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 cross-bridge).

• 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

Digestive system• Steps:

– 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. HCl lowers pH to 1.6-2.4, this activates pepsinogen to make pepsin. Pepsin is protease: breaks proteins into small polypeptides.

Digestive system• Low pH 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 pH• Pancreatic enzymes work best at ____________ pH

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

Digestive system• Duodenum:

– 1) Fatty chyme stimulates cholecystokinin production– Stimulates gallbladder contraction and pancreatic juice

secretion

Digestive system• Duodenum:

– 2) Acidity in chyme stimulates ______________ production– Secretin stimulates pancreas to release bicarbonate

Digestive system• Duodenum:

– 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