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Bio 203 Ch. 12 Study Guide Part 2

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Course

Anatomy And Physiology II (BIOL 1300)

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Academic year: 2018/2019
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Jack Robinson
Franklin Pierce University
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CHAPTER 12 PART 2: Nervous Tissue Physiology

(Sections 12 – 12)

Vocabulary:

Polarized Resting membrane potential Sodium-potassium pump Stimulation Depolarized Repolarized Graded (local) potential Excitatory postsynaptic potential (EPSP)

Inhibitory postsynaptic potential (IPSP) Action potential Threshold Hyperpolarization Refractory period Absolute refractory period Relative refractory period Unmyelinated fibers

Saltatory conduction Continuous conduction Presynaptic neuron Postsynaptic neuron Synaptic clef Neurotransmitter Ligand-gated channel Voltage-gated channel

Required Core Objectives:

  1. Describe resting membrane potential and what factors determine and maintain it. Resting membrane potential is when the cell is at rest but has the potential to be excited and fire. It’s the electrical potential difference across the plasma membrane when the cell is in a non-excited state. It exists because of unequal electrolyte distribution between extracellular fluid (ECF) and intracellular fluid (ICF). There are more negatively charged particles on the inside of the membrane (ICF) than the outside (ECF). Resting membrane potential results from 3 factors: 1) Ions diffuse down their concentration gradient through the membrane, 2) the plasma membrane is selectively permeable and allows some ions to pass easier than others, and 3) electrical attraction of cations (positively charged ions) and anions (negatively charged ions) to each other.

Define: a. electrical potential: The difference in the concentration of charged particles between one point and another. It’s a form of potential energy that, under the right circumstances, can produce a current. b. electrical current: A flow of charged particles from one point to another. Currents indicate the flow of positively or negatively charged ions across the resistance of your cells’ membrane. c. resting membrane potential: The charge difference between the plasma membrane.

Which ion has the greatest influence on membrane potential? Potassium. Is there a higher concentration of K+ inside or outside the cell? Outside. Is the cell membrane more permeable to K+ or Na+ ions? K+ Is there a higher concentration of Na+ ions inside or outside the cell? Inside. This difference in ions is called Polarization.

  1. Relate sodium potassium pump to resting membrane potential. Explain how the Na+/K+ pump works: Sodium leaks out of the cell and potassium leaks into the cell. The sodium-potassium pump continually compensates for this leakage by pumping 3 sodium ions out of the cell and 2 potassium ions into the cell. How many Na+ and K+ ions are pushed through it? 3 Na+ ions move out and 2 K+ ions move in. How much of the total energy of the nervous system is used to fuel it? 70%. Where does this energy come from? ATP (Adenosine triphosphate).

  2. Explain how stimuli can cause changes in the resting membrane potential. When a neuron is stimulated, it creates an impulse in the form of an action potential, which causes sodium to enter the cell, resulting in depolarization. At the peak of the action potential, potassium enters the cell, causing it to become

hyperpolarized, thus changing the voltage of the cell, and changing the resting membrane potential.

What are some of the stimuli that can activate neurons? Touch, sound, light, pressure, heat, chemical information from other cells. When this occurs, Sodium (Na+) ions rush into the neuron causing depolarization. The flow of Na+ along the inside of the membrane causes a current that travels toward the trigger zone of the neuron, causing a local potential.

  1. Be able to diagram, label, and explain the phases of an action potential.

What is an action potential? An action potential is a rapid sequence of changes in the voltage across a membrane. This is produced by voltage-gated ion channels. It’s a rapid up-and-down shif in voltage.

Where is it initiated? Axon Hillock. What is the “threshold” that must be reached to cause an action potential? Typically, about -55mV. As more and more Na+ channels in the membrane open through a positive-feedback mechanism, a rapid rise in membrane voltage, called a Action Potential occurs. As Potassium (K+) ions are repelled by the positive charge inside the cell, they flow out, causing Repolarization. As the membrane potential becomes MORE negative than it was at the start, there is a brief period of Hyperpolarization where the neuron is harder to stimulate.

  1. Explain why action potentials are considered “all-or-none”. If the threshold (~ -55mV) is reached, the neuron fires at maximum voltage. If the threshold isn’t reached, the neuron doesn’t fire. The neuron either fires at maximum voltage or doesn’t fire at all; it’s non-decremental and irreversible.

  2. Differentiate between a graded (local) and action potential. Action potentials are “all-or-nothing”, meaning if threshold is reached, they neuron fires at maximum voltage, whereas graded (local) potentials are reversible, meaning if stimulation ceases, threshold isn’t reached, and cell goes back to RMP. Local potentials are produced by gated channels on the dendrites and soma, whereas action potentials are produced by voltage-gated channels on the trigger zone of the axon. Local potentials are also decremental – the signal grows weaker with distance, whereas action potentials are nondecremental, meaning the signal remains the same strength regardless of distance.

  3. Identify the key steps that take place in a chemical synapse. What is a synapse? The gap between two cells, where electrical or chemical signals are released.

