midterm1 Flashcards
which system exerts control by sending hormones through the blood and lymphatic systems?
endocrine
T/F- all body cells have membrane potential
true
what are excitable tissues
They are tissues that when excited, change their resting potential to produce electrical signals.
when membrane potential becomes more positive (moving towards 0mV), it is said to be _____
depolarized
when the membrane returns to its normal resting potential after being depolarized
repolarization
when there is an increase in negative membrane potential, i.e. the potential becomes more polarized or more negative
hyperpolarization
channels which are always open (unregulated flow), that allow water soluble ions to cross the plasma membrane. Each ion has it’s own specialized channel it can leak through.
leak channels
this type of channel has gates which can either be opened or closed. Whether the gate is opened or closed is determined by the protein’s 3-dimensional conformation.
gated channels
gated channels which open or close in response to a change in membrane potential
voltage gated channels
gated channels which change in response to the binding of a specific chemical messenger to a membrane receptor in close association with the channel.
chemically gated channels
gated channels which respond to mechanical changes such as stretching or other types of deformation.
mechanically gated channels
gated channels which open or close in response to local changes in temperature (heat or cold)
thermally gated channels
substances what have low resistance and therefore provide little hindrance to current flow, ex. electrical wire, ICF and ECF.
conductors
substances which have high resistance and therefore impede the movement of charge, ex. plastic (which is why it surrounds wires), body lipids.
insulators
the gradual spread and loss of a graded potential
decremental loss
give examples of graded potentials
postsynaptic potentials, receptor potentials, end-plate potentials, pacemaker potentials, slow wave potentials
overshoot
the portion of the action potential during which the potential is reversed
when a excitable membrane is triggered to undergo an action potential
fire
Pna+
At threshold potential, there is an explosive increase in Na+ permeability, symbolized by Pna+, as the membrane swiftly becomes 600 times as permeate to Na+ as to K+
the part of the action potential due to the Na+ influx
rising phase
the part of the action potential brought on by K+ efflux
falling phase
the ____ and ___ of a neuron is the input zone
cell body and dendrites
Once initiated, the velocity, or speed, with which an action potential travels down the axon depends on which two factors
(1) whether the fibre is myelinated and (2) the diameter of the fibre. Contiguous conduction occurs in unmyelinated fibres
most common excitatory inhibitor in the brain
glutamate
most common inhibitor neurotransmitter
GABA
are EPSPs and IPSPs action or graded potentials?
graded potentials
membranous sacs containing hydrolytic enzymes
lysosomes
membranous sacs containing oxidative enzymes
peroxisomes
dispersed within the cytosol and facilitate intracellular reactions involving degradation, synthesis, and transformation of small organic molecules
intermediary metabolism enzymes
maintain asymmetric cell shapes, coordinate complex cell movements, transport of secretory vesicles, main structural and functional component of cilia/flagella
microtubules
the six organelles
the ER, Golgi, lyosomes, peroxisomes, mitochondria and vaults.
site of synthesis of proteins and lipids destined for the cell membrane and secretion
rough ER
muscle cells have a ____stores calcium, needed to facilitate muscle contraction and movement.
sarcoplasmic reticulum
membrane enclosed sacs, which are not in physical contact with one another. They are thin in the middle but have dilated, bulging edges.
cisternae
are peroxisomes smaller than lysosomes?
yes
an antioxidant enzyme that decomposes potent H2O2 into harmless H2O and O2
catalase
purpose of mitosis in multicellular organisms
growth and replacement
the interval of time between cell division (as all cells capable of dividing alternate between periods of mitosis and nondivsion)
interphase
chromatin condenses and duplicates (creates inter chromatids) but remain joined at the cetromere. Centrioles divide and the daughter centrioles move to opposite ends of the cell where they form mitotic spindles (made of microtubules). The membrane around the nucleus starts to break down
prophase
Nuclear membrane disappears. The chromosomes align in the middle and attach to the mitotic spindles at their centromeres.
metaphase
The centromeres split and separate the chromatids, moving the chromosomes toward opposite ends of the cell. Molecular motors pul the chromosomes along the spindle fivers (46 chromosomes at either end of the cell)
anaphase
the cytoplasm divides through the formation of an actin contractile ring forming to diploid cells (each with a full set of chromosomes). The spindles disassemble and the chromosomes uncoil into their decondensed chromatin form while a new nuclear membrane forms.
telophase
Any flow of electrical charges is called a ___
current
T/F - An impulse may be triggered during the refractory period, provided the stimulus is strong
true
the part of the nueron that contains the nucleus and organelles; also called soma.
cell body
side branches that extend off the axon.
collateral
Because of the all-or-none nature of action potentials, the ____ of a stimulus affects the number of action potentials, not the speed of their propagation
strength
areas located between the myelinated regions where the axonal membrane is exposed to the ECF.
nodes of ranvier
which nerve fibres can regenerate?
