Study guide Chp 11

Parts Of CNS

The central nervous system

brain and spinal cord

processes information and coordinating responses throughout the body.

PNS

is the peripheral nervous system

all nerves outside the central nervous system

connecting the brain and spinal cord to the rest of the body

Parts of PNS

Cranial Nerves

Spinal Nerves

Ganglia

Peripheral Nerves

What are the 2 cell types that produce Mylein Sheaths?

Oligodendrocytes and Schwann cells.

Oligodendrocytes

found in CNS

Insulate Axons

Increase speed of electrical signal or impulse

Random spaced Nodes Ranvier

Schwann Cells

Insulate one segment of axon

found in PNS

Increase speed of nerve impulse or electrical signal

Even spaced Nodes Ranvier

What does not have Neurilemma?

Oligodendrocytes

What does have Neurilemma?

Schwann cells

What cells are Amitotic?

Nerve cells (neuron), do not divide

Neurons are composed of

Soma, Axon, Dendrites

What is released at the axon terminal or ending?

Neurotransmitters

Bundles of Axons in CNS are called

Tracts

Bundles of Axons in PNS are called

Nerves

Dendrites produce

Graded Potential

Axons Produce

Action Potentials

Clusters in CNS are called

Nuclei

Clusters in PNS are called

Ganglia

Neuron region that receives signals

Dendrites

Neuron region that secretes neurotransmitters and send signals (transmit action potential)

Axon

Myelin Sheath

A protective covering around axons that facilitates the rapid transmission of electrical impulses along the nerve cell.

Schwann cells surround nerve fibers but coiling does not take place

Unmyelinated Axons

Myelin Sheath in CNS

Formed by Oligodendrocytes

widely spaced

no Neurilemma

Multipolar

Neuron structure- Many dendrites, One Axon together, but many

Bipolar

One Dendrite, One Axon and cell body between

Often found in Sensory Neurons

Unipolar

Found in PNS

Dendrite, axon straight together

What Neurotransmitter Stimulates Skeletal Muscle

Acetylcholine (ACh)

What are Clusters of Neuron Cell Bodies located in PNS called

Ganglia

CNS cell bodies are called

Nuclei

PNS axons are called

Nerves

CNS axons are called

Tracts

What determines Stimulus Strength?

Frequency of action potentials and Number of Neurons activated (recruitment)

What Ions are involved in setting up resting membrane potential?

Potassium (K), Sodium (Na), Chloride (Cl-)

What is much higher Intracellular?

Potassium (K) and proteins

What is much higher extracellular (outside) cell?

Sodium (Na) and Chloride (Cl-)

Ion Channels

Proteins that facilitate the movement of ions across the cell membrane

What causes Resting Membrane Potential?

More Potassium moving out cell than sodium moving in.

More leakage gates for potassium

More Positive outside and Neg charge inside cell

What Maintains Resting Membrane Potential?

Sodium Potassium Pump

Lose more positive charges than bringing in sodium, contributing to a negative charge inside the cell. Maintaining Positive on outside

Resting Membrane Potentail

-70mv

the electrical potential difference across the membrane of a resting cell, typically around -70 millivolts.

Ions can not pass through the plasma membrane without ?

Ion Channels

Leakage Channel

Always open

Leak Gate for Potassium (K)

More abundant

Potentail means

Difference between outside and inside charge of a cell's membrane, determining its electrical state.

How do Ions move through Channel Gates?

The Gate opens in response to voltage, Chemical Transmitter, or Pressure.

Ions move from High to Low concentration (Chemical Gradient)

Or toward Opposite Charge (Electrical Gradient)

Threshold Potential

-55mv

the level of depolarization needed to trigger an action potential in a neuron.

Action Potentials vary in strength

Fasle. They are always max strength

Action Potentials and Graded Potentials involve Depolarization, Repolarization, Hyperpolarization

True

Which locations are Graded Potentials found?

Dendrites and Cell Bodies

Graded Potential Characteristics

Short lived

Decrease strength with distance

Magnitude varies with strength of stimulus

Stong Graded potentials can initiate Action Potentials

Involve Chemical Gates for Depolaization

Characteristics of Action Potentials

Long Lived

Do not decrease in strength with distance

Always max strength

Involve Voltage Gates for Depolarization

Occur at Axons

Action Potentials

Occur at Dendrites and Cell Bodies

Graded Potentials

Steps for Any Kind of Membrane Potential?

Depolarization, Repolarization, Hyperpolarization

What Creates the Resting Membrane Potential?

Sodium Potassium Leak Gates

What gates are open and closed during Depolarization?

Sodium (Na) are open

Potassium (K) closed

Further away from threshold for Action Potential

Hyperpolarization

What opens Voltage Gates for Sodium?

Reaching Threshold

giving an action potential

When do sodium gates close?

Repolarization

Voltage sensitive K gates open when

Sodium channels have closed

the membrane potential starts to become less positive.

Role of Sodium Potassium Pump

Repolarization

Restores resting electrical condition of neuron

Ionic Redistribution - sodium out, potassium in

Hyperpolarization

Potassium gates remain open, causing excessive K to leave the cell, making the inside of the neuron more negative than the resting potential.

Phases of Action Potential

Resting, Depolarization, Repolarization, Hyperpolarization, Resting

1. Na gates open at rest

2. Depolarization

3. Na+ gates close

4. Action Potential

5. Potassium gates open

6. Repolarization

7. Hyperpolarization occurs as K+ gates remain open.

What happens if threshold isn’t met?

Will not have an Action Potential, only Graded Potential

What determines stimulus strength?

Frequency in impulse transmission or signals

When is Absolute Refractory Period?

During Depolarization and Repolarization

Characteristics of Absolute Refractory Period

Prevents neuron from generating another Action Potential

The Relative Refractory Period occurs during Hyperpolarization

True

When is Threshold Elevated?

During Relative Refractory Period - AP is harder to reach and occurs during Hyperpolarization