Lecture 5 (Nervous System II)

What are other names for the cell body of a neuron?

Soma, perikaryon

What part of a neuron receives information and interacts with other neurons?

Dendrites

What part of a neuron sends output signals?

Axon

What part of a neuron is where action potentials originate?

Axon hillock

What part of a neuron stores neurotransmitter vesicles and has mitochondria?

Pre-synaptic terminal

When a neuron is resting, the cell has a ________ charge outside and a _________ charge inside.

Positive; negative

How many gates does a sodium channel have? What are they?

Two; activation and inactivation gates

During resting state, what is the membrane potential of a neuron?

-90 mV

During resting state, which gate of the sodium channel is closed?

Activation gate

What must the membrane potential of a neuron reach for the activation gate of a sodium channel to open?

-70 mV

What (slower) process occurs when the activation gate of a sodium channel opens?

Inactivation gate closes

What channels open alongside the sodium channels when the membrane potential reaches -70 mV (but slower)?

Potassium channels

The opening of the gates to a sodium channel is _________-dependent.

Voltage

What three ions control the voltage of a neuron? Which one is most important?

Sodium, potassium, chloride

At rest, a neuron is ___________ (polarized/depolarized).

Polarized

When a strong stimulus reaches a neuron, __________ channels open quickly.

Sodium

What ion rushes into a neuron to cause depolarization?

Sodium

During depolarization, what ion rushes out of a neuron?

Potassium

How are neurons repolarized?

Potassium exits the cell

Describe the steps of an action potential.

1. Stimulus

2. Sodium channels open, sodium rushes into cell → depolarization

3. Potassium channels open (slow), potassium rushes out of cell

4. Sodium channels close

5. Potassium exits cell → repolarization

6. Potassium channels close

What is quicker, depolarization or repolarization?

Depolarization

What works against the depolarization of a neuron all the time?

Sodium-potassium pump

Some presynaptic terminals are _________, and others are __________.

Excitatory; inhibitory

The transmission of information between neurons is called a _________.

Synapse

Synaptic terminals contain ____________ and _____________.

Vesicles; mitochondria

What are the two types of synapses?

Chemical and electrical

What type of receptor on the post-synaptic terminal is a direct ion channel with a fast (short-term) effect?

Ionotropic receptor

Describe the action of an ionotropic receptor.

When neurotransmitters present, channels open quickly; when not present, channels close quickly

What type of receptor on the post-synaptic terminal activates second messengers and has a prolonged (long-term) effect?

Metabotropic receptor

Describe the actions of a metabotropic receptor.

• Prolonged opening of ion channels

• Activation of metabolic machinery

• Activation of enzymes

• Activation of gene transcription

Where are neurotransmitters produced?

Soma

How are neurotransmitters transported through the axon?

In vesicles

Where are neurotransmitter vesicles stored?

Presynaptic terminal

What two things can happen to a neurotransmitter when it is released into the synapse?

Metabolized or reabsorbed into presynaptic terminal

Why are some neurotransmitters metabolized in the synapse?

Used for generation of more neurotransmitters

Describe the pathway of acetylcholine synthesis, storage, release, and metabolism.

Acetyl CoA + choline (choline acetyl transferase) → acetylcholine (acetylcholine esterase) → acetate + choline

What is the resting potential of a spinal motor neuron?

-65 mV

When the voltage of a neuron becomes less negative, the neuron becomes ________ excitable.

More

When the voltage of a neuron becomes more negative, the neuron becomes ________ excitable.

less

A stimulus can make the inside of a neuron more __________.

Negative OR positive

The firing of ________ (one/many) neurons is required to cause an action potential.

Many

Describe what happens when a neuron is excited.

• Cell becomes more positive

• Cation channels allow sodium to pass

• Depressed conduction of Cl- to inside of neuron and K+ to outside

Describe what happens when a neuron is inhibited.

• Cell becomes more negative

• Anion channels allow chloride to pass

• Increased conduction of K+ to outside

What is an EPSP?

Excitatory postsynaptic potential

Multiple neurons need to fire to increase a neuron’s voltage in a process called _____________.

Summation

What is an IPSP?

Inhibitory postsynaptic terminal

What happens during an IPSP?

Hyperpolarization; Cl- and K+ channels open

An excitatory synapse makes the membrane permeable to Na+ for only 1-2 milliseconds because:

Sodium potassium pump restores ionic balance