21122010

1

Nervous tissue charachteristics

neurons glial cells

Functional Organization

of Nervous Tissue

The Nervous System

bull Components

ndash Brain spinal cord nerves sensory receptors

bull Responsible for

ndash Sensory perceptions mental activities

stimulating muscle movements secretions of

many glands

bull Subdivisions

ndash Central nervous system (CNS)

ndash Peripheral nervous system (PNS)

The Nervous System

bull THE NERVOUS SYSTEM

bull THE RAPID COMMUNICATION SYSTEM OF THE BODY (CARRYING ELECTROCHEMICAL IMPULSES)

bull Functions of the nervous system-

bull SENSATION - in internal amp external environment

bull INTEGRATION - of sensory information

bull CO-ORDINATION - of voluntary amp involuntary actions

bull REGULATION - of peripheral structures amp systems

bull HIGHER FUNCTIONS -

CENTRAL NERVOUS SYSTEM

(CNS)

bull = BRAIN SPINAL CORD

bull (Approx 95 bodys neural tissue)

bull Performs INTEGRATION

amp CO-ORDINATION of nervous activity

PERIPHERAL NERVOUS

SYSTEM (PNS)

bull ALL OF NEURAL TISSUE OUTSIDE

CNS

bull Links CNS with all of body tissues amp

outside world

21122010

2

Central Nervous System

bull Consists of

ndash Brainbull Located in cranial vault

of skull

ndash Spinal cordbull Located in vertebral

canal

bull Brain and spinal cord

ndash Continuous with each other at foramen magnum

Peripheral Nervous System

bull Two subcategories

ndash Sensory or afferent

ndash Motor or efferent

bull Divisions

ndash Somatic nervous

system

ndash Autonomic nervous

system (ANS)

raquo Sympathetic

raquo Parasympathetic

raquo Enteric

Nervous System Organization Another way to look at the

Nervous System

bull The master controlling and communicating

system of the body

bull Functions

ndash Sensory input ndash monitoring stimuli occurring

inside and outside the body

ndash Integration ndash interpretation of sensory input

ndash Motor output ndash response to stimuli by

activating effector organs

Nervous SystemOrganization of the Nervous

System

bull Central nervous system (CNS)

ndash Brain and spinal cord

ndash Integration and command center

bull Peripheral nervous system (PNS)

ndash Paired spinal and cranial nerves

ndash Carries messages to and from the spinal cord

and brain

21122010

3

bull Sensory (afferent) division

ndash Sensory afferent fibers ndash carry impulses from skin

skeletal muscles and joints to the brain

ndash Visceral afferent fibers ndash transmit impulses from

visceral organs to the brain

bull Motor (efferent) division

ndash Transmits impulses from the CNS to effector organs

Peripheral Nervous System

(PNS) Two Functional Divisions

bull Somatic nervous system

ndash Conscious control of skeletal muscles

bull Autonomic nervous system (ANS)

