extenta djurfysiologi

What is Creatinine phosphate?

The most common type of phosphagen that is stored in the body. It is energy rich phosphate bonds and can be used to create ATP in anaerobic enviroments

chatgpt: Creatine phosphate (CP), also known as phosphocreatine, is a high-energy phosphate compound stored in muscle cells. It serves as an immediate energy reservoir for ATP synthesis during short bursts of high-intensity activity by donating its phosphate group to ADP in a reaction catalyzed by creatine kinase. This process is anaerobic and occurs rapidly, allowing for quick regeneration of ATP. However, CP stores are limited and deplete within seconds during intense muscular effort.

What is basal metabolic rate?

Basal Metabolic Rate (BMR) is the number of calories your body needs to maintain basic physiological functions while at rest, such as breathing, circulation, cell production, and temperature regulation.

Mostly used on mammals

What is lactic acid and VO2max?

Lactic acid is the end product of anaerobic glycolysis when the O2 is not sufficent to create ATP aeroicly.

VO2max is the maximal O2 uptake of an individual.

Explain a experiment to

a) demonstrate the existence of a endogenous free-running circadian rhythm

b) how an external zeitgeber entrains the endogenous rhythm

a) if you observe an animals active and awake behaviours during day, with a natural daylight circle. Then see their inactive sleeping behaviour in the dark, with a natural 24h cycle. The experiment then does a dark enivorment for 24h time period for a long period. You will see the active and inactive periods shift. The animal will have about 12h of active behaviors and about 12h inactive behaviours periods in the darkness which will be their new circadian rhythm.

b) And with this rhythm shift, if an external zeitgeber like the natural light/dark periods during the 24h of a day is present to it will effect the rhythm.

What is epinephrine n?

ADRENALIN!

What is the effect of stress in a) Short-term and b) Long-term, are they positive or negative?

a)

• Survival (springa från predator) positive

• Higher heart rate will increase and pump more blood and O2 out to the muscles.

• Sympathetic nervous system will respond with (fight or flight) and releace adrenaline and noraderenaline to the body.

• The ventilation will increase to supply the body with O2 to get AT

• Processes like digestion and reproduction will reduce to use energy on other processes.

• Cortisol levels will also rise to help with faster respones and better focus.

• Immunförsvaret startar för ta hand om ev skada

b)

• Negative

• High blood pressure for a longer period will have a negative effect on the heart.

• The immune system will be effected negativly.

• The digestion in the body will be damaged and could lead to lose of weight or diseses.

• The sleep will also have a negative effect because of the fight or flight response beacause the parasympatic NS can’t work beacuse sympatic NS is working non stop.

What is striated skeletal muscle?

tvärstrimmlig skelettmuskelatur

True or false: “The vertebrate motor unit of striated skeletal muscle is one pair of antagonistic muscles (ex: the biceps and the triceps of humans)”

False

True or false: “ The force of a muscle contraction can vary depending on how many motor units are engaged in a contraction?”

TRUE

List and decribe the events that takes place (in skeleltal muscle fibers) between the realese of acetylcholine from a somatic motor neuron on to the skeletal muscle sacrolemma and the iniation of cross bridge action as skeletal muscle contraxtion starts

1. Frisättning av acetylkolin

När en nervimpuls når änden av den somatiska motorneuronen, frisätter neuronen acetylkolin (ACh) i synapsklyftan mellan neuronen och muskelcellen.

2. Bindning till receptorer

Acetylkolin binder till specifika receptorer på muskelcellens sarkolemma (cellmembran). Detta orsakar en förändring i permeabiliteten hos cellmembranet.

3. Depolarisering av sarkolemma

Den bundna ACh-receptorn leder till att natriumjoner (Na⁺) strömmar in i muskelfibern, vilket resulterar i depolarisering av sarkolemma och skapar en aktionspotential.

4. Spridning av aktionspotential

Aktionspotentialen sprider sig längs sarkolemma och in i muskelcellen genom T-tubuli (transversala tubuli), vilket möjliggör en snabb och effektiv spridning av signalen.

5. Frigöring av kalciumjoner

Aktionspotentialen når det sarkoplasmatiska retiklet (SR), vilket orsakar frisättning av kalciumjoner (Ca²⁺) från SR till muskelfibrernas cytoplasma.

