BILD 2 Final All Untested LOs

What are the differences between asexual & sexual reproduction?

• Asexual reproduction

  • Occurs without the fusion of gametes

  • Doesn’t involve the exchange of genetic information

  • Offspring are genetically identical to parent

• Sexual reproduction

  • Occurs through the fusion of gametes (fertilization)

  • Offspring are genetically unique

How do the environment, sex chromosomes, sex-determination genes, & hormone levels contribute to sex determination?

• Environment

  • In some species, environmental conditions determine sex

  • Temperature during embryonic development can determine whether offspring develops as male or female

• Sex chromosomes

  • XX is female (in humans)

  • XY is male (in humans)

• Sex determination genes

  • SRY gene on the Y chromosome

  • If SRY gene is present:

    • Gonads develop into testes

    • Testes produce testosterone

    • Male reproductive anatomy develops

  • If SRY gene is absent:

    • Gonads develop into ovaries

    • Higher estrogen/progesterone levels dominate

    • Female reproductive anatomy develops

• Hormone levels

  • High testosterone levels promote the development of male internal/external reproductive structures

  • High estrogen & progesterone levels promote the development of female reproductive structures

How do changes in levels of blood sugar, insulin, or glucagon affect the homeostatic control of blood glucose levels?

• Increase in insulin levels

  • Blood glucose levels decrease

  • Glucose uptake by cells increases

  • Glycogen formation increases

• Decrease in insulin levels

  • Blood glucose levels remain elevated

  • Cells take in less glucose

• Increase in glucagon levels

  • Increase in blood glucose levels

  • Increase in glycogen breakdown in the liver

  • More glucose released into the blood

• Decrease in glucagon levels

  • Reduced ability to raise blood sugar during fasting

  • Risk of low blood sugar

How would changes in neurotransmitter release, receptor activity, or neurotransmitter clearance from the synapse affect signaling between neurons & their targets?

• Increase in neurotransmitter release → Increased signaling because more neurotransmitter binds receptors

• Decrease in neurotransmitter release → Decreased signaling because fewer receptors are activated

• Increased receptor activity → Stronger signaling response

• Decrease receptor activity → Weaker signaling response

• Faster neurotransmitter clearance → Decreased signaling because neurotransmitter spends less time in the synapse

• Slower neurotransmitter clearance → Prolonged or increased signaling because neurotransmitter remains in the synapse longer

What are the two ways the hypothalamus & pituitary gland work together to release hormones?

• Anterior pituitary pathway: Hypothalamus releases hormones into blood vessels that travel to the anterior pituitary → Stimulates or inhibits the release of anterior pituitary hormones

• Posterior pituitary pathway: Hypothalamus directly produces hormones → Hormones travel down axons of hypothalamic neurons to the posterior pituitary → Hormones are stored in the posterior pituitary & released into the bloodstream

What are the two methods of long-distance communication in animals? What are their differences?

• Endocrine system

  • Uses hormones

  • Endocrine glands secrete hormones into surrounding fluid, including blood

  • Targets cells throughout the body because all cells have a blood supply

  • Reaches target cells more slowly

  • Effects tend to last longer

• Nervous system

  • Uses signaling by nerve cells (neurons)

  • Signals are electrical or chemicals carried through extracellular fluid

  • Targets neurons, muscles, & some glands only

  • Reaches target cells more quickly because electrical signals are quicker than chemical signals

  • Effects tend to last a shorter amount of time

What are the different types of glia? What are their functions? Where are they found?

• Central nervous system

  • Oligodendrocytes

    • Insulate neurons with myelin

    • Can myelinate multiple neurons at once

  • Astrocytes

    • Main support cells for the brain

    • Transport nutrients from the blood to neurons

    • Balance ionic & chemical environment

    • Involved in care & maintenance of the brain, like healing

  • Microglia

    • “White blood cells” of the brain

    • Fight micro-organisms

    • Scavenge & clean up debris

• Peripheral nervous system

  • Schwann cells

    • Insulate cells of the PNS with myelin

How does the flow of ions during the action potential change the voltage inside the cell?

