Animal Science 214 Exam 2

Nervous System

X

The nervous system is what form of communication in the body?

2nd form

Explain the subdivisions of the nervous system.

You main sections of the nervous system are the central nervous system (CNS) and the peripheral nervous system (PNS). The PNS then branches off into the sensory (afferent) division and motor (efferent) division. The Motor will also branch off into two sections, the somatic nervous system and the autonomic nervous system. Finally, you will see the autonomic division branch off into two final divisions of the nervous system, the sympathetic division and the parasympathetic division.

The central nervous system is located where?

Brain and spinal cord

What does the central nervous system do?

This is your integrative and control center. It is in charge of receiving signals and deciding what to do with them.

Where is the peripheral nervous system located?

Cranial and spinal nerves

What is the peripheral nervous system do?

This is the communication line between the central nervous system and the rest of the body.

Where is the sensory division of the nervous system located?

Somatic and visceral sensory nerve fibers

What does the sensory division do?

Conducts impulses from receptors to the CNS

Where is the motor division of the nervous system located?

Motor nerve fibers

What does the motor division do?

Conducts impulses from the CNS to effectors (muscles and glands)

What type of movement is the somatic nervous system?

Voluntary

What does the somatic nervous system do?

Conducts impulses from the CNS to skeletal muscles

What type of movement does the autonomic nervous system conduct?

Involuntary

What does the autonomic nervous system do?

Conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands

What does the sympathetic division do?

This is responsible for structure and function. It mobilizes body systems during activity.

What does the parasympathetic division do?

Conserves energy by promoting house-keeping functions during rest.

What are the two types of nerve cells?

Neurons (or nerve) and glial (neuroglial cells)

What do neuroglial cells do?

Supports the neuron

What cells are a part of the PNS?

Satellite and Schwann cells

What cells are a part of the CNS?

Microglia, ependymal, oligodendrocytes, and astrocyte cells

What are the most common type of glial cells?

Astrocytes which make up 20-40% of the cells

What do astrocytes do?

Provide nutrients, support, excess signaling, blood ring barrier, remodeling/repair; They also hide or cover up neurons that die off

What is the second most common type of glial cell?

Microglial (10-20%)

What is the function of microglial cells?

Provide more of an immune system/support; helps to remove dead and dying hormones

What is the function of the ependymal cells?

Provide cerebrospinal fluid

What is the function of the oligodendrocytes and Schwann cells?

Produces myelin which is important in helping with the signaling of the neuron across both the CNS and PNS

What is the function of the satellite cells?

Repair an regeneration of nerves

What is the function of the Soma?

This is the cell body. General biosynthetic (general protein, RNA protein) occurs and the receptive region

Know the parts of the neuron cell?

What is the function of the dendrites?

The receptive region of the neuron; receives the signals from other neurons; goes through the soma to the axon

What is the function of the axon?

This is the impulse-generating and conducting region; These are the extensions from the soma that will carry the electrochemical signal away from the soma.

What is the function of the axon hillock?

Connection between the soma and axon; this is the threshold that needs to be met

Myelin sheath Gap

Also known as the nodes of Ranvier; These are the gaps between the Schwann cells where we see exposed axon

Axon terminal

This is the end of the axon that functions in the signaling from one axon to the next; this is the secretory region

What are the three properties of a neuron?

Excitability, conductivity, and secretion

How does excitability work in a neuron?

The ability to be of an action potential to be stimulated/receive a signal

How does conductivity work in a neuron?

Conducts a signal down the entire axon

How does secretion work in a neuron?

The ability to signal to the next cell

How do neurons signal?

Action potentials (also known as spike potential)

Neurons are __________ systems.

All or none

Define all or none.

It is either going to get a response or it won't (no in-between)

Activation of neuron signaling can occur through what three types of channels?

Ligand-gated channels, mechanically-gated channels, and voltage-gated channels

How do ligand-gated channels work?

Protein molecules bind to receptors causing it to always be open; neurotransmitters binded to receptors/channels

Ligand-gated channels allow for what?

A flux of ions

How do mechanically-gated channels work?

There is a pressure on the cell membrane which causes the channel to open

Mechanically-gated channels allow for what?

Change in ions

Voltage-gated channels open due to a change in what?

Membrane potential

What factors drive membrane potential?

The negative protein in a cell

What should be the mV of a membrane potential?

-70 mV (negative at resting membrane potential)

What is membrane potential?

The voltage that is associated with the cell membrane

What is resting membrane potential?

The state of an axon when nothing is going on; also known as the baseline

Define volt meter.

How many mV are in a neuron

Define a threshold.

Magnitude or intensity that must be exceeded for a certain reaction, phenomenon, result, or condition to occur or be modified

Describe the parts of an action potential. Make sure to add what channels are open, and what ion is moving into or out of the neuron.

1) The first step of an action potential is the resting membrane potential.

2) Next, the AP goes to depolarization. In this stage, once the threshold is met activation of fast voltage-gated Na+ channels will occur (first to open). Membrane potential becomes less negative and drifts towards positive. Na+ flows into the neuron.