ndash Regulates smooth muscle cardiac muscle and

glands

ndash Divisions ndash sympathetic and parasympathetic

Motor Division Two Main Parts

bull The two principal cell types of the nervous

system are

ndash Neurons ndash excitable cells that transmit electrical

signals

ndash Supporting cells ndash cells that surround and wrap

neurons

Histology of Nerve Tissue Cells of Nervous System

bull Neurons or nerve cells

ndash Receive stimuli and

transmit action

potentials

ndash Organization

bull Cell body or soma

bull Dendrites Input

bull Axons Output

bull Neuroglia or glial cells

ndash Support and protect

neurons

Nerve Cells

bull 1048708 Two distinct cell types form nervous

tissue

bull 1048708 Neurons which are excitable cells that

initiate and transmit nerve impulses

bull 1048708 Glial cells which are nonexcitable cells

that support and protect the neurons

Characteristics of Neurons

bull 1048708 Neurons have a high metabolic rate

bull 1048708 Neurons have extreme longevity

bull 1048708 Neurons typically are non-mitotic

21122010

4

Neuron Structure

bull 1048708 Neurons come in all shapes and sizes

but all neurons share certain basic structural

features

bull 1048708 A typical neuron has a cell body

dendrites and axons

bull Neuron Structure ndash Cell Body

bull 1048708 The cell body serves as the neuronrsquos

control center and is responsible for

receiving integrating and sending nerve

impulses

Neuron Structure ndash Dendrites

bull 1048708 Dendrites tend to be shorter smaller

processes that branch off the cell body

bull 1048708 Some neurons have only one dendrite

while others have many

bull 1048708 Dendrites conduct nerve impulses

toward the cell body they receive input and

then transfer it to the cell body for

processing

bull 1048708 The more dendrites a neuron has the

more nerve impulses that neuron can

receive from other cells

Neuron Structure ndash Axon

bull 1048708 The larger typically longer nerve cell

process emanating from the cell body is the

axon sometimes called a nerve fiber

bull 1048708 Most neurons have only one axon

bull 1048708 The axon transmits a nerve impulse

away from the cell body toward another

cell

Types of Neurons

bull Functional classification

ndash Sensory or afferent Action potentials toward CNS

ndash Motor or efferent Action potentials away from CNS

ndash Interneurons or association neurons Within CNS from one

neuron to another

bull Structural classification

ndash Multipolar bipolar unipolar

21122010

5

Classifications of Neuronsbull 1048708 Neurons vary widely in morphology

and location

bull 1048708 They can be classified according to

either their structure or their function

bull 1048708 Neurons can be classified according to

the number of processes extending from the

cell body

bull 1048708 unipolar neuron has a single process

bull 1048708 bipolar neurons have two processes

bull 1048708 multipolar neurons have three or more

processes

bull The neurons entirely within the CNS are

upper motor neurons

bull

bull The neurons with cell bodies in the CNS

but whose axons pass into the peripheral

nerves are lower motor neurons

bull

11-27

bull Interneurons

bull 1048708 Interneurons or association neurons lie

entirely within the CNS and are multipolar

bull 1048708 They receive nerve impulses from

many other neurons and carry out the

integrative function of the nervous system

bull 1048708 Thus interneurons facilitate

communication between sensory and motor

neurons

Neuroglia of CNS

bull Astrocytesndash Regulate extracellular brain fluid composition

ndash Promote tight junctions to form blood-brain barrier

bull Ependymal Cellsndash Line brain ventricles and spinal cord central canal

ndash Help form choroid plexuses that secrete CSF

Neuroglia of CNS

bull Microglia

ndash Specialized macrophages

bull Oligodendrocytes

ndash Form myelin sheaths if surround axon

21122010

6

Neuroglia of PNS

bull Schwann cells or neurolemmocytes

ndash Wrap around portion of only one axon to form myelin sheath

bull Satellite cells

ndash Surround neuron cell bodies in ganglia provide support and nutrients

bull Satellite cells (syn mantlecells or amphicytes) are

flattened Schwann cells a type of glial cell lining the

exterior surface of neurons in the peripheral nervous

system Satellite cells also surround neuron cell bodies

within ganglia They are thought to have a similar role to

astrocytes in the central nervous system (CNS) They

supply nutrients to the surrounding neurons and also have

some structural function Satellite cells also act as

protective cushioning cells

11-33

bull Sometimes referred to as neuroglia occur

withinboth the CNS and the PNS

bull 1048708 Glial cells are smaller and capable of

mitosis

bull 1048708 Glial cells do not transmit nerve

impulses

bull 1048708 Glial cells physically protect and help

nourish neurons and provide an organized

supporting framework for all the nervous

tissue

bull 1048708 Glial cells far outnumber neurons

bull 1048708 Glial cells account for roughly half the

volume of the central nervous system

bull They say that einsteinrsquos brain did not

contain more neurones but more glial cells

11-36

21122010

2

Central Nervous System

bull Consists of

ndash Brainbull Located in cranial vault

of skull

ndash Spinal cordbull Located in vertebral

canal

bull Brain and spinal cord

ndash Continuous with each other at foramen magnum

Peripheral Nervous System

bull Two subcategories

ndash Sensory or afferent

ndash Motor or efferent

bull Divisions

ndash Somatic nervous

system

ndash Autonomic nervous

system (ANS)

raquo Sympathetic

raquo Parasympathetic

raquo Enteric

Nervous System Organization Another way to look at the

Nervous System

bull The master controlling and communicating

system of the body

bull Functions

ndash Sensory input ndash monitoring stimuli occurring

inside and outside the body

ndash Integration ndash interpretation of sensory input

ndash Motor output ndash response to stimuli by

activating effector organs

Nervous SystemOrganization of the Nervous

System

bull Central nervous system (CNS)

ndash Brain and spinal cord

ndash Integration and command center

bull Peripheral nervous system (PNS)

ndash Paired spinal and cranial nerves

ndash Carries messages to and from the spinal cord

and brain

21122010

3

bull Sensory (afferent) division

ndash Sensory afferent fibers ndash carry impulses from skin

skeletal muscles and joints to the brain

ndash Visceral afferent fibers ndash transmit impulses from

visceral organs to the brain

bull Motor (efferent) division

ndash Transmits impulses from the CNS to effector organs

Peripheral Nervous System

(PNS) Two Functional Divisions

bull Somatic nervous system

ndash Conscious control of skeletal muscles

bull Autonomic nervous system (ANS)