• Na⁺ flowing in will make the cell more positive

• K⁺ flowing out will make the cell more negative

What do the terms depolarization & hyperpolarization mean?

• Depolarization: Membrane potential gets more positive (less negative)

• Hyperpolarization: Membrane potential gets more negative (less positive)

How does an action potential occur?

1.) A neuron is at resting potential, then is stimulated, causing it’s membrane potential to rise above threshold

2.) Rising Phase: When a neuron reaches threshold, all voltage-gated sodium channels open & sodium flows into the cell due to the concentration gradient

3.) Peak: Right when the rising phase changes to the falling phase; Na⁺ channels inactivate due to time, meaning the sodium ions stop passing through even though the voltage is above threshold; Voltage-gated K⁺ channels open due to the voltage reaching threshold, they are just slow to respond

4.) Falling Phase: Because the K⁺ channels have just opened, K⁺ flows out of the cell, causing hyperpolarization; Because Na⁺ channels have just become inactive, Na⁺ stops flowing in & stops depolarization

5.) Undershoot Phase: So much K⁺ leaves the cell that the membrane potential sometimes hyperpolarizes below the resting potential; Then, the K⁺ channels close, the Na⁺ channels go back to rest, & the cell returns to resting membrane potential; The neuron can now make another action potential & Na⁺/K⁺ pumps restore ion concentrations

How does the synapse function?

1.) High voltage causes voltage-gated Ca²⁺ channels to open → Ca²⁺ enters the cell

2.) Ca²⁺ causes vesicles to fuse with the membrane → That fusion releases neurotransmitters into the synapse

3.) Neurotransmitter binding causes the receptor to have an effect in the receiving cell

What causes neurotransmitter signaling to stop?

• Diffusion away from the synapse

• Reuptake into the presynaptic terminal

• Enzymatic degradation

What happens to the graph of voltage vs. time of an action potential if Na⁺ channels are blocked?

• You do not get an action potential

• No sharp rising phase

• At most a small subthreshold bump, but not enough to stimulate an action potential

• Because rising phase depends on Na⁺ influx

What happens to the graph of voltage vs. time of an action potential if the function of Na⁺ channels is reduced?

• Harder to reach threshold

• If it fires, the peak may be reduced or the action potential may fail to fully develop

What happens to the graph of voltage vs. time of an action potential if Na⁺ channels fail to inactivate?

• The action potential stays depolarized longer

• Repolarization is delayed

• Neuron may be prone to repeated firing/seizures

What happens to the graph of voltage vs. time of an action potential if K⁺ channels are blocked?

• Falling phase is slower

  • Repolarization is delayed

• Undershoot is reduced or missing

• Action potential is wider

  • Takes longer to return to rest

• Action potential propagation can still occur because propagation depends on Na⁺ driven depolarization to trigger the next segment

What happens to the graph of voltage vs. time of an action potential if K⁺ channels open more easily?

• Faster repolarization

• Bigger undershoot (more hyperpolarization)

• Peak might be cut short

  • Because K⁺ “fights” Na⁺ sooner

What do the hypothalamus & the pituitary do?

• Hypothalamus

  • Receives information from the rest of the brain & initiates responses

• Pituitary

  • Works with the hypothalamus to secrete hormones into the blood

How do the hypothalamus & posterior pituitary work together to release hormones?

• Posterior pituitary is made of axons from hypothalamic neurons

• The cell bodies are located in the hypothalamus & make the hormone

• The hormone is physically moved down the axon & released into the pituitary blood vessels

How do the hypothalamus & anterior pituitary work together to release hormones?

• Hypothalamic neurons secrete the first hormone

• That hormone acts on the anterior pituitary to release the second hormone into the bloodstream

What is the sensory receptor’s function?

To turn an outside stimulus into a change in membrane potential

What type of channels in sensory neurons respond to touch signals? Smell & taste?

