Nervous Tissue

Most neurotransmitters synthesized in cell body and are transported to axon terminal at a rate of ___________.

1 - 400 mm/day

PNS can repair damaged dendrites or axons if:

1. Neuron cell body remains intact 2. Schwann cells remain active and form a tube 3. Scar tissue does not form too rapidly

What do schwann cells do?

1. encircle PNS axons 2. speeds neurotransmission

What are some functions of astrocytes?

1. monitor neuronal activity and signal blood vessels to constrict/dilate to regulate blood flow providing oxygen and nutrient supply 2. convert blood glucose to lactate and supply it to neurons 3. control chemical environment around neurons 4. provide a supportive framework for nervous tissue - induce synapse formation 5. form scar tissue when neurons are damaged - sclerosis

Regeneration of nerve axons includes...

1. sprouting of new dendrites 2. synthesis of new proteins 3. changes in synaptic contacts with other neurons

______ _________ secrete neurotransmitters that either excite or inhibit other neurons or effector cells.

Axon terminals

The cell body contains:

a nucleus, lysosomes, mitochondria, a Golgi complex, cytoplasmic inclusions such as lipofuscin, chromatophilic substances, and neurofibrils

Excitability

ability to respond to stimuli

What is white matter composed of?

aggregations of myelinated processes

The nervous system is responsible for...

all of our behaviors, memories, and movements

Reflexes include glandular secretion and contractions of which types of muscle? Also some learned responses termed ___________ ________.

all three types; conditioned reflexes

The _____ conducts nerve impulses from the neuron to the dendrites or cell body of another neuron or to an effector organ of the body (muscle or gland)

axon

The central nervous system (CNS) consists of...

brain and spinal cord

The stretch reflex operates as a feedback mechanism to...

control muscle length by causing muscle contraction

The tendon reflex operates as a feedback mechanism to...

control muscle tension by causing muscle relaxation when muscle force becomes too extreme

Axons of the PNS are surrounded by Schwann cells, which are covered by _______________

endoneurium

Ependymal cells form what?

epithelial membrane lining cerebral ventricles & central canal of cord

Nerve cells, or neurons, have three fundamental physiological properties that enable them to communicate with other cells.

excitability (irritability), conductivity, secretion

All somatic spinal reflexes...

exhibit reciprocal innervation

Each neuron has a single axon that arises from the axon ________ and generates and conducts nerve impulses away from the cell body to the axon __________.

hillock; terminals

Where are bipolar neurons found?

in retina, inner ear & olfactory cells

a. They are called motor neurons because... and efferent because...

most of them lead to muscle cells; they carry signals away from the CNS

A simple two-neuron or monosynaptic reflex arc contains...

one sensory neuron and one motor neuron (no interneuron)

Sensory neurons begin in almost every _______ of the body and end in the ___

organ; CNS

What do neurons metabolically require?

oxygen and glucose

A _______ is a fast, predictable, automatic response to changes in the environment that helps to maintain homeostasis.

reflex

Amitotic

relating to or denoting the division of a cell nucleus into two parts by constriction without the involvement of a mitotic apparatus

Most of the simple reflex arc in the body contain a...

single interneuron

The ________ reflex is ipsilateral and is important in maintaining muscle tone and muscle coordination during exercise.

stretch

What is an example of a simple reflex arc?

stretch reflex, such as the patellar reflex

The ____________ division tends to arouse the body for action. For example, through accelerating the heartbeat and increasing respiratory airflow and inhibiting digestion. Fight or Flight

sympathetic

The site of functional contact between two neurons or between a neuron and an effector cell is called a _________

synapse

The _______ reflex is ipsilateral and prevents damage to muscles and tendons as a result of stretching.

tendon

Where are receptors located?

terminal end of the peripheral process of a sensory neuron

The __________ ________ division (____________ nervous system) carries signals to glands, cardiac muscle, and smooth muscle over which we have no voluntary control; the responses are termed visceral reflexes.

visceral motor (autonomic)

The _________ _________ division carries signals from viscera of the thoracic and abdominal cavities.

visceral sensory

What is the function of microglia?

wander through CNS probing for cellular debris or other problems - monitor health and perform defense functions for neurons

Secretion

when electrical signal reaches end of nerve fiber, a chemical neurotransmitter is secreted that crosses the gap and stimulates the next cell

Axons within the CNS that have myelin sheaths are called ______ _______, while those without are called gray matter.

white matter

Bipolar

one main dendrite and one axon

About __% of neurons in the human body are interneurons.

