BIO 120 FINAL EXAM

Proximate questions - immediate causation, development

• How?

Ultimate questions - evolution, adaptive function

• Why?

1. Physiological systems require integration of multiple levels of organization

   • Atomic and molecular level

   • cellular level

   • tissue level

   • organ level

   • organ system level

   • organism level

All levels need to intergrate to function

2. Organismal structure is fundamentally related to function

   • cellular level

   • tissue level

   • organismal level

3. Feedback mechanisms drives physiology

   • Homeostasis

Sensor - detects stimulus

Integrator - translation of signal in body

Effectors - effect change in body

Negative feedback - response opposes stimulus that triggered response

Positive feedback - response enhances or amplifies the stimulus, leading to an even greater response.

Homeostasis - balance-stability in chemical and physical conditions (regulated by negative feedback)

4. Gradients - super important!

   • Concentration gardients: things move from high → low concentration

5. Proteins are critically important mediators of physiology

6. Evolution by natural selection

   • Variation

   • Heritability

   • Differential survival

Natural selection hypotheses

• Species comes from other, pre-existing species

• Species change through time

Dawrin and Wallace proposed one mechanism for evolution: natural selection

Four Postulates:

• There must be variation among individuals in a population

• At least some variation must be heritable

• Survival and reporductive success are highly variable. Some individuals proce more offspring that survive to reproduce than others do

• Survival and reproductive success are not random: individuals with certain heritable traits are more likely to survive and reproduce in a given environment

7. Adaptation and acclimation are both important, but they’re not the same

Adaptation - evolutionary process

• By evolution by natural selection

• Occurs in population (individuals do not change)

Acclimation - in response to current conditions

• Reversible changes in physiology

• Occurs at individual level

  8. Trade-offs are everywhere

“Cave fish” and “surface fish” are not seperate species

Why have these fish lost their eyes? - Ultimate

How have these fish lost their eyes? - Proximate

How vertebrate animals see:

• Light is focused on retina

• Light sensitive photoreceptors in retina are “excited” by light

• Neurons from retina are “excited” - send signals to brain

• Neurons in brain process info recieved from neurons at retina

Fertilization - egg and sperm produce zygote

• Egg and sperm are “germ cells”

• Zygote is diploid

• Egg: maternal DNA, mitochondria, proteins and RNA, nutrition

• Sperm: paternal DNA, centrosome structure - intiate mitosis

Cleavage - rapid cell division, end product: blastula, hollow fluid-filled ball of cells

• Size of embryo doesn’t change much

Gastrulation - process of cell movements that give rise to the 3 germ layers

• Ectoderm - outer (skin, CNS)

• Mesoderm - middle (bones, muscle, blood vessels)

• Endoderm - inner (digestive organ lining, lungs)

• Body plan and axes also begin to develop during gastrulation

  

Organogenesis - specific tissues and organs arise

• Can occur because gastrulation has formed and positioned germ layers such that cells can signal to one another

4 stages of eye development

1. Neurulation - formation of CNS, occurs during organogenesis

   • Formation of neural tube at end

   • Hollow tube formed from ectoderm becomes CNS (brain, spinal cord)

Part 1: regions of neural tube bein to become specialized

Part 2: optic vesicles form from the neural tube

Part 3: optic cup and lens pit forms

• O.V. contacts with surface ectoderm

Part 4: lens vesicle forms

neural tube → optic vesicle → optic cup → RETINA

surface ectoderm → lens pit → lens vesicle → LENS

Every cell in an organism contains the same DNA sequences

Cell type - a group of cells that exhibit a similar function (Neuron, muscle cell)

Cell lineage - developmental history of a cell or group of cells (ecto-, endo-, mesoderm)

Cell commitment

Uncommited state

• cell can become essentially any cell in adult organism

• possibilities are endless

Commited state

• cell is now specialized

• cell may not look like a specific cell type yet, but it’s commited to a very limited set of potential cell types

Differentiated state

• cell looks like a specific cell type, has associated functions

• unsually irreversible

All possible because of differences in gene expression over time

• Gene expression: production of different proteins

Chromosomes and genes

• Genes: segements of DNA that are expressed to form a functional product → RNA → proteins

mRNA hypothesis - stand of DNA is used as a template to make a complementary strand of RNA