• Touch: Stretch-sensitive channels

• Smell, taste: Receptors that detect chemicals & indirectly open channels

Map out how how light, retinal, opsins, & cation channels affect a photoreceptor’s membrane potential & neurotransmitter release.

• Light (photons) enter the eye & hit the retina

• The retina’s photoreceptor cells (rods & cones) detect light

• When more light is detected:

  • The molecule retinal that is in the photoreceptor cells is activated, and it changes shape

  • Opsin is bound to retinal, and detects retinal’s change in shape, activating the opsin

  • The activation of opsin activates a pathway that decreases cGMP and closes Na⁺ channels

  • K⁺ channels are always open, so without Na⁺ entering the neuron, K⁺ continues to flow out, causing hyperpolarization

  • Neurotransmitter release decreases

• When less light is detected:

  • Retinal in the photoreceptor cells remains inactive

  • Opsin is not activated

  • cGMP levels remain high, so Na⁺ channels remain open

  • With both K⁺ & Na⁺ channels open, K⁺ flows out & Na⁺ flows in, causing depolarization

  • Neurotransmitter release increases

How does information flow in the nervous system?

How does the sensory pathway flow?

How does light turn into neurotransmitter signals?

External stimulus (photons in light) → Change in membrane potential → Neuron releases a certain amount of neurotransmitter

Given a neuron’s responses to stimuli, how can you hypothesize its receptive field?

• A neuron’s receptive field is the stimulus & location in space that causes the strongest response

• To identify the receptive field:

  • Present stimuli at different locations

  • Observe when the neuron’s firing rate increases

  • The stimulus & location that produce the strongest response are the neuron’s receptive field

How do you distinguish between innate & learned behavior?

• Innate

  • All individuals in a population behave alike

  • Instinctive

  • Not modified & unaffected by environment

  • Low variation in population

  • Evolved through natural selection

  • Often have to do with important tasks for survival or reproduction

  • Cannot seem to adjust the behavior when the situation changes

• Learned

  • Allows individuals to change their behavior in response to their specific environment

  • Based on experience

  • Modified via trial & error

  • Affected by environment

  • High variation in population

  • Capacity to learn is a product of natural selection

How could an experiment using optogenetics demonstrate the concept of “fire together, wire together”?

• Principle: If two neurons that are connected to each other fire at the same time, it will cause stronger or more connections between them, so in the future if one neuron is activated, it will cause the other to fire too.

• Optogenetics: Genetically inserting Channelrhodopsin (ChR2) into mouse’s brain

  • Blue light inserted in the mouse’s brain will activate ChR2 → Na⁺ influx → Depolarization

• Experiment:

  • Part 1:

    • Put mouse in Location A → Location A neurons will fire

    • Scientists also force location A neurons to express ChR2 → Neurons will “fire together” that usually wouldn’t

  • Part 2:

    • Put mouse in footshock location B & turn on blue light → Location B neurons will fire & ChR2 in location A neurons will be activated → Location A ChR2-activated neurons will be linked with Location B footshock neurons

  • Test if neurons wired together:

    • Put mouse back in Location A → Location A channels activated because mouse is in Location A → Because Location A neurons are connected to (or wired to) Location B footshock neurons, then Location B neurons will also be activated → Mouse will freeze

What does it mean to say that a synapse is strengthened or weakened?

• A synapse is strengthened when an AP in the presynaptic neuron will cause a bigger response in the postsynaptic neuron.

• A synapse is weakened when an AP in the presynaptic neuron will cause a smaller response in the postsynaptic neuron.

Distinguish between the innate & adaptive immune systems in terms of cell types, pathogen recognition, & protection from infection.

