Unit 12, Animal form and function

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Unit 12, Animal form and function   Chapter 47,
p. 924 I. The sliding filament mechanism of
muscle contraction A. Structure of a muscle fiber
as with contraction arranged in levels of
structure or organization. 
From large to small muscle, fascicle, fiber (1
cell) myofibrils, myofilaments.  1. Muscle fibers
are stripped because myofibrils are stripped
(i.e. striated)
 2. The repeating unit is a sarcomere, fig. 47.8,
47.9, p. 925, and contains the following
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a. The repeating unit is from z line to z line
(i.e. the sarcomere)
b. Myosin thick filament A band (dark)
c. Actin thin filament I band (light)
d. H band is created when muscle is relaxed and
is area where myosin is present but not actin.
During muscle contraction H band is lost.
B. The physiology of muscle contraction sliding
filament hypothesis. 1. Myofibrils (NOT
myofilaments) contract and shorten
2. Thin filaments (actin) move toward the center
overlapping myosin (i.e. toward A)
3. H zone in center disappears
4. I bands of actin (light when not overlapping
because more of the actin overlaps the myosin
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C. Mechanisms of sliding filaments how does it
happen? 1. Structure of the filaments a. Thick
filament is actually many myosin proteins wound
together. Each myosin proteins has a thickened
region on an end called the head.
 b. Thin filaments are actin protein molecules
twisted into a double helix
c. The myosin heads form cross bridges to actin
and pull the fibers across.
2. Mechanism of cross-bridge pulling (p.
47.13) a. ADP Pi are bound to myosin. Myosin
is in a conformation (shape) that allows it to
bind to actin, forming a cross-bridge.
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http//www.sci.sdsu.edu/movies/actin_myosin.html
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b. Bridge formation changes shape of myosin (it
bends) releasing ADP Pi
c. ATP binds to myosin head. ATP breakdown
allows myosin head to release from actin
d. myosin is now in original condition (with ATP
Pi) and the process repeats
D. Calcium concentrations in striated muscle
regulate contraction (fine tuning) 1. When myosin
heads are cocked and ready to form cross-bridges,
tropomyosin proteins block binding sites on actin
at low calcium concentrations, the muscle is
relaxed
2. At higher calcium concentrations calcium binds
to another protein, troponin, which causes a
conformational change in tropomyosin, allowing
myosin heads to bind to actin and cause muscle
contraction.
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3. Calcium is stored in muscle fibers in muscle
fibers in sarcoplasmic reticulum (SR), a modified
endoplasmic reticulum. Muscle contracts causing
SR to release calcium into myofibril)
4. Muscle contraction is regulated by nerves
E. Nerves stimulate muscles to contract 1. Nerve
cells found on skeletal muscle are called somatic
motor neurons
2. Axons of somatic motor neurons make synapses
(intercellular junctions or gaps, in this case
neuromuscular junctions) with many fibers.
3. The mechanism a. Somatic motor neuron (one
nerve cell) is stimulated
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b. Release of neurotransmitter acetylcholine
(Ach) into the synapse
c. Muscle fiber is stimulated, impulse spreads
through fibers and transverse tubules (t-tubules)
d. T-tubules send impulse to SR
e. SR releases calcium which binds to troponin
4. Other considerations a. Motor unit (fig.
47.16, p. 929) the set of muscle fibers in
contact with (innervated by) all axonal branches
of a given motor neuron.
b. recruitment The numbers and sizes of motor
units vary and variation allows for gradations in
motor movement (needed for coordination)
1. Muscles that need a fine degree of control
have few muscle fibers per neuron (smaller motor
units)
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2. Muscles that need power and force (vs.
precision) require large numbers of muscle fibers
per neuron (lager motor units), e.g. large
muscles of the leg
3. Selective activation most muscles contain a
variety of motor unit sizes. Weak contractions
activation of a few small motor units, Strong
contractions additional motor units are
activated.
II. Other muscle considerations A. Types of
muscle fibers 1. Type I fibers slow
twitch example soleus muscle in leg, sustained
contraction, low fatigue, high number of
capillaries, respiratory enzymes, myoglobin,
mitochondria. Myoglobin is red, hence called red
fibers
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2. Type II fibers fast twitch example eye
muscle, rapid power, weight training, high fiber
thickness, low number of capillaries,
mitochondria and myoglobin, hence white fibers.
3. Intermediate muscle fibers example calf
muscle (gastronemius), somewhat in between fast
and slow twitch. Endurance training will
increase number of these muscle fibers.
B. Muscle metabolism 1. Skeletal muscles at
rest obtain energy mainly from aerobic respiration
2. During exercise, anaerobic respiration occurs
for 45-90 seconds, then glycogen and blodd
glucose are used
3. If exercise is moderate, aerobic respiration
will operate after first 2 minutes
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4. Intensity of exercise level varies with
individuals capacity for oxygen uptake (aerobic
capacity or VO2 max), e.g. Lance Armstrong
5. Muscle fatigue decrease in muscles ability
to generate force, directly related to high
lactic acid formation
6. Weight training increases cell size (not
number of cells), called hypertrophy
7. Oxygen used in exercise must be repaid (oxygen
debt). This is the reason why you continue to
breathe heavily after exercise.
C. Other types of muscle (besides striated,
skeletal muscle) 1. Cardiac muscle makes up
heart. These cell interconnect and link (at
structures called intercalated discs) creating a
single, functional unit, the myocardium.
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2. Smooth muscle no striations, surround
vessels and organs. Many are under involuntary,