ndash Regulates smooth muscle cardiac muscle and

glands

ndash Divisions ndash sympathetic and parasympathetic

Motor Division Two Main Parts

bull The two principal cell types of the nervous

system are

ndash Neurons ndash excitable cells that transmit electrical

signals

ndash Supporting cells ndash cells that surround and wrap

neurons

Histology of Nerve Tissue Cells of Nervous System

bull Neurons or nerve cells

ndash Receive stimuli and

transmit action

potentials

ndash Organization

bull Cell body or soma

bull Dendrites Input

bull Axons Output

bull Neuroglia or glial cells

ndash Support and protect

neurons

Nerve Cells

bull 1048708 Two distinct cell types form nervous

tissue

bull 1048708 Neurons which are excitable cells that

initiate and transmit nerve impulses

bull 1048708 Glial cells which are nonexcitable cells

that support and protect the neurons

Characteristics of Neurons

bull 1048708 Neurons have a high metabolic rate

bull 1048708 Neurons have extreme longevity

bull 1048708 Neurons typically are non-mitotic

21122010

4

Neuron Structure

bull 1048708 Neurons come in all shapes and sizes

but all neurons share certain basic structural

features

bull 1048708 A typical neuron has a cell body

dendrites and axons

bull Neuron Structure ndash Cell Body

bull 1048708 The cell body serves as the neuronrsquos

control center and is responsible for

receiving integrating and sending nerve

impulses

Neuron Structure ndash Dendrites

bull 1048708 Dendrites tend to be shorter smaller

processes that branch off the cell body

bull 1048708 Some neurons have only one dendrite

while others have many

bull 1048708 Dendrites conduct nerve impulses

toward the cell body they receive input and

then transfer it to the cell body for

processing

bull 1048708 The more dendrites a neuron has the

more nerve impulses that neuron can

receive from other cells

Neuron Structure ndash Axon

bull 1048708 The larger typically longer nerve cell

process emanating from the cell body is the

axon sometimes called a nerve fiber

bull 1048708 Most neurons have only one axon

bull 1048708 The axon transmits a nerve impulse

away from the cell body toward another

cell

Types of Neurons

bull Functional classification

ndash Sensory or afferent Action potentials toward CNS

ndash Motor or efferent Action potentials away from CNS

ndash Interneurons or association neurons Within CNS from one

neuron to another

bull Structural classification

ndash Multipolar bipolar unipolar

21122010

5

Classifications of Neuronsbull 1048708 Neurons vary widely in morphology

and location

bull 1048708 They can be classified according to

either their structure or their function

bull 1048708 Neurons can be classified according to

the number of processes extending from the

cell body

bull 1048708 unipolar neuron has a single process

bull 1048708 bipolar neurons have two processes

bull 1048708 multipolar neurons have three or more

processes

bull The neurons entirely within the CNS are

upper motor neurons

bull

bull The neurons with cell bodies in the CNS

but whose axons pass into the peripheral

nerves are lower motor neurons

bull

11-27

bull Interneurons

bull 1048708 Interneurons or association neurons lie

entirely within the CNS and are multipolar

bull 1048708 They receive nerve impulses from

many other neurons and carry out the

integrative function of the nervous system

bull 1048708 Thus interneurons facilitate

communication between sensory and motor

neurons

Neuroglia of CNS

bull Astrocytesndash Regulate extracellular brain fluid composition

ndash Promote tight junctions to form blood-brain barrier

bull Ependymal Cellsndash Line brain ventricles and spinal cord central canal

ndash Help form choroid plexuses that secrete CSF

Neuroglia of CNS

bull Microglia

ndash Specialized macrophages

bull Oligodendrocytes

ndash Form myelin sheaths if surround axon

21122010

6

Neuroglia of PNS

bull Schwann cells or neurolemmocytes

ndash Wrap around portion of only one axon to form myelin sheath

bull Satellite cells

ndash Surround neuron cell bodies in ganglia provide support and nutrients

bull Satellite cells (syn mantlecells or amphicytes) are

flattened Schwann cells a type of glial cell lining the

exterior surface of neurons in the peripheral nervous

system Satellite cells also surround neuron cell bodies

within ganglia They are thought to have a similar role to

astrocytes in the central nervous system (CNS) They

supply nutrients to the surrounding neurons and also have

some structural function Satellite cells also act as

protective cushioning cells

11-33

bull Sometimes referred to as neuroglia occur

withinboth the CNS and the PNS

bull 1048708 Glial cells are smaller and capable of

mitosis

bull 1048708 Glial cells do not transmit nerve

impulses

bull 1048708 Glial cells physically protect and help

nourish neurons and provide an organized

supporting framework for all the nervous

tissue

bull 1048708 Glial cells far outnumber neurons

bull 1048708 Glial cells account for roughly half the

volume of the central nervous system

bull They say that einsteinrsquos brain did not

contain more neurones but more glial cells

11-36

21122010

3

bull Sensory (afferent) division

ndash Sensory afferent fibers ndash carry impulses from skin

skeletal muscles and joints to the brain

ndash Visceral afferent fibers ndash transmit impulses from

visceral organs to the brain

bull Motor (efferent) division

ndash Transmits impulses from the CNS to effector organs

Peripheral Nervous System

(PNS) Two Functional Divisions

bull Somatic nervous system

ndash Conscious control of skeletal muscles

bull Autonomic nervous system (ANS)