• Innate immune system

  • Characteristics:

    • Fast, immediate response

    • Present at birth

    • Can attack pathogens never encountered before

    • Found in all plants & animals

    • Recognizes broad classes of pathogens

  • Recognition:

    • Detects PAMPs (Pathogen-Associated Molecular Patterns) such as:

      • Bacterial flagella

      • Bacterial cell wall

      • Viral RNA

    • Use Toll-Like Receptors (TLRs) to detect PAMPs

      • TLRs on innate immune cells detect PAMPs → Secrete cytokines, recruit more immune cells → Phagocytose pathogens, etc

  • Major cell types:

    • Macrophages

      • Large phagocytic cells that engulf pathogens

      • Functions:

        • Phagocytosis

        • Cytokine secretion

        • Talks to adaptive immune system

    • Dendritic cells

      • Functions:

        • Detect pathogens

        • Talks to adaptive immune system

    • Neutrophils

      • Functions:

        • Phagocytoses pathogens

        • First responder

        • Secretes cytokines

    • Eosinophils

      • Attacks larger pathogens like parasites & cancer cells

  • Protection:

    • The skin & other membranes

    • Some bodily fluids

      • Sweat

      • Tears

      • Mucus

    • Inflammation

      • Antimicrobial peptides: Molecules that directly attack invading microbes

      • Cytokines: Molecules that signal to other cells to do something

• Adaptive immune system

  • Characteristics:

    • Acquired

      • Prior exposure needed

    • Slower response (days-weeks)

    • Very specific signals recognized by countless receptors

    • Only found in vertebrates

  • Recognition:

    • Recognizes specific antigens

    • B & T cells respond to unique pathogen antigens

  • Major Cell Types:

    • B & T cells

      • Produce antibodies

        • Antigens are the particular outside shape of each pathogen

        • Antigens can be detected by antibodies

      • After infection, you make memory B & T cells

        • When you are exposed to the pathogen again, the memory cells react to the antigens of the pathogen directly & quickly

    • Antibodies

      • Tag the pathogen as being “bad” as a signal to the innate immune system

      • Block their ability to infect

      • Big variety possible

What are the two arms of the adaptive immune system?

• Cell-mediated arm

  • Cytotoxic T-cells infect body cells & cancer cells

  • When pathogens are inside body cells (viruses & some bacteria), the infected body cells need to be killed

• Humoral arm

  • B-cells divide to make plasma cells, which secrete antibodies

  • When pathogens are in blood & body fluids, antibodies can reach them

Map out the path of the adaptive immune system.

Map out the path of the innate immune system.

How would the innate immune system function be affected by a loss of macrophages? Defective TLR signaling? Loss of dendritic cells?

• Loss of macrophages

  • Effects:

    • Reduced phagocytosis

    • Fewer cytokines

    • Weaker activation of adaptive immunity

  • Result: Higher pathogen load early in infection

• Defective TLR signaling

  • Effects:

    • Pathogens not detected efficiently

    • Delayed immune response

  • Result: Pathogens replicate before immune response begins

• Loss of dendritic cells

  • Effects:

    • Adaptive immunity not properly activated

How would the adaptive immune system function be affected by a loss a B cells? A loss of T cells? Loss of memory cells?

• Loss of B cells

  • Antibodies not produced

  • Extracellular pathogens persist

• Loss of T cells

  • B cells not activated

  • Cytotoxic T cells poorly activated

  • Antibodies reduced

• Loss of memory

  • Repeated infections cause the same severity of illness

  • No enhanced secondary immune response

How do traditional vaccines work? How do mRNA vaccines work?

Traditional vaccines

• Types include:

  • Weakened pathogen

  • Killed pathogen

  • Purified pathogen protein

• How they work:

  • Vaccine introduces antigen

  • Antigen-presenting cells ingest antigen

  • Helper T cells recognize antigen

  • Helper T cells activate B cells

  • B cells becomes plasma cells

  • Plasma cells produce antibodies

  • Some B cells become memory cells

• Result: Future infection triggers rapid antibody production

mRNA vaccines

• Deliver genetic instructions for making a pathogen protein

• How they work:

  • Vaccine introduces mRNA from pathogen (antigen source)

  • mRNA codes for pathogen protein

  • Presented to immune cells

  • Helper T cells activate B cells

  • Plasma cells produce antibodies

  • Memory B cells form

Predict whether an infection or changes in B- & T-cell development might predispose someone to develop an autoimmune disease.

