 Flashcards
What are the functions of the Muscular System?
- move the body
- maintain posture
- protect and support
- secrete cell signals
- regulate elimination of materials
- produce heat
How does the muscular system move the body?
- move bones
- make facial expressions
- speak
- breathe
- swallow
How does the muscular system maintain posture?
- stabilizes joints to maintain posture
How does the muscular system provide protection and support?
- package internal organs and hold them in place
- ex. diaphragm is separated from abdominal cavities
How does the muscular system secrete cell signals?
- myokines have autocrine, paracrine, and endocrine functions
How does the muscular system regulate the elimination of materials?
- circular sphincters control the passage of materials at orifices and sphincters
How does the muscular system produce heat?
- muscle contractions produce heat and regulate body temp
What do myokines in the bone do?
-leads to osteogenesis
What do myokines in the brain and nerves do?
- leads to cognitive function
What do myokines in adipose tissue do?
- leads to lipolysis browning
What do myokines in the liver and pancreas do?
- leads to glycogen and fat metabolism, insulin secretion
What do myokines in the intestines do?
- leads to anti-tumorigenesis, gut hormone secretion
What do myokines in the skeletal muscle do?
-leads to glucose, fat, protein metabolism, muscle development and proliferation
What is excitability?
- ability to respond to a stimulus by changing electrical membrane potential (sarcolemma potential)
- ach released from major neurons, some contain AP
What is conductivity?
- involves sending an electrical change down the length of the cell membrane
- carrying of an AP which requires v-gated NaK channels
What is contractility?
- exhibited when filaments slide past each other enabling muscles to cause movements
What is concentric contractility?
shorter muscles with more overlap in between
What is extensibiity?
- ability to be stretched
What is elasticity?
- ability to return to the original length after a lengthening or shortening
How are muscle fibers developed?
- multiple myoblasts fuse to form each multi-nucleated skeletal muscle fiber
- myoblasts to satellite cells with 2 mini muscle fibers to a satellite cell with one muscle fiber
Why do some muscle fibers have satellite cells ?
- for support and repair of muscle fibers
What is the muscle heirarchy?
- muscle (organ) to muscle (tissue) to muscle fiber (cell)
What tissue is a muscle made out of?
-Nervous Tissue
- Blood vessels
- Connective tissue
What is the epimysium?
- dense CT layer that surrounds the outer surface of the whole muscle
What is the perimysium?
- dense CT layer around and between fascicles that house many blood vessels and somatic nerves
What is the endomysium?
- a delicate layer of loose CT that provides electrical insulation, capillary support, and binding of neighboring cells between muscle fibers
What is a tendon?
- fusion of the epimysium, perimysium, endomysium, which extends through the entire muscle and then connects to bone
- cordlike/ rope-like structure of dense regular CT
What is an aponeurosis?
- thin sheet of dense irregular tissue that goes in all different directions
What is the deep fascia and what does it do?
- dense irregular CT, just superficial to the epimysium
- separates individual muscles and binds muscles with similar functions
What is the superficial fascia and what does it do?
- areolar and adipose connective tissue layer superficial to the deep fascia
- separation of muscles from skin
What is a motor unit?
- a lower motor neuron and all the muscle fibers it controls
- fibers of a motor unit are dispersed, not just a clustered compartment
Is the numver of fibers a neuron innervates set?
no
Describe small motor units?
-less fibers (less than 5)
- performs small but accurate movements (eye movement)
Describe big motor units?
- allows for the production of a large amount of force
- has 100-1000s of fibers
- postural muscles and limbs
What is the sarcolemma?
- outer plasma membrane of muscle fibers
- where AP are carried, has v-gated channels
What is the sarcoplasm?
- contains mitochondria and multiple nuclei
What are myofibrils?
- densely packed into muscle fibers, containing contractile proteins
- organelle, not cell
- has sarcoplasm
- takes up the majority of space
- has high ATP usage
-uses actin and myosin proteins
What is the sarcoplasmic reticulum?
- covers entire myofibril (mesh-like)
- raps around each myofibril using t-tubule
What do t-tubules do?
- takes AP from the outside of fiber into the inside
- has terminal cisterna of SR on each end of it like a sandwich (also called a triad)
- changes electrical signal to chemical signal (AP- Ca2+)
Where do motor neurons innervate muscles?
