the composition of dry air (numbers for O2, N, CO2)
- O2 = 20.95%
- N = 78.09%
- CO2 = 0.03% - treat basically as zero
as you go up in altitude, pressure ___
PO2 = ?
PO2 = FO2 x (Patm - r.h. (PsH2O))
PsH20 = water vapor pressure at certain temps
what determines the amount of gas dissolved in fluid? and Henry's law
- Henry's Law: [gas] = solubility constant x Pgas
Henry's law coefficient for different gases - O2, CO2, N2
- solubility for O2 is very low - not much oxygen is dissolved in liquid (.003 ml/100ml - mmHg)
- CO2 solubility is much higher (.071 ml/100 ml-mmHg) -
- the difference in O2 and CO2 solubility has consequences for their transport in the body
- N2 - .0015 - also pretty low
at equilibrium, is pressure or concentration the same across phases? diffusion depends on....
- so there is more O2 in air than in water and more CO2 in water than in air
average capillary PO2, and average brain/retinal tissue PO2
- capillary = 30-40 mmHg
- brain = 20 mmHg
what does solubility depend on?
- Temperature and salinity
- solubility decreases as T increases
- solubility decreases as salinity incrases
solubility depends on temp and salinity so concentration does too
diffusion works for gases when? when it doesn't work anymore - what is used?
- diffusion of gas is ok for short distances but too slow for long distances
- use convection then!!! - how gases get around the body
- to get gas into lungs use convection (inhale) - at alveoli you depend on diffusion, flow of blood = convection, rely on diffusion to get oxygen into mitochondria
difference between air and water as a respiratory medium
- O2 is much more concentrated in oxygen
- much higher viscosity of H2O than viscosity of air = much harder to move water over resp. passages
- diffusion rate is MUCH higher in air than it is in water
diffusion rate equation
J = Dx (solubility coefficient) x A x (change in P/change in distance)
- J = mass flow, D = diffusion coefficient, A = area
- J is related to pressure gradient, but also related to diffusion coefficient
less important differences between air and water as a respiratory medium
- thermal conductivity of water is much higher than air
- heat capacity of water is much higher than air
- these don't really have much of a role in gas transport though
how does PO2 vary with depth?
- it should stay the same in a sterile lake b/c if there were changes diffusion would cause them to equal out
- but in an unsterile lake - PO2 decreases with depth b/c of metabolism by animals and microorganisms
- (the low diffusion coefficient and high viscosity of water keep downward movement of O2 slow so pressure differences remain)
- concentration of O2 should be higher with increasing depth b/c of coldness if all other things were kept equal
mixed venous blood
blood that is returning to the heart
at different altitudes - ambient pressure is much different. is mixed venous blood pressure any different?
- no - they are about the same - adaptations to have steeper slope for P changes in other parts of the blood (air to alveoli and artery to mixed venous)
- want venous blood to have high enough PO2 so that is can still diffuse into the mitochondria
the two main categories of respiratory designs
- invaginated - like lungs
- evaginated - external or internal gills
- usually lungs = air, gills = water
two categories of gas vs. blood flow (counter and con)
- concurrent exchange - water and blood flow in same direction - worse - at some point there won't be a difference in gradient so not much will be transferred
- countercurrent flow - flow in opposite directions - maintains a gradient across entire length of exchange surface - better
- as medium flows across a respiratory surface, respiratory medium loses oxygen to blood
how do the gills work?
