Week 9 Chapter 12 Part 2 HW

Classify the given items with the appropriate group. Spatial Summation Temporal Summation - Multiple presynaptic neurons releasing neurotransmitter - A single presynaptic neuron releases neurotransmitter - The same location of neuron is exposed to neurotransmitter in a very short period of time - Can generate an EPSP, IPSP, or both - Various locations of receptive segment are exposed to neurotransmitter

Spatial Summation - Various locations of receptive segment are exposed to neurotransmitter - Multiple presynaptic neurons releasing neurotransmitter - Can generate an EPSP, IPSP, or both Temporal Summation - A single presynaptic neuron releases neurotransmitter - The same location of neuron is exposed to neurotransmitter in a very short period of time

Graded potentials are added together at the axon hillock in a process known as _________.

Summation

Fill in the blanks with the terms provided. Between each presynaptic and postsynaptic neuron is a __________ that is the fluid-filled space between them. Each presynaptic neuron releases __________ that binds with receptors in the __________ segment of a postsynaptic neuron. The __________ channels of the receptive segment open when these molecules bind. Specific ions then cross the membrane, initiating a __________ potential in the postsynaptic neuron. This local potential is a small voltage change in the __________ potential. Graded potentials that occur in postsynaptic neurons are specifically called __________ potentials.

Synaptic Cleft Neurotransmitter Receptive Gated Graded Resting Membrane Postsynaptic

Which part of a neuron contains calcium pumps and channels?

Synaptic bulbs

A typical synapse in the CNS consists of a presynaptic neuron and a postsynaptic neuron, separated by a narrow space called the

Synaptic cleft.

Correctly identify each of these definitions or examples as either depolarization or hyperpolarization of the plasma membrane. 1. Decrease in the membrane potential Depolarization 2. Inside of the cell becomes more positive Depolarization 3. An increase in the extracellular concentration of potassium Hyperpolarization 4. Increase in the membrane potential Hyperpolarization 5. Inside of the cell becomes more negative Hyperpolarization 6. A decrease in the extracellular concentration of potassium Depolarization 7. An increase in the number of sodium leak channels Depolarization

1. Depolarization 2. Depolarization 3. Hyperpolarization 4. Hyperpolarization 5. Hyperpolarization 6. Depolarization 7. Depolarization

On a particular patch of axolemma, the electrical events that occur as an action potential travels by can be ordered as Depolarization Hyperpolarization Repolarization

1. Depolarization 2. Repolarization 3. Hyperpolarization

Answer these True/False questions regarding graded potentials. 1. Graded potentials can result from voltage across the plasma membrane. 2. Graded potentials can result from mechanical stimulation or temperature changes. 3. The potential change can vary from small to large depending on the stimulus strength or summation. 4. The effects produced by one graded potential can be added onto the effects of another graded potential. 5. Increased permeability of the membrane to sodium results in depolarization. 6. A depolarizing graded potential can cause an action potential.

1. True 2. Ture 3. True 4.True 5. True 6. True

Fill in the blanks with the terms provided. Not all terms will be used. A synapse is the specific location where __________ is functionally connected to either another neuron or __________. There are two types of synapses in the human body: chemical synapses and electrical synapses. Most synapses within the nervous system are __________ synapses.

A Neuron An Effector Chemical

When a neurotransmitter binds a protein channel, it opens and lets sodium diffuse down its concentration gradient. This is an example of a

Chemically gated sodium channel.

Classify the given items with the appropriate group. Excitatory Neurotransmitter Actions Inhibitory Neurotransmitter Actions - Binds to a chemically gated chloride channel - Binds to a chemically gated sodium channel - Potassium moves down its concentration gradient out of the neuron - Chloride moves down its concentration gradient into the neuron - Sodium moves down concentration gradient into the neuron - The inside of the neuron becomes more positive - Binds to a chemically gated potassium channel

Excitatory Neurotransmitter Actions - Binds to a chemically gated sodium channel - Sodium moves down concentration gradient into the neuron - The inside of the neuron becomes more positive Inhibitory Neurotransmitter Actions - Binds to a chemically gated potassium channel - Binds to a chemically gated chloride channel - Potassium moves down its concentration gradient out of the neuron - Chloride moves down its concentration gradient into the neuron

On a graph of an action potential, the small depolarizations that lead to threshold are from

Excitatory postsynaptic potentials (EPSPs).

True or False: At resting membrane potential, voltage-gated potassium ion channels are open.

False

Fill in the blanks with the terms provided. Not all terms will be used. EPSP and IPSP __________ potentials are local currents of ions that move along the plasma membrane toward the initial segment area of the __________. Graded __________ potentials are added together in the initial segment; this process is called __________. The initial segment, by adding postsynaptic potentials, determines if a(n) __________ potential is reached. This potential is __________ mV. This is a change of __________ mV from the RMP. When this threshold is reached, it initiates the opening of __________ channels and the generation of a(n) __________ potential that will travel along the axon.

