BY 124L Animal Development & Muscle Physiology

During embryonic development, cells increase in _______________ but also undergo _____________

number, differentiation

What is differentiation?

process of unspecialized cells becoming specialized - becoming tissues, organs, organ systems (stem cells)

What are the four stages of early developmental stages?

1- Fertilization and Cleavage

2- Gastrulation

3- Neurulation

4- Organogenesis

When does development begin? (Fertilization and Cleavage)

fertilization

What is fertilization? (Fertilization and Cleavage)

the process of two haploid gametes fusing to become diploid zygote

What is a diploid zygote? (Fertilization and Cleavage)

fertilized egg

What are two functions that fertilization serve? (Fertilization and Cleavage)

1 - combine the different chromosomal sets of 2 haploid individuals into 1 diploid

2- to activate the egg

The sperm-to-egg combination begins a _____________ change of reactions starting development? (Fertilization and Cleavage)

metabolic

Females are born with _____ their eggs, but gradually lose them with each _____________ cycle?(Fertilization and Cleavage)

all, menstrual

All eggs are at the _____________ __ and then at each menstrual cycle, they progress to ______________ __ until lost. (Fertilization and Cleavage)

prophase 1, metaphase 2

Fertilization is followed by what? (Fertilization and Cleavage)

cleavage

What is cleavage? (Fertilization and Cleavage)

this is the process of rapid cell divisions, resulting in a ball of cells from the zygote

The size of the zygote undergoing cleavage _________ _____ increase in size, ONLY cell ________. (Fertilization and Cleavage)

does not, number

During cleavage, the ___________ is partitioned off into these new cells, what are these new cells called? (Fertilization and Cleavage)

cytoplasm, Blastomeres

The first and second cleavage are ___________ (________). Produces how many cells? (Fertilization and Cleavage)

vertical (polar), 4 cells

The third cleavage is ______________ (____________). Produces how many cells? (Fertilization and Cleavage)

horizontal (equatorial), 8 cells

What are the first five stages of the cleavage of a zygote? (Fertilization and Cleavage)

ovum, two cells, four cells, eight cells, blastomere stage (mass of cells)

Continued division after the blastomere stage result in? (Fertilization and Cleavage)

a Morula

In the center of the Morula, is the what? What is this? (Fertilization and Cleavage)

Blastocoel, a fluid-filled cavity

Once the Blastocoel is _______ formed, the embryo is in the _________ Stage? (Fertilization and Cleavage)

fully, Blastula

What is Gastrulation?

once the Blastocoel is formed, cells begin to migrate from the surface, inward towards the center

What is the opening for these cells to move? (Gastrulation)

Blastopore

What are the two things the Blastopore can become? (Gastrulation)

Protostomes - mouth is blastopore

Deuterostomes - anus is blastopore

Once cells migrate inward, the Blastocoel will be obliterated, forming the what? (Gastrulation)

Archenteron

What will the new cavity, the Archenteron form? (Gastrulation)

the digestive tract of the animal

The final stages of gastrulation is the formation of the what?

3 germ layers

What are the three germ layers? (Gastrulation)

ectoderm (outer layer), mesoderm (middle layer), endoderm (inner layer)

What does the ectoderm develop into? (Gastrulation)

Nervous System, Epidermis/Outer skin glands, Inner Ear, Lens of the Eye, Adrenal Medulla

What does the mesoderm develop into? (Gastrulation)

Lining of the Coelom, Notochord, Muscles, Skeleton, Gonads, Kidneys, Circulatory System

What does the endoderm develop into? (Gastrulation)

Lining of Digestive System, Liver, Pancreas, Thyroid, Lungs

What is neurulation?

the formation of the Neural Groove, the outer, ectodermal cells flattening to form a groove

The outer edges of the Neural Groove will fold, forming the what? (neurulation) What will this do?

Neural Folds

The Neural Folds will wrap around, combining to form the what?

hollow Neural Tube

What is Organogenesis?

the process of forming organs

What are the first two organs? (Organogenesis)

neural tube and the notochord

What does the neural tube become?

the Brain and Spinal Cord

What does the notochord form? (Organogenesis)

Intervertebral discs within the spine

Blocks of Mesoderm will condense forming the ___________ of the backbone

vertebrae

Does Organogenesis occur at the same time as Neurlation?

yes

What are the three basic types of muscles?

skeletal, cardiac, smooth

Skeletal Muscle is attached to what to move the skeleton?

bone

Is skeletal muscle voluntary or involuntary?

voluntary

Is skeletal muscle striated?

yes

What is the organization of a muscle?