-neuromuscular junction
- usually located in the mid-region of the muscle fiber
What are the parts of the neuromuscular junction?
- synaptic knob
- synaptic cleft
- motor end plate
Why is the end plate highly folded?
to increase Surface area and increase the number of membranes and receptors
Describe how EPP is reached and ACH is released?
- An AP is conducted down the MN axon results in an influx of Ca2+ through the opening of v-gated Ca2+ channels at the synaptic knob
- Ca2+ binds to ACH-filled synaptic vesicles triggering exocytosis and the release of ACH into the synaptic knob
- ACH diffuses across the synaptic cleft and binds to ACH Receptors (chemically gated cation channels) found on the motor end plate region of the sarcolemma
- opening of cation channels causes and EPP (depolarization)
What is Excitation Contraction coupiling
- An AP is conducted down the sarcolemma surrounding the muscle fiber and moves into the cell through the t-tubules (with NaK+ v-gated channels)
- AP is conducted down the sarcolemma surrounding muscle fiber and moves into cell through t-tubules (through NaK+ v-gated channels)
- DHP receptors within t-tubules stimulate the opening of Ca2+ receptors at SR resulting in the movement of Ca2+ from SR into the sarcoplasm
- An AP initiated at the motor end plate travels along the sarcolemma and down t-tubules surrounding myofibrils (NaK v-gated)
What is the sarcolemma AP graph?
- RMP -90
- Threshold: End plate potential -90 - -65
- Depol: Na+ V-gated channels open - 65 - +30
- Repol: Na+ v-gated channels close K v-gated open, K+ efflux, +30 - -90
What is a sarcomere?
- smallest contratile unit?
Where is a sarcomere located?
along microfile, along entire length
What is a sarcomere made of?
thin and thick filaments
What are thick filaments made of?
myosin
what is a thick filament?
- extends from z- disks to m-line through myosin (centered at M-line)
- binds ATP one it detaches from actin
- uses ATP to reset, gets in ready position to be able to bind actin
- bound to ATP and PI
What are thin filaments?
- has actin and regulatory proteins (troponin and tropomyosin)
- actin contains myosin binding site
- troponin (attached to tropomyosin) contains binding site for Ca2+
- topomyosin directly covers myosin binding sites on actin
What happens if there is no calcium in the thin filaments?
no binding of filaments
What happens when there is calcium in the thin filaments?
- binding sites available for myosin to bind
- confirmation change is regulatory protein resulting in removal of tropomysin from binding sites on actin
What does troponin do?
contains binding site for calcium
What does tropomyosin do?
directly covers myosin binding site on actin
What is the sarcomere doing when the muscle is relaxed?
sarcomere relaxed
What happens to the sarcomere when the muscle is contracted?
sarcomere contracted
- z disks move towards m line
- I band gets smaller/ disappears
- H zone gets smaller/ disappears
What is the m-line?
- cross-section of sarcomere
- thick filaments and accessory points
What is the h-zone?
- cross-section of sarcomere
- thick filaments only
- subset of A band
What is the A-band?
- cross-section of sarcomere
- thick and thin filaments
What is the I band?
- cross-section of sarcomere
- thin filaments and connectin
- no thick filaments
- half on one sarcomere half on the other
What is the z-disk?
- cross-section of sarcomere
- thin filaments, connectin, accessory proteins
What does connectin do?
- provides stability and elasticity to sarcomere
- connects z-disks and helps maintain the placement of thick filaments in btwn the thin filaments
- compressed during contraction of the sarcomere but its elasticity allows it to uncoil during relaxation
Where is dystrophin located?
- primarily in muscles used for movements (skeletal muscle) and cardiac muscle
- small amounts are present in nerve cells of brain
What does dystrophin do?
- provides structural link btwn muscle cytoskeleton and extracellular matrix while maintaining muscle integrity
- key in maintaining the mechanical stability of skeletal muscle by liking actin filaments in sarcomeres to the sarcolemma
What does a lack of dystrophin do?
- causes these cells to be increasingly fragile and prone to damage
What is the sliding filament model of muscle contraction?
- z disks move towards m line
- I band gets smaller/ disappears
- H zone gets smaller/ disappears
Where is the myosin head and where does it face?