6. Aktivering av troponin och tropomyosin

De frigjorda kalciumjonerna binder till troponin, ett protein som är en del av muskelfibrernas aktinfilament. När kalcium binder till troponin, förändras dess form och drar på så sätt bort tropomyosin från aktinets bindingsställen.

7. Korsbryggans initiering

När tropomyosin avlägsnas, kan myosinhuvudena binda till aktinfilamenten, vilket initierar korsbryggans cykel. Detta leder till att myosinhuvudena drar aktinfilamenten mot varandra, vilket orsakar muskelsammandragning.

Why does fetus have higher pO2 (oxygen partial pressure) than the mother? From blood samples.

• Placenta and fetus near each other allowing O2 exchange (The placenta serves as the interface for gas exchange between maternal and fetal blood.)

• Fetus has to have high affinetet than the mother at any given pO2 (This means that HbF can bind oxygen more readily, allowing the fetus to extract oxygen from maternal blood even at lower oxygen levels.)

• There is an oxygen partial pressure gradient between the maternal and fetal blood. Maternal blood (with lower pO2) releases oxygen into the fetal blood (with higher pO2) due to this gradient, which promotes diffusion of oxygen from the mother to the fetus. (kräver energi aktiv transport)

Provide a short explanation for your customers on what just happend to the sperm whales while diving in this particular occasion. With all body systems (circulation, metabolism, respiration, nervous system, hormones, muscle,…) how they work togheter to achivce proper homeostastis while diving. Focus on the three mechanisms of the classical dive response and aerobic dive limit.

• Animal is scared

• Dive reflex leads to Apnea (holding of breath)

• Rapid Vasoconstrition (blodkärl i yttre delarna drar ihop sig snabbt) by PNS → lower bloodflow in larger parts of the body

• heart rate decreases → resitance in blood flow = Bradycaria occur

• parasympatic NS slows down digestion because of the stress. Sympatic NS starts

• And the ATP is then used on other important parts ex heart and brain

• The body uses stored O2 in ex muscles, hemoglobin, myoglobin, phosfat binding osv

• As the whale dives deeper the lungs will compress to handle the increased pressure from the water

• Lung collapse and alveolar collpase that enables the gasexchange of the O2 that is left in the lungs.

• oxygen uptake switches from aerobic to anaerobic (ADL (aerobic diving limit) is reached )

• Anaerobic metabolism = makes energy without O2, anaerobic glycolysis to make glucouse from lactic acid.

• Summary beacause of the responses of the whale it will be able to stay under water for 90 min with homeostatis

• If ADL is not reached lungs collapese wont happen. ADL is not reached during volontary dives.

what is Bardycardia (diving)?

This is a decrease in heart rate. When a person dives, the heart rate decreases as an adaptation to conserve oxygen. This is done by activating the parasympathetic nervous system, which inhibits the activity of the heart.

“Breeding like rabbits” is a common expression for having large number of offspring. Rabbits are indeed noted for their great reproductive potential. Rabbits exhibit induced ovulation and postpartum estrus. Explain in not more than 6 sentences these reproductive traits and how they help endow rabbits with their considerable reproductive potential

Induced ovulation means that the ovulation (release of an egg) is connected with the act of copulation. Copulation between a male and a female result in a spike(peak?) in the hormone LH in the female 1-2 h after mating and trigger ovulation. Postpartum estrus is a time period directly after giving birth that makes the female ready to mate again and induced ovulation can take place if mating occurs in this time period. That they have this time period directly after giving birth makes them able to reproduce at a very high speed.

Explain VO2 max with 3 sentences

VO2 max is the maximum amount of oxygen the body can utilize during intense exercise. It represents a person's aerobic capacity and is a key indicator of cardiovascular fitness. The higher the VO2 max, the more efficiently the body can deliver and use oxygen in the muscles.

Explain phosphagen with 2 sentences

The phosphagen system is the body's immediate energy source used during short, intense bursts of activity, such as sprinting or weightlifting. Doesn't require oxygen, making it anaerobic.

Explain respiratory qoutlent in 1 sentences?

The respiratory quotient (RQ) is a ratio used to measure the amount of carbon dioxide (CO₂) produced relative to the oxygen (O₂) consumed during metabolism. It provides insight into which macronutrients (carbohydrates, fats, or proteins) are being used for energy.

Explain glycolysis in 2 sentences?

Transforms 1 glucose into 2 pyruvic acids that can enter the Krebs cycle. 2 ATP is produced

Explain Glycogen in 2 sentences?

