Chapter 9 Nervous system

Types of neurons Sensory neurons -

(aka afferent) - Carry impulses to the spinal cord & brain from all parts of the body

Types of neurons Interneurons -

(aka central connecting neurons) Conduct impulses from sensory neurons to motor neurons. They also connect with each other to form complex central networks of nerve fibers

Types of neurons Motor neurons -

(aka efferent) - Carry impulses away from the brain & spinal cord. - They DO NOT conduct impulses to all parts of the body - Only two types of tissue : Muscle tissue & glandular epithelial tissue

Withdrawal reflex -

(example) Application of an irritating stimulus to the skin of the thigh initiates a three-neuron reflex response that causes contraction of muscles to pull the leg away from the irritant -a three neuron arc reaction.

Microglia -

- Are smaller than astrocytes. They usually remain stationary, but in inflamed or degenerating brain tissue, they enlarge, move about and act as microbe eating scavengers - Help to clean up cell damage resulting from injury & disease

Reflex arc -

- Basic type of neuron pathway & is important to nervous system functioning - the simplest kind of reflex arc is a two-neuron arc "so called" because it consists of only two types of neurons : sensory & motor neurons

Neuron structure Axon -

- One elongated projection from the cell body - They are the processes that carry impulses away from the neuron cell body

Neuron structure Dendrites -

- One or more branching projections from the cell body. - They are the process or projections that carry impulses to the neuron cell body

Transmission of signals from one neuron to the next -__________- is an important part of the nerve conduction process..

Across the synapse

Nerve impulses is also known as...

Action potentials

Blood brain barrier (BBB) -

Along with the walls of the blood vessels, astrocytes branches form a two layer structure. BBB separates the blood tissue & nerve tissue to protect vital brain tissue from harmful chemicals that might be in the blood

reflex -

An involuntary response to impulse conduction over a reflex arc

Nodes of Ranvier -

Are gaps between adjacent Schwann cells.

Glial cells are also known as _________. They attach to neurons and blood vessels holding these structures together

Astrocytes

Three main types of glia cells:

Astrocytes, Microglia, & Oligodendrocytes

What are three types of glia cells?

Astrocytes, microglia, & Schwann cells

Pons -

Bulges out a bit more than the medulla forming a bridge to the narrower midbrain

Neuron structure Each neuron consist of three parts :

Cell body , Dendrites, & Axon

Because there are no Schwann cells in the __________________, axons in the brain & spinal cord have no neurilemma

Central nervous system (CNS)

What is the difference between the central nervous system and the peripheral nervous system?

Central nervous system is the brain and spinal cord; Peripheral nervous system is the rest of the body

Neurotransmitters-

Chemicals by which neurons communicate; at least 30 different compounds have been identified as "it"

The nervous system & the endocrine system

Control of the body's trillion of cells is mainly accomplished by two body-wide communication systems :

Glia -

Do not specialize in transmitting impulses. Instead, they're special types of supporting cells

Each axon in a nerve is surrounded by a thin wrapping of fibrous connective tissue called __________ . Groups of these wrapped axons are called fascicles. Each fascicles is surrounded by a thin, fibrous perineurium. A tough fibrous sheath called epineurium covers the whole nerve

Endoneurium

Each axon in a nerve is surrounded by a thin wrapping of fibrous connective tissue called endoneurium . Groups of these wrapped axons are called _________. Each fascicles is surrounded by a thin, fibrous perineurium. A tough fibrous sheath called epineurium covers the whole nerve

Fascicles

How are glial cells different from neurons?

Glial cells are smaller than neurons, as well as more numerous . They can be metastatic & also act as glue by holding functioning neurons together as well as protecting them.

Most common type of brain tumor called _________ develops from the glial cell

Glioma

Nerve -

Group of peripheral nerve fibers (axons) bundled together like the strands of a cable.

Oligodendrocytes -

Help hold nerve fibers together. They produce the fatty myelin sheath that envelops nerve fibers located in the brain & spinal cord. The myelin sheath affects nerve conduction speed.

Saltory conduction -

If the traveling impulse encounters a section of membrane covered with insulating myelin, it simply "jumps" around the myelin to the next gap in the myelin sheath. This type of impulse travel is much faster than is possible in nonmyelinated sections.