ndash Regulates smooth muscle cardiac muscle and

glands

ndash Divisions ndash sympathetic and parasympathetic

Motor Division Two Main Parts

bull The two principal cell types of the nervous

system are

ndash Neurons ndash excitable cells that transmit electrical

signals

ndash Supporting cells ndash cells that surround and wrap

neurons

Histology of Nerve Tissue Cells of Nervous System

bull Neurons or nerve cells

ndash Receive stimuli and

transmit action

potentials

ndash Organization

bull Cell body or soma

bull Dendrites Input

bull Axons Output

bull Neuroglia or glial cells

ndash Support and protect

neurons

Nerve Cells

bull 1048708 Two distinct cell types form nervous

tissue

bull 1048708 Neurons which are excitable cells that

initiate and transmit nerve impulses

bull 1048708 Glial cells which are nonexcitable cells

that support and protect the neurons

Characteristics of Neurons

bull 1048708 Neurons have a high metabolic rate

bull 1048708 Neurons have extreme longevity

bull 1048708 Neurons typically are non-mitotic

21122010

4

Neuron Structure

bull 1048708 Neurons come in all shapes and sizes

but all neurons share certain basic structural

features

bull 1048708 A typical neuron has a cell body

dendrites and axons

bull Neuron Structure ndash Cell Body

bull 1048708 The cell body serves as the neuronrsquos

control center and is responsible for

receiving integrating and sending nerve

impulses

Neuron Structure ndash Dendrites

bull 1048708 Dendrites tend to be shorter smaller

processes that branch off the cell body

bull 1048708 Some neurons have only one dendrite

while others have many

bull 1048708 Dendrites conduct nerve impulses

toward the cell body they receive input and

then transfer it to the cell body for

processing

bull 1048708 The more dendrites a neuron has the

more nerve impulses that neuron can

receive from other cells

Neuron Structure ndash Axon

bull 1048708 The larger typically longer nerve cell

process emanating from the cell body is the

axon sometimes called a nerve fiber

bull 1048708 Most neurons have only one axon

bull 1048708 The axon transmits a nerve impulse

away from the cell body toward another

cell

Types of Neurons

bull Functional classification

ndash Sensory or afferent Action potentials toward CNS

ndash Motor or efferent Action potentials away from CNS

ndash Interneurons or association neurons Within CNS from one

neuron to another

bull Structural classification

ndash Multipolar bipolar unipolar

21122010

5

Classifications of Neuronsbull 1048708 Neurons vary widely in morphology

and location

bull 1048708 They can be classified according to

either their structure or their function

bull 1048708 Neurons can be classified according to

the number of processes extending from the

cell body

bull 1048708 unipolar neuron has a single process

bull 1048708 bipolar neurons have two processes

bull 1048708 multipolar neurons have three or more

processes

bull The neurons entirely within the CNS are

upper motor neurons

bull

bull The neurons with cell bodies in the CNS

but whose axons pass into the peripheral

nerves are lower motor neurons

bull

11-27

bull Interneurons

bull 1048708 Interneurons or association neurons lie

entirely within the CNS and are multipolar

bull 1048708 They receive nerve impulses from

many other neurons and carry out the

integrative function of the nervous system

bull 1048708 Thus interneurons facilitate

communication between sensory and motor

neurons

Neuroglia of CNS

bull Astrocytesndash Regulate extracellular brain fluid composition

ndash Promote tight junctions to form blood-brain barrier

bull Ependymal Cellsndash Line brain ventricles and spinal cord central canal

ndash Help form choroid plexuses that secrete CSF

Neuroglia of CNS

bull Microglia

ndash Specialized macrophages

bull Oligodendrocytes

ndash Form myelin sheaths if surround axon

21122010

6

Neuroglia of PNS

bull Schwann cells or neurolemmocytes

ndash Wrap around portion of only one axon to form myelin sheath

bull Satellite cells

ndash Surround neuron cell bodies in ganglia provide support and nutrients

bull Satellite cells (syn mantlecells or amphicytes) are

flattened Schwann cells a type of glial cell lining the

exterior surface of neurons in the peripheral nervous

system Satellite cells also surround neuron cell bodies

within ganglia They are thought to have a similar role to

astrocytes in the central nervous system (CNS) They

supply nutrients to the surrounding neurons and also have

some structural function Satellite cells also act as

protective cushioning cells

11-33

bull Sometimes referred to as neuroglia occur

withinboth the CNS and the PNS

bull 1048708 Glial cells are smaller and capable of