A form of stored glucose, in the presens of insulin glucose is stored as glygogen in the liver.

Explain electron transport chain in 2 sentences?

Creating the most ATP. A series of protein complexs that achive e- from NADH and FADH, creating a concentration gradient.

Unmyellinated axons conduct action potentials without decrement, but when myelinated axons lose their myelin sheaths, then the conduction of action potentials is blocked. Explain in not more than 4 sentences why that is the case.

Unmyelinated axons conduct action potentials continuously along their length through the regular spread of ions, maintaining the signal without decrement. In contrast, myelinated axons rely on saltatory conduction, where action potentials jump between nodes of Ranvier, significantly speeding up transmission. When myelin is lost, this insulation is disrupted, preventing the efficient jumping of action potentials and causing ion leakage. As a result, the signal weakens and may fail to propagate across the axon.

Mammals have brains that are more complex than those of fish and amphibians, particularly in terms of expansion of the cerebral cortex. Does this increased complexity make mammals more advanced and fish and amphibians more primitive? Explain in not more than 4 sentences why you think that this is the case or why you think that this is not the case.

Yes I believe that this makes mammals more advanced and this is due to Some of the physiological principles of the brain. First, the size of the brain matters and bigger allows for more complex and advanced processing. a The cerebral Cortex is also w vital component for planing, coordinating and desicion making of different types of movements. Lastly the hindbrain of mammals and fish/amphibians are very alike and this Could argue to be the primitive state of our brains.

Suppose you are in charge of a captive breeding program for a species of zoo animal that is similar to humans in its reproductive endocrinology. By study of hormone signals, how could you tell when a female ovulates? If you permit her to mate at that time, how could you later tell from study of hormone signals whether she has conceived? Explain your answers in not more than 4 sentences (in total, not per question).

To determine when a female ovulates, you can monitor her levels of LH, which surges just before ovulation. To detect if she has conceived, you would look for a sustained increase in progesterone levels after ovulation, indicating that the corpus luteum is supporting a potential pregnancy. If conception has occurred, progesterone remains elevated, whereas it would drop if conception did not occur.

what is LH?

LH is a hormone produced by the pituitary gland that triggers ovulation in females.

What is Progesterone?

Progesterone is a hormone produced mainly by the ovaries after ovulation that helps prepare the uterus for pregnancy and maintain early stages of pregnancy. It also regulates the menstrual cycle and supports embryo implantation.

True or false: As you add electrical stimulation at a low frequency (1 stimulations/sec.), the muscle produces a series of Single Twitch contractions. Each Single Twitch produces an Increases tension compared to the previous Single twitch contraction.

False

True or False: As the frequency of stimulation Increases (fromn 1stim/sec to 20 stim/sec.) the muscle does not have time to relax completely between two Single twitch contractions. During this Summation (of Single twitch contractions) there may be a small increase in muscle tension.

True

True or False: As the stimulation frequency increases further (to 40 stimsec.) the muscle has no time to start the relaxation process between contractions and the muscle reaches Fused Tetanic contraction.

True

True or False: A sustained high concentration of Ca2+ in the cytoplasm of the muscle fibers ls required for Tetanic contraction to happen.

True

True or false: If you add stretchling the muscle to the experiment, the muscle tension will reach its X maximum level when the muscle is stretched to its maximum length.

False

True or false: When you stretch the muslce to its maximum the reduced overlap between thin and thick filaments of the sarcomeres of the muscle fibers results in a reduced muscle tension.

True

Explain the role of Ca2+ sensitization during smooth muscle contraction. (Use the 8 rows below to write your answer, do not write outside the lines or increase the number of rows)

Ca²⁺ sensitization in smooth muscle contraction enhances the muscle's responsiveness to calcium by inhibiting myosin light chain phosphatase (MLCP), allowing myosin light chain kinase (MLCK) to remain active. This leads to increased phosphorylation of myosin light chains even at lower Ca²⁺ concentrations. As a result, cross-bridge cycling and contraction continue despite reduced Ca²⁺ levels.

A team of Animal sclentists are out on a boat, on a lake, and it mers day. As part of a study on Fish breathing, they are taking water samples from various depths in the lake to construct a plot of dissolved O2 versus depth important that they measure its partial pressure of dissolved O2 immediately, rather than letting it sit on the boat deck for 20 min and then measure the PO2?

