Animal Phys Final

Question 1

Cells store energy in what two main forms?

Answer 1

Reducing energy
High energy covalent bonds

Question 2

Describe carbs

Answer 2

• Have many hydroxyl (-OH) groups
• Glucose is most common carb form
• Used for energy metabolism
• Used as a substrate in biosynthesis to form new or more complex carbs

Question 3

Describe monosaccharides

Answer 3

• Used for energy and as biosynthesis substrate
• Monosaccharides, also called simple sugars, are the simplest forms of sugar and the most basic units from which all carbohydrates are built. Simply, this is the structural unit of carbohydrates. They are usually colorless, water-soluble, and crystalline shaped organic solids

Question 4

Describe Complex Carbs

Answer 4

• Polysaccharides that are used for energy storage (i.e insulin, starch) and formation of structural molecules (chitin, cellulose)

Note: Amylose + amylopectin = starch

Question 5

Glycogen synthesis = ______
Glycogen degradation = ______

Answer 5

glycogenesis
glycogenolysis

Question 6

Describe the process of glycogenisis

Answer 6

1. Glycogen synthase is inactive
2. Protein phosphatase activates the complex
3. Glycogen (n glucose) interacts with the active glycogen synthase and is converted to glycogen (n+1 glucose)
4. Upon conversion protein kinase inactivates glycogen synthase and returns it back to it’s inactive state

Question 7

Describe the process of glycogenolysis

Answer 7

1. Glycogen phosphorylase is inactive
2. Glycogen phosphorylase kinase activates the glycogen phosphorylase
3. Glycogen (n+1 glucose) interacts with the active glycogen phosphorylase and is converted to back to glycogen (n glucose)
4. Upon conversion Glycogen phosphorylase phosphatase inactivates the glycogen phosphorylase and returns it to back to its inactive state

Question 8

Describe the process of ANAEROBIC glucose metabolism / breakdown

Answer 8

• Overall Rxn: Glucose + 2 ADP + 2 NAD+ → 2ATP + 2 pyruvate + 2 NADH + 2 H-
• Happens in cytoplasm
• Produces intermediates for synthesis of various molecules (Carbs, nucleic acid, amino acids or fatty acids)
• End product, pyruvate, can be used in further catabolic processes

Question 9

Describe AEROBIC pyruvate oxidation

Answer 9

1. Converts carbs (glucose) to pyruvate within cytoplasm
2. Pyruvate is carried into the mitochondria
3. Pyruvate Dehydrogenase (PDH) oxidises pyruvate to form acetyl-CoA + NADH

Note: Lactate and amine can also be turned into pyruvate

Question 10

Describe AEROBIC oxidation of NADH

Answer 10

• Glycolysis can only continue if NADH is oxidised to NAD+ and H+
• Two “redox shuttles” carry reducing equivalents (H+ atoms) from cytoplasm ←→ mitochondria:
  α - glycerophosphate shuttle
  Malate-aspartate shuttle

Question 11

Oxidation of NADH in the Absence of O2

Answer 11

1. NADH is oxidised in the cytoplasm
2. Buildup of NADH in cyto means drop in NAD+
   - This would inhibit glycolysis (since NAD+ is an important substrate)
3. Pyruvate + NADH + H+ ←→ lactate + NAD+
   - Catalysed by the enzyme lactate dehydrogenase (LDH)

Note: Other anaerobic pathways form less toxic end products and more ATP than lactase (2 ATP)
For example, succinate (4 ATP) and propionate (6 ATP)

Question 12

Describe lipids

Answer 12

• Lipids are used for energy metabolism, cell structures (e.g membranes), and signalling

Question 13

Describe fatty acids

Answer 13

• Saturated = No double bonds between carbons
• Unsaturated = One or more double bonds between some carbons
• Fatty acids are a more dense form of energy storage than carbs

Question 14

Describe the process of fatty acid oxidation

Answer 14

• β-oxidation
• Takes place in mitochondria
• Consumes an ATP to make 1 NADH, 1 FADH and 1 Acetyl-CoA
• Acetyl-CoA is then oxidised in next step

Question 15

What is the degradation process of glucose to ATP?

Answer 15

1. Glycolysis:
   * Anaerobically happens in cytoplasm, one glucose is broken down into two pyruvates
   * Glucose + 2 ADP + 2 NAD+ → 2ATP + 2 pyruvate + 2 NADH + 2 H-
2. Pyruvate oxidation:
   * Pyruvate is carried into the mitochondria
   * Pyruvate is oxidised by Pyruvate Dehydrogenase (PDH) to form acetyl-CoA + NADH
   * Can be done aerobically or anaerobically
3. Acetyl CoA is either converted to ketones or sent to the Kreb’s cycle
4. In the tricarboxylic acid cycle (TCA aka Krebs) acetyl-CoA is converted to CO2, NADH (x3), FADH2 (x1), GTP (x1)
5. These reducing agents are oxidised at the ETC to release energy which creates the gradient that drives ATP synthesis/phosphorylation

Question 16

Describe ketones

Answer 16

• Some tissues cannot metabolise fatty acids , but they can metabolise ketones. So ketones are pretty much a form of acetyl-CoA that can be stored, or used by any type of tissue.
• Ketogenesis:
  1. Fatty acids converted to acetyl-CoA
  2. Acetyl-CoA converted to ketones
  3. Ketone bodies can move through circulation
• Ketolysis
  1. Ketones are broken down to acetyl-CoA Which can then participate in oxidative phosphorylation

Note:

Question 17

Describe the ETC

Answer 17

• Has five multisubunit protein complexes embedded within the inner membrane between the intermembrane and the matrix. -
• There’s also two electron carries (ubiquinone and cytochrome c)
• Complex I reduces NADH to pump H+ ion from the matrix into the intermembrane space or to complex II
• Complex II turns FAD → FADH, and then cyclically reducing FADH back into FAD and omitting an electron to complex III
• Complex III hands the electron over to cytochrome c which then delivers the electron over to complex IV
• Complex IV oxidises cytochrome c and is itself reduced by cytochrome c. Complex IV uses O2 and adds it to H to get a water molecule byproduct and pumps an electron into the intermembrane space
• Electron buildup in intermembrane space creates gradient that drives protons through ATP synthase, phosphorylating ADP–>ATP
• Generates a proton gradient, heat, water and reactive oxygen species as final products

Question 18

Describe phosphocreatine

Answer 18

• Is used for muscle energy, found within the myofibril
• Phosphocreatine pretty much just acts as a transporter of phosphate from the main ATP supply chain (the mito) to the sister branch producer (the muscle)
• Reaction is reversible so relative rate of ATP versus phosphocreatine production depends on ratio of concentration of substrates/products
  -Phosphocreatine can also move throughout cell (like ATP)
• Thus, it can enhance flux of high energy phosphate molecules from site of synthesis (e.g. mitochondria) to site of hydrolysis (e.g. muscle sarcomeres)

Question 19

What is 31P-NMR Spectroscopy

Answer 19

• Measures ATP turnover
• Detects change in NMR spectra as Pi groups shift between ATP and inorganic phosphate

Pros:
* Accounts for aerobic, anaerobic metabolism, etc.
* Accurate over extremely short time scales. E.g. A single muscle contraction

Cons:
* Logistically difficult
* Subject must be restrained, possibly anaesthetised
* Equipment not portable, and complicated

Question 20

Describe direct calorimetry

Answer 20

• Measurement of heat of chemical/physiological processes (unit can be ‘calorie’)

Pros:
* Quite accurate under many conditions
* Accounts for aerobic and anaerobic energy production

Cons:
* Subject must be restrained
* Equipment heavy and complicated
* Makes assumptions about anabolic versus catabolic activity

Question 21

What is Hess Law?

Answer 21

Any anatomical fuel source will always exhibit the same total amount of energy released (as heat) regardless of what intermediate states occur during their breakdown

Question 22

In scaling relationships what are two things that are factors of volume , and two that are factors of surface area?

Answer 22

Some things are a factor of volume (internal size of animal):
- Total metabolic rate
- Total heat production (cellular respiration byproduct)

Some things are a factor of surface area:
- Respiration (how many cells require air)
- Absorption/expulsion (for animals who do so via skin membranes, like heat loss through skin or water absorption)

Note: Ratio between surface area and volume is 2:3. So, BMR can be predicted to scale with an exponent of 0.667
- Kleiber was the one to find significance and to quantitate the relationships

Question 23

If resting animal cells (regardless of animal size) had a similar metabolic rate (i.e heat production), larger animal would have relatively ____ surface area for dissipating extra heat

Why?

Answer 23

less

As animals grow in size their inside (volume) gets “more bigger” than their outside (surface area).

Question 24

Define thermal inertia

Answer 24

The tendency of a material (animal) to resist thermal change.

In our case an animal with a high metabolic rate in relation to it’s size would have low thermal inertia, like a mouse. So it’s losing heat relatively faster than it’s larger counterpart, a rat for example.

Question 25

Define basal metabolic rate

Answer 25

- Metabolic rate of homeothermic animal at rest inideal conditions - Does not scale proportionally to volume. - Slowest metabolic rate (unless in torpor/hibernation)

Question 26

In ____ ____, the growth rates of different body parts differ from that of the whole body. In contrast, in ____ ____, body parts grow at the same rate as the rest of the body.

Answer 26

allometric growth isometric growth

Question 27

What are the terms that correlate with each definition? 1. The capacity to do work 2. The transfer of energy by a force (mass x acceleration) acting on an object as it is displayed (force x distance) 3. The rate at which work is done

Answer 27

Energy Work Power

Question 28

What is the respiratory quotient and some important things to note about its ratios?

