Cell E3(2)

Ch 22, 24

basic structure of a neuron

has cell body, axon which is one long stretch, dendrites which are shorter more branched, has terminal branches at end, some have myelin shelth around axon length which protects/insulates

What is membrane potential? what is the main producer and maintainer of the membrane potential?

when there is an uneven distribution of charge on either side of a membrane, inside cells it’s usually negative millivolt, main producer is Na/K ATPase pump (ion channels, voltage gated)

Is the membrane potential of a neuron positive or negative and why?

negative due to the voltage gated ion sodium and potassium channels

for Na+, K+, and Ca2+, is the concentration higher or lower inside the cell

K+ inside higher, Ca2 and Na higher outside

How is an action potential generated and propagated? (role of Na, K, voltage gated sodium and potassium channels)

when a change in membrane potential is detected, sodium channels open and depolarization occurs (Na rushes in), then repolarization occurs when voltage gated potassium channels open allowing K+ ions to flow out, (restores internal negative charge)

Why does the action potential only propagate forward and not go backward?

it propagates along the axon, inactivating channels along the way down the axon

What are electrical and chemical synapses?

chemical is connecting by gap junctions, the electrical chemical can’t pass between so it must be converted to a chemical signal at a presynaptic neuron, electrical has gap junctions as ions move between the cells, the depolarization in 1 cell spreads passively to the connected cell (very quick)

How is a signal transmitted across an electrical synapse?

gap junctions between synapse/neurons and action potential travels

How is a signal transmmited across a chemical synapse?

vesicles at end of one neuron (neurotransmitters inside), vesicles fuse to membrane of first neuron and insides go in synaptic cleft, neurotransmitters will bind to receptors on recieving neurons, causes an action potential in other cell

How is neurotransmitter released? What is the role of calcium in neurotransmitter release?

voltage gated calcium channel is before synapse, when action potential reaches it calcium will rush in, on neurotransmitters is a sensor that binds to calcium, sensor can activate snare proteins, causing plasma membrane to do exocytosis

How is neurotransmitter signaling terminated?

reuptake where the neurotransmitters will move out of the synaptic cleft, or they are degraded into inactive molecules

How do postsynaptic neurons integrate signals from synaptic input to determine if they will fire an action potential?

if a neurotransmitter is excitatory it will cause a small amount of depolarization (excitatory postsynaptic potential), if neurotransmitter is inhibitory it will hyperpolarize the postsynaptic neuron by a small amount (inhibiting postsynaptic potential)

voltage-gated ion channel

respond to changes in the voltage across a membrane

ligand-gated ion channel

open when a particular molecule binds to the channel

depolarization

when there is a rapid influx of sodium ions in response to a change in membrane potential

refractory period

after an action potential, a period in which cells cannot fire another one immediately, this ensures that action potentials move in one direction along the axon and do not overlap

neurotransmitter

chemical messengers that can send signals between brain/nerve cells

What are the stages of the cell cycle and what occurs?

What are the stages of mitosis and what occurs?

What cytoskeletal structure comprises the mitotic spindle?

How is the mitotic spindle organized? Include plus and minus ends, as well as kinetochore, polar, and astral microtubules

How does the mitotic spindle line up the chromosomes at the metaphase plate?

What are the anaphase A/B, that lead to chromosomes separating?

How do chromosomes separate during anaphase? What aspects of microtubules and motor proteins lead to the movements of anaphase?

How does cytokinesis occur in animal cells? What is the role of the contractile ring in cytokinesis? What cytoskeletal structures comprise the contractile ring?

At what points is the cell cycle regulated?

What are some reasons the cell cycle needs to be regulated?

What are cyclins and cyclin-dependent kinases and how do they regulate the cell cycle?

How does the mitotic cyclin-CDK get activated to initiate mitosis at the G2/M transition? (role of cyclin, activating and inactivating kinases, phosphatase)

How does activated mitotic cyclin-CDK lead to the initiation of mitosis?

What is anaphase promoting complex and what does it do?

What holds sister chromatids together and how is it released during anaphase? (what proteins)

How does DNA damage affect the cell cycle? role of p53 in signaling cascade that occurs if DNA damage is found

What happens at the spindle assembly checkpoint (m checkpoint) and why is it necessary?

How do growth factors regulate the cell cycle? What is the role of ras and MapK cell signaling pathway?

What is apoptosis, what happens during it?

How can apoptosis be activated?

What are caspases and how are they involved in apoptosis?

What are initator and executioner caspases?

What are the extrinsic and intrinsic pathways of apoptosis?

How are mitochondria involved in apoptosis?

How are Bcl-2 family members involved in apoptosis? What is the role of apoptotic, anti-apoptotic, and pro-apoptotic Bcl-2 family members in initiation of apoptosis?

How is cancer related to cell cycle regulation and apoptosis?

What are oncogenes and how do they lead to cancer?

What kind of oncogenes are there? What do they do, give examples?

What are tumor suppressor genes, how do they lead to cancer?

What types of tumor suppressor genes are there, what do they do, give examples?

How is p53 involved in cancer?