This is due to the physiological property of water. Water has both higher density and viscosity than air and therefore dissolves less oxygen. Also factors such as higher temperature and decreases PO2. In this case the temperture may be the biggest issue, if we wait the temperture can change, thus the PO2.

The result of the experiment on PO2 measured in different depths in this Lake (related to question a) shows that the PO2 close to the bottom of the lake is low. For fish species, that live close to the bottom of this lake breathing/respiration is a challenge. Fish gills are very effective when it comes to picking up oxygen from the environment to the blood in the gill capillarles. Explain why the Respiration model Countercurrent Gas Exchange (in Fish gills) is a more effective way to transport Oxygen than Cocurrent Gas Exchange.

In countercurrent gas exchange the medium and the blood flows in opposite direction, creating a gradient in pO2. Since it always higher in the medium, oxygen easily diffuses over to the blood. The blood leaves with higher po₂ than the medium. In cocurrent gas exchange the medium and the blood flows in the same direction eventually reaching equilibrium. There is still a gradient in pO2, but not as great in countercurrent. The blood leaves with lower pO2 than if it would have been countercurrent.

Explain what a cardiovascular shunt is and what physiological consequences does it have. Name 3 animal groups in which shunts can be found in healthy individuals.

A shunt is a morphological structure that cardiac output to the allows for variable Pulmonary and systemic distribution of Circulation. The physiological consequence it have is variable mixing of deoxegynated and oxegynated blood. Another blood that needs to be oxegynated example, Such is not shunts is to direct as in mammalian fetuses, since their lungs and liver fully developed yet. Other animal groups that has it are non-avian reptiles and lungfish species

What 3 mechanisms is used before aerobic ATP production, in a pay-as-you-go-phase?

• Stored Phosphagens = The phosphagen bonds breaks to produce ATP

• Stored O2 in muscles = Use O2 in myoglobin

• Anaerob glycolysis = Produce ATP without O2 but creates latic acid that becomes metabolized when O2 i availble

What happens when you stimulate an isolated axon that gentrate an AP at both ends at the same time. Describe in no more than 4 sentences what happens when they meet?

When action potentials (APs) are generated simultaneously at both ends of an isolated axon and propagate toward each other, they will eventually meet. When they do, they cancel each other out because the refractory period of each AP prevents further depolarization. This refractory period ensures that no new AP can be initiated at the collision point. As a result, the APs dissipate upon meeting and no further signal continues down the axon.

Explain in not more 4 senctences the functional advatages and disadvatages of electrical synapses?

Adventages: faster than chemical, goes both way on the axon, Synchronization (stimulates more than one)

Disadvantages: less strenght and duration than chemical, bidirectionality (goes both way can be negative)

If fiber muscle contration is an all-or none phenomon, how can a muscle generate different amounts of tension?

• Adding more muscles fibers and motor units = recruitment

• Timing of when each fiber contracts

• Summation, not as precise as the others

Patients with amenia typically display an increase in the concentration of 2,3-DPG in their blood that cause a reduction in affinity of about 10 mmHg. The oxygen saturation values at increasing partial O2 pressuares for an anemic and a control patient are shown in the table below.

Is patient A anemic or not? Justify your answer?

The P50: the O2 is saturated (mättad) to 50%, patient A has PO2 value of 35 and patient B has 25. 35-25=10. Patient A has the same saturation with higher PO2, so yes patient A is anemic.

Is the increase in 2,3-DPG concentration beneficial for anemic patients, justify your answer.

Ja, en ökning av 2,3-DPG (2,3-difosfoglycerat) är fördelaktigt för anemiska patienter. 2,3-DPG binder till hemoglobin och minskar dess affinitet för syre, vilket underlättar syreavgivning från hemoglobin till vävnader. Vid anemi, där antalet röda blodkroppar och därmed syretransportkapaciteten är reducerad, hjälper ökat 2,3-DPG att leverera mer syre till vävnader trots begränsad mängd hemoglobin. Denna anpassning kan delvis kompensera för anemi genom att förbättra syreavgivningen. Men om 2,3-DPG-nivåerna blir för höga kan syreupptaget i lungorna försämras, vilket kan motverka den totala syretransporten. Därför är en måttlig ökning av 2,3-DPG generellt fördelaktig för att förbättra syreleveransen till vävnader hos anemiska patienter.

