Flashcards in Directed Objectives: Final Exam Deck (51):
Osteoblast Pg. 167
Bone forming cells, have an extensive endoplasmic reticulum and numerous ribsomes.
-Produce collagen and proteoglyans, which are packed into vesicles by the Golgi apparatus and releases from the cell by exocytosis.
-Ossification: The formation of new bone by osteoblasts. Occurs by appositional growth on the surface of previously existing material, either bone or cartilage.
-Also release matrix vesicles, which contain high concentrations of Ca2+ and PO3-/4
-Elongated cell extensions from osteoblasts connect to the cell extensions of other osteoblasts through gap junctions.
-Bone matrix produced by the osteoblasts covers older bone surface and surrounds the osteoblast cell bodies and extensions. The result is a new layer of bone.
Osteoclasts Pg. 168
Bone destroying cells. Large, multinucleated cell.
-Perform reabsorption, or breakdown, of bone that mobilizes crucial Ca2+ and phosphate ions for use in many metabolic processes.
-Mature osteoclasts carry out bone reabsorption through a multi-step process.
-Integrins: Form attachment structures via interactions with cell-surface proteins.
Calcitonin (What Does It Do) Pg. 187
-One of three hormones that helps to maintain calcium homeostasis.
-Secreted from the thyroid gland when blood Ca2+ levels are too high.
-Inhibits osteoclast activity by binding to receptors on the osteoclasts.
Simplified Version: Hormone released from parafollicular cells that acts on tissues to cause a decrease in blood levels of calcium ions.
Parathyroid Hormone (PTH) (What does it do?) Pg. 186
-One of three hormones that helps to maintain calcium homeostasis.
-The major regulator of blood Ca2+ levels.
-Secreted from the parathyroid glands when blood Ca2+ levels are low, stimulates an increase in the number of osteoclasts, which break down bone and elevate blood Ca2+ levels.
-Stimulates osteoblasts to release enzymes that break down the layer of unmineralized organic bone matrix covering bone, thereby making the mineralized bone matrix available to osteoclasts.
Simplified Version: Peptide hormone produced by the parathyroid gland; increases bone breakdown and calcium levels.
What Are The Functions of Bone Pg. 166
1. Body support:
-Rigid, strong bone is well suited for bearing weight and the major supporting tissue of the body.
-Cartilage provides a firm yet flexible support within certain structures. Ex. Nose, External Ear, Thoracic Cage, and Trachea.
-Ligaments strong bands of fibrous connective tissue that hold bones together.
2. Organ Production:
-Bone is hard and protects the organs it surrounds.
-Example: The skull encloses and protects the brain, and the vertebrae surround the spinal cord. The ribcage protects the heart, lungs, and other organs of the thorax.
3. Body Movement:
-Skeletal muscles attach to bones by tendons, which are strong bands of connective tissue.
-Contraction of the skeletal muscles move the bones, producing body movements. Joints, which are formed where two or more bones come together, allow movement between bones.
-Smooth cartilage covers the ends of bones within some joints, allowing the bones to move freely. Ligaments allow some movement between bones but prevent excessive movements. (Ligaments: connect bone to bone)
4. Mineral Storage:
-Some minerals in the blood are stored in bone. If blood cells of the minerals decrease, the minerals are released from bone into the blood.
-The principal minerals stored are calcium and phosphorus, two mineral essential for many psychological processes. Adipose tissue is also stored within bone cavities, If needed, the lipids are releases into the blood and used by other tissues as a source of energy.
5. Blood Cell Production:
-Many bones contain cavities filled with red bone marrow, which gives rise to blood cells and platelets.
Components of Bone Matrix Pg. 167
The intercellular substance of the bone tissue; comprised of organic (collagen and proteoglycans) and inorganic substances (mainly hydroxyapatite). Gives bone tensile strength and weight bearing strength
-Normally about 35% organic and 65% inorganic material.
-The collagen and mineral components are responsible for the major functional characteristic of bone.
-Can be compared to reinforced concrete.
-The collagen fibers lend flexible strength to the matrix, like concrete, the mineral components give the weight-bearing strength.
-If all the mineral is removed from a long bone, collagen becomes the primary constituent and the bone is overly flexible. On the other hand, if the collagen is removed from the bone, the mineral component becomes the primary constituent and the bone is very brittle.