Answer 28

- When respiring the body uses three different substrates. By isolating mitochondria and observing the rate of CO2 production/O2 consumption we are given the RQ. The RQ can help us determine which substrate is being used as fuel Carbs: When RQ ≈ 1, O2 consumed = CO2 produced Lipids: When RQ ≈ 0.7, O2 consumed > CO2 produced Proteins: When RQ ≈ 0.85, O2 consumed > CO2 produced

Question 29

What is the respiratory exchange ratio (RER) and how does it differ from the respiratory quotient?

Answer 29

- Respiratory Exchange Ratio (RER) directly measures Vol CO2 released/Vol O2 absorbed at the mouth - Respiratory quotient, on the other hand, measures directly at the tissue

Question 30

Endurance training burns ____, bursts of strength require ____

Answer 30

lipids carbs

Question 31

How does the ATP/O stoichiometric relationship vary with fuel type?

Answer 31

- In order for isolated cells to produce a given # of ATP molecules: 14.9 – 18.7% more O2 required when oxidising fats, compared to carbs - Sugar is the more O2-efficient fuel source

Question 32

What is the difference between metabolism and metabolic rate?

Answer 32

Metabolism: The set of processes by which cells and organisms acquire, rearrange, and void commodities (e.g. elements or energy) in ways that sustain life Metabolic rate: An animal’s rate of energy consumption; the rate at which it converts chemical-bond energy to heat and…work. (rate of power)

Question 33

Describe chamber respirometry and it's pros/cons

Answer 33

- Animal enclosed in a chamber where you are flowing air from outside through the chamber and measuring how the air changed from entering and exiting the chamber as a result of how the animal affected it - Pros * Easiest approach * More sure that all expired gases accounted for * More accurate * Quality of air provided (environment) easier to control - Cons * Animal constrained, less natural behaviour * Risk of asphyxiation * Can be messy * Animal may do all its functions in chamber

Question 34

Describe chamber respirometry in a closed system and it's pros/cons

Answer 34

- Used on small things. You dont let air recirculate through thus the animal rebreathes the air and continuously raises the CO2 and water vapour level, decreases oxygen level. Can measure pressure change. Pros - More sure that all expired gases accounted for - Quality of air/water provided (environment) easier to control Cons - Risk of asphyxiation if O2 level gets too low, CO2 level gets too high - More accurate with longer time scales - Activity state must be known or constant - Switching between rest and activity complicates calculations

Question 35

Describe mask respirometry and its pros/cons

Answer 35

- A variant of flow-through chamber respirometry in which the chamber only covers the mouth/nose/head - Done when most oxygen is exchanged utmostly through inhalation/exhalation Pros: Small volume, faster flow rates mean even greater temporal resolution; animal can behave nearly naturally Cons: Poorer signal to noise ratio; composition of gases harder to control; must assume gas concentrations in surrounding ambient air

Question 36

Fill in the blanks

Answer 36

Question 37

Given that during and after exercise, O2 consumption rates are high, what would you expect to happen as you approach and persist through rest?

Answer 37

- Initially O2 consumption levels and ATP turnover rates are high, and begin to decline - Even when rest is reached O2 remains high because : 1. lactate goes through cori cycle to replenish glycogen stores and is also used as a substrate in oxidative phosphorylation in aerobic tissue 2. Rebuilding phosphocreatine at expense of ATP (now largely being generated aerobically)

Question 38

Describe Lactate

Answer 38

A byproduct of anaerobic glycolysis. Glucose is broken down into pyruvates in the cytoplasm, however there's no oxygen so it can't move to the mitochondria. Acid (H+) is attached to pyruvate and that is lactate. It acts as a buffer for acidity. The hydrogen can also be removed later and combined with oxygen to form water.

Question 39

What is the cori cycle?

Answer 39

Two lactates in the liver have their hydrogens removed and then combine to form a glucose which returns to tissue to rebuild glycogen

Question 40

Tf is glycogen and why do I forget?

Answer 40

This stored form of glucose is made up of many connected glucose molecules and is called glycogen. When the body needs a quick boost of energy or when the body isn't getting glucose from food, glycogen is broken down to release glucose into the bloodstream to be used as fuel for the cells.

Question 41

Define the standard metabolic rate

Answer 41

Same as BMR, except for poikilothermic animal, at a defined environmental temperature

Question 42

What is the order in which fuel sources are consumed over time of physical exertion

Answer 42

Question 43

Define the resting metabolic rate

Answer 43

Metabolic rate of animal at rest under defined conditions Not necessarily during quiescent (inactive) phase, or totally post-absorptive, or within TNZ

Question 44

What is the field metabolic rate?

Answer 44

The realised metabolic rate of an animal in the wild

Question 45

What is the difference between maximum aerobic metabolic rate (VO2max) and supramaximal metabolic rate?

Answer 45

- Maximum Aerobic Metabolic Rate (VO2max) is the maximum SUSTAINABLE VO2 seen during intense aerobic exercise or when homeotherm is exposed to very cold temps. The Supramaximal Metabolic Rate is above the VO2max but isn't sustainable. - Analogy: VO2max = ultramarathon running SMR = 100m burst

Question 46

What is the daily energy expenditure?

Answer 46

- Total energetic cost of a day of life - NOT a metabolic RATE, an energy amount - Useful for considering ecology, survival, etc.

Question 47

The whole animal metabolic rate is _____ in small animals than it is for big animals. However the mass-specific metabolic rate (MR/kg) is _____ in smaller animals than in larger animals.

Answer 47

lower higher

Question 48

What are the equations for whole-animal metabolic rate and for mass-specific metabolic rate?

Answer 48

Question 49

Rate of heat production should be a function of ____ (The size of all the cells consuming energy and producing heat ) Rate of heat loss should be a function of ___ ____ (Heat is lost to environment across surfaces)

Answer 49

volume surface area

Question 50

What is the total thermal energy equation?

Answer 50

Total thermal energy = ∆Heat = ∆Hmetab + ∆Hconvec + ∆Hrad + ∆Hevap

Question 51

What are the four types of heat exchange?

Answer 51

1. Convection: * Transfer of thermal energy between an object and an external medium that is moving 2. Radiation: * Emission of electromagnetic radiation 3. Evaporation: * Water molecules absorb thermal energy from a surface when making the transition from liquid to vapour 4. Conduction: * Transfer of thermal energy between one object or fluid to another

Question 52

What is Fouriers Law?

Answer 52

Question 53

What are Bergmann and Allen's rules and why do they make sense?

Answer 53

Bergmann’s rule: - Animals living in cold environments tend to be larger because larger animals exchange heat less than smaller ones due to their smaller surface area-volume ratio Allen's rule: - Body form or shape is linear in warm climates and more rounded and compact in cold climates. Being round and compact = less surface with more volume Note: The more volume = greater metabolic heat output The less surface area = less loss of heat to environment

Question 54

Match definitions to terms 1. Poikilotherms: 2. Homeotherm: 3. Endotherm: 4. Ectotherms: A. Body temp derived from environment B. Body temp varies C. Body temp produced metabolically D. Body temp is stable

Answer 54

1-B 2-D 3-C 4-A

Question 55

What is regional endothermy and what is an example of regional heterothermy?

Answer 55

- The ability to conserve metabolically derived heat to maintain the temperature of certain tissues elevated above ambient temperature 1. Tuna, unlike most fish, maintain heat in red muscles which are kept more towards the core of their bodies, which minimises heat loss via diffusion to the environment.

Question 56

What is temporal endothermy?

Answer 56

Phase of time where body temperature is maintained. This includes torpor, which lasts less than a day, and hibernation/aestivation which lasts much longer

Question 57

What are the three thermal zones of homeotherms?

Answer 57

1. Thermoneutral zone: - Optimal range for physiological processes; metabolic rate is minimal 2. Upper critical temperature (UCT) - Metabolic rate increases as animal induces a physiological response to prevent overheating 3. Lower critical temperature (LCT) - Metabolic rate increases to increase heat production - Animals differ in the width of their thermoneutral zone, UCT, and LCT

Question 58

What are the three (kinda 5) thermal zones of poikilotherms?

Answer 58

1. Preferred temperature: - Ambient temperature for optimal physiological function 2. Incipient lethal temperature: - Ambient temperature at which 50% of animals die * Incipient upper lethal temperature (IULT) * Incipient lower lethal temperature (ILLT) 3. Range of tolerance - Range of ambient temperatures between IULT and ILLT

Question 59

What's the difference between eurytherms and stenotherms?

Answer 59

Stenotherms can tolerate only a narrow range of ambient temperatures. Eurytherms can tolerate a wide range of ambient temperatures and occupy a greater number of thermal niches

Question 60

How does thermogenesis by ion pumping work?

Answer 60

- Ion-pumping membrane proteins produce heat For example, billfish heater organs which are modified muscles that don’t contract. Heat is produced in these muscle tissues by: 1. Reduction of ATP → ADP + P by Ca+2ATPase which pumps Ca+2 through the sarcoplasmic reticulum 2. When substrate is catabolised from Ca+2 and ATP → ATP + P 3. From the NADH → O2 ETC process in the mitochondria

Question 61

How can insects produce heat prior to flight?

Answer 61

1. They have a carbohydrate metabolism in flight muscles. Within these muscles opposing enzymes are activated, constantly anabolising and catabolising ATP → ADP + P → ATP to produce heat as a byproduct 2. They also contract antagonising flight muscles, thus the muscle does not contract yet remains tense. Energy is expended and heat is produced without movement required. This is a coordinated version of shivering 3. Finally the frequency and orientation of their wings are controlled to avoid generating lift – wing buzzing

Question 62

What is a homeoviscous adaption?