Graded Axon Hillock Postsynaptic Summation Threshold Membrane -55 +15 Voltage-gated Action

Depolarization is initiated by a stimulus that makes the membrane potential

More positive.

Depolarization of a cell membrane occurs because

More sodium ions diffuse into the cell than potassium ions diffuse out of it.

When sodium enters the neuron via chemically gated sodium channels, the membrane will depolarize. Therefore, the membrane potential will become more

Positive.

Fill in the blanks with the terms provided. Not all terms will be used. The relative difference in charge across a plasma membrane is the __________ in an inactive excitable cell. A __________ is used to measure the voltage difference across the plasma membrane. This is done by placing one microelectrode into the __________ and the other microelectrode outside the neuron into the __________. The RMP has a value that is typically __________ millivolts. More positive ions reside __________ a neuron than __________ a neuron when it is at rest.

RESTING MEMBRANE POTENTIAL VOLTMETER NEURON INTERSITITIAL FLUID -70 OUTSIDE INSIDE

Place the events in the correct sequence. Not all items will be used. - Neurotransmitter attaches to receptors on a muscle, neuron, or gland cell - Synaptic vesicles merge with synaptic knob plasma membrane - Neurotransmitter is released by exocytosis - Neurotransmitter crosses synaptic cleft - Action potential reaches synaptic knob - Voltage-gated calcium channels open - Calcium enters the synaptic knob

- Action potential reaches synaptic knob - Voltage-gated calcium channels open - Calcium enters the synaptic knob - Synaptic vesicles merge with synaptic knob plasma membrane - Neurotransmitter is released by exocytosis - Neurotransmitter crosses synaptic cleft - Neurotransmitter attaches to receptors on a muscle, neuron, or gland cell

Under no circumstances can another action potential be generated during the ______ refractory period.

Absolute

The _______ is a period when a membrane cannot respond to another stimulus (no matter how strong).

Absolute refractory period

A recently depolarized area of a cell membrane cannot generate an action potential because of the

Absolute refractory period.

Fill in the blanks with the terms provided. Pumps move substances __________ a concentration gradient, a process that requires energy. Channels instead provide the means to move a substance __________ a concentration gradient. Neurons contain the following major types of channels: • Channels that are always open, allowing continuous diffusion of a specific ion from a region of __________ concentration to a region of __________ concentration are leak channels. • Channels that are normally closed that open in response to the binding of a __________ are chemically gated channels. When open, they allow a specific ion to __________ across the plasma membrane. • Channels that are normally closed, but open in response to changes in __________ across the plasma membrane are voltage-gated channels. When open, they allow a specific ion to diffuse across the membrane.

Against With High Low Neurotransmitter Diffuse Electrical Charge

When chloride enters the neuron via chemically gated chloride channels, the membrane potential will become more negative than the resting membrane potential. This is called _____________.

Hyperpolarization

If neurotransmitter from Neuron A causes Neuron B to hyperpolarize, this is an example of an

Inhibitory postsynaptic potential.

Complete each statement by using the appropriate word or phrase from the list. Not all terms will be used. Resting membrane potential is created as a result of a greater net flow of positive charges from the __________. Though potassium and sodium both leak through the membrane at rest, there is a greater diffusional flow of __________ at rest. The diffusional movement of sodium and potassium across the membrane is driven at all times by the __________. The electrical and chemical gradients for __________ are both high during resting membrane potential, which results in a very high electrochemical gradient toward the inside of the cell. In order to maintain the electrochemical gradients for sodium and potassium, AT Pase pumps move these ions __________ their respective gradients.

Intracellular Fluid to the Extracellular Fluid Potassium Electrochemical Gradient Sodium Against

The negative value of the resting membrane potential means that

There are more negatively charged particles on the inside of the membrane than on the outside.

True or False: Inhibitory postsynaptic potentials (IPSPs) may be caused by the opening of either chemically gated potassium channels or chemically gated chloride channels.

True

If extracellular calcium was absent, which would likely be true?

Vesicles containing neurotransmitter would not merge with the plasma membrane.

Place a single word into each sentence to make it correct. Some terms may be used more than once, some not at all. Action potentials arriving at the presynaptic terminal cause __________ -gated calcium channels to open. Calcium ions diffuse into the cell and cause synaptic vesicles to release __________. Neurotransmitters diffuse from the __________ terminal across the synaptic cleft. Neurotransmitters combine with their receptor sites and cause __________ -gated ion channels to open. The diffusion of __________ into the cell or out of the cell causes a change in membrane potential.

Voltage Neurotransmitters Presynaptic Ligand Ions