neural control
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Chapter 48, p. 935 I. Vertebrate Digestive
systems A. Overall, comprised of the alimentary
canal (system of tubes) and the solid organs
B. Histology of the alimentary canal (tubular
gastrointestinal tract) from inside to outside,
fig. 48.5, p. 937
1. Innermost layer mucosa lines the lumen
(opening). Functions vary with location. Ex
esophagus lubrication small intestine -
absorption
 2. Next layer submucosa contains blood and
lymph vessels
3. Next layer muscalaris contains external
muscles for support (circular, longitudinal,
oblique-stomach only)
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4. Outermost layer serosa (aka peritoneum) a
thin layer of connective tissue surrounding the
abdominal cavity.
II. The pathway of digestion A. The mouth 1.
The oral cavity is guarded by the teeth
(incisors, canines, premolars, molars, all
specializations of omnivore teeth
 2. Digestion begins in the mouth with 2 types of
breakdown
a. Mechanical teeth breakdown the food forming
a ball (bolus) of food
b. Chemical saliva and enzymes secreted from
salivary glands. Polysaccharides broken down
into disaccharides by salivary amylase
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B. From mouth, food goes to pharynx, esophagus 1.
The epiglottis blocks the trachea
2. Food moves through the alimentary canal by
peristalsis contraction of smooth muscle.
C. Food enters the stomach (review structure,
fig. 48.11, p. 940) 1. Function breakdown (AKA
digestion, AKA hydrolysis)
2. Main activity is partial breakdown of protein
 3. Gastric pits of mucosal cell layer contain
gastric glands that secrete a. parietal cells
secrete HCL
b. chief cells secrete pepsinogen (See notes)
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4. Stomach pH is about 2 due to secretions of HCL
excess secretion can cause ulcers (usually
duodenal)
5. Solid food is converted to a semi-liquid
called chyme
6. Some water, aspirin and/or alcohol in chyme is
absorbed in stomach, the rest goes through
pyloric sphincter (aka pyloric valve) where
terminal digestion of carbs, lipids, proteins
occur and digestion products (monomers of these
molecules) are absorbed.
D. The small intestine has 2 main functions,
terminal digestion and absorption 1. Structure of
(3 sections) a. duodenum (30 cm)
b. jejunum (3 m) c. ileum (4 m)
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2. Accessory (solid) organs produce HC03-
(bicarbonate ions) which neutralizes acid as
chime enters the duodenum and jejunum (pH goes
from 2-3 to about 7.8 in small intestines
a. pancreas secretes digestive enzymes
b.liver secretes bile which stimulates gall
bladder to secrete bile. Bile emulsifies (break
down)
c. These organs secrete into ducts that empty
into the duodenum
3. Absorption a. In small intestine, epithelial
cells of the mucosa contain microvilli small
cytoplasmic finger-like projections
1. Each villi is directly over both a capillary
and a lacteal of the lymph system
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2. Brush border enzymes are in plasma membranes
of the epithelial cells and break down nucleic
acids and sugars
b. Two pathways of absorption in small intestine
(big. 48.16, p. 941), see notes
E. The large intestine (colon) 1. Main function
concentration of waste, reabsorption of water,
ions, vitamin K
2. water relations determines the regularity
(i.e. constipation, diarrhea, etc)
3. The cecum and appendix are vestigial
structures
4. Three main portions ascending, transverse,
descending (rectum)
5. E coli in large intestine consume undigested
food and secrete amino acids and vitamin K for
absorption.
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6. Fecal matter (feces) dead bacteria,
undigested food, plant fibers, cell debris (odor
bacterial break down products and gases
methane, hydrogen sulfide, etc
7. Movement by peristalsis regulated by anal
sphincter
III. Accessory (solid) organs of the digestive
system, see fig. 48.20, p. 948 A. Pancreas 1.
exocrine organ secretes enzymatic fluid into
duodenum through pancreatic duct
2. Endocrine gland islets of langerhans. Cells
in this region secrete important hormones
a. alpha cells secrete glucagons
b. beta cells secrete insulin
c. together these regulate blood glucose
levels KNOW fig. 48.21, p. 949
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B. Liver and Gall Bladder 1. Secretions
(exocrine) bile pigments and salts
2. Liver produces bile, gall bladder stores it.
Fatty foods in duodenum triggers secretion of bile
3. Function of liver bile production, storage
and/or break-down of glycogen, synthesis of
glucose (gloconeogenesis), production of blood
plasma proteins, destruction of RBCs,
detoxification of drugs and alcohol, regulates
lipid metabolism, involved in lactic acid
metabolism 
IV. Neural and hormonal regulation of digestion,
see table 48.2, p. 950, 48.22, p. 951 A. Sight or
smell of food triggers impulse to brain which
stimulates stomach which releases the hormone
gastrin which triggers release of HCL and
pepsinogen
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B. Chyme in duodenum inhibits further addition of
chyme via an enterogasterone hormone. CCK
(cholecystokinin) hormone is secreted in response
to fat. Stimulates addition of bile to duodenum
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Chapter 49, Circulation I. Types of circulatory
systems, fig. 49.2, p. 958 A. Open Circulatory
system circulating fluids (blood) and
extracellular fluid body tissues (aka
interstitial fluid aka lymph) are mixed and
collectively called hemolymph. Ex. Mollusks,
arthropods
B. Closed circulatory systems blood is enclosed
within vessels and circulated by a pump, the
heart. Ex. Annelida through chordates
C. Vertebrate circulatory systems 1.
Transportation of molecules needed in metabolism
including hormones
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2. Temperature a. countercurrent heat exchange
cold, incoming blood from surface areas (skin) is
warmed by warm blood from torso because arteries
and veins are right next to each other.
b. constriction of vessels (vasoconstriction)
