Nervous System Flashcards by Jocelyn Gill

Functions of the Nervous System

Coordinate the actions of your body
Ensure effective behaviour
Maintain homeostasis in the internal environment

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Homeostasis

Stability in the body

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What send electrochemical messages throughout the body

The brain and hormones

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What are the two parts of the nervous system

The Central Nervous System (CNS)
The Peripheral Nervous System (PNS)

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What makes up the CNS

The brain and spinal cord

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What makes up the PNS

The rest of the body

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What are the two types of cells in the nervous system

Neurons and Neuroglial Cells

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Neurons

Transmit impulses

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Neuroglial Cells

Support neurons

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Dendrites

Receive signals

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Cell body

Contains the nucleus

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Axon

Conducts nerve impulses away

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Sensory neurons

Take information from sensory receptors to the CNS

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Interneurons

Occur within the CNS and integrate input (nonmyelinated)

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Motor Neurons

Informations from CNS to muscles or glands

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Nodes of Ranvier

Unmyelinated sections of a myelinated neuron, impulses “jump” from node to node

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Neurilemma

A thin layer encompassing neurons in the PNS, promoting regeneration

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Schwann Cells

Responsible for the myelin synthesis, type of glial cells (supporting and nourishing cell found in the nervous system)

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Axon Bulb

Either at a synaptic bulb or end plate to muscle, contains neurotransmitter

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Myelination

Covers long axons with a myelin sheath

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What does a sheath contains

Lipid myelin

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What does lipid do to the appearance of the myelin sheath

It gives nerve fibers their white appearance

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Mulitple Sclerosis

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Disease of the myelin sheath

What are nerves made up of

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Many neurons

What is white matter

Mylenated neurons

Whats the difference between white and gray matter

White matter can regenerate, gray matter won't regenerate

Reflex Arc

Pathways that use fewer neurons and it allows you to react rapidly when there is danger

What is the order of a reflex arc

1. Sensory Receptor 2. Sensory Neurons 3. Interneurons 4. Motor Neurons 5. Effector

Nerve Impulses

Convey Information

Oscilloscope

Nature of a nerve impulse has been studied by using excised axons and voltmeter

Thershold Potential

Neurons either fully activate and give a certain level of response, or it doesn't activate at all

How is the brain informed of the intensity by

1. Frequency of firing is increased 2. The number of neurons that respond to that level of stimulus can increase

Resting Potential

When no nerve impulse is being conducted

What is the charge inside the axon when it is at resting potential

-70 mV

What is being pumped in the cell and out of the cell during resting potential

Potassium is being pumped into the cell. Sodium is being pumped out of the cell

Membrane depolarization

Also known as the action potential. When the nerve cell is excited and the polarity changes

What happens to the potassium and sodium ions in the cell during depolarization

The sodium channels open and the sodium rushes in while the potassium gates close. There then becomes a greater concentration of sodium ions in the axon.

What does the charge of the axon become during membrane depolarization

40mV

Membrane Repolarization

The charge changes again, the axon membrane goes back to polarized but the sodium is inside the axon membrane and potassium is on the outside

What does the Na/K Pump restore

The ion concentrations inside and outside the cell

Refractory Period

Lasts 1-10 ms, it gives time for the neuron to recover. The pump requires ATP in order to work

What is the purpose of the refractory period

To make sure that the impulse travels forward

Synapse

The junction between neurons or neurons and effectors

When does a transmission of a nerve impulse take place

When a neurotransmitter molecule stored in the synaptic vesicles in the axon bulb is released to the synaptic cleft between the axon and the receiving neuron

What happens when a nerve impulse reaches an axon bulb

Calcium channels open and Calcium flows into the bulb

What does the rise in calcium cause

Synaptic vesicles to move and merge with the presynaptic membrane

What do the synaptic vesicles merging with the presynaptic membrane cause

Releasing of the neurotransmitter molecules into the synapse

What does the binding of the neurotransmitter to the receptors in the postsynaptic membrane cause

Inhibition and Excitation

Inhibition

Has a hyperpolarizing effect on the postsynaptic membrane

Excitatory

Has a depolarizing effect on the postsynaptic membrane

Summation

Summing up of excitatory and inhibitory signals

Two well known neurotransmitters

Acetylcholine and Norepinephrine

What enzyme breaks down acetylcholine

Acetylcholinesterase

How are neurotransmitter molecules removed from the cleft

Enzymatic breakdown or reabsorption

Why is synaptic transmission much slower than axonal transmission

Neurotransmitter move only by diffusion

Nervous System Flashcards

(55 cards)