Week10.pdf EXSC 223 001
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This 0 page Class Notes was uploaded by Chase Heffron on Friday November 6, 2015. The Class Notes belongs to EXSC 223 001 at University of South Carolina taught by Thompson in Summer 2015. Since its upload, it has received 59 views. For similar materials see Anatomy and Physiology 1 in Physical Education at University of South Carolina.
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Date Created: 11/06/15
Week 10 The Twitch a muscle twitch is when you give a muscle a single stimulus causing a contraction Twitches take a lot longer to occur 120 milliseconds about There are 3 phases the latent period period between stimuli and when tension occurs During the latent period the action potential moves across the sarcolemma and down the Ttubule causing the release of Ca This period is very brief 12 milliseconds The period of contraction is when tension occurs Calcium is being released into the cell and many cross bridges are formed More tension is being developed The relaxation period is when calcium is pumped out of the cell and the muscle relaxes Different skeletal muscles have different rates at which they develop tension and relax Some muscles develop tension rapidly fast twitch Some muscles are slower slow twitch Eye muscles are constantly twitching very rapidly They are extremely fast because they contain a speci c contractile protein This twitch is much faster than even fast twitch muscles The oastrocnemius is the muscle that is used to push off to move forward This is a fast twitch muscle The time of tension and relaxation are about 20 Milliseconds each The soleus sits underneath the gastrocnemius The soleus muscle is a posture muscle The soleus muscle holds you in place This muscle takes about 40 milliseconds to reach peak tension and about 50 milliseconds to relax There is NO difference in the time of the latent period for all of these twitches The primary difference in the time of muscle contraction is myosin There is fast and slow myosin in muscles Fast muscles use ATP faster and are less ef cient The relaxation periods have to do with Ca pumps not myosin Fast twitch muscles have a fast rate calcium pump and slow twitch have a slower rate ca pump Dark meat is a hallmark quality of slow twitch muscle This darker redish meat of chicken contains myoglobin This is because they use their legs The white meat contains no myoglobin Graded muscle responses Stimulus frequency What happens if a second stimulus is given to a muscle while it is contracting or relaxing The force produced following the second stimulus is going to be greater than that provided by the rst This is caused by a greater amount of calcium in the cytosol which causes more cross bridges to form Each successive stimulus to a muscle will create more force than the last if the muscle is stimulated before relaxation Eventually there is a peak value of strength that can be reached This is known as tetanus This is when a maximal amount of cross bridges have formed Neural Recruitment A motor unit consists of a motor neuron and all the muscle bers that that neuron innervates Nerves can have multiple motor units Each muscle ber can be innervated by only 1 motor neuron but a motor neuron can innervate multiple bers Motor units with slow twitch muscle tend to be small Motor units with fast twitch tend to be larger How is force regulated with motor units As we activate more motor units we produce more force This causes more cross bridges to form This is controlled voluntarily If you lightly curl your ngers you are stimulated just a few motor units If you tightly curl your ngers into a st you are activating all of your motor units which produces much more force than just a few The size principle the more motor units recruited the more force produced The small and the slow motor units are recruited rst If more force needs to be produced we recruit larger and faster motor units Length tension relationship describes relationship between force and length of sarcomere Percent of resting sarcomere length ranges from 60 to 180 100 is the ideal resting length At ideal resting length we can produce maximum force At this resting length you can form the maximum number of cross bridges Increasing the length of the sarcomere about 20 to 120 your muscle can still produce maximum force But from 120 onward maximum force production decreases Less cross bridges can form This is because there is less overlap of the thick and thin laments Eventually the sarcomere can be pulled apart so far very little force at all can be produced If there is a decrease in length of the sarcomere below 100 it produces less maximal force When the sarcomere shortens youll see that you can reach a point where the thin laments from the right overlap with the thin laments from the left This provides interference to cross bridges forming Cardiac muscle specialized striated muscle has organized contractile proteins myo brils with sarcomeres Cardiac muscle has similarities and differences from skeletal Myocytes are much smaller in cardiac cells lntercalated discs are where to cardiac myocytes are connected to one another from desmosomes and gap junctions Cardiac myocytes are only found in the walls of the heart Usually only 1 