Bio 155 Lecture

What is Homeostasis?

The ability to maintain a stable environment. Is preserved when our physiological mechanisms use energy to keep body conditions steady in spite of disruptions

What 3 components does homeostasis regulation of a biological variable require?

1.) sensor : Detects changes or deviations in a physiological variable from its normal range

2.) Integrator: which is the control center. It compares value to the set point and determines appropriate response.

3.) effector: organ or tissue that receives commands from control center and works to restore homeostasis.

What is Allostasis? What are the 2 types and what do they particularly do that’s different from homeostasis.

Refers to the body’s ability to adapt our set points or our behaviour to meet different conditions.

Physiological Allostasis: our internal integrators can shift their set points during specific states ( ex. Bp increases when scared)

Behavioural Allostasis: when we voluntarily perform behaviours that alter a regulated variable away from its current set point. (Ex. Wrapping up before you go outside)

Both forms are feed-forward and anticipate a future physiological need.

What’s a feedback loop? What are the 2 types?

Feedback loop: occur when change detected by a sensor triggers an effector response that changes the environment.

Negative feedback loop: returns the controlled variable toward its set point. (Ex. Eating roses blood glucose level and insulin is released to take up glucose so levels decrease in blood. When at set point insulin release stops.)

Positive feedback loop: enhance or amplify changes. Each cycle moves the regulated variable further from its initial set point.

Structure determines ____. Exact features of a structure may reflect ___ between ____.

Function.

tradeoffs. Multiple competing functions.

Cell Cycle describes what? What happens if the cell cycle is disrupted?

The balance in a typical cell between cell division and ‘simply’ performing normal physiological functions.

If cell cycle regulation is disrupted, abnormal cell division can occur leading to tumours, which can lead to cancer.

True or false: a cell that divides at an abnormally fast rate will become a cancer.

False- it will become a tumour.

Benign tumour vs. malignant tumour.

Benign tumour - stays within its original tissue boundaries. Malignant cancer spreads beyond them.

Compare the concentrations of ions in the extracellular fluid (ECF) and the Intracellular fluid (ICF)

ICF: little Na. Lots of K+, little Cl. Lots of large anions. very little Ca- almost none.

ECF: lots of Na. little of K+. lots of Cl. no large anions and a lil bit of Ca. (but more than ICF)

Passive vs. active transport + the different types of each.

What is vesicular transport?

Passive Transport: allows substances to move according to their concentration or electrochemical gradients.

• Free diffusion.

• Facilitated diffusion

Active Transport: uses stored energy to move ions against a concentration gradient.

• primary active transport - ‘pump’ protein directly uses ATP

• secondary active transport - uses a gradient of one molecule (created using ATP) to move another molecule.

Vesicular Transport: a specialized form of active transport (needs ATP) that can move large molecules or many molecules at a time using endosomes.

• Exocytosis - transporting things out

• Endocytosis- transporting things in- needs more ATP.

Is the inside or outside of the cell more electronegative?

inside of cell.

What are the 4 types of tissues?

Epithelial Tissue, Connective Tissue, Muscle Tissue, Nervous Tissue.

Explain what Muscle Tissue is.

Muscle Tissue is able to contract and produce mechanical force.

Explain what Nervous Tissue is.

Specialized to send and receive information in the form of electrochemical signals.

Explain what epithelial tissue is.

What 2 main types does this include?

• Tissue that covers surfaces in your body- external surfaces, internal cavities and passageways and secreting structures.

• includes Epithelia and Glands

Explain what connective tissue is.

Typically fills or stiffens spaces in you body.

What are some basic features all epithelial cells share. What are the types of surfaces in epithelial cells?

• they share polarization. Meaning they are structurally and functionally different on either side.

• Apical surface ( in contact with lumen) . Basolateral surface ( in contact with interstitial fluid) . There is also the basement membrane.

What defines how water and solutes can move between lumen and ISF? What are the different types of these?

Tight junctions define how water and solutes can move between the lumen and ISF.

• ‘Leaky’ tight junctions- allows paracellular transport of water and solutes.

• ‘Tight ‘ Tight junctions - do not allow for paracellular transport.

(paracellular transport- goes through junction. )

(transcellular - goes through the membrane)

What are the different types of epithelial tissue structures?

What is ‘pseudo- stratified’ ?

What determines the name of the tissue structures?

There is squamous. Cuboidal. Columnar.