90%

What is a myelin sheath?

A multilayered lipid and protein syncovering sheath that electrically insulates the axon and increases the speed of nerve impulse conduction

Interneurons (association neurons) lie entirely within the ___.

CNS

___ no repairs are possible

CNS

Most neuron cell bodies are located within the ___, however, some clusters of cell bodies (ganglia) lie along the nerves of the ___.

CNS; PNS

_______________ ___________ (Nissl bodies) are an orderly arrangement of rough ER.

Chromatophilic substances

__________ are cell processes that are the receptive regions of the cell and provide surface area for receiving signals from other neurons.

Dendrites

__________ is a tough connective tissue surrounding the entire nerve

Epineurium

Clusters of cell bodies include: a. _________ in the PNS b. _________ in the CNS

Ganglia; Nuclei

___________ is a pigment created by lysosomes when they digest worn out organelles, and it accumulates in neurons with age.

Lipofuscin

_________ are bundles of axons in the PNS

Nerves

___________ are intermediate filaments that form the cytoskeleton.

Neurofibrils

________ (____) are specialized tissue cells that support neurons, attach neurons to blood vessels, produce the myelin sheath around axons, and carry out phagocytosis.

Neuroglia (glia)

Neuroglia of the ___ completely surround axons and cell bodies

PNS

____________ is connective tissue surrounding nerve fascicles.

Perineurium

Babinski Reflex

Reflex in which a newborn fans out the toes when the sole of the foot is touched

PNS: 2 cell types

Schwann Cells and Satellite Cells

What are oligodendrocytes analogous to in the PNS?

Schwann cells

What is associated with the axon?

Schwann cells, Oligodendrites and a myelin sheath

Which type of neurons analyze sensory information?

association/interneurons

What has the most diverse functions of any glia?

astrocytes

What is the most abundant glia?

astrocytes -- constitute over 90% of the tissue in some brain areas

How is the blood brain barrier formed?

astrocytes cover blood capillaries

CNS: 4 cell types

astrocytes, oligodendrocytes, microglia, ependymal

How does the neurolemma aid in regeneration of an injured axon?

by forming a regeneration tube that guides and stimulates regrowth of the axon

How do reflexes help maintain homeostasis?

by permitting the body to make exceedingly rapid adjustments to homeostatic imbalances

Most neurons, or nerve cells, consist of a _____ _____ (_____), and neuron processes that extend from them: many _________, and usually a single _____.

cell body (soma); dendrites; axon

What are the subdivisions of the nervous system?

central nervous system and peripheral nervous system

In two regions of the brain, ____________ and ______________, there is an additional layer of gray matter located superficially, the cortex

cerebrum and cerebellum

What are ependymal cells?

ciliated cells that (along with capillaries in brain) help circulate cerebrospinal fluid (CSF)

Ependymal cells resemble what? But...

cuboidal epithelium lining internal cavities of the brain and spinal cord; no basement membrane and have rootlike processes that penetrate the underlying tissues

The _________ are the receiving or input portions of a neuron.

dendrites

Most axons branch extensively at their ______ end

distal

Satellite Cells are...

flat cells that surround CBs of neurons in PNS ganglia

How long do neurons function optimally?

for a lifetime

Each oligodendrocyte...

forms a myelin sheath around more than one axon in CNS

A _________ is a knot-like swelling in a nerve where the cell bodies of neurons are concentrated.

ganglion

Cells can divide - rapid mitosis in tumor formation (_______).

gliomas

in the brain a thin outer shell of _____ matter covers the cerebral hemispheres

gray

Where do synapses occur?

gray matter

Where does integration for spinal reflexes occur?

gray matter

In the spinal cord, ____ matter forms an H-shaped inner core, surrounded by _______ matter

gray; white

After 12-18 months of age, if the Babinski reflex is still present

is indicative of abnormalities in the motor control pathways leading from the cerebral cortex and is widely used as a diagnostic aid in disorders of the central nervous system

What is the problem with the blood brain barrier?

it can't differentiate between harmful toxins, and life-saving chemicals

The _______ (_________) division carries signals from the CNS to gland and muscle cells that carry out the body's responses; cells and organs that respond are called effectors.