Normal Self-Tolerance

• During B- & T-cell development:

  • Many different receptors are generated

  • Developing lymphocytes are exposed to self-antigens

  • Cells that strongly recognize self-antigens are eliminated.

  • This prevents the immune system from attacking the body’s own tissues

Defective B- or T-cell Development

• Self-reactive B or T cells are not eliminated

• They mature & attack self-antigens

• Increased risk of autoimmune disease

Infection with Cross-Reactive Antigens

• A pathogen has antigens similar to a body’s own antigens

• Immune cells attack the pathogen

• The same immune cells may accidentally attack the body’s tissues

• Increased risk of autoimmune disease

How is pressure involved in the movement of water & nutrients in plant xylem & phloem?

• Xylem

  • Water moves from roots → leaves

  • No pumps in the roots

  • Transpiration at the leaves lowers pressure, so water evaporates through stomata

  • Very low pressure in the leaves causes water to be pulled upward from higher pressure in the roots

  • Movement occurs because of a pressure gradient created by evaporation at the top

• Phloem

  • Sugar is actively loaded into phloem at source cells in the leaves

  • High sugar concentration draws in water by osmosis, increasing pressure

  • At sink tissues (roots/storage), sugar is unloaded

  • Water leaves, lowering pressure

  • Sugar moves from high pressure (source) to low pressure (sink)

How is pressure involved in the movement of blood in vertebrates?

• The heart acts as a pump

• During ventricular systole, contraction increases pressure in arteries

• Blood flows from high pressure (ventricles/arteries) to lower pressure (capillaries → veins → atria)

• Pressure gradually decreases along pathway: Arteries → Arterioles → Capillaries → Venules → Veins

• Ventricles generate the most pressure because they have thicker muscle walls

How does blood flow through the four chambers of the heart, the great vessels, lungs, and the blood vessels?

• Blood passes the heart twice

• Body to heart (Systemic circuit) (deoxygenated)

  • Body capillaries → Venules → Veins → Vena cava → Right atrium

• In heart to lungs (Pulmonary circuit)

  • Right atrium → Right ventricle → Pulmonary artery → Lung capillaries → Pulmonary veins → Left atrium → Left ventricle

• Heart to body (System circuit) (oxygenated)

  • Left ventricle → Aorta → Arteries → Arterioles → Capillaries

• Arteries → Arterioles (Away from heart)

• Veins → Venules (Toward heart)

Draw out the ECG associated with heart beat and describe what is occuring during each section of the graph.

• P wave

  • Atrial contraction

  • Generated by the SA node

  • Atrial depolarization occurs

• QRS

  • Ventricular contraction

• T wave

  • Ventricular relaxation

What are the components of the circulatory system?

• Fluid in which materials are transported (blood)

• A pump to move the fluid around (heart)

• Vessels to provide controlled paths (veins, arteries, capillaries)

What are the roles of the veins, venules, capillaries, arterioles, & arteries?

• Veins: Carry blood toward the heart

• Venules: Connect capillaries to veins

• Capillaries: Allow for exchange of O₂/CO₂, nutrients, & waste

• Arterioles: Control blood flow into capillaries & help regulate blood pressure

• Arteries: Carry blood away from the heart

What is the cardiac cycle, & what it its order?

• Cardiac cycle: One complete phase of pumping & filling

  • Contraction phase is systole

  • Relaxation phase is diastole

• Order:

  • Atrial & ventricular diastole

    • Atria & ventricles are relaxed, & blood is returning to the heart

  • Atrial systole (ventricular diastole)

    • Atria contract, ventricles are still relaxed

  • Ventricular systole (atrial diastole)

    • Ventricles contract

    • Pushes blood to the next structure

What happens if the SA node is destroyed?

The AV node becomes the pacemaker, and there are no P waves

What happens if the atria do not depolarize normally?

• Atrial contraction is abnormal or absent

• Ventricles still contract, but rhythm may be slower

How does the electrical signal travel in the heart?

