EXAM 2: Nerve tissue & glial cells

Oligodendrocytes

- Myelinate axons - Multiple Sclerosis- degenaration of oligodendrocytes - Have processes that form myelin sheats around CNS nerve fibers

What are some functions of Astrocytes?

- Secrete growth factors to support neurons -Can modulate synaptic activity - Replicate (source of most CNS tumors) - Buffer pH and ioninc environments in extracellular space - Highly branches, join together by end feet to separates neural tissue from other tissue - forms part of blood brain barior

Microglial cells

-Defensice cells in the CNS (immune cells) -Phagocytic scavengers -Secrete neurotoxic substances

Do sensory (afferent) nerves conduct impulses away from or towards the CNS? What about motor (efferent) nerves?

-Sensory (afferent) nerves conduct impulses only toward the CNS. - Motor (efferent) nerves carry impulses only away from the CNS. Nerves carrying both sensory (afferent) and motor (efferent) fibers are called mixed nerves. Most nerves of the body, including all spinal nerves, are mixed nerves.

Explain how Schwann cells myelinate (enclosed in a myelin sheath) nerve fibers (axons) in the peripheral nervous system?

1. A Schawann cell envelops an axon 2. The Schawann cell then rotates around the axon, wrapping its plasma membrane loosely around it in successive layers 3. The Schawann cell cytoplasm if forced from between the membranes. The tights membrane wrappings surrounding the axon form the myelin sheath

What are the two types of processes in a neuron? What are their functions?

1. Dendrites - receptors regions that bear receptors for nuerotrasmitters released by the axon terminals of other neurons 2. Axons- form the impulse generating & conductions region of the neuron

What two cell types is nervous tissue made up of?

1. Neurons 2. Neuroglia (glial cells)

What are the cells in the PNS nervous system glial cells called?

1. Satellite cell- analogous to astrocytes in CNS - surround cells in ganglia and regulate extracellular ioninc environment 2. Shwann cells- myelinate peripheral nerve Macrophages- immune cells

Which of the following statements is true? A) Neurolemmocytes form a myelin sheath around axons in the peripheral nervous system, and oligodendrocytes form a myelin sheath around axons in the central nervous system. B) Astrocytes form a myelin sheath around axons in both the peripheral nervous system and the central nervous system. C)Schwann cells are the same as oligodendrocytes, and they both act as phagocytic cells to provide protