• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/289

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

289 Cards in this Set

  • Front
  • Back
What are the size ranges for life?
10^8 (blue whale) to 10^-13
Describe the difference between scaling and allometry.
Scaling describes how organismal structure and function changes with size; allometry is the study of size and its consequences for organismal function
What is the allometric equation?
Y= aX^b
What is the linear version of the allometric equation?
log Y = log a + b log X
What is the slope for the linear version of the allometric equation?
b (scaling coefficient)
How does the SA:volume ratio change with increasing volume?
SA:volume ratio decreases, because SA does not keep up
What is the scaling of surface area per unit volume?
l^-1 (l^2 / l^3)
What is it called when the slope for a scaling equation is greater than expected?
Positive allometry
What is metabolic rate in mammals not a log-log plot?
Metabolic rate is a power function of mass (vol vs. mass has a slope of 1); there is more tissue to increase metabolism; however, have to dump more heat through surface area (surface area vs. mass has a slope of 2/3); final slope is around 0.75 (between 1 and 2/3)
Do large mammals use more oxygen?
Yes, but not as much per gram of mass (since slope is not 1)
What is the Kleiber curve?
Plot based on a metabolic rate to body mass plot with a slope of 0.75
Describe how metabolic rate to mass actually compares.
Warm-blooded mammals show positive allometry; insects and amphibians dump heat in a same way and have a slope around 0.75; smaller organisms show negative allometry
Describe the slope if metabolic rate was scaled per kg of body mass.
It would be negative
Describe the slopes for the cost of transport vs. body mass in runners, fliers, and swimmers.
Runners cost more than flyers, which cost more than swimmers; however, the slopes are negative and relatively parallel

Swimmers use less energy than fliers and runners (they don't have to support their weight against gravity) and they have different structures to acquire O2; they ahve a system that operates with one chamber
Describe the slop for the cost of transport vs. body mass in mammals.
Negative - larger organisms cost less per kg to move
How does the cost of transport for semi-aquatic mammals compare to the cost of transport for marine mammals?
Cost of transport is higher for semi-aquatic mammals.
Describe some recent results on scaling in human locomotion.
Walking for humans is 20% less costly than expected based on body size, whereas running is about 17% more costly than expected
Describe the scaling of lung volume vs. body mass.
Pretty much isometric (slope of 1.06)
Describe the scaling of capillary volume vs. body mass
Pretty much isometric (slope of 1.00)
Describe the scaling of alveolar diffusion distance vs. body mass.
Slope of 1 is predicted, but slope actually 0.05 because it would be hard to get O2 in.
Describe the scaling of alveolar surface area vs. body mass.
Slope of 2/3 expected, but slope is 1
Why did the elephant die when given a scaled amount of acid?
Geometrically scaled dosage with that of a cat; however, metabolic rate does not scale geometrically ~ might want to scale by brain weight
What are the 5 functions of bone?
1. Stiffness
2. Strength
3. Store calcium
4. Make blood cells
5. Permit muscle to generate movements at joints
Define stiffness.
Resistance to deformation (opposes gravity, permits movement, and protects organs)
What is stiffness the slope of?
Stress vs. strain
On the graph for stiffness, what happens until the points "y" and "f?"
Elastic until hit "y," which is the yield point, and then plastic until hit "f," which is the fracture point
Define strength.
Resistance to deformation or fracture.
What happens hormonally if Ca2+ levels fall?
Parthyroid releaes parathyroid hormone, which cases reabsorption in bone and the kidneys, which is converted to pre-vitamin , which increase the amount of vitamin D in the plasma, which increases ca2+ and decreases Ca2+ excretion.
What type of cells make blood cells?
Haemotopoetic cells
What are the type types of bone?
Compact (cortical) and trabecular (spongy/cancellous); compact is the thick, solid, outer cortex & shafts; trabecular is in the end of bones
What is bone composed of?
65% calcium hydroxyapatite crystals; 23% collagen, 2% non-collagen proteins; 10$% water
What are the different benefits of collagen and minerals?
Collagen: flexibility, resistance to tension, toughness

Mineral: stiffness and resistance to compression
Describe the structure of collagen.
Triple helix of polypeptides (tropocollagen); collagen fibril are bundled into fibers, which are combined to create sheets
What are the benefits of collagen fibers?
Act like ropes to resist tension; they are tough, so it takes more energy to fracture; provide sites for mineralization
Why are fibers in bone often arranged in a plywood like arrangement (lamellae)?
Provides resistance to compression perpendicular to the long axis and resistance to tension parallel to the long axis ~ gives resistance to tension and compression in multiple planes
What are ways in which bone lamellae can be laid down?
Circumferential (around the surface with each layer oriented in a different direction)

Trabecular (layers in small struts)

Osteonal (tube-like layers around a vascular channel; cortical bone is well-vascularized)
What happens to osteons as you age?
Bone is filled with more osteons (secondary osteonal bone replaces original osteon); replaces old bone so that microcracks do not meet and create a large crack
Describe the structure of cartilage.
Poorly organized complex of several components:
- Hydrophilic proteoglycan complexes (GAGs), which are gigantic hydrophilic structures that look like bottle brushes
- Collagen (type II), which holds together the GAGs
- H20, which binds to the GAG, making the cartilage glossy and giving it a wet, translucent appearance
What allows cartilage to act like a water bed for joints?
GAGs have strong negative charges, which repel each other and resist compression
What do ligaments do?
Connect bone-bone; connect and limit movement of the joints
What are ligaments made of?
Collagen bundles with limited elasticity
What do tendons do?
Connect muscle to bone; have an elastic, spring-like function (they can store elastic energy and then recoil)
Describe the structure of tendons.
Made of parallel arrays of collagen and collage-like proteins (elastin)
What are the two main groups of cells in the bone?
- Depository cells, which make materials (bone, cartilage, tendon, ligament, osteoblasts, chondrocytes, fibroblasts)

- Resorptive cells, which get rid of materials (chondroclasts, osteoclasts)
What is the mesenchyme?
Embryonic connective tissue stem cells made up of loosely associated cells (often stellate) and a dispersed extracellular matrix
Describe what mesenchymal stem cells become
Become osteoblasts; if the osteoblast is in the middle of a bunc hof bone cells it becomes an osteocyte
What two organelles are particularly important to osteoblasts?
ER and golgi apparatus to assemble and send out protein (mostly collagen)
What is the two-step process by which osteoblasts syntehsize bone?
1. Lay down a collagen matrix (osteoid, which is early collagen)
2. Mineralize it by creating a supersaturated solution of Ca2+ and phosphate and then essentially adding seed crystals and changing the pH of thematrix to crystallize
What are the two pathways of bone growth?
Intramembranous and endochondral
Describe intramembranous bone formation.
Mesemchyme stem cells ~ Periosteal membrane surrounds the bone (highly vascularized and innervated); memebrane has many osteoblasts, which produce a collagen matrix that they then biomineralize
Describe endochondral bone formation.
Mesenchyme ~ perichondrium, which produces chondrocytes (cartilage-producing), which forms pre-formed bones called anlagen ~ replacement of cartilage with bone
What does it hurt to break bone?
Periosteal membrane is highly innervated
What is characteristic about intramembraneous bone growth?
Shape is determined by what membrane it surrounds; cranial vault, for example, is based on brain size

Bone is added in sutures and is moves through drifts (bone resorption on one surface (osteoclasts) and bone deposition on opposite surface at same rate (osteobalsts))
What are the two intramembraneous bones?
Skull and clavical (because it used to be a bone in the head of fish)
Are the majority of bones formed through intramembranous or endochondral bone growth?
Endochondral bone formation
Describe the process through which analgens become bone.
Central chondrocytes in analgens enlarge to become hypertrophic chondrocytes; nutrient vessels penetrate through teh priosteal collar; chondroclasts are brought by teh vessel and remove cartilage; osteoblasts arrive and replace where the cartilage was; cartilage cells proliferate towards the outside and is essentially being displaced from the center of the shaft
What happens to the size of bone when it experiences strain?
It grows more (force applied to an area causes stress, which generates deformation, which causes strain, which causes osteoblasts to add bone); mostly in young mammals

Exercising individuals also have denser bone, because bone mineral is added
What is osteoporosis?
When bone resorption > bone deposition; osteoporosis refers to bone density between 1 and 2 standard deviations below normal bone density; osteopenia is 1 standard deviation below; severe is greater than 2
What type of bones does osteoporosis cause fractures in?
Trabecular bones
Why is osteoporosis more of a problem for women than for men?
When Ca2+ levels are low, parathyroid gland releases PTH, which stimulates bone resorption by osteoclasts to increase the amount of calcium in the blood; estrogen inhibits PTH, so when estrogen levels fall in post-menopausal women, less inhibitin of PTH, so more resorption of bone by osteolcasts; women also stop growing bone sooner, so they havea lower peak bone mass
What happens when calcium levels rise above a set point in the blood?
thyroid gland releases calcitonin, which stores calcium and causes its level to fall in the blood
What are 4 other factors that influence bone strength?
1. Exercise (lowers rate of resorption)
2. Calcium (too little leads to osteoporosis; too much leads to kidney stones)
3. Smoking
4. Genetics
Why is going to space bad for bones?
Not much loading for bones (so density is not built up)
What are the three processes energy is used for?
Maintenance/metabolism, growth, and reproduction
What growth have an energetic trade-off with?
Reproduction;in mice, for example, energy originally devoted to growth is devoted to producing babies in female mice and fierce competition in male mice
What are the three stages of human growth?
1. Dramatically decelerating growth during infancy
2. Deceleration decreases during childhood
3. Accelerated growth during adolescence
What does it mean that growth in height is more canalized than growth weight?
There is smaller deviance in the growth of height
What are three principle regularities of bone growth.
1. Different parts have somewhat different trajectories
2. There is a high correlation of part-to-part growth (someone with long legs tends to have long arms)
3. High correlation of age-to-age
What is the standard for determining whether there is a clinical concern in one's growth pattern?
Crossing two centile lines (except in adolescence)

Even random parts of the body, such as the eyeball, go through growth spurts during adolescence
What do thyronine hormones control?
General metabolic rate
Describe goiters.
If something impedes production of thyronine hormones (such as iodine defficiency), more TSH is secreted, which causes hypertrophy of thyroid
What is cretinism?
Severe mental retardation and dwarfism due to deficiency in thyroid hormone
In terms of growth, what does insulin do?
Causes glucose uptake and utilization, especially in muscle and fat; essential for all anabolic (building up) processes
What does growth hormone do?
Mitotic stimulant in bone and muscle; stimualtes chondrocytes, which causes growth in skeleton
What hormone is widely abused in sports?
Growth hormone
What conditions result from too much and too little growth hormone respectively?
Too much: acromegaly
Too little: dwarfism
What does insulin-like growth factor 1 (IGF1) do?
Mediates GH action
Give an example of a condition that results from lack of IGF1.
Efe pygmies secrete GH, but do not go through an adolescent growth spurt
In terms of growth, what does cortisol do?
Opposes insulin, causing catabolic action; if stop eating, stop growth because cortisol stimulates catabolism
Describe primary and secondary bone formation in endochondral bones.
Diaphysis is primary bone formation in the shaft; epiphysis is secondary bone formation around the joints
In terms of diaphysis and epiphysis, what do androgens and estrogens do?
Androgens stimualte bone growth (stimulate epithysis where mitotic activity is occurring)

Estrogens stimulate and terminte gown growth (diathysis where ossification is occurring)
What brings bone age in line with chronological age?
Increase thyroid hormone
What does estrogen receptor deficiency cause?
Causes bones to continue to grow; eventually stop, because growth of plates gives out
What is congenital adrenal hyperplasia?
Condition in which adrenal gland pumps out androgens instead of cortisol, resulting in premature development
Where do androgens and estrogens potentiate insulin?
Androgens potentiate insulin in muscle; estrogens potentiate insulin in fat
Describe the negotiation in the size of the female pelvic bone.
Women are caught between wanting to increase pelvis size for parturition and decreasing it for locomotion
Describe the hips of athletic women.
Athletic women have narrower hips, because of delayed puberty and lower estrogen secretion
Are late maturers taller?
Only very slightly (essentially very little variance)
What is ground reaction force (G/GRF)?
Force acting on the foot during the 'stance phase' of gait; results from the support of body weight due to gravity
What are joint moments?
G * R (perpendicular distance to the point of rotation) = Fm * r (moment arm/lever arm)
What is the difference between G and Fm.
G is the force on the body due to gravity; Fm is the resulting force exerted by the muscle
Does G or Fm have to be larger to produce the same M?
Fm (muscle force has to be larger than ground force) because r < R
What is a muscle's gear ratio?
Ratio of moment arms (R/r = Fm/G)
What is smaller ground force due to?
Reduced acceleration and slower speed
What happens if you have a larger r?
Larger M, but smaller displacement (d theta decreases) ~ larger r decrease range and speed)

Smaller moment arm (r) also gives larger muscle force (Fm) for a given ground force)

This is why muscles operate close to joint for rapid movement and farther away from joints for more powerful movements
How do muscles transmit tensile forces?
Via rigid skeletal levels to produce torques that balance external torques and produce movement
On a graph of force vs. deformation (L), what is slop and the area under the line?
Slope = F/L= stiffness (at yield, slope decreases & starts to level off)

Area under = 1/2 FL = work of fracture/toughness/energy absorption (how much energy can a bone withstand before it breaks)
What is the problem of the graph of F vs. L (deformation)?
Does not account for size differences & larger animals can withstand larger forces
What accounts for size differences on a F vs. L graph?
Stress and strain
On a graph of stress (F/A or σ) vs. strain (% change in L or ε), what is the slope and area under the line?
Slope = stiffness or elastic modulus at the material level (structural stiffness is the slop of an F vs. strain graph)

Area under = energy absorption per volume
What is stress (σ) equal to?
F/A which is proportional to W/A (Force is proportional to weight)
What is the symbol for stress?
σ
What is the symbol for strain?
ε
Describe the difference between the stress vs. strain graphs for bone, tendon, and cartilage.
Bone is stiff and strong, so it has the steepest slope and the greatest max stress

Tendon is strong and tough, so it can store and recover elastic energy - approximately as strong as steel, but not as strong as bone

Cartilage is compliant and tough; it is the chock-absorber, so it has the steepest slope, but the lowest maximum stress

Bone can reach highest stress; cartilage can reach highest strain
In terms of strength and stiffness, how does bone compare with tendon and cartilage?
Bone is 1.8 times stronger than tendon and 3 times stronger than cartilage

Bone is 1.8 times stiffer than tendon and 60 times stiffer than cartilage
Define toughness.
Energy to break (work of fracture)
Describe how the Achilles tendon acts like a spring.
Every time one lands, force is applied to the Achilles tendon (it is stretched and stressed, and energy is stored); when one leaves hte ground, the stress and strain go to 0 and energy is recovered)
What is the safety factor?
σf/σmax (strength or stress at which breaks / peak stress ideally seen over a lifetime)
Why is the safety factor important?
Reproductive cost of failure (evolutionary fitness), cost to build and operate, uncertainty of physical environment)
Why can't safety factor be too large?
Cost of having bones and tendons that are too large
What increases when the unpredictability in the environment increases (as in arboreal environments)?
Safety factor ~ birds have a large safety factor
What are the 3 types of loads and which is most important?
1. Compression
2. Bending (most important)
3. Twisting/torsion
Why is the bone's tubular design important?
Increases bones' resistance to bending & torsion; max compression on one side (-ε & -σ), max tension (+ε & +σ), and no stress or strain in the middle); by displacing that bone to the outside, the radius increases which is proportional to I (resistance to bending) increase to the power of 4. Similar to the way flat paper can't support its own weight but a fan can (took more paper away from neutral plane of bending)
What is the equation for bending moment?
M = Ft * L/2
What does I equal
Second moment of area (resistance to bending due to shape); proportional to r^4
What is bending 'flexural stiffness' equal to?
E (material stiffness) * I (structural shape stiffness)
Does the autonomic nervous system have afferent and efferent neurons?
No
What is another name for the autonomic nervous system?
Visceral
What physical changes occur in neurons during learning?
Heads of dendritic spines enlarge
What are NRXNs and NLGNs?
NRXNs are on presynaptic terminal and form a structural connection with NLGNs on dendritic spine; mutations are linked to complex diseases such as schizophrenia
What system has a cranial portion and a sacral portion?
The parasympathetic nervous system
Is the dorsal root ganglion related to sensory or motor neurons?
Sensory
What is different between the connection of the somatic nervous system vs. the autonomic nervous system.
The autonomic has preganglionic fibers that synapse with another postganglionic fiber, whereas the somatic nervous system has one neuron the directly innervates the skeletal muscle (parasympathetic connect in ganglion closer to the effector organ)
What is the resting membrane potential inside the cell?
-70 mV
At resting potential, what are the concentration of ions inside and outside of the cell?
Na+ : 150 mmol/L outside & 15 inside
Cl-: 110 outside & 7 inside
K+: 5 outside & 150 inside
What are the 3 states of ligand-gated channels?
Deactivated (closed)
Activated (open)
Inactivated (closed)
How many ions are related in the sodium-potassium pump?
3 Na+ are let in and 2 K+ are let out
Is the size of the graded potential proportional to the size of the stimulus?
Yes
What is the threshold potential?
-55 mV
What happens if the graded potential surpasses -55 mV?
Na+ channels open ~ Na+ rushes in ~ positive feedback causing more Na+ to rush in ~ potential rises to about 30 mV ~ subsequent inactivation of Na+ channels & opening of K+ channels ~ K+ rush out and bring membrane potential back to 0 mV ~ Na+/K+ pumps bring the membrane potential back to -70 mV
What is the difference between Na+ channels and K+ channels?
K+ channels open more slowly and stay open longer
Why are action potentials propagated more quickly down myelinated axons?
Na+ and K+ channels are only located in the nodes, so action potentials are only in the nodes (saltatory conduction: action potentials jump from one node to the next)
What does the action potentail stimulate ones it arrives at the terminal?
As action potential comes down, Ca2= channels open ~ Ca2+ comes in, which causes neurotransmitter vesicles to fuse with the presynaptic membrane.
How wide is the synaptic cleft?
10 nM
Are Ca2+ channels voltage gated or ligand gated?
Voltage gated
What is the main neurotransmitter for an EPSP?
Glutamate
How many ions are related in the sodium-potassium pump?
3 Na+ are let in and 2 K+ are let out
Is the size of the graded potential proportional to the size of the stimulus?
Yes
What is the threshold potential?
-55 mV
What happens if the graded potential surpasses -55 mV?
Na+ channels open ~ Na+ rushes in ~ positive feedback causing more Na+ to rush in ~ potential rises to about 30 mV ~ subsequent inactivation of Na+ channels & opening of K+ channels ~ K+ rush out and bring membrane potential back to 0 mV ~ Na+/K+ pumps bring the membrane potential back to -70 mV
What is the difference between Na+ channels and K+ channels?
K+ channels open more slowly and stay open longer
Why are action potentials propagated more quickly down myelinated axons?
Na+ and K+ channels are only located in the nodes, so action potentials are only in the nodes (saltatory conduction: action potentials jump from one node to the next)
What does the action potentail stimulate ones it arrives at the terminal?
As action potential comes down, Ca2= channels open ~ Ca2+ comes in, which causes neurotransmitter vesicles to fuse with the presynaptic membrane.
How wide is the synaptic cleft?
10 nM
Are Ca2+ channels voltage gated or ligand gated?
Voltage gated
What is the main neurotransmitter for an EPSP?
Glutamate
What does an action potential in a rpesynaptic neuron result in in the postsynaptic neuron?
A graded potential (EPSP or IPSP)
Where does the action potential start?
The initial segment of the axon after the cell body
What are the main neurotransmittesr of the IPSP?
GABA and glycine
If the postsynaptic ligand-gated channel is non-selective, is the receptor excitatory or inhibitory?
Excitatory
If the postsynaptic ligand-gated channel is K+ selective, is the receptor excitatory or inhibitory?
Inhibitory
What are the two types of summation?
Spatial (summation from different neuronal inputs)
Temporal (repeated stimulation from same input)
Do neurons have either an IPSP or an EPSP?
No, there are many recpetors and EPSP and IPSP are constantly being generated; the summation just has to exceed -55 mV in order for an action potential to fire
What percent of the body weight is made of muscle?
40%
What are fascicles?
Bundles of muscle fibers confined the the perimysium sheath
What are myofibrils made of?
Contractile myofilaments; functional units (sarcomeres) show striation
What is neural integration?
Summation of all input graded potentials (each neuron has approximately 20,000 synapses)
At the neuromuscular junction, what is the muscle fiber membrane called that is depolarized by the action potential?
Sarcolemma
What does tintin do?
Ats as a molecular spring and scaffolding for sarcomere assembly
What are attached to Z-lines?
Actin filaments
What are fascicles?
Bundles of muscle fibers confined in a sheath (perimysium)
What are gibers made up of?
Myofibrils, which are made up of contractile myofilaments (acting and myosin) and sarcomeres
What do titins do?
Act as a spring and scaffolding; extending from one z-line to another
How are sarcomeres structured to improve muscle length/strength?
Stack end to end to lengthen; stack in parallel to make stronger
What do tropomyosin and troponin do?
In the absence of calcium, tropomyosin blocks the myosin binding site on the actin, preventing cross-bridge attachment. Tropinin attaches to the actin and tropomyosin and holds tropomyosin in place.
How does calcium cause cross-bridge binding?
Calcium binds to troponin, so troponin changes shape and pulls tropomyosin away from the cross-bridge binding site
Describe the cross-bridge cycle.
1. Myosin-binding site on actin becomes available, so the energized cross-bridge binds (cross-bridge has hydrolyzed ATP bound)
2. The hydrolyzed ADP + P depart, causing the flexing of the bound cross-bridge
3. Binding of a new ATP to the cross-bridge uncouples the bridges
4. Partial hydrolysis of bound ATP to ADP and P energizes and re-sets the cross-bridge
How many ATP are split in each cycle of the cross-bridge cycle?
One
Are all fo the cross bridges in synch?
No, there are always many cross bridges attached at any one time to maintain force
Do all of the innervated muscle fibers contract when the respective motor nerve axon fires an action potential?
Yes, all the innervated muscle fibers contract.
Is the neuromuscular junction excitatory, inhibitory, or both?
Always excitatory
What is th emuscle cell membrane called?
Sarcolemma
What neurotransmitter is released into the neuromsucular junction?
Acetylcholine
What are the potentials called that are generated in the post-synaptic muscle cell from the neuromuscular junction?
Excitatory end plate potentials (EPP)
What do t-tubulues do?
Conduct electrical depolarization of the sarcolemma into the muscle cell interior