Eukaryots HAVE a nucleus

Prokaryots do NOT HAVE a nucleus

Regulation of transcription and translation

• “Gene expression”

Transcribed region - DNA sequence that is transcribed to producce RNA

Regulatory region - DNA sequences that allow bonding of proteins that control initiation of transcription

• Has to come before transcribed region

Proteins that bind at regulatory regions

• RNA polymerase - produces an RNA strand whose sequence is complementary to the DNA strand

• Transcription factors - proteins that bind to regulatory region and allow trasncription to occur (can turn genes on or off)

*Need both for bind to occur

Binding of transcription factors can be affected by:

• Concentration - how much is present?

• Affinity - high tightly does transcription factor bind to DNA?

Pax6 - an important transcription factor that is required for eye development

• Transcription factors: are proteins, are also regulated by gene expression

Shh - sonic hedgehog

• protein that controls abundance of pax6

• chemical messenger

• “local” secretion (nearby cells)

• binds recpetors - produces an effects (different effects on pax6 depends on Shh concetration)

High concentration Shh → Less Pax6, more Vax1 (negative transcription factor)

Low concentration Shh → More Pax6

• Proximate approach

Shh expression in blind cavefish is higher than in surface fish

What does this mean for pax6 levels in the region where eye structures would normally form? Vax 1 levels? → There would be less pax6 and more vax1 (negative transcription factor)

What does this mean for eye development in cavefish? → Eye development is essentially not occurring because of high levels of vax1

Energy use in animals

1. generation of physical work (movement)

2. maintenence (nervous system regulation, circulation, respiration, digestive system)

3. biosynthesis (tissue growth)

Energy molecules

• carbohydrates (sugars)

• fats

• proteins

Carbohydrates - monosaccharides, disaccharides, polysaccharides

Monosaccharides - glucose, fructose

Disaccharides - sucrose

Polysaccharides - Often long chains of monosaccharides

• Glycogen - string of glucose molecules

  Glycogen → storage form of glucose → stored in muscles and liver

Fats/lipids - trigylcerol/triglyceride

• fat soluble vitamins

• insulation

• long-term energy storage (2x as much energy per weights as carbs

Fat is stored in adipose tissue

• Body fat

• Bone marrow

• Lipid droplets in muscles

Proteins - numerous diverse functions

• can be used directly for energy

• used only when carbs, fats, not available

Sugars, fats, and proteins provide sources of energy for organisms: cells use these to produce ATP

ATP - the “energy currency” of the cell

• adenosine triphosphate

• energy is released following hydrolysis of a phosphate bond

• ATP → ADP

Hydrolysis - breaking and reforming of bonds

Energy metabolism in animals

Antoine Lavoisier - heat produce dby an animal is proportional to O₂ consumed and and CO₂ produced

Energy → maintenence, growth, activity

Food/fuel is oxidized to form ATP

Metabolism - sum of all biological transformations of energy and matter

Metabolic rate - energy metabolism per unit time

Aerobic metabolism

fuel + O2 → CO2 + H2O + ATP + heat

Fuel, O2, CO2, and H2O are INDIRECT measures of metabolic rate

Indirect measures of metabolic rate - O2 consumption or CO2 production

Respirometry - used to measure O2 consumption or CO2 production

• Can be open (open container, uses sensors) or closed (closed container)

Heat is a DIRECT measure of heat production

Direct measure of heat production - “direct calorimetry”

• 335 Joules melts 1g ice

Endothermy - birds and mammals

• relatively high metabolic rate

• body temperature is elevated by metabolically produced heat

• thermoregulate by physiological means

Ectothermy - everything but birds and mammals

• relatively low metabolic rate (not producing enough heat to elevate body temp)

• depend on conditions of environment to elevate or decrease body temp

• thermoregulate behaviorally

Thermoneutralzone - range of temperatures over which MR does not change

Endotherms - basal metabolic rate

• not active

• haven’t just eaten

• know reproductive success

• not thermoregulating (in thermoneutralzone)

Ectotherms - standard metabolic rate

• not active

• haven’t just eaten

• know reproductive success

• report temperature (standard)

Aerobic respiration - series of reactions that harness energy from food and transfer it to ATP