- water is pumped across the gills by the mouth and opercular movements
- blood flows through the arch vessels, along venuoles
- the capillaries are in the lamellae (the offshoots from the arches) - blood flow is countercurrent to water flow
distance between RBC and water in gills
- 3-8 umeters - much bigger than in us
- the gills must have water flow to keep them open - will collapse in air
two other categories of gas vs. blood flow for when the medium is air
- cross-current - intermediate effectiveness between counter and concurrent exchange
- cross - air flow is to the right, and blood flow goes across - what birds have
- tidal - is the most inefficient - relies on diffusion at the bottom --> no uniform flow of respiratory medium - air goes down and gets stuck in chambers
- these two designs are for when the medium is air
characteristics of mammalian lungs
- LOTS of surface area
- several layers of respiratory membrane (epithelium for alveoli, basement membrane, capillary basement membrane, and endothelial cell in capillaries)
- this is less than 1 micron thick
- BUT still not all the air gets exchanged - 150 ml of dead space
is respiratory surface area vs. body weight an allometric function?
- BUT also, homeotherms have higher exchange area b/c of higher metabolic rates
- the ectotherms don't need as much oxygen - less surface area
- fish use this to get air from the water
- they open their mouth and swim to run liquid across their gills
- good for high O2 demands - some use just ram ventilation, others use it when their swimming speed increases
- more energy efficient than opercular pumping at higher speeds of swimming
- another possibility besides lungs/gills
- insects have these
- trachae - tubes in which air diffuses through
- pores in the surface are called spiracles
- some insects even pump air into the trachea to boost diffusion with convection
- another possibility to get air
- gas transport through skin - no specialized respiratory organ
- works well in amphibians especially
- small for most reptiles, mammals, birds
why do reptiles have lower amount of gas transport through skin?
- much lower permeability to water - b/c in terrestrial conditions
- don't want to lose water and dry out!
the anatomy of the lungs/thorax - what helps quiet/heavy breathing
- lungs are passive - no muscles to do with ventilation
- lungs are encased in closed chamber - you move the wall of that chamber (the thorax)
- lungs are connected to the thorax by a vacuum in the pleural space
- the small negative pressure (relative to atmospheric) of the intrapleural space balances elastic recoil of lung and chest
- during quiet breathing, just diaphragm
- during heavy breathing - use thorax too
so how do we ventilate?
- small pressure changes expand the lungs
- when you breathe in, the interpleural space gets more negative
- air flow is determined by difference between atmospheric and alveoli pressure (Palv goes neg when Pip goes neg)
- BUT - at end of respiration, Pip is more negative, but alveoli pressure goes above zero
- this is because air enters the lungs until the Patm-Palv difference is zero
- what happens when you puncture the chest wall
- you lose the negative pressure inside the intrapleural space
- lung collapses
what is different about bird lungs?
- they have other air sacs in the body
- these sacs are connected to the lung for holding air
- cross current gas flow - very efficient - good for high altitudes
- no alveoli
- the parabronchi are channels
- non-tidal - one way flow
what is different about bird respiration?
- breathes air through trachea
- goes into posterior air sacs
- expiration - air flows across the lungs
- inspiration - air pulled from lungs into anterior air sacs
- expiration - pushed out of sac and out of trachea
- 2 cycles!
crosscurrent exchange in birds
- blood flow in channels adjacent to parabronchus
- more efficient than tidal
- the fluid dynamics of air flow cause the air to go across parabronchi instead of back through trachea on first exhalation
how would you optimize the respiratory system?
- max lung volume
- max surface area between external medium and blood
- minimize thickness of interface (easier to diffuse)
- mas flow rate of fluids passing resp. surface (increase pressure difference across fluid space across long - lower IP pressure)
- actively move fluid (not tracheas like insects)
- optimize exchange geometry (countercurrent, crosscurrent, tidal)
- minimize dead space
- live in air not water
the similarities in the O2 cascade in water and air breathers and the differences
- similar: stepwise gradient form medium to tissues
- different: the difference between lung PO2 and arterial PO2 is much smaller than gill PO2 to arterial PO2.
- why? - diffusion across the respiratory membrane is faster in air breathing animals!
what is different about CO2 and O2 that will influence CO2 elimination form the body?
- there is a lot less CO2 in the atmosphere -partial pressures will be different
- solubilities will be different - CO2 much more soluble in liquid than O2
- CO2 carried in blood in form of bicarbonate
- CO2 doesn't really attach to the heme in hemoglobin
why is there a huge drop between alveoli and ambient air in the CO2 cascade for lungs?