Osteogenic Cells Pg. 169
Immature bone cells capable of mitosis that give rise to osteoblasts.
-Osteochondral progenitor cells are stem cells that can become osteoblasts or chondroblasts.
-Located in the endosteum, the inner surface of the periosteum, and within harversian canals.
-From these locations, they are a potential source of new osteoblasts or chondroblasts.
-Osteoblasts are derived from osteochondral progenitor cells, and osteocytes are derived from osteoblasts. Whether or not osteocytes freed from their surrounding bone matrix by reabsorption can revert to become active osteoblasts is a debated issue. As discussed in the previous section, osteoclasts are not derived from osteochondral progenitor cells but from stem cells in red bone marrow.
Osteocytes Pg. 168
Osteocytes: Mature bone cell surround by bone matrix.
-Retain their connections to neighboring osteocytes through cell extensions.
-Become relatively inactive, compared with most osteoblasts, but it is possible for them to produce the components needed to maintain the bone matrix.
-Lacunae: The spaces without the matrix but occupied by the osteocyte cell bodies.
-Canaliculi: The space occupied by the osteocyte cell extensions.
-In a sense, the cells and their extensions form a "mold" around which the matrix is formed.
Where Articular Cartilage Would Be Found? What Type of Cartilage Is It? Pg. 172
Location: Within joints, the end of the bone bone.
Type: Hyaline Cartilage
Part: Yellow Marrow
Description: Fat stored within the medullary cavity or in the spaces of the spongy bone.
Ampiarthrosis Pg. 242
A slightly moveable joint.
Joints can be classified according to it's degree of motion.
Diarthrosis Pg. 242
Freely moveable joints
Joints can be classified according to it's degree of motion.
Synarthrosis Pg. 242
Joints can be classified according to it's degree of motion.
Positive Feedback Systems (What Are They, When Do They Happen, What Makes Them Stop) Pg. 11
Positive Feedback Systems:
-The body changes from a normal point and amplifies it.
When do they happen?
-Mechanisms occur when a response to the original stimulus results in the deviation from the set point becoming even greater.
What makes them stop?
-Positive Feedback Systems stop when the action is completed.
For example, birth is an example of a normal positive feedback mechanism. Near the end of pregnancy, the baby's larger size stretched the uterus. This stretching, especially around the opening of the uterus, stimulates contractions of the urine muscles. The uterine contractions push the baby against the opening of the uterus and stretch it further. This stimulates additional contractions, which result in additional stretching. This positive-feedback sequence ends when the baby is delivered from the uterus and the stretching stimulus is eliminated.
The Ability to Sense Changes In The Environment is _______________. Pg. 6
-An organism's ability to sense changes in its external and internal environment and adjust to those changes is Responsiveness.
-Responses include actions such as moving toward food or water and moving away from danger or environmental conditions.
-Organisms can also make adjustments that maintain their internal environment. For example, if the external environment causes the body temperature to rise, sweat glands produce sweat, which can lower body temperature down to the normal range.
Homeostasis Pg. 9
The existence and maintenance of a relatively constant environment within the body.
-To achieve homeostasis, the body must actively regulate conditions that are constantly changing.
-As our bodies undergo their everyday processes, we are continuously exposed to new conditions. These conditions are called variables because their values can change.
For example, a small amount of fluid surrounds each body cell; for cells to function normally, the volume, temperature, and chemical content of this fluid must be maintained within a narrow range.
-Homeostatic mechanisms, such as sweating or shivering, normally maintain body temperature near an ideal normal value, set point. *These mechanisms are not able to maintain body temperature precisely at the set point.
-Body temperatures increases and decreases slightly around the set point to a produce a normal range.
-The organ systems help keep the body's internal environment relatively constant.
Example: For example, the digestive, respiratory, cardiovascular and urinary systems work together, so that each cell in the body receives adequate oxygen and nutrients and waste products do not accumulate to a toxic level. If body fluids deviate from homeostasis, body cells do not function normally and can even die. Disease disrupts homeostasis and sometimes results in death. Modern medicine attempts to understand disturbances in homeostasis and works to reestablish a normal range.
Levels of Structural Organization Pg. 4 and 5
Six Levels of Organization:
1. Chemical Level (Atoms):
-Involves interactions between atoms, which are tiny building blocks of matter.
