MCAT Biology Embryogenesis and Nervous system

  1. fraternal twins description
    • 2 diff eggs released
    • 2 diff sperm
    • implants on uterine wall and develops own placenta
  2. conjoined twins description
    • incomplete division of when a single zygote splits into 2
    • share same structure except amnion for monozygotic
  3. by dividing into smaller cells, the cells increase 2 ratios:
    • nuclear to cytoplasmic
    • surface area to value ratio for gas exchange and nutrient exchange
  4. 2 cells groups of blastoysts (mammal blastula)
    • trophoblast
    • inner cell mass
  5. Ampulla
    second portion of the fallopian, tube It is an intermediate dilated portion, which curves over the ovary,common site of human fertilization
  6. acrosomal apparatus
    a tube like structure formed from sperm which extends to puncture cell mem
  7. cortical reaction
    puncture of cell mem and release calcium ions
  8. fertilization mem
    depolaized and impenetrable mem that occurs after the sperm has penetrated the membrane and has entered
  9. indeterminate cleavage
    cells that can develop into complete organisms
  10. determinant cleavage
    cells with fates that are already determined
  11. morula
    solid mass of cells after several divisions
  12. blastula
    hollow ball of cells with fluid filled cavity known as blastocoel
  13. the trophoblast cells function
    • surround blastocoel and give rise to chorion and placenta
    • specialized to create an interface between the maternal blood supply and developing embryo
    • form chorionic villi
  14. inner cell mass function
    protrudes in blastocoel and gives rise to organism itself
  15. chorion function
    extraembryonic mem that develops into the placenta
  16. chorionic villi
    microscopic fingerlike projections that penetrate endometrium and support maternal fetal gas exchange
  17. umbilical cord function
    • two arteries and 1 vein encased
    • carries fresh oxygen blood with nutrients from placenta embryo
  18. yolk sac
    supports embryo until placenta is functional and is the site of early blood cell development
  19. allantois
    invlove in early fluid exchange between embryo and yolk sac
  20. umbilical cord is formed from remnants of the yolk sac and the allantois
  21. amnion
    • surrounds the allantois
    • serves as shock absorber during pregnancy
    • forms placenta
    • chorion adds another level of protection
  22. deuterosomes (humans) blastopores develops into anus
  23. protosomes blastopore develops into mouth
  24. 3 primary germ layers (outer into inner)
    • ectoderm
    • mesoderm
    • endoderm
  25. ectoderm gives rise to 3 things
    • epidermis
    • epithelium
    • lens of eye and nervous system
  26. mesoderm gives rise to these 5
    • musculoskeletal, circulatory,excretory system
    • gonads
    • muscular and connective tissue layers
    • digestive and respiratory systems
    • adrenal cortex
  27. endoderm gives rise to these 2 things
    • epithelial linings of digestion and respiratory tract
    • pancrease,thyroid,bladder, and liver
  28. induction
    ability of one group of cells to influence the fate of other nearby cells, which is mediated by inducers (chemical substances)
  29. neurulation
    development of the nervous system
  30. notochord
    • rod of mesoderm
    • forms along the axis of the organism like a spine
  31. 4 steps of neurulation
    • notochord forms along axis
    • notochord induces overlying ecto to slide inward to form neural folds
    • neural folds grow toward each other to form neural tube
    • neural crest cells migrate to form PNS as well as other specific cell types
    • ectoderm cells migrate over neural tube and crest to cover NS
  32. neural tube gives rise to CNS
  33. teratogens
    substances that interfere with development causing defects or even death of embryo
  34. cause of teratogens
    • genetics
    • exposure and rate of placental transmission of teratogens
    • alcohol, drugs, viruses, bacteria
    • environmental chemicals
  35. diabetes in babies is due to
    increase blood glucose and causes baby to be too large w/hypoglycemia
  36. maternal folic acid deficiency causes
    prevent closure of neural tube which leads to spinal bifida
  37. 2 ways for determination of what a cell will be
    • after being determined, the cell can become any cell type and will commit to a specific lineage
    • can be determined during cleavage (asymmetrical spliting between 2 daughter cells, specific mrna molecules result in determining)
    • secretion of specific molecules from nearby cell
  38. morphogens (determination)
    • cause nearby cells to follow a particular development pathway
    • closer to morphogen to the cell, the more it will differentiate into comparison to those that are further(unique combo of morpho exposure and causes diff of specific cell types)
  39. cells first are determined and then differentiate into the cell they were determined to be
  40. differentiation
    changing in structure, function, and biochem of the cell to match cell type the cell is determined to be
  41. potency
    the ability of a stem cell to differentiate into a specific cell
  42. totipotent
    greatest potency, ultimately differentiate into any cell type in fetus or placenta
  43. as cells begin to differentiate, they lose their potency
  44. totipotent>pluripotent>multipotent
    • any cell differentiation
    • any cell differentiation except those in placental structures
    • multiple cell types within a particular group
  45. after egg is fertilized, the embryo develops into a gastrula contains 3 germ layers which woulde differentiate into diff tissue types in the human body
  46. the ability to induce a stem cell to be a specific type is not easy, depends on complex structures of organs and diff cell types which require diff signals