Sarcomere, myofibril, muscle fiber/cell, muscle

Skeletal muscle contains what thing called what?

muscle cells called muscle fibers

Muscle cells are attached by what?

connective tissue

What are within the cells that extend the length of the cell?

myofibrils

Where do myofibrils contract?

along their length

Myofibrils alternate, along their length, in _________ and __________ bands

light and dark

What are dark bands called? what are they bisected by? Do they remain constant during contraction?

A bands, M bands, yes

What are light bands called? What is in the middle of these bands? Do they remain constant during contraction?

I bands, Z bands, no

What is the functional unit of myofibrils?

sarcomere

What are the two proteins that make up the Sarcomere?

actin and myosin

What is actin? Where is it connected at? Does it shorten during contraction?

thin filament of 2 molecules, connected at the "Z" Line, no

What is myosin? Where is it connected at? Does it shorten during contraction?

thick filament of hundreds of molecules, connected at the "M", no

In the Sarcomere, what pulls actin towards the middle?

myosin

What is the first step in muscle contraction?

myosin head attaches to actin

What is the second step in muscle contraction?

working stroke - the myosin head pivots and bends, pulling the thin filament toward the midline of the sarcomere

What is the third step in muscle contraction?

ATP attaches to the myosin head, causing it to detach from the actin filament. The cycle then repeats

What is morphogenesis?

development of the animal's shape or body form, and organization

The width of the ____ band remains constant throughout contraction

A

Contraction narrows the ___ bands and the ___ zone as the ___ discs come closer together, the dark areas of the __ band become wider

I, H, Z, and A

What are Z discs connected to?

cell membranes

The __ discs and __ lines run through the myofibrils and align the sarcomeres

Z, M

The dark areas of the __ band correspond to region where the thick and thin filaments overlap

A

The light area in the middle of the A band, called the __ zone, consists of thick filaments only

H

The width of the A band corresponds to the length of the _______ filament

thick

The __ band corresponds to regions consisting of thin filaments only

I

What does the sarcoplasmic reticulum house?

Ca2+

Myosin has 6 polypeptide chains, __ are light and __ are heavy

4, 2

The __ chains terminate in 2 regions called the myosin head, the __ chains are found in the myosin head

H and L

Which neurons innervate skeletal muscle?

motor neurons

What are the nerve ends that connect or lie close to the muscle?

axon terminal branches

What is the region between an axon terminal branch and a muscle cell?

neuromuscular junction

what is the neurotransmitter that is stored in vesicles of the terminal branch?

Acetylcholine

When a nerve impulse reach the axon terminal branch, it causes an influx of what ions? What does this influx cause?

calcium, vesicles with ACh to fuse with nerve cell membrane

Where does ACh bind to specific recptors?

motor end plate membrane

What does the binding of ACh do to the membrane, which causes it to be more permeable to what ions? What does this flow initiate?

open pores, sodium (into muscle) and potassium (out of muscle), action potential

Is calcium concentration normally high or low in the cytoplasm? where is it stored? the action potential travels to the SR membrane and modifies it, allow what ions to be released?

low, SR, Ca2+

What does the increase of calcium ions in the muscle cell cytoplasm allow myosin to do?

to bind to actin and the muscle to contract

What is located in the muscle end-plate membrane that break down acetylcholine?

acetylcholine esterase

When ACh is absent, Na and K revert to the normal locations, where does Ca2+ go?

SR

What disease is characterized by skeletal muscle weakness and fatigue, caused by immune cells destroying ACh receptors?

myasthenia gravis

What causes paralysis by binding to ACh receptors and not allowing a current to form in the mucle cells?

curare

What inhibits ACh esterase, preventing action potential from forming?

nerve gas and pesticides

What blocks the release of ACh from the axon terminal branches? With 500 grams of this, you could kill the entire human race.

botulinus toxin

Fast-twitch (light) muscles are ____ in myosin ATPase, have a ________ blood supply, ______ mitochondria counts, and receive ATP production via what?

high, poor, low, glycolysis

Slow-twitch (dark) muscles are ______ in myosin ATPase, have a _______ blood supply, ______ mitochondria counts, and receive ATP production via what?

low, good, high, oxidative phosphorylation