There is also simple epithelia- one layer between basal membrane and lumen . And Stratified epithelia - multiple layers.

There is also ‘Pseudo-stratified’ which is an exception. Is is ‘pseudo’ because every epithelial cell touches the basement membrane.

The layer closest to the lumen determines shape name of epithelial cells.

What is the histological definition of connective tissue? What are the different types?

It is defined by the presence of extracellular protein fibres and cells suspended within a ground substance (matrix), but can fulfill many functions.

Connective Tissue proper. Fluid connective tissues.(blood, lymph) Supporting connective (cartilage, bone) tissues.

What types of connective tissue are there?

Can be divided into:

Loose - with low density of extracellular fibres and with more diversity of cell types.

Dense - with high density of extracellular fibres and with less diversity of cell types.

What are the different cell types found within loose connective tissue- + give examples

There are fixed cells - which remain permanently in the tissue.

• Fibroblasts- baby cells remain that secrete the proteins of extracellular matrix

• Fibrocytes- mature cells that maintain the proteins of the extracellular matrix

Wandering cells - can move into or through tissue depending on physiological demands.

• Mesenchymal cells- stem cells that divide to replace damaged cells

Several different types of protein with different biophysical properties can be present as extracellular fibres in connective tissue proper

Elastin fibres- not always present but they are elastic and stretch + recoil.

Collagen fibres- in most connective tissues. High tensile strength ( strong but not stretchy - resists mechanical force)

Tissue membrane vs. Fasciae.

Tissue membrane: a layer of epithelial tissue + underlying layers of connective tissue.

Fasciae: layers of pure connective tissue that surround organs and provide physical support.

how do epithelial and connective tissues employ strategies for healing repair after damage?

Epithelium: Rapid proliferation (makes lots of new cells) A clot forms out of blood tissue for ex.

Connective : (mostly) increased rates of secretion of more fibres. A scar forms when a dense web of collagen fibres is secreted at the injury site.

What is the integument? and what does it consist of (what are the diff layers?")?

Your skin. Consists of the cutaneous membrane, which consists of the epidermis and the dermis. There is also the hypodermis- the lowest layer- but it isn’t part of the cutaneous membrane. The integument also contains accessory structures.

What are some functions of the integument?

• is a barrier of the inside of you to the outside world.

• Vitamin D and Ca2+ homeostasis.

• Is a sense organ

• Thermal homeostasis

What is thin and thick skin?

Thick skin is hairless (on plantar and palmar surfaces). Thin skin is hairy (everywhere else)

What type of epithelium cells is the epidermis consisted of? (compare thin and thick skin)

Thick skin:

• Stratum corneum

• stratum lucidum (very thin)

• Stratum granulosum

• Stratum spinosum

• Stratum basale (on top of the basal membrane)

Thin skin: ( no stratum lucidum)

• C

• G

• S

• B

How are epidermal cells generated?

They are generated in the deepest layers, only basal cells divide. they are differentiated in the middle layers.

When a basal cell divides, one will be another basal cell and one will be a keratinocyte. Once it is made, it is pushed to the stratum spinosum. Cells in all the other layers are keratinocytes. Then will differentiate.

In the stratum granulosum, nuclei and organelles kicked out to make more room for more keratin. then shed from the superficial layers.

After this, they are no longer Alive cells.

What is a keratinocyte? What does it mean for the epidermis to be keratinized?

A keratinocyte is a cell filled with a lot of keratin, which is a tough, cross-linked, water resistant protein that limits insensible perspiration ( which is water loss through the cutaneous membrane not through sweat glands).

What are melanocytes and where are they located. What are melanosomes?

Melanocytes are found within the stratum basal and produce melanin pigments and transfer them to keratinocytes.

Melanosomes (the vesicle) are packed with melanin are transferred via vesicle transport —> are specialized organelles/ vesicles inside melanocytes.

What are the two layers of connective tissue contained within the dermis?

• The stratum papillare (loose connective tissue proper)

• Stratum reticulare (dense, irregular elastic)

• also lots of blood vessels.

In integumentary repairing- what is the first stage? What are the other stages?

• First stage is an inflammatory response, so increased blood flow and an attraction of immune phagocytic cells.

• then its the migratory phase,

• proliferation phase

• and the scarring phase.

Explain the migratory phase in integumentary repairing

Scab forms on the surface and macrophages remove debris and pathogens.