- because tidal exchange is really bad
- CO2 must leave by diffusion - CO2 backs up in the system, increases PCO2 everywhere
what are the PO2 and PCO2 values for entering and leaving the lung?
- PO2 entering = 40 mmHg
- PO2 leaving = 100
- PCO2 entering - 45
- PCO2 leaving = 40
- bigger difference in O2 across lung than CO2!
and what it is for carbs, amino acids, protein
- CO2 produced/O2 used =respiratory quotient
- 1 for carbs
- 0.8 for amino acids
- 0.7 for proteins?
- we produce about as much CO2 as we use O2!
what form of the gas contributes to partial pressure?
- only the dissolved form!
- Co2 in blood is carried in 3 ways (Hb, dissolved, and converted to HCO3
- O2 in blood carried in 2 forms - dissolved and Hb
ventilation and equation for it
- rate at which medium is made to flow across respiratory organ
- = frequency of breathing x tidal volume
rate at which blood flows through respiratory organ
how do water breathers regulate ventilation?
- monitor O2 concentration in incurrent water
- CO2 concentration is usually too low to monitor (b/c its usually as HCO3 or other compounds, it diffuses away from gills too fast to monitor)
- ventilation increases if O2 in water decreases b/c this decreases O2 in blood
regulation of ventilation for air breathers
- control based on CO2 concentration b/c its closely linked to pH of blood
- b/c so much O2 is stored in hemoglobin, we are less affected by the inspired O2 concentration
- increase blood CO2 = more ventilation
- decrease blood O2 = increased ventilation (takes bigger change in O2 than CO2 though)
- no effect if more O2 than normal
sensors in mammals that regulate ventilation?
- pulmonary stretch receptors
chemoreceptors in mammals
- in the medulla of the brain
- detect pH and/or CO2
- very important for ventilation rate
- small change in CO2 = big change in respiration
- also in carotid and aortic bodies - they detect O2 in blood
pulmonary stretch receptors
- these are called baroreceptors in the lung
- help control breathing rhythm
- mediated by skeletal muscle, but essentially all automatic and controlled by brain stem
- increase of stretch = decrease in inhalation
- 2 alpha, 2 beta
- 4 globins each with a heme - iron atom
- the heme is where the oxygen binds
- so hemoglobin can bind 4 oxygen molecules
the 4 kinds of oxygen binding proteins
where are hemoglobins found?
- protostome and deuterostome phyla
- intracellular in muslce (myoglobin)
- extracellular in blood (polymers)
- intracellular in blood (RBC)
hemocyanins and where found
- molluscs and arthropods
- blue not red
- extracellular in blood
- heme based and similar to hemoglobin
- only in a few annelids
- extracellular in blood
- iron based, but not heme based
- in several phyla
- intracellular in blood
why are the monomeric to tetrameric hemoglobins only intracellular and not extracellular?
- if small ones were extracellular they would gum up the kidneys! - plug up glomerulus and kidney
- there would be too high of an oncotic pressure in extracellular blood (pressure due to proteins in blood)
- the polymers don't seem to cause this problem, are present in extracelular blood
equation for vol % and what the numbers are for at rest and heavy exercise
- vol% = mlO2/100 ml blood
- 5 vol% is extracted at rest - so it goes from 20 to 15
- 15 vol % is extracted for exerise, so it goes from 20 to like 5
extraction = ?
- the SaO2 - SvO2
- mucher higher in exercise
QO2 = ?
- the oxygen utilization/consumption (like metabolic rate)
- = F (SaO2 - SvO2)
- F = blood flow for organ or for whole body (for whole body F would be cardiac ouput!)
- called the Fick principle
what 3 properties does O2 binding vary with?