0. Sinoatrial node: Pacemaker

1. Spreads to atria

2. Spreads to atrioventricular node

3. Spreads down the septum

4. Spreads out to both ventricles

What are the differences between systolic & diastolic blood pressure?

• Systolic blood pressure

  • Arterial blood pressure during ventricular contraction

  • It is the higher number in a blood pressure reading because ventricular contraction generates the greatest pressure

  • Pumping pressure

• Diastolic pressure

  • Arterial blood pressure during ventricular relaxation

  • It is the lower number because the heart is not actively contracting, so arterial pressure falls

  • Resting pressure

What are cross-sectional & total cross-sectional area, & what is the pattern in the body?

• Cross-sectional area: The area of a vessel if you slice it & look at the opening

• Total cross-sectional area: The sum of all vessels at that level

• Pattern in the body:

  • Small in aorta (one large vessel)

  • Larger in arteries

  • Largest in capillaries (because there are millions of them)

  • Decreases again in veins

• Capillaries have the greatest total cross-sectional area

How is velocity related to total cross-sectional area? What is the pattern of blood velocity & why?

• Total cross sectional area & velocity are inversely related

• If total cross-sectional area increases → velocity decreases

• If total cross-sectional area decreases → velocity increases

• Pattern:

  • Highest near heart (aorta, arteries)

  • Decreases dramatically in capillaries

  • Increases somewhat again in veins (but not as high as arteries)

• Cause:

  • Pressure (higher pressure → faster velocity)

  • Total cross-sectional area (lower area → Faster velocity)

How is pressure related to total cross-sectional area? What is the pattern of blood pressure?

• Pattern:

  • Highest in aorta & arteries

  • Gradually decreases through arterioles

  • Much lower in capillaries

  • Lowest in veins & vena cavae

• Cause:

  • Pressure is generated by ventricular contraction

  • As blood moves through vessels, energy is lost due to:

    • Stretching of vessel walls

    • Friction within vessels

• Pressure steadily declines with distance from heart

What are pressure, total area, & velocity like in the aorta, capillaries, & veins?

• Aorta

  • High pressure

  • Low total area

  • High velocity

• Capillaries

  • Lower pressure

  • Highest total area

  • Lowest velocity

• Veins

  • Very low pressure

  • Lower area than capillaries

  • Moderate velocity

How is blood pressure controlled homeostatically?

• If blood pressure is low, heart rate increases & arteries & arterioles constrict, making blood pressure rise

• If blood pressure is high, heart rate decreases & arteries & arterioles relax, making blood pressure fall

How do changes in body posture affect homeostatic control of blood pressure?

• When a person stands up suddenly:

  • Gravity pulls blood downward

  • Less blood returns to the heart

  • Arterial blood pressure falls

• Homeostatic response:

  • Baroreceptors detect less stretch

  • Signal sent to medulla

• Effectors respond:

  • Heart rate increases

  • Arteries & arterioles contrict

• Result:

  • Blood pressure rises back toward the set point

  • If this reflex did not occur → Dizziness or fainting

How do changes in baroreceptor function affect homeostatic control of blood pressure?

• Typically, when blood pressure increases:

  • Baroreceptors detect increased stretch

  • Medulla decreases heart rate

  • Arteries relax (vasodilation)

  • Blood pressure falls toward normal

• If baroreceptors cannot detect stretch:

  • Changes in blood pressure are not sensed properly

  • The medulla does not adjust heart rate or vessel diameter appropriately

  • Blood pressure becomes unstable

  • Standing up could cause prolonged drops in pressure

• If baroreceptors reset to a higher set point, like in chronic hypertension:

  • High blood pressure is treated as acceptable

  • Homeostatic correction does not occur

  • Hypertension (high blood pressure) persists

How will blood pH levels change when the kidney reabsorbs bicarbonate ions? When bicarbonate ions are secreted?

• Reabsorption

  • From filtrate back to blood

  • Adds bicarbonate back to the blood

  • Blood pH increases (becomes more basic)

  • Occurs when body needs to correct low blood pH

• Secretion

  • From blood to filtrate

  • Removes bicarbonate from the blood

  • Blood pH decreases (becomes more acidic)

  • Occurs when body needs to correct high blood pH

Map out how blood pH is homeostatically controlled.

