Kinesiology 02

Front 1

conduction of action potential from presynaptic neuron to post synaptic neuron

Back 1

presynaptic --> releases neurotransmitters --> synaptic cleft --> cross to neurotransmitter receptors on postsynaptic neuron --> passes signal along axon of post-synaptic neuron --> it becomes more permeable to Na+ --> Na+ enters, causes graded potential --> action potential transfers down post-synaptic axon.

Front 2

summation

Back 2

combination of many small depolarizations adding to one another in space and time. If enough depolarizations in a summation occur to reach the threshold potential, an action potential is generated.

Front 3

how membrane potential comes about and how it's maintained in a neuron

Back 3

large depolarization occurs as a result of stimulus, action potential is generated, opens voltage regulated channels at hillock, causes more voltage reg. channels to open,(pos.feedback) all down axon until termination. Voltage gated Na+ terminals then close, lastly slower K+ channels close. Closing of these causes net movement of pos. ions out of cell (na+ stops diffusing in, K+ diff. out.) returning axon to norm. Na+-K+ pump has same purpose in neuron.

Front 4

absolute refractory period

Back 4

period after an action potential during which another action potential can not be generated as the channels are still open.

Front 5

post synaptic neuron

Back 5

the neuron that is activvated by the neurotransmiitter at a synapse.

Front 6

gap junction

Back 6

Special proteins in muscle cells that extend from cell membranes to function as "tubes" joining to gap junctions in adjacent cells, and allowing the transmission of electrically charged ions between cells. Gap junctions allow these electrical signals to pass between cells at distances that electrical signals couldn't normally jump. This allows for the action potential in one muscle cell to the next, allowing for contraction of the muscle

Front 7

why is energy required to pump Na+ out of cell

Back 7

cell membrane not as permeable to Na+, won't diffuse out on its own, plus, going against electrical gradient, so requires energy.

Front 8

neurohormones

Back 8

released by neuroendocrine cells, chemical messengers which nerve cells release into the bloodstream to effect another area of the body such as oxytocin which influences milk output of the mammary gland in response to suckling.

Front 9

Explain the synaptic delay

Back 9

half a millisecond - time it takes for the neurotransmitter to be released, cross the synaptic cleft, activate the post-synaptic neuron to become more permeable, and for Na+ to enter and cause the graded potential.

Front 10

concentration gradient

Back 10

difference in concentration of ions in solution on either side of a selectively permeable membrane

Front 11

convergence versus divergence - significance?

Back 11

convergence - many neuron inputs join to one. divergence - one to many. Significance - input from many senses goes towards one 'reaction.' sight of steak, hear sizzle, smell it, all contribute to a neuron to induce hunger. Or, input from vision, muscular control, memory, emotions, all go to control an action - jump shot.

Front 12

synaptic transmission

Back 12

transfer of information from neuron to another cell by chemical means.

Front 13

Hormones

Back 13

chemical messengers that are secreted by glands- travel throughout the entire body, have one or more targets and many different effects, but receptor cells in target areas elicit different responses.

Front 14

axon hillock

Back 14

where the cell body of the neuron narrows to become the axon, the first region where voltage-gated ion channels occur, and where action potentials are generated.

Front 15

convergence

Back 15

joining of the output of many pre-synaptic neuron into one post synaptic neuron.

Front 16

net diffusion

Back 16

the total movement of ions across a selectively permeable membrane until a balance is reached in both electrical charge and ion concentrations on both sides of the membrane.

Front 17

divergence

Back 17

one nerve cell providing output to numerous post-synaptic cells.

Front 18

axon collateral

Back 18

side branch of an axon.

Front 19

how is active transport important in ensuring that action potentials can be generated. Discuss why important

Back 19

creates potential as a side benefit, but changing ion concentrations, thus creating the potential across the membrane. The electrical charge is the basis for action potentials to be possible. Other importance of active transport - ion regulation ensures cell volume homeostasis.

Front 20

relative refractory period

Back 20

period following an action potential when the membrane is nearly back to resting potential, and during which another action potential can be generated, IF, the stimuli is stronger than usual.

Front 21

How can a post synaptic neuron become hyperpolarized?

Back 21

certain neurotransmitters produce depolarizing graded potentials that reduce the chance that an action potential will be generated.

Front 22

synapse

Back 22

a specialized junction that allows communication between a neuron cell and another cell type.

Front 23

Sim & diff between graded and action potentials

Back 23

both cause changes in membrane potential, but action a large, rapid change, sweeps down axon and can't be stopped once started. graded have different levels, can be small changes. Produced by chemically gated channels opening due to binding of a receptor.

Front 24

all-or-none rule of action potentials

Back 24

action potentials are alike in amplitude and shape, so you either generate one, or not.