-Atoms combine to form molecules.
-Function of a molecule is related to their structure.
-For example, collagen molecules are ropelike protein fibers that give skin structural strength and flexibility. With old age, the structure of collagen changes, and the skin becomes fragile and more easily torn.
-The basic structural and functional units of plants and animals.
-Molecules combine to form organelles, which are the small structures inside cells.
-For example, the nucleus is an organelle that contains the cell's heredity information, and mitochondria are organelles that manufacture adenosine triphosphate (ATP), a molecule cells use for energy,
-Composed of a group of similar cells and the materials surrounding them.
-The characteristics of the cells and surrounding materials determine the functions of the tissue.
-The body is made up of four basic tissue types: epithelial, connective, muscle, and nervous.
-Composed of two or more tissue types that perform one or more common functions.
-The urinary bladder, heart, stomach, and lung are examples of organs.
5. Organ Systems:
-A group of organs that together perform a common function or set of functions and are therefore viewed as a unit.
-For example, the urinary system consists of the kidneys, ureter, urinary bladder, and urethra. The kidneys produce urine, which the ureters transport to the urinary bladder, which it is stored until being eliminated from the body through the urethra.
-Any living thing considered as a whole -- whether composed of one cell such as a bacterium, or of trillions of cells, such as a human.
-The human organism is a network of organ systems, all mutually dependent on one another.
*The simplest to the most complex:*
6. Organ System
1. Support neuronal activity
2. Remove ions and neurotransmitters that accumulate in extracellular space
3. Provide neurons with energy
4. Mediate brain development by secreting growth factors, guiding neuronal migration, and enhancing formation of synapses.
Astrocyte means a star-shaped cell. More specifically, these are non-neuronal cells of the nervous system that help to support the neurons (nerve cells).
Responsible for ensuring that water gets to its citizens in an appropriate manner through the pipes. Well, the central nervous system has pipes of its own, blood vessels, and the astrocytes help regulate the flow of blood through these vessels.
A glial cell that wraps around the nerve fiber in the peripheral nervous system, and spirally wraps around an axon to form the myelin sheaths of peripheral axons.
Oligodendrocytes are the myelinating cells of the central nervous system (CNS).They are characterized by having dark round, oval and sometimes irregularly shaped nuclei, in which chromatin is clumped both beneath the nuclear envelope and throughout the nucleoplasm. Oligodendrocytes are most abundant in white matter, but they also occur in gray matter, sometimes as satellites to neurons.Oligodendrocytes are types of cells that make up the supportive or glial tissue of the brain.
Ependymal cell, type of neuronal support cell (neuroglia) that forms the epithelial lining of the ventricles (cavities) in the brain and the central canal of the spinal cord. Ependymal cells also give rise to the epithelial layer that surrounds the choroid plexus, a network of blood vessels located in the walls of the lateral ventricles (the two largest ventricles, which occur as a pair in the cerebral hemispheres).
Ependymal cells and their epithelial derivatives of the choroid plexus have several important functions. In the ventricles ependymal cells possess tiny hairlike structures called cilia on their surfaces facing the open space of the cavities they line. The cilia beat in a coordinated pattern to influence the direction of flow of cerebrospinal fluid (CSF), bringing nutrients and other substances to neurons and filtering out molecules that may be harmful to the cells.
Microglia, type of neuronal support cell (neuroglia) occurring in the central nervous system of invertebrates and vertebrates that functions primarily as an immune cell.Microglia nuclei are typically oval-shaped, and projecting out from their cell bodies are slender elongated processes that enable the cells to move via chemotaxis (movement along a chemical gradient).
A. Flight, Fight, Freeze, Faint
B. Thoracolumbar- Nerve Pathway
C. Adrenergic- neurotransmitters
---Activity results in increased alertness and metabolic activities to prepare the body for an emergency situation.
----The main purpose of the SNS, or sympathetic nervous system, is to activate the response of the body during stressful situations. Moreover, this system initiates the fight-or-flight mechanism of the body.
--components of the autonomic nervous system.
Function of muscle tissue
*Smooth muscle: Moving food through the digestive tract, emptying the urinary bladder, regulating blood vessel diameter, changing pupil size, contracting many gland ducts. moving hair.