- head at end of A-band
- facing towards z-disk
What is the cross-bridge cycle
- Ca2+ binding (if no Ca2+ it’s just relaxed)
- Crossbridge formation (has ADP and phosphate
- Power stroke (ATP goes to m-line)
- Myosin Release/ detachment (ATP must bind)
- Myosin reset
What is exposure of myosin to the binding site on actin?
- Ca2+ binds troponin, inducing a conformation change in regulatory protein complex (troponin and myosin)
- tropomyosin rotates exposing binding sites on actin
What is crossbridge formation?
- myosin heads binds to exposed binding site on actin
- ADP and Pi are bound to myosin when binding occurs
- a-band stays the same, H-band disappears because z-disks move closer, I-band gets smaller
What is a power stroke?
-myosin heads swivels toward the center of the sarcomere, pulling along attached thin filament, moving it towards m-line
- ADP and Pi release
What is myosin release?
-cross-bridge detachment
- ATP binds to the ATP binding site on myosin head as myosin head releases from binding site on actin
What are the steps in skeletal muscle relaxation?
- termination of nerve signal and ACH release from motor neuron
- closure of ACH receptor causes cessation of EPP
- return of muscle to original position due to its elasticity which is largely a contribution of connectin
What does the termination of a nerve signal and ACH release from a motor neuron do?
- hydrolysis of ACH by ACHE (ACH removed and stops signal)
What does the closure of ACH receptor and cessation of EPP do?
- no further AP generated
- no excitation
- no Ca2+
What are the metabolic processes for generating ATP?
- available atp and phosphate transfer to adp
- glycolysis
- aerobic cellular respiration
- myosin kinase
- creatine phosphate
Is O2 required for available atp and phosphate transfer to adp?
no
Is O2 required for glycolysis?
no
Is O2 required for aerobic cellular respiration?
yes
Describe available atp and phosphate transfer to adp?
- o2 not required
- limited ATP available
- ATP produced from creatine P in limited amounts
Describe glycolysis?
-no O2 required
- more rapid production of ATP than aerobically
- lesser amounts of ATP are made than aerobically
- fuel is glucose typically from glycogen breakdown and blood
What is the fuel for glycolysis?
- glucose typically from glycogen break down and blood
Describe aerobic cellular respiration?
- O2 required
- slower production of ATP than glycolysis
- greater amount of ATP made than glycolysis
- fuel: pyruvate (glycolysis product), fatty acids, amino acids with NH2 removed
What is the fuel for aerobic cellular respiration?
- pyruvate ( a glycolysis product), fatty acids, amino acids with NH2 removed
What is the myosin kinase metabolic process for generating ATP?
- ATP releases energy when least phosphate is removed, resulting in a surplus of ADP within the muscle fiber
-ATP to ADP + P - enzymes in muscle catalyze production of ATP by phosphate transfer
What does myosin kinase do?
- catalyzes the transfer of a phosphate from 1 ADP to another ADP forming ATP and AMP
What is the creatine phosphate metabolic process for generating ATP?
- like a phosphate savings account
- requires muscle to resynthesize energy from other sources including high energy creatine phosphate
- reaction is reversible using ATP to replenish the creatine phosphate supply in resting muscle
How long do stored ATPs last?
- in muscle cell the stored ATPs spent after a few seconds of intense exertion
What does creatine kinase do?
- catalyzes the transfer of a phosphate from creatine to phosphate to ADP to ATP in active muscle
How does glycolysis work/ what is the goal?
- No O2, happens in cytosol
- glucose from muscles (glycogen) or through blood is converted to 2 pyruvate molecules releasing 2 ATP per glucose molecule
How does glycolysis work in a high O2 environment?
- in a high O2 environment, pyruvate moves into the mitochondria to continue to make ATP through Aerobic cellular respiration
How does glycolysis work in a low O2 environment?
- pyruvates are converted into lactate by lactate dehydrogenase
- in the presence of O2 lactate can be converted back to pyruvate within the mitochondria of skeletal or cardiac muscle fibers to continue with aerobic cellular respiration
- lactic acid cycle
What is the lactic acid cycle?
- occurs as lactate is transported back to the muscles
How does aerobic cellular respiration occur?
- requires energy source (glucose or triglycerides) and O2
- myoglobin is present in sarcoplasm binds to O2
- pyruvate (produced by glycolysis) enters the mitochondria where oxidative phosphorylation occurs, producing large amounts of ATP
- works slower than glycolysis but produces more ATP
What is the byproduct of aerobic cellular respiration?