mitosis

bull 1048708 Glial cells do not transmit nerve

impulses

bull 1048708 Glial cells physically protect and help

nourish neurons and provide an organized

supporting framework for all the nervous

tissue

bull 1048708 Glial cells far outnumber neurons

bull 1048708 Glial cells account for roughly half the

volume of the central nervous system

bull They say that einsteinrsquos brain did not

contain more neurones but more glial cells

11-36

21122010

4

Neuron Structure

bull 1048708 Neurons come in all shapes and sizes

but all neurons share certain basic structural

features

bull 1048708 A typical neuron has a cell body

dendrites and axons

bull Neuron Structure ndash Cell Body

bull 1048708 The cell body serves as the neuronrsquos

control center and is responsible for

receiving integrating and sending nerve

impulses

Neuron Structure ndash Dendrites

bull 1048708 Dendrites tend to be shorter smaller

processes that branch off the cell body

bull 1048708 Some neurons have only one dendrite

while others have many

bull 1048708 Dendrites conduct nerve impulses

toward the cell body they receive input and

then transfer it to the cell body for

processing

bull 1048708 The more dendrites a neuron has the

more nerve impulses that neuron can

receive from other cells

Neuron Structure ndash Axon

bull 1048708 The larger typically longer nerve cell

process emanating from the cell body is the

axon sometimes called a nerve fiber

bull 1048708 Most neurons have only one axon

bull 1048708 The axon transmits a nerve impulse

away from the cell body toward another

cell

Types of Neurons

bull Functional classification

ndash Sensory or afferent Action potentials toward CNS

ndash Motor or efferent Action potentials away from CNS

ndash Interneurons or association neurons Within CNS from one

neuron to another

bull Structural classification

ndash Multipolar bipolar unipolar

21122010

5

Classifications of Neuronsbull 1048708 Neurons vary widely in morphology

and location

bull 1048708 They can be classified according to

either their structure or their function

bull 1048708 Neurons can be classified according to

the number of processes extending from the

cell body

bull 1048708 unipolar neuron has a single process

bull 1048708 bipolar neurons have two processes

bull 1048708 multipolar neurons have three or more

processes

bull The neurons entirely within the CNS are

upper motor neurons

bull

bull The neurons with cell bodies in the CNS

but whose axons pass into the peripheral

nerves are lower motor neurons

bull

11-27

bull Interneurons

bull 1048708 Interneurons or association neurons lie

entirely within the CNS and are multipolar

bull 1048708 They receive nerve impulses from

many other neurons and carry out the

integrative function of the nervous system

bull 1048708 Thus interneurons facilitate

communication between sensory and motor

neurons

Neuroglia of CNS

bull Astrocytesndash Regulate extracellular brain fluid composition

ndash Promote tight junctions to form blood-brain barrier

bull Ependymal Cellsndash Line brain ventricles and spinal cord central canal

ndash Help form choroid plexuses that secrete CSF

Neuroglia of CNS

bull Microglia

ndash Specialized macrophages

bull Oligodendrocytes

ndash Form myelin sheaths if surround axon

21122010

6

Neuroglia of PNS

bull Schwann cells or neurolemmocytes

ndash Wrap around portion of only one axon to form myelin sheath

bull Satellite cells

ndash Surround neuron cell bodies in ganglia provide support and nutrients

bull Satellite cells (syn mantlecells or amphicytes) are

flattened Schwann cells a type of glial cell lining the

exterior surface of neurons in the peripheral nervous

system Satellite cells also surround neuron cell bodies

within ganglia They are thought to have a similar role to

astrocytes in the central nervous system (CNS) They

supply nutrients to the surrounding neurons and also have

some structural function Satellite cells also act as

protective cushioning cells

11-33

bull Sometimes referred to as neuroglia occur

withinboth the CNS and the PNS

bull 1048708 Glial cells are smaller and capable of

mitosis

bull 1048708 Glial cells do not transmit nerve

impulses

bull 1048708 Glial cells physically protect and help

nourish neurons and provide an organized

supporting framework for all the nervous

tissue

bull 1048708 Glial cells far outnumber neurons

bull 1048708 Glial cells account for roughly half the

volume of the central nervous system

bull They say that einsteinrsquos brain did not

contain more neurones but more glial cells

11-36

21122010

5

Classifications of Neuronsbull 1048708 Neurons vary widely in morphology

and location