At the epidermis: proliferation of basal cells

At the dermis, recruitment, proliferation and differentiation going on. Granulation tissue formed, which is a mixture of new blood vessels, mesenchymal cells and fibroblasts.

Explain the proliferation phase and the scarring phase in integumentary repairing. What type of scar can happen when there is high proliferation and secretion from fibroblasts?

Proliferation phase: Deeper portions of the clot dissolve and fibroblasts produce new collagen fibres and ground substances. Normal cell division at the epidermis.(instead of proliferation mode where you make 2 basal cells, they go back to one basal and one keratinocyte)

Scarrring phase: scar tissue is formed. In the dermis, activation happens where there is enhanced collagen secretion. Very high proliferation and secretion from fibroblasts can cause a keloid scar formation

What is a callus?

Is a specific thickening of the stratum corneum that is caused by keratinocytes being more strongly cross-linked. These more links causes more force and Time needed to shed.

What are glands in the integumentary? give the 2 types.

They are epithelial structures which contribute to protection or homeostasis.

• Sebaceous glands. secrete sebum.

• Sweat glands- secrete sweat. There are apocrine glands, which are found in axillary and pubic regions. There are eccrine glands which are found mostly everywhere.

Skin plays a critical role as a ___ and an ___ in thermal homeostasis. Name the two roles it plays.

evaporative cooling- liquid to gas.

radiant cooling- heat radiates off of you.

How does the epidermis participate in calcium homeostasis? What trade-off exists?

It does so by synthesizing vitamin D.

a trade-off that exists between melanin and vitamin D synthesis is that in dark skin, upper layers absorb more UV light, and less reaches basal layers and makes less vit C. In lighter skin, upper layers let more UV light through to basal layers and so more vit. D but also more cell damage.

What are the effects of age on the integument in epidermis and dermis layers?

epidermis: fewer melanocytes (less melanin to absorb UV). Drier epidermis (less resistant to bacteria), thinning epidermis and decreased perspiration (more susceptible to heat strokes) .

dermis: Altered hair and fat distribution, slower skin repair , reduced blood supply, loss of elastin, thinning dermis and diminished immune response.

What are the variety of connective tissues that connect the skeletal and muscular systems? + what types of connective tissue are they?

Cartilage:

• supportive connective tissue

• Joint surfaces, ears, nose, vertebral discs.

Ligaments:

• Dense regular connective tissue

• Anchors bones to other bones

• Matrix: collagen and usually some elastin.

Tendons:

• Dense regular connective tissue

• Anchors bones to muscles

• Matrix: mostly collagen and little to no elastin.

Cartilage and bone are both what types of tissues?

What are each of their matrix strengths and compositions?

Bone tissue ‘s matrix is made of collagen (fibres in bone), calcium salts, hydroxyapatite. Matrix strength is strong and relatively rigid.

Cartilage’s matrix is made of chondroitin sulfates- which are carbohydrates (+ proteins forming proteoglycans). Matrix strength is relatively flexible.

Cartilage is ____ and contains ____ residing in ____.

Surface of cartilage typically covered by what layer?

Is avascular and contains chondrocytes (cells living in cartilage) residing in lacunae.

Surface of cartilage typically covered by a dense fibrous connective tissue layer called the perichondrium.

What are the 3 subtypes of cartilage which differ in extracullualar fibre composition ?

• Hyaline Cartilage

  • proteogylcans

• Elastic Cartilage

  • proteoglycans + elastin fibres

• Fibrocartilage

  • proteoglycans + extra collagen.

Label the following:

Also, what is the difference between ‘Bone’ and ‘A bone’

bone = tissue

A bone = an organ

What are the two subtypes of bone tissue organization?

• Compact bone: dense and able to resist compression. Like osteons- cells in lacunae, organized in concentric rings operated by layers of matrix.

• Spongy bone: light and distributes force- like spaces around trabeculare which are filled with bone marrow.

What are 4 types of cells found in bone tissue ? Where are they found?

Osteogenic cells: produce other bone cells

Osteoblasts ( created by osteogenic cells): produce bone matrix

Osteocytes: (once osteoblasts surrounds itself with matrix) maintains bone matrix.

Osteoclasts: dissolves bone matrix.

How do bones act as a reservoir for minerals within ur body?

• ability of bone to be actively remodelled by cellular activity allow it to store or release minerals as they are needed.