The heart in amphibians has two atria and a single ventricle. If blood from the lungs returns to the left atrium and blood from the tissues returns to the right atrium, why don't these two types of blood mix in the single ventricle? What prevents that from happening? explain in not more than 6 sentences.

In amphibians, the partial separation of oxygenated and deoxygenated blood within the single ventricle is achieved by both timing and structural adaptations. When blood enters the ventricle from both atria, it tends to remain somewhat separated because the ventricle's muscular contractions guide blood flows along distinct pathways. Oxygenated blood from the left atrium is directed preferentially toward the systemic circulation, while deoxygenated blood from the right atrium is directed toward the pulmonary arteries. Additionally, spiral valves within the conus arteriosus (the outflow tract) help channel blood more precisely into the correct arteries. This strategic flow pattern minimizes mixing and allows for more efficient oxygen delivery despite the single-ventricle structure.

Explain what a right to left shunt is and how it is crucial to sustain mammalian fetal development.

A right-to-left shunt is a condition in which deoxygenated blood bypasses the lungs and flows directly from the right side of the heart to the left side. This type of shunt is crucial for sustaining fetal development in mammals, as the fetus receives oxygen through the placenta rather than through its own lungs. The two main structures involved are the foramen ovale, which allows blood to flow from the right atrium to the left atrium, and the ductus arteriosus, which connects the pulmonary artery to the aorta, diverting blood away from the lungs. After birth, these shunts close as the lungs become functional, allowing for normal circulation patterns. The right-to-left shunt is vital during fetal life, facilitating proper growth and development before the newborn transitions to breathing air

explain in not more than 4 sentences the adaptive advantages that centralization and cephalization may offer in the evolution of NS organization.

Centralisering innebär att nervfunktioner samlas i ett centralt system, vilket förbättrar koordinering och respons eftersom signalbehandling sker snabbare från en enhetlig plats.

Cephalization, där sensoriska organ och nervcentra koncentreras i huvudregionen, möjliggör snabbare upptäckt och respons på omgivande stimuli, särskilt i den riktning djuret rör sig.

Dessa anpassningar ökar organismens förmåga att effektivt interagera med sin omgivning, vilket förbättrar dess chans till överlevnad och reproduktion i komplexa miljöer.

Describe the organization of a motor unit in vertebrate skeletal muscle in not more than 5 sentences

A motor unit in vertebrate skeletal muscle consists of a single motor neuron and all the muscle fibers it innervates. The motor neuron’s cell body is located in the spinal cord, and its axon extends out to connect with multiple muscle fibers, forming a neuromuscular junction at each fiber. When the motor neuron fires an action potential, all the muscle fibers in that unit contract simultaneously, producing coordinated movement. The size of a motor unit varies depending on the muscle's function; smaller motor units allow for precise control (e.g., in the hands), while larger units provide powerful contractions (e.g., in the legs). This organization enables graded control of muscle force by recruiting different numbers and types of motor units as needed.

in fiber muscle contraction is an all-or-none phenomenon how can a muscle generate differente amounts of tension? In not more than 5 sentences

Though each muscle fiber contraction follows the all-or-none principle, whole muscles can vary the amount of tension they generate by adjusting the number of motor units activated and by varying the frequency of stimulation. When more motor units are recruited (a process called motor unit recruitment), the overall force generated by the muscle increases. Additionally, by increasing the rate of action potentials sent to the muscle (known as rate coding), the tension can be increased as the muscle fiber contractions overlap, producing a stronger, sustained contraction called tetanus. Muscle tension can also be fine-tuned by activating different sizes of motor units, with smaller units providing finer control and larger units providing greater force.

what is the physiological relevance of peripheral vasocontriction in a seal preforming a volontary dive.

Peripheral vasoconstriction is physiologically relevant for seals during voluntary dives as it helps conserve heat and maintain core body temperature in cold water.

By reducing blood flow to the extremities, seals minimize heat loss while ensuring that vital organs, like the heart and brain, receive sufficient oxygenated blood.

This process also prioritizes oxygen delivery to critical muscles and organs during periods of apnea, allowing seals to dive for extended durations while reducing the risk of hypoxia.

Is seals homothermal or heterothermal?

Homothermal

How does vasoconstriction take place? explain the anatomical strucutes that explain how the central nervous system triggers the constriction of a blood vessel,

Vasoconstriction occurs when smooth muscle cells in the walls of blood vessels contract, leading to a reduction in the diameter of the vessel. This process is primarily triggered by the central nervous system (CNS) through sympathetic nervous system activation.

