Step 1 Anatomy Kaplan Chapter 2

Front 1

What is the nervous system?

Back 1

A vast communication network

Front 2

How is the nervous system divided anatomically?

Back 2

Into two overlapping systems: the central nervous system and the peripheral nervous system

Front 3

What makes up the central nervous system?

Back 3

Brain

Brainstem

Spinal cord

Front 4

What makes up the peripheral nervous system?

Back 4

Nerves and nerve roots

Ganglia

Nerve endings, receptors

Front 5

What are the two classes of cells present in the nervous system?

Back 5

Neurons

Neuroglia

Front 6

What are neurons?

Back 6

They are excitable cells that receive and integrate stimuli, conduct electrical impulses along its processes and pass on the "information" through specialized chemical junctions called synapses

Front 7

What are some of the special characteristics of neurons?

Back 7

They are highly differentiated

They are NOT able to replicate

They carry information in one direction, thru chains of neurons linked together by synapses

Front 8

What is neuroglia and what is its function?

Back 8

Nerve glue. They are glue cells that support neurons, and serve as the connective tissue cells of the nervous system.

They play an important role on the normal functioning of the nervous system.

They protect, surround, myelinate, and modulate the environment allowing neurons to function efficiently.

The also provide the metabolic support to neurons.

Most glia can divide

Front 9

Which are the glial cells of the CNS?

Back 9

Oligodendrocytes

Astrocytes

Ependymal cells

Microglia

Front 10

Which are the glial cells of the PNS?

Back 10

Schwann cells: surround all axons, may form myelin

Satellite cells: surround cell bodies in the ganglia

Front 11

What are the different parts of the neuron?

Back 11

Cell body

Dendrites

Axon

Front 12

What is the cell body of a neuron?

Back 12

The nucleus + the cytoplasm

Front 13

What is the function of the cell body of a neuron?

Back 13

Contains the genetic material in the nucleus

Trophic (nutrition) center of the cell. Contains all the organelles for maintaining the cell

Produces proteins for the entire cell

Membrane receives and integrates stimuli

Front 14

What are the components of the cell body of a neuron?

Back 14

Nucleus

Cytoplasm

Front 15

Describe the nucleus in the cell body of a neuron

Back 15

Large, euchromatic, vesicular nucleus with a single prominent and well developed nucleoulus

Front 16

Describe the cytoplasm in the cell body of the neuron

Back 16

Cytoplasm contains:

1. Microtubules, microfilaments, neurofilaments (intermediate), mitochondria (no glycogen), synaptic vessicles

2. Organelles to make new proteins: golgi apparatus, ribosomes, and RER

Front 17

What are Nissl bodies?

Back 17

RER and ribosomes present in the cell body of a neuron appear in LM as basophilic clumps called Nissl bodies

This happens because the RER stains intensely with basic dyes

Front 18

Why does the cell body have an abundant RER?

Back 18

Because there is a high rate of protein synthesis taking place in the cell body

Front 19

What are the functions of microtubules and microfilaments in the cell body?

Back 19

Contribute to the neuronal cytoskeleton

Play important roles in axonal transport

Front 20

What pigment granules can be seen in the cytoplasm of a neuron?

Back 20

Lipofuscin ("wear and tear" pigment)

Melanin (found in some catecholamine-containing neurons)

Front 21

What are dendrites?

Back 21

Neuronal processes that receive information and transmit it to the cell body.

Front 22

What is the purpose of the extensive branching of dendrites?

Back 22

To increase the receptive area of the neuron

Front 23

What are the functions of dendrites?

Back 23

Membrane receives and integrates stimuli

Increases the surface area for receiving stimuli

Front 24

What are the components of dendrites?

Back 24

They are basically extensions of the cell body, so they contain the same organelles

Front 25

What are axons?

Back 25

Thin, long cylindrical processes of constant diameter typically arising from the cell body (or from a proximal dendrite) through a short pyramidal-shaped region called the axon hillock

Front 26

What are the functions of axons?

Back 26

1. Conduct nerve impulses (action potentials) towards the axon terminal

2. Communicates with the next cell via a synapse

3. When the impulse arrives at the terminal, synaptic vesicles containing neurotransmitters are released into the synaptic space

Front 27

What is the cell membrane of the axon called?

Back 27

Axolemma

Front 28

What is the cytoplasm of the axon called?

Back 28

Axoplasm

Front 29

What is the axon hillock?

Back 29

Elevated region of the cell body at the beginning of the axon that stops protein making organelles from entering the axon

Front 30

What is a collection of cell bodies + axons called in the CNS?

Back 30

Gray matter (nuclei)

Front 31

What is a collection of cell bodies + axons called in the PNS?

Back 31

Ganglia

Front 32

What is a collection of axons (no cell bodies) called in the CNS?

Back 32

White matter

Front 33

What is a collection of axons called in the PNS?

Back 33

Nerves

Front 34

What are the contents of axons?

Back 34

Cytoplasm contain mitochondria, synaptic vesicles, parallel arrays of microtubules, microfilaments, and neurofilaments.

Axons do NOT contain ribosomes, RER, and golgi

Front 35

What is axoplasmic transport?

Back 35

Continuos flow of cytoplasm and organelles up and down the axon guided by microtubules

Front 36

How does axoplasmic transport take place?

Back 36

Axons contain abundant microtubules and neurofilaments.

Axonal transport uses microtubules.

It proceeds in both anterograde and retrograde directions

Front 37

What powers anterograde transport?

Back 37

Kinesins

Hint 37

Kinesins in bold!

Front 38

What powers retrograde transport?

Back 38

Dynein

Hint 38

Dynein in bold!

Front 39

What are axon terminals?

Back 39

Specialized endings where axons terminate

Front 40

What do axon terminals contain?

Back 40

Synaptic vesicles containing neurotransmitters

Front 41

When do the axon terminals release vesicles?

Back 41

Upon arrival of the nerve impulse

Front 42

Axons may be gathered into

Back 42

Bundles

Front 43

What is anterograde transport?

Back 43

Transport from cell body to the terminal that brings newly synthesized materials (like vesicles) down the axon.

Can be fast or slow

Front 44

What is retrograde transport?

Back 44

Transport form terminal to the cell body.

Can only be slow

Front 45

Bundles of axons with Schawnn cells in the PNS form

Back 45

Nerves

Front 46

Bundles of axons and glia cells in the CNS form

Back 46

White matter of the CNS

Front 47

Do axons have Nissl bodies?

Back 47

No

Front 48

Which neuronal components have Nissl bodies?

Back 48

1. Cell body

2. Dendrites when close to cell body

Front 49

What is myelin?

Back 49

An insulating layer that forms around nerves in the brain and spinal cord

Front 50

How is myelin formed?

Back 50

Schawn cells repeatedly wrap around an axon and form a myelin sheath

Front 51

What is myelin composed of?

Back 51

Multiple layers of the Schawn cell membrane (lipid bilayer)

Front 52

How do schawn cells surround axons?

Back 52

Schawn cells surround axons in one of two ways:

1. Wrap around a single axon over and over forming a myelin sheath

2. Surround several axons

Front 53

Axons can be

Back 53

Myelinated or unmyelinated depending on the type of covering provided by their supporting cells

Front 54

What surrounds unmyelinated axons?

Back 54

Unmyelinated axons in peripheral nerves are surrounded by the cytoplasm of Schawn cells

Front 55

Describe an unmyelinated axon

Back 55

1. Have a small diameter and a relatively slow conduction velocity

2. A single Schawn cell may ensheath several axons

Front 56

What surrounds myelinated axons?

Back 56

Myelinated axons are surrounded by several layers of the Schawn cell membrane

Front 57

Describe a myelinated axon

Back 57

1. Have a larger diameter

2. They are ensheated in myelin

Front 58

What are Schawn cells?

Back 58

They are the myelin-forming cells of the peripheral nervous system (PNS)

They contain elongated nuclei that lie parallel to the axons of peripheral neurons

Front 59

When does myelination in the PNS begin?

Back 59

During the 4th month of development

Front 60

How many axons can one Schawn cell myelinate?

Back 60

Only one axon

Front 61

How many axons can one Schawn cell surround?

Back 61

Several axons

Front 62

All axons in the PNS are surrounded by

Back 62

Schawn cells

Front 63

Schawn cells can repeatedly wrap around an axon and form

Back 63

A myelin sheath

Front 64

What are oligodendrocytes?

Back 64

They are the myelin-forming cells of the central nervous system (CNS)

Front 65

When does myelination begin in the CNS?

Back 65

During the 4th month of development and continues into the second decade of life

Front 66

How many axons can an olygodendrocyte myelinate?

Back 66

An individual oligodendrocyte is able to myelinate many axons

Hint 66

"An individual oligodendrocyte is able to myelinate many axons" in bold!

Front 67

What is a node of ranvier?