Map out the creation, processing, & path of filtrate in the human kidney.

1. Glomerulus: Blood pressure forces arteriole blood through slits to make the filtrate. Small things like water, ions, & sugars can go through the filter, but not cells or proteins.

2. Proximal tubule

• Filtrate has been made, so things can go back into the blood

• Glucose, amino acids, water, sodium, & bicarbonate are reabsorbed by blood

• Most of the reabsorption is done here

• The filtrate ends isosmotic

3. Descending nephron loop

• Water leaves filtrate & is reabsorbed into the blood

• Filtrate ends hyperosmotic

4. Ascending nephron loop

• Sodium is reabsorbed into the blood

• Extracellular fluid in medulla is salty

• Actively pumps salt out

• Filtrate ends hyposmotic

5. Distal tubule

• Water is reabsorbed if there is ADH, and sometimes bicarbonate is reabsorbed

• Filtrate ends hyposmotic without ADH, isosmotic with ADH

6. Collecting duct

• Water is reabsorbed if there is ADH because the ADH inserts aquaporins into the membrane, which allow water to flow out because the medulla fluid is saltier

• Sometimes sodium & bicarbonate are reabsorbed into the blood

• Bicarbonate is sometimes secreted into the filtrate

• Filtrate ends hyposmotic without ADH or hyperosmotic with ADH

What happens when glomerular filtrate rate is low? High?

• Low GFR

  • Waste products stay in tubule too long & move back into the body

  • Too much fluid is retained in blood

  • Filtration stops & wastes/excess fluids remain in blood

• High GFR

  • Important materials flushed out with urine before they’re recovered

  • Too much fluid loss

  • Damage to glomerular capsule & kidney failure

How do the kidneys control GFR?

• Myogenic mechanism

  • Smooth muscle around the arteriole detects stretch & controls the arteriole’s size

  • High blood pressure stretches the arteriole → arteriole constricts → less blood in kidney → GFR lower

  • Low blood pressure → arteriole is not stretched → more blood in kidney → GFR higher

  • Local; only affects the glomeruli

  • Controls how much blood reaches the glomeruli

  • More blood flow → higher GFR

• Controlling the renin-angiotensin-aldosterone system

  • Global; affects the whole body

  • Controls the blood pressure of all the body’s blood

  • Higher blood pressure → higher GFR

How do changes in the renin-angiotensin-aldosterone system affect blood volume & pressure?

• Low GFR causes the release of the hormone renin

• Renin causes the formation of angiotensin I

• Angiotensin I turns into hormone angiotensin II

• Angiotensin II causes the adrenal glands to release the hormone aldosterone

• Aldosterone increases the reabsorption of sodium in the distal tubule & collecting duct, making the blood saltier

• Blood pressure & volume increase because the increased salt concentration in the blood attracts more water through osmosis

What are the different types of osmolarity?

• Hyperosmotic → Concentrated

• Isosmotic

• Hyposmotic → Dilute

How do the functions of the distal tubule & collecting duct change with & without ADH?

• With ADH: Water is reabsorbed from the filtrate into the blood

  • In the distal tubule, filtrate stays hypotonic & ends isotonic

  • Fluid around the collecting duct is very salty, so water leaves the filtrate

  • Filtrate goes from isotonic to hypertonic, & hyperosmotic urine is produced

• Without ADH: Water is not reabsorbed & stays in the filtrate

  • In the distal tubule, filtrate remains hypotonic

  • In collecting duct, water cannot leave the filtrate, so the filtrate remains hypotonic

  • A large volume of hypotonic, dilute urine is produced

How is blood osmolarity homeostatically controlled? Map it out.

When osmolarity is high:

• Hypothalamus contacts other parts of the brain, to create a feeling of thirst

• Hypothalamus tells the posterior pituitary to release more of the hormone anti-diuretic hormone (ADH)

When osmolarity is low:

• Hypothalamus tells the posterior pituitary to release less of anti-diuretic hormone (ADH)

Map out the effects of angiotensin II.