Reticular formation -

In the brainstem, small bits of gray matter mix closely & intricately with white matter to form the "it". In the spinal cord, gray & white matter do not intermingle. Gray matter forms the interior core of the spinal cord, & white matter surrounds it

Also known as Central connecting neurons

Interneurons

Hypothalamus -

Located below the thalamus. The posterior pituitary gland , the stalk that attaches it to the under surface of the brain, & areas of gray matter located in the side walls of a fluid-filled space called the third ventricle are extensions of the "it"

Also known as effernt neurons

Motor neurons

The most common primary diseases of the CNS is a myelin disorder called _______

Multiple sclerosis (MS)

The ___________ affects nerve conduction speed

Myelin sheath

Organization of the Nervous system Peripheral nervous system :

Nerves that extend to the outlying parts of the body

Cells of the nervous system ____________ is the major component of the nervous system

Nervous tissue

Nodes of Ranvier are gaps between adjacent Schwann cells. The outer wrapped layer of a Schwann cell is called the...

Neurilemma

Cells of the nervous system Two types of cell s are found in the nervous system :

Neurons & Glia

Oligodendrocyte can form part of the myelin sheath around several axons -BUT schwann cels wrap around ____________ axon

Only one

The simplest kind of reflex arc is a two-neuron arc because it consists of two types of neurons :

Sensory & motor neurons

Also known as afferent neurons

Sensory neurons

Three-neuron arcs are the next simplest kind of arcs after two-neuron arcs. They consists of all 3 kinds of neurons :

Sensory, interneurons & motor neurons

Endocrine system transmits info _________ by chemicals secreted by ducted glands into the blood stream & then circulates to other parts of the body

Slowly

The nerve impulse ________ at the synapse, chemical signals are sent across the gap & then a new impulse continues along the dendrites, cell body, & axon of the motor neuron. The motor neuron axon forms a synapse with a structure called an effector, an organ that puts nerve signals "into effect". Effectors are usually muscles or glands & muscle contractions & gland secretions are the kind of reflexes operated by these effectors

Stops

Cells of the nervous system Glia supports....

Supports neurons

Organization of the Nervous system Central nervous system :

The brain & the spinal cord

Brainstem -

The lowest part of "it" is the medulla oblongata. Immediately above the medulla lies the pons & above that the midbrain. Together these three structures are called the "it"

Neuron pathways -

The routes traveled by nerve impulses

Reflex arc are like one way streets :

They allow impulse conduction in only one direction

Reflex arcs are like one-way streets :

They allow impulse conduction in only one direction.

Organization of the Nervous system Autonomic nervous system :

Toomatic or involuntary functions (heart rate, stomach contractions, intestines, & secretions of chemical compounds by glands)

The simplest kind of reflex arc is a _________ arc because it consists of two types of neurons : Sensory & Motor neurons

Two-neuron

Bundles of axons are called tracts, also are myelinated & thus form ___________ of the brain & spinal cord

White matter

A synaptic knob is -

a tiny bulge at the end of a terminal branch of a presynaptic neuron's axon.

...other well known neurotransmitters include, nonrepinephrine, dopamine, & serotonin. They belong to a group of compounds called______, which plays a role in sleep, motor function, mood, & pleasure recognition

amines

Some neurons in the hypothalamus function in a surprising way; they make the hormones that the posterior pituitary gland secretes into the blood. Because of these hormones (called _______________) affects the volume of urine excreted, the hypothalamus plays an essential role in maintaining the body's water balance

antidiuretic hormone or ADH

Schawnn cells

are glial cells that also form myelin sheaths, but only do so in the peripheral nervous system (PNS)

Receptors -

are the beginning of dendrits of sensory neurons. They are often located far from the spinal cord (examples : in tendons, skin, mucous membranes)

Nerve impulses do not continually race along every nerve cells surface. They 1st have to be initiated by a stimulus, a change in the neuron's environment, pressure, temperature, & _____________ are the usual stimuli

chemical changes

In three-neuron reflexes, the end of the sensory neuron's axon synapses 1st with an interneuron before ________________ are sent across a second synapse resulting in conduction through the motor neuron

chemical signals

Cells of the nervous system Neurons conduct....

conduct impulses

Nerve impulses do not.....

continually race along every nerve cells surface. They 1st have to be initiated by a stimulus, a change in the neuron's environment, pressure, temperature, & chemical changes are the usual stimuli.