- P50 - affinity of hemoglobin for oxygen (partial pressure at which blood is half saturated with O2)
- the lower the P50 = the higher the affinity
- Cooperativity - how easy it is for 2nd, 3rd, etc. to bind after one or two is already attached
- Total amount of pigment in blood - is the plateau
SO2 equation and what each variable means
SO2 = Smax (PO2^n / (P50^n + PO2^n))
- Smax = total amount
- P50 is affinity
- n = cooperativity
- gives s-shaped curve!
how do P50, cooperativity, smax vary the O2 concentration curve?
- P50 - shifts curve left and right
- smax - shifts curve up/down - same shape, same P50, just higher or lower
- cooperativity - with more cooperativity the curve gets steeper!
how does pH and PCO2 and temperature affect affinity for O2
- if gets more acidic (like during exercise) - no effect on smax or cooperativity, but P50 increases, graph shifts right = Bohr effect!
- Root effect - max O2 saturation can also vary with CO2
- an allosteric modulator of O2 affinity
- if you increase amoutn of 2,3 DPG, you increase the P50 = lower the affinity of hemoglobin for O2
why are most organs in parallel in the mammalian circulatory plan?
- allows each of them to have access to high pressure that comes out of the aorta
- to drive the blood through the organs
- the liver and kidney are not parallel though!
artery vs. vein
- artery - flows away from the heart (oxygenated except pulmonary)
- vein - flows toward the heart (partly deoxygenated except pulmonary)
the conduction system of the heart
- heart must contract ALMOST as a single unit - starts at apex of heart and spreads downward
- from SA node, to AV node (specialzied cardiac muscle - a myogenic heart)
- then through bundles to bottom of heart
why is the left ventricle thinker than teh muscle of the right ventricle?
b/c the systemic resistance is much higher than pulmonary resistance!
what is the average presure of systemic circuit and pulmonary circuit at the arteries?
- systemic - 90 mmHg
- pulmonary - 20 mmHg
- b/c resistance in pulmonary is much lower than in systemic
- measure the activity of the heart
- happens b/c a small amount of current flows out to the surface of the body
- show where the heart depolarizes/repolarizes
- ventrical depolarization = QRS wave
- ventricle repolarization = T wave
- P = atrial depolarization
- the wall of the heart that has the coronary circulation (circulation to body of the heart muscle)
- we have a compact myocardium with coronary arteries and veins
- spongy myocardium - little/no coronary vessels - it perfuses as same time that ventricle perfuses - allows smaller enough distances between muscle and blood that diffusion of O2 works!
- can also be a mixed structure - blood flows from lumen into coronary veins - vessels that emminate from the ventricle itself (invertebrates)
what are the heart valves mostly controlled by?
- when blood flows from ventricle into the aorta, the aorta and arteries expand and store pressure in their elastic walls
- during diastole, thw all of the aorta (muscular and springy) will contract and push blood through the circulation
how does total cross sectional area and average velocity of blood change over the circulation system
- much larger cross sectional area in the smaller vessels (biggest in capillaries)
- b/c of this velocity is lowest in capillaries
- you want this slowing of blood so that there is time for oxygen to leave and pick up CO2!
- you also want a ton of area so that they have enough area for oxygen to diffuse out into the tissue
Flow rate equations
- F = change in P/R for each vessel
- F = volume/time
- R = resistance to flow
- Fartery = all F in areriole = n(F arteriole) --> conservation of mass
- F = V x A (v = velocity, A = cross sectional area)
the resistance of the group of arterioles is lower or higher than the resistance of each arteriole
- with more arterioles = more paths - resistance is much lower than resistance of each one
- more channels = easier for blood to get through!
how is resistance of the gorup (Rt) related to individual resistances? (Ri)
- Rt = Ri/n
- n = number of aterioles/capillaries, whatever it is
so Ri is bigger than Rt!
where is the largest presure drop in teh circulation?