to 4 nuclei in cardiac myocytes Cardiac myocytes also branch out which is unique The mechanisms of contraction are similar to skeletal muscle There39s a membrane depolarization which releases calcium and so on and so on same as skeletal muscle The difference is how you stimulate the membrane Automaticity the heart beats on its own The heart can be sped up or slowed down This is related to the autonomic nervous system The parasympathetic branch causes the heart to decrease frequency of contractions The sympathetic system speed it up The intercalated discs is where cardiac muscle cells join Desmosomes are high stress structures that hold the cells together Gap junctions allow for communication If one cell depolarizes it will tell the other to depolarize Inside the cell there are myo brils and organized contractile proteins Cardiac myocytes have a sarcoplasmic reticulum It is not as well developed But it does not contribute to all the calcium like that in skeletal muscle Remaining calcium comes from interstitial uid through calveoli 7080 of calcium come from SR Cardiac cells are aerobic Cardiac myocytes are rich in mitochondria Smooth muscle very different no striations Smooth muscle bers have no distinct sarcomeres These cells are small and mononucleated The nucleus are about center in each cell Some smooth muscles will contract as units because of gap junctions some will not Smooth muscle is controlled by the nervous system The autonomic nervous system The parasympathetic and sympathetic system In some cases the para system stimulates smooth muscle in other cases it causes it to relax The same is true with the sympathetic system When you rest the Parasympathetic system is active and heart rate is low rest and digest So here the parasympathetic stimulates the smooth muscle There is also no neuromusclularjunctions in smooth muscle Instead nerves secrete neurotransmitter into the extracellular space which are taken into the cells by a gradient Smooth muscle contraction phasic contraction then relaxation usually associated with peristalic contraction There is also Tonic these occur in places like blood vessels here smooth muscles can hold a contractile state for a long time And it doesn39t take energy to hold the state it only takes energy to change to the contracted state The sympathetic and parasympathetic nerves innervate smooth muscle One nerve can branch and innervate a region of muscle There39s no synaptic cleft On the nerve there are a series of swellings known as varicosities These are where the vesicles containing the neurotransmitters When the nerve receives the signal the transmitters are released Relaxed smooth muscle cell There is a crossing network of intermediate laments The intermediate laments are connected to each other at dense bodies Caveolae are invaginations in the sarcolemma that contain a voltage gated ca channel that allows calcium to move inside the side This is important for smooth muscle contraction The SR in smooth muscle is poorly developed so most Ca comes from the caveolae Smooth muscle contains thick and thin laments The thick laments are made up of smooth muscle speci c myosin The thin laments are made up of smooth muscle speci c actin There is no troponin and tropomyosin The thick and thin laments are organized in a spiral fashion that corresponds to the intermediate laments This organization means there is a fairly uniform light absorption unlike in skeletal muscle which has bands In smooth muscle there are 13 thin to 1 thick laments When a smooth m contracts the muscle shortens and twists The organization of thick and laments causes the cell to twist Excitation contraction couolino excitation refers to events at the membrane that allow calcium to enter the cell Coupling is the result of calcium entering the cell and stimulating contraction At the calveolae the calcium enters the cell Smooth muscle has a limited SR but it too releases calcium into the cytosol Calcium activates contraction differently ln smooth muscle calcium enters the cytosol and binds to a protein called calmodulin This switches calmodulin to an active enzyme Calmodulin breaks down ATP and then it takes the Pi and attaches it to another enzyme a kinase The Kinase once active will break down ATP to ADP and Pi and attach a phosphate to myosin The attachment of ADP to myosin determines whether it is active or inactive When activated it will go to the cocked state therefore shortening the cell In smooth muscle cross bridges are regulated differently Single unit contraction phasic mostly seen in the viscera or the gastrointestinal organs common in the esophagus down to the rectum This is a rhythmic contraction There are two layers of muscle in single unit contraction Each layer acts as a single group of cells Each layer the cells are connected by gap junctions allow the connected cells to act as one This type of smooth muscle may spontaneously contract You will also see stress relaxation response Peristalsis name given to the alternating contraction and relaxation of smooth muscle to move contents from one area to the next There are two layers of smooth muscle There is the inner layer known as the circular layer because the smooth muscular cells are oriented around the diameter All the cells in the circular layer are