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What is an organ system?

a group of organs each with specific structures and functions that coordinate and integrate with one another

What are examples of an organ system?

Nervous, circulatory, respiratory, digestive, excretory, endocrine, and reproductive

What makes up the nervous system?

brain, spinal cord, nerves, and associated ganglia

Ganglia are not as ____ as _____, but they do have a specific _____ and ____.

obvious, organs, structure, function

What makes up the circulatory system?

heart, blood vessels, lymph nodes, lymph vessels

What is the general function of the nervous system?

short term coordination and integration of body functions

What is the nervous system controlled by?

electrochemical communication (nerve impulses or action potentials)

Without impulses and action potentials, what would happen?

There would be no coordination of body functions

What are the properties of the nervous system?

1. Irritability or excitability
2. Conductivity

What is irritability or excitability?

the ability to react to stimuli followed by the generation of nerve impulses

What is conductivity?

the ability to transmit nerve impulses/APs from one area of the body to another

(if the NS could not do this, there would be no function for APs or nerve impulses)

What is the functional sequence of events for short term coordination?

1. reception of stimuli
2. conversion of stimuli
3. transmission of APs
4. Production of a response or an action

Reception of stimuli is received from where?

from external or internal environments

Conversion of stimuli -->

into nerve impulses/APs

Transmission of APs -->

over correct pathways

What is an example of production of a response or an action for short term coordination?

Muscle contraction --> gland secretion

What are the two divisions of the nervous system?

central nervous system and peripheral nervous system (CNS, PNS)

What does the CNS consist of?

the brain and spinal cord

What does the PNS consist of?

1. Nerves and ganglia of somatic NS
2. Nerves and ganglia of autonomic NS

What are the nerves and ganglia of the somatic NS associated with?

skeletal muscles

What are ganglia?

a collection of nerve cell bodies

What are the two divisions of the autonomic nervous system?

1. Sympathetic NS
2. Parasympathetic NS

What are the 3 histological elements of the nervous system?

Neurons (nerve cells), neurological/glial cells, and white fibrous collagenous connective tissue

What is another term for neuron?

Nerve cells

What is another term for nerve cells?


What are neurons?

the basic unit of cellular function

What is the function of neurons?

they generate and conduct nerve impulses

How many neurons are in the brain?

over 100 billion

How many neurons are in the nervous system?

over 1 trillion

Neuroglial/glial cells provide what?

A variety of functions

How many glial cells are in the nervous system compared to neurons?

10-50x more

What is another term for schwann cells?


What is another term for neurolemmocytes?

schwann cells

Where are schwann cells found?

only in the PNS, NOT in the brain or spinal cord!

What are schwann cells described as?

being insulator cells

What are found associated with portions of neurons?

schwann cells

Schwann cells are found associated with what?

portions of neurons (axons and dendrites)

Where is white fibrous collagenous connective tissue found?

mainly in peripheral nerves, little is found directly in the brain

What is the dura mater?

a membrane that surrounds the brain

What is the dura mater made of?

white collagenous connective tissue

What are the 2 component parts of a neuron?

the cell body and the processes of fibers

What is another name for the cell body?


Where is the nucleus found?

in the cell body

Where are the processes of fibers?

they extend off the cell body

What are the two processes of fibers called?

dendrite and axon

Describe a dendrite

there are one or more (200) and usually short in length

Describe an axon

there is ONLY one and most often longer in length than dendrites

How long is the longest axon?

2-3 feet

Where is the longest axon found?

in the posterior thigh region

What are the three morphological classifications of neurons?

1. pseudo-unipolar
2. bipolar
3. multipolar

What is the function of pseudo-unipolar neuron axons?

they carry APs to the cell body then continue to carry the AP away from the cell body

Describe a pseudo-unipolar neuron fiber

the fiber is divided in two but in both cases, it is an axon, and the term dendrite is not used in classification

What is typical of sensory neurons?

they have a fiber that is divided in two but in both cases, they are axons

Sensory neurons have cell bodies located in what?

cranial and spinal ganglia

Describe a bipolar neuron

it has one dendrite and one axon

What are bipolar neurons associated with?

special senses

Where are bipolar neurons found?

1. the retina of the eye
2. the olfactory epithelium of the nose (detect odors)
3. the taste buds of the tongue

Describe a multipolar neuron

has many dendrite but ONLY ONE axon

What is the most common neuron in the nervous system?

the multipolar neuron

Which neuron do we focus on in terms of structure and function?

the multipolar neuron

The multipolar neuron is the most focused on in terms of what?

structure and function

What are the 3 functional classification of neurons?

1. motor
2. sensory
3. interneurons

What is another term for motor neurons?

efferent neurons

What is another term for sensory neurons?

afferent neurons

What is another term for interneurons?

association neurons or internuncial (older term) neurons

Where do motor neurons transmit APs?

from the brain/spinal cord to muscles or glands

What kind of neuron is a motor neuron?


Where do sensory neurons transmit APs?

from peripheral receptors to spinal cord or brain

What kind of neuron is a sensory neuron?

mostly pseudo unipolar

Where do interneurons transmit APs?

from sensory neurons to other interneurons or to motor neurons

What kind of neuron is an interneuron?