bull 1048708 They can be classified according to

either their structure or their function

bull 1048708 Neurons can be classified according to

the number of processes extending from the

cell body

bull 1048708 unipolar neuron has a single process

bull 1048708 bipolar neurons have two processes

bull 1048708 multipolar neurons have three or more

processes

bull The neurons entirely within the CNS are

upper motor neurons

bull

bull The neurons with cell bodies in the CNS

but whose axons pass into the peripheral

nerves are lower motor neurons

bull

11-27

bull Interneurons

bull 1048708 Interneurons or association neurons lie

entirely within the CNS and are multipolar

bull 1048708 They receive nerve impulses from

many other neurons and carry out the

integrative function of the nervous system

bull 1048708 Thus interneurons facilitate

communication between sensory and motor

neurons

Neuroglia of CNS

bull Astrocytesndash Regulate extracellular brain fluid composition

ndash Promote tight junctions to form blood-brain barrier

bull Ependymal Cellsndash Line brain ventricles and spinal cord central canal

ndash Help form choroid plexuses that secrete CSF

Neuroglia of CNS

bull Microglia

ndash Specialized macrophages

bull Oligodendrocytes

ndash Form myelin sheaths if surround axon

21122010

6

Neuroglia of PNS

bull Schwann cells or neurolemmocytes

ndash Wrap around portion of only one axon to form myelin sheath

bull Satellite cells

ndash Surround neuron cell bodies in ganglia provide support and nutrients

bull Satellite cells (syn mantlecells or amphicytes) are

flattened Schwann cells a type of glial cell lining the

exterior surface of neurons in the peripheral nervous

system Satellite cells also surround neuron cell bodies

within ganglia They are thought to have a similar role to

astrocytes in the central nervous system (CNS) They

supply nutrients to the surrounding neurons and also have

some structural function Satellite cells also act as

protective cushioning cells

11-33

bull Sometimes referred to as neuroglia occur

withinboth the CNS and the PNS

bull 1048708 Glial cells are smaller and capable of

mitosis

bull 1048708 Glial cells do not transmit nerve

impulses

bull 1048708 Glial cells physically protect and help

nourish neurons and provide an organized

supporting framework for all the nervous

tissue

bull 1048708 Glial cells far outnumber neurons

bull 1048708 Glial cells account for roughly half the

volume of the central nervous system

bull They say that einsteinrsquos brain did not

contain more neurones but more glial cells

11-36

21122010

6

Neuroglia of PNS

bull Schwann cells or neurolemmocytes

ndash Wrap around portion of only one axon to form myelin sheath

bull Satellite cells

ndash Surround neuron cell bodies in ganglia provide support and nutrients

bull Satellite cells (syn mantlecells or amphicytes) are

flattened Schwann cells a type of glial cell lining the

exterior surface of neurons in the peripheral nervous

system Satellite cells also surround neuron cell bodies

within ganglia They are thought to have a similar role to

astrocytes in the central nervous system (CNS) They

supply nutrients to the surrounding neurons and also have

some structural function Satellite cells also act as

protective cushioning cells

11-33

bull Sometimes referred to as neuroglia occur

withinboth the CNS and the PNS

bull 1048708 Glial cells are smaller and capable of

mitosis

bull 1048708 Glial cells do not transmit nerve

impulses

bull 1048708 Glial cells physically protect and help

nourish neurons and provide an organized

supporting framework for all the nervous

tissue

bull 1048708 Glial cells far outnumber neurons

bull 1048708 Glial cells account for roughly half the

volume of the central nervous system

bull They say that einsteinrsquos brain did not

contain more neurones but more glial cells

11-36

21122010

7

11-37 11-38

Glial Cells of the CNSbull 1048708 Astrocytes exhibit a starlike shape due

to projections from their surface

bull 1048708 Astrocytes are the most abundant glial

cells in the CNS and they constitute over

90 of the tissue in some areas of the brain

bull 1048708 Help form the blood-brain barrier

(BBB) that strictly controls substances

entering the nervous tissue in the brain from

the bloodstream

bull 1048708 Regulate tissue fluid composition

Functions of Glial Cells

bull 1048708 Forming a structural network

bull 1048708 Replacing damaged neurons

bull 1048708 Assisting neuronal development

Myelination

bull 1048708 Neurolemmocytes also called Schwann

cells are associated with PNS axons and are

responsible for myelinating PNS axons

bull 1048708 Myelination is the process by which

