exam 3

Question 1

organisms live seasonal lives

Answer 1

1) 3 energy costly events:
- migration ( spring and fall)
- molting ( renewal of feathers)
- breeding
2) seasonal living involves important physiological aspects
- an internal circannual clock
- zeitgeber or external cues to keep the body clock in synch with the environment
3) hormone regulation to coordinate timing and annual events such as reproduction

Question 2

zeitgeber

Answer 2

important to coordinate physiological mechanisms with the “local” environment
2) the most important one in birds and mammals is photoperiod (day length)

Question 3

gonadal hormone basics

Answer 3

• regulate both primary and secondary sexual characteristics
• have organizational and activational effects
  
  • organize and determine the development of male and female reproductive anatomy
• activate reproductive changes in physiology and behavior
• are mainly secreted by the gonads but have other minor sites of secretion ( adrenal glands)
• regulated through hypothalamic-pituitary-gonadal axis

Question 4

Testosterone vs estrogen

Answer 4

• testosterone and estrogen differ very little in chemical structure, and one enzyme changes testosterone to estrogen (estradiol)
• aromatase is also known as estrogen synthase

Question 5

Testosterone

Answer 5

1) effects before birth
- masculinizes the reproductive tract and external genitalia
- promotes descent of the testes into the scrotum of most mammals
2) effects on sex-specific tissues
- promotes growth and maturation of the reproductive system at puberty
- essential for spermatogenesis
- maintains the reproductive tract throughout adulthood
3) Other reproductive effects
- develops the sex drive at puberty
- controls gonadotropin hormone secretion
4) effects on secondary sexual characteristics
- induces the male pattern of hair or feather growth
- causes the voice to deepen because of the thickening of the vocal cords
- promotes muscle growth responsible for the male body configuration
5) nonreproductive effects
- exerts a protein metabolic effects
- promotes bone growth at puberty and then closure of the epiphyseal plates
- induces aggressive behavior

Question 6

Testerone secretion

Answer 6

1. seasonal breeders show an increase in T before and during breeding seasons
2. T levels in humans and other non-seasonal breeders often show circadian rhyths

Question 7

alternate reproductive strategies

Answer 7

1) phenotypic plasticity and different developmental fates in individuals can lead to alternative phenotypes within populations
2) when these alternative phenotypes relate to sex and reproduction. they are called alternative reproductive strategies
- alternative mating strategies can be condition-dependent, density-dependent, or fixed

Question 8

white-throated sparrow example

Answer 8

1) variation in androgens cause 2 color morphs as well as a large supergene on chromosome 2
-Tan males have lower T than white males
4 sexes:
1) Male white-throated: aggressive, promiscuous, poor parental care, nests more in the open, and sing often at high frequencies
2) female white-throated: similar behavior to males and they even sing
3) male tan-throated: less aggressive, faithful, and a good parent, nest in more wooded habitats, and sing less and at lower frequencies
4) female tan-throated: similar behavior to males, but do not sing

Question 9

rock paper scissors lizards

Answer 9

3 color morph
1) the ultra-dominant polygynous orange-throated males
2) the more monogamous mate-guarding, blue males
3) “sneaker” yellow-throated males, which look like females
- yellow males tend to be recognized by blue males, but not by orange males
O>B, B>Y, Y>O
- orange and blue males actively defend a territory
- yellow males tend to cluster around the territories of orange males, probably because they are more successful in “sneaking” copulations from the females on an orange male’s territory compared to a blue male’s territory
Tradeoff:
high testosterone lowers survival chances significantly (T suppresses the immune system)

Question 10

Female endocrine cycles

Answer 10

1) endocrine cycles in females coordinate:
- estrous (a period of fertility and receptivity, sometimes called “heat”)
- behavioral
- lasts until pregnancy
- often timed with ovulation
- may include menstruation if pregnancy does not occur
-Two important internal cycles characterize reproduction in females
1) ovarian cycle: prepares and releases an egg, becomes endocrine ( secretes estrogen)
2) Uterine cycle: prepares the uterus for implantation, becomes endocrine (secretes estrogen and progesterone)