The cerebellum may assist the cerebrum & other parts of the brain, perhaps having an overall __________ for the whole brain

coordinating function

In the spinal cord, gray & white matter__________

do not intermingle

...other well known neurotransmitters include, nonrepinephrine, __________, & serotonin. They belong to a group of compounds called amines, which may plays a role in sleep, motor function, mood, & pleasure recognition

dopamine

The axon of the sensory neuron travels from the cell body in the ______ _______ ganglion & ends near the dendrites of another neuron located in the gray matter of the spinal cord

dorsal root

The nerve impulse stops at the synapse, chemical signals are sent across the gap & then a new impulse continues along the dendrites, cell body, & axon of the motor neuron. The motor neuron axon forms a synapse with a structure called an ________, an organ that puts nerve signals "into effect". Effectors are usually muscles or glands & muscle contractions & gland secretions are the kind of reflexes operated by these effectors

effector

Two morphinelike neurotransmitters called ________ & ______ are released at various spinal cord & brain synapses in the pain conduction pathway. These neurotransmitters inhibit conduction of pain impulses. They are natural painkillers

endorphins, enkephalins

Each axon in a nerve is surrounded by a thin wrapping of fibrous connective tissue called endoneurium . Groups of these wrapped axons are called fascicles. Each fascicles is surrounded by a thin, fibrous perineurium. A tough fibrous sheath called ____________ covers the whole nerve

epineurium

It is important to know that there are NO neurilemma in the CNS, because the neurilemma plays an essential role in the regeneration of cut and injured axons. Therefore, the potential for regeneration of damaged axons in the brain &b spinal cord is _______ than it is in the PNS

far less

One function of ___________ is to hold the functioning neurons together & protect them

glia cells

Glia in Greek means..

glue

Brain & spinal tissue composed of cell bodies & unmyelinated axons & dendrites is called...

gray matter

Measured by size, it is one of the least significant parts of the brain, but measured by its contribution to ______________, it is one of the most important brain structure

healthy survival

Each dorsal root ganglion contains ______ of sensory neuron cell bodies

hundreds

Hypothalamus exerts major control over virtually all ____________. Among the vital functions that it helps to control are the heartbeat, constriction & dilation of blood vessels & contractions of the stomach & intestines

internal organs

Some reflexes involve three rather than two neurons. In these complex types of responses, an ____ addition to a sensory & a motor neuron, is involved.

interneuron

Gray matter forms the H- shaped inner core of the spinal cord. Because of the presence of an.....

interneuron, three-neuron reflex arcs have two synapse. However, a two-neuron reflex arc has only a sensory neuron & a motor neuron with one synapse between them

Ganglion -

is a group of nerve cell bodies located in the PNS

Nerve impulse -

is a self-propagating wave of electrical disturbance that travels along the surface of a neuron's plasma membrane. (visualize this as a tiny spark sizzling its way along a fuse)

Medulla oblongata -

is an enlarged, upward extension of the spinal cord. It lies just inside the cranial cavity, above the large hole in the occipital bone called the foramen magnum

Cerebellum -

is the second largest part o the human brain. It lies under the occipital lobe of the cerebrum. In the "it" folded gray matter composes the thin outer layer & forms a large surface area of nervous connections that allow for a huge amount of information processing. White matter tracts form most of the interior.

Nerve signals If all impulse conduction ceases,.....

life itself ceases

arbor vitae literally means

living tree

Neuron structure Cell body -

main part of a neuron

The brain is protected by the skull, the spinal cord is surrounded in the spinal cavity by the vertebral column. In addition, the brain & spinal cord are also protected by three membranes called...

meninges

In the brain stem, small bits of gray matter _______& intricately with white matter to form reticular formation

mix closely

All three parts of the brainstem functions as two-way conduction paths. Sensory fibers conduct impulses up from the spinal cord to other parts of the brain, & ___________ conduct impulses down from the brain to the spinal cord

motor fibers

Hormones are the other kind of signal the body can use to send information with, however, this method is ___________ than nerve signals. They can move from one body part to another via blood circulation.

much slower

The nerve impulse stops at the synapse, chemical signals are sent across the gap & then a new impulse continues along the dendrites, cell body, & axon of the motor neuron. The motor neuron axon forms a synapse with a structure called an effector, an organ that puts nerve signals "into effect". Effectors are usually muscles or glands & ________ & ________ are the kind of reflexes operated by these effectors

muscle contractions & gland secretions

The nerve impulse stops at the synapse, chemical signals are sent across the gap & then a new impulse continues along the dendrites, cell body, & axon of the motor neuron. The motor neuron axon forms a synapse with a structure called an effector, an organ that puts nerve signals "into effect". Effectors are usually __________ or _________ & muscle contraction & glands secretions are the kind of reflexes operated by these effectors

muscles or glands

Many diseases are associated with disorders of the oligodendrocytes . Because these glial cells are involved in myelin formation, these diseases are called _______

myelin disorders

Bundles of axons are called tracts, also are ______ & thus form white matter of the brain & spinal cord (because myelin is white peripheral nerves often look white)

myelinated

Neurons with myelin-wrapped axons are called ...