  47. cell diff depends on location of cell and surrounding cells
    cell comm can occur between autocrine, paracrine, jucxtacrine, or endocrne system
  48. autocrine signals act on what cells
    same cell that secreted the signal first
  49. paracrine signals act on what cells
    cells in the local area
  50. juxtacrine signals act on what cells
    they act directly by stimulating receptors adjacent to the cell
  51. endocrine signals act on what cells
    secrete hormone that travel through the blood to distant tissue
  52. growthfactors (inducers for cell differentiation)
    peptides that promote differentiation and mitosis in certain tissue and can code for particular tissues
  53. cells can disconnect from their location and travel to reach the correct location once they are determined
  54. apoptic blebs
    cell undergone changes in morphology and divides into many pieces that can be digested by other cells
  55. nercosis
    cell death in which cell dies due to injury
  56. regenerative capacity
    • ability of an organism to regrow certain parts of the body
    • (stem cells travel to place where it needs to be regenerated)
  57. complete regeneration
    lost or damaged tissues replaced with identicle tissues
  58. incomplete regeneration
    newly formed tissue is not identical in structure or function to the tissue that has been injured or last
  59. a large amount of C & G knot off the ends of the telomeres
  60. HbF fetal hemoglobin function
    • exhibits greater affinity for O2
    • assists in transfer of O2 into fetal circulatory system
  61. placenta produces progesterone, estrogen, and HCG which helps maintain pregnancy
  62. umbilical arteries function
    carry deoxygenated blood and waste products away from the fetus toward the placenta
  63. umbilical vein function
    carry oxygenated blood toward fetus from placenta as well as nutrients
  64. gas exchange occur in placenta along with waste exchange, lungs of fetus doesnt function until birth
  65. detox and metab are controlled by mothers liver because their lungs and liver are underdeveloped and sensitive to increased BP
  66. How the baby's body deals with the sensitiveness to BP?
    body constructs 3 shunts to divert blood away from organs
  67. function of 3 shunts
    • 1)foramen ovale - one way reroute blood from lungs. Blood entering RA from inferior VC to flow to LA instead of RV
    • 2)ductus arteriosus - blood goes from pulmonary artery to aorta
    • 3)ductus venosus - shunts blood returning from placenta via UV directly to inferior VC
  68. 4 occurrences of 1st trimester
    • major organ development
    • heart beats
    • bones harden
    • embryo becomes fetus
  69. 4 occurrences of 2nd trimester
    • fetus grows
    • moves
    • face looks more human
    • toes/fingers elongate
  70. 3 occurrences of 3rd trimester
    • rapid growth & brain development
    • antibody transport mother to fetus for protection from outside world
    • growing slows and fetus is less active
  71. 4 occurrences of birth
    • cervix thins
    • amniotic sac ruptures
    • uterine contraction=birth of fetus
    • after birth
  72. soma function and location
    location of ER and ribo and is locted in the cell body of the axon where the nucleus is
  73. dendrites function
    receive incoming messages from cells and transmitted through cell body before reaching axon hillock
  74. axon hillock function
    integrate incoming messages from other cells and sums the excitatory or inhibitory signals received by dendrites
  75. action potentials
    • transmission of eletrical impulses down the axon
    • axon hillock receives signals from dendrites (excit inhibit) to and if signal strong enough will cause action potential
  76. myelin ( mammal nerve fibers)
    insulated to prevent loss of signal or signal crossing
  77. myelin sheath function
    maintains electrical signal with one neuron and increases speed of conduction in axon
  78. myelin is produced by these two in what 2 locations
    • oligodendrocytes (CNS)
    • schwann cells (PNS)
  79. function of nodes of ranvier and location
    • between myelin sheaths on axon
    • critical for rapid signal conduction
  80. nerve terminals function and location
    • end of neuron
    • enlarged and flattened to maximiize neutransmission to next neuron and ensure proper release of NT to other neurons
  81. neurons dont physically touch b/c small space w/in terminal portion of axon (synaptic cleft) release NT which bind to dendrites of post synaptic neurons
  82. synapse is made up of these 3
    nerve terminal, synaptic cleft,post synaptic cleft
  83. nerve
    multiple neurons bundled together (sensory, motor, or mixed neurons can make them up) into ganglia
  84. tracts
    CNS neurons bundled together to form tracts that carry one type of info
  85. nuclei
    cell bodies of neurons in the same tract (bundle of neurons that carry one type of info)
  86. axons carry neural signals away from soma, dend carry signals toward soma
  87. astroytes function
    nourish neurons and form blood brain barrier
  88. ependymal cells
    line ventricles of brain and produce cerebrospinal fluid
  89. microgalia
    phagocytic cell
  90. resting mem potential
    an electrical potential difference between the inside of the neuron and the extracellular space
  91. Na/K ATPase maintains negative environment
    • Na gets higher, K gets lower outside of cell
    • Vice versa for inside of the cell
    • cell is more negative, outside is more positive due to for every K molecule, 3 Na molecule come out leaving a more negative charge for the inside
  92. the neuronal plasma mem is impermeable to charged species and is polar so crossing cannot be done. What happens to allow it to cross?