Glucose - the most common form of chemical energy used by organism

• stored in the bonds

In cellular respiration, glucose is oxidized (“burned”) in cells through a series of carefully controlled redox reactions

Oxidation - loss of electrons

Reduction - gain of electrons

Redox reactions - energy transfer via transfer of electrons

Important electron carriers

1. FAD → FADH2 → electron carrier

2. NAD+ → NADH → electron carrier

Cellular respiration - 4 phases

1. glycolisis - takes place in the cytoplasm

   • “splitting glucose”

2. pyruvate processing - takes place in the mitochondria

3. citric acid cycle - takes place in the mitochondria

   • also called the krebs cycle

4. electron transport chain - takes place in the mitochondria

   • oxidative phosphorylation

Stage 1: glycolysis

• glucose is split into 2 3-c pyruvates

• energy transferred to NADH, ATP

Stage 2: pyruvate processing

• those 2 3-c pyruvates → produce 2 2-c acetyl CoA and 2 CO2

• energy transfers: NADH is formed

Stage 3: citric acid cycle

• the 2- 2c acetyl CoA molecules form 4 CO2 molecules

• energy transfer: 6 NADH, 2 FADH2, 2 ATP

Stage 4: electron transport chain

• oxygen is the final electron acceptor → H2O formed

• H+ gradient (proton gradient)

• H+ move from inner membrane back out through ATP synthase range → 25-29 (driven by H+ gradient)

• ADP + P → ATP

Anaerobic ATP production - fermentation

• lactic acid fermentation occurs in humans

• some ATP produced

• byproducts produced: lactate

• occurs only in the cytoplasm

Overview of cellular respiration: glucose is not the only possible input!

Rely on fats and carbohydrates during exercise

• carbohydrate metabolism is more efficient during high intensity exercise → human body favors carbohydrate metabolism during high intensity exercise

Maximal oxygen uptake (VO2 max) - maximum rate of O2 uptake/use during activity

• measured in mLO2/kg/min

• an activity’s intensity is often determined by what % of VO2 max it demands

As intensity of an aerobic activity increases, reliance on glucose for cellular respiration increase

There are glycogen stores in liver and muscle

• you can also ingest carbohydrates

Sled dogs have a VERY high VO2 max

• more muscle than humans

• with training and high fat diet, they have increased numbers of mitochondria

Sled dog diet - 50% fat, 35% protein, 15% carbohydrates

If sled dogs are fed higher carbohydrates:

• Intense muscle cramping

• blood sugar drops

• muscle glycogen is depleted

If sled dogs are fed higher protein and fat:

• lower injury incidence

How do sled dogs fuel their activity on such a low carb diet?

• their muscle glycogen increases over course of race (when on a low carbohydrate diet)

• shift towards carbohydrate metabolism

• change in hormonal profiles that allows for glucose production by liver

  1. increase in glycogen breakdown in liver → elevates blood glucose

  2. increase gluconeogenesis in liver

gluconeogenesis - make glucose from non-carb molecules (fats, proteins)

How do they stay in the thermoneutralzone?

Challenge #1: not losing heat to the cold environment

• Solutions: highly insulative fur coat

Why don’t they lose heat from legs/feet? → special arrangement of blood vessels that keeps feet cold

• lose less heat to the environment (keep core warm)

Challenge #2: not overheating during activity

• Solutions: low body fat, insulative fur coat

What is mad honey and why is it dangerous?

2 systems of chemical regulators used for communication within the body:

Endocrine system

• secretes hormones

• signals can be “broadcast” to all cells via blood supply

• chemical communication

Nervous system

• “point to point” communication

• chemical, electrical signals

Organization of the nervous system

• cephalization

• segmental organization

• centralization

Central nervous system (CNS) - brain and spinal cord

Peripheral nervous system (PNS) - everything else

Neural tissue: 2 cell types

Neurons

• structural, functional units of the nervous system

• transmit electrochemical signals

Neuroglia (glial cells)

• support: insulate, nourish, etc.