Question 11

female gonad hormones

Answer 11

as in males, the gonads (ovaries) are regulated by two anterior pituitary hormones:
1) luteinizing hormone (LH)
2) Follicle stimulating hormone (FSH)
also as males, gonadal hormones impact other tissues and exert feedback on the hypothalumus and anterior pituitary

Question 12

female reproductive system

Answer 12

Ovaries: release oocytes, (ova, or unfertilized eggs) and secrete the hormones estrogen and progesterone
Oviduct( or fallopian tube or uterine tube): duct to transport oocyte to the uterus, site of fertilization
Uterus: organ where zygote grows and develops
1) endometrium : supports fertilized egg and forms part of placenta after implantation occurs, sloughs off during menstrual flow
2) myometrium: smooth muscle, expands during pregnancy, contracts during labor and orgasm
3) cervix: the narrow opening in the lower part of the uterus that permits sperm to enter the uterus and allows the fetus to exit during birth

Question 13

hormonal regulation of cycles

Answer 13

1) ovarian and uterine cycles are linked. OC drives UC
2) The cycling of hormones in the pituitary gland and reproductive structures is caused by both positive and negative feedback

Question 14

feedback control of follicular phase

Answer 14

• early on low levels of estrogen from the maturing follicle inhibit release of LH
• inhibin inhibits FSH and further development of follicles
• later in the follicular phase, increased levels of estrogen from the maturing follicle prompt release of LH and FSH resulting in the hormone surge prior to ovulation

Question 15

Luteal feedbacks

Answer 15

• progesterone dominates effect on the hypothalamus and pituitary and inhibits release of FSH of LSH

Question 16

simple version

Answer 16

1) FSH release (follicle develops and secretes estrogen)
2) Increased levels of estrogen promote FSH and LH release (positive feedback)
3) LH peak results in ovulation
4) Corpus luteum degenerates and, with no fertilization, progesterone and estrogen levels drop
5) menses

Question 17

Corpus luteum during pregnancy

Answer 17

1) chorionic gonadotropin is secreted into the blood by embryonic chorion, and sustains the corpus luteum during early pregnancy
2) when the child is born and the placenta is expelled, blood concentrations of estrogen and progesterone plummet

Question 18

Positive feedback during birth

Answer 18

1) myometrial contractions force the fetus against the cervix, stimulating mechanoreceptors that send action potentials to the hypothalamus
2) oxytocin- secreting neuroendocrine cells in the hypothalamus become more active
3) oxytocin is secreted into the general circulation in the posterior pituitary at an increased rate
4) blood oxytocin concentration rises
5) oxytocin stimulates the myometrial smooth muscle to contract and stimulates the smooth muscle to secrete prostaglandins which also stimulates contraction
6) strengthening contraction increase mechanoreceptor stimulation

Question 19

Follicular phase cells and hormones

Answer 19

1) hypothalamic GnRH cells (secrete GnRH): stimulates the secretion of FSH and LH from anterior pituitary cells
2) Anteriory pituitary gonadotropin cells (secrete LH): stimulate theca cells to secrete androgens during the follicular phase, a surge of LH triggers final maturation of the oocyte and ovulation, after ovulation, LH initiates the transformation of follicle cells into corpus luteum
3) anterior pituitary gonadotropin cells (secrete FSH): stimulates aromatase action in granulosa cells for conversion to estrogen
4) Theca cells of ovarian follicle (secrete androgens): diffuse from theca cells to granulosa cells for conversion to estrogen
5) granulosa cells of ovarian follicle (secrete estrogen (principally estradiol): acting together with FSH stimulates the proliferation of granulosa cells, at low concentrations has a negative feedback effect on the anterior pituitary, promotes estrous behavior in species that exhibit estrus, promotes growth of endometrium and development of endometrial progesterone receptors
(secretes inhibin): inhibits FSH secretion

Question 20

Luteal phase cells and hormones

Answer 20

Corpus luteum cells secrete progesterone, estrogen, and inhibin
1) progesterone: causes the endometrium to become secretory; promotes relaxation of uterine and oviduct smooth muscles
2) estrogen: acting together with progesterone, reduces secretion of FSH and LH from the anterior pituitary; thereby greatly suppressing folliculogenesis in primates and slowing folliculogenesis in other mammals
3) inhibin: inhibits FSH secretion