*Skeletal muscle: Body movement
*Cardiac muscle- Pumping blood; contractions provide the major force propelling blood through blood vessels.
Function of all muscle tissue
1. Movement of the body- Most skeletal muscles are attached to boned and are responsible for the majority of body movements, including walking, running, chewing, and manipulating objects with the hands.
2. Maintenance of posture- Skeletal muscles constantly maintain tone, which keeps us sitting or standing erect.
3. Respiration-Skeletal muscles of the thorax carry out breathing movements.
4. Production of body heat- When skeletal muscle contract, heat is given off as a by-product. This released heat is critical for maintaining body temperature.
5. Communication- Skeletal muscles are involved in all aspects of communication, including speaking, writing, typing, gesturing, and smiling or frowning.
6. Constriction of organs and vessels- The constriction of smooth muscle within the walls of internal organs and vessels causes those structures to constrict. This constriction can propel mixe food and water in the digestive tract; remove materials from organs, such as the urinary bladder or sweat glands; and regulate blood flow through vessels.
7. Contraction of the heart- The contraction of cardiac muscle causes the heart to beat, propelling blood to all parts of the body.
Steps involved in muscle contraction
1. Neuron action potential arrives at end of motor neuron
2. ACH is released
3. ACh binds to receptors on motor end plate
4. Permeability of sarcolemma changes (Na rushes in)(an action potential is produced)
5. Muscle action potential sweeps into the T tubules triggering
6. release of Ca from the cisternae of the sarcoplasmic reticulum
7. CA binds to troponin
8. Troponin changes shape and shifts tropomyosin to expose binding sites of actin
9. myosin binds to actin (cross bridge is formed)(ADP released from myosin)
10. Myosin head pivots (pulling actin)
11. Myosin releases from actin (cross bridge is broken)(another ATP binds to myosin)
A. Rest, response, and digest
B. Craniosacral- Nerve Pathway
C. Cholinergic- neurotransmitters
--subdivision of the peripheral nervous system.
-This system is accountable to stimulate the salivation process, tear production, defecation, digestion, and urination.
Parts of a saccomere
The basic structural and functional unit of skeletal muscle because it is the smallest portion of a skeletal muscle capable of contracting. Each one extends from one Z disk to the next Z disk.
Each sarcomere consists of two light-staining bands are called isotropic bands, I bands, Each I band includes a Z disk and extends to the end of the myosin filaments.
The dark-staining band at the center of each sarcomere is an anisotropic band or A band. Each A band extends the length of the myosin myofilaments within a sarcomere.
In the center of each A band is a smaller band called H zone, where actin and myosin myofilaments DO NOT overlap and only myosin myofilaments are present.
A dark line, called M line, is in the middle of the H zone and consists of delicate filaments that attache to the center of the of the myosin filaments.
Metabolism Pg. 35 or G-15
All of the anabolic and catabolic reactions in the body are collectively defined as metabolism.
-Sum of all chemical reactions that take place in the body, consisting of anabolism and catabolism.
*Cellular metabolism refers specifically to the chemical reactions within cells.
Single motor neuron and many skeletal muscle fibers. All muscle fibers controlled by motor neuron.
A group of skeletal muscle cells that are innervated (connected) by one nerve cell. It tells cells attached to it to contract
Four types of tissue
Tissue composed of layers of closely spaced cells that cover organ surfaces, form glands, and serve for protection, secretion and absorption. Location: Epidermis, inner lining of digestive tract, liver and other glands
Tissue with more matrix than cell volume, often specialized to support, bind together, and protect organs Location: Tendons and ligaments, cartilage, and bone, blood.
Tissue containing excitable cells specialized for rapid transmission of coded information to other cells. Location: Brain, Spinal cord, nerves.
Tissue composed of elongated, excitable cells specialized for contraction. Location: Skeletal muscles, Heart (cardiac muscle), Walls of viscera (smooth muscle)
Four types of tissue 2.0
Covers & protects surfaces on the inside & outside of the body. Composed of cells with very little extracellular matrix between them. Have distinct cell surfaces (apical/free, lateral, basal). Capable of regeneration. Protects underlying structures, acts as a barrier, permits passage of substances, secretes and absorbs substances
Found in the brain, spinal cord, and nerves. Able to conduct electrical signals (action potentials). Consists of neurons and neuroglia. Controls & coordinates body movements
Contracts and shortens (movement). 3 types: cardiac, skeletal, smooth
consists of cells far apart/separated by abundant extracellular matrix. Encloses and separates other tissues, connects tissues to each other, support & movement of body parts, stores compounds, transport and protection.
