Animal Physiology Exam 2 Flashcards
Hypothalamic-pituitary-gonadal axis (HPG)
responsible for regulation of the reproductive (sex hormones) and immune systems
The hypothalamus secretes what?
Gonadotropin releasing hormone (GnRH)
GnRH stimulates what?
Anterior pituitary to secrete luteinizing hormone (LH) & follicle stimulating hormone (FSH)
LH and FSH act on what?
testes and ovaries to release testosterone (or estrogen)
Estrogen
in females, it promotes development and maintenance of female characteristics and behavior, oocyte maturation, uterine proliferation; stimulated by FSH & LH
Testosterone
In males, promotes development and maintenance of male characteristics, behavior, and spermatogenesis; stimulated by LH
What is the ecological relevance of testosterone?
- influences development of male secondary characteristics (crests, throat fans, color)
- related to aggression
- may both stimulate & retard growth
Sexual dimorphism
morphological differences between male and females
- e.g. male cuban anole lizards are larger than females because of faster growth rates
- growth rates largely determined by circulating levels of testosterone
Testosterone influences what?
aggressive behavior & competition among males for mates, thus, testosterone may be involved in sexual selection may influence mate choice (more blue)
Maternal provisioning of yolk testosterone influences what?
phenotypes of both males and female offspring that may influence fitness
What is correlated with testosterone levels in spiny lizards?
Mite parasitism; fitness cost of testosterone
Immunocompetence handicap hypothesis
increased levels of circulating testosterone cause an increase susceptibility to infection (reduced immune system)
What fitness benefits and costs does testosterone provide?
benefits: increased endurance, movement, and home range area
Cost: decreased growth rate & survival + increased parasitism
Muscle functions
locomotion, repositioning, internal movement, organism shape & form, support, protection, heat production
Type of muscle cells
cardiac, smooth, skeletal
which muscle cells are striated?
cardiac & skeletal
Which muscle cells are voluntary? Involuntary?
Voluntary: skeletal
Involuntary: smooth & cardiac
Skeletal muscle
- bundles of fibers
- attaches via connective tissue to bone
antagonistic muscle groups
muscles that cause opposing movements
e.g. bicep & tricep
Muscle organization
muscle - fiber bundles - fibers (cell) - myofibrils - sarcomere - actin (thin) + myosin (thick)
Muscle contraction produced by what?
Sliding filaments
1) myosin heads pull on thin filaments
2) Sarcomere unit shortens
Molecular interactions underlying muscle contraction (steps)
1) rigor conformation
2) breaking the cross-bridge: ATP binds & myosin releases actin
3) Hydrolyzing the ATP causes the angle of the myosin head to change
4) and Myosin head binds actin
5) Power stroke: fueled by phosphate leaving
6) Myosin unbinds ADP & remains bound to actin (rigor)
Thin filament
Actin: binding site for myosin
What are the regulatory proteins of actin (thin)?
tropomyosin & troponin
Relaxed muscle state versus contracted
relaxed: No Ca2+ present in cytoplasm
contracted: Ca2+ present
Calcium regulation of muscles
1) Ca2+ binds troponin
2) tropomyosin moves, exposing myosin binding sites
3) myosin head binds & makes power stroke
4) thin filament is moved
What triggers calcium release?
Excitation-contraction coupling
Excitation-contraction coupling steps
1) action potential: releases ACh
2) ACh binds ligand gated Na+ channels, Na+ enters = AP
3) AP depolarizes T-tubule: triggers voltage sensitive DHPR conformation change
4) Ryr Ca2+ channel opens & Ca2+ diffuses into cytoplasm
5) Ca2+ can now bind troponin and move tropomyosin
6) ACh is degraded: stops AP
How does Ca2+ get removed from the cytoplasm?
ATP-dependent Ca2+ pumps
Muscle twitch
mechanical response to action potential
Isometric twitch response
same length; tension developed is NOT sufficient to move load and muscle stays the same length
Isotonic
same tension; tension developed IS sufficient to move load & muscle shortens
what determines the tension by muscle?
frequency of action potentials
Summation
Action potentials in rapid succession (leads to twitches)
very high frequency stimulation produces what?
Tetanus = “fused” contraction
Muscular work depends on what?
ATP
ATP functions in muscle
1) binds myosin head: release actin
2) ATP hydrolysis: activates myosin cross-bridge
3) ATP hydrolysis: Ca2+ pumped into SR
How is ATP generated?
1) creatine phosphate
2) glycolysis
3) oxidative phosphorylation
Most ATP generated in a short-duration
Anaerobic glycolysis with phosphagen
All ATP is made by what in long-duration events?
catabolism
Tonic muscle fibers
- don’t generate action potentials
- slow cross-bridge cycling = long, sustained contraction with low energy cost
Twitch muscle fibers
- generate action potentials
- most common
- 2 main categories: slow oxidative & fast glycolytic
slow oxidative fibers (twitch)
- contract slow
- fueled by oxidative metabolism
- lots of aerobic enzymes
- lots of mitochondria and myoglobin: makes fiber more resistant to fatigue
fast glycolytic (twitch)
- contract quick
- powerful
- fueled by glycolysis
- lots of glycolytic enzymes
- low mitochondria volume
motor unit
motor neuron + all skeletal muscle it stimulates
each axon branches innervate what?
multiple muscle fibers
each fiber receives synaptic input from what?
one motor neuron
when motor neuron fires action potential
all muscle fibers in the motor unit contract
Recruitment
increased muscle contraction force by increased number of active motor units
muscle force proportional to what?
cross-sectional area
Transport of gases =
passive
For O2 to move from environment into cells, conditions must be what?
favorable for passive transport
What are respiratory gases?