low blood flow, low heat loss. Dilation of
vessels (vasodilation) high blood flow, high
heat loss
D. Other 1. An artery leaves the heart 2. A vein
goes to the heart
II. Vessels see fig. 49.7, p. 962 A. Arteries
transport 1. Tough and 3 layers thick to
withstand blood pressure
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2. Layers a. Inner endothelium
b. Middle smooth muscle dilates or contracts to
accommodate pressure
c. outer connective tissue (collagen) for
support and elasticity
B. Veins transport 1. Contains some tissue
layers as arteries do, but not as thick
2. Thin walls and large lumen (vessel openings)
cause a low resistance to blood flow so can move
more easily to heart.
3. Valves in veins prevent backflow and fight
gravity
 C. Capillaries exchange 1. Made of endothelial
cells, only 1 cell layer thick
2. Extensive branching causes low speed of blood
flow for more efficient exchange
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3. Small vessel diameter gives means a high
resistance to flow
4. No cell in the body is further than 100
micrometers from a capillary bed
5. Exchange across the capillaries 3 methods
a. across cell membrane of endothelial cells
b. endocytosis/exocytosis
c. pores and clefts (between cells except in
NS) allow water and ions to cross exchange is
based on differences in the concentration
gradients of osmotic pressure (due to osmotic
concentration) and hydrostatic pressure (pressure
of fluid in vessel).
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III. The lymphatic system A. Functions drainage
of extracellular (interstitial) fluid, part of
immune system, absorption of fat from intestines
B. Pathways Fluid in extracellular spaces goes
to lymph pores (lacteals), goes through lymph
system to heart, lymph collects in thoracic duct
and is returned to bloodstream via superior vena
cava (in neck)
 C. Transport (circulation of fluids) in
lymphatic system is aided by body (skeletal)
muscle contraction and smooth muscle contraction
in vessels
IV. Evolution of heart vertebrates. Review
phylum chart and Fig. 49.12-49.14, p. 965-967
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V. The cardiac cycle A. the heart is a muscle 1.
arteries leave the heart
2. veins go to the heart review major
arteries, veins, structures, p. 49.15, p. 968
B. Cardiac Output CO (volume of blood moved per
contraction) since the heart is a muscle, the
better condition you are in, the better the CO
(the muscle stretches)
C. Blood flow Both atria fill simultaneously,
both atria contract, both ventricles fill, both
ventricles contract
D. Regulation of heart beat 1. The heart beat is
a rhythmic contraction within the heart itself.
The impulse to contract is located in nodal
tissue (nodal a mass of tissue)
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2. Pathway of conduction of the heart beat a.
pacemaker sino-atrial (SA) node. Bundle of
tissue in wall of right atrium
b. Atrio-ventricular node (AV node) a bundle of
tissue between the right atrium and right
ventricle
c. Bundle of his and Purkinje fibers (see fig.
49.16, p. 969) Conducting nerve fibers that go
from AV node around both ventricles
d. Conduction see notes
3. Heart sounds -lub atrial ventricle valves
closing
-dub valves between ventricles and arteries
closing
-pfff or hissing bad or leaky valves
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E. Factors that affect blood flow and blood
pressure 1. Arterial blood pressure is determined
by total volume of blood being pumped (CO) and
resistance to blood flow
2. Blood pressure measured as   systolic
pressure (ventricular contraction) 120 mm
Hg average pressure diastolic pressure
(atrial filling) 80 mm Hg
3. Baroreceptors receptor cells in carotid
arteries (neck) and in arch of aorta that detect
changes in arterial pressure. Cell receptors
trigger sensory neurons that trigger control
centers in medulla oblongata. Helps maintain
homeostasis because nerve cells trigger
vasoconstriction of vessels which increase blood
pressure
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4. Blood volume regulation is affected by 4 major
hormones a. ADH (antidiuretic hormone, aka
vasopressin). Thirst stimulates release of ADH
from posterior pituitary. ADH causes kidneys to
keep more water in blood, less excreted, raises
blood volume
b. Aldosterone kidneys experience decreased
blood flow and release angiotensin II causing
vasoconstriction. This in turn causes
stimulation of adrenal cortex, releasing
aldosterone. Net result high sodium and water
retention in blood
c. Atrial Natrioretic hormone opposite action
of aldosterone. High blood volume stretches
right atrium which release atrial natriuretic
hormone. Action low sodium, water in blood
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d. Nitric oxide (NO) a gas that causes smooth
muscle to relax, vessels dilate, blood flow
increases. Can help regulate blood flow. This
is the reason nitroglycerin works with heart
patients. Discovered in 1998 (Nobel prize in
medicine)
Blood clotting a cascade of reactions where one
reaction is dependent on the previous one
occurring i.e. see notes
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Chapter 50 I. Respiration the diffusion of
gases A. Refers to exhange of gases with the
enviroment (not cell respiration)
B. Review various types of respiration systems,
see fig. 50.2, with an eye toward evolution
C. Ficks Law diffusion rates across membranes
vary with surface area, concentration differences
(gradients) and distance, see equation, p. 974
D. Barometric pressure (pressure of all gases in
atmosphere at sea level, or atmospheric pressure
760 mm Hg. The partial pressure of individual
gases in enviroment are
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II. Respiration by gills A. Gills are between
mouth and operulum or flap. Opening the mouth
forces out water into cavity, closing mouth
forces water over gills.
B. Blood in gills flows in opposite direction to
flow of water, i.e. countercurrent exchange.
This steeply increase (and maintains) a high to
low concentration gradient, so oxygen will
diffuse into blood.

