BIOL1030 MIDTERM

what are some examples of varying response to environmental change?

skin temperature, breathing rate, heart rate, sweating, heat production

define homeostasis

maintenance of a stable internal environment

what are the three essential control system components?

1. sensors (receptors for temp, ph, touch)

2. effectors (muscles, sweat glands)

3. response (shivering, sweating)

how does a negative feedback loop work?

help maintain stability by counteracting deviations from a set point, such as a thermostat

what are the two environmental change categories?

conformers - do not maintain homeostasis regulators - maintain homeostasis

what are the four characteristics of membranes?

1. separate the inside of the cell from the outside

2. surround many internal structures

3. composed of lipids, proteins, carbs

4. two phospholipid layers which arrange themselves spontaneously

what are the four characteristics of plasma membrane?

1. feature of all cells

2. defines the cell boundary

3. separates internal contents from surrounding environment

4. critical for homeostasis

what's the difference between saturated and unsaturated fatty acids?

saturated fatty acid - chains lack double bonds, phospholipids with a straight structure that favor tight packing

unsaturated fatty acid - one or more double bonds that introduce kinks in phospholipids, reducing tightness

what does membrane fluidity depend on?

phospholipid composition (bonds and the length of the tails)

how does membrane selectivity work?

certain items can move freely, some only under certain conditions, some not at all

reasons for limited permeability?

• lipid bilayer is hydrophobic, preventing ion movement

• many macromolecules ae too large (gasses, lipids, polar molecules can cross)

• key to maintain homeostasis

explain simple diffusion/passive transport

net movement of solute from the area of higher solute concentration to the area of lower solute concentration (random motion in both directions)

explain osmosis

diffusion of water through the membrane (not solute)

what are aquaporins?

protein channels allowing for facilitated diffusion of water

what occurs in primary active transport?

ATP is directly used to move molecules against their concentration gradient

explain the sodium-potassium pump in primary AT

1. three sodium ions are pumped out of the cell against their concentration gradient

2. two potassium ions are pumped into the cell against their concentration gradient

what are the two carrier proteins involved in secondary active transport?

antiporter - transports solutes/ions in opposite directions symporter - transports solutes/ions in same direction

what occurs in secondary active transport?

1. protons are pumped across the membrane by primary AT

2. the proton pump generates an electrochemical gradient (higher proton concentration outside the cell, lower proton concentration inside the cell)

3. antiporter uses said gradient to move a different molecule out of the cell against its concentration gradient

what are the three water balances of a cell?

hypertonic (shrunk) - water out, solute concentration lower

isotonic (normal) - water equal, solute concentration equal

hypotonic (lysed) - water in, solute concentration higher

what two systems maintain homeostasis?

endocrine and nervous systems

how does the endocrine system influence cells?

ductless glands release hormones into bloodstream capillaries which circulate throughout the body and exert influence on target cells which possess receptor molecules (response is slow and widespread)

how does the nervous system influence cells?

neuron stimulation is received by dendrites, an action potential is triggered at the axon, leading to the release of neurotransmitters which bind with the target receptor to create a new signal in the postsynaptic neuron (response is fast and targeted)

what is the neuron resting membrane potential?

when no signal is present there are more negative ions inside the cell, so the inside is negatively charged relative to the outside, aka polarized

why is the neuron resting membrane polarized?

positive potassium channels allow potassium ions to leak out of the cell, causing a buildup of positive ions outside the cell

why does depolarization occur?

the neuron becomes excited, more sodium ions diffuse into the cell, creating a positive charge

where does depolarization occur?

axon hillock

what is the refractory period?

the period during which the inside membrane voltage falls below, and then returns to the resting potential

why cant a neuron fire a second action potential during the refractory period?