Anatomy of a neuron

Many neurons also have dendritic spines - increase surface area of dendrites

Neurons send signals across synapses

• Synapses - gap between one neuron and another neuron/cell

Communication across synapses

• chemical

• electrical

Classifying by structure

1. Total number of neurites (axons and dendrites) that extend from cell body

   • lots of neurites → multipolar

   • 2 neurites → bipolar

   • 1 neurite → unipolar

2. Anatomy of dendrites

   • spiny vs not spiny

3. Axon length

Classifying by gene expression

1. neurotransmitter type

   • chemical released into synapse

Classifying by function

1. Sensory neurons

   • carry information to central nervous system

2. Motor neurons

   • carrying information from central nervous system to “effectors” (muscles)

3. Interneurons

   • associate information from sensory and motor neurons → located entirely in central nervous system

Neurons - the resting membrane

The cell membrane: barrier and gatekeeper

Phospholipid bilayer

• phosphate - containing head (polar - can dissolve in water, “hydrophillic”)

• Tails: lipids (non-polar, “hydrophobic”)

Cytosol and extracellular fluid - fluid inside and outside of the cell

Ions - atom or molecule with a net electrical charge (positive or negative)

• Na+ + Cl- → NaCl

Phospholipid bilayer allows intracellular fluid to maintain different concentration of ions that extracellular fluid

Cations - positively charged ions

• Na+, K+, Ca2+

Anions - negatively charged ions

• Cl-

The cell membrane barrier and gatekeeper

Proteins embedded in membrane - some allow substances to cross (in or out)

• Channels - always open or gated

• Transport proteins

• Pumps - move ions against concentration gradient

• Receptors

• Glycoproteins

Ion channels

• selective for specific ions (can be always open or gated)

1. concentration gradient

Diffusion - movement from area of higher to lower concentration

2. electrical gradient (charge matters)

   • “electrical potential”

Voltage also known as “electrical potential”

Two gradients at work simultaneously

• concentration gradient

• electrical gradient

Cell membranes are polarized

• unequal distribution of ions

• “inside negative”

In an unstimulated neuron, membrane potential = “resting potential”

• average: -65 mV

What factors contribute to resting potential?

The primary players

1. charge - carrying ions/molecules

   • sodium (Na+)

   • potassium (K+)

   • organic anions (A-)

   • proteins also have a negative charge

2. membrane proteins

   • Na+/K+ ATPase pumps

   • open K+ channels (“leak channels”)

K+ and A- more concentrated on inside

Na+ and Cl- more concentrated on outside

Distribution established and maintained by ion pumps

What contributes to resting membrane potential of the neuronal membrane?

1. sodium-potassium ATPase pumps produce and maintain K+ and Na+ gradients across the membrane (high K+ in, high Na+ out)

2. at rest, neuronal membrane is highly permeable to K+ due to presence of potassium “leak” channels (permeability is 40x higher than it is to Na+)

3. movement of K+ ions through these channels (out, along concentration gradient) leaves inside of membrane charged negatively relatively to outside

• 3 Na+ IN, 2 K+ OUT

• At rest, -65 mV

Na+ moves inside cell

• membrane potential is LESS negative - depolarizes

K+ moves outside cell

• membrane potential is MORE negative - hyper-polarizes

Membrane potentials can change → graded potentials

Graded potentials - changes in membrane potential that vary in amplitude and duration

Voltage-gated ion channels drive action potential

Membrane potentials can change: excitable membranes (neurons) produce action potentials

All-or-none response - a brief, all-or-none change in membrane potential

• threshold potential ~ -55 mV

Depolarization - Na+ channels open

Hyperpolarization - K+ channels open

What makes neuronal membranes “excitable”?

Voltage-gated Na+ channels & voltage-gated K+ channels → open in response to a change in membrane potential (voltage)

• -55 mV threshold

• Depolarizing signal is required

Voltage-gated sodium channels

1. at rest

2. channel opens, Na+ moves into cell (threshold) open ~ 1 msec

3. inactivates - Na+ cannot move through - remains inactive for few msec (“refractory period”)

4. channel closes - no longer inactivated - happens when membrane returns to resting potential (“deinactivation”)

Voltage-gated potassium channels

• open in response to depolarization of membrane (but with a ~1 msec delay)

• slows to close

Remember: “nerve impulses” are waves of action potentials

Blood sugar on the rise: what is diabetes melitus and why is it a major public health concern?