Action potential sweeping down t-tubules is sensed by DHP receptors which synapse with the ryanodine receptor on the sarcoplasmic reticulum, which changes conformation in response to voltage ~ Ca2+ flows out into myofibrils and binds to troponin ~ releases inhibition of tropomyosin ~action/myosin can move past each other
How do muscle cells return to their relaxed state?
Ca2+ pumps are constantly working, so eventually decrease concentration of Ca2+ ~ tropomyosin blocks the binding site & ceases the cycling of myosin heads
What results in the latent period between the msucle fiber action potential and the muscle contraction?
Time needed to releases Ca2+ from sarcoplasmic reticulum, move tropomyosin, and cycle the cross-bridges
What does acetocholine cause in the postsynaptic cell of the neuromuscular junction?
Causes Na+ to diffuse across (excitation)
What is the difference between isotonic and isometric contractions?
Isotonic work against a constant load and shorten as force is generated; in isometric contracts, muscles stay at a constant length but changes
What is the plot for isotonic contraction?
Distance vs. time or velocity vs. time
What is the plot for isometric contraction?
Force vs. time; increasing curve after stimulated then decreasing as Ca2+ channels close (decreasing portion is longer than the increasing portion - peaks at 35 ms and then returns to 0 at 140 ms)
What does repeated stimuli cause in isometric muscles?
Force summates, generating an increase in muscle force (tension)
What happens if successive stimulation occurs rapidly enough in isometric muscles?
Summation reaches non-fused tetanus then reaches fused tetanus around stimuli of about 20-100 Hz, which is about 3-5 times twitch tension (maximal tetanic tension)
Describe the plot of force resulting from stimulation vs. % of rest length when stimulated.
When at 60%, compating of actin & myosin leads to buckling and fewer opportunities for overlap, so force is less than at 100% length; at 140%, stretching causes overlap between acting and mysosin to decreass, resulting in fewer cross bridges, resutling in a parabolic active-length tension curve

