Chapter 14: Nervous tissue

How are synapses classified?

- Based on function: Electrical, chemical - Based on location: axodendritic, axosomatic, axoaxonic

What are functions of the nervous system?

- Processing and evaluating information - Collecting information - Responding to information

Statements regarding astrocytes

-Astrocytes are the most abundant glial cells in the CNS -Astrocytes help form the blood-brain barrier by wrapping around capillaries in the brain -Astrocytes assist in the neuronal fetal development by secreting chemicals that regulate neuronal connections

Statements that apply to myelinated axons

-Myelinated axons have faster nerve impulse conduction that unmyelinated axons -In myelinated axons, the nerve impulse "jump" from node to node, and do not have to travel the entire length of the axon membrane -Myelinated axons use less energy than unmyelinated axons

Which glial cells form a myelin sheath around axons?

-Oligodendrocyte -Neurolemmocyte

What structures are involved in synapses?

-Swelling of axons at their end branches are called synaptic knobs -Space between the presynaptic and postsynaptic cells is the synaptic cleft

Check all the factors that increase the chance of a damaged axon being able to regenerate

-The damaged axon is in the PNS -Some neurilemma remains -The distance between the site of the damaged axon and the effector organ is relatively short

Statements regarding the sensory and motor nervous systems

-The sensory nervous system contains both PNS & CNS components -The somatic nervous system component of the motor nervous system conducts impulses from the CNS to skeletal muscle -The motor nervous system contains both CNS & PNS components

Statements of chemical synapses

-chemical synapses are the most numerous type of synapse in the human body -chemical synapses are unidirectional (one way)

How and when can damaged neurons be regenerated in the PNS?

A damaged axon can be regenerated if the cell body remains intact and a certain amount of neurilemma remains. The success depends upon the amount of damage & the distance between the site of the damaged axon

Define microglial cells

Act as phagocytes in nervous tissue

What does the nervous system include?

All the nervous tissues in the body

What are the two basic categories of neural tube defects?

Anencephaly-complete absence of a brain as well as the bones that make up the cranium Spina bifida-a caudal portion of the neural tube fails to close, often in the lumbar or sacral region.

Which nervous system innervates cardiac and smooth muscle?

Autonomic motor

A student observes the structure of a neuron under the microscope. The cell has a central stoma with two cell process emerging, one in each side. One cell process receives input from another cell while the second cell process is responsible for generating output. What is the structural classification of this neuron?

Bipolar

Nerve bundle anatomy and organization

Bundle of many parallel axons organized in 3 layers: endoneurium around a single axon, a perineurim around a fascicle, and an epineurium around all of the fascicles.

When does the embryo have an official "neural tube"?

By the end of the 3rd week when the neural folds have met and fused at the midline

Which nervous system consists of the brain and spinal cord?

Central nervous system

Which synapse utilizes neurotransmitters?

Chemical synapse

What's the anatomy of a neuron?

Contains a cell body and processes like dendrites and an axon

The nerve impulse conduction along an unmyelinated axon is called___________conduction

Continuous

What is the PNS system composed of?

Cranial, spinal, and ganglia

When does nervous tissue development begin?

During the 3rd week

Which synapse requires gap junctions?

Electrical synapse

What are the different ways synapses communicate?

Electrically when a flow of ions pass from the presynaptic cell to the postsynaptic cell through gap junctions and chemically when a nerve impulse causes the release of a chemical neurotransmitter from the presynaptic cell

What are neurons and what special characteristics do they possess?

Excitable cells that transmit nerve impulses & glial cells completely surround neurons & protect them

T/F Ganglia are clusters of neuron cell bodies located within the CNS

False

T/F In the CNS, oligodendrocytes secrete nerve growth factor to stimulate the regeneration of damaged axons.

False

T/F Nerve impulses relaying pain would most likely use saltatory conduction

False

T/F Neurons are unique in that they do not require glucose or oxygen to function

False

T/F One function of the nervous system is to always respond to sensory input

False

Increased intake of which vitamin greatly reduces the risk of one category of NTD?

Folic acid (B vitamin)

Define astrocytes

Help form the blood brain barrier and regulate tissue fluid composition

Define ependymal cells

Lines CNS cavity and produce cerebrospinal fluid

A nerve contains neurons sending both afferent & efferent information is classified as

Mixed

Define oligodendrocytes

Myelinate axons in the CNS

Which cells are responsible for myelination in the CNS and PNS as well as the difference in conduction between myelinated and unmyelinated axons and the terms for HOW they conduct nerve impulses?

Oligodendrocytes in the CNS. Neurolemmocytes in the PNS. Myelin sheath insulates the axonal membrane resulting in faster nerve impulse conduction unlike unmyelinated axons that are not ensheathed by neurolemmocytes.

Which nervous system includes cranial and spinal nerves?

Peripheral nervous systwm

Another term for the__________system is the afferent nervous system

Sensory

What is the functional organization of of the sensory and motor nervous system?

Sensory nervous system conveys sensory information to the CNS. Motor nervous system conducts motor commands to muscles and glands.

The________________nervous system transmits information from receptors to the CNS, while the____________nervous system transmits information from the CNS to the rest of the body

Sensory; motor

Define glial cells

Small cells capable of mitosis. Protect, support, and form the framework for all the nervous tissue

The___________sensory system includes sensory information such as touch, pain, pressure, vibrations , and the general senses

Somatic

Which nervous system innervates skeletal muscles?

Somatic motor

Which nervous system receives information from skin?

Somatic sensory

Anatomy of a synapse

Specialized junction between two excitable cells where a nerve impulse is transmitted

Define satellite cells

Support neuron cell bodies in ganglia and neurlemmocytes myelinate axons in the PNS

What is the main activity of axons?

To make contact with other neurons, muscle cells, or gland cells

T/F A regenerating axon in the PNS is guided by the regeneration tube, and grows at a rate of about 5 mm per day

True

How and when can damaged neurons be regenerated in the CNS?

Very limited to regeneration because oligodendrocytes do not release a growth factor. The axons are very crowded & astrocytes & connective tissue covering may form scar tissues that obstructs axon regrowth

The autonomic nervous system is also known as the_________nervous system because it involves involuntary actions in the smooth muscles, cardiac muscles, and glands

Visceral

Which nervous system receives information from the intestines?

Visceral sensory

What effects the speed at which they convey it?

Whether the axon is myelinated or not.

How can you classify a neuron?

You can classify whether the neuron is unipolar, bipolar, or multipolar by the number of processes attached to the cell body and functionally as sensory, motor, or interneurons

Put the events of axon regeneration into the correct order.

a. Peripheral nerve injury results in the severing of an axon b. The proximal part of the axon seals off and swells; the distal part degenerates. c. Glial cells that myelinate the axon form a regeneration tube d. Axon regenerates and myelination occurs. e. Reinnervation of the skeletal muscle fibers by the axon.

When our esophagus contracts involuntarily to move a bolus of food down, it is acting based on which subdivision of the motor nervous system?

autonomic

Which of the following cells secrete nerve growth factors that stimulate outgrowth of severed axons?

neurolemmocytes

Myelin sheaths mainly consist of which part of the glial cells that form them?

plasma membranes

The optic nerve is composed of axons of neurons that send afferent information from the retina of the eye to the brain. Which of the following describes the functional classification of this nerve?

sensory

A typical synapse in the CNS consists of a presynaptic neuron and a postsynaptic neuron, separated by a narrow space called the

synaptic cleft