connected by gap junctions In the longitudinal layer the cells run length ways The longitudinal layer cells are connected by gap junctions The way peristalsis works is there is alternating contractions from the longitudinal layer and the circular layer When the longitudinal layer contracts the circular layer contracts Peristalsis is important for not only moving but promoting effective digestion and absorption of nutrients There are also multiunit contractions tonic This is the idea that each smooth muscle cell acts as its own entity Not connected to neighboring cells by gap junctions Each cell is basically independent lt receives a signal from the autonomic ns to relax or contract Multiunit you see variations in contraction You can contract a little a moderate amount or a lot You see that it is present in lungs blood vessels eye muscles that regulate dilation and erector pilli muscles The Stress Relaxation response of smooth muscle when you stretch smooth muscle it contracts If you hold it in a stretched position the smooth muscle will eventually relax and reset itself to this new resting length Your bladder is a good example The walls of the bladder contain multiunit smooth muscle As you ll the bladder the smooth muscle contracts This is when you feel you must use the restroom After a while you may not feel the urge to urinate This is because the muscles have adjusted and reset to how contracted they are This is the stressrelaxation response It can also happen in the stomach Hyperplasia refers to the division of smooth muscle cells Smooth muscle cells are mitotically capable This phenomena is unique to smooth muscle Not seen in striated muscle Myoblasts before they fuse are mitotically capable but that is not skeletal muscle This can occur in blood vessels typically occurs in blood vessels and is associated with atherosclerosis This is thought to contribute to high BP and heart disease There is also a scenario unique to females Prior to puberty the uterus is small At puberty the smooth muscle cells that make up much of the uterine wall divide and allow the uterus to grow and become about the size of a woman39s st This is due to estrogen If a woman becomes pregnant to accommodate the growing fetus the uterus grows as well The uterus also has to be able to produce enough force to push the baby through the birth canal During pregnancy the uterus gets larger the smooth muscle cells divide Chapter 23 The digestive system The digestive system is broken into two componets The Alimentary canal runs from mouth to anus Everything in that tube is technically outside of your body Only the food that is absorbed enters the body The accessory organs these aid in the process of absorption the teeth tongue gallbladder liver pancreas Most of the organs associated with the digestive system sit in the abdominopelvic cavity Pancreas is both endocrine and an exocrine organ When we put food into our mouth we are ingesting food If it is solid the process of mechanical breakdown begins Chewing or mastication is aided by teeth and tongue Churning occurs in the stomach mixing of the food with enzymes Segmentation the further mechanical breakdown of food that occurs in the small intestine Propulsion is the movement of food through the alimentary canal Propulstion includes swallowing and peristalsis Digestion is the breakdown of food by enzymes Begins in the mouth but mostly occurs in the small intestine Churning make sure food comes in contact with enzymes Most absorption of primary nutrients occurs in the small intestine Some water is absorbed in the small intestine but most water is absorbed in the large intestine A small amount of absorption occurs in the mouth Small amounts of carbohydrates can be absorbed in the mouth When we talk about absorption were talking about the transportation of the food from the lumen into the blood stream Anything that is not absorbed will be eliminated Food will be collected into the rectum When a signi cant about is in the colon you will have the urge to defecate Most of what you defecate is actually bacteria not the food you consume Some bacteria that reside in you GI tract produce vitamins such as vitamin K Bacteria form a symbiotic relationship with us that we both bene t from The organs of the digestive system mostly reside in the abdominopelvic cavity and most of these are wrapped by the serous membrane the peritoneum Like all serous membranes there is a visceral layer and a parietal membrane All serous membranes are sac The parietal side is one side of the sac the visceral is the other side The visceral side is adjacent to the organ The parietal is normally against the outside wall The peritoneum serves two important functions 1 secreted on the inside is a lubricant The digestive system gets stretched out and changes size often This constant change in size results in friction So this lubricant reduces friction and pain 2 The peritoneum isolates most of your body from the GI tract This is important because there are large amounts of bacteria in the GI tract and this physical barrier keeps the bacteria out of the body The mesentery is where you nd two regions of the peritoneal membrane essentially fused together Typically in the mesentery you nd lots of blood vessels There are regions not surround by the