Question 21

Pregnancy

Answer 21

Placental cells secrete chorionic gonadotropin, progesterone, estrogen, and lactogen
1) chorionic gonadotropin: secreted y embryonic placental cells in primates and horses, in which it rescues the corpus luteum and ensures the maintained function of the corpus luteum
2) progesterone: opposes the stimulatory effect of estrogen on uterine smooth muscle until late pregnancy, stimulates the secretion of prolactin from the anterior pituitary, synergistic with estrogen and prolactin, promotes growth of mammary glands
3) estrogen: synergistic with progesterone and prolactin, promotes growth and development of mammary glands, acting together w/ progesterone (prevents milk secretion by mammary glands), prepares the uterine smooth muscle for parturition by promoting production oxytocin receptors and synthesis of connexins that form gap junctions between muscle cells, stimulates the enzymatic breakdown of cervical collagen fibers, thereby softening the cervix
4) lactogen (chorionic somatomammotropin): alters maternal glucose and fatty acid metabolism to shunt glucose and fatty acids to the fetus; may contribute to development of capacity for lactation

Question 22

contraceptive methods that affect hormones

Answer 22

1) oral contraceptives, depo-provera injections, and silastic implants
- contain progesterone, or both progesterone and estrogen
- inhibits LH and FSH release, and therefore prevents ovulation
- very reliable 99-100%
2) RU486 (mifepristone): can work 1-3 days after intercourse and up to 10 weeks
- blocks the action of progesterone and results in menses in pregnant women
3) Lactation after childbirth
- reduces LH production and prevents ovulation, only lasts a few months, and then the menstrual cycle will return
- not reliable, too variable

Question 23

Mammary glands and lactation

Answer 23

1) suckling produces mechano-sensory stimuli transmitted to the CNS
2) as a consequence of changes in hypothalamic neurosecretory activity, prolactin, and oxytocin are released at increased rates into the general circulation
3) prolactin stimulates the alveolar epithelial cells to secrete milk into the alveolar lumen
4) oxytocin stimulates the myoepithelial cells surrounding each alveolus to contract and eject milk from the alveolar lumen

Question 24

membrane potential

Answer 24

difference in charge between outside and inside cell
- represents force exerted on a charged particle
- any cell has a negative voltage inside relative to the outside of the cell ( resting potential)
- in most cells (and neurons and muscles at rest), the membrane potential is determined by EK bc K is the most permeable ion by far ( has leak channels that facilitate K diffusion)

Question 25

flow

Answer 25

• sodium is the major cation and chlorine anion outside the cell
• K+ is higher inside the cell as well as PO4

Question 26

what forces act on charged particles

Answer 26

• permeability (ion channels)
• concentration (determines net flow)
  
  • K+ flows down its concentration gradient ( H - L)
• this results in an electromotive force which will become equal and opposite (no net flow)
• ## Na/K pumps always pump Na out and K in to establish a concetration gradient

Question 27

The Nernst equation

Answer 27

• describes the electrochemical equilibrium potential across a membrane for a single permeant ion
• Eion+ (58/z) log([ion]o/[ion]i) units in mV
• Ek: - 58 mv
• this is the equilibrium potential for potassium at the given concentration, where the chemical gradient is exactly balanced with the electrical gradient. At Ek, influx and outflux of potassium will be equal

Question 28

biological membranes

Answer 28

• more ions are present and permeabilities to different ions vary even at rest
• need Goldman equation for this situation
  Neurons
• there are more K+ leak channels than any other type of channel open at rest. if we can set Pk to 1.0 then PCI= 0.45 and PNa= 0.04
• or K carries 67% of the current in neurons at rest, Cl carries 30%, and Na only 3%

Question 29

current

Answer 29

• measured in amps, symbolized by I
• the rate of movement of an electrical charge through a conductor such as a copper wire
• In the nervous system, current is the flow of charged particles through an ion channel or down an axon
• current is determined by potential and conductance