• Balance between the amounts of osteoblast and osteoclast activity help maintain calcium homeostasis. ( osteoblasts continuously deposit new bone matrix and osteoclasts erode existing matrix, releasing calcium and phosphate ions into the circulation.

What are the two methods cartilage can grow by and does it ever cease?

• Cell-division

  • Interstitial growth: chondrocyte proliferation

    • Growth by cell division ceases after adulthood.

• Differentiation.

  • Appositional growth: Mesenchymal cells differentiation into new chondrocytes by adding extra layers to surface.

  • Cells differentiate into chrondroblasts, they secrete new matrix, and mature into chondrocytes.

What are the two mechanisms bone can grow via?

1.) Endochondral growth: (increase length of bone)

• occurs via ossification of cartilage.

• 1. Most bones begin in utero as hyaline cartilage

• 2. ossification begins at shaft

• 3. Next, ossification starts at the epiphyses (ends)

• 4. Cartilaginous ‘epiphysial plates’ grow by interstitial division unit they ossify at puberty.

  • at the plate, chondrocytes are dividing (lengthening the bone), they die and deteriorate (matrix is calcifying)

  • Osteoblasts secrete bone matrix (ossification) and cartilage replaced with bone.

• Some bones initially form through intramembranous ossification- arising within dense proper connective tissue. Mesenchymal cells differentiate into osteoblasts, and the ossification centre is where ossification begins. - ex. dermal and sesamoid bones.

(osteocytes do NOT proliferate- bone does not grow intersitiatal growth- only cartilage does.)

2.) Appositional growth: (in crease diameter of bone)

• Adds layers to outer surface of bone. Osteoblasts active at periosteum, Osteoclasts active at the endosteum.

What type of joint is a synovial joint?

free movement- diarthrosis- most complex- involve several different tissues, including bone and hyaline cartilage (specifically articular cartilage- which is a subtype of this)

Can/how does bone tissue repair itself?

Can/how does cartilage repair itself?

Bone repairs itself well. bone healing involves extra proliferation of cells which typically first differentiate into cartilage.

• First, internal and external callus made by chondrocytes making fibrocartilaginous matrix and making hyaline cartilage. Cartilage → spongy bone → compact bone.

Cartilage does not repair itself well bc interstitial growth doesn't happen after puberty so repair through appositional growth only can occur

• However, articular cartilage cannot undergo self-repair at all usually bc it lacks a perichondrium layer.

What is Osteoarthritis?

• Is a degenerative disorder caused by damage to the articular cartilage

What are the types of Muscle tissue and what are the 3 distinct subtypes?

There is striated muscle (has stripes)- which has the subtypes of skeletal muscle tissue and cardiac muscle tissue.

There is also smooth muscle .

How is each skeletal muscle connected to the skeletal system?

What is skeletal muscles organized within?

What is a fascial compartment?

Tendons ( which are narrow and/or rounded). OR aponeuroses (which are broad and flat).

Skeletal muscles are organized within layers of fasciae (bundles of muscle fibres).

A fascial compartment is a space of the body containing one or more muscles that is enclosed by fascia.

Each muscle is a ___.

Explain the structure of an individual muscle using the following diagram.

Each muscle is an organ.

Individual cells within skeletal muscles are myofibers, which is a single cell that contains many nuclei. stretches tendon-tendon. long.

Within one myofiber, there are myofibrils that are specialized organelles inside striated muscle cells. They allow muscles to contract.

Within Endomysium(connective tissue surrounding muscle) there are myosatellite cells that are stem cells for muscle tissue.

perimysium made of dense elastic connective tissue.

A single muscle is surrounded by an epimysium

Label the following structure.

Label the following structures.

T-tubules, bring membrane into cell.

Stores and releases calcium

How are myofibers made and how are they repaired in adulthood?

Myofibers are made by the fusion of many myoblasts during development and are repaired in adulthood by myosatellite cells (which proliferate and fuse w existing myofibers.)

What does excitation-contraction (E-C) coupling refer to?

refers to the mechanisms by which excitation triggers contraction.

What is a neuromuscular junction (NMJ) made up of?

What is the motor unit made up of?

Please label this structure:

• made up of the axon terminal, synaptic cleft and the motor end plate.

• Motor unit is combo of motor neuron and muscle cell(s)

(that’s the NMJ at the top)

What is the process of the excitement of a muscle cell at the NMJ?