Answer 62

- Maintenance of membrane fluidity at different temperatures by changing membrane lipids (cholesterol content). This is done by: 1. Decreasing the length of fatty acid chains increases fluidity 2. Adding double bonds to fatty acids (unsaturation) increases fluidity 3. Changing the polar head of the lipid to either: * Phosphatidylcholine (PC): to decrease fluidity * Phosphatidylethanolamine (PE): to increase fluidity

Question 63

How is membrane fluidity affected by temperature?

Answer 63

- Low temperatures cause membrane lipids to solidify - High temperatures increase membrane fluidity

Question 64

___ ____ exhibit enzyme activity in relation to temp that underpins difference in performance

Answer 64

LDH alleles

Question 65

What are psychotrophs?

Answer 65

- Animals that thrive at low temperatures - Psychrotrophs possess cold adapted enzymes 1. Fewer weak bonds 2. Enzymes breathe (jiggle) more easily at low temperature - But cold-adapted enzymes are more vulnerable to temperature dependent unfolding

Question 66

Describe freeze-avoidance

Answer 66

Animals can allow their tissues to freeze in a controlled, safer way. They can do this by producing antifreeze molecules which are proteins or glycoproteins that depress the freezing point by non colligative actions (depend on the identity of the dissolved species and the solvent). This disrupts ice crystal formation by binding to small ice crystal and preventing growth

Question 67

Describe freeze-tolerance

Answer 67

- Animals use behavioural and physiological mechanisms to prevent ice crystal formation (e.g frogs) - Two mechanisms of freeze-tolerance 1. Produce nucleators outside of the cell which control the location and kinetics of ice crystal growth. So the extracellular fluid freezes, but intracellular fluid remains liquid 2. Produce intracellular solutes to counter the movement of water into the cell

Question 68

What are the advantages of a higher body temp?

Answer 68

↑ growth, development, digestion, biosynthesis

Question 69

What are internal thermostats?

Answer 69

- Exactly as the name suggest, how the body knows/perceives the temperature. - In mammals info from central and peripheral thermal sensors is integrated in the hypothalamus which sends signals to the body to alter rates of heat production and dissipation - In birds the thermostat is located on the spinal cord

Question 70

What is shivering thermogenesis?

Answer 70

- Uncoordinated myofiber contraction that results in no coordinated net muscle work but results in heat as a byproduct. - It is unique to mammals and birds - Cannot be sustained for long, the muscles will eventually run out of nutrients - When the muscles are in use, prevents locomotion

Question 71

What is brown adipose tissue and how does it work? (BAT)

Answer 71

- Tissue found in small mammals and newborns in cold climates. - Within the tissue there's a high density of mitochondria which produce a protein called UCP1 (Uncoupling Protein 1) which work by: 1. The sympathetic nervous system activates UCP which uncouples the mitochondrial ETC and proton pumping from ATP synthesis. This creates a futile cycle where H+ ions move through the UCP gradient, but don't produce ATP 2. This means that fatty acid oxidation must occur to produce energy (releasing more heat as byproduct compared to ETC)

Question 72

What is a Blastula (or blastocyst)?

Answer 72

A sphere of undifferentiated cells that forms shortly after initial bout of cell division Note: It implants in your uterine wall, eventually becoming the embryo and then the fetus

Question 73

What is gastrulation and what are the steps?

Answer 73

The process of invagination and differentiation into 2 or 3 cell layers of a blastocyte. Every animal except sponges experiences this phenomenon 1. Blastopore begins to form along the flat bottom of the blastocyte 2. Some cells inside the blastocyte break loose and form mesenchyme 3. Some mesenchyme attach themselves top the top of the blastocyte (archenteron) and then extend villi to the roof 4. The villi contract, drawing the blastopore upwards, developing the invagination 5. The opening of the invagination becomes the anus of the animal, the archenteron becomes the mouth

Question 74

Describe a batch-reactor stomach

Answer 74

- Ingested food enters and leaves the stomach pouch through a SINGULAR tube. - Stomach composition changes with time

Question 75

Describe a continuous-flow stirred-tank stomach

Answer 75

- Ingest food continuously enters the stomach through one tube, continuously exits through another - Food that enters is stirred/mixed and barely digested before leaving - Stomach composition does not change with time when in a steady state

Question 76

Describe a plug-flow reactor stomach

Answer 76

- Continuous input and output of food is pushed through the tube by an axial gradient (e.g peristalsis) - Stomach composition does not change with time at any point along the reactor

Question 77

What are the guts in order from ingestion to defecation?

Answer 77

1. Headgut 2. Foregut 3. Midgut 4. Hindgut Acronym: He Fancies Mean Head

Question 78

What does the hindgut do and what organs are associated with it?

Answer 78

- The hindgut is all about waste storage but in many animals plays a huge role in ion-hydration balance - Large intestine/colon/coclea/rectum

Question 79

What does the midgut do and what organs are associated with it?

Answer 79

- Responsible for digestion and absorption of nutrients - Small intestine, duodenum, ilium, jejunum

Question 80

What do the foregut and headgut do and what organs are associated with em?

Answer 80

- Responsible for ingestion conduction, food storage and digestion - Esophagus, stomach

Question 81

Describe goblet cells

Answer 81

- Found in small intestine and respiratory tract - Produce mucus which help protect the tissues from the gastric acid

Question 82

Describe parietal cells

Answer 82

- Made in the stomach gastric pits - Produce hydrochloric acid (HCl) which breaks down food and kills bacteria

Question 83

Describe chief cells

Answer 83

- Made in the stomach gastric pits - Create pepsinogen which is activated by HCl. When activated it becomes pepsin which breaks down proteins

Question 84

Describe chyme

Answer 84

- Increases the surface area of food by breaking it down into a thick semifluid mass. - Also stimulates digestive glands (gallbladder and pancreas) to secrete their respective solutions (bile, digestive enzymes, and bicarbonate).

Question 85

What are the two types of mammalian stomachs and how do they differ?

Answer 85

1. Monogastric: * A singular stomach compartment * Humans 2. Digastric (Ruminant): * Four stomach compartments * These mammals must regurgitate

Question 86

Describe the movement within the intestine in animals

Answer 86

- Small animals can get away with using cilia to facilitate the movement of food particles along the gut system, large animals cannot. Therefore we use a process called peristalsis which pushes food via a wave of circular muslce contraction, followed by alternating waves of longitudinal muscle contractions Note: Segmentation can occur where a bolus (block of semifluid digested food) that is two big is cut in half by the contraction of circular muscles pinching it in half

Question 87

How are the types of carbs (glycogen, starch, disaccharides, cellulose) digested and where?

Answer 87

Question 88

How does the digestion of glycogen/starch work?

Answer 88

1. Monomers are broken apart by salivary or pancreatic amylase 2. Produces either maltose (disaccharide) or limit dextrins (oligosaccharide) Note: Amylase can only break down the a-1,4 linkages (linear) of the monomers, they however cannot breakdown the a-1,6 linkages.

Question 89

Match the disaccharide to the monosaccharide products it yields 1. Sucrose 2. Lactose 3. Maltose A. Glucose + Glucose B. Glucose + Fructose C. Glucose + Galactose

Answer 89

1-B 2-C 3-A

Question 90

When must we rely on symbiotic gut microflora?

Answer 90

- When our small intestine must breakdown cellulose or inulin because we lack the essential enzyme to do it ourselves.

Question 91

How do termites acquire gut microflora?

Answer 91

- Symbiotic protists help termites digest the cellulose and lignin (wood poly-aromatic alcohols) but eventually termites must moult to grow. Unfortunately, digestive tract lining also gets molted so they lose the flora. In order to regain it, they must eat their nestmates' feces

Question 92

How are carbohydrates absorbed at the brush border?

Answer 92

Note: brush border are a stria of microvilli on the plasma membrane of an epithelial cell (as in a kidney tubule) that is specialized for absorption.

Question 93

How are the midguts of small flying invertebrates specialised

Answer 93

- They require more absorption per unit surface area because they need to optimise their stomach size to efficiency ratio - To do this they have increased villi length (increase SA), and also leaky guts which allow passive movement of sugars and AA

Question 94

How are the foreguts of small flying invertebrates specialised

Answer 94

- Have a lil pouch called a crop to store shit, since they gotta use their forearms to fly

Question 95

Describe the post-absorption processing of toxins

Answer 95

- Orally ingested toxins are dissolved either in the stomach where they are then absorbed in the blood stream through the epithelial cells, or by the small intestine - Once in the system they are brought to the liver which inactivates the toxin or excretes it to gull blader

Question 96

How can fibre help constipation?

Answer 96

- Fibre is a carb, hydrophilic - Retains more water in small intestine, large intestine has less water which encourages excretion of water from large intestine. - Keeps stool soft making defecation easier

Question 97

Describe the insulin response in glucose homeostasis

Answer 97

1. When a meal is had, glucose levels rise and is absorbed. 2. Insulin is released 3. Stimulates glucose uptake (conversion to glycogen or by being consumed) 4. Promotes lipogenesis while suppressing lipolysis, and hence free fatty acid flux into the bloodstream decreases (so glucose must be used for fuel) Counter: 5. If glucose level is too low, glucagon instructs the liver to convert glycogen to glucose, making glucose more available in the bloodstream

Question 98

WTF is wegovy/ozempic?