Simple vs Stratified
One layer vs many layers
Squamous, cuboidal, columnar, transitional
*Squamous epithelial tissue cells are flat and scalelikes with the nucleus in the middle of the cell
*Cuboidal epithelial tissue cells look like cubes with the nucleus in the center of the cell
*Columnar epithelial tissue cells are taller than they are wide, like columns, with the nucleus staying near the bottom of the cell
*Stratified transitional epithelium looks like up to ten layers of roughly cuboidal cells that distort to squamous shape when stretched
*Respond to changes in temperature at the site of the receptor and are necessary for the sense of temperature.
*Thermoreceptors Example: Temperature
-Located in the dermis, skeletal muscles, liver, and hypothalamus that area activated by different temperatures.
Notes: Free nerve endings only respond to 50-118 degrees Fahrenheit. Any lower or higher and the pain receptors take over.
Enzyme found in synaptic cleft that causes the breakdown of acetylcholine to acetic acid and choline, thus limiting the stimulatory effect of acetylcholine.
--Sensory receptors in muscles, joint capsules and surrounding tissues, that signal information to the central nervous system about position and movement of body parts, for example the angle at a joint or the length of a muscle. proprioception the process of receiving this information, with or without conscious awareness
--Defined as a sensory neuron that responds to potentially damaging sensory stimulation. Can be classified as external (cutaneous nociceptors) or internal (associated with organs, muscles, bladder, and gut). Nociceptors generally have receptors that consist of bare nerve endings.
Cranial nerve VIII: The eighth cranial nerve is the vestibulocochlear nerve.
The vestibulocochlear nerve is responsible for the sense of hearing and it is also pertinent to balance, to the body position sense.
Problems with the vestibulocochlear nerve may result in deafness, tinnitus (ringing or noise in the ears), dizziness, vertigo and vomiting.
--The 12 cranial nerves, the vestibulocochlear nerve included, emerge from or enter the skull (the cranium), as opposed to the spinal nerves which emerge from the vertebral column.
Parts of a neuromuscular junction
point where a nerve fiber meets its target cell, a junction at the end of an axon where it stimulates another cell
neuromuscular junction (NMJ) or motor end plate
when the target cell is a muscle fiber, synapse between a nerve fiber and a muscle fiber, also called motor end plate. functional connection between the distal end of a nerve fiber and the middle of a muscle fiber
Rounded areas or swollen tip on the end of the axon terminals, doesn't directly touch the muscle fiber but is separated by a narrow space called synaptic cleft. site of synaptic vesicles and neurotransmitter release
a narrow space between the synaptic knob of an axon and the sarcolemma, across which a neurotransmitter diffuses
envelops the entire junction and isolates it from the surrounding tissue fluid, , One of the two peripheral nervous system supporting (glial) cells. Schwann cells from he myelin sheath on axons of peripheral neurons.
tiny pouches or sacs in the axon terminals that are filled with the chemical messenger called ACh
increases surface area, ACh receptors usually concentrated
proteins in the muscle fiber's membrane to respond to the chemical and binds to the Ach
entire muscle fiber and the Schwann cell of the NMJ are surrounded by this. it separates them from the surrounding connective tissue
deficiency in ACH receptors leads to muscle paralysis
neurotransmitter released by a somatic motor fiber that stimulates a skeletal muscle fiber
enzyme in the sarcolemme and basal lamina of the muscle fiber in the synaptic region; responsible for degrading ACh and stopping the stimulation of the muscle fiber
aka site where axon and muscle fiber communicate
Node of Ranvier
--periodic gap in the insulating sheath (myelin) on the axon of certain neurons that serves to facilitate the rapid conduction of nerve impulses.
Parts of a synapse
--The three parts of a synapse are the presynaptic ending, the synaptic cleft and the postsynaptic ending. An impulse traveling from one nerve cell to another must pass through all three parts to successfully cross the synapse and to travel to the next neuron in the sequence.