Front 25

autocrine factor

Back 25

localized chemical messengers which release their chemical message into the extra-cellular space, but effect their own cell. (An autocrine factor may be, as an example, a factor which stops a cell from entering the cell division phase of life.)

Front 26

active transport

Back 26

The active movement of molecules through the cell membrane by proteins. Primary active transport transports molecules by using the energy generated from the breakdown of Adenosine tri-phosphate into Adenosine di-phosphate (and water) while secondary active transport uses the wasted energy created in the process of moving one molecule across the cell membrane, to move a second (bonus) molecule across the membrane as well.

Front 27

hormone

Back 27

chemicals secreted by glands to travel via the bloodstream to another body site to exert its effect

Front 28

neuroendocrine cells

Back 28

neurons with axon terminals not by another neuron but which instead release neurohormones into the bloodstream.

Front 29

paracrine factor

Back 29

localized chemical messengers synthesizing and releaseing their chemical messages from cells to deliver their message via the extracellular space to their nearby target cells.

Front 30

How an action potential moves along the axon of a nerve cell

Back 30

review and add answer.

Front 31

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Back 31

(Axon drawing)
dendrites
cell body
axon hillock
axon collateral
axon terminal

Front 32

repolarization

Back 32

the return of the membrane potential to normal resting potential

Front 33

prostaglandins

Back 33

a group of paracrine factors found in nearly every organ and tissue and made up of fatty acids.

Front 34

Differences between chemical and electrical gradient

Back 34

ion concentration versus charge across a membrane.

Front 35

depolarization

Back 35

when the inside of the cell becomes less polarized by additional Na+ positive ions entering it, reducing the membrane potential.

Front 36

hyperpolarization

Back 36

When the membrane potential is much more negative than normal, the membrane is hyperpolarized. This is caused by the outward diffusion of positively charged ions, leaving a surplus of negative ions.

Front 37

electrochemical gradient

Back 37

combination of concentrations and voltages at which chemical forces move ions.

Front 38

axon terminals

Back 38

at the end of the axon, specialied region for transmitting information to another cell.

Front 39

graded potential

Back 39

a change in the polarity and permeability of the cell membrane when chemically gated channels open due to binding of a particular receptor.

Front 40

threshold potential

Back 40

the membrane potential at which an action potential is generated.

Front 41

selective permeability

Back 41

the ability of some membranes to allow certain substances to pass through them, but not other substances.

Front 42

voltage gated Na+ channels

Back 42

channels within the axon hillock and axon which, when activated by an electrical impulse, allows the passage of positively charged sodium through the channel.

Front 43

membrane potential

Back 43

the difference in charge between cell exterior versus interior. Most membranes are about 70 mV. Generally more positively charged ions outside of cell - this causes the potential, which is then available to perform work. Active pumping of sodium and potassium through protein pumps enhances the potential.

Front 44

electrical gradient

Back 44

a difference in electrical charge across a selectively permeable membrane that causes net movement of positive ions toward the negatively charged side of the membrane.

Front 45

action potential

Back 45

a large and rapid change in membrane potential that sweeps down the axon and cannot be stopped once started.

Front 46

nodes of ranvier

Back 46

points where myelinated sheath are interrupted, in effect, a new action potential is created at each one.

Front 47

myelinated axon

Back 47

a nerve cell that is coated at regular intervals with a myelin insulative coating.

Front 48

resting membrane potential

Back 48

the normal potential of the membrane when not receiving sensory input. About 70mV. Potential is generated by the difference in charge between the interior and exterior of the cell.

Front 49

presynaptic neuron

Back 49

neuron that releases a neurotransmitter at a synapse in response to an action potential in its axon

Front 50

synaptic bulb

Back 50

at the axon terminal of a presynaptic neuron, the bulb contains chemical neurotrnamitters that are packaged in vessicles and released after an action potential into the synaptic cleft (the space between a pre and post synaptic nerve cell.)

Front 51

neurotransmitter

Back 51

a chemical released from a pre-synaptic neural axon that delivers a chemical message across the synaptic cleft to the neurotransmitter receptors on the post synaptic neuron.

Front 52

function of the Na+ - K+ pump

Back 52

controls the total number of solutes in the cell to maintain homeostatic cell volume. The action potential produced is an indirect benefit, as is the secondary active transport of other molecules that the cell needs - i.e. use of facilitated diffusion to brind in other required molecules.

Front 53

saltatory conduction

Back 53

impulse conduction from node to node (ranviers nodes). This is a much faster form of impulse conduction because it doesn't require the opening and closing of ion channels. Allows for increased conduction speed without increasing the diameter of the axon.