Muscular system Skin burns First degree epidermis second

Muscular system

Skin burns • First degree (epidermis), second degree (epidermis and dermis), third degree (dermis)

Muscular system • Brief review of 3 types of muscle tissue • 1) Smooth muscle (walls of vessels or tubules in digestive, circulatory, excretory, reproductive, respiratory systems) – Spindle shaped – 1 nucleus per cell – Involuntary (no conscious control) – Can make prolonged contractions

Muscular system • Brief review of 3 types of muscle tissue • 2) Skeletal muscle – multinucleate – transverse striations – powerful, quick contractions – voluntary

Muscular system • Brief review of 3 types of muscle tissue • 3) Cardiac muscle – 1 nucleus per cell – Transverse striations – Intercalated discs present (increase conduction of impulses) – Fast-acting – Involuntary

Levels of Organization • Muscle: entire unit. Usually surrounded by connective tissue sheath • Fascicle: bundle of muscle cells. Also surrounded by connective tissue sheath • Fibers: muscle cells

Levels of Organization • Myofibrils: elongate structure. ______ in each muscle cell. Contain elongate proteins called myofilaments • Myofilaments – thick filaments (of myosin) – thin filaments (of actin)

Levels of Organization • Myofilaments – thick filaments (of myosin protein) – thin filaments (of actin protein)

How muscles contract • Sarcomere structure – Z line: Very dark thin line at edges of sarcomere. Is place where thin filaments attach to each other (backbone from which they project) – A band: represents thick fibers (dark color) I

How muscles contract • Sarcomere structure – H band: Light area in middle of A band – I band: area between A bands (thin filaments only so light color) I

How muscles contract • Thin filaments slide deeper into thick filaments

How muscles contract – When muscle contracts, sarcomere shortens to _____ of its original size. – Z lines move closer together (H band gets smaller or disappears entirely). I band decreases. A band stays same.

How muscles contract • Why do filaments slide? • Myosin heads attach to form cross-bridges, bend, release (power stroke). Called cross-bridge cycle.

How muscles contract • Repeat of cross-bridge cycle slides thin filaments between thick filaments • 50 -100 cycles per second!

How muscles contract • Why? Action of ATP/ADP. With ADP, myosin head attaches to thin filament (forms crossbridge). • Once attached, head bends and releases ADP

How muscles contract • Binding with ATP again causes detachment • Breaking ATP into ADP bends head ____ (head cocked) • Head ready to attach again

How muscles contract • How control this? Role of Ca++

How muscles contract • Relaxed muscle: heads cocked but can’t bind • Blocked by tropomyosin (protein)

How muscles contract • Binding sites exposed by action of troponin (protein) • Ca++ binds to troponin, causing tropomyosin to expose binding sites

How muscles contract • So, control _______ and you control muscle

How muscles contract • Ca++ stored in sarcoplasmic reticulum • Nerve impulse arrives at muscle fiber, causes release of Ca++ and thus contraction

How muscles contract • When impulse stops, Ca++ transported back into sarcoplasmic reticulum and contraction stops

How muscles contract • So, supply of Ca++ used to control contraction of muscle cells. • Note: mitochondria supply ATP needed for cross-bridge cycles

Motor units • Each fiber either contracts or not • How control power of contraction?

Motor units • Size of motor unit. Motor unit: set of fibers that respond to one motor neuron. All fibers contacted by one ____ and its branches.

Motor units • Fine control: small motor units (ex, muscles that move eyes) • Not so fine control: large motor units (ex, hamstring muscle) • Weak contraction of muscle uses few motor units. Stronger contraction uses more motor units.

Muscle fiber types • A contraction/relaxation cycle is a twitch

Muscle fiber types • Slow-twitch fibers: take long time to reach maximum contraction. Do aerobic respiration well: have good blood supply, have ______ pigment that helps use oxygen efficiently • Turkey: dark meat

Muscle fiber types • Fast-twitch fibers: take short time to reach maximum contraction. Do anaerobic respiration well. Rapid generation of power: grow thicker and stronger with use (“Arnold” effect) • Turkey: white meat

Muscle fiber types • Slow-twitch fibers • Fast-twitch fibers • Note also Intermediate fibers: combine traits of other 2

Skeletal Muscles • Make body parts move • Most in antagonistic pairs

Skeletal Muscles • Make body parts move • Most in antagonistic pairs – Abductors: move part away from body – Adductors: move part toward body

Skeletal Muscles • Make body parts move • Most in antagonistic pairs – Flexors: decrease angle between bones – Extensors: increase angle between bones

Skeletal Muscles • Make body parts move • Most in antagonistic pairs – Depressors: lower body part – Elevators: raise body part

Skeletal Muscles • Other muscle features: – Origin: Stationary bone to which one end of muscle is attached – Insertion: Moveable bone to which other end of muscle is attached – Action: description of what muscle ____

Skeletal Muscles • Lab: learn some major muscles

Cardiac Muscle • Intercalated discs connect cells • Striations present

Cardiac Muscle • Electric impulses spread directly from cell to cell through discs. Connected cells form a myocardium (2 in the heart) • Impulses created by group of _____ called pacemaker • Each myocardium contracts as unit.