- at the arterioles! - have largest resistance in teh system
- this is also the place hwere you can adjust resistance to lower or raise the blood flow
why is there resistance to blood flow?
b/c fluid is viscous - slipping past itself takes up some energy
laminar flow of blood vessels
highest velocity at center - velocity at walls = zero
- for all circulation except capillaries! - b/c the RBC are larger than capillaries - can't have middle of RBC go faster than edges
- RBC must move all at once
R = (8nl)/ (r^4 x pi)
- n = viscosity
- l= length
- r = radius
how is resistance in the circulation regulated?
- change diameter of arterioles - lots of smooth muscle around arterioles - none around capillaries
- change number of capillaies that are open - change diameter of sphincter muscles
- resistance controlled largely at arteriole level
- autonomic control - smooth muscle - sympathetic for norepinephrine
- metabolic local control - if more O2 used in tissues, vessels will dilate
- chemical factors - drugs like histamine, angiotensin, nitric oxide
cardiac output and equation for it
- flow through the whole circulation
- the flow into each side
- C.O. = (Pa - Pv) / TPR
- TPR = total peripheral resistance
- since Pv = o
- Pa = C.O. x TPR
cardiac output equation involving heart rate and stroke volume
- C.O. = HR x SV
- HR = heart rate, frequency
- SV = stroke volume - amount of blood pumped on individual beat
- if you want to incrase CO you usually increase both HR and SV
- TPR decreases so Pa stays the same
the two pressure components for capillaries
- hydrostatic - usually forces fluid out of the capillary and into the blood
- decreases as you go across the capillary
- oncotic (pressure due to proteins in blood) - stays constant and wants water to be drawn into capillaries (Acts against hydrostatic pressure)
- Net filtration = k ((Pcap-Pecf) - (picap - piecf)
- k = filtration coefficient
fish circulatory plan
- one pump not two
- pump blood once - through gills and then through systemic circulation
- pressure will be lower
- lower cardiac output
- low C.O. b/c MR is lower!
- can have ABO's
- air breathing organs
- puts circulatory plan into parallel instead of series
- mouth, gut, swim bladder
- swim bladder also used for buoyancy control
circulatory plan of lungfish!
- don't use gills for oxygen transport
- have lungs!
- blood goes into pulmonary circulation to get oxygenated - not gills
- 1 atrium 1 ventricle
- have two auxilary chambers to help with pumping tho
- before atrium there is the sinus venosus
- bulbus arteriosis (conus in tuna b/c its contractile)
- 2 atria, 1 ventricle
- frog - has a conus with two outlets - not as much mixing between deoxygenated oxygenated blood
non crocodillian reptile hearts
- 2 atria, 1 divided ventricle
- many inlets and outlets - no auxillary things
- effective separation between pulmonary and systemic in ventricle
- 2 atria - 2 ventricles, but not totally parallel system
- completely separated ventricles
- when submerged tho - they can direct blood away form pulmonary circulation (can't get air so why?)
mammal and bird heart
2 atria, 2 ventricles
- they have a single pump, but the gills come after the tissues
- lack of vessels by tissues - no endothelialized channels
- blood perfuses tissues - collects in sinuses
- distributino of circulation is not as finely tunable as ours
- blood gets back to heart by muscular contraction
open circulation heart
- heart is refilled by elastic recoil
- blood enters via ostia openings
electrogenic heart vs. myogenic
- electrogenic - pacemaker is neural not muscular like myogenic
- one neuron is pacemaker
what is different about octopus circulation?
- its a double circuit
- two branchial hearts that are separate from systemic heart
how much of us is water?
- 2/3 of it is intracellular
- 1/3 of it is extracellular (interstitial fluid and plasma)
water only moves if there is a ____ gradient
what ions dominate in seawater?