Answer 98

- Drug used for diabetic treatment Wegovy works by helping to regulate food intake and appetite. GLP-1 targets areas of the brain that help to regulate appetite, especially after eating. It also slows how quickly the stomach empties, which makes you feel fuller for longer. In addition to this, Wegovy enhances the production of insulin.

Question 99

What is biotransformation for secretion?

Answer 99

- Altering the structure of a lipophilic toxin in the digestive system so that it becomes hydrophilic, and easier to excrete - Can also inactivate and activate drugs as well (somehow idk)

Question 100

Talk to me bout some sugar absorption (I am in steep mental decline)

Answer 100

- Sugar uptake is constrained at multiple steps: 1. How fast it can be delivered via circulatory system. 2. How fast it can be taken up by the liver or muscles and then oxidised - Glucose is used up more fully and faster than fructose, however a mixture of the two works best - Human liver takes up all fructose ingested before distribution. Free fructose in our diets leads to rise in obesity, promotes lipogenesis - Human muslces take up surcose and use it as a substrate to help catabolise ADP+Pi --> ATP

Question 101

Talk to me bout mammalian closed (blood in vascular system) circulatory system

Answer 101

1. Starts with deoxygenated blood from heart which goes through the pulmonary circulation to the lungs. 2. Gas exchange occurs and the oxygenated blood is pumped through the venous system to the left ventricle which then restarts the process. - Mammals have a four chambered heart with an atria and ventricle on each side. . Gym pump is caused by the increased blood flow to the muscles.

Question 102

What is the difference between pulmonary and systemic (venous) circulation?

Answer 102

Pulmonary = - Movement of blood between the lungs and heart. - Shorter time to complete cycle. - Have thick muscular walls Systemic = - Movement of blood between the heart and body. - More vascularity - Have thin elastic walls Notes: It takes less pressure from the right side of heart to drive flow thru pulmonary than it does for the left to pump blood through the systemic circulation

Question 103

What is the importance of the lymphatic system?

Answer 103

The lymphatic system is important for the optimal functioning of our general and specific immune responses. The lymph nodes monitor the lymph flowing into them and produce cells and antibodies which protect our body from infection and disease.They then drain that lymph fluid, and return it back to circulation

Question 104

Talk to me bout insect open circulatory system

Answer 104

Have a heart (ostia) and store hemolymph in sinuses surrounding organs. The primary hemolymph (circulatory fluid) is pumped through a muscular heart into an arterial system and then eventually the fluid is dumped out into the general extracellular fluid bathing the tissues of the animal. The hemolymph contains nutrients, excrement or harmful-organism deteriorators which osmotically diffuse into whatever centres they're needed at. Close to the heart there are openings where the fluid can reenter the heart to be pumped again.

Question 105

What are the circulatory fluids found in vertebrates?

Answer 105

1. RBC, carry oxygen, nucleated cells 2. Platelets (injury vessels to clot, plugs blood leaks) 3. WBCs, made from monocytes, lymphocytes and other things

Question 106

What are the fractional composition amounts of the blood when centrifuged?

Answer 106

blood is composed of like 47.5% plasma (lightest), the buffy coat WBC about 5% (middle) and RBC for 47.5% and is the heaviest

Question 107

Describe Haemoglobin

Answer 107

- Haemoglobin is where 98.5% of O2 in RBCs is bound to. Composed of two alpha-subunits and two beta-subunits. - Oxygen binds to the haemoglobin because of the “heme group” which has a nitrogen-surrounded Fe group at the centre which is where the O2 binds to.

Question 108

____ can reversibly bind O2 to its heme group acts as a storage locker for oxygen within the muscle

Answer 108

myoglobin

Question 109

SHOULD I MAKE A CARD FOR THE WHOLE HAEMOGLOBIN TO MUSCLE PROCESS?

Question 110

What are the circulatory fluids found in invertebrates?

Answer 110

- Insect circulatory fluid is called hemolymph (not blood) - In many insects it is not responsible for O2/CO2 delivery, the tracheal system is. Rather they carry nutrients and hormones and contain hemocytes which work like WBC (immune response) Note: IF PRESENT, the resp. pigments are found in plasma

Question 111

Describe oxidation dissociation curves

Answer 111

- Represents oxygen saturation (y-axis) as a function of the partial pressure of oxygen (x-axis) - P50 = Partial pressure at which pigment heme groups are 50% saturated. On a graph, the x-value where half of the total y-value occurs - The higher the PO2 level at P50 the more effective it is - The shape of the oxygen dissociation curve of Hb is sigmoidal, whereas that of Mb is not (it is hyperbolic); only the sigmoidal curve is characteristic of the cooperative process.

Question 112

How does the binding of oxygen to Hb affect the surrounding Hb?

Answer 112

- When one heme group in an Hb gets oxygenated, the other groups become more easily oxygenated, even in the Hb nearby. Conversely as deoxygenation occurs, the more heme groups that lose an oxygen, the easier it becomes for the other groups to lose theirs. This helps that there are many subunits. However in myoglobin there are insufficient subunits for such a phenomenon to take place between Mb and Mb. - The affinity for myoglobin for oxygen is higher, stronger than the affinity for oxygen of haemoglobin - When hemoglobin-oxygen affinity increases, the oxyhemoglobin dissociation curve shifts to the left and decreases p50

Question 113

What is haemocyanin?

Answer 113

- Blue respiratory pigment found in horseshoe crabs. They don't contain iron or heme group, rather they have copper. Floats freely in plasma, not constrained to RBCs - Horseshoe crab blood contains a protein called coagulogen which coagulates to trap and bind to bacteria which can tell us if a blood of a donor is infected with something - The shape of the oxygen binding curve should be exponential due to the fact that it is a single monomer, which would not function cooperatively

Question 114

What is Hemerythrin/myohemerythrin?

Answer 114

- Contains iron, but no heme group - Found in some marine inverts, and a single annelid worm genus - Colourless when deoxygenated, pink-violet when oxygenated

Question 115

What is Chlorocruorin?

Answer 115

- Found in plasma of many animals (mostly worms) - Composed of multiple monomers (sigmoidal O2 binding curve) - Contains “abnormal” heme group, has iron however it has a different structure - Incidentally some nematodes and arthropods have Hb floating in plasma (or even inside nerves or muscle fibres - similar to role of Mb in us)

Question 116

What factors decrease the affinity of Hb for oxygen?

Answer 116

1. Increased temp. Higher temp = more cellular respiration = higher O2 demand = need for Hb to let go of O2 more easily 2. ↑ levels (more binding of…) 2,3-DPG (e.g. mammals) ATP, GTP, (e.g. fishes) IP5 (birds) 3. ↓ pH (Bohr shift, as RBC encounter a local environment that becomes more acidic it shifts their curve for Hb to the right, thus less affinity for oxygen) 4. ↑ CO2 (carbamino-haemoglobin formation: HbCO2)

Question 117

If the curve goes right and the P50 climbs the x-axis. This indicates a _____ affinity for Hb and O2. Which means that it takes ____ PO2 to get the same level of binding.

Answer 117

lowered more

Question 118

What do a left or right shift on the oxygen dissociation curve indicate?

Answer 118

Left = More affinity for oxygen (more intense bonding) Right = Less affinity for oxygen (less intense bonding)

Question 119

Where there is ____ levels of O2 consuming tissues you would tend to see a ____ in pH, which encourages Hb affinity to ____ so that it lets go of it’s oxygen.

Answer 119

high decline lower

Question 120

What are the differences between polycythemia and anaemia?

Answer 120

Polycythemia: Proportion of RBC in blood is much higher than average Anaemia: Proportion of RBC in blood is much lower than average

Question 121

How do CO2 levels differ between arterial and venous blood?

Answer 121

Arterial and venous CO2 levels teeter totter each other as they counter each other.

Question 122

What is the Bohr Effect? Hint: ties to Hb

Answer 122

Question 123

How does elevation affect relative gas partial pressures in the: 1. lumen of the lung 2. Lung capillaries 3. Diffusion gradient

Answer 123

Question 124

What is a behavioural response to lower PO2?

Answer 124

Hyperventilation: - Called the “Hypoxic Ventilatory Response” (HVR) - Enhances O2 AND CO2 exchange, temporarily Note: It’s already easier to lose CO2 than O2 so overall CO2 levels lower more significantly, leading to slight increase in pH (Bohr effect: thus Hb affinity for O2 increases)

Question 125

Lower P50 for O2 ______ uptake by Hb at lungs, but _____ release at tissues

Answer 125

encourages discourages note: lower P50 = lower PO2 = oxygen scarcity in environment. so the lungs want to take up as much oxygen as they can, and use up as little as it can

Question 126

What physiological responses would you anticipate after extended acclimation periods to high elevation?

Answer 126

- After a few days, there is increased release of 2,3-DPG into circulation which increases P50 (offsetting effects of pH change) - Over similar/slightly longer time frame, body responds with increased EPO levels which encourages erythropoiesis (production of RBCs). Higher RBC levels make up for the lowered affinity of Hb caused by 2,3-DPG

Question 127

Why would athletic training at higher elevation be beneficial?

Answer 127

High altitudes have less abundant oxygen. So in your blood you have higher CO2:O2 levels than usual, thus pH decreases. In order to counter that 2,3-DPG is bound to Hb, decreasing it's affinity for O2 (Bohr shift right) so that O2 levels increase, raising and balancing out the pH. However the decreased affinity means erythropoeisis must be stimulated so that there are more available RBCs that can take up oxygen, making the saturation of blood:oxygen levels higher and returning to normal. This high RBC count will remain temporarily after training so you have more RBCs thus more oxygen can be carried into your blood (affinity increases because the pH balance no longer needs to be countered). More oxygen in your blood means increased cellular respiration capabilities

Question 128

What is erythropoiesis?