    • a - resting potential is generated by a - charged protein w/in the cell that increase + permeability
    • the Na/K ATPase helps restore the gradient after action potential has occurred as well as gradients that have been dissipated by action potential
  93. once a neuron receives a excitatory or inhibitory input, it causes an action potential from a resting potential or causes it to go from action to resting
  94. excitatory input from neurons cause depolarization which does what
    raising mem potential from resting and makes neurons more likely to fire an action potential which allows the ions to cross, but can only cross once excitatory input reaches a threshold (can be multiple signals to reach threshold or one large one)
  95. inhibitory input from neurons causes hyperpolarization which does what
    lowers mem potential from resting potential thus makes neurons less likely to fire an action potential
  96. summation
    additive effects of multiple signals from neurons which can be either or excitatory and inhibitory signals
  97. 2 types of summation and their definitions
    • temporal-multiple signals integrated during a short period of time
    • spatial-the effects are based on the number and location of incoming signals
  98. in an electrochemical gradient, the interior of the cell is more negative than the outside, so there will be an influx of + charged ions into the cell
  99. 3 states sodium channels exist in during action potential
    • closed-occurs before reaching threshold
    • open-once threshold is reached
    • inactive-when it comes down from threshold
  100. positive potential inside of the cell causes the voltage gated sodium channels to become inactive and the potassium channels to open releasing K+ (3 for 1). there will be a restoration of negative mem once k+ is out (repolarization)
  101. too much K+ cause hyperpolarization of the neuron refractory which furthers action potentials
  102. 2 types of refractory periods and their functions
    • absolute-no stim causes action to occur
    • relaive-greater than normal stim to cause action potential
  103. impulse propagation
    signals to be conveyed to another neuron, action potential must travel down axon and initiate NT release
  104. how impulse propagation works?
    • Na+ rushes into segment of axon, depolar in surrounding regions occur
    • depolar bring segments of axon to threshold and opens NA+ in the segments
    • continues until AP is in a wave like fashion until it reaches nerve terminal, one segment of axon has been fired, the segment beome refractory and can only go in one direction
  105. speed of action potential depends on these 2
    • Length-longer axon, higher resistance, slower conduction
    • cross section-increase CS faster propagation due to lower resistance
  106. saltatory conduction
    signal down the axon hops from node to node
  107. all AP within same type of neuron have same potential diff during depolarization. increased intensity does not result in increase potential diff of the AP but increased frequency of firing
  108. synapse-28463798
    • presynaptic neuron-before synaptic cleft
    • postsynaptic neuron-after synaptic cleft
  109. effector
    neuron signals to a gland or a muscle, the post synaptic cell
  110. how does the message from one neuron travel down to others
    once NT is released into synapse after exiting mem bound vessicles to be exocytosized , the NT molecules diffuse across the cleft and bind to receptors on the post syn cell
  111. NT must be regulated by being removed from the synaptic cleft by these 3 mechanisms
    • NT broken down by enzymatic rections
    • reuptake carriers bring NT back into the presynaptic neuron (serotonin,dopamine,and norepinephrine are carriers)
    • NT may diffuse out of synaptic cleft (NO nitric oxide)
  112. 3 type of NT receptors
    • ligand gated ion (hyper or depolar)
    • G protein coupled receptors (change in levels of cAMP)
  113. sensory neurons
    afferent, transmit sensory info from receptors to spinal cord and brain
  114. motor neurons
    efferent, transmit motor info from brain and spinal cord to muscles
  115. interneurons
    most numerou,locayed in brain and spinal cord and are linked to reflexes
  116. 4 divisions of Spinal cord
    • cervical
    • thoracic
    • lumbar
    • sacral
  117. vertebral function
    • protects spinal cord
    • transmits nerves at the space between adjacent vertebrae
  118. white matter inside SP
    greay matter outside SP
    inside SP are axons of motor and sensory neurons
  119. autonomic NS, two neurons work in series to transmit messages from SP, what are the two neurons and their functions
    • preganglionic and postganglionic
    • soma of pregang (release acetycholine) is in the CNS and its axon travels down gang to PNS, there it synapses to postgang (norepinephrine) which affercts the target tissue
  120. 2 types of reflex arc and functions
    • monosynaptic - single synapse between sensory neuron that receives stimulus and motor neuron responds
    • polysynaptic - one interneuron between the sensory and motor neurons
  121. knee jerk reflex explained (monosyn)
    patellar tendon is stretched, info travels up sensory neuron to SP where it interfaces with motor neuron that contracts the quadricep muscles which results in extension of leg and tension lessens on patellar
  122. withdrawal reflex explained (polysyn)
    person places foot on ground to remain balanced. the motor neuron controls the quadriceps in the opp leg and must be stim, extending the leg. Interneurons in SP provide the connections from sensory info to motor neurons in supporting leg
Card Set
MCAT Biology Embryogenesis and Nervous system
chapter 3 and 4 of biology book