CO2
What are the types of muscle fibers categories?
- based on type of contraction (power or speed + duration)
- or the primary means of supplying ATP (oxidative or glycolytic
What is the power muscle fiber group?
- related to the diameter of muscle fiber
- larger= more powerful
What is the speed and duration muscle fiber group?
- speed and duration related to the type of myosin ATPase, quickness of AP prorogation and Ca2+ release and reuptake by SR
-has fast twitch fibers
What are fast twitch fibers?
- more powerful and have quicker and briefer contractions than slow twitch fibers
What is the oxidative muscle fiber group?
- fatigue-resistant red fibers
- have extensive capillaries many mitochondria and a large supply of myoglobin to support aerobic cellular respiration
What is the glycolytic muscle fiber grou[?
- fatigueable white fibers
- have fewer capillaries and mitochondria
- smaller supply of myoglobin and large glycogen reserves to support aerobic cellular respiration
What are the skeletal mucsle fiber types?
- slow oxidative (type 1)
- fast oxidative (type 2a)- intermediate
- fast glycolytic (type 2b)- fast anaerobic
What is the slow oxidative muscle fiber group?
- contractions are slower and less powerful
- high endurance since ATP is supplied aerobically
- about 1/2 the diameter of other fibers
- red due to myoglobin
What is the fast oxidative muscle fiber group?
- fast and powerful contractions
- primarily aerobic respiration, but lower O2 delivery
- intermediate size
- light red
What is fast glycolytic/ fast anaerobic muscle fiber gorup?
- fast and powerful contractions
- brief contractions as ATP is produce anaerobically
- largest size
- white in color due to a lack of myoglobin
Is a muscle fiber the same cell type?
no a mixture of cell types make up a muscle fasicle
How do muscle fibers vary?
- proportions of fiber types in differnt muscle groups
- relative amount of fiber type
What is an example of varying proporitons of muscle fibers containing different muscle groups?
- hand muscles have high percent of fast glycolytic fibers for quickness
- back muscles have a high percent of slow oxidative fibers to continually maintain postural support
How is the amount of muscle fiber types determined?
- mostly genetic but can be altered through training
What is an example of muscle fiber types varying?
- long distance runners have a higher proportion of slow oxidative fibers in legs
- trained sprinters have a high percent of fast glycolytic fibers
What is a twitch?
-brief contraction due to a single stimulus
- The minimum voltage that triggers a twitch is a threshold
What are the twitch periods?
-latent
- contraction period
-relxation period
What is the latent twitch period?
- time after stimulus, but berfore contraction
- no change in tension
What is the contraction period of muscle twitchs?
- time when tension is increasing
- begins as power stroke pulls thin filaments
What is the relaxation period of muscle twitches ?
- time when tension is decreasing to baseline
- begins with crossbridge release
- generally lasts longer than contraction period
What are we measuring when we look at muscle twitches?
- tension, NOT VOLTAGE
What is motor unit recruitment/ summation?
- muscle is repeatedly stimmulated
What happens as voltage increases?
more units are recruited to contract
How do muscles exhibit varying degrees of force?
- varying degrees of muscle units recruited
- few to lift pencil
- many to lift suitcase
What is motor unit recruitment order based on?
- size of the motor unit
- small first and large last
What is wave summation?
-relaxation between twitches is incomplete
- contractile forces add up to produce higher tensions
-20-40 stmulli per second
How many stimuli occur per second in wave summation?
-20-40
How many stimuli occur per second in tetany?
-40-50
What is incomplete tetany?
- each twitch reaches maximum peak
- tension increases at twitches partially fuse
When does incomplete tetany become tetany?
- if frequency is further increased
- straight line without relaxaiton
What does a high frequency stimuli lead to?
fatigue
What is muscle tnesion?
-resting tension of a muscle
- background tension
When does muscle tone decrease?
during sleep
What causes muscle tone?
- generated by random involuntary nervous system stimmulation of a muscle
- motor unit changes so the unit is not fatigued
What is isometric contraction?
- tension is increased but its insufficient to over come resistance
- muscle length stays the same
what does a sustained isometric contraction cause?
- higher blood pressure
What is an isotonic contraction?
-muscle tension overcomes resistance resulting in movement
- tone stays constant, lenth changes
What are the types of isotonic contractions?
- concentric
- eccentric
What is a concentric contraction?