1. Chemical messengers and the endocrine system

General categories of chemical messengers (short distances)

Autocrine secretion - chemical messenger affects cell that secreted it (extra local)

Paracrine secretion - chemical messenger secreted by one cell and affects nearby cells

• Shh

Neurotransmitters - chemical messenger secreted by neurons at synapses

“Endocrine” secretions travel through the blood to affects distant cells

Endocrine secretion - “hormone”

• secreted into blood, affects distance cells

• long distance messengers

Neuroendocrine secretion - “neurohormone”

• neuron secretes chemical messenger into blood

• affects distant cell

2. Hormones and receptors

A focus on endocrine secretions: general features

1. gland - ductless, rich blood supply

2. hormone - secreted into the blood

3. transport - reaches every cell in the body

   • does not mean all cells are affected

4. target cell - only cells affected by hormones

3 main chemical types of hormones:

Peptide/polypeptide/”protein hormones”

• made via gene expression transcription-translation

• strings of amino acids

• most abundant type

• example: insulin, growth hormone, secretion

• tend to be species specific

Amino acid derivatives/modified amino acids

Made from enzymatic modifications of a single amino acid

• example: epinephrine, norepinephrine, melatonin

• not species specific

• enzymes made out of proteins

Steroid hormones

• made by enzymatic modification of cholesterol

• 5 classes

• example: testosterone, estrogen, progesterone

• not species specific

Hormone must interact with a receptor to exert an effect

Receptors are specific

2 general classes of receptors

Intracellular - hormone-receptor complex acts as a gene transcription factor

• changes in cell are slower

Membrane bound - signal transduction (signal amplification)

• hormone never enters cell

Membrane receptor activation leads to rapid changes in cells

Intracellular receptors: bind hormones that can cross the membrane (lipid-soluble hormones)

Mechanism of action - how receptor works to effect change in cell

Peptides and polypeptides - cannot cross membrane

• not lipid soluble

Amino acid derivatives - most cannot cross membrane

• not lipid soluble

Steroids - can cross

• lipid soluble

Glucose homeostasis

Glucose - if too low = hypoglycemic → not enough fuel to produce ATP

• if glucose is too high = hyperglycemic → high glucose levels are toxic to neurons and blood vessels

Insulin and glucagon: 2 pancreatic hormones that are important in maintaining glucose homeostasis

human body → pancreas → islet of langerhans → alpha cell (glucagon) & beta cell (insulin)

Pancreas is an…

endocrine organ - secretes hormones

• not through ducts

exocrine organ - secretes digestive enzymes

• through ducts

Glucose transporters (GLUT transporters)

Membrane proteins that allow glucose to cross membrane

• Facilitated diffusion - diffusion of substance across membrane with assistance of protein transporter/channel

1. Some are not regulated: always present in membrane

   (no special signal required to insert in membrane)

   • GLUT 1 - most cells in the body

   • GLUT 2 - abundant in liver cells

   • GLUT 3 - abundant in CNS

2. Others are regulated: they require a signal to be inserted in the membrane

   • GLUT 4 - skeletal muscle cells, adipose (fat) cells

     • pool of vesicles inside of cell containing GLUT 4 transporters

     • insulin binds receptor

       • stimulates insertion of GLUT 4 transporter into membrane

GLUT 4 is insulin regulated

Insulin stimulates uptake of glucose by cells

Insulin has important actions in liver, adipose, and skeletal muscle tissue

Insulin action on liver cells

• Glucose uptake occurs through GLUT 2 transporters (non-insulin regulated)

• Insulin binds receptors on liver cells - signal transduction cascade stimulates glycogenesis (formation of glycogen)

• Glucose is also metabolized here to produce ATP

Insulin action on skeletal muscle cells

• most abundant glucose transporter: GLUT 4 (insulin-dependent)

• insulin stimulates insertion of GLUT 4 into membrane

• glucose → ATP

• other actions of insulin in muscle cells:

  • glycogenesis (formation of glycogen)

  • amino acid uptake into muscle cells

  • protein synthesis

Insulin action on adipose tissue

• insulin binding to receptor stimulates insertion of GLUT 4 transporters into membrane

• insulin also stimulates:

  • formation of glycerol

  • uptake of fatty acids

  • (tri-glyceride production)