Map out the flow of information in the nervous system.

What are the different types of muscle? What are sarcomeres & do they have sarcomeres?

• Skeletal

  • Attached to bones

  • Voluntary movement

  • Have sarcomeres

• Cardiac

  • Walls of the heart

  • Involuntary movement

  • Have sarcomeres

• Smooth

  • Walls of hollow, visceral organs

  • Involuntary movement

How do thin filaments, thick filaments, and Z lines move during muscle contraction?

• During contraction, thick & thin filaments slide together lengthwise

• Thin filaments (actin) slide toward the center of the sarcomere

• Thick filaments (myosin) stay in the same position

• Z lines move closer together as the sarcomere shortens

What are the steps of skeletal muscle fiber contraction?

1. Neuron has an action potential, which activates the neuromuscular junction

• In the neuromuscular junction:

  • The action potential in the neuron opens voltage-gated calcium channels

  • Calcium influx into the neuron causes the release of acetylcholine

  • Acetylcholine binds to its receptor on the muscle fiber, opening a channel that lets in sodium

  • Acetylcholine is broken down in the cleft by acetylcholinesterase

2. The muscle has an action potential, and the signal propagates to the rest of the muscle

3. Muscle contracts using cross bridge cycling

How is muscle contraction influenced by calcium?

• Without calcium

  • Myosin heads cannot bind to actin because tropomyosin is bound to actin and is in the way

• With calcium

  • Ca²⁺ binds to troponin

  • Troponin moves tropomyosin off the actin binding sites so the actin & myosin can form cross bridges

  • Myosin head turns & pulls thin filaments to contract

  • ATP binding to the myosin detaches the cross bridges

  • Energy from ATP hydrolysis moves myosin back into the initial state

What are the differences between the sympathetic & parasympathetic nervous system?

• Parasympathetic

  • Rest & digest

  • Promotes maintenance functions & conserves body energy

  • Promotes low blood pressure, low heart rate, & digestion

• Sympathetic

  • Fight or flight

  • Release epinephrine & norepinephrine

  • Increase heart rate

  • Increase blood pressure

  • Vasoconstriction

  • Increase blood sugar

What are the two parallel stress pathways?

Would a larger animal or a smaller animal have more trouble keeping its body temperature at its set point & why?

• A smaller animal

• Because smaller animals have a larger surface area to volume ratio

• This means that it has a lot of surface area compared to its volume, so there are lots of places for the heat to leave and not much heat stored inside, meaning that heat leaves quickly compared to how much heat it has

• A larger animal has less surface area compared to its volume, so there are fewer places for heat to leave and a lot of heat stored inside, so heat leaves slowly compared to how much heat it has

How can you become big while still having a high SA/V ratio?

• Be made up of many smaller units

• Shape

  • Have a folded, elongated, or branched shape instead of a compact sphere to increase surface area without greatly increasing volume

What does this arrow mean? ⊣

Block, inhibit, or decrease

What is a negative feedback loop?

• Occurs when a change in the level of something causes an effect that counteracts that change

• Stabilization

What is a positive feedback loop?

• Occurs when a change in the level of something causes an effect that increases that change

• Amplifies an effect or pushes the organism into a new state

What are the parts of a basic homeostatic circuit? Describe each part.

• Set point

  • Narrow range for value of variable

• Control center

  • Receives information from the sensor & relays info to the effector

• Effector

  • Cells, tissues, & organs that change things to get back to the set point

• Sensor

  • Thing in tissues or organs that detects body changes

How is the exchange of stuff with the environment related to the SA/V ratio?

• High SA/V allows for more exchange with the environment

  • Because there is more surface area relative to volume, so there is more space for diffusion of heat, gases, nutrients, and waste to occur

• Low SA/V allows less exchange with the environment

  • Because there is less surface area relative to volume, so there is less space for diffusion of heat, gases, nutrients, and waste to occur