Answer 128

Is your body's process of making red blood cells (erythrocytes). Erythropoiesis ensures you have the right number of blood cells — not too few or too many.

Question 129

How do buccal oscillations occur in some fish and amphibians?

Answer 129

1. Floor of the mouth is lowered; buccal cavity is expanded; air flows through the nares (nostrils) into the bottom of the mouth. 2. Glottis opens; air flows from the lungs across the top of the mouth and out of the nares. 3. Floor of the mouth is raised; buccal cavity is compressed; air is pumped into the lungs; the glottis closes. 4. Buccal cavity expands, drawing air from lungs 5. Buccal cavity raises, expelling air from mouth

Question 130

____ _____ found in some fish means they must propel themselves through water to push it through their gills for respiration

Answer 130

Ram ventilation

Question 131

Describe the ventilation oscillations that occur in birds, mammals and some reptiles? (axial musculoskeletal oscillations)

Answer 131

Inspiration (diaphragm lowers, rib cage expands via contraction of external intercostals) creates negative pressure in lungs because pleural space (between ribs and lungs) cannot expand (fluid filled). Exhalation causes rise in diaphragm and contraction of internal intercostals compresses rib cage.

Question 132

What is the difference between anatomical and physiological deadspace?

Answer 132

Anatomical: - The volume of oxygen which is not used in gas exchange, it never even reaches the alveoli, it is just taken into the respiratory system and then expired without change Physiological: - Physiologic dead space includes all the non-respiratory parts of the bronchial tree included in anatomic dead space, but also factors in alveolar deadspace (unperfused alveoli)

Question 133

What is the difference between functional residual capacity (FRC) and residual volume (RV0 in the lungs?

Answer 133

FRC is the volume of air left in the lungs at the end of a normal expiration. It is the combination of residual volume (RV) and the expiratory reserve volume. RV is the amount of air that cannot be expelled from the lungs at the end of a forced expiration.

Question 134

What is the difference between expiratory and inspiratory reserve volume?

Answer 134

The inspiratory reserve volume is the amount of air a person can inhale forcefully after normal tidal volume inspiration; the expiratory reserve volume is the amount of air a person can exhale forcefully after a normal exhalation

Question 135

What is Ficks equation?

Answer 135

Question 136

Describe countercurrent in terms of respiration

Answer 136

- Between the alveolar sacs and blood - Countercurrent = two factors (CO2, O2) move in opposite directions of eachother during exchange interaction - In respiration, O2 from alveoli move oppositely (to blood) than CO2 from the blood (to alveoli) - Eventually the CO2:O2 ratio in both blood and alveoli will be equal, thus diffusion gradient fades and no more net movement occurs. More in depth: Concurrent exchange is a reasonable approximation of gas exchange. Inhaled air comes into alveoli sacs where the pulmonary circuit comes from the heart and exchanges deoxygenated air for oxygenated air. Blood will have low CO2, and the air will have comparatively high PO2, the difference will drive the diffusion of oxygen. As that blood moves from arteriol → ventricle the blood is losing oxygen, and after a while the oxygen levels in both the sac and the blood will be about equal which in turn reduces the gradient of diffusion until there is no more net diffusion. Countercurrent exchange, like in gills. In this system water moves through the buccal cavity past the gill arches. However the blood flow, deoxy comes from the edge of gill arch → upstream, relative to water flow, towards the head of the fish then to the rest of the circulation. Water and blood flow in opposite directions

Question 137

What is Hypoxic Pulmonary Vasoconstriction (HPV):

Answer 137

- Arterioles feeding areas of lung that are hypoxic (oxygen lacking) constrict, reducing blood flow to that area, this means that they divert blood from the unperfused alveoli sacs (think physiological deadspace) to alveoli that actually have oxygen present - In hypobaric hypoxia (low PP of O2 in environment because of lower total air pressure at high elevation), all of pulmonary circulation gets constricted (lung uniformly hypoxic). This increased resistance to flow raises pressure Note: Tibetans show blunted HPV response compared to lowlanders (they're already adapted so they won't need to "adapt" as much)

Question 138

Describe cross current (counter and concurrent) exchange in bird respiratory systems?

Answer 138

- Air Sacs are air storage areas ensure unidirectional flow of air through parabronchi (the main site of gas exchange) because the air doesn't need to be exhaled for the gas exchange to occur - Birds inhale by expanding their rib cage and exhale by compressing their rib cage - Very efficient system, needs to be because of the massive oxygen demand of flight, and the low oxygen supply at high altitudes Note: Tarzan couldn’t breathe through a reed because of the long area of dead space added to breathing. That tube is hard to pass clean fresh air through and remove old air from. This means in swans with long ass necks (kinky) have to work harder to pump the air through that.

Question 139

Define osmotic pressure?

Answer 139

Pressure needed to offset movement of pure solute across semipermeable membrane

Question 140

Define Hydrostatic pressure?

Answer 140

- The pressure a fluid physically exerts on surroundings - Can be due to pull of gravity - E.g Pressure of blood on vessel wall

Question 141

Pressure ____ with depth Water moves from ____ conc to ____ conc

Answer 141

increases high low

Question 142

Hypotonic solution means there's more ionic concentration ____ the cell than ____ of the cell and water is drawn into the cell Hypertonic solutions means there's more ionic concentration ____ of the cell than ____ and water leaves the cell 5

Answer 142

WITHIN OUTSIDE OUTSIDE WITHIN

Question 143

Intake and secretion of water requires both ____ water osmosis and _____ osmosis in the body

Answer 143

obligatory regulated

Question 144

The extracellular environment is higher in _____, the intracellular environment is higher in _____

Answer 144

sodium potassium

Question 145

If you were to fast you would die of dehydration ______ because you have much ____ water loss than nutrient loss

Answer 145

far sooner more

Question 146

What is most responsible for leakage in the lymphatic nodes and capillary beds?

Answer 146

- There's a similar osmotic gradient in the lymph (fluid) and interstitial fluid, this implies that there is similar electrolyte concentrations between the two, so any leakage would be due to hydrostatic pressure forcing the lymph out of the nodes

Question 147

What is interstitial fluid?

Answer 147

The body fluid between blood vessels and cells, containing nutrients from capillaries by diffusion and holding waste products discharged by cells due to metabolism. 11 liters of the extracellular fluid are interstitial fluid and the remaining three liters are plasma.

Question 148

Describe electrolytes

Answer 148

Electrolytes are essential for basic life functioning, such as maintaining electrical neutrality in cells and generating and conducting action potentials in the nerves and muscles. Significant electrolytes include sodium, potassium, chloride, magnesium, calcium, phosphate, and bicarbonates

Question 149

Fill in the blanks

Answer 149

Question 150

The air around us compared to our lungs is much ____ humid which means that via respiration we ____ humidity

Answer 150

less lose

Question 151

What does something mean when it says iso-osmotic urine conc relative to blood?

Answer 151

It suggests that there is little focus on conc within the urine. It doesn’t look like there is substantial modification of urine production with respect to osmotic balance (contributes little to homeostatic maintenance) . You could predict that the osmolarity in the urine would be similar what it started off as in the blood when the serum enters the kidney

Question 152

What does it mean when something says hypo-osmotic blood conc. relative to the environment?

Answer 152

- ECF is also hypo-osmotic - Animal should tend to lose water from its plasma to the environment and conversely a gradient for ion uptake into the body from the environment. In order to replace the water that it’s losing the animal must drink sea water and then actively draw out the ions and secrete them through their gills - Water loss, ion gain

Question 153

Do hyperosmotic blood conc relative to environment fish drink water?

Answer 153

Their blood has high electrolyte composition and low water, so they want to lose electrolytes via urinitation to balance it out. So their urine is super concentrated (high electrolyte, low water) thus they retain a lot of water and do not need to drink much if any (metabolic water production may be sufficient)

Question 154

Do desert animals drink water?

Answer 154

Desert animals don’t drink water, rather they rely on their metabolic water. Their urine concentration is hyperosmotic in relation to the plasma (blood)

Question 156

Do marine birds drink water?

Answer 156

Marine birds drink seawater. Their urine is hyperosmotic to their blood, because they must limit their loss of water to their environment. They have hyperosmotic salt-glands

Question 157

Describe Respiratory Evaporative Water Loss:

Answer 157

- Gas exchange between environment and tissues must occur in MOIST membranes because the oxygen must first be dissolved before going through tissues. Thus when you inhale, the air from environment is originally not as humid as it will be in your lungs. - Air comes in, is warmed and water must be evaporated into the air to humidify it. When we breathe it back out we can recoup a portion of the water but some of it is lost - You would lose less water in humid jungles, lose more in cool deserts.

Question 158

What are the two types of nephrons in the mammalian kidney?

Answer 158

1. Juxtamedullary: Nephron is found mostly in the cortical section but is partially juxtaposed into the medullary section as well. Juxtamedullary nephrons (15% of nephrons) concentrate and dilute urine 2. Cortical: Nephron is found entirely within the cortex/cortical area. Cortical nephrons (85% of all nephrons) mainly perform excretory and regulatory functions

Question 159

There is ____ plasticity in the ability of your respiratory system to reduce water loss in arid environments, but you can modify the _____ of your ____ to change or limit the rate of water loss (in birds). This is done by altering specific lipids, ceramides and cerebrosides

Answer 159

less makeup skin

Question 160

What are two stores for water?