--Nerve impulses travel from the body of the nerve cell to its end through the axon terminal, which is a long straightaway. At the far end of this terminal lies the presynaptic ending. This structure contains pockets of chemical neurotransmitters that are released in response to the arrival of the impulse from the nerve.
Once released, neurotransmitters cross the synaptic cleft, which is just a short gap between the nerve cells. Unused neurotransmitters are taken back up by the presynaptic ending after the transmission is complete.
The neurotransmitter proteins that reach their target are taken up by the third part of the synapse, the postsynaptic ending.
The postsynaptic ending has specialized receptor structures on its surface. These receptors accept neurotransmitters in the way that a lock accepts a key.
The arrival of a transmission protein triggers an impulse in the postsynaptic ending that travels up a short terminal to the main body of the cell.
Components of a reflex arch
1. The receptor at the end of a sensory neuron reacts to a stimulus.
2. The sensory neuron conducts nerve impulses along an afferent pathway towards the CNS.
3. The integration center consists of one or more synapses in the CNS.
4. A motor neuron conducts a nerve impulse along an efferent pathway from the integration center to an effector.
5. An effector responds to the efferent impulses by contracting (if the effector is a muscle fiber) or secreting a product (if the
effector is a gland).
--Action potential, the brief (about one-thousandth of a second) reversal of electric polarization of the membrane of a nerve cell (neuron) or muscle cell. In the neuron an action potential produces the nerve impulse, and in the muscle cell it produces the contraction required for all movement.
--Sometimes called a propagated potential because a wave of excitation is actively transmitted along the nerve or muscle fibre, an action potential is conducted at speeds that range from 1 to 100 metres (3 to 300 feet) per second, depending on the properties of the fibre and its environment.
How do ions move during an action potential?
During the action potential, part of the neural membrane opens to allow positively charged ions inside the cell and negatively charged ions out.
--When an impulse is sent out from a cell body, the sodium channels open and the positive sodium cells surge into the cell. Once the cell reaches a certain threshold, an action potential will fire, sending the electrical signal down the axon. Action potentials either happen or they don't; there is no such thing as a "partial" firing of a neuron.
--After the neuron has fired, there is a refractory period in which another action potential is not possible. During this time, the potassium channels reopen and the sodium channels close, gradually returning the neuron to its resting potential. Once the neuron has returned to the resting potential, it is possible for another action potential to occur and transmit the signal down the length of the axon.
--The somatic system is the part of the peripheral nervous system that is responsible for carrying motor and sensory information both to and from the central nervous system. This system is made up of nerves that connect to the skin, sensory organs, and all skeletal muscles. The system is responsible for nearly all voluntary muscle movements as well as for processing sensory information that arrives via external stimuli including hearing, touch, and sight.
Squamous, cuboidal, columnar, transitional more info
what does simple squamous epithelium look like and what is its function?
simple squamous epithelium is a single layer of scalelike cells adapted for transport for example as in absorption
what does stratified squamous epithelium look like and what is its function?
stratified squamous epithelium has many layers of closely packed scalelike cells specializing in protection
what does simple columnar epithelium look like and what is its function?
simple columnar epithelium are tall, column like cells arranged in a single layer. They contain mucus producing goblet cells and are specialized for absorption
what does stratified transitional epithelium look like and what is its function?
stratified transitional epithelium looks like up to ten layers of roughly cuboidal cells that distort to squamous shape when stretched. Stratified transitional epithelium cells are found in body areas that stretch such as in the urinary bladder.
what does pseudostratified epithelium look like and what is its function?
pseudostratified epithelium looks like a single layer of distorted columnar cells. Each cell touches the basement membrane but are stretched and arranged so it looks like there is more than one layer
what does simple cuboidal epithelium look like and what is its function?
simple cuboidal epithelium looks like a single layer of cubelike cells. simple cuboidal epitheium are often specialized for secretory activity. simple cuboidal epithelium may secrete into ducts, directly into the blood and on the body's surface
Cell membrane/Plasma membrane
Forms a boundary between a cell and the surrounding environment and controls the passage of materials into and out of the cell.
Selectively permeable phospholipid bilayer. Composed on hydrophilic polar heads and hydrophobic tails along with proteins, lipids, & other molecules
Steps for mitosis
A four-stage process that creates two identical cells from one original cell.