• Myofibre is at rest, electrical signal is arriving via action potential.

• neurotransmitters are released.

• Neurotransmitter binds and NMJ is excited

• Excitation is spread through the myofibre’s sarcolemma beginning from NMJ due to voltage-gated ion channels getting triggered via spreading depolarization. (graded potential generated at motor end plate triggers and ap in muscle cell’s sarcolemma).

• The T-tubules propagate the action potential into the vicinity of the sarcoplasm reticulum, triggering internal calcium release from ICF into ECF.

• and then enzymes remove the neurotransmitter.

btw the space is the synaptic cleft, the blue is the axon terminal and the end plate is shown.

What do Ions move according to when moving across membranes?

What is the transmembrane potential at rest? (V_m)

concentration gradient AND electrochemical gradient- charged molecules like ions are either attracted or repelled according to charge in membrane.

At rest, there is negative transmembrane potential (V_m)

_{ALL Vm signals occur by proteins that allow ions to rapidly cross the membrane- ion channels.}

What is the difference between graded and action potential?

Graded potential: change in membrane potential whose size depends on strength of stimulus.

Action potential: when a membrane depolarizes enough to reach a threshold. (either full ap or none)

What is the difference between depolarization and repolarization and hyper polarization?

Vm signals are described in terms of what?

depolarization is when the cell is becoming less negative. (ex. Na
+ entering cell) .

Depolarization is when ions are leaving the cell and the cell is becoming more negative. (ex. K+ leaving cell).

Hyperpolarization is when the cell is more neg than at RMP.

Vm signals are described in terms resting membrane potential (RMP)

What are the categories of ion channels?

• Leak channels (undated)

  • RMP is created by leak channels, which are always open.

• Gated channels

  • Ligand-gating: only open when ligand binds.

  • Voltage-gating: open and close depending on voltage

  • Mechanical-gating: pressure/ mechanical force applied and channel opened.

In the process of muscle excitation, what is the neurotransmitter and what is the receptor?

Neurotransmitter is acetylcholine(ACh) - is the ligand.

and the receptor is ACh-receptor. which is a ligand-gated ion channel.

Each mature myofiber has __ neuromuscular junction (NMJ).

A single motor neuron can make NMJs with __ myofibres

one.

many.

What do the contractile organelle myofibrils contain and how are these things they contain organized?

They contain myofilaments- thin filaments and thick filaments.

Myofilaments are organized into repeating units called sarcomeres.

Label all the bands and lines in these images.

What are the twisted strands of the thin filaments of the sarcomere built from?

Thin Built from

• actin- which is organized in a double helical fibre

• Actinin- ground at the Z-line, interconnects thin filaments.

• Tropomyosin and Troponin- wraps around the actin helix

What are the thick filaments composed of?

Thick composed of myosin proteins. Each myosin monomer has a mobile head and neck that can bind to actin or ATP.

Titin tethers the thick filament to the Z-line.

Explain the contraction cycle in more detail.

• AFTER calcium reveals the active site, the contraction cycle begins.

• the myosin head binds to actin (this connection called cross bridges) ,

• Myosin neck pivots and and completes the power stroke, moving the thin and thick filaments past each other. ADP and phosphate released.

• ATP binding allows myosin to detach from actin .

• ATP hydrolysis (ATP → ADP +P) ‘recocks’ the myosin head. remember ATP used to reset myosin neck NOT during the power stroke.

What role does calcium have in muscle contraction?

It interacts with the troponin-tropomyosin complex of the thin filament and therefore reveals the myosin-binding ‘active site’ on actin.

AFTER calcium reveals the active site, the contraction cycle begins.

Interaction of sliding filaments causes the sarcomeres to shorten, creating ___ in the ___. This can only be produced by what?

Tension in the tendons.

This can only be produced by myosin heads that overlap with (and thus bind to ) actin. So the total amount of ‘pull’ depends on how many of its myosin heads can grab onto actin. Therefore, tension can only be produced when active sites are available, and thus tension also depends on Ca2+ levels.

When do muscles produce max tension?

When they are excited at an intermediate sarcomere length.

What is a muscle twitch?

What 3 phases are involved in a single muscle ‘twitch’ contraction?

Muscle twitch is the contractile/tension response of a muscle fibre in response to a SINGLE action potential.

First phase: latent period - muscle excitation.. takes time for action potential to happen and cause contraction.