Back 67

A myelin free region at the junction between adjacent Schawn cells

Front 68

The node of ranvier is exposed to

Back 68

The extracellular space

Front 69

What is the relationship between the node of ranvier and action potentials?

Back 69

The action potential skips from node to node in a process called saltatory conduction

Hint 69

"The action potential skips from node to node in a process called saltatory conduction" in bold!

Front 70

Myelinated axons conduct action potentials

Back 70

Rapidly

Front 71

What is the composition of myelin?

Back 71

Because myelin is of membrane origin, it is rich in phospholipids and cholesterol

Front 72

The degeneration of oligodendrocytes results in

Back 72

Demyelinating disorders such as multiple sclerosis

Hint 72

Clinical Correlate

Front 73

What is the function of myelin?

Back 73

The myelin sheath electrically insulates the axon and increases the speed of nerve impulse conduction

Front 74

Each axon in the PNS is surrounded by

Back 74

1. Schawn cells (+/- myelin)

2. Basal lamina secreted by the schawn cell

3. CT wrapping (endoneurium)

Front 75

What is the general classification of neurons according to processes?

Back 75

1. Unipolar

2. Pseudounipolar

3. Bipolar

4. Mulitpolar

Front 76

What is the classification of neurons according to functional role?

Back 76

1. Motor neurons

2. Sensory neurons

Front 77

What are unipolar neurons?

Back 77

They are neurons that have one axon and no dendrites, and probably occur only during development

Front 78

What are pseudounipolar neurons?

Back 78

They are neurons that have one axons that divides close to the cell body into two long processes (one to the periphery and one to the CNS)

Front 79

Name the two processes present in pseudounipolar neurons?

Back 79

Central process

Peripheral process

Front 80

Which process in pseudounipolar neurons function as dendrites?

Back 80

The peripheral process

Front 81

What is the function of pseudounipolar neurons?

Back 81

General sensory: touch, pain, vibration, position sense

Front 82

Where are pseudounipolar neurons found?

Back 82

Dorsal root ganglia

Cranial ganglia sensory in fucntion (trigeminal)

Front 83

What are bipolar neurons?

Back 83

They are neurons that have one axon and one dendrite at opposite poles

Front 84

What is the function of bipolar neurons?

Back 84

Special sensory: vision (retina), hearing and balance (inner ear), smell (olfactory mucosa)

Front 85

Where are bipolar neurons found?

Back 85

1. Cochlear ganglia

2. Vestibular ganglia

3. Retina

4. Olfactory mucosa

Front 86

What are multipolar neurons?

Back 86

They are neurons that have one axon and multiple dendrites

Front 87

What is the function of multipolar neurons?

Back 87

1. Motor neurons: LMN to skeleltal muscle

2. Autonomic neurons: sympathetic and parasympathetic neurons

Front 88

Where are multipolar neurons found?

Back 88

Most neurons in the body and the CNS are multipolar neurons:

Ventral horn neurons in the spinal cord

Front 89

What are motor neurons?

Back 89

They are neurons that control effector organs and muscle fibers

Front 90

What are sensory neurons?

Back 90

They are neurons that receive sensory stimuli from internal or external environment and relay them to the CNS

Front 91

What are synapses?

Back 91

They are specialized membrane junctions designed for the unidirectional communication between neurons or between neurons and effector cells

Front 92

What is the synaptic cleft?

Back 92

The space between the pre and post-synaptic membranes

Front 93

Where are synapses located?

Back 93

Between and axon and a dendrite (axodendritic) or between and axon and a cell body (axosomatic).

Synapses between dendrites (dendrodendritic) and between axons (axoaxonic) also occur

Front 94

What do synapses contain?

Back 94

Synaptic vesicles

Front 95

What are synaptic vesicles?

Back 95

Spherical/ovoid structures in the axoplasm that contain neurotransmitters

Front 96

When are neurotransmitters released into the synaptic cleft?

Back 96

When the synaptic vesicles fuse with the pre-synaptic membrane

Front 97

Neurotransmitters can excite, which means

Back 97

Depolarize the post-synaptic membrane

Front 98

Neurotransmitters can inhibit, which means

Back 98

Hyperpolarize the post-synaptic membrane

Front 99

Neurotransmitters can excite or inhibit the post-synaptic membrane depending on

Back 99

The type of receptor to which it binds

Front 100

Neurotransmitters can be inactivated in the synaptic cleft by

Back 100

1. Enzymatic degradation

2. Reuptake

Front 101

What is a ganglia?