myelinated fibers

reticular means

netlike

When a nerve impulse arrives at the synaptic knob, _____________ are released from vesicles into the synaptic cleft.

neurotransmitter molecules

...other well known neurotransmitters include, _________, dopamine, & serotonin. They belong to a group of compounds called amines, which plays a role in sleep, motor function , mood, & pleasure recognition

nonrepinephrine

The cerebellum plays a essential part in the production of ....

normal movements

Each axon in a nerve is surrounded by a thin wrapping of fibrous connective tissue called endoneurium . Groups of these wrapped axons are called fascicles. Each fascicles is surrounded by a thin, fibrous _________. A tough fibrous sheath called epineurium covers the whole nerve

perineurium

Microglia surround the microbes, draw them into cytoplasm, & digest them. (What is this an example of?)

phagocytosis

By definition, a synapse is the place where impul;ses are transmitted from one neuron, called the presynaptic neuron, to another neuron called the ______ neuron.

postsynaptic

Nerve impulses do not continually race along every nerve cells surface. They 1st have to be initiated by a stimulus, a change in the neuron's environment, __________, temperature, & chemical changes are the usual stimuli

pressure

By definition, a synapse is the place where impulses are transmitted from one neuron, called the ____________ neuron, to another neuron called the postsynaptic neuron.

presynaptic

Nerve signals Only neurons can provide the _____________ between cells that is necessary for maintaining life

rapid communication

Nervous system transmits info________ by nerve impulses

rapidly

impules conduction normally starts in ...

receptors

It is important to know that there are NO neurilemma in the CNS, because the neurilemma plays an essential role in the _________ of cut and injured axons. Therefore, the potential for regeneration of damaged axons in the brain &b spinal cord is far less than it is in the PNS

regeneration

Glial cells perform many different functions, one including the __________ of neuron function

regulation

This type of impulse travel is much faster than is possible in nonmyelinated sections

saltory conduction

All three parts of the brainstem functions as two-way conduction paths. ______________ conduct impulses up from the spinal cord to other parts of the brain, & motor fibers conduct impulses down from the brain to the spinal cord

sensory fibers

...other well known neurotransmitters include , nonrepinephrine, dopamine, & __________. They belong to a group of compounds called amines, which plays a role in sleep, motor function, mood, & pleasure recognition

serotonin

Diencephalon -

small but important part of the brain located between the mid-brain below & the cerebrum above. It consist of three major parts : Hypothalamus, thalamus, & pineal gland

The word astrocyte means

star cell

A microscopic separates the axon ending of one neuron from the dendrites of another neuron. This gap serves as a junction between nerve cells called a ....

synapse

Three structures make up a typical synapse: a synaptic knob, a _________, & the plasma membrane of a postsynaptic neuron.

synaptic cleft

Three structures make up a typical synapse : a ______________, a synaptic cleft, & the plasma membrane of a post synaptic neuron.

synaptic knob

Nerve impulses do not continually race along every nerve cells surface. They 1st have to be initiated by a stimulus, a change in the neuron's environment, pressure, ____________, & chemical changes are the usual stimuli

temperature

Receptors are....

the beginning of dendrites of sensory neurons. They are often located far from the spinal cord ( i.e. in tendons, skin, & mucous membranes)

Produces smooth coordinated movements, maintains equilibrium, & sustains normal posture

the cerebellum

All interneurons lie entirely within ___________ of the brain or spinal cord

the gray matter

Three structures make up a typical synapse : a synaptic knob, a synaptic cleft, & __________ of a post synaptic neuron

the plasma membrane

Synaptic cleft -

the space between a synaptic knob & the plasma membrane of a postsynaptic neuron -it is an incredibly narrow space- only about two-millionths of a centimeter in width. "It" is filled w/ extracellular matrix that holds the synaptic structure in place

Neuron structure Each neuron consist of _______ parts.

three

Bundles of axons are called _________

tracts

The nervous system and the endocrine system both ...

transmit info throughout the body

Each synaptic knob contains many small sacs of

vesicles. Each vesicle contains a very small quantity of a chemical compound called a neurotransmitter

Many important reflex centers lie in the brainstem. The cardiac, respitory, & vasomotor centers ( collectively called the _________), for example are located in the medulla

vital centers

Some neurons in the hypothalamus function in a surprising way; they make the hormones that the posterior pituitary gland secretes into the blood. Because of these hormones (called antidiuretic hormone, or ADH) affects the volume of urine excreted, the hypothalamus plays an essential role in maintaining the body's water balance

water balance