Where are interneurons confined to?

a region of the CNS called the gray matter

Where are interneurons found?

ONLY in gray matter

What is a dendrite?

short fibers which extend off of the cell body/perikaryon

What is the function of a dendrite?

they transmit APs TO the cell body

Some dendrite have tips that are modified into what?

sensory receptors

What does the cell body/perikaryon contain?

usual cell organelles suspended in cytosol

What is the nucleus?

a cell organelle that contains the nucleolus and chromatin

Where is the nucleolus located?

in the nucleus

Where are chromatin located?

in the nucleus

Where are cell organelles found?

in the cell body suspended in cytosol

What is mitochondria?

a cell organelle found also in synaptic knobs of the axon

What is the golgi complex?

a cell organelle that produces vesicles containing neurotransmitters

Where are neurotransmitters made?

in the cell body

Where are neurotransmitters incorporated into vesicles?

the golgi apparatus

What happens to neurotransmitters in the golgi apparatus?

they are incorporated into vesicles

What is nissl substance?

concentrated areas of rough ER and RNA

The areas where you find the nissl substance, are where you will also find _____.

protein synthesis

The cytoskeletal components maintain what?

1. the shape of neurons
2. the cell shape

Cytoskeletal components contain what structures?

intermediate filaments
microtubules (neurotubules)

What is another name for microtubules?


Where are cytoskeletal components found?

in all parts of the neuron, cell bodies, dendrites and axons

What is an axon?

a single long fiber that extends AWAY from the cell body

Can axons be branched?


What is the branch of an axon called?

an axon collateral

Where do axons carry APs?

from the cell body AWAY to other cells

Axons arise from where?

the cell body at a region called the axon hillock

Where do APs originate?

the axon hillock

What is the axon hillock?

a funnel shaped structure that leads into cell fibers

Axons or its _____ end in ____ ____.

collaterals, axon terminals

Are axon terminals highly branched?


Where do axon terminals end?

in structures called synaptic knobs

What is another term for synaptic knob?

boutons or end feet

What is another term for bouton?

Synaptic knob, end feet

What is another name for end feet?

synaptic knob, bouton

What does the synaptic knob innervate?

other neurons, muscle cells, or gland cells

What is a neurotubule's function?

they assist in the transport of neurotransmitters vesicles down the axon

Neurotubules allow ___ ___ to move from the ___ ___ to ____ ___.

synaptic vesicles, cell body, synaptic knob

Where do axons send APs?

away from the cell body

What are branches of axons called?

axon terminals

Where can one axon send one signal?

To several different cells

What are the two types of axons and dendrites in the PNS?

myelinated and unmyelinated

What do schwann cells do?

1. they line up on one axon
2. each one individually wraps around the axon
3. they produce a myelin sheath

What is a myelin sheath composed of?

layers of schwann cell plasma membranes rich in the lipid myelin

What is myelin?

a lipid

Schwann cell plasma membranes are rich in what?


What type of cell is a schwann cell?

a glial cell in the PNS

What is the neurilemma?

a layer of schwann cell cytoplsam outside of the myelin sheath

Schwann cells exert a very important ____ on ____ that have them.

function, axons

Where do schwann cells NOT cover?

the axon hillock or axon terminals

What are the ends of axons referred to?

axon terminals

What is the nodes of ranvier?

spaces between schwann cells where an axon is NOT covered

In the nodes of ranvier, the plasma membrane of the axon is not...

exposed to the extracellular fluid

Where is extracellular fluid located?

outside of the axon

Unmyelinated axons have several what?

fibers (axons or dendrites)

What fiber is most commonly found in unmyelinated axons?


Where are axons in unmyelinated embedded?

in the cytoplasm of a series of schwann cells

Multiple fibers in unmyelinated axons prevent what?

schwann cells from coiling around the axons

Can the multiple fibers of an unmyelinated axon form a myelin sheath?


In unmyelinated axons, axon _____ are exposed to ____ all along the length of ____.

membranes, ECF, axons

Peripheral components include what?

1. epineurium
2. perineurium and fascicles
3. endoneurium

What is the epineurium?

outer covering of peripheral nerve

What is the epineurium made of?

white fibrous connective tissue

The epineurium layer covers what?

the outer surface of the peripheral nerve

What is the perineurium?

a layer of white fibrous connective tissue that extends from the epineurium into a nerve and makes compartments called fascicles

What is the perineurium made of?

white fibrous connective tissue

Where does the perineurium extend from?

the epineurium into a nerve

The perineurium makes compartments called?


What are fascicles?

sub-compartments of a nerve

The perineurium serves as the...

outer sheath of a fascicle

The fascicle is a group of...

axons and/or dendrites

The fibers of the axons and/or dendrites of a fascicle...

may be myelinated or unmyelinated

What is the endoneurium?

an areolar tissue that covers the surface of each fiber in a fascicle

What is a function of connective tissue components?

serve as a pathway for blood vessels to penetrate a nerve

What is the pathway for blood vessels to penetrate a nerve?

epineurium-->perineurium--> endoneurium

What is the function of the epineurium?

it holds fascicles together as a nerve

The function of the perineurium?

holds fibers together as a fascicle

The function of the endoneurium?

it interconnects fibers

Where are neurologlial cells found?

only in the CNS and PNS

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