Smooth Muscle • No sarcomeres (striations) • Thick and thin filaments present and extend across cell

Smooth Muscle • No sarcoplasmic reticulum, Ca++ enters cell from extracellular fluid to cause contraction • Ca++ entry can be stimulated by nerve action or spontaneously by ____ cell itself • Impulse spread to other smooth muscle cells through cellular connections

Digestive system

Digestive system • Processes: – 1) Ingestion: take food into mouth – 2) Digestion: mechanically and chemically break down food, absorb products – 3) Egestion: get rid of undigested food (feces). NOT same as excretion (rid body of nitrogenous wastes).

Digestive system • In animals: • 1) Intracellular digestion: food breakdown occurs in vacuoles of cells (sponges) • 2) Extracellular digestion: food breakdown occurs in cavity in body into which enzymes secreted

Digestive system • Extracellular digestion: – Incomplete digestive system. No specialization can occur. All cells take part similarly

Digestive system • Extracellular digestion: – Complete digestive system. One-way flow of food. Specialization can occur along way. Increases efficiency.

Digestive system • Here emphasize human system • Primary organs – mouth – pharynx (crossroads to trachea and lungs, or esophagus and stomach) – esophagus – stomach – small intestine – large intestine (colon) – rectum – anus

Digestive system • Much of tube has layered structure – mucosa: epithelium – submucosa: connective tissue – muscularis: smooth muscle layers – serosa: _______ tissue

Digestive system • Secondary organs or tissues – teeth – tongue – salivary glands – liver – gall bladder – pancreas

Digestive system • Now, follow a bite of food through the digestive system

Digestive system • Mouth (oral cavity) • Chewing occurs. Note this special for mammals. Most other vertebrates swallow food whole or in chunks (other parts of digestive system can break up food: example, gizzard)

Digestive system • • Teeth (heterodont): differ depending on function Incisors and canines: shearing teeth (carnivores) Premolars and molars: grinding teeth (herbivores) Humans omnivores (eat both meat and plant material): front for carnivory, back for herbivory

Digestive system • Teeth: Living structures – Enamel: hard coating on exposed portion – Dentin: softer underlying material – Pulp: contains nerves and blood vessels – Root: Extends into bone socket, held to bone by ligaments and cementum layer

Digestive system • Mouth (oral cavity) • Tongue: muscular organ. Mixes food with saliva to form ____ (food lump) • Food moistened with saliva from salivary glands

Digestive system • 3 pairs of salivary glands (parotid, submandibular, sublingual) • Saliva contains: – water and ions – ____ (lubrication) – amylase: hydrolyzes starch (polysaccharide) to maltose (double sugar)

Digestive system • Emptying the mouth (swallowing): food delivered to esophagus • Complex action! • Players: – – – – Hard palate Soft palate Tongue Epiglottis Glottis Larynx (voicebox) Esophagus

• Steps: Digestive system – 1) tongue moves food to back – 2) soft palate lifts to close nasal cavity – 3) larynx raises to push glottis against epiglottis – 4) tongue and throat muscles squeeze food into esophagus

Digestive system • • Esophagus: Muscular tube that conducts food to stomach Waves of contractions (peristalsis) push food downward Secretes mucus to smooth passage Does not make digestive ________

Digestive system • Stomach: Muscular bag.

Digestive system • Stomach: Muscular bag. • Top has cardiac sphincter. Keeps contents from coming back up • Bottom has pyloric sphincter. Controls passage into small intestine

Digestive system • When food enters, sphincters close. Stomach secretions begin along with muscular churning movements. Forms acidic mush called _____. • Stomach wall invaginated to increase surface area. • Mucosa has gastric pits, which contain gastric glands

Digestive system • Stomach digestion: – 1) Mechanical breakdown: churning/mixing – 2) Chemical breakdown: _____ cells make pepsinogen. Parietal cells make HCl lowers p. H to 1. 6 -2. 4, this activates pepsinogen to make pepsin. Pepsin is protease: breaks proteins into small polypeptides.

Digestive system • Low p. H kills most bacteria/fungi • Other secretions: gastric lipase (breaks down lipids), mucus (helps protect lining from acid), water

Digestive system • Little absorption in stomach (except _____, alcohol, fast-acting drugs) • Once food converted to chyme, pyloric sphincter meters out contents a little at a time into small intestine

Digestive system • Small intestine and its 3 regions: – duodenum (10 inches) – jejunum (8 feet) – ileum (12 feet)

Digestive system Inner wall folded Folds of mucosa covered with projections (villi) Epithelial cells of villi with membrane folds: microvilli Together these produce enormous surface area (300 square meters) • Many times skin surface! • •

Digestive system • Main functions of small intestine: • Digestion: Most occurs here. Accessory organs provide important _______ • 1) Pancreas. Very important organ. • Produces digestive enzymes and delivers them through pancreatic duct (exocrine gland). Produces 2 liters of pancreatic fluid/day!