Second phase: contraction phase, Ca2+ builds up.

Third phase: relaxation phase- Ca 2+ removal after max tension development.

What is a summation?

As summation is repeatedly stimulating a single muscle fibre and is due to residual Ca2+- more Ca2+ enters the cytosol before all the go Ca2+ is removed, revealing more active sites. (ion transport by pumps is slower than movement via ion channels. )

What is tetanus?

If a muscle is producing persistent maximum tension with little to no relaxation phase. Muscle fibres have a max tension when all troponin sites are bound by calcium. Occurs when stimulation (excitation) frequency of myofibril reaches max.

The relationship between tension and actual contraction can be complicated and different types of contraction occur based on the balance between a muscle’s load and the force its producing. What are the 3 types of contraction?

• Concentric (shortening) contractions: occur when the external load is less than internally generated tension. Heavier loads= slower contraction rates.

• Isometric contractions: occur when the muscle produces just enough tension to balance an external load. used to stabilize a joint. length of muscle unchanged during contraction (tension produced).

• Eccentric (lengthening) contractions: when the external load is higher than the internally generated tension. Can be used like a ‘brake’ by slowing down movement at a joint produced by external forces like gravity.

Muscles obtain __ from catabolism of glucose and other nutrients using either ___ or ___ metabolism. Explain these 2 methods.

obtain ATP from catabolism of glucose and other nutrients using either anaerobic or aerobic metabolism.

• Anaerobic: glycolysis, in cytosol and does not require oxygen.

• Aerobic: aerobic metabolism, in mitochondria and requires oxygen.

What are the tradeoffs that exist between the total amount of ATP generated and the rate at which it can be produced?

Aerobic metabolism:

• - needs steady oxygen supply

• - is slow

• + >30 ATP molecules from single glucose molecule

• + can also use fatty acids

Aenaerobic metabolism:

• + doesn’t need oxygen

• +is fast

• - only 2 ATP molecules from a glucose

• - cannot use fatty acids.

What’s a special way muscle fibres can use to store energy?

Can store energy in the form of creatine phosphate (phosphocreatine).

• + doesn’t need oxygen

• + is very fast

• Can only have limited stores in the muscle and is rapidly depleted,

Explain how muscles obtain ATP at the 3 different activity levels ( resting muscles, moderately active muscles and peak activity)

Resting: use aerobic respiration of free fatty acids to build up energy stores of glycogen and creatine phosphate (recharging stores). slow building of ATP surplus.

Moderately active muscles: use aerobic respiration of both free fatty acids and glucose. meets current ATP requirements and uses glycogen stores.

Peak Activity: Most or all myofibrils active. muscles rely on anaerobic respiration of glucose and use up energy stores like creatine phosphate and glycogen. Waste products like lactate and creatine build up.

What is muscle fatigue and when does it occur?

Muscle fatigue is reduced contractile tension for the same (excitation) stimulus. It occurs when rapid ATP production affects the ability of muscles to initiate or maintain the contraction cycle.

• trouble in initiate: Fatigue factors that affect excitation: ACh vesicles on the motor neuron axon terminal are depleted and K+ is accumulated in the T-tubules due to repeated APs. (which Is bad normally lots of K+ inside cell and little outside so K+ leaks out and keeps inside neg. If outside K+ rises, gradient shrinks so less K+ leaves and inactivates voltage gated NA+)

• Trouble in maintain: Fatigue factors that affect contraction: leakage of Ca+back into the sarcoplasm due to leaking (tired/sluggy) channels- shuts down processes bc body detects not healthy. Microtears in myofibrils (myosin heads rip off cuz trying to slide over but stay attached).

• Build up of lactate and H+ (acid disrupts function)

What are short term and long term recovery methods from muscle fatigue?

short term: in rest, lactate can be used in aerobic metabolism or shipped to the liver for gluconeogenesis.

Medium/long term: Myosatellite cells activated and proliferate, utilizing supplies of free amino amino acids in blood to rebuild torn myofibrils.

What is the trade-off that sustained contractions expose between maximal tension production and energy efficiency?

Maintaining the contraction cycle needs a steady supply of ATP for every participating myosin head. If you add more myofibrils (max tension), you need to either squish in more mitochondria to support contractions (more energy) or risk rapid fatigue.

What are the different distinct types of muscle fibres?