At high lengths, passive properties take over, so passive elastic curve results in an exponential increase from 100 to 140

Combined, this results in the total force curve
Describe the graph for velocity vs. force of lifting.
Hyperbolic; high velocity for small forces then cannot even lift hvery heavy objects (becomes isometric at this point)
What does the smallest unit of force that the nerves can generate depend on?
Depends on the # of muscle fibers innervated by motor neurons; the eye, for example, has fewer fibers innervated by motor neurons than the leg, which prevents the eye from jerking around too much
Are all fibers in a single motor unit the same type of fiber?
Yes
Why has fish muscle been a model system fo rstudying muscle recruitment patterns?
Due to the spatial segregation of muscle fiber types
What is the 'size principle' of motor unit recruitment within a muscle?
As you being to move, recruit SO (small, slow motor units, then FOG, the FG (large and fast)
Do larger neurons innervate more fibers?
Yes
Describe the graph for the recuritment of different muscle fiber types.
Motor unit 1 stimulated ~ curves up to a set point; motor unit 2 stimulated ~ curves higher above initial set point to another set point; motor unit 3 stimulated ~ curved even higher above second set point to a third set point
What are the factors degtermining muscle tension?
1. Tension developed by each fiber due to action potential frequency, fiber length, fiber diameter, and fatigue; nu7mber of active fibers (per motor unit and total motor units)
What sense muscle force and length?
Muscle spindles privde information about length; muscle spindles consist of a capsul, intrafusal muscle fiber with afferent nerves wrapped around them (as opposed to normal extrafusal muscle fibers), and a stretch receptor) which relays information about length

Golgi tendon organs provide information about muscle force as stretch in collagen fibers stretches the nerve cell membrane
What does a stretched muscle spindle do?
Generates a burst of action potentials as the muscle is lengthened; the nervosu system decodes this burst of action optentials to determine length
Describe the action potentials caused by golgi tendon organs.
Relaxed muscle shows no action potentials; most action potentials for contraction; fewer action potentials for passive stretch
Describe electromyography.
Electrodes (either surface or needle) and other recording devices are used to measure extracellular potentials resulting from muscle fiber membrane depolarization
What are the 3 types of muscle fibers?
Type I (slow oxidative (SO) or red), Type IIa (fast oxidative glycolytic (FOG) or intermediate), and Type IIb (fast glycolytic (FG) or fast)
Besides acting as a motor and contractor, what are other ways muscle can move bone?
Muscle may function as a strut, spring, or a brake