Cut axons in the peripheral nervous system can regenerate, whereas those in the central nervous system cannot
a tube formed by Schwann cells when there is a cut axon in a peripheral
regeneration tube
the five events that occur at the synaptic cleft
- The action potential of the presynaptic neuron triggers voltage-gated calcium channels in the synaptic knob.
- This releases calcium ions into the cleft.
- The addition of calcium causes the release of neurotransmitters through exocytosis.
- The neurotransmitters diffuse across the gap and bind to postsynaptic receptors.
- This activates gated ion channels on the postsynaptic neuron.
These five events produce a graded potential in the postsynaptic neuron.
A neuron may terminate on what 3 structures
a muscle, a gland, or another neuron
when a neuron terminates on a muscle or a gland, the neuron is said to
innervate or supply the structure
____allow an influx of potassium or chloride ions, which hyperpolarizes the membrane and reduces the probability that the neuron will reach threshold
Inhibitory synapses - leading to an IPSP
neurotransmitters are removed from the synaptic cleft by______
diffusion, enzyme degradation, or absorption by the presynaptic axon terminal.
the total potential in the postsynaptic neuron; or sum total of all EPSPs and IPSPs occurring at approximately the same time
grand post synaptic potential
two ways a postsynaptic neuron can be brought to threshold
temporal and spatial summation
Only if an excitatory presynaptic signal is_______ through summation will the information be passed on.
reinforced by other supporting signals
why do action potentials initiate at the axon hillock?
because this region has a much greater density of voltage-gated Na+ channels than anywhere else in the neuron.
larger molecules made up of anywhere from 2 to about 40 amino acids
neuropeptides
where are neuropeptides synthesized?
in the neuronal cell body in the endoplasmic reticulum and Golgi complex and are subsequently moved by axonal transport along the microtubular highways to the axon terminal.
chemical messengers that do not cause the formation of EPSPs or IPSPs, but rather bring about long-term changes that subtly modulate – depress or enhance – traction of the synapse. They bind to neuronal receptors at non-synaptic sites – not at the sub synaptic membrane – and they do not directly alter membrane permeability and potential.
neuromodulators
the depression of synaptic effectiveness because a third neuron between a presynaptic ending and post synaptic ending can influence the activity.
presynaptic inhibition
results in the enhancement of synaptic effectives
presynaptic facilitation
any biological substance that when consumed will in some way alter the biological function of the organism.
a drug
4 possible drug actions
(1) altering the synthesis, axonal transport, storage, or release of a neurotransmitter; (2) modifying neurotransmitter interaction with the postsynaptic receptor; (3) influencing neurotransmitter reuptake or destruction; and (4) replacing a deficient neurotransmitter with a substitute transmitter.
injection of cocaine blocks _______
reuptake of the neurotransmitter dopamine at presynaptic terminals.
why is cocaine addictive?
it causes long-term molecular adaptations of the involved neurons such that they cannot transmit normally across synapses without increasingly higher doses of the drug. The postsynaptic cells become accustomed to high levels of stimulation and become ‘’hooked’’ on the drug
desensitization to an addictive drug so that the user needs greater quantities of the drug to achieve the same effect.
tolerance
attributable to a deficiency of dopamine in the basal nuclei, a region of the brain involved in controlling complex movements. This movement disorder is characterized by muscular rigidity and involuntary tremors at rest, such as involuntary rhythmic shaking of the hands or head
parkinsons disease
act at different synaptic sites to block inhibitory impulses while leaving excitatory inputs unchecked
tetanus toxin and strychnine
prevent the release of GABA from inhibitory presynaptic input terminating at neutrons that supply skeletal muscles. Unchecked excitatory input to these neurons result in uncontrolled muscle spams (early in the disease this is the jaw- lockjaw)
tetanus toxin
ompetes with glycine at the postsynaptic receptor site. This poison combines with the receptor but does not directly alter the potential of the postsynaptic cell in any way, instead it blocks the receptor so that it is not available for interaction with glycine when the latter is released from the inhibitory presynaptic ending
strychnine
the branching of axon terminals so that a single cell synapses with and influences many other cells.
divergence