- muscle shortens as it contacts
- sliding filament theory
What is the tension a muscle produces dependent on?
- its length at the time of stimmulation
What is a eccentric contraction?
-muscle lengthens as it contracts
- calf lengthens when going up hill
What type of length generates the max contractile force?
- resting length
Why does a fiber at resting length generate a max contractile force?
- optimal overlap of thick and thin filaments
- actin and myosin heads have a good grip
Why do fibers at a shortened length generate a weaker force?
- filament movement is limited
- already close to z-disk
Why do fibers at an extended length generate a weaker force?
- minimal thick and thin filament overlap for crossbridge formation
- actin and myosin don’t have a good grip
What are the functions of the digestive system?
- ingestion
- motility
- secretion
- digestion
- absorption
- elimination
What is ingestion?
- introduction of solid and liquid nutrients through the oral cavity
What is motility?
- movement of materials due to muscle contractions throughout the gi tract
What is secretion?
- production and release of materials associated with digestion
- pancreas has digestive enzymes
- live has bile
What is digestion?
- breakdown of ingested materials to facilitate absorption
- mechanical and chemical
What is mechanical digestion?
- mastication, occurs in oral cavity
What is chemical digestion?
- uses enzymes to change chemical strucutre
What is absorbtion?
- transport of digested material across a membrane and into the blood/ lymph and small intestine
What is elimination?
- expulsion of ingestible materials from rectum and anus
What is the accessory digestive system?
- assists in the digestion of food
- some produce secretions that empty in to GI tract
What is the Gi tract?
- the continuous tube that transports food through the body while breaking it down into smaller, absorbable components
What is the GI tract made of?
- tissue layers called tunics
What happens in the oral cavity?
- mastication begins mechanical digestion
- saliva has salivary amylase which initiates the digestion of starches
- food is mixed with saliva to form a bolus
What does the pharynx do?
- bolus moves from the oral cavity to the pharynx during swallowing which is facilitated by mucus secretion s
What does the esophagus do?
- transports bolus from pharynx to stomach
- lubricated by mucous secretions
What happens in the stomach?
- primarily storage
- bolus mixed with gastric secretions by smooth muscle contractions
- secretions from epithelial cells of the stomach
- chyme is formed from mixing
What is the secum?
where material moves from small intestine
- contains appendix
- part of large intestine
What are the layers of the GI tract from the inside out?
- lumen
- mucosa,
- epitheleal tissue
- connective tissue,
- smooth muscle
What is the submucosa layer?
- vascularized layer of CT found below the mucosa
- contains submucosal nerve plexus and mucosa-associated lymphatic tissue (MALT) helps with immunity
What are the layers of the muscalaris?
- inner circular layer
- outer longitudinal layer
- sphincters
- also has myenteric nerve plexus
What does the muscularis control?
-mixing
- propulsion
What is the inner circular layer of muscle?
- constricts tube lumen
What does the outer longitudinal layer of muscle do?
- contractions shorten tube
What do sphincters do?
- thichkened regions control the movement of materials through GI tract
What is mixing?
- back and foward motion that lacks directional movement
- blends ingested material with secretions
What is propulsion?
- directional movement of materials through the GI tract
- occurs by peristalsis
What is peristalsis?
- sequential contraction of muscularis
- gi tract moves like a wave
What is the adventitia?
- areolar CT
- found outside the peritoneal cavity
What is the serosa?
- areolar CT
- covered by visceral peritoneum
- found within peritoneal cavity
What is the mesentery?
-double layer of visceral peritoneum that supports, suspends, stabilizes, intraperitoneal gi tract organs
- contains blood and lymph vessels, nerves between folds
What is the peritoneum?
- serous membrane associated with abdominal pelvic cavtiy
What is the parietal peritoneum?
- lines inside surgace of abdominal wall, outer layer
What is the visceral peritoneum?
- serous membrane reflecting over and covering internal organ surface
- double layer forms mesentery
What is the peritoneal cavity?
- potential space between two layers
- lubricating serous fluid secreted from both layers
- allows organs to move freely
What is the intraperitoneal organs?
- organs completely surrounded by visceral peritoneum
- includes stomach, small intestine, lare intestine
What are the retroperitoneal organs?
- lies directly against the posterior abdominal wall
- only anterolateral portions covered the peritoneum
- includes most of the duodenum, pancreas, ascending colon, descending colon, rectum
What is the enteric nervous system?