In walking and trotting dogs, for example, most activity when length not changing; in galloping dogs, active during lenthening, stabilization, and shortening
How many connections are tehre within the typical human brain?
1 * 10^13
What are other names for the forebrain, midbrain, & hindbrain?
Forebrain = prosencephalon
Midbrain = mesencephalon
Hindbrain = rhombencephalon
What does the forebrain (prosencephalon) divide into?
Twin brain (diencephalon) and cerebrum (telencephalon)
What does the hindbrain divide into?
Pons & cerebellum (metencephalon); medulla oblongata (myelencephalon)
What is at the center of the neural tube?
Cerebrospinal fluid, which bathes the cells & connects with blood
Describe fish brains.
Big brain stem, small forebrain, big cerebellum
What part of the body grows most quickly in humans?
Brain (growth occurs within 6-7 years rather than 3-4 as in a chimp)
What is the midbrain involved in?
Connections between brainstem & cortex; involved in ocular motor control
What is the pons involved in?
Relay to cerebellum
What is the medulla oblongata involved?
Regulating basic body functions , such as breathing and swallowing
Describe the cerebellum.
Has as many neurons as the rest of the brain; monitors sensory input from body and coordinates with motor output from cerebrum (motor control, posture, balance, and other autonomic movements)
What does the thalamus do?
Sends sensory output (except smell) to cerebrum; awareness
What does the epithalamus do?
Involved in circadian rhythms
Describe the synthesis of the BBB.
Synthesized in choroid plexus (0.5 l/day, which lines ventricles
What does the BBB permit passage of?
Plasma, glucose, gasses, hormones, small lipid soluble substances (alcohol, heroin)
Describe how non-diffusable substances get across the BBB.
Blood to CSF (break down ATP) and then CSF to brain cells (break down ATP)
What is the circle of willis.
Central conjunction of arteries that supply the brain with blood; provides redundant pathways to get blood to the same place
Describe how the brain drains.
Valveless sinuses; valveless so pressure doesn't prevent blood from flowering out and causes stroke
What is the entire CNS suspended by?
3 dural membrane: outer dura mater, middle arachnoid mater (CSF ffilled), and the inner pia mater
What does the CSF circulate through before being drained?
Ventricles and dural spaces
What is hydrocephalus?
Excess CSF; in childhood, brain case can grow around swelling
How do we know the original projection of the rod through Gage's head is wrong.
Showed going through ventricle; if hole exposes ventricle, air gets in because pressure is lower inside, which causes air embolism; Gage, however, sat upright for 45 minutes afterward
What are the dangerous temperatures for brain cell death?
Below 35 degrees C causes impaired function; below 30 causes cell death; above 39 causes impaired function; about 40-41 causes rapid death
Why do we sweat so much on our sclps and faces?
Countercurrent cooling; cooled blood from sweating enters cavernous sinus, which is next to he carotid artery ~ air is cooled as it goes up (like cold blood in tongues and nose of dogs runs by hot blood going to brain)
What is the scaling of brain mass to body mass?
0.75, like the slope for metabolism (have to pay for the cost of brain);
What is the encephalization quotient?
Actual brain mass/estimated brain mass; highest for humans; dolphins are second
What is fish locomotion caused by?
Lateral undulation of trunk axis powered by alternating contraction of axial (myotomal) muscles
How do amphibians move?
Combination of lateral trunk undulation (retained from fish ancestor) and motion of sprawled limbs; limbs rotated with lateral undulation; as long as the center of mass stays within triangle of support, they will not fall; salamanders use a traveling wave when swimming and a standing wave on land
How do terrestrial mamals and birds move?
More upright planar (parasaggital limb motion) with litle lateral undulation of trunk; limbs move in line of travel at higher speeds ~ evolved dynamic stability so they did not have to rely on statis stability
Why do many quadrupedal mammals employ do increase manuverability and stride length/speed at a gallop?
Dorsoventral spindal flexion ~ quadrupeds run more quickly than bipeds
What does the stride consist of ?
Stance phase + swing phase
What is speed equal to in terms of gait? What happens with increased speed?
Stride rate * stride length; (both increase with increased speed)
What is longer in walking and running respectively - stance phase or swing phase?
Stance is longer in walking; stance is smaller in running
Why did we not evolve wheels?
Wheels are diffcult to evolve (canot be powered by muscles to produce rotation); work only for smooth surfaces; on an ideal flat surface, no KE and PE difference for a wheel, whereas legs require changes in PE and KE in CM of boyd, but allow animals to step over and around obstacles high than r
What is the ground reaction force?
Body pushing against the ground
What are the 3 components of ground force?
Gv vertical (support body weight), Gh fore-aft horizontal (important during acceleration and deceleration), and GML medio-lateral (minimizes tendency to roll - when changing direction)
What is the largest of the components of ground force?
Gv vertical
When does Gv peak?
Mid-support and falls after limb is raised off of hte ground
When does GH increase?
When start pushing in direction of travel
Describe the GRF graphs for Gv, GH, and GMl.
Gv: Increase and then decrease
GH: negative curve then positive curve
GMl: increase then decrease and go slightly below then increase to 0
How does speed and gait affect Gv?
As move more quickly, peak has to increase, because less time of contact with ground;
Describe the graph of Gv for walking.
Increase to peak (as land on heel) then slight dip (as move forward), then increase to a second peak then decrease to 0 (as push off)
What are 2 conditions for steady speed in terms of GRH?
Gh summed over time = 0 (increase and then decrease in speed)
GV summer has to equal body weight
Why did we not evolve wheels?
Wheels are diffcult to evolve (canot be powered by muscles to produce rotation); work only for smooth surfaces; on an ideal flat surface, no KE and PE difference for a wheel, whereas legs require changes in PE and KE in CM of boyd, but allow animals to step over and around obstacles high than r
What is the ground reaction force?
Body pushing against the ground
What are the 3 components of ground force?
Gv vertical (support body weight), Gh fore-aft horizontal (important during acceleration and deceleration), and GML medio-lateral (minimizes tendency to roll - when changing direction)
What is the largest of the components of ground force?
Gv vertical
When does Gv peak?
Mid-support and falls after limb is raised off of hte ground
When does GH increase?
When start pushing in direction of travel
Describe the GRF graphs for Fv, FH, and FMl.
Gv: Increase and then decrease
GH: negative curve then positive curve
GMl: increase then decrease and go slightly below then increase to 0
How does speed and gait affect Gv?
As move more quickly, peak has to increase, because less time of contact with ground;
Describe the graph of Gv for walking.
Increase to peak (as land on heel) then slight dip (as move forward), then increase to a second peak then decrease to 0 (as push off)
What are 2 conditions for steady speed in terms of GRH?
Gh summed over time = 0 (increase and then decrease in speed)
GV summer has to equal body weight
Describe the difference in the GV graph for forelimb vs. hindlimb in quadrupeds.
Hindlimb has a taller GV, because bears more weight support and causes net acceleration (more mass at the head end)
What do primates exhibit forelimb and hindlimb specialization for?
Arboreal locomotion
Describe the CM path for walking and not walking.
When walking, PE and KE fluctuate out-of-phase