Type I: known as slow twitch or slow oxidative fibres. Fewer myofibrils but more mitochondria. slow myosin and slow pumps. more capillaries per fibre so higher oxygen supply. now powerful (less max tension) but fatigue resistant and fast to recover.

Type II: fast twitch. fast myosin and pumps, fewer capillaries per fibre, more myofibrils per fibre but fewer mitochondria. produce high force and rapid contractions, but fatigue easily and recover slowly.

• Type II A and B

• Type II A have intermediate properties between Type IIB and Type 1.

  • fast contraction speeds, intermediate twitch directions, size/power, mitochondria + capillary density and intermediate resistance from fatigue.

How are motor units and tension generated related?

What is the size principle?

All fibres in a motor unit are the same fibre type- both the number of myofibrils per fibre and the number of myofibres per motor unit contribute to tension. small motor units have few fibres all type I, larger motor units have many fibres all type IIB

The size principle is when only the smallest motor units will be recruited by weak stimuli in the spinal cord while strong stimuli recruit both small medium and large motor units.

Compare Synchronous and asynchronous motor unit recruitment.

Synchronous recruitment: many motor units activated at the same time. they all fatigue around the same time tho. used for short, maximal efforts like jumping, sprinting or heavy lifting.

Asynchronous recruitment: motor units activated in rotation, out of phase. while one group of units contracting, another is resting. This produces stead smooth force for a long time without fatigue. used for sustained, low intensity activity like holding posture or walking.

What are the two ways muscles can enhance their peak tension production by becoming larger? Which way I used in adult humans?

Hyperplasia: more myofibres per fascicle.

Hypertrophy: more myofibrils per myofibre

In adult humans, muscles increase in size via hypertrophy. after embryonic development, skeletal muscles can repair muscle fibres but cannot add new ones. physical training increases fibre diameter not number

Can fibres be converted into different types?

What is the difference between Aerobic training and Anaerobic training?

Is very rare. between type IIA and IIB possible but type I to II is thought to be harder.

Aerobic training: leads to hypertrophy of Type I fibres

Anaerobic training (high intensity): leads to hypertrophy of Type IIB fibres.

What are the three anatomical components the nervous system can be divided into?

1. Central nervous system(CNS)-

• found within the vertebrae and cranial bones (spinal cord and brain)

• houses majority of all neuronal cell bodies- and their processes.

2. Peripheral nervous system (PNS)-

• located outside the skull and spine, but directly connected to CNS

• nerves, which are collections of long neuronal processes interacting with non-neuronal cells and organs.

• Ganglia, groups of cell bodies outside the CNS.

3. Enteric nervous system (ENS)-

• neural cells within the digestive system, which only indirectly connect to CNS via the PNS.

What are the 2 classes of cells within nervous tissue?

Neurons: principal cells of nervous tissue which transmit information

Neuroglia: which play supporting roles. (elongated cell processes found in neurons like axon and dendrites).

What are glial cells and what are the different types?

Found within nervous tissue (half of cells in nervous tissue) and protect and maintain neurons.

Different types are

• Ependymal cells

• Microglia

• Myelinating cells

• Astrocytes/satellite.

What do Astrocytes and satellite cells do? (type of glial cell)

Astrocytes (In the CNS) Regulate the extracellular environment around neurons and maintain + modify synaptic connections.

• buffer ion concentrations in ECF

• recycle/ buffer neurotransmitters

• regulate local blood flow (oxygen and nutrient supply)

• regulate CSF flow (cerebral spina fluid)

Satellite cells do the same things but in the PNS.

What do myelinating cells do? (type of glial cell) what are the 2 types

Myelinating cells provide electrical insulation in both CNS and PNS

they wrap cellular processes containing myelin (fats and proteins) around the axons of neurons- myelination allows for electrical signals to travel rapidly and efficiently in axons.

Two distinct types are Schwann cells (in PNS) and oligodendrocytes (CNS, instead of wrapping entire cytoplasm around 1 axon, does across multiple)

myelin doesn’t participate in the AP tho just is insulating.

What do Ependymal cells and microglial cells do? (type of glial cell)

Ependymal cells: line ventricles and secrete cerebrospinal fluid (CSF), which bathes and cushions the CNS.

Microglia: white blood cells which perform immune functions for the CNS and help modify connections between neurons.

(both found in CNS)

Neurons are highly ___ cells. Label this cell and mention each parts function.

neurons are highly polarized cells