- sensory and motor nuerons within submucosal plexus and mesenteric plexus
- innervates smooth muscle and glands of GI tract
- coordinates mixing and propulsion reflexes
What is the autonomic NS of the gi tract?
- parasympathetic innervation promotes gi tract activity
- sympathetic innervation opposes gi tract activity
What are baroreceptors?
- detects stretch in gi tract wall
What are chemoreceptors?
- monitor chemical contents in lumen
What are reflexes in the ANS or ENS initiated by?
- in response to receptor input
What is a short reflex?
- local reflex only involves ENS coordinates small segments of gi tract
What is long reflex?
- involves sensory input to CNS and autonomic motor output and coordinates gi tract motility, secretions, accessory digestive organs
What is hormonal control of the digestive system?
- several hormones participate in regulation of digestive which will be addressed with the organs that secreted them
Where does mechanical digestion begin?
- oral cavity with the tongue and teeth
How many teeth do we have?
- 20 denticious/ baby teeth
- 32 permanent teeth
What does saliva do?
- moistens ingested food to form a bolus
- is secreted from salivary glands in response to food
- contains antibacterial substances that inhibit bacterial growth in oral cavity
What do lysozyme and antibodies do?
- inhibit bacterial growth in oral cavity
What glands help secrete saliva?
- parotoid
- submandibular
- sublingual
What is the pharynx?
- shared patway for air and food
- contains nasopharynx and laryngopharynx
- mucous secreted here facilitates swallowing of bolus
What does teh laryngopharynx play a part in?
digestion
What does the nasopharynx play a part in?
- respiratory
What does the esophagus do?
- normally collapsed passageway connecting pharynx and stomach
- ## passes through esophogeal hiatus
What is the esophageal hiatus?
- opening in diaphragm
What do peristaltic contractions do?
- help with swallowing
What is the superior esophageal sphincter?
- connected ring of circular skeletal muscle at the superior end where esophagus and pharynx meet
- closed during air inhalation
What is the inferior esophageal sphincter?
- connected ring of circular skeletal muscle at inferior end
- not strong enough by itself to stop stomach contents from regurgitating, diaphragm muscles assist
What are the phases of swallowing?
- voluntary
- pharyngeal
- esophogeal
What is the voluntary phase of swallowing?
- bolus is pushed by toungue against hard palate and then goes to oropharynx
What is the pharyngeal phase of swallowing?
- involuntary
- soft palate and uvula elevate and close of nasopharynx
- bolus moves into oropharynx
- epiglottis closes over laryngeal opening
What is the esophogeal phase of swallowing?
- involuntary
- soft palate, uvula, epiglottis return to the pre-swallowing position
- superior esophageal sphincter closes
- peristaltic contractions of the esophageal muscle push bolus toward the stomach
- inferior esophogeal sphincter opens
- bolus passes through esophagus and enters stomach
What does the stomach do?
- receives bolus from esophagus
- mixes materials stored with gastric secretions and digestive enzymes forming chyme
- pressure gradient moves contents toward pylorus opening pyloric sphincter
Where does chyme go?
- from the stomach to the duodenum
- smal volumes of chyme enter the duodenum before the sphincter closes
What controls chyme movement?
- movement into the duodenum is controlled by pyloric sphincter
- pressure gradient moves it towards the pylorus
How does food move through the stomach?
- contractions of smooth muscle in stomach wall mix bolus with gastic secretions to form chyme
- peristaltic waves result in pressure gradients that move stomach contents and pyloric sphincter
- pressure gradient increasese force in pyloric sphincter
- pyloric sphincter opens and a small volume of chyme enters duodenum
- pyloric sphincter closes and retropulsion occurs
What cells are in the gastric pit?
- surface mucous cells
- mucous neck cells
What do surface mucous cells do?
- continuolsy secrete alkaline product containing mucin that helps prevent ulceration of the stomach lining
- protects stomach lining
What do gastric glands do?
- expells gastric secretions into stomach thorugh gastric pit
What are the chief cells of the gastric glands?
- gastric lipase
- zymogen granules
What does gastric lipase do?
- plays limited role in fat digestion
What are zygmogen graules?
- primarily contain pepsinogen which is activated by HCL to form pepsin
What does pepsin do?