• III. Respiration by Lungs
• Gills were probably replaced by lungs for 2
  reasons
• 1. The complex structure of the gills could not
  be supported by air (requires water to buoy it up)

2. The large surface area of gills would cause
rapid decline in water from gills to air
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B. Other than insects, who have air pumped into
them by trachea, most terrestrial animals use
lungs as ventilators.
1. Amphibians have low surface area and
positive presuure breathing. Supplement oxygen
uptake with diffusion across skin (cutaneous)
2. All other terrestrial vertebrates have
negative pressure breathing (higher pressure
outside body, gases want to come in

• C. Respiration in Mammals and Birds
• No gas exchange across skin
• 2. Mammals, see notes

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3. Birds have most efficient respiration.
Cross-current flow of air and blood plus
unidirectional air flow as a result of air sacs
allows this to happen.

• IV. Structure and mechanics of breathing
• Mechanical Control
• 1. Breath, inhalation or inspiration, causes
  intercostals and diaphragm to expand increasing
  the volume in the thoracic or chest cavity.
  Pressure is higher outside (negative pressure) so
  air rushes in.

2. Relaxation of muscles and diaphragm
exhalation
B. Chemical control see notes
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V. Blood chemistry of respiration. A. Oxygen is
carried in the blood by the tetrameric (4 chain)
protein hemoglobin (Hb)
1. Hb 4 O2 ? oxyhemoglobin
2. Binding oxygen to Hb involves an allosteric
effect (AKA conformational change in Hb protien
aka cooperativity, e.g.
a. The first oxygen binds slowly and changes the
shape of the protein.
b. The change in shape allows other oxygens to
bind quickly
c. This gives oxygen dissociation curves
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3. The Bohr effect When CO2 levels are high,
acidity increases
4. Hemoglobin binding sites can also bind NO
(nitric oxide), affects blood flow, and CO
(carbon monoxide) leads to irreversible
competitive inhibition and death.