Back 101

A collection of cell bodies (and attached axons) in the PNS

Front 102

What is a peripheral nerve?

Back 102

A collection of axons (no cell bodies)

Front 103

Name the types of ganglia in the PNS

Back 103

1. Dorsal root ganglia (spinal, sensory). Big

2. Sympathetic ganglia (paravertebral, superior cervical, prevertebral). Big

3. Parasympathetic ganglia. Teeny tiny

Front 104

All ganglia contain

Back 104

1. Cell bodies of neurons (and attached axons)

2. Glial cells: satellite cells around cell bodies, schawn cells around axons, CT, and blood vessels

Front 105

What are peripheral nerves composed of?

Back 105

Bundles of axons (myelinated and unmyelinated, big and small, motor and sensory) with their supporting Schawn cells, all held together by several layers of CT (and blood vessels)

Front 106

What are the nerves 3 layers of connective tissue?

Back 106

1. Endoneurium (around one axon)

2. Perineurium (around a bundle of axons)

3. Epineurium (around a gross nerve)

Front 107

What is the perineurium made of?

Back 107

Specialized fibroblasts linked together forming part of the blood-nerve barrier

Front 108

What is the function of peripheral nerves?

Back 108

All peripheral nerves are mixed in function

Mixed = Motor + Sensory

Front 109

What happens structurally when there is damage to a peripheral nerve?

Back 109

1. Axons are severed and separated from their cell bodies

2. The separated portion degenerates

3. There is a possibility that the portion connected to the cell body can sprout, grow, and reconnect with the receptors and/or muscle fibers

3. This regeneration or regrowth of the severed axons is guided by the Schawn cells and fibroblasts of the endoneurium

Front 110

What happens functionally when there is damage to a peripheral nerve?

Back 110

All functions carried out by the axons are lost, both sensory and motor.

Function may return with successful regeneration

Front 111

If you see a cell body you are in a

Back 111

Ganglia

Front 112

What are the functions of neuroglia?

Back 112

Mechanically support and maintain the proper environment of the neurons

Front 113

What is the neuron-neuroglia ration?

Back 113

Neuroglia are greater in number than neurons

Front 114

Are neuroglia capable of proliferating?

Back 114

Yes

Front 115

In the adult, where are primary brain tumors derived from?

Back 115

Neuroglia (glial cells)

Front 116

What are gliomas?

Back 116

Glial cell tumors. They are the common primary brain tumors of the adult, including: glioblastomas, astrocytomas, ependymomas, and oligodendrogliomas

Front 117

What are astrocytes?

Back 117

1. They are the largest of the neuroglial cells.

2. They have a centrally located nucleus and numerous long processes with expanded vascular end-feet (pedicels), which attach to the walls of capillaries

3. They contain intermediate filaments made of glial fibrillary acidic protein

Front 118

What are the functions of astrocytes?

Back 118

1. Modulate ionic environment of neurons

2. Involved in the maintenance the blood-brain barrier and the exchange of metabolites

3. Important in controlling the microenvironment of nerve cells

Front 119

What are oligodendrocytes?

Back 119

1. They myelinate axons in the CNS: can form a myelin sheath around segments of up to 50 axons

2. They are the major component of white matter

3. Have a small nuclei

4. Contain abundant mitochondria, ribosomes and microtubules
2.

Front 120

What are microglia?

Back 120

Small, dense, elongated cells with elongated nuclei

Front 121

What are the functions of microglia?

Back 121

Immune cell:

1. Active in antigen sensing

2. Active in phagocytosis

3. Part of the mononuclear phagocytic system

Hint 121

Mononuclear phagocytic system in bold!

Front 122

What germ layer do microglia derive from?

Back 122

From monocytes in the blood (mesoderm)

Front 123

What germ layer do neuroglial cells derive from?

Back 123

Neuroectoderm, except microglia which derives from mesoderm

Front 124

When do microglial cells become prominent?

Back 124

With injury

Front 125

What are ependymal cells?

Back 125

Cilliated cells that line the ventricles (cavities) of the brain and the central canal of the spinal cord

They are capable of mitosis and can develop long processes that deeply penetrate neural tissue

Front 126

What are the functions of ependymal cells?

Back 126

1. Form the epithelial lining of the choroid plexus, which secretes cerobrospinal fluid (CSF) into the ventricles

2. Cilia on the ependymal cells move CSF through the ventricles

Front 127

What is the neuromuscular junction?