peritoneum In the duodenum of the small intestine there is region covered by adventitia Layers of small intestine The lumen is the name of the tube The rst lining is the mucosa Mucosa line most of the GI tract Mucosa is always a damp membrane there will be some sort of secretion keeping the columnar cells moist Associated with the mucosa is the muscularis mucosae This is a smooth muscle that causes wrinkling in the mucosa These wrinkles help increase the amount of contact between chyme and mucosa thus helping with absorption The Submucosa is where absorption takes place Nerves controlling peristalsis and the absorption of food are found here The submucosal nerve plexus important part of nervous system speci c to GI tract is found Outside the submucosa there is the muscularis externa this is where most of the smooth muscle is found This layer is what causes peristalsis The Serosa is the visceral layer of the peritoneum IF there is no serosa found instead adventitia is found The gastrointestinal tract has its own nerve supply The enteric nervous system can operate independently from the central nervous system Normally this is call short re ex When you operate with the nervous system this is called long re ex When you ingest food you activate chemoreceptors that can activate this system Short re exes are speci cally about what39s in the system When you have food in the system that leads to contractions and other things promoting absorption Just by putting food in your mouth increases the activity in your GI tract Information from the central NS to the enteric nervous system is really from the autonomic nervous system The parasympathetic NS increases digestion and the Sympathetic system slows down digestion Mouth made of the oral cavity bordered by the Hard palate bordered by the soft palate and uvula Uvula doesn39t have any known function In the oral cavity you see non keratinized strati ed squamous epithelium The soft palate and palatoglossal arch aids in the movement of food down into the pharynx Teeth are important for mastication The tongue is an important muscle for communication and mixing food and swallowing The tongue is unique in that its skeletal muscle One region the muscle has no origin and insertion The second layer of muscle the lower layer has an origin but no insertion This is responsible for broadening the tongue The tonsils are part of the lymphatic system This system helps recover uid lost from the cardiovascular system and plays a role in aiding the function of the immune system Your tonsils are a type of lymph gland When a response is initiated to ght off infection they swell up and become tender At the back of the mouth there is the pharynx There are 3 regions There is the upper region the oropharynx and the laryngopharynx The pharynx turns into the esophagus after the last region The epiglottis prevents you from inhaling food It closes the trachea when you swallow F day Below the tongue there is the opening of the submandibular duct Teeth are important to digestive function though technically they are an accessory organ Food is masticated into smaller bits so it can be swallowed safely Also make sure food is broken down suf ciently so in the stomach more enzymes can reach more particles of the food 32 Adult teeth Different teeth serve different functions and have different surface areas Different teeth have different numbers of roots Most have a single root but some molars have two or even 3 roots Teeth consist of two parts crown visible part and the root Crown exposed region covered in enamel hardest substance in our body Made of hydroxyapatite just like bones but much more dense Cannot repair teeth because Point of Fluoride is to ll in divots created by bacteria that break down enamel We bene t enormously by uoridated water The enamel is the part of the tooth that is hard and allows us to chew Under the enamel is dentin Dentin is hard but has more exibility than enamel Dentin acts as a shock absorber The dentin is associated with the crown and the root Within the crown there is the pulp cavity This is where blood vessels are found and the nerve endings are found The pupl cavity is enlarged in the crown but extends into the root and into the bone A root canal is where part of the tooth is cut off and the pulp cavity is killed lled then an arti cial crown is put on top Root the dentin projects down into the bone The root is attached to the bone by cementummineralized connective tissue Adjacent to this is the periodontal ligament which is also mineralized CT that helps hold the tooth in place The tongue important skeletal muscle Upper layer with no orgin or insertion is the intrinsic muscle This is important in terms of mastication tongue mixes up food and makes sure food gets under teeth When you swallow part of the tongue moves the food and pushes it down Two major regions to the tongue part in the oral cavity and part in the oral pharynx The part in the oral cavity includes liform papilla increase friction These help pick up particles of food onto tongue Filiform papilla are not associated with taste buds The fungiform vallate and foliate papillae are associated with taste buds We have 5 different tastes but have thousands of cells There are also taste buds in the cheeks and the soft palate