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40 Cards in this Set

  • Front
  • Back
What does the nervous system consist of?
The central nervous system (CNS) and peripheral nerves; made of cells called neurons.
What are neurons?
The cells of the nervous system; they carry rapid electrical impulses
What carries nerve impulses from the receptors to the CNS?
sensory neurons
What carries nerve impulses within the CNS?
relay neurons
What carries nerve impulses from the CNS to effectors?
motor neurons
You are playing soccer. You see a ball coming towards you and then you kick it. Describe what your nervous system is doing during thes process.
Receptors in your eye (photoreceptors) note that the ball is coming towards you and start a nerve impulse. Sensory neurons send this nerve impulse to your brain. Within the brain, the nerve impulse is in relay neurons. The brain sends a message to your leg muscles (the effectors that will do the responding action). This message is a nerve impulse that will travel through the peripheral nerves, which are made of motor nerurons.
On the nervous system diagram, what is A?
motor end plate
On the nervous system diagram, what is B?
Schwann cell
On the nervous system diagram, what is C?
node of Ranvier (or axon)
On the nervous system diagram, what is D?
axon
On the nervous system diagram, what is E?
cell body
On the nervous system diagram, what is F?
nucleus
On the nervous system diagram, what is G?
dendrite
Define resting potential
the electrical potential of a neuron at rest; the inside of the cell is more negative than the outside; -70 mV (millivolts)
Define action potential
when the neuron is at +40mV; the rapid change in membrane potential of a neuron caused by opening and closing of voltage-sensitive gates in sodium and potassium ion channels
What is depolarization?
the inside of the neuron is made less negative relative to the outside; the neuron's potential increases from the resting potential of -70mV
What is repolarization?
th inside of the neuron becomes more negative relative to the outside; the neuron's potential drops from the action potential of +40 mV
On the nervous system diagram, what is 1?
depolarization
On the nervous system diagram, what is 2?
action potential
On the nervous system diagram, what is 3?
repolarization
On the nervous system diagram, what is 4?
resting potential
Where in the nervous system diagram (graph) do voltage-gated sodium ion channels open?
1
Where in the nervous system diagram (graph) do voltage-gated potassium ion channels open?
3
Describe the ion distribution of the neuron at rest and the state of the ion channels.
high Na+ outside, high K+ inside; overall more positive outside than inside; the gated Na+ and K+ channels are closed
What must you include in a drawing of a neuron for IB?
cell body drawn and labeled with a nucleus shown inside; axon drawn at least five times as long as the diameter of the cell body and labeled; myelin sheath drawn and labeled; gaps in the myelin sheath labeled as nodes of Ranvier; at least five dendrites drawn leading to the cell body and labeled; at least two motor end plates / synaptic knobs drawn and labeled
What returns sodium and potassium ions to their original locations after repolarization?
sodium-potassium pump
What ions move during depolarization of a neuron? Where/how?
Na+ (sodium ions) moves in through voltage gated sodium ion channels out of the neuron (causing the increase). These open in response to the diffusion of ions from an adjacent region that is undergoing an action potential once the threshold potential is reached.
What ions move during repolarization of a neuron? Where/how?
K+ (potassium ions) move through voltage-gated potassium channels into the neuron (causing the potential to decrease). The sodium channel are closed/inactive during this period.
What direction do nerve impulses within neurons go? What prevents nerve impulses from going in both directions simulataneously?
dendrites to cell body to axons; refractory period
Describe the structure/function of the following part of a neuron: dendrites
pick up messages from other neurons. Many branches means a large surface area. Lots per cell.
Describe the structure/function of the following part of a neuron: cell body
contains major cell organelles including the nucleus and mitochondria needed for normal cell activity
Describe the structure/function of the following part of a neuron: axon
very long extension that quickly transmits the nerve impulse. These branch at the end. The ends flatten to make a motor end plate which is used when the axon of one neuron send a message to the dendrite on the next neuron
Describe the structure/function of the following part of a neuron: myelin sheath
insulating layer made of Schwann cells; speeds up the nerve impulse and saves energy while the impulse is traveling
Describe the structure/function of the following part of a neuron: nodes of Ranvier
non-myleinated gaps between the Schwann cells in the myelin sheath. The nerve impulse in a myelinated nerve travels from node to node (N.B. we will study nerve impulses only in non-myelinated nerves)
Describe the process of depolarization of a neuron
local currents / ions diffuse from adjacent depolarised section of axon; resting / membrane potential reduced; voltage-gated ion channels (for sodium) affected; sodium channels open; sodium diffuses in (moves in rapidly); therefore fewer positive charges outside and more inside; inside becomes positive relative to outside; before depolarisation outside was positive relative to inside
Describe how the neuron goes from the action potential back to its resting state.
Voltage-gated sodium channels close; Voltage-gated potassium channels open, K+ diffuses out of cell rapidly. This restores the resting potential; Notice that the Na+ and K+ are in different locations than at the beginning of the process. Also, the voltage-gated sodium channel are not capable of opening for a little while. This prevents the impulse from traveling backwards; Sodium-potassium pumps move Na+ out and K+ in to restore the neuron to its original conditions
The signals within a neuron are________; the signals between neurons are ______________.
electrical, chemical
What is the space between two adjacent neurons called?
synapse or synaptic cleft
What do you call the signaling molecules that allow one neuron to cause another neuron to begin an nerve impulse?
neurotransmitters (examples include acetylcholine, dopamine, serotonin)
Explain the principles of synaptic transmission
nerve impulse travels to end of presynaptic neuron; triggers influx of Ca2+ through voltage-gated calcium channels; causes synaptic vesicles to fuse with membrane; release neurotransmitter molecules (acetylcholine, GABA, dopamine, serotonin, etc) into synaptic cleft; neurotransmitter crosses / diffuses across channel; neurotransmitter binds to receptors on postsynaptic neuron; causes ion channels to open on neuron. For example, Na+ can diffuse into postsynaptic neuron; can inhibit/excite receiving by hyperpolarizing/depolarizing; if enough sodium enters then the cell starts an action potential; neurotransmitter degraded; Ca2+ in presynaptic neuron pumped back into the synaptic cleft