Structure and Functions of Cells Flashcards Preview

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Flashcards in Structure and Functions of Cells Deck (54):
1

multipolar neuron

the somatic membrane gives rise to one axon but to the trunks of many dendritic trees

(motor; interneuron)

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bipolar neuron

gives rise to one axon and one dendrite at opposite ends of the soma. usually sensory

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unipolar neuron

one stalk, which leaves the soma and divides into two branches a short distance away. usually sensory with the dendrites outside the CNS and the branches in the CNS are terminal buttons

4

sensory neuron

detect changes in the external or internal environment and send info about these changes to the CNS 

5

glia

responsible for white matter. glue the CNS together by surrounding neurons and holding them inplace. control their supply of nutrients and insulate them from one another so the messages don't get messed up. they remove the neurons that have died (astrocytes, oligodendrocytes, and microglia)

6

microtubules

the thickest strand of cytoskeleton

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axoplasmic transport

substances we propelled along microtubules that run the length of the axon

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anterograde transport

movement from soma to terminal buttons. Done by the kinesin protein, which attaches to the item being delivered and walks it down the microtubule

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retrograde transport

movement of terminal buttons to soma. performed by dynein protein (half as fast as anterograde transport)

10

astrocytes

support neurons and clean debris
produce and control chemical composition of fluid by keeping them at critical levels
nourish neurons
get glucose from capillaries, break it down into lactate and release it into exracellular fluid. neurons take lactate to mitochondria to be used as energy

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oligodendrocyte

support axon to produce myelin sheath (80% lipid, 20% protein)
produces 50 segments of myelin in multiple axons.
does not help regrowth

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microglia

act as phagocytes (clean up debri)
part of immune system for brain
smallest glial cells

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phagocytosis

the process by which astrocytes clean up debris by engulfing it

14

Schwann cell

forms myelin sheath in PNS
only provides myelin for one axon
when damage occurs to the nerve, Schwann cells digest dead and dying axons and can guide regrowth of new axons by signalling neurons to elongate. 

15

area postrema

a part of the brain that controls vomiting where the BBB is much weaker

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threshold of excitation

the voltage level that triggers an action potential

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withdrawl reflex

withdraw limb quickly by getting sensory info and goes into interneuron to send info to motor neuron tomove to the brain. the brain can inhibit the interneuront omodulate the reflex

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depolarization

potential moving closer to zero
sodium channel opens and sodium ions rush into the cell
as more sodium comes in, more channels open to the point where the membrane potential becomes more positive and reaches threshold 
closes sodium channel door and opens potassium channel 
potassium leaves the cell

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hyperpolarization

the potential is moving away from zero
as more potassium ions move outside the cell, the membrane becomes more negative
the potassium channel closes, as well as the sodium channel door (potassium channel closing the slowest)
the sodium channel on the inside of the membrane opens

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force of diffusion

the process where molecules distribute themselves evenly throughout the medium in which they are disolved. The rate of this movement depends on the temperature. the collision of molecules forces some to move upwards and some downwards

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force of electrostatic pressure

the force exerted by the attraction and repulsion of ions

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threshold of excitation

~-60 mV
If a signal doesn't reach the threshold, it diminishes...no action potential

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ions/anions

ions have positive charge
anions have negative charge

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intracellular fluid

within cell membrane
contains organic anions (A-) and potassium ions (K+)
 

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organic anions (A-)

unable to pass through membrane, therefore it contributes to membrane potential

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potassium (K+)

mostling inside the cell, but diffusion can push it out. Once outside it is positively charged, therefore electrostatic pressure forces it in

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extracellular fluid

outside the membrane contains sodium ions (Na+) and chlorine ions (Cl-)

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chloride (Cl-)

mostly outside the cell, but diffusion pushes it in. since the inside is negatively charged, pressure keeps it out

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sodium (Na+)

mostly concentrated on the outside, but some are allowed inside. the sodium potassium pump pushes Na+ outside the cell. Sodium potassium transporters exchange 3 sodium ions for every 2 potassium ions they push in. 

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electrical gradiant

inside membrane is slightly more negative and outside membrane is slightly more positive.  As ions exchange, the cell tries to keep a balance of posititive and negative ions

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concentration gradiant

wants a balance of ions inside and outside of the cell. ions want to diffuse. This is stronger than the electrical gradiant, which is why sodium gets rushed in 

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ion channels

contian passages that open or close. the permeability of a membrane is detrmined by the number of ion channels open

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voltage dependent ion channel

an ion channel that opens or closes according to the value of the membrane potential

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membrane potential

because more potassium ions are allowed to come outside than sodium ions are allowed to come inside, this creates a slightly negative charge inside the cell. -70mV

35

sodium potassium pump

exchanges 3 sodium ions with 2 potassium ions. this creates an electrical changes inside the membrane (electrical potential)

36

rate law

the rate of firing determines rate of reaction to a stimulus. high rate=strong muscle contraction

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decremental conduction

the decrease in teh size of the disturbance as it travles along an axon

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transport proteins

fill vesicles with neurotransmitter

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trafficking proteins

release neurotransmitter and recycling vesicle

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ligand

chemical that attaches to the binding site near ligand-gated channels 

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ionotripic receptors

contains a binding site for a neurotransmitter and an ion channel that opens when a molecule of the neurotransmitter attaches to the binding site
send info about hyperpolarizing and depolarizing 

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metabotropic receptors

involve steps that require the cell to expend metabolic energy
located close to G protein, which activates an enzyme that stimulates production of a second messenger
these attach near ion channels and cause them to open
the second messengers can turn genes on or off 
receptor in different place than channel
 

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excitatory postsynaptic potential

(EPSP)

when sodium channels open and result in depolarization

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inhibitory postsynaptic potential

(IPSP)

the efflux of potassium that results in hyperpolarization

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enzymatic deactivation

accomplished by enzyme that destroys molecules of neurotransmitter
this termination is done for acetylcholine and neurotransmitters consisting of peptides

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acetylcholinesterase
 

an enzyme that makes the postsynaptic potentials of ACh short lived by AChE cleves into choline and acetate

47

physostigmine

a drug that deactivates acetylcholinesterase
prolongs effects of ACh
 

48

neuromodulators

chemicals released by neurons that travel farther and are dispersed more widely than NT

not restricted to the synaptic cleft; diffuses through the extracellular fluid 

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autoreceptor

receptor molecule located on a neuron that responds to NT released by that neuron. no changes in membrane potential. instead, they regulate internal processes like the synthesis and release of neurotransmitters.

metabotropic

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presynaptic inhibition

decreases the amount of neurotransmitter released by the postsynaptic bouton

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presynaptic facilitation

increases the amount of neurotransmitter released by postsynaptic terminal bouton

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target cells

cells that contain receptors for a particular hormone

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motor neuron

neurons located within the CNS that control the contraction of a muscle 

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interneuron

a neuron located entirely w/in the CNS btw sensory and motor neurons 

local interneurons: form circuits w/ neurby neurons and analyze small pieces of information

relay interneurons: connect circuits of local interneurons in one region of the brain with those in other regions