Answer 160

1. Fat: * Carb stores (glycogen) are hydrophilic (take in water). However lipids themselves are hydrophobic * Energy: fat is good because it is dense energy source * Water: fat is good because it liberates 1.5 X as much water for each ATP made 2. Protein: * The catabolism and oxidation of protein yields five times more metabolic water than that generated through fat oxidation alone * Done mostly by birds, when migrating because drinking water is not an option as their journeys do not cease. So they catabolise lean mass in their flight muscles, which provides them water but also makes them lighter, easing their energy expenditure for flight

Question 161

Do hummingbirds become dehydrated?

Answer 161

- Don’t become dehydrated during the day because they’re constantly drinking - Have small kidneys because during the day there isn’t much water to urine conversion - Must produce dilute urine and maximise glucose reabsorption But at night, dilute urine production while fasting imposes dehydration danger - Hummingbirds dramatically reduce glomerular filtration rate (GFR) during night and turn off their kidneys

Question 162

What is the process of glucose and amino acid intake?

Answer 162

- Very similar to carb absorption in intestine 1. An Na/K ATPase pumps K from peritubular fluid (between baso mem and capillary) to inside the basolateral membrane, and Na oppositely. Consumes ATP but creates a diffusion gradient 2. Since the basolateral membrane Na conc. is now low, the cotransporter SGLT2 facilitates the diffusion of Na into the baso mem from tubular fluid (from high to low) and also draws in glucose with it. 3. Now glucose conc. is high in baso mem. but low in capillary so the GLUT2 complex pumps the glucose into capillary (high to low)

Question 163

Describe blood pH regulation

Answer 163

1. Carbon dioxide is exchanged from tissues into the blood 2. Carbonic anhydrase (CA) combines CO2 with water to form HCO3 + H 3. The H+ ion is pumped out of cell by a Proton ATPase pump, into tubular lumen 4. The HCO3 is pumped into the blood by a Cl-antiporter, Cl enters the cell from the blood as the exchange 5. Na is pumped from tubular lumen into cell, 6. Lumen is now acidified and positively charged, enhancing the electrochemical gradient for Na into the cell 7. To decrease the CO2 levels we can either expire more CO2 (shift right) or the kidney can filter out H ions, and reabsorb the HCO3. Less H+ means equation shifts left, returns to equilibrium Note: This equation is at equilibrium, meaning that the conc. of both sides is equal at all times. The ratio is 1:1<-->1:1, but say CO2 is at higher levels (0.8:0.2) it shifts the equation to the other side, leading to increased conc. of both products on the other side

Question 164

How does urine help buffer H+ and regulate pH?

Answer 164

- Nitrogenous waste products are filtered from the blood and excreted into urine - The H+ ions from either the bicarbonate (in blood-pH reg.) or from the breakdown of NH4 --> NH3 + H, are pumped into the urine. - To avoid the urine pH getting to acidic due to influx of H+ ions, the ions combine with NH3 or HOP2 in the urine, which buffers them and reduces their impact on the pH level Note: If pH < 4.5 the H+ ATPase pump won't work, that's why the pH balance is important.

Question 165

How does vasopressin regulate blood pressure?

Answer 165

- Regulation of BP is intimately intertwined with the kidney 1. Osmoreceptors in the hypothalamus detect high plasma osmolarity (High electrolye, low water) OR stretch receptors & baroreceptors detect low BP 2. These factors stimulate vasopressin (aka ADH) which increases the water reabsorption of the collecting duct by increasing number of aquaporins (holes), this concentrates the urine - Retaining more water and excreting more ions increases your blood pressure and lowers plasma osmolarity

Question 166

What are aquaporins?

Answer 166

Pores in the collecting duct membranes of the kidney which allow water to pass through

Question 167

- ADH production is ____ by alcohol consumption - ADH production is ____ by increasing plasma osmolarity detected by _______ in the hypothalamus - ADH production is ____ by increasing blood pressure detected by ____ receptors in atria and ______ in carotid and aortic bodies

Answer 167

Inhibited Stimulated Osmoreceptors Inhibited Stretch Baroreceptors

Question 168

How does vasopressin stimulate the formation of aquaporins?

Answer 168

Question 169

Define hypertension

Answer 169

When you eat too much Na it raises the [Na] in the plasma. This offsets the osmolarity balance, thus more water is retained in the plasma to dilute the Na, returning osmolarity to regular levels. However more water means higher hydrostatic pressure which means increased blood pressure which is not bueno Note: Hypertension = high blood pressure

Question 170

How is secretion of renin controlled in three ways

Answer 170

1. Baroreceptors in juxtaglomerular cells release renin in response to low blood pressure 2. Sympathetic neurons in cardiovascular control centre of medulla oblongata trigger renin secretion in response to low BP 3. Macula densa cells in distal tubule respond to decreases in flow by releasing a paracrine signal that induces juxtaglomerular cells to release renin

Question 171

What is the process of the Renin-Angiotensin-Aldosterone blood pressure regulation?

Answer 171

1. Renin secreted from juxtaglomerular cells when blood pressure or glomerular filtration rate (GFR) lower than normal 2. Renin converts angiotensinogen (-gen means precursor and inactive form) to angiotensin I 3. Angiotensin converting enzyme (ACE) on epithelia of blood vessels converts angiotensin I to angiotensin II 4. Angiotensin II causes synthesis and release of aldosterone from adrenal cortex 5. Aldosterone stimulates Na+ and water reabsorption from filtrate and enhances K+ excretion

Question 172

Broadly speaking, what two mechanisms of the R-A-A pathway regulate blood pressure?

Answer 172

1. Angiotensin II acts as a vasoconstrictor which raises blood pressure by increasing resistance to flow 2. Aldosterone increases Na+ (and water) retention Raises blood pressure by increasing blood volume

Question 173

What is electrical resistance?

Answer 173

Resistance {R} (Ohms - Ω): opposition to the passage of current

Question 174

What is electrical current?

Answer 174

Current (I) (Ampere – A): the flow of charge e.g. movement of electrons (e-) e.g. movement of other ions (Na+, H+, Ca++, Cl-, etc.)

Question 175

What is electrical voltage?

Answer 175

Voltage (V) (volts – V): - the “pressure” that pushes electricity between 2 points across a membrane

Question 176

Mathematically, how do current (I), voltage (V) and resistance (R) connect?

Answer 176

Ohms law: I = V/R

Question 177

What is the difference between direct current (DC) and alternating current (AC)?

Answer 177

- Direct current (DC) there is a continuous flow of charge from the cathode (-) to the anode (+) - In alternating current (AC) the flow moves in one direction and slows down at some point and then turns back around e.g action potentials Note: Some biological phenomena behave like DC currents. e.g. Blood pressure (acts LIKE a DC current – flow of fluid, not charge)

Question 178

Describe Cycle frequency (Hertz)

Answer 178

- Hertz (Hz) is a unit of frequency of complete cycles per second. The term Hertz applies to changes in state or cycle in a sound wave, alternating current or other cyclical waveforms - 120 BPM = 120 pumping cycles = 2 Hz / 60 seconds

Question 179

Describe the flow of ions

Answer 179

- They will move down chemical (concentration) AND in response to electrical (charge) gradients - These gradients (and resulting motive forces) can be in same OR opposite directions Note: Mass is important. Remember that in some small vertebrates we saw an elevated rate of paracellular nutrient transport rate across the cell walls. The rate that this occurs is inversely proportional to the mass of the chemical moving, thus smaller things move more quickly than larger things.

Question 180

Imagine two solutions of KCl, one has 0.1M (left) and the other 0.01M (right), they are initially charge balanced, which means no electrical gradient. They are also separated by an impermeable membrane between them. Now imagine you made that membrane permeable to potassium only, what would you expect to observe?

Answer 180

You would expect K to move down conc gradient from the left side to the right side because the right side is ten times less concentrated and thus it goes from low to high. After that it will soon reach an equilibrium where the net electrical gradient driving the K from right to left is balanced by the net conc gradient driving K down the gradient from left to right. Overall there is very little movement of K. Note: The membrane between left and right acts as a capacitor, allows charge organisation on either

Question 181

Inside of cell usually has ____ potassium levels, and ____ chlorine levels than the outside

Answer 181

higher lower

Question 182

Describe leak channels

Answer 182

Leak channels are open channels during rest in axons or muscle tissues

Question 183

What is the equation for the work required to move ions across a chemical gradient?

Answer 183

Question 184

What is the equation for the work required to move ions across an electrical gradient?

Answer 184

Question 185

What is the Nernst Equation

Answer 185

Question 186

What is the Goldmans Equation

Answer 186

Question 187

Describe compound action potentials

Answer 187

CAP is the SUMMED action potentials from many individual nerve cells When the motoneuron discharges one action potential, it makes all its muscle fibres fire. When you record this activity from the muscle, you are recording superimposed action potentials (summed APs) of all muscle fibres firing simultaneously. The recorded activity is the “compound action potential”.

Question 188

Describe single action potentials

Answer 188

An action potential is a rapid and brief change in electrical potential that travels along the membrane of a neuron. It is a key mechanism for transmitting signals in the nervous system.

Question 189

TESTABLE: Compare single and compound action potentials

Answer 189

Single AP are as it implies, just the AP. The CAP is all associated APs that are fired from a neuron, added together to form one massive AP

Question 190

What is the minimum stimulus intensity?

Answer 190

Intensity necessary to trigger at least one (or few) axon(s) to fire AP

Question 191

What is the process of the full hodgkins cycle (one full AP)?