part of an axon is wrapped with a myelin

sheath a protective fatty coating that gives

it glossywhite appearance

bull 1048708 The myelin sheath supports protects

and insulates an axon

bull 1048708 No change in voltage can occur across

the membrane in the insulated portion of an

axon

bull 1048708 In the PNS myelin sheaths form from

neurolemmocytes

bull 1048708 In the CNS they form from

oligodendrocytes

21122010

8

11-43 11-44

11-45

Mylenated vs UnmylenatedAxon

bull 1048708 In a myelinated axon the nerve

impulse ldquojumpsrdquo from neurofibril node to

neurofibril node and is known as saltatory

conduction

bull 1048708 In an unmyelinated axon the nerve

impulse must travel the entire length of the

axon a process called continuous

conduction

bull 1048708 A myelinated axon produces a faster

nerve impulse

11-47

Myelinated and Unmyelinated

Axons

bull Myelinated axons

ndash Myelin protects and

insulates axons from

one another

ndash Not continuous

bull Nodes of Ranvier

bull Unmyelinated axons

21122010

9

Electrical Signals

bull Cells produce electrical signals called action

potentials

bull Transfer of information from one part of

body to another

bull Electrical properties result from ionic

concentration differences across plasma

membrane and permeability of membrane

Action Potential Propagation

Saltatory Conduction

11-62

11-63

Regeneration of PNS Axons

bull 1048708 PNS axons are vulnerable to cuts crushing

injuries and other trauma

bull 1048708 A damaged axon can regenerate however if

at least some neurilemma remains

bull 1048708 PNS axon regeneration depends upon three

factors

bull 1048708 the amount of damage

bull 1048708 neurolemmocyte secretion of nerve growth

factors to stimulate outgrowth of severed axons

bull 1048708 the distance between the site of the damaged

axon and the effector organ

21122010

10

11-65 11-66

11-67 11-68

bull A common neurotransmitter is

acetylcholine although there are many

more used by different neurones

Chemical Synapses

bull Componentsndash Presynaptic terminal

ndash Synaptic cleft

ndash Postsynaptic membrane

bull Neurotransmitters released by action potentials in presynaptic terminalndash Synaptic vesicles

ndash Diffusion

ndash Postsynaptic membrane

bull Neurotransmitter removal

21122010

11

Neurotransmitter Removal Summation

11-74

bull Axons may establish synaptic contacts with

bull any portion of the surface of another

neuron

bull except those regions that are myelinated

Motor Neuron

(efferent)multi-polar and efferent

relays information from the CNS to the periphery

21122010

12

Motor Neuron

bull Cell body

bull Dendrites

bull Axon Hillock (AP)

bull Myelinated fibre

ndash Schwann Cell

ndash Node of Ranvier

bull Synaptic Bulb

Nerve impulse propagation

bull Axon Hillock

bull Resting Membrane Potential

bull Membrane Potential

bull Threshold

bull Depolarisation

bull Repolarisation

21122010

8

11-43 11-44

11-45

Mylenated vs UnmylenatedAxon

bull 1048708 In a myelinated axon the nerve

impulse ldquojumpsrdquo from neurofibril node to

neurofibril node and is known as saltatory

conduction

bull 1048708 In an unmyelinated axon the nerve

impulse must travel the entire length of the

axon a process called continuous

conduction

bull 1048708 A myelinated axon produces a faster

nerve impulse

11-47

Myelinated and Unmyelinated

Axons

bull Myelinated axons

ndash Myelin protects and

insulates axons from

one another

ndash Not continuous

bull Nodes of Ranvier

bull Unmyelinated axons

21122010

9

Electrical Signals

bull Cells produce electrical signals called action

potentials

bull Transfer of information from one part of

body to another

bull Electrical properties result from ionic

concentration differences across plasma

membrane and permeability of membrane

Action Potential Propagation

Saltatory Conduction

11-62

11-63

Regeneration of PNS Axons

bull 1048708 PNS axons are vulnerable to cuts crushing

injuries and other trauma

bull 1048708 A damaged axon can regenerate however if

at least some neurilemma remains

bull 1048708 PNS axon regeneration depends upon three

factors

bull 1048708 the amount of damage

bull 1048708 neurolemmocyte secretion of nerve growth

factors to stimulate outgrowth of severed axons

bull 1048708 the distance between the site of the damaged

axon and the effector organ

21122010

10

11-65 11-66

11-67 11-68

bull A common neurotransmitter is

acetylcholine although there are many

more used by different neurones

Chemical Synapses

bull Componentsndash Presynaptic terminal

ndash Synaptic cleft

ndash Postsynaptic membrane

bull Neurotransmitters released by action potentials in presynaptic terminalndash Synaptic vesicles

