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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)
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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
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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)
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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)
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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
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mucosa: epithelium
submucosa: connective tissue
muscularis: smooth muscle layers
serosa: ______________ tissue
Digestive system
• Secondary organs or tissues
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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
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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:
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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
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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!
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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
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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