- Na and Cl
- lots of Mg and SO4 also
- much higher osmolarity than seawater!!
freshwater fish - problems
- they are hyperosmotic
- so they gain water by osmosis and lose ions by diffusion
- therefore they must excrete lots of urine that is hypoosmotic
- AND actively take up Na and Cl (in food and through gills)
marine teleost fish - problems
- they are hypoosmotic - bigger difference than in freshwater fish too
- so they gain ions by diffusion and lose water by osmosis
- must have concentrated urine - but they can't do this (isoosmotic)
- urine has high concentrations of Mg and SO4 though
- need to actively pump salt across their gills
marine elasmobranchs - problems
- like sharks
- they are slightly hyperosmotic but they are hypoionic!
- this is because of the concentration of urea and TMAO in their bodies
- they gain some water by osmosis
- and they also gain salt by diffusion
- so they must excrete concentrated stuff --> do this with their rectal gland secretions (rich in salts)
counteracting solute and an example
- a solute, in which you have a high concentration of to activate enzymes that balance the effect of urea inactivating them
- TMAO is sharks
- also could be other methylamines
compatible solutes - do humans use them?
- they can raise osmolarity and have no effect on enzymes
- glycerol, glycine, arginine, proline, serine (amino acids)
- humans use them in cells in renal medulla where osmolarity is high
how freshwater fish regulate salt
- use the gills
- there is a Na/K pump at the basal membrane
- Na will then cross passively across apical membrane
- to get chloride across apical membrane - you have counter transport with HCO3 gradient to have energy for Cl transport
marine fish salt regulation
- must secrete Na and Cl
- at basal, Cl is transported by secondary active transport with K and Na
- Cl across apical is then passive
- at basal, Na comes in coupled with K and Cl
- but no way for Na to go out at apical - b/c of negativity outside cell - it gets pulled out paracellularly between the gill epithelial cells
- the pumping cells
- in marine fish - there are tons of mitochondira in it and pavement cells almost completley cover ti
- in freshwater fish - the pavement cells just surround the chloride cell
gas transporting cell
salt gland and how it is controlled
- used by reptiles and birds in their heads
- there are lobes full of epithelial cells that allow for this
- controlled by high blood osmolarity - parasympathetic stimulation of the gland (AcH?) and then salt is secreted.
- drying out - because skin and other surface allows for evaporation
- a problem for terrestrial animals!
evaporation and body weight
- dessication is an allometric function
- the smaller animals have a larger rate of evaporation because of body surface area!!
relationship between size and urine concentrating ability
- smaller animals have higher max urine osmolarity
- this partially compensates for the greater rate of evaporation in smaller animals
what regulates thirst?
- blood osmolarity and angiotensin
- which stimulate release of ADH - for water conservation
metabolic water production relation to body size
- smaller animals produce more metabolic water b/c their metabolic rate is higher!
- means we are ureotelic
- medium toxicity
- medium amount of water needed to excrete it
- medium cost of production
- medium solubility
what do we make for nitrogen excretion?
- uric acid
excrete ammonia as nitrogen waste?
- ammonotelic - mostly aquatic vertebrates
- but highly toxic
- low cost of making
- must have a lot of water with it to excrete it
- high solubility
use uric acid for nitrogen excretion?
- birds, many reptiles, sharks
- low toxicity
- high cost or metabolic production
- small amounts of water required for excretion
- low solubilty - precipitates out (bird poop)
urine vs feces wastes
- urine - eliminates prety much everything made in teh body/absorbed into the blood (water, ions, amine groups, cellular metabolism products)
- feces - eliminate components of food that could not be digested - are usually never actually inside the body
path of circulation in the kidney
renal artery --> afferent arteriole --> glomerular capillaries --> efferent arteriole --> paritubular capillaies or vasa recta --> renal vein
equation for E =
which parts are not included for water, Na, and H
- E (extraction) = F - R + S
- water - no secretion
- Na - no secretion
- H - no reabsorption usually
what determines GFR?
- the amoutn of fluid filtered
- Hydrostatic pressure (Pgc - Pbc)
- Oncotic pressure which opposes filtration -
- Filtration coefficient K
- GFR = k x glomerular filtration pressure
what is much of reabsorption driven by?