1. voltage-gated Na channels are closed/inactive

2. voltage-gated K channels are open

how do action potentials travel?

propagate along the axon by sequentially opening and closing adjacent voltage-gated Na and K channels

what occurs in saltatory propagation?

action potentials jump from node to node due to the layers of myelin insulating the axon, the speed of conduction is increased

charge wise, what occurs at nodes of ranvier?

buildup of positive charges inside and negative charges outside

what occurs when neurotransmitters bind to post-synaptic cells?

the opening of ion channels, generating post-synaptic potential (grading potential)

potential in depolarized cell vs hyperpolarized cell

depolarized - potential is excitatory (EPSP), ligand-gated Na channels open

hyperpolarized - potential is inhibitory (IPSP), ligand-gated Cl or K channels open

sensory transduction

stimulus is converted into an electrical impulse (conversion of physical or chemical stimuli into nerve receptors)

provide an example of sensory transduction

receptors located in the ear convert the energy of sound waves into nerve impulses that allow animals to hear

how do simple multicellular animals exchange compounds with the environment?

diffusion

how do larger animals exchange compounds with the environment?

diffusion and bulk flow for gas exchange

what are the two steps of bulk flow?

1. ventilation (movement of medium over respiratory surface)

2. circulation (movement of body fluids containing dissolved gases, this requires pumps)

what is the goal of gas transport?

to deliver oxygen to mitochondria

what is the goal of ventilation?

to reduce formation of static boundary layers

what occurs during active ventilation?

animal creates ventilatory currents that flow across gas exchange surface using suction or positive pressure, expanding metabolic energy

what occurs during passive ventilation?

environmental air or water currents induce flow to and from the gas exchange membrane, no use of metabolic energy

what do chemoreceptors detect?

brainstem - CO2 and H

carotid and aortic - O2 and H

how does the stimulus in chemoreceptors work?

as activity rises, so do CO2 and H levels, while blood O2 levels fall

how does the sensor in chemoreceptors work?

if CO2 is too high, chemoreceptors in brainstem stimulate respiratory muscles

how does the effector in chemoreceptors work?

diaphragm and other respiratory muscles contract more frequently and more strongly

how does the response in chemoreceptors work?

blood CO2 and blood H levels fall, blood O2 levels rise

how do circulatory systems move fluids?

by increasing the pressure of fluid in one part of the body, fluid flows down the body and down the pressure gradient

what are the three components needed for circulatory systems to move fluid?

1. fluid that circulates through the system

2. system of tubes, channels, or spaces

3. pump or positive structures

what is hematocrit percentage?

fraction of blood made up by red blood cells which affects resistance

what is hemoglobin?

a globular protein consisting of four subunits (each subunit surrounds a heme group which contains iron)

what occurs during open circulation?

blood flows through a vessel with muscular thickenings that act as a pump, blood empties into an open body cavity to supply the tissues with nutrients

what occurs during closed circulation?

blood flows through connected blood vessels, pumped by the muscular hearts to supply the tissues with nutrients

what occurs during single circuit circulation (fish)?

deoxygenated blood enters the atrium from a main vein and then the ventricle, same blood is pumped from the ventricle into a main artery

what occurs during double circuit circulation (land vertebrate)?

hearts evolved with over two chambers which separate circulation to the gas exchange organs from circulation to the body tissues (separated into pulmonary and systemic circuits)

what are the advantages of double circuit circulation?

1. increased supply of oxygenated blood to tissues (pumped at high pressure)

2. increased uptake of O2 at gas exchange surface (due to lower pressure and more time for extraction)

blood flow through the heart

S&IVC --> RAT --> RAV --> RV --> PV --> PA --> (becomes O2) --> LAT --> LAV --> LV --> AOV --> systemic circulation

how do cardiac muscle cells differ from skeletal muscle cells?

1. specialized cardiac cells generate action potentials on their own (pacemaker, SA and AV nodes)

2. electrically coupled via gap junctions which transmit electrical signals

what is a pacemaker?

sinoatrial node, small group of specialized cells in the RA that generates electrical impulses, causing the heart to beat in a regular rhythm

what occurs during depolarization in the pacemaker?