Associated with the tongue we secrete and enzyme known as a lipase enzyme that breaks down fat Limited amount of digestion take place here but it starts here Salivary glands parotid submandibular and sublingual gland The submandibular and sublingual secrete very thin and runny mucous The parotid glands are large and towards the back of the mandible secrete directly into the mouth The other 2 glands secrete in front of the tongue We are vaccinated against mumps This is cause the parotid gland would become infected Saliva cleans mouth mixes with foods to help with breakdown helps to componets of food to become free and interact with taste buds Breaks down starch with amylase Saliva is 99 h20 but contains amylase mucin runny mucous lgA antibodies or immunoglobulins protective mechanism against things we ingest enzymes like lysozymes and defensins also offer protection against things we ingest This is because we don39t consume sterile food Control of salivation done by parasympathetic NS PNS is active when you rest and digesting If you are out for a run this is Sympathetic activity which tends to inhibit these things There are also mechanical and chemical receptors that cause us to salivate Esophagus has 4 layers of tissue mucosa the submucosa CT tissue enteric nerves muscularis externa 2 layers of smooth muscle and adventitia CT tissue technically not a membrane The esophagus39s job is to take food from the oral pharynx down to the stomach No digestion just transport There are peristaltic contractions that take place here The Stomach located in the abdominal cavity so for the esophagus to connect it has to penetrate the diaphragm A sphincter is associated with the esophagus Most sphincters are circular muscles the esophageal sphincter is smooth muscle found where the esophagus attaches to the stomach This structure prevents acid from going up into the esophagus Stomach acid can destroy the lining of the esophagus so this is an important muscle The stomach is a large hollow organ There are 4 layers of tissue mucosa submucosa muscularis externa and serosa The lining of the stomach is simple columnar epithelia In the muscularis layer there are actually 3 layers of smooth muscle The stomach has 3 regions The cardia is where the esophagus opens up to the esophagus The fundus is in the superior part where the stomach extends upward The Pyloric canal is where the stomach narrows The stomach can change size tremendously like most smooth muscle When you haven39t eaten in a while you see a unique structure called The stomach is a temporary storage facility Food here mixes with acids and enzymes speci cally pepsinogen These acids break down proteins and activate pepsinogen into pepsin Both acid and pepsin combine to cause the breakdown of proteins into amino acids Not all digestion is done here but the majority of protein breakdown occurs here High carb meal moves through the stomach faster High protein and fat foods remain in stomach longer As food mix with acids and other secretions we form something called chyme It is chyme that is released into the small intestine Chyme is really acidic The autonomic nervous system plays an important role The PNS stimulates digestion the SNS inhibits digestion Blood supply of the GI system is known as the splanchnic This is responsible for sending blood to GI system then to the liver from the GI system In the process of mixing and forming chyme the stomach has 3 layers of smooth muscle There is the circular longitudinal and oblique muscle diagonal to the other 2 This allows effective mixing of the food and also aids in the movement of the food towards the valve When the stomach empties contents into the small intestine it does so in small amounts This is because the contents of the chyme are so acidic it would overwhelm the small intestines ability to neutralize the chyme The mucosa of the stomach is made of columnar epithelia which is almost exclusively goblet cells These mucous secretion are combined with bicarbonate The bicarbonate is there to prevent the acid from destroying the goblet cells If Goblet cells get destroyed they are replaced very quickly The acid resistance mucous and bicarbonate keep the stomach from digesting itself The bicarbonate only neutralizes the acid locally The gastric pits are where glands are found that make secretions for the stomach There are parietal cells gastric glands mucous cells and chief cells It is the parietal cells that are responsible for producing the acid The mucous cells prevent acid from degrading the cells within the gastric pits The intrinsic factor is produced by The intrinsic factor is necessary for the absorbtion of Vitamin B12VBlZ is necessary for the absorption of iron Chief cells produce pepsinogen Pepsinogen is a protein that is an inactive enzyme When pepsinogen is exposed to a low ph environment it breaks down into its active form Then it will be ready to enzymatically break down proteins The enteroendocrine cells don39t secrete into the stomach They secrete into the interstitial space Histamine and gastrin and serotonin are secreted by these Food much travel through the pyloric sphincter to get into the small intestine Chyme must be neutralized shortly after entering the SI This is down in the rst region of the small intestine the duodenum