- active Na reabsorption in proximal tubule!
- about 75% of total water and Na reabsorption occur in proximal tubule!
- all of glucose is reabsorbed in proximal tubule too!
why do we secrete things if we filter so much? (2 reasons)
- 1 - sometimes we need regulatory adjustments for secretion late in the tubule
- 2 - sometimes you don't filter enough! like H+
how is osmotic gradient created in extracellular fluid in medulla?
partially by active ion pumping from thick ascending limb of Loop of Henle (pumps out ions) whereas descending limb is permeable to water so it flows out
- antidiuresis hormone
- causes insertion of aquaporin 2 water channels in apicla membrane
- at basal - the aquaporins are already present and open!
how does relative medullary thickness relate to body weight?
- decreases as animals get bigger - more able to concentrate their urine
- increased ADH secretion with increase in blood osmolarity and decrease in ECF volume
- causes ADH release from hypothalamus which allows for water reabsorption in CT
- acts on distal tubule
- increases Na reabsorption
- increases K secretion
- its a steroid so it makes more Na/K pumps at basal and more apical K channels
regulation of aldosterone
- more release from adrenal cortex when increase in K concentration in plasma or when blood pressure decreases
- it eventually causes more water reabsorption!
- the primitive organization for nervous systems
- no organized groups of neurons
- contacts are pretty random at crossing points
- like our enteric nervous system
what do bilateral animals show for their nervous systems?
- centralization (into ganglia)
- cephalizatoin (ganglion in head)
cerebrum, thalamus, hypothalamus
what does the cerebrum include?
- cerebral cortex (outer covering)
- sensorimotor processing
- like eye movements
pons, medulla, cerebellum
motor learning and feedback to control motor function
group of cells in CNS
bundles of axons within ganglia in CNS
smooth muscle, cardiac muscle, some endocrin/exocrine glands
what parts of the brain control autonomic function?
hypothalamus and hindbrain
which function has no autonomic component?
which part is only autonomic?
what are the 3 types of neurons?
- exist without environmental information
- a biological clock controls these rhythms
- the main biological clock in mammals
- its in the hypothalamus
- like the pineal gland for birds
what is the cellular unit of vertebrate striated muscles? and description of it
- the muscle fiber
- very long
- its functional unit is the myofibril that runs parallel in it
purpose of T-tubules
- carries the excitation of the plasma mebrane due to acetylcholine releasing Na
- causes depolarization!
how much of the muscle mass is due to the myofibrils?
what does calcium due to actin/myosin binding in skeletal muscle?
- Ca binds to troponin complex - moves tropomyosin!
- allows for them to bind!
- a molecule that goes from Z line (by actins) to the M line (by mysoins)
- helps with elastic recoil of stretched muscles
- anchors the actin
- is inelastic unlike titin
motor unit definition
a motor neuron and the fibers it innervates
the receptors in skeletal muscle in excitation-contraction
- Dihydropryidine receptor (DHPR) on t-tubule and Ryanodine receptor (Ryr) on SR
- action potential opens them!
- allows Ca to be released from SR
how does Ca get back into SR?
what are ATP's three main jobs in skeletal muscle excitation contraction?
- disconnects the actin-myosin bond
- the myosin head moves
- pumps the Ca back into SR
useful tension of a skeletal muscle?
- 70%-140% because of sliding filament theory
- you want as many crossbridges in right orientation as possible!
- don't want too scrunched but also dont want to lengthened
what are the series elements in muscles? parallel elements?
- series - tendons
- parallel - titin, SR membrane, blood vessels
most normal contractions start isometric/isotonic and go isometric/isotonic?
- start isometric
- go to isotonic
do sarcomeres in parallel or series exert more force?
- larger diameter = larger force!
velocity-load curve for skeletal muscles
- if no load - velocity of contraction is fast
- if max load - no movement - contraction is isometric - velocity is zero
- much less prevalent than twitch muscles
- no action potentials in teh muscle membrane!