1. SA pacemaker cells generate action potentials which spread through the atria and contract

2. signals from SA pacemaker reach the AV node which activates and fires

3. APs are transmitted through a set of modified muscle fibers, depolarization spreads from said fibers through the entire ventricle which then contracts

what is a metabolic rate?

the overall rate of energy used by an organism, affected by activity level, body size and temperature

what is the thermal strategy?

combination of behavioral, biochemical, and physiological responses that ensure body temperature is within an acceptable limit

source of heat for endotherms vs ectotherms

endotherm - generate internal heat to maintain temp

ectotherm - environment determines temp

what are the two responses to environmental temperature change?

homeotherm - stable body temp (balance heat gain/loss)

poikilotherm - variable body temp

what behavioral mechanisms are common for maintaining optimal temperature?

orienting toward or away from the sun, seeking shelter or breezes

high vs normal/cool body temp heat exchange

normal/cool - constriction of arterioles reduces blood flow to skin surface

high - decrease in arteriole constriction, vessels dilate, blood is directed to skins surface

how do endotherms use shivering thermogenesis for heat production?

skeletal muscles pull against each other, ATP is converted to ADP (heat is released)

what are the heat conservation adaptations in endotherms?

1. large body size

2. reduced extremities

3. insulation (feathers and fur)

how do endotherms avoid overheating?

1. evaporative cooling (sweating)

2. direct contact with water

3. panting

4. heat windows (rabbit ears)

what are the advantages of ectotherms?

1. lower metabolic rate

2. expend little effort on thermoregulation

3. invest in growth and reproduction

4. less time foraging

what are the disadvantages of ectotherms?

1. limited ability to regulate body temp

2. limited activity (duration and seasons)

3. limited geographic distribution

4. limited bursts of high activity

negative feedback regulation of body temp

stimulus - cold sensor - hypothalamus effector - muscles (shivering) response - heat

what are the three types of muscle?

skeletal, cardiac, smooth

striated vs smooth muscle

striated - appears striped, actin and myosin arranged in a regularly repeating pattern smooth - appear uniform, actin and myosin arranged in irregular pattern

what is the skeletal muscle organization path?

belly --> bundle --> fiber --> myofibril

what do myofibrils contain?

thin (actin) filaments, thick (myosin) filaments

sarcomere

contractile unit of muscle defined as the region between two Z discs

how does titin function?

like a spring, prevents overstretching

how do myosin and actin function?

actin and myosin slide/overlap one another, causing muscle fibers/cells to shorten and produce force

what occurs during muscle shortening?

1. myosin head binds ATP, leading to detachment from actin

2. myosin head catalyzes ATP hydrolysis, forming ADP and Pi, myosin head cocks back

3. myosin heads bind to actin at specific sites to form cross-bridges

4. ADP and Pi are released, producing a power stroke that generates force, causing the thin filament to slide relative to the thick filament and the sarcomere to shorten

what is necessary for cross-bridges to form?

myosin binding sites on actin must be exposed (Ca must bind to troponin to cause movement of tropomyosin)

how are skeletal muscle fibers activated?

impulses transmitted by motor nerves to the skeletal muscle cell at the fibers motor endplate

excitation-contraction coupling

depolarization (excitation) leads to shortening (contraction)

why does depolarization spike in a vertebrate muscle cell?

the binding of neurotransmitter to receptors on a vertebrate muscle cell causes an influx of sodium ions, causing a spike in depolarization

what are the three types of muscle contractions?

concentric, eccentric, isometric shortening, lengthening, staying the same

what does muscle force depend on?

1. stimulation frequency

2. the number of motor units activated

what is necessary for twitch contraction to occur?

Ca must be released from the sarcoplasmic reticulum then pumped back in

what is tetanus?

the highest tension developed by a muscle in response to stimulation of increasing frequency

motor unit

a motor neuron and the population of muscle fibers it innervates

fast twitch skeletal muscle

1. large glycolytic (white) fibers, stained light yellow

2. energy supplied by anaerobic glycolysis

3. few mitochondria, capillaries, or myoglobin

4. develop force rapidly, fatigue quickly

slow twitch skeletal muscle

1. oxidative (red) fibers, stained red

2. aerobic respiration and oxidative phosphorylation

3. well supplied mitochondria, surrounded by capillaries, abundant myoglobin

4. develop force slowly, fatigue resisted

myoglobin

red muscle oxygen storage molecule