Diabetes melitus is a disorder of glucose regulation

Type 1 diabetes - individual does not secrete sufficient insulin to stay in glucose homeostasis

• beta cells of pancreas attacked/destroyed by immune system

  • no insulin

• autoimmune

Type 2 diabetes - target cells don’t respond properly to insulin

• receptor issue

• diabetes epidemic

• origins: lifestyle factors (diet, exercise) and genetic predispositions

Type 2 diabetes: risk factors

• obesity

• high sugar diet

• lack of exercise

• metabolic syndrome

Consequences of chronic hyperglycemia

1. macrovascular complications (effects on arteries)

   • glycosylation - glucose binds to proteins in blood

   • atherosclerosis - thickening, hardening of arteries due to build up of plaques

   • Can cause: heart attack, stroke, coronary artery disease, peripheral artery disease (extremities don’t get enough blood supply)

2. Microvascular complications (problems with capillaries)

   • diabetic nephropathy (kidney disease)

   • diabetic retinopathy (retina disease)

   • damage to capillaries in kidneys - problems with filtration

   • vision problems due to damage to capillaries at retina

3. Neuropathy (problesm with neurons)

   • diabetic neuropathy (nerve damage)

   • loss of sensation

   • greater likelihood of injuries that may be unnoticed

Most common treatment approaches

Pharmaceuticals - drugs that attempt to mitigate certain aspects of disease

• increase cellular responsiveness to insulin

• increase insulin production

• example: metformin, GLP-1 agonists, sulfonoureas

Lifestyle changes - diet and exercise

GLUT 4 is abudant in skeletal muscle tissue

• GLUT 4 is regulated by insulin and muscular contraction

How can antarctic icefish survive without red blood cells?

What is blood useful for?

• gas transport (O2, CO2) → red blood cells are good for this

• fighting infections, coagulation/clotting

• transporting wastes

• transporting hormones

• transport of heat

• transport of nutrients

Important blood gases

Cellular respiration:

glucose + oxygen → carbon dioxide + water + ATP + heat

• Whether you are a human or a fish, gas exchange occurs at the respiratory surface

• Respiratory surface can be characterized by:

  • thin membrane

  • lots of capillaries

  • allows for efficient gas exchange

Gases diffusing across membranes

• based on concentration gradients

Red blood cells and respiratory pigments

Hematocrit = 45

Blood can carry WAY MORE O2 than what is simply dissolved

Hemoglobin (Hb) - respiratory pigment

• binds O2 reversibly

• 4 subunits

• protein portion - “globin”

• heme portion - iron - containing

• each subunit can bind 1 O2

• cooperative binding: when 1 O2 binds, Hb has a conformational change that increases likelihood of more O2 binding

O2 dissolves into blood plasma → 1.5%

Enters red blood cell, binds to Hb → 98.5%

(now it is taken out of solution→ not contributing to concentration)

Hb binds oxygen reversibly

Hb + O2 ⇌ HbO2 (oxyhemoglobin)

When O2 concentration is high:

→ at lung/gill capillaries

When O2 concentration is low:

← at systemic tissue (everything but lungs/gills) capillaries

The amount of O2 bound to Hb depends on how much O2 is dissolved in the blood plasma → concentration of dissolved O2 in blood plasma → partial pressure of O2 = P_o2

Hemoglobin-O2 equilibrium curves: describe saturation of Hb at different Po2

“Sigmoid curve”

• when 1 O2 binds to Hb, the other 3 binding sites bind O2 more readily (comformational change)

Where in body is PO2 low? - anywhere in the body

Where in body is PO2 high? - respiratory surface and lungs

General principle: tradeoffs

Between

• loading of O2 onto Hb at respiratory surface

• unloading of O2 from Hb at systemic tissues

  • “delivery”

Hb’s affinity for O2 tells us which one is favored

• Affinity: the ease with which Hb will bind O2 when it encounters O2

High affinity - readily binds O2, even when there’s not much available - favors loading

• Saturated at low PO2

Low affinity - binds O2 less readily, becomes saturated only when there’s a lot of O2 available - favors delivery

• saturated at high PO2

P₅₀ is a measure of O2 affinity

• P50 is the PO2 at which Hb is 50% saturated with O2

Higher affinity respiratory pigment has a lower P50 value

Myoglobin (Mb)