ndash Diffusion

ndash Postsynaptic membrane

bull Neurotransmitter removal

21122010

11

Neurotransmitter Removal Summation

11-74

bull Axons may establish synaptic contacts with

bull any portion of the surface of another

neuron

bull except those regions that are myelinated

Motor Neuron

(efferent)multi-polar and efferent

relays information from the CNS to the periphery

21122010

12

Motor Neuron

bull Cell body

bull Dendrites

bull Axon Hillock (AP)

bull Myelinated fibre

ndash Schwann Cell

ndash Node of Ranvier

bull Synaptic Bulb

Nerve impulse propagation

bull Axon Hillock

bull Resting Membrane Potential

bull Membrane Potential

bull Threshold

bull Depolarisation

bull Repolarisation

21122010

9

Electrical Signals

bull Cells produce electrical signals called action

potentials

bull Transfer of information from one part of

body to another

bull Electrical properties result from ionic

concentration differences across plasma

membrane and permeability of membrane

Action Potential Propagation

Saltatory Conduction

11-62

11-63

Regeneration of PNS Axons

bull 1048708 PNS axons are vulnerable to cuts crushing

injuries and other trauma

bull 1048708 A damaged axon can regenerate however if

at least some neurilemma remains

bull 1048708 PNS axon regeneration depends upon three

factors

bull 1048708 the amount of damage

bull 1048708 neurolemmocyte secretion of nerve growth

factors to stimulate outgrowth of severed axons

bull 1048708 the distance between the site of the damaged

axon and the effector organ

21122010

10

11-65 11-66

11-67 11-68

bull A common neurotransmitter is

acetylcholine although there are many

more used by different neurones

Chemical Synapses

bull Componentsndash Presynaptic terminal

ndash Synaptic cleft

ndash Postsynaptic membrane

bull Neurotransmitters released by action potentials in presynaptic terminalndash Synaptic vesicles

ndash Diffusion

ndash Postsynaptic membrane

bull Neurotransmitter removal

21122010

11

Neurotransmitter Removal Summation

11-74

bull Axons may establish synaptic contacts with

bull any portion of the surface of another

neuron

bull except those regions that are myelinated

Motor Neuron

(efferent)multi-polar and efferent

relays information from the CNS to the periphery

21122010

12

Motor Neuron

bull Cell body

bull Dendrites

bull Axon Hillock (AP)

bull Myelinated fibre

ndash Schwann Cell

ndash Node of Ranvier

bull Synaptic Bulb

Nerve impulse propagation

bull Axon Hillock

bull Resting Membrane Potential

bull Membrane Potential

bull Threshold

bull Depolarisation

bull Repolarisation

21122010

10

11-65 11-66

11-67 11-68

bull A common neurotransmitter is

acetylcholine although there are many

more used by different neurones

Chemical Synapses

bull Componentsndash Presynaptic terminal

ndash Synaptic cleft

ndash Postsynaptic membrane

bull Neurotransmitters released by action potentials in presynaptic terminalndash Synaptic vesicles

ndash Diffusion

ndash Postsynaptic membrane

bull Neurotransmitter removal

21122010

11

Neurotransmitter Removal Summation

11-74

bull Axons may establish synaptic contacts with

bull any portion of the surface of another

neuron

bull except those regions that are myelinated

Motor Neuron

(efferent)multi-polar and efferent

relays information from the CNS to the periphery

21122010

12

Motor Neuron

bull Cell body

bull Dendrites

bull Axon Hillock (AP)

bull Myelinated fibre

ndash Schwann Cell

ndash Node of Ranvier

bull Synaptic Bulb

Nerve impulse propagation

bull Axon Hillock

bull Resting Membrane Potential

bull Membrane Potential

bull Threshold

bull Depolarisation

bull Repolarisation

21122010

11

Neurotransmitter Removal Summation

11-74

bull Axons may establish synaptic contacts with

bull any portion of the surface of another

neuron

bull except those regions that are myelinated

Motor Neuron

(efferent)multi-polar and efferent

relays information from the CNS to the periphery

21122010

12

Motor Neuron

bull Cell body

bull Dendrites

bull Axon Hillock (AP)

bull Myelinated fibre

ndash Schwann Cell

ndash Node of Ranvier

bull Synaptic Bulb

Nerve impulse propagation

bull Axon Hillock

bull Resting Membrane Potential

bull Membrane Potential

bull Threshold

bull Depolarisation

bull Repolarisation

21122010

12

Motor Neuron

bull Cell body

bull Dendrites

bull Axon Hillock (AP)

bull Myelinated fibre

ndash Schwann Cell

ndash Node of Ranvier

bull Synaptic Bulb

Nerve impulse propagation

bull Axon Hillock

bull Resting Membrane Potential

bull Membrane Potential

bull Threshold

bull Depolarisation

bull Repolarisation