Digestive system • Pancreatic enzymes: – 1) proteases (trypsin and chymotripsin) – 2) lipases (pancreatic lipase) – 3) nucleases (DNase: breaks DNA into nucleotides. RNase: breaks RNA into nucleotides) – 4) carbohydrases (pancreatic amylase) • Note: enzymes of pancreas can digest all 4 major macromolecules (proteins, lipids, nucleic acids, carbohydrates)

Digestive system • Pancreas also produces bicarbonate (alkaline substance) • Neutralizes stomach acid and gives chyme slightly alkaline p. H • Pancreatic enzymes work best at ______ p. H

Digestive system • 1) Pancreas. Very important organ. • Also is endocrine gland. Makes several hormones (including insulin and glucagon) in Islets of Langerhans. These regulate blood sugar level. • Less insulin, more glucagon leads to breakdown of glycogen & fat

Digestive system • 2) Gall bladder and liver. • Liver is ______ internal body organ. Many functions: including detoxification center, production of blood plasma proteins, etc.

Digestive system • • 2) Gall bladder and liver. Also makes bile, stored in gallbladder Bile: A) bile pigments: waste from liver destroying old red blood cells • B) bile salts: emulsify fats. Break _____ into smaller droplets so they can be digested by enzymes

Digestive system • Still more enzymes embedded in membranes of small intestine cells (brush border enzymes)

Digestive system • Brush border enzymes: – 1) Peptidase: breaks peptides into amino acids – 2) Nucleases: Break DNA/RNA into sugars and nucleic acid bases – 3) Carbohydrases: Sucrase (sucrose into glucose and fructose), Maltase (maltose into 2 glucose), Lactase (lactose into glucose and galactose) • People who are lactose intolerant don’t have functional lactase (can occur with age)

Digestive system • Main functions of small intestine: • Digestion (discussed) • Absorption (90% occurs here), rest in stomach and large intestine

Digestive system • Absorption: • Water, amino acids, monosaccharides: taken up by epithelium and transferred to blood capillaries • From there, hepatic portal vein delivers to _____

Digestive system • Fatty acid absorption: – absorbed and reassembled into _____ inside epithelium cells – coated with protein to form chylomicron – these taken into lymph capillaries and enter lymph system (empties into blood veins near neck)

Digestive system • Jejunum and ileum of small intestine complete processes begun in duodenum • Last point: lots of fluid moves through small intestine. About 9 liters a day. But 8. 5 liters reabsorbed there.

Digestive system • Large intestine (large diameter, 5 feet long). • Begins at ileocecal valve. Ends in anus • Caecum: pouch at start. No current function. Grazing animals have expanded ______ • Appendix: no current function

Digestive system • Other parts: Ascending colon, transverse colon, descending colon, rectum, anus.

Digestive system • Large intestine: No digestion occurs. Water absorbed, some vitamins and ions absorbed. Main function is to compact and store wastes • Note lots bacteria live here. Bad: can make _____. Good: synthesize Vitamin K.

Digestive system • Rectum at end: final storage of compacted wastes • Two sphincters: first of smooth muscle and opens involuntarily, second of skeletal muscle and is voluntarily controlled.

Digestive system • Looking back on the journey. . . Digestive enzymes

Digestive system • Digestive coordination • Nervous system and endocrine system

Digestive system • Stomach: – 1) Proteins in stomach stimulate secretion of ______ – 2) Gastrin stimulates HCl and pepsinogen production by stomach

• Duodenum: Digestive system – 1) Fatty chyme stimulates cholecystokinin production – Stimulates gallbladder contraction and pancreatic juice secretion

• Duodenum: Digestive system – 2) Acidity in chyme stimulates _______ production – Secretin stimulates pancreas to release bicarbonate

• Duodenum: Digestive system – 3) Presence of chyme stimulates gastric inhibitory hormone – Prevents stomach from releasing more chyme until current batch moves on

Digestive system • Specialized vertebrate guts (herbivores) – Stomach chambers: ruminants have large chamber (rumen) that acts as fermentation vat for bacteria/protists to digest cellulose – Rumination: chewing cud (contents of rumen). Exposes more _____ area of plant cells

Digestive system • Specialized vertebrate guts (herbivores) – Enlarged caecum: nonruminant herbivores use caecum as fermentation vat. Some (rabbits) produce two kinds of feces: soft ones are reingested. This called ________. Hard ones not.

Digestive system • Carnivores and omnivores with shorter, unspecialized guts