O2 & CO2
- principal gases consumed and produced by cellular respiration
Dalton’s law
total pressure exerted by mix of gases = sum of pressures of individual gases
PV = nRT
Partial pressure
individual pressure exerted by any particular gas in a gas mix
Px = Fx x Ptot
Diffusion of gases dependent on what?
variation in partial pressures
Partial pressures of a gas is proportional to what?
the concentration of that gas in gas phase
Atmospheric pressure what with altitude?
decreases
Henry’s law
Gases dissolve in liquids in proportion to their partial pressures
Cx = A x Px
Henry’s law depends on what?
- solubility in specific fluids
- temperature
- presence of other solutes (salinity)
Gases diffuse from what?
High Px to low Px
solubility what with increasing temperature?
decreases
solubility what with increasing salinity?
decreases
gases diffuse more readily through what than what?
air than water
Respiration via diffusion alone only possible at what?
<1mm distance
Gas transport is enhanced by what?
convective movement (bulk)
- unidirectional flow
- tidal flow
oxygen cascade of people
ambient air - alveolar gas - arterial blood - capillary blood - mitochondria
Solubility of Oxygen in blood =
low
What increases O2 carrying capacity by 50x?
metalloproteins
3 types of respiratory pigments
1) hemocyanins (copper)
2) hemerythins (iron)
3) hemoglobin
Hemocyanins
- copper
- anthropods & molluscs
- dissolved in hemolymph
- blue when oxygenated
Hemerythins
- iron
- brachiopods, annelids
- inside coelomic cells
- violet pink when oxygenated
Hemoglobin
- most common
- verts, nematodes, annelids, insects, crustaceans
- globin bound to heme (Fe)
- carried by RBCs
- red = oxygenated
Fetal hemoglobin
alpha-globin & gamma-globin
Adult hemoglobin
alpha-globin & beta-globin
Mammals Hb
fairly uniform in composition
Ectotherms Hb
mixes of 2,3, up to 10 different forms of Hb
O2 equilibrium curve
functional relationship between percent of binding sites oxygenated & partial pressure of O2
As PO2 drops, less & less of what is required to cause the same unloading of O2?
drop in partial pressure
myoglobin
- no cooperativity
- 1 binding site
- function independently
Hemoglobin
- cooperativity
- partially bound Hb = increased oxygen affinity
- 4 O2 binding sites/ molecule
cooperativity enhances what?
responsiveness of the process to changing PO2
No cooperativity =
low PO2 pressure necessary to release 80% of O2
Cooperativity =
unloads 80% of its O2 at much higher O2 partial pressure
O2 equilibrium curve Shape reflects what?
a trade-off between loading & unloading O2
O2 equilibrium curve height shows what?
how readily pigment binds to O2
High O2 affinity =
loads more easily = shift LEFT
low O2 affinity =
unloads more easily = shift RIGHT
Bohr shift
a right-shift in the normal curve due to decreased pH & an associated increase in CO2
decreased pH means shift
right
increased PCO2 means shift
right
Bohr effect typically what?
enhances O2 delivery
increased temperature does what to O2 affinity?
decreases O2 affinity; shift RIGHT
increasing temperatures promotes what?
O2 delivery during exercise
Specialized breathing structures
1) gills (external & internal)
2) lungs
3) cutaneous
4) tracheae
Respiratory surfaces must be what?
ventilated
- reduces static boundary layers
Passive ventilation
nondirectional
Active ventilation
- tidal
- unidirectional
- nondirectional
Tidal gas exchange
1) fresh medium mixes with stale medium in the lung, so the PO2 of the medium @ the exchange surface with the blood is below that in the environment
2) O2 diffuses into the blood flowing along the exchange surface. The PO2 in the blood rises
3) The PO2 in blood leaving the lung remains lower than that in the exhaled medium
Countercurrent gas exchange is more efficient than what?
cocurrent gas exchange & Cross-current gas exchange
Area of gas exchange increases with what?
increasing body size
Thickness of gas-exchange is relatively constant with what?
increasing body size
Challenges to breathing in water
- H2O 1000 times denser than air
- H2O has 100 times greater viscosity
- solubility of O2 in water is 30x lower than in air
Advantages to breathing in water
- easier to eliminate CO2
- air breathing causes dehydration
Bucal-opercular pumping steps
1) buccal cavity (mouth) refilling causes buccal expansion, reducing the pressure, which draws in water.
2) Operculum draws water across gills
3) buccal pressure forces additional water across gills into opercular cavity
4) relaxation phase prior to next ventilation cycle
Ram ventilation
when swimming at 50-80 cm/s or greater, some fish simply open their mouth to ventilate gills
reliance on air increases as what?
dissolved O2 in habit decreases
Amphibians have what?
paired, unicameral lungs
How do amphibians ventilate?
buccopharyngeal pressure
simplest lung is
unicameral
Inhalation = what in snakes & what in lizards?
elastic expansion in snakes, intercostal ctx in lizards
Exhalation = what in snakes & what in lizards?
muscular compression in snakes, elastic relaxation in lizards
Upper respiratory tract
mouth, nasal cavity, pharynx, trachea
Lower respiratory tract
bronchi & lungs
Airways of the lungs
bronchioles & alveoli
Alveoli are what?
sites of gas exchange
The airways of human lungs
- tidal ventilation
- highly vascularized
- High SA
- low diffusion distances