The first and longest stage of mitosis. In this stage the chromosomes become visible and the centrioles separate and move to opposite poles of the cell.
The second stage of mitosis. In this stage the chromosomes line up across the center of the cell and become connected to the spindle fiber at their centromere.
The third stage of mitosis. In this stage the sister chromatids separate into individual chromosomes and are pulled apart.
The fourth and last stage of mitosis. During this stage the chromosomes gather at opposite ends of the cell and lose their distinct rod-like shapes. Two new nuclear membranes then form around each of the two regions of DNA and the spindle fibers disappear.
The process that follows the last stage of mitosis. With two complete copies of the DNA now in two different regions of one cell, the cell membrane will pinch and divide the cytoplasm in half. The result is two individual cells that are identical to the original cell. Each of the two new cells have a complete copy of the DNA and contain all of the organelles that the original cell had.
A period of cell growth and normal activity. This period comes between mitosis in the cell cycle. Cells that do not need to replicate will spend their time in this stage. If a cell does need to divide, it will copy all of it's DNA while period. This way, the cell has two complete copies of its DNA before it begins the process of mitosis.
Steps of mitosis more in depth
-cell growth and functioning
gap 1 phase of interphase
-duplication of organelles
s phase of interphase
gap 2 of interphase
-cell reaches maximum size
-cell begins preparatory steps for mitosis
NUCLEAR division; not cell division
prophase, (prometaphase), metaphase, anaphase, telophase, (cytokinesis)
-chromatin in nucleus coils into chromatid (chromosomes)
-nuclear envelope begins to dissolve
-microtubules extend from centrioles(called asters= star-like structure)
-centrioles migrate to opposite poles, forming the spindle
-chromosomes attach to spindle, then metaphase occurs
-chromosomes line up on equator (center) of the spindle by their kinetochore region (specialized protein of the chromosome's centromere)
-centromeres split/break down
-chromatid pairs separate and move to opposite poles in the cell
-chromatids reach opposite poles
-nuclear envelope begins to develop around chromatids in the poles
-spindle breaks down
-cytokinesis: membrane splits--> 2 "new" genetically identical daughter cells are formed
Cell Division Triggers
-Physical factors (surface-volume ratio limits diffusion rate, cell density and anchorage)
-Chemical Factors (Growth Factors)
-class of proteins
-each part of cell cycle is triggered by kinases (type of growth factor) that have a site for a chemical messenger to be activated and the signal for that certain part of cell cycle is sent
-MPF (maturation promotion factor--> reference sheet)
-M/S Cyclin dependent Kinase (CDK) is an enzyme that is in its inactive state until a S cyclin (s phase) or M cyclin (mitosis) protein pairs with it
-this pairing then opens another site on the kinase that (once threshold concentration of pairing is reached) a phosphorylated chemical messenger binds to the kinase
-this new pairing triggers the DNA replication (s-cyclin) or mitosis (m-cyclin) and the cyclins are destroyed in the process
-cell division with no control (never stops)
-oncogenes= genes that make proteins for the cell cycle and their faultiness is what causes the uncontrollable cell division
-HeLa cells: Henrietta Lack's cancer cells are still being divided today and used in numerous different drug tests
-Ras Gene: codes for signal protein on cell membrane can be normal or mutated (signal tells to divide and then stop normally, but if mutated it never says to stop)
-Tumor Suppressors: block cell division when it shouldn't divide; basic immune system does this; cancer is a combination of faulty onco/ras genes and a faulty tumor suppressor
-Binary Fission: duplication of DNA in two directions from its attachment point to membrane; separation of those copies
-form a cell plate between the opposite sides that becomes a new cell wall
-plants don't have centrioles, but a spindle still forms
-cleavage furrow: contracting ring of microfilaments (actin) pulls membranes appart
What are they?
Invaginations of the muscle cell plasma membrane that extend deep in to the muscle cell and are in close contact with (but not continuous with) the sarcoplasmic reticulum.
1. T tubules propagate the action potential from the plasma membrane into the interior of the muscle cell via voltage-gated Na and K channels
2. An action potential carried by a T tubule regulates the opening and closing of Calcium channels in the sarcoplasmic reticulum. The resulting change in the cytosolic Calcium concentration triggers the contraction of the myofibrils
Without these, the muscle cell would not be able to contract