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37 Cards in this Set
- Front
- Back
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what is a neuron |
a neuron is a nerve cell that rapidly carries electrical impulses from one point of the body to another. |
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what is a nerve |
many neurons grouped together as one structure |
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The Central Nervous System is |
- composed of the brain and spinal cord - made of relay neurons - receives sensory info from receptors by sensory neurons (sensory organs) - interprets info received (brain) - processes info received - initiates motor response through motor neurons if a response is needed |
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what is the peripheral nervous system made of |
sensory and motor neurons |
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what are the two categories of peripheral nerves |
spinal nerves (spinal cord) and cranial nerves (brian) |
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what are the features of the spinal nerves
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- composed of 31 pairs - emerge directly from the spinal cord - spinal nerves are mixed nerves: both sensory nerves and motor nerves |
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what are the features of the crainal nerves |
- composed of 12 pairs - emerge from the brainstem - ex: optic nerve carries visual info from the retina to the brain (eyes, ears, nose, mouth) |
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what are the two types of nerves |
sensory nerves: takes messages from sensory organs to spinal cord and brain motor nerves: takes messages from spinal cord and brain to or |
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what are the parts of a neuron |
- cell body - dendrites - nucleus - axon - myelin sheath - nodes of Ranvier - terminal dendrites - terminal buttons - synaptic terminals of axon |
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direction of a nerve impulse |
dendrite -> cell body -> axon -> terminal axon -> terminal button |
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what are the 3 kinds of nuerons and how do they connect |
sensory neuron (sensory organs) (message) -> association neuron (brain and spinal cord) (translation) -> motor neuron (organs and muscles) (action) |
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what is a nerve impulse |
communication along the nervous system takes place in a form similar to an electrical pulse known as action potential |
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what unit of measurement is an action potential |
action potential has voltage and is measured in millivolts |
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what is the myelin sheath |
the myelin sheath is a membrane that covers the axon. it acts as an insulator and it increases the rate at which the action potential flows through the axon. |
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what are the different ions to note |
Na+ = sodium K+ = potassium Ca2+ = calcium Cl - = chloride |
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what are voltage-gated channels |
protein channels in the cell membrane that open in response to a change of the electric potential of the cell membrane. |
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what are Ligand-gated channels |
membrane protein channels that open by responding to chemical messengers such as a neurotransmitter. ligand is a molecule that binds to another molecule. |
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what is resting potential |
the stage when the cell is not sending an impulse but is ready to send one. it is said to be polarized. |
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how is resting potential achieved |
- using active transport (sodium-potassium pump) most sodium ions are transported out of the axon into the intercellular fluid and most potassium ions are transported into the cytoplasm of the nuron - there are negatively charged organic ions permanently located in the cytoplasm of the axon - the cell membrane contains voltage-gated sodium and potassium channels, in resting potential the sodium channels are closed and some potassium channels are open - the movement of positive ions results in a negative net charge outside the axon membrane |
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whats the difference between polarized, depolarized, and repolarized |
polarized is when there is a net negative charge inside the axon membrane and a net positive charge outside. (at rest). depolarized is when the inside of the cell becomes positively charged and the outside becomes negatively charged. (neurons sending an impulse) repolarized is after depolarization when the inside is negative and the outside is positive. (return to resting) |
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what happens during depolarization |
- voltage-gated sodium channels open and close rapidly allowing sodium ions to diffuse into the cell. - the area in which the sodium ions entered initiates the adjacent area of the axon to open up the sodium channels - the rapid diffusion of positively charged ions in addition to the potassium ions that are already inside reverses the charge inside the cell membrane relative to the outside of the cell. - the inside becomes positively charged and outside negative. - this is called the action potential |
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what happens during repolarization |
- before sending another impluse, sodium and potassium ions need to be restored to the resting potential - membrane channels open for positively charged potassium ions to diffuse out - the decrease in potassium ions causes the inside of the cell membrane to become negatively charged - then the sodium-potassium pump activates |
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what is the refractory period |
the time taken by one neuron to depolarize and repolarize. during the refractory period, the sodium channels are inactive and will not open or respond to a stimulus that can cause a second action potential |
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what does it mean to be myelinated |
the axons of neurons of organisms ith an advanced nervous system have myelin sheath |
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what is myelin sheath made of |
schwann cells that wrap themselves around the axon several times to form layers around the axon. |
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what are nodes of ranvier |
the small gaps in between the schwann cells |
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what is saltatory conduction |
the phenomenon in which impulses skip from one node of ranvier to another. the movement of ions doesn't pass through the myelin because its insulated and doesn't allow ions to pass through it. the movement of ions only occurs in the nodes of ranvier. this works because the cytoplasm is electrically conductive and it conducts the impulse from one node to the next. |
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what are the advantages of saltatory conduction |
1. the impulse in the myelinated fibers moves faster than non-myelinated fibers which is important for efficient neural processing for organisms with high functioning nervous systems 2. less energy (ATP) is used as sodium-potassium pump has to re-establish resting potentials at nodes of ranvier only |
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stimulus threshold peak time voltage |
stimulus: -70 threshold: -55 peak: +40 time: (ms) 1.3.5 voltage: mV |
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synapses def |
the chemical communication between two cells |
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a sensory pathway is... |
unidimensional |
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sensory neuron line up |
dendrite of cell 1 -> cell body of 1 -> axon of 1 -> synaptic gap -> dendrite of cell 2 -> cell body of 2 -> axon of 2 -> synaptic gap -> etc. |
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what are different patterns of synaptic connections |
one to one one to many many to one |
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what is a neurotransmitter, where are they located, and give an example |
neurotransmitters are chemicals used for synaptic transmission. located in the terminal buttons. ex) acetylcholine |
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explain the mechanism of synaptic transmission |
when an action potential reaches the terminal buttons: - the calcium ion channels open - calcium ions diffuse into terminal buttons - calcium ions cause the vesicles the fuse with the plasma membrane and release the neurotransmitter into the synaptic gap by exocytosis - the neurotransmitter diffuses across the synaptic gap from pre to post nuron - neurotransmitter binds with receptor on post nuron - the binding causes ligand-gated channel to open and sodium ions to diffuse through the channel which initiated the action potential in the post nuron - enzymes degrade the neurotransmitter and cause it to detatch from the receptors - sodium ion channels close - neurotransmitter fragments diffuse back across the synaptic gap to the terminal buttons of the pre where they're reassembled |
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where can synapses occur |
where a motor nuron meets a muscle tissue. the junction where a nuron sends a neurotransmitter to a muscle tissue is known as a motor plate. synapses also occur between a receptor and a sensory neuron |
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what is neonicotinoid |
it is a kind of insecticide that is chemically similar to nicotine and it can bind to post synaptic receptors that receive acetylcholine so when acytlcholine is released in the synaptic gap, it is blocked and cannot create a action potential in the post. the enzyme acetylcholinesterase that usually breaks down acetylcholine cannot breakdown neonicotinoid and the receptors stay permanently blocked |