motor (efferent)

Which neurons respond to stimuli?

motor (efferent) neurons

What is the most common cell type in the CNS?

multipolar

Motor (efferent) neurons send signals predominantly to...

muscle and gland cells

Where are microglia found?

near blood vessels

A ______ is a bundle of nerve fibers (axons) wrapped in connective tissue.

nerve

What is gray matter composed of?

nerve cell bodies, dendrites, and axon terminals or bundles of unmyelinated axons and neuroglia

Groups of axons are bound into bundles called _________ _________

nerve fascicles

The peripheral nervous system (PNS) consists of...

nerves, ganglia, and sensory receptors

_________ and ________ are groups of axons in the PNS and CNS, respectively

nerves; tracts

The __________ __________, along with the ____________ ___________, helps to keep controlled conditions within limits that maintain health and helps to maintain homeostasis.

nervous system; endocrine system

The study of the nervous system is _____________

neurobiology

The myelin sheath has gaps called _______ along the axon.

neurofibril nodes/nodes of Ranvier

The outer nucleated cytoplasmic layer of the Schwann cell, which encloses the myelin sheath, is called the ____________ (_______ __ ________) and is found only around axons in the PNS.

neurolemma (sheath of Schwann)

The branch of medical science that deals with the normal functioning and disorders of the nervous system is called __________

neurology

Explain the difference between a neuron, nerve fiber, and nerve.

neuron = nerve cell nerve fiber = long axon nerve = collection of axons in the PNS

Nerve tissue contains two types of cells:

neurons & glial cells

Which cells are damaged in multiple sclerosis?

olgiodendrocytes

Myelin sheaths are produced by ____________ in the CNS and ____________ in the PNS

oligodendrocytes; Schwann cells

A reflex arc is the simplest type of pathway; pathways are specific neuronal circuits and thus include at least how many synapses?

one

Unipolar

one axon only extending from the cell body that is associated with receptors at the distal end

Some receptors are themselves neurons, such as those for... In senses such as... the receptor is a separate cell that communicates directly with a sensory neuron.

pain and smell; taste and hearing

The ________________ division tends to have a calming effect. For example, slowing down the heartbeat and stimulating digestion. Rest and Digest.

parasympathetic

Withdrawal Reflex

prevents/limits tissue damage

Conductivity

produce electrical signals that are conducted to other cells

The _________ (________) division carries sensory signals from receptors to the CNS; this pathway informs the CNS of stimuli

sensory (afferent)

Which type of neurons sense changes in the internal and external environment?

sensory (afferent) neurons

Neurons fall into three functional classes based on the three major aspects of nervous system function.

sensory (afferent), interneurons (association), motor (efferent)

The PNS is functionally divided into...

sensory and motor divisions

Unipolar neurons are always...

sensory neurons

The nervous system carries out its coordinating task in three basic steps

sensory, integrative, and motor functions

Multipolar

several dendrites and one axon

What are microglia?

small macrophages that develop from white blood cells called monocytes

What can pass through the blood brain barrier?

small molecules like alcohol, caffeine, nicotine, oxygen, and glucose

The _________ ________ division carries signals to the skeletal muscles, producing muscular contractions that are under voluntary control as well as involuntary contractions called somatic reflexes.

somatic motor

The __________ ___________ division carries signals from receptors in the skin, muscles, bones, and joints

somatic sensory

If a withdrawal reflex is absent, or abnormal, the damage may be where?

somewhere along a particular conduction pathway

Reflexes may be _______ and _______ in location, and ________ or ____________ in function.

spinal/cranial; somatic/autonomic

What shape are astrocytes?

star shaped

The five functional components of a reflex arc are...

the receptor, sensory neuron, integrating center neuron, motor neuron, and effector

Somatic spinal reflexes include...

the stretch reflex, tendon reflex, flexor (withdrawal) reflex, and crossed extensor reflex

After damage to oligodendrocytes...

there is little regrowth

What is the integrative function of the nervous system?

to analyze the sensory information, store some aspects, and make decisions regarding appropriate behaviors

What is the motor function of the nervous system?

to respond to stimuli by initiating action -- the spinal cord and brain tissue commands to muscle and gland cells to carry out the response

What is the sensory function of the nervous system?

to sense changes in the internal and external environment through sensory receptors and transmit messages to the spinal cord and brain