What is the role of the presynaptic neuron? Transmits a signal toward the synapse.

What is the role of the postsynaptic neuron? Transmits a signal away from the synapse.

A presynaptic neuron stores pre-made neurotransmitter in synaptic vesicles. Once the signal gets all the way to the synaptic knob, it triggers the releases of these chemicals into the synapse. Post-synaptic neurons have protein receptors for these neurotransmitters that bind and trigger the opening of ligand-gated ion channels in their membrane. How many neurotransmitters have been identified? 6: Acetylcholine, norepinephrine, glutamate, GABA, serotonin, and dopamine.

List the four classes of neurotransmitters and give one or more examples of each type.

a. Acetylcholine: Acetylcholine

b. Amino Acids: glycine, glutamate, aspartate, and GABA

c. Monoamines: Epinephrine, norepinephrine, dopamine

d. Neuropeptides: Cholecystokinin and substance P

Why is it that one neurotransmitter can have different effects in different target cells in the body?

Some neurotransmitters are excitatory while others are inhibitory, and the transmitters effects differs depending on the type of receptor on the postsynaptic cell.

Synapses are required because they enable interconnection between neurons. They enable each axon to connect with many dendrites at the same time.

What is neural integration? The ability to process, store, and recall information and use it to make decisions.

  1. Differentiate between electrical and chemical synapses. What is the difference between an electrical synapse and a chemical synapse? Chemical synapses relay information through chemicals, slowly and steadily, while electrical synapses use electricity, which is quicker, however, less flexible.

What is a gap junction? A direct point of contact which allows ions to flow directly.

Where are electrical synapses found? The brain

What are the advantages of electrical synapses? Electrical synapses allow rapid, two-way communication.

What are the disadvantages of electrical synapses? As the signal transmits from one neuron to another, the electrical synapse become weaker.

  1. Explain the difference between IPSPs and EPSPs. ISPSs inhibit action potentials to be fired, whereas ESPSs facilitate action potential firing.
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Bio 203 Ch. 12 Study Guide Part 2

Course: Anatomy And Physiology II (BIOL 1300)

8 Documents
Students shared 8 documents in this course

University: Fitchburg State University

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CHAPTER 12 PART 2: Nervous Tissue Physiology
(Sections 12.4 – 12.6)
Vocabulary:
Polarized
Resting membrane potential
Sodium-potassium pump
Stimulation
Depolarized
Repolarized
Graded (local) potential
Excitatory postsynaptic potential
(EPSP)
Inhibitory postsynaptic potential
(IPSP)
Action potential
Threshold
Hyperpolarization
Refractory period
Absolute refractory period
Relative refractory period
Unmyelinated fibers
Saltatory conduction
Continuous conduction
Presynaptic neuron
Postsynaptic neuron
Synaptic clef
Neurotransmitter
Ligand-gated channel
Voltage-gated channel
Required Core Objectives:
1. Describe resting membrane potential and what factors determine and maintain it.
Resting membrane potential is when the cell is at rest but has the potential to be excited and fire. It’s the electrical potential
difference across the plasma membrane when the cell is in a non-excited state. It exists because of unequal electrolyte
distribution between extracellular fluid (ECF) and intracellular fluid (ICF). There are more negatively charged particles on the
inside of the membrane (ICF) than the outside (ECF). Resting membrane potential results from 3 factors: 1) Ions diffuse
down their concentration gradient through the membrane, 2) the plasma membrane is selectively permeable and allows
some ions to pass easier than others, and 3) electrical attraction of cations (positively charged ions) and anions (negatively
charged ions) to each other.
Define:
a. electrical potential: The difference in the concentration of charged particles between one point and another. It’s a form
of potential energy that, under the right circumstances, can produce a current.
b. electrical current: A flow of charged particles from one point to another. Currents indicate the flow of positively or
negatively charged ions across the resistance of your cells’ membrane.
c. resting membrane potential: The charge difference between the plasma membrane.
Which ion has the greatest influence on membrane potential? Potassium.
Is there a higher concentration of K+ inside or outside the cell? Outside.
Is the cell membrane more permeable to K+ or Na+ ions? K+
Is there a higher concentration of Na+ ions inside or outside the cell? Inside.
This difference in ions is called Polarization.
2. Relate sodium potassium pump to resting membrane potential.
Explain how the Na+/K+ pump works: Sodium leaks out of the cell and potassium leaks into the cell. The sodium-potassium
pump continually compensates for this leakage by pumping 3 sodium ions out of the cell and 2 potassium ions into the cell.
How many Na+ and K+ ions are pushed through it? 3 Na+ ions move out and 2 K+ ions move in.
How much of the total energy of the nervous system is used to fuel it? 70%.
Where does this energy come from? ATP (Adenosine triphosphate).
3. Explain how stimuli can cause changes in the resting membrane potential.
When a neuron is stimulated, it creates an impulse in the form of an action potential, which causes sodium to enter the cell,
resulting in depolarization. At the peak of the action potential, potassium enters the cell, causing it to become

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