- chemically digest denatured proteins into oligopeptides
What are g-cells?
- gastrin
What does gastrin do?
- hormone that stimulates stomach secretions and motility
What is the intrinsic factor of parietal cells?
- required for absorption of B12 in the illeum
- necessary for production of normal erythrocytes
What does hcl do for parietal cells?
- responsible for stomach PH
- converts inactive pepsinogen to active pepsin
- kills most microorganisms entering stomach and helps break down mmaterials
What initiates the cephalic reflex?
-initiated by thought, smell, sight and tast of food
What is the effect of the gastric reflex?
- presence of food in stomach causes releases of gastrin which targets stomach to increase the force of contraction and release of secretions
- enhances what was started at cephalic phase
What is the effect of the cephalic reflex?
- stomach stimulated to increase its force of contraction and release of secretions
What initiates the intestinal reflex?
- chyme in duodenum
What does the intestinal reflex cause?
- also causes release of cholecystokinin(CCK) which decreases secretions and contractions in stomach
- acidic chyme causes release of secretin from duodenum and inibiting release of secretions
What does the liver do?
- produces bile
- cotains water, bicarbonate ions, nak pigments, cholesterol. lechitin, mycin
What do bile salts and lecithin do?
- helps manually digest lipids
What is hepcidin?
hormone released from liver that inhibits iron absorbtion
What does the gallbladder do?
- stores, concentrates, releases bile
- bile is transported through duct system into duodenum
What does the pancreas do?
- pancreatic juice released into duodenum through hepatopancreatic ampulla
- exocrine (acinar) cells release digestive enzymes
- biocaronate released from duct cells neutralizes ph of chyme entering the duodenum
What are the enzymes of the pancreas?
- amylase
- lipase
- inactive protases
- nucleases
What does amylase do?
-breaks down carbs
What does lipase do?
- breaks down fats
What does inactive protases do?
- breaks down proteins
What does nucleases do?
-breaks down rna and dna
What are the steps of amalyse?
- amylas formed by pancreas and decreted into small intestine
- amylase continuos digestion of starch by brush border enzymes embedded within the epitheleal lining of small intestine resulting in production of glucose
- molecules absorb into blood
Is a brushborder enzyme needed for lipase?
no
How does lipase work?
-bile salts take big lipids and break them down through micells
- tryglycerides are broken down into monglyceride and tree fatty acids
- must be like this to enter intestinal cells but in intestinal cells it reforms into tryglyceride
- needs to be repackaged into chylomicrons which can move out of cell and into lymph
What are the triglyceride molecules?
- gastric lipase
- lingual lipase
- pancreatic lipase
Where does trypsin come from and what does it do?
tripsinogen
- activates chemotrypsinogin and procarboxypeptidase
What do trypsin, chymotrypsin, and carbozypeptidase do?
breaks down polypeptides and peptide fragments
When is inactive proteases active?
-inactive in pancrease
- active in small intestin
Where do the trypsons move to after doing their thing?
- not into blood
- brush border enzymes still have to make it absorbable
What are the types of colon?
- ascending
- transverse
- descending
- sigmoidal
- tenae coli
- cecum
Whaere does the sigmoidal colon lead?
- leads to the rectum and anus
- contains haustra
What is the rectum?
- muscular tube that expands and stores feces and has transeverse folds called rectal valves
What is the function of the large intestine?
- absorb water
- little bacterial farm different to everyone that helps breakdown materials to form feces and vitamins b and k
What are the steps in feces formation and regulation?
- as we fill the rectum it stretches stimulating baroreceptors
- sensory info is sent to spinal cord
- nerve signals along parasympathetic axons increaed to internal sphincter
- increased pressure on internal sphincter causes it to open
- external anal sphincter is voluntary and stays contracted until we say
What is the resting state of the internal and external anal sphincters?
contracted and closed
What is a lactile?
-lymphatic capillary within the small intestine
What is the surface of the small intestine like?
- highly folded with villi containing supramucidial cells surrounded by capillaries
What do intestinal cells produce?
- brush border cells
What do emicellular cells do?
- make enteropeptidase which takes trysinogen and activates it into tryposin
What do enteroendocrine cells do?
-release cck and secretin
What are the water soluble vitamines?
- B and C
- not stored in body and need to be replenidshed
What are the fat soluble vitamins?
- ADEK
- absorbed in small intestine and stored in liver