When running, hopping & trotting, PE and KE fluctuate in phase, because lose PE and KE when land
What are the energy saving mechanisms for walking and running?
Walking: inverted pendlum
Runing: mass-spring (bouncing gait); leg acts like a large spring such that limb compression via joint flexion is recovered during re-extension
In robots walking ona surface, what is energy loss replaced by?
Sloped surface
How do kangaroos differ from other mamals?
Store more energy when running
When did bipedalism evolve?
6-8 million years ago (after chimps branched off 'main v')
Why do scientists think sahelanthropus was a biped?
Animals tend to look where they are going & FM vs. OP planes indicated sahelanthropus was upright
What is the point of being a biped?
Cost of transport/body mass is lower (0.05 vs. 0.2 for chimps), because we have a shorter moment arm & since torque equals moment arm times force, we have lower hip torque
During what percent of the time is the foot on the ground during walking?
62% ~ acts like a pendulum
What is the biomechanical challenge?
To move Center of Gravity (COG) forward economically and with stability
Describe COG (location and movement).
COG lies 2 cm anterior to 2nd sacral vertebrae; oscillations of COG during walking look like a distorted figure 8
What is the function of the determinants of gait?
To minimize the oscillations of COG
What is determinant 1?
Medial rotation - hip rotates 4 degree towards midline to elongate leading and traling legs adn heel strik, whihc decreases nadir of COG about 1 cm
What is determinant 2?
Pelvic tilt - pelvis on swing tilts inferiorly about 5 degrees as controlled by ABduction of stance hip (slide away from midline) ~ decreases zenith of tragectorial arch about 0.5 cm
What are medial rotation and abduction made possible by?
Small gluteal muscles on side of hip
What determinants do chimps lack?
Determinants 1 and 2
What is determinant 3?
Knee flexion during stance - knee extends at heel strike, but flexes 15 degrees by midstance; extends again at heel off, which decreases zenith of trajectory by about 1 cm
What is determinant 3 caused by?
Gravity and hamstring muscles; controlled by quadruceps
What is determinant 4?
Controlled plantarflexion at heel strike ~ foot plantarflexes and lowers trajectory of the COG between HSS and FF
What are plantarflexors and what controls plantarflexion?
Plantarflexors are claf muscles (gastrocnemius and soleus); plantarflexion is ontrolled by dorsiflexor shin muscles (anterior tibialis)
What is determinant 5?
Powered plantarflexion at heel off ~ rises center of gravity at HO

(Without plantarflexion, the leg would rotate about the ankle joint causing COG to fall after HO)
What does mid-tarsal stiffness cause?
Maintains arch (as opposed to no arch in chimps), because powered plantarflexion requires an arch.
What is out of phase with KE and PE during running?
Elastic energy
Why is running abouncy gait?
Aerial phase then COG in front of hip during falling; no heel strike; knee bent at foot strike; knee bent during swing; opposite arm swing
What are four big challenges of runing?
Energetic cost, stabilization, force resistance, thermoregulation
For the mass-spring model, how is potential energy stored and by what muscles?
Potential energy is storked by U = 0.5kx^2 where k = spring ocnstant and x = displacement

17% stored in achilles tendon; 32% stored in other tendons
How does stride length and stride rate compare with other animals in relation to speed?
As speed increases, speed is about same as horse until levels off at a certain speed; higher than dog

Stride rate increases most slowly to surpass horse; lower than dog
What are the two points of angular rotation and how have humans evolved to accommodate this?
Spin around thorax and between pelvis and legs; humans have more vertebrae than chimps between thorax and pelvis (lumbar region) and narrowed pelvis; we also have separation between head and thorax so we don't have to move side to side while run
What is the point of a stable arch?
Gives us stiffness to push off with our toes
What is the difference between humans COT vs. speed and a pony's COT vs. speed?
For walking in humans and walking, trotting, and galloping in humans, there is a decrease than an increase (so optimal COT is a lowest point); for humans, there is no optimal COT

(Overall, humans COT is greater)
Why is running less costly when barefoot?
Barefoot acts like a spring ~ makes running much less costly (it hurts, however)
What is the difference between angular momentum of sprinter vs. endurance runner?
Sprinters pump their arms to counter angular moment generated by legs which keeps him going straight ~ holds thorax stiffly

Endurance runner doesn't have enough upper muscle mass to counteract legs, so rotates his entire thorax
What does the large gluteus maximus do?
Stabilizes during running - clenches during each stance to prevent COM from falling forward (not active durning walking)
How do humans accommodate for a large GRF?
Large joints to accommodate stress (F/A) - humans are positive allometric for femoral head size vs. body mass
What percent of energy goes into heat when running?
75%
What are the benefits of human evapotranspiration?
Lose about 581 kcal/liter
Independent of respiration
In addition to painting
High endurance rates during running
Who is better at endurance running - a horse or a human, and why?
Human, because better thermoregulation - can jog at a higher speed that requires galloping in other animals (which animals cannot maintain)