- innervated at several points
- slower contraction but more efficient
- mammals = only in muscle spindles, extraocular muscles
- lower vertebrates - in postural
what is different about invertebrate muscle?
- more than one neuron per muscle fiber (motor units overlap)
- fewer total neurons per muscle than in vertebrates
- also have inhibitory motor neurons (we just inhibit in CNS)
smooth muscle characteristics
- in vertebrates
- lots more actin than in striated
- actin attaches to membrane at dense body
- slow but efficient
- chemical/neural signals but also spontaneously
- related to intracellular Ca but a lot comes from extracellular
- large contractile range
single unit smooth msucle
- acts like a big single cell b/c of all the gap jnctions
- more hormonal control, some neural control
- can spontaneously depolarize
- in small blood vessels, late in the uterus contractions
mutliunit smooth muscle
- few gap junctions - acts as separate cells
- more neural control
- rarely sponteaneously depolarizes
- in large blood vessels, in early uterus contractions, in hair follicles
how is Calcium different in smooth muscle?
- must be extracellular too
- Ca binds to CaM - which activates MLCK - phosphorylates myosin - allows binding to actin
homing vs migration
- homing: return to starting point (usually more frequent than migration)
- migration: seasonal/life-cycle movement - over a longer distance than homing
the reliable cues from environment for navigation
- sun - light and polarization
- star positions
- magnetic fields
- chemical gradients
- internal maps
how to use the sun position for navigation
- sun always moves 15 degrees per hour (from E to W)
- seen in bees - there little dance
polarization of the sun for navigation
- sunlight is unpolarized
- 90 degrees to sun is max polarization
- it reflects off atmospheric water and dust particles
- must know degree of polarization and time of day to determine where sun is - determine where you are
- must have an oritentation of photopigment to do this (arthropods and birds)
using star position for navigation
- stars rotate around Polaris in the North
- its a learned behavior!
use magnetic cues for navigation
either the magnetic field (weak but reliable) or dip angles
magnetic cues mechanisms?
- particles of magnetic materials (like in nose of trout)
- electroreceptors in lateral line in Sharks to detect magnetism
- light induced electron transfer between photopigments?
- track direction changes/distances to make direct path back to home
- no map though - can get displaced
1a afferent neuron
- used in stretch/myotactic spinal reflexes
- are sensory axons associated with muscle spindles
simple, graded response to a specific stimulus
the working fibers - generate the load
gamma motor neurons
- involved in stretch reflex
- innervate the intrafusal fibers --> if you increase their activity you increase the muscle spindle activity
- allwos for load compensation - maintains sensitivity of the reflex
- make indirect connections with motor neurons - for protection
- like stepping on a tack
twitch and its 3 periods
- response to single action potential - normally an all or none thing
- latent period
- contraction period
- relaxation period
- when the muscle does not shorten much as it exerts a tension on a force it cannot move
- pulls on the elastic elements
- the muscle changes its length as it exerts a tension on a load
- tension = constant
- concentric (shortens) or eccentric (lengthens)
slow oxidative muscles
- slow at rate of cross-bridging (300 ATP/myosin-sec)
- many mitochondria
- aerobic catabolism
- smaller diameter = less force over all
- lots of blood capillaries
- slow to fatigue
- posture, slow movements
fast oxidative muscles
- fast at cross-bridging (600 ATP/myosin-sec)
- many mitochondria
- medium diameter
- lots of capillaries
- slow to fatigue
- repeated movements
fast glycolytic muscles
- fast at cross-bridging (600 ATP/myosin-sec)
- few mitochondria
- anaerobic glycolysis
- fast to fatigue
- large diameter = large force!
- few capillaries
- quick, fast movements, jumps
in a motor unit - are all the muscles fibers of 1 type or more?
map sense for navigation
- have some sort of representation of position and goal position
- is learned
- landmarks, smell, magnetic cues?
- turtles use different cues for different parts of travel!