Gas transport in animals often occurs by alternation of convection (bulk flow) and diffusion. Describe these two ways of transporting oxygen and carbon dioxide in an air breathing mammal and explain where/when, in the animal, Oxygen and Carbon dioxide is transported by convection and diffusion, respectively.

Diffusion transports: O2 and CO₂ molecules from regions of high P02 resp. PCO₂ to regions of low PO2 resp. PCO₂.

Diffusion of O2 and CO₂ occurs at the alveolar air spaces from to (O2 into alveoli from the lungs and CO₂ from the alveoli to lungs and ventilation) and at tissue cells (O2 into tissues, CO₂ out of tissues).

Convection transports O2 and CO₂ molecules in a solution, and transport occurs when air or blood flows.

Convection occurs between the air in the atmosphere and the lungs and also when blood transports O2 and CO₂ throughout the body (regions of high concentrations to low conc.)

What is the Foramen Ovale? Why is it important for blood circulation during fetal development in mammals? Formulate your answer with a maximum of five sentences.

The foramen ovale is an opening in the interatrial septum of the fetal heart that allows blood to flow directly from the right atrium to the left atrium, bypassing the non-functional lungs. This structure is crucial during fetal development because it enables oxygen-rich blood from the placenta to efficiently circulate to the body while avoiding the lungs, which are not yet in use. The foramen ovale helps maintain proper blood flow and pressure in the developing fetus, ensuring that vital organs receive adequate oxygen. After birth, the foramen ovale typically closes as the lungs become functional.

The typical thermoneutral curve as shown in Figure 10.28 of the book informs of the metabolic costs associated with potential thermoregulatory costs when ambient temperature changes. Considering that the curve has a flat part (the so-called thermoneutral zone, TNZ) does that mean that within the TNZ there are no thermoregulatory mechanisms in operation? Formulate your answer with a maximum of five sentences.

The thermoneutral zone (TNZ) represents a range of ambient temperatures where an animal can maintain its body temperature without expending extra energy on thermoregulatory mechanisms. However, this does not mean that all thermoregulatory mechanisms are inactive within the TNZ; rather, the costs of these mechanisms are minimized. Animals may still engage in subtle thermoregulatory behaviors, such as adjusting posture or seeking shade, to maintain optimal body temperature. Additionally, physiological processes, such as vasodilation and the modulation of fur or feathers, can still occur to fine-tune temperature regulation even when the energy expenditure is low. Therefore, while metabolic costs are reduced, some thermoregulatory mechanisms are still at play within the TNZ.

Carassius carassius (the crucian carp) and some other fish sometimes risk facing oxygen free waters, especially in the winter. They have a way of coping with anoxia and unlike turtles they can remain conscious for a long time. All tissues of the fish produce ATP by anaerobic glycolysis. The unique feature of these fish is that their swimming muscles can turn lactate into ethanol which can be excreted from the gills. However, most animals don't have the ability to convert lactate to ethanol. How do they get rid of the lactate?

They must have access to O2 to get rid of lactate. The lactate is then convert back to pyruvic acid and then it either enters the Krebbs cycle or used to synthesize glucose.

Explain in not more than 4 sentences the functional differences between ionotropic and metabotropic receptors.

An ionotropic receptor is an ion channel which opens and directly increase the ion permeability, for those ions that can diffuse through the ion channel, in the cell when binding of a molecule. When a metabotropic receptor binds a molecule a metabolic cascade involving second messengers initiates in the cell, this can e.g., indirectly lead to an increased ion permeability of the cell membrane. The response of molecule-binding to a metabotropic receptor are usually slower and has a longer effect than the binding of a molecule to a ionotropic receptor.

Explain what "fiber recruitment" means in muscle physiology.

This means that there are an increase in the number of fibers contributing to the contraction of the whole muscle.

When and what for Is fiber recruitment needed?

Fiber recruitment is needed during physical activities to increase muscle force output, with higher recruitment required for more intense or heavy tasks.

Justify the actual mechanism by which fibers are recruited? (vilka storlekar på muskelfibrer sköter vilka typer av muskler?)

Muscle fibers are recruited through the size principle, where smaller motor units activate first for low-force tasks, followed by larger units as force demands increase.