Answer 191

1. Depolarisation: * If a stimulus is strong enough to cause the resting potential to rise to the threshold potential an AP begins * This phase, the rising phase, is characterised by the influx of Na+ ions through channels into the neuron causing the interior to become more positive than the outside 2. Repolarisation: * This positive accumulation inside the nerve cell stimulates the opening of K+ ion channels and closing of Na+ channels. * K+ leaves the cell, making the interior less and less positive, bringing it back towards it's resting potential 3. Refractory Period: * The repolarisation period actually overshoots past the resting potential, making the cell more negative than it should be * K+ gates close, some Na+ gates open and some Na+ flows back into the cell, raising the potential until it returns to the resting potential

Question 192

Define equilibrium potential

Answer 192

Equilibrium Potential = the membrane potential at which there is NO net movement of a specific ion across membrane

Question 193

Is the Na/K ATPase pump directly responsible for the repolarisation of a nerve after an individual action potential?

Answer 193

- Na+/K+ ATPase pump NOT directly responsible for repolarization after individual action potential - Na+/K+ ATPase pump helps to maintain ion concentrations. It is activated by ↑[Na+] in & ↑[K+] out (e.g. due to APs) but it takes many APs before pump activity increase is noticeable Expanded explanation: So the idea is that the cell has a big volume inside of it (akin to a swimming pool of water and ions) and AP are tiny little lapping waves occurring at the edge of the pool. The edge of the pool is the capacitor for water to air, the same way that membrane is a capacitor for charge across the membrane. You can have fluctuations occur but no actual detectable difference in the water and salt levels of the pool itself. Thus the amount of ions moving that are responsible for an individual AP at a given portion of the membrane that fires once, is just a drop in the bucket compared to the acc distribution of ions across the membrane. It would take dozens of AP firing in a row until you would see a really pronounced increase in Na/K ATPase pumping rate because the pump is not DIRECTLY responsible, it just helps maintain.

Question 194

What is the difference between absolute and relative refractory periods?

Answer 194

Absolute: - Period of time during which AP cannot be triggered (no matter stim. intensity) - Membranes of all axons (at stim. electrodes) are in a refractory state and won’t fire - No Compound AP - Too many inactivated Na+ channels for successful Hodgkin cycle (AP) Relative: - Period of time during which excitability is reduced (threshold is higher and resulting AP is weaker) - Membranes of some axons (at/near stim. electrodes) are in a refractory state and won’t fire - Smaller Compound AP (fewer summed APs) - Only some of Na+ channels ready…so Hodgkin cycle is harder to get started (higher threshold), AP is less intense

Question 195

If depolarization from stimulus occurs only slowly, threshold for triggering AP will be ____ The slower the depolarizing stimulation is applied, the ___ synchronised’ the opening of voltage gated ion channels is

Answer 195

higher less

Question 196

What is a local response in a nerve cell?

Answer 196

Local response: stim. just barely shy of threshold; some voltage-gated channels open… but not enough for full AP to be elicited

Question 197

How does ion channel refractory behaviour makes AP propagation unidirectional from site of initiation?

Answer 197

1. Imagine a transect down the neuron, and you’re looking at Na channels along the way. There is a net influx of sodium and the hodgkin cycle going strong. The channels beyond the first are still closed because their microenvironment has not become depolarised to the threshold. However with the influx of Na diffusing away down the membrane, the wave will cause depolarisation at site #2 which allows it to begin firing and starting its hodgkin cycle. 2. Now the original channel which is now UPSTREAM has begun its refractory period. So even though now there is an influx of positive current into the cytosol and along the membrane in both directions, upstream and downstream. The downstream is ready to go, it is able to respond to the depolarisation whereas upstream they are not ready for that signal yet, thus the depolarisation proceeds unidirectionally downstream. 3. This process repeats and makes up the action potential

Question 198

How does myelination occur?

Answer 198

- Oligodendrocytes have appendages that reach out and wrap around axons. They are the myelin sheath producing cells in the central nervous cells, in the peripheral nervous system they’re called schwann cells. - Myelination only occurs in segments, leaving spaces between them. The spaces between are the nodes of ranvier. This is where the axon has the ability to exchange a lot of ions with the extracellular compartments. Where the axon is wrapped with myelin sheath there is limited ion exchange. The voltage gate transporters are usually excluded from these areas but clustered and dense in the nodes of ranvier.

Question 199

What do myelin sheaths do?

Answer 199

Myelin sheaths: - Increase membrane resistance (𝑟𝑚) to change flow (leak) - Reduce membrane capacitance (organisation of charge along membrane) – charge flows better along axon Note: Threshold is so high where myelin is, APs can only occur elsewhere (at Nodes of Ranvier) Explanation: Imagine an 100m field. The goal is to throw a ball from one side to the other (pass an AP along). Each person can throw the ball 20m (upstream depolarisation distance). And each time the ball is caught and thrown to another person it takes 5 seconds (time it takes for an AP to fire). So in order to maximise efficiency you would space people (nodes of ranvier) every 20m so it takes only five (100/20) tosses to reach it's destination, and in total takes 25 (5pplx5seconds) seconds for this process to occur. Now imagine instead you placed people every 10ms (more nodes of ranvier, less distance between) it would take 10 throws and 50 seconds to get the ball to the other side.

Question 200

Describe saltatory conduction

Answer 200

When there is a hodgkin cycle occurring in a node there is an influx of positive charge which diffuses both ways in the membrane but can only successfully cause a hodgkin cycle to continue downstream.

Question 201

What are the steps of saltatory conduction?

Answer 201

1. An action potential is generated 2. Na+ enters the axon and spreads toward the next node 3. Elevation of intracellular [Na+] depolarizes the membrane at the next node causing voltage-gated Na+ channels to open there (AP). 4. APs “jump” or “leap” from node to node – hence, ‘saltatory’ conduction

Question 202

Potential exam: What would happen if you shortened / lengthened the width of myelin sheaths / the distance between nodes of ranvier?

Answer 202

- If you make them too far apart then they’ll pass the length constant and won’t be able to transduct any further - If you make them shorter then the AP travels more quickly down the axon

Question 203

Describe electrical synapses

Answer 203

https://www.youtube.com/watch?v=pKgHV0b7ZHYNote

Question 204

How do electrical synapses work?

Answer 204

Question 205

What are rectifying electrical synapses?

Answer 205

Question 206

Why do graded potentials travel short distances?

Answer 206

Question 207

What are graded potentials?

Answer 207

Graded potentials are changes in membrane potential that vary according to the size of the stimulus, as opposed to being all-or-none (APs)

Question 208

Explain a fast chemical synapse (4 steps)

Answer 208

1. Presynaptic axon terminal at rest separated by synaptic cleft. All ligand channels are closed and not bound. Vesicles closed. 2. Action potential arrives, vesicles fuse with terminal membrane, depolarization occurs. Voltage-gated sodium at nodes of Ranvier opens alongside potassium channels. Free intracellular Ca is low at this point → causing brief rise in intracellular Ca levels due to external influx. 3. The transmitter binds to postsynaptic receptor proteins. Ligand-gated and ion channels open on the postsynaptic membrane to allow transmission. (this must happen fast or else ligand-gated channels will keep opening → hyperpolarization) 4. The transmitter removed from cleft, fused membrane recycled.

Question 209

Acetylcholine causes a ____ excitation and _____ inhibition. GABA (y-aminobutyric acid) causes a ____ inhibition and ____ inhibition in terms of speed for fast chemical synapse

Answer 209

Fast, Slow Fast, Slow

Question 210

What is the antagonist of the neuroreceptor acetylcholine (ACh) and how does it work?

Answer 210

Nicotinic synapse: ACh OR Nicotine bind to Nicotinic-ACh receptors causing the gate to open and then subsequent depolarization of the postsynaptic membrane. The gate closes after the influx of potassium and sodium. If there is no ACh or Nicotine on the channel, it will remain closed.

Question 211

The equation for Electromotive force (EMFx)

Answer 211

EMFx= Vm- Ex Vm is voltage of the membrane, Ex is the equilibrium potential for the x ion. (-) EMF means net positive moving inward toward equilibrium potential (+) EMF means net positive moving outward towards equilibrium potential

Question 212

Equation for ionic conductance (Ix)

Answer 212

Ix = gx (EMFx) Ionic current = magnitude of driving force multiplied by inverse of resistance (gx)

Question 213

Explain reverse potential

Answer 213

When current Ix for one ion is equal and opposite to the other Erev = (½) (Ex+Ey)

Question 214

Explain slow chemical synapse (3 steps)

Answer 214

- Happens when the neurotransmitters of pre are too large for the receptors of the ion channels on post 1. The neurotransmitter binds to an accessory receptor 2. This causes the activation of G-protein complex 3. Complex sends message to ion channel to open/close This is what makes it slow, compared to the fast synapse. Because the fast neurotransmitters just bind right to the ion channel, causing it to open. But in slow synapses there is this extra step involved between receptor binding and ion channel opening

Question 215

What is neurotransmitter recycling

Answer 215

This is the extension of the slow synapse. For sustained neuronal signaling, neurotransmitters are recycled after release from neuronal terminals. During this process, perisynaptic glial cells take in and convert neurotransmitters such as glutamate, GABA, and histamine into inactive metabolites for transport.The inactive forms are packaged into vesicles. Vesicles get transported back to place/neuron of origin (recycled)

Question 216

What are the 4 functional neural zone

Answer 216

1. Signal recognition (dendrites, change membrane potential) 2. Signal integration (axon hillock, signal converts to AP) 3. Signal conduction (Axon, where AP travels down the axon) 4. Signal transmission (Axon terminals, release of electrical synapse) Acronym Racist Individuals Cause Turmoil

Question 217

How does signal get integrated in the cell?