Back 127

A specialized synapse between a lower motor neuron and a skeletal muscle fiber

Front 128

Where does the neuromuscular junction occur?

Back 128

At the motor end plate

Front 129

Describe the interaction of the axon and the muscle in the NMJ

Back 129

1. At the NMJ the axon forms a number of small branches that fit into grooves on the muscle where the post-synaptic membrane is convoluted into numerous folds, called the sub-neural clefts

2. Ach released from the axon depolarizes the sarcolemma via the acetylcholine nicotinic receptors

Front 130

What is myasthenia gravis?

Back 130

It's a disease characterized by weakness and easy fatigue of the muscles

It can be life threatening if swallowing or breathing is affected

Hint 130

Clinical Correlation

Front 131

What causes myasthenia gravis?

Back 131

1. It's caused by an autoimmune response to the Ach receptor.

2. Normally, old receptors are constantly removed by endocytosis, transported, and degraded in the lysosomes

3. Old receptors are replaced by new receptors, made in the golgi apparatus and then inserted into the junctional folds

4. The normal half life of a receptor is about 10 days

5. In myasthenia gravis, the half-life of the receptor is reduced to about 2 days, resulting in a marked decrease in the number of available receptors

Front 132

What is the treatment for myasthenia gravis?

Back 132

Administration of AchE inhibitors, which by slowing the rate of degradation of Ach, the increase the binding time of Ach to the remaining receptors.

The usual response is prompt improvement of muscle power

AchE serve as a diagnostic and therapeutic tool

Front 133

What are sensory nerve endings?

Back 133

Distal tips of sensory neurons (nerve "beginning") that respond to a sensory stimuli by initiating a nerve impulse

Front 134

What is the function of nerve endings?

Back 134

They convert sensation into electrical impulses

Front 135

What are the functions of naked or free nerve endings?

Back 135

Perceive touch, pain, and temperature

Front 136

Where are free nerve endings?

Back 136

They are common, but hidden in the CT and epithelium

Front 137

What are encapsulated sensory receptors?

Back 137

Nerve endings with fancy CT around them

They are the meissner's corpuscle (touch), the pacinian corpuscle (vibration), and the muscle spindle (stretch receptor)

Front 138

What is the cerebral cortex?

Back 138

It's the thin outer grey layer of the cerebrum

Front 139

How is the cerebral cortex organized?

Back 139

Into 3-6 layers of cells

Front 140

What is the largest cell of the cerebral cortex?

Back 140

The pyramidal cells

Front 141

What is the cerebellar cortex?

Back 141

The thin outer gray area of the cerebellum

Front 142

How is the cerebellar cortex organized?

Back 142

Into 3 layers

Front 143

What is the largest cell of the cerebellar cortex?

Back 143

The purkinje cell

Front 144

During what week of development does the nervous system form?

Back 144

During the 3rd week of development

Front 145

What germ layer forms the nervous system?

Back 145

The surface ectoderm

Front 146

Describe the development of the nervous system

Back 146

The surface ectoderm thickens, folds, and invaginates downward to form:

1. Neural tube

2. Neural crest

Front 147

What is the neural tube?

Back 147

A hollow tube initially, open at both ends that forms most of the CNS including: neurons of the CNS, CNS glia, the neural retina, and the posterior pituitary

Front 148

What is the neural crest?

Back 148

A collection of cells not incorporated into the neural tube that eventually migrate away and form most of the PNS including: all ganglionic cells, PNS glia, the meninges, adrenal medulla, melanocytes, scattered endocrine cells, and diverse structures in the head and neck

Front 149

Describe the development of the nervous system

Back 149

The surface ectoderm thickens, folds, and invaginates downward to form:

1. Neural tube

2. Neural crest

Front 150

What is the neural tube?

Back 150

A hollow tube initially, open at both ends that forms most of the CNS including: neurons of the CNS, CNS glia, the neural retina, and the posterior pituitary

Front 151

what are the four main types of receptors?

Back 151

ionotropic, G-protein coupled, kinase linked, nuclear

Front 152

What are the 3 levels of connective tissue wrappings in skeletal muscle?

Back 152

Endomysium

Perimysium

Epimysium

Front 153

What is the endomysium?

Back 153

The connective tissue that surrounds individual muscle fibers

Front 154

What is the perimysium?

Back 154

The connective tissue that surrounds groups (fascicles) of muscle fibers

Front 155

What is the epimysium?

Back 155

The connective tissue that surrounds the entire muscle