3) The third step is repolarization. In this stage, we see the inactivation of our fast voltage-gated Na+ channels. These channels have a ball and chain mechanism where the ball closes the channel to prevent Na+ from coming back in. Opening of slow voltage-gated K+ channels will cause K+ to flow out and membrane potential moves towards RMP as a result

4) The final step is hyperpolarization. Membrane potential is below baseline where Na+ is inside the axon and K+ is outside. This will occur due to slow-voltage gated channels K+ that stay open longer than needed. This results in fast voltage-gated sodium channels.

5) To get back to the threshold Na+ and K+ have to switch and do so through an ATPase pump

Define Absolute refractory period.

Time when the neuron cannot have a second action potential occur

Define Relative refractory period.

The neuron is starting to reset which slows down the signals. The neuron has to overcome hyperpolarization. This is also the period where the second AP can occur but it will take a longer time

Define myelination.

When the plasma membrane from other cells is wrapped around the axon to form an isolated barrier that allows for propagation of the signal to be more efficient.

What percent of myelination is fat and what percentage is protein?

20% protein and 80% fat

What types of cells can be found in CNS myelination?

Oligodendrocytes cells

What types of cells can be found in PNS myelination?

Schwann cells

Where does action potential start?

Axon hillock

Explain what myelination in the CNS and PNS looks like and what the difference is.

Myelination in the CNS can be seen with oligodendrocyte cells with a many-to-one ratio. These cells will wrap around multiple different neurons and spread out to multiple cells to wrap around them. There are three different neurons present and this is found exclusively in the CNS. Myelination in the PNS can be seen with Schwann cells with a 1-to-1 ratio. Only one cell will wrap around the neuron.

Signaling between two neurons occurs where?

Synapse

Define Synapse.

Functional connection between a neuron and another cell.

What are the two types of synapse?

Electrical synapse and chemical synapse

What is an electrical synapse?

Sends a change in electrical signals.

Where does electrical synapse occur?

The heart

Define chemical synapse.

The use of a chemical, or neurotransmitter, to go across an opening

Where does the pre-synaptic neuron take place?

Before the synaptic cleft

What does the pre-synaptic neuron do?

Sends the signal

Where does the post-synaptic neuron take place?

After the synaptic cleft

What is the function of the post-synaptic neuron?

Receives the signal

What are the three interactions that occur with the synaptic relationships?

Axodendrite synapse, axosomatic synapse, and axoaxonic synapse

Define Axodendrite synapse.

Where we have the axon terminals of the pre-synaptic neuron interact with dendrites of the post-synaptic neuron

Define Axosomatic synapse.

Where our axon terminals of pre-synaptic neurons interact with the soma or cell body of the post-synaptic neuron

Define Axoaxonic synapse.

Where our axon terminal of the pre-synaptic neuron interacts with the axon or axon terminal of the post-synaptic neuron

Describe the steps involved in synaptic signaling.

1) AP leads down the axon terminal; activation on voltage-gated calcium channels (open)

2) Ca2+ goes into the axon terminal

3) Ca2+ binds to the cytoskeleton

4) Neurotransmitters filled secretory vesicles move to plasma membranes

5) Exocytosis of neurotransmitters

6) Neurotransmitter binds to ligand-gated channels which opens up ion channels (gets the next cell

7) Termination of the signal

How does a neurotransmitter terminate a signal?

The neuron can uptake a signal, enzymes break down neurotransmitter, and diffusion

Define postsynaptic potentials.

A temporary change in the electric polarization of the membrane of a nerve cell (neuron)

In excitatory synapse there is an influx of what?

Na+ coming into the cell

Define excitatory synapse.

The action potential in a pre-synaptic neuron increases the probability of an AP occurring in post-synaptic cleft.

In an excitatory synapse the neurotransmitter binds to what?

The receptors located on the post-synaptic membrane of the lower neuron

Define inhibitory synapse.

Makes a post-synaptic neuron less likely to generate an AP

In inhibitory synapse neurotransmitters bind to what?

K+ receptors

We see an influx of what in the inhibitory synapse state?

K+ and Cl-

Will we see an AP in an inhibitory synapse?

No

What are the four parts of integration: summation?

1. Excitability and inhibitory

2. Excited pre-synaptic neurons (Temporal summation/over time)

3. Spatial summation

4. Red neuron

Do we get an AP in excitatory and inhibitory state?

No

Define the Temporal Summation phase?

Over time; add excitatory postsynaptic potentials together

Do we get an action potential in the temporal summation phase?

Yes

Do we get an AP in the spatial summation phase?

Above threshold causes an AP

Define spatial summation

Two PS neurons dire at the same time causes excitatory SP

Define a red neuron.

This is the inhibitory action potential, it is how to move that signal along

Muscle System

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What is the function of all muscle types?

To contract

What are the three types of muscles?

Smooth muscle, cardiac muscle, and skeletal muscle

Where is smooth muscle found?

Hollow organs

What type of contractions does smooth muscle conduct?

Involuntary (autonomic nervous system)

Is smooth muscle striated?

Non-striated