Answer 217

A combination of AP’s in the same soma will stack in order to remain above threshold in post synaptic membrane. The density of Na channels is proportionate to how excitable the cell is. High density of channels = less need to be open for AP and AP generating threshold is lower

Question 218

Excitatory synapse (epsp) causes a post synaptic membrane to _______ Inhibitory synapse (ipsp) causes membrane _________

Answer 218

Depolarize hyperpolarization…. Note: the total AP can be measured by taking the energy of both

Question 219

Explain spatial summation

Answer 219

Question 220

Explain temporal summation

Answer 220

The sum of a single synapse activating several times very fast (rapid succession) Note: So rather than the buildup of a stimulus caused by the sum of small stimuli provided by many axons, it is the sum caused by the rapid firing of a single axon

Question 221

Neuronal plasticity is defined as the modification of neuronal function as a result of (1______) and (2______). (1) happens when _____________________, this can be in a singular synapse and happen during something like ____ _____. (2) happens when there are changes in the presynaptic activity influenced by ____________, an example of this is a _________.

Answer 221

Homosynaptic modulation; Heterosynaptic modulation Activity in the terminal itself causes change in the neurotransmitter release; temporal summation Another closely related axon terminal; slow synapse

Question 222

True or false, the rapid firing of AP demands less Ca influx for successive firing

Answer 222

False, higher Ca influx is needed for the following pulse to reach successive AP.

Question 223

What are the roll of sensory receptors, what are the different types?

Answer 223

They turn external signal into internal responses. They transduce incoming stimuli into changes in membrane potential. Receptor detects stimulus, opens channel, AP to CNS There are Chemoreceptors, mechanoreceptors, photoreceptors, electroreceptors, magnetoreceptors, thermoreceptors.

Question 224

How is the molecular mechanism changed in result to external stimulus

Answer 224

1. Structural change in transmembrane proteins 2. Activation of G-protein complex results in modification of IOn channel permeability 3. Net ion flux is affected Note: this is the same as a slow synapse

Question 225

Salt flavor is from opening of _____ Bitter/sour taste is from opening of ____

Answer 225

Na channels, K channels

Question 226

Stimulus modality is _____ Stimulus location is _____ Stimulus intensity is _____ Stimulus duration is _____

Answer 226

What is being detected, where it is in external environment, tonic, phasic

Question 227

Explain the difference between tonic and phasic receptors

Answer 227

- Tonic encodes for the information of magnitude. It produces AP’s as long as the duration of the stimulus, AP frequency decreases when stimulus is maintained for a long time - Phasic is the coding information for the rate of change in the stimulus. Phasic receptors activate only when stimulus is received and/or removed. Ex: how fast sound is approaching.

Question 228

What are vertebrate proprioceptors

Answer 228

Proprioception is the internal sense of body position, and proprioceptive control of locomotion is essential to generate and maintain precise patterns of movement or gaits. This proprioceptive feedback system is conserved in many animal species and is mediated by stretch-sensitive receptors called proprioceptors.They are our ability to sense ourselves through motor and sensory nerves. They are crucial in playing a role in negative feedback reflexes influencing muscle tone. Eg: muscle spindles

Question 229

What is the role of muscle spindles

Answer 229

They make connections to muscle fibers which send a negative feedback signal as the muscle lengthens or shortens. This stops muscles from over flexing, causes muscle to relax.

Question 230

What is the organization of the skeletal muscle

Answer 230

Tendon connects muscle to bone. Muscle cells are multinucleated. Myofibril is where the change in length occurs (where the actin and myosin are)

Question 231

Explain the structure of the sarcomere

Answer 231

- Made of thick and thin filaments (actin and myosin/troponin). Each thick filament reacts with 6 thin, each thin reacts with 2 thick. - From z-z line - I band has no thick filaments, gets shorter in compression - A band cannot shorten - H zone is region where thin exists without thick, shortens in compression

Question 232

Within a 10cm length; if there are many sarcomere divisions the muscle will contract _____ with _____ force. If there are few sarcomere divisions the muscle will contract ____ with ____ force. Note: long sarcomeres have ____ cross bridges which allow more force.

Answer 232

Fast, less Slow, more More

Question 233

The three major compartments of the muscle besides plasma are …

Answer 233

Myofibrils, sarcoplasmic reticulum, mitochondria

Question 234

Explain the process of Ca+ release from the sarcoplasmic reticulum (6 steps)

Answer 234

1. Depolarisation (along t-tubule) causes conformational change in DHP-R receptor (very brief), thus Ca release increases dramatically 2. Increased free calcium results in more being bound to troponin. With more Ca2+ bound there is a conformational change and troponin interacts with tropomyosin to move it from its resting position next to actin which was blocking access to myosin-binding site 3. Myosin is now free to bind to actin, initiating cycles of cross-bridge formation release 4. As soon as there is an increase in free calcium, there is an increase in Ca-ATPase pump activity 5. Increased Ca-ATPase pumping lowers free calcium levels, resulting in less Ca being bound to troponin - this results in conformational changes that lead to tropomyosin moving back into place blocking access to the myosin binding sites on actin 6. Once the myosin binding site is blocked, the cycle of cross-bridge formation-release occurs ## Footnote https://www.youtube.com/watch?v=4ihWJ0TKn-g

Question 235

Explain the cross bridge formation-release (4 steps)

Answer 235

Begins with muscle at rest 1. Myosin with ADP - Pi bound is ready to bind to actin 2. Actin site becomes available with increase of free intracellular Ca levels. Myosin binds to actin, this is a very weak bond 3. The free Pi that was bound to ADP dissociates from the complex, creating a strong bond and a power stroke (shortening of sarcomere) 4. ADP dissociates letting a new ATP to bind to the actomyosin complex. This causes the myosin head to break from actin (crossbridge release)

Question 236

Rigor mortis is when…

Answer 236

There is no ATP to be given to the muscle (4th step of cross bridge formation-release). This means that the 4th step cannot occur, this causes permanent stiffness, Ca+ stays inside the cell.

Question 237

What are some of the rules of muscle contractions

Answer 237

There is a maximum muscle flexion that has no correlation to Ca or voltage (the muscle won't contract more even if there is an excess). There is also a latent period that occurs in between the AP and the tension (delay from AP to movement). This occurs because of different types of movement such as Ca+ through T-tubules

Question 238

What is the major idea of twitch kinetics

Answer 238

A single stimulation will cause a single twitch when a single ESPS can raise the voltage membrane past the threshold.

Question 239

Low frequency APs have ____ summation of tensions that have partial relaxation between twitches. High frequency APs have _____ summation of tensions which have little to no relaxation between twitches.

Answer 239

Low; High

Question 240

What is the length-tension relationship

Answer 240

The relationship between the overlap of thick/thin filaments to the force of the sarcomere. The longer the sarcomere, the more force it has. (means that stretching improves force generation)

Question 241

What is the velocity-power relationship

Answer 241

Relationship between how fast the muscle contracts to how much force is generated. Power = (change in length)(force)(time) The faster it contracts, the shorter the length of sacromeres, the less force is generated

Question 242

What is EMG, what can it do, what are the expected trends between white and red fibers at different activity levels; slow, burst, fast swimming

Answer 242

Stands for Electomyoscopy, used for measuring power voltage in muscles. The higher the EMG means there was more force, longer EMG means longer muscle activation. During slow swimming - red muscles are used, no activity in white fibers Burst - Activation of all muscle types Fast swimming - white muscles are major contributors, red barely used.

Question 243

What are the major differences of red and white muscle fibers

Answer 243

Red fibers have more mitochondria for aerobic metabolism, long lasting, lots of capillaries, shorter sarcomeric division. White fibers have low mitochondria, anaerobic, longer and faster for more power, fatigue quick, glycolytic, M-ATPase more prevalent.

Question 244

If a muscle fibre is composed of: Most type 1(red) and least type 2b (white) it means ______ When type 2b is most rapid and type 1 is least active that means ______ Most type 2b and least type 1 causes _____

Answer 244

Fatigue resistance Twitch kinetics Force production

Question 245

Type 1 muscle fibers are ____, type 2a fibers are ______, type 2b fibers are ______

Answer 245

Slow twitch, oxidative; fast twitch, oxidative-glycolytic; fast twitch, glycolytic

Question 246

What is the process of smooth muscle contraction?

Answer 246

Question 247

What are the two types of striated muscle, what is their difference

Answer 247

Phasic and Tonic, they differ in innervation, force dynamics and excitation.

Question 248

Explain phasic and tonic MUSCLE

Answer 248

Phasic - One twitch that activates AP, used in force production, high density ACh receptors compared to the rest of the sarcoplasmic membrane Tonic - Kept on by constantly receiving graded potentials, white fibers have NMJ along their entire length, they need to have enough summation to generate sufficient calcium for graded potential to occur. Note: Note: Only striated muscles shrink and lengthen, smooth just sink

Question 249

What are the different areas of possible muscle fatigue, explain each

Answer 249

At the NMJ: There is an incomplete neurotransmitter release, receptor activation decreases which changes the membrane potential in the muscle At the muscle cell: not enough energy (no ATP), glycogen storage gets depleted with excess exercise, lowers performance of the entire muscle.

Question 250

How does cholesterol affect fluidity of a membrane?

Answer 250

At high temperatures, cholesterol acts to stabilize the cell membrane and increase its melting point (decreased fluidity) While at low temperatures, it inserts into phospholipids and prevents them from interfering with each other to avoid aggregation (increased fluidity)