Single subunit

• globin portion (protein)

• heme unit (Fe-containing)

• very high affinity for O2 (small P50)

• only found in muscle cells

  • skeletal and cardiac muscle

What is the function of myoglobin? - O2 “reserve” storage for muscles - holds onto O2, gives it up only when concentration drops very low

• Some icefish also lack myoglobin

Closed systems: hearts

• atria (plural)

• ventricles

Closed systems: blood vessels

Capillaries - small and extremely thin walled

• exchange occurs here

Arteries - very thick walled

Fish hearts: 2 chambers

• single ventricle

• single atrium

• low blood pressure

• only pump deoxygenated blood

Heart action:

Cardiac output - volume pumped per unit time

• CO = HR x SV

3 questions to consider:

1. How did icefish lose the ability to produce Hb? DNA → mRNA → protein (Loss of genes themselves)

   • partial a-globin gene, no B-globin gene

2. When did loss of Hb genes occur in icefish evolution?

   • 5.5 - 2 million years ago

   • happened one time in ancestor common to icefish

   • Synapomorphy = shared derived trait

3. If not advantageous, why did this condition persist?

   • cold H2O - higher O2 content

   • well aerated - higher O2 content

   • cold H2O lower the metabolic rate of icefish (lower O2 demand)

   • lack of competition

     • many species lacked sufficient antifreeze protein production, disappeared when ocean cooled

Hb loss = sublethal trait

• only disadvantageous in the context of competition

Compared to red-blooded fishes, icefish have a low thermal tolerance

Can coconut water be used in place of IV fluids?

Body fluid compartments - intracellular fluid and extracellular fluid

• Intracellular fluid (ICF) - fluid inside of cells

  • most of water in body is intracellular fluid

• Extracellular fluid (ECF) - fluid outside of cells

  • Interstitial fluid: between cells

  • Blood plasma

Transport across membrane - active or passive

• Active - uses ATP

  • Protein mediated

• Passive - no ATP required

  • Protein mediated (facilitated diffusion)

  • Simple diffusion across membrane

Protein mediated - active or passive

• Active

  • Primary active transport: Na+/K+ ATPas pump

  • Secondary active transport

• Passive

  • Facilitated diffusion: transporters, channels, aquaporins

Aquaporins - membrane channels that allow water to move through (facilitated diffusion)

Diffusion across a semipermeable membrane establishes equillibrium

• ions move along their own gradient with a permeable membrane

Solute - dissolved particles in solution

Water with move from area of lower solute concentration to a higher solute concentration

Osmosis - diffusion of water across a semipermeable membrane

• depends on solute concentrations

Fluid outside → higher concentration of solute

• water moves OUT

  • cell shrinks

Fluid outside → lower concentration of solute

• water moves IN

  • cell swells

Fluid outside → equal concentration of solute

• no NET movement

  • no net change

Osmolarity: concentration of solutes in solution - mOsm

Osmolarity vs. molarity

150 mM sucrose = 150 mOsm solute

150 mM NaCl = 300 mOsm NaCl

Hyperosmotic: solution has greater concentration of solutes

Hyposmotic: solution has lower concentration of solutes

Isosmotic: solution has equal concentration of solutes

Oceans: 3.5% NaCl

Freshwater: <0.5% NaCl

Estuaries: Variable NaCl

Osmoregulators vs osmoconformers

Osmoregulators - regulate internal osmolarity within a narrow range, despite difference sin environmental osmolarity

Osmoconformer - internal osmolarity matches environmental osmolarity

Freshwater fish - hyperosmotic regulator

• Challenges: H2O gain, salt loss

  • Solutions: produce lots of dillute urine, active uptake of salts

Saltwater fish - hyposmotic regulator

• Challenges: H2O loss, salt gain

  • Solutions: produce little urine - more concentrated than freshwater fish, active transport of salts out of body

Desication/dehydration - osmoregulator in terrestrial environment

• change activity levels (reduce H2O loss via evaporation)

• drink H2O (eat food with high H2O content)

• metabolish H2O production

• produce concentrated urine (mammals, birds, insects)

• insects have waxy body coverings (reduce H2O loss from body)

• reduce H2O loss in urine