Question 30

potential

Answer 30

• measured in volts
• describes the force exerted on a charged particle
• voltage reflects the difference in charge between two points, such as an anode and cathode in a battery, or the two sides of the membrane in cells
• the larger the voltage potential, the greater the current flow

Question 31

conductance

Answer 31

measured in mhos
- the ease at which current flows through a conductor. the reciprocal of resistance

Question 32

resistance

Answer 32

• the reciprocal of conductance (1/g)
• resistance is a measure of how difficult it is for a current to pass through a conductor

Question 33

flow of information

Answer 33

• receive input from dendrites, flows down the axon to axon terminal which causes the release of neurotransmitter
• neurotransmitter binds neurotransmitter receptor molecules and effect occurs

Question 34

action potential

Answer 34

stages
1) rising phase: depolarization ( away from resting potential)
2) falling phase (return to resting potential)
3) undershoot: below threshold
- the farther away the ap is from Ek, the higher driving force is on K
General features
1) the stimulus for an action potential is depolarization ( from resting potential)
2) once action potentials occur the happen fully ( all or none)

Question 35

voltage-gated channels

Answer 35

1) only one channel quickly shuts after it opens in response to depolarization
2) any one channel either has no conductance ( when shut) or a small conductance when open
3) there is no stimulus to shut a channel once a channel is open, shutting the channel is time-dependent

Question 36

channel kinetics

Answer 36

1) voltage-gated Na channels open quickly in response to depolarization and inactivate quickly
2) voltage-gated K+ channels open slowly in response to depolarization and shut more slowly
3) voltage-gated sodium channels have 3 conformational states: closed, open, inactivated
- K only has open or closed

Question 37

Vm change (rising)

Answer 37

1) rising occurs when Na influx > K efflux which occurs when Pna > Pk
2) initial depolarization causes voltage-gated Na channels to open (P na increases)
3) if/when PNa&raquo_space;> Pk threshold current is reached the AP will occur
4) Na influx is greater than K efflux
5) Vm moves toward ENa

Question 38

Vm overshoot

Answer 38

1) voltage-gated Na channels continue to open
2) PNa&raquo_space; PK and Na influx&raquo_space; K efflux, but mechanisms for repolarization begin slowly
3) some voltage-gated Na channels begin to inactivate
4) more K channels begin to open up
At the peak of the AP
PNa = PK and Na influx = K efflux, so there is no net current flow and Vm does not change momentarily

Question 39

Vm falling phase

Answer 39

1) even more voltage-gated K channels open
2) more voltage-gated Na channels inactivate and some start to close ( and continue to close until the absolute refractory period is over
3) PNa &laquo_space;PK, and Na influx «< K efflux
4) Vm moves towards EK

Question 40

Vm undershoot and recovery

Answer 40

Undershoot
1) because both K leak channels and voltage-gated channels are open PK&raquo_space; than PK at rest
2) “Excess” PK conductance offsets the effect of Na and Cl on the resting membrane potential, and Vm gets very close to EK
3) Most voltage-gated Na channels are inactivated and many are transitioning to closed
Recovery
1) voltage-gated K channels begin to close, Pk returns toward a resting value
2) Vm returns toward resting

Question 41

the hodgkin cycle

Answer 41

1) initial depolarization - opening of voltage-gated Na+ channels increases PNa
2) Increased Na flow
3) Further membrane depolarization
4) 1 is repeated

Question 42

TTX

Answer 42

• a potent, antagonist for voltage-gated Na channels
• 2 mg is enough to kill a 75 kg human
• created symbiotic bacteria
• binds to voltage-gated Na channels
• blocks flow of Na ions through channels, preventing action channels

Question 43

Scorpion alpha toxin in scorpions

Answer 43

• slows inactivation of Na channels
• prevents A. P. from ending
• rhythmic actions are inhibited ( breathing, heartbeat)

Question 44

Batrachotoxin (BTX)

Answer 44

• irrevisibly binds to the Na+ channels which causes a conformational change in the channels that forces the sodium channels to remain open ( agonist)
• leads to paralysis

Question 45

Cone snail

Answer 45

• have a variety of deadly toxins in their venom. K-conotoxin, like TEA ( antagonist for voltage-gated K channels)
• A.P falls very slowly

Question 46

Refractory period

Answer 46

absolute
1) Na channels inactivation is responsible for the absolute refractory period b
2) No stimulus can open an inactive channel
- during this short period, many Na channels are inactive, so the stimulus cannot open them
relative
1) The slow closing (or prolonged opens) is responsible for the relative refractory period
2) The extra K+ conductance causes the undershoot and makes it harder for Na+ influx to overcome K+ efflux: Na channels can be opened but more must open to offset the extra K conductance

Question 47

Neuronal signaling

Answer 47

1) passive axons will lose charge as the signal travels down the axon
- two resistances impact flow down the axon (and action potential velocity
- Ra= will reduce internal flow
- Rm= membrane resistance can reduce charge loss across the membrane , therefore improving flow down the axon

Question 48

myelination

Answer 48

• increases conduction velocity
• myelin sheath composed of layered glial cell membrane
• node of Ranvier ( spaces between myelin)

Question 49

Blood

Answer 49

• 45% = RBC
• plasma = 55%
• WBC
  Function
• carry oxygen and some carbon dioxide
  Shape and structure
  1) small disk cells (biconcave)
  2) can bend or fold to pass through small blood vessels (no nucleus in mature cells)
  Origin
  1) stem cells in bone marrow
  Life span:
  1) 120 days in Humana (3000 round trips per day)
  Control of production
  1) hormone: erythropoietin

Question 50

Homeostasis of blood 02

Answer 50

1) kidneys detect reduced O2 carrying capacity
2) kidneys secrete the hormone erythropoietin (peptide) into the blood
3) erythropoietin stimulates erythropoiesis
4) erythrocytes increase O2 carrying capacity
5) the increased O2 carrying capacity relieves the initial stimulus that triggered erythropoietin secretion
6) leads to acclimation to low ambient O2 levels

Question 51

chemical structure of hemoglobin

Answer 51

1) HB is (1) a major reserve of oxygen and (2) helps facilitate oxygen uptake by keeping the partial pressure of dissolved oxygen in the blood low
2) Most oxygen is reversibly bound to hemoglobin in RBC
- each hemoglobin molecule can carry four O2 molecules maximum
- affinity of hemoglobin for O2 depends on PO2 to which the hemoglobin is exposed
- a small amount of oxygen is dissolved directly into the plasma, but not much due to the low solubility of oxygen in water

Question 52

internal respiration

Answer 52

HbO2 -> Hb + O2
HbO2: oxyhemoglobin
Hb: deoxyhemoglobin

Question 53

external respiration

Answer 53

Hb + O2 -> HbO2
partial pressure determines whether external is occurring
1) increased pressure= binding
2) decreased pressure= unbinding
3) as partial pressure increases, saturation increases
Functional consequences
1) Pp high at rest ( high saturation)
2) Pp low at exercise ( low saturation)
- as Pp drops 5ml of O2/ 100 ml is unloaded and smaller drops of Pp are required with time

Question 54

myoglobin

Answer 54

• hyperbolic curve ( no subunit cooperatively)
• higher affinity for O2 (P50)
• curves to the left ( higher binding affinity)
• curves to the right ( lower binding affinity)

Question 55

a diversity of blood oxygen equilibrium curves

Answer 55

Occurs in two main ways
1) the shape or variation in P50, occurs due to molecular differences in the respiratory pigment’s amino acid sequence that impact oxygen binding
2) The height, or total amount of O2 in the blood, reflects oxygen-carrying capacity, or the total amount of respiratory pigment in the Hb blood

Question 56

Changes in Hb oxygen affinity to temp and organophosphates

Answer 56

1) temperature increases the affinity of hemoglobin for oxygen decreases
2) temperature changes cause conformational changes in the structure of the hemoglobin molecule
3) Hemoglobin shows a similar shift with accumulation of 2,3-biphosophoglyceric acid (BPG), a metabolite of glycolysis in RBCs. As the rate of metabolism increases, the affinity of hemoglobin for oxygen decreases

Question 57

Gas transport

Answer 57

1) 70% of CO2 is carried by carbonic acid or bicarbonate
2) 20% as carbaminohemoglobin. CO2 binds to NH2 groups, the protein portion of Hb
3) 10 % as dissolved gas
- proportions depend on temperature, pH, and ionic content of plasma
4) The largest source of H ions and flux (and the biggest influence on blood pH) is associated with CO2 production!
5) Blood pH is homeostatically maintained at pH between 7.35- 7.45

Question 58

The Bohr effect

Answer 58

1) The pH of blood affects the affinity of hemoglobin for oxygen.
2) As CO2 increases and pH decreases, the affinity of hemoglobin for oxygen decreases ( shifts curve to the right)
Why?
- a conformational change occurs in the structure of hemoglobin that causes hemoglobin to bind oxygen less tightly
Importance
- increases O2 unloading levels when CO2 levels increase ( and the reverse)
- in the capillaries, CO2 rises and pH decreases, promoting O2 unloading
- oxygenated blood= less CO2

Question 59

the Haldane effect

Answer 59

1) deoxygenation of Hb in tissues allows blood to carry more CO2 and H+ and reduces the pCO2 as CO2 enters the blood by:
- facilitating the formation of bicarbonate
- forming carbaminoHb

Question 60

weddell’s seal

Answer 60

1) Thermoregulation: maintaining a core temp of 37C in water often below 0C
2) osmoregulating- living in salt water incurs the same challenges we observed in whales and other marine organisms
Diving challenges
1) extended apnea and hypoxia while swimming and hunting
2) exposure to extreme pressure
3) finding and maintaining access. holes in the winter ice sheets

Question 61

duration and depths of dives

Answer 61

Duration
1) most dives are short in duration ( less than 25 minutes)
2) Capable of dives over an hour
- human static apnea record: men (24 min, 37 sec) women (18 min, 32 sec)
- human dynamic apnea record with fins: men (300 m), women (245 m)
Depth
- most dives are less than 200 m deep
2) capable of dives up to 600 m

Question 62

physiology

Answer 62

1) Because the thorax is highly compressible in marine mammals, lung volume decreases dramatically as ambient pressure increases
2) some animals inhale before diving but most exhale
3) lung volume, and hence lung O2 storage, during a dive is largely inconsequential
4) any O2 in the lungs is unavailable during a deep dive because the alveoli collapse easily under pressure

Question 63

seal physiology

Answer 63

1) diving mammals have large blood O2 stores
- max blood store/kg = max O2 carrying capacity x blood volume
- O2 carrying capacity is determined by Hb
- Humans: 15 ml/kg
- Weddell seal: 60-85 ml/kg
2) Weddell seals and other phocids have both higher O2 carrying capacity and higher volume of blood (huge cardiovascular load)
Adaptations for hypoxia
1) diving mammals have high (myoglobin) and large myoglobin-bound O2 stores
- humans: 4-9mg/gram wet weight
- Weddell seal: 55-70 mg
2) Myoglobin is a “private” store of O2 for muscle. It can actually “pull” O2 out of the blood due to its higher binding affinity
3) Myoglobin will only release CO2 at low Pp. Blood flow reduction to muscle during the dive promotes this
4) Regional vasoconstriction limits blood flow to most of a diving mammal’s body during protracted ior forced dives
- regional vasoconstriction is caused by sympathetic control of vasomotor events to:
- skin
- appendages
- kidneys
- digestive system
5) blood flow is reserved for
- the heart itself (coronary blood flow)
- the brain
- the lungs
- this ensures proper O2 diffusion for the heart muscle which relies largely on aerobic metabolism for ATP and the brain
- this increases total peripheral resistance to blood flow and thus increases blood pressure
Diving bradycardia: reduced heart rate offsets the effect of vasoconstriction on mean arterial pressure
1) bradycardia is caused by increased activity in the parasympathetic neurons innervating the heart
- vasoconstriction and bradycardia are graded responses

Question 64

RBC resevoir in the spleen

Answer 64

Blood RBC can be increased ( up to 15%) in about 10 - 20 min of diving
1) comes from the spleen
2) increases blood viscosity which also increases TPR increasing the need for bradycardia

Question 65

membrane potential in brain neurons of seals

Answer 65

1) despite conserving O2 for brain metabolism, phocid brain tissue is more resistant to some of the negative effects of hypoxia on neurons
- seals can remain conscious at O2 levels that would cause humans to black out

Question 66

Is metabolism aerobic or anaerobic during a dive

Answer 66

Both depending on dive length and tissue
1) despite myoglobin stores of O2, the muscle becomes anaerobic even during relatively short dives
2) lactic acid builds up and so does CO2 for earlier aerobic metabolism
Remain in muscle until an animal resurfaces: no blood flow to the muscle
3) build-up of blood CO2 increases acidity in the blood, which usually causes a ventilation response in mammals
- seals have a reduced sensitivity to blood acidity and CO2 levels, decreasing their ventilation response

Question 67

Lactic acid in muscles and blood

Answer 67

1) the muscles start to release their accumulated lactic acid when the animal resurfaces, causing the concentration in the circulating blood to rise
2) the concentrations in both muscle and blood eventually converge and thereafter fall together as lactic acid si metabolized
3) tens of minutes are required to restore the blood concentration of lactic acid to its original level

Question 68

Aerobic dive limit

Answer 68

1) the ADL for seals is 20-25 min
2) ADL = longest dive that can be undertaken without a net accumulation of lactic acid above resting values
- total O2 stores never permit dives longer than ADL to be fully aerobic
3) overall MR decreases during dives, despite increased activity
- allow regional hypothermia of extremities and lower body temperature (inhibition of shivering thermogenesis saves energy)
- decrease digestion to decrease specific dynamic action
- decrease locomotion cost, by gliding and decreasing buoyancy

Question 69

AP worksheet

Answer 69

How can conductance be non-zero values but achieve Vm= 0
1) the inward flow of Na must outward flow of K ( flowing at same rate)
- can achieve this with Na in:out = 1:10 and K in:out= 10:1, then set their conductance to equal non-zero values
Why does ratio of Na+ outside determine the height of action potentials?
- the ratio of Na in:out changes ENa and therefore the driving force on Na and how “high” Vm goes
Decrease refractory period
1) lower K maximum conductance: will mean Vm will not drop as low during the undershoot, making it easier for Na influx to reach the threshold and fire an AP
2) increasing the maximum Na conductance: will strengthen Na influx relative to K efflux making it easier to rise to the threshold for each action potential
3) increasing K closing speed: will mean that Vm will not drop as low during the undershoot (because it will be shorter in duration), making it easier for Na influx to reach the threshold and fire a second action potential
4) increasing the Na equilibrium potential: will increase the driving force on Na influx making it easier to rise for each action potential
How is axon diameter related to axial conductance
- increasing diameter increases axial conductance ( or the ease at which current travels down the inside of the axon). This lowers Ri to current flow
Relationship between axial conductance and AP velocity
- increasing axial conductance increases AP velocity
- myelin increases membrane resistance and thus AP velocity

Question 70

Withdrawal or Flexion reflex

Answer 70

1) Modulation via chemical synapses is important to achieve inhibition, as well as excitation
- stimulus: thermal pain receptor in paw
- afferent pathway: sends sensory info to brain
- efferent pathway: motor neurons deliver signal to effector organs

Question 71

Neurotransmitters

Answer 71

1) acetylcholine
enzyme: (choline acetyltransferase)
receptor: nicotinic
receptor type: ionotropic EPSP
receptor: muscarinc M1- M
2) norepinephrine
enzyme: TH and dopamine B-hydroxylase
receptor: a1,2,3
metabotropic

Question 72

Black widow toxin

Answer 72

• alpha latrotoxin from the black widow spider causes massive vesicle release independent of Ca influx
• alpha latrotroxin interacts with neurexin and inserts itself into the membrane of presynaptic terminals, forming a pore that allows Ca influx
• neurexin is a presynaptic surface protein involved in the normal formation of synapses

Question 73

spatial vs temporal summation

Answer 73

temporal: one presynaptic neuron repeatedly releases NT
- spatial: more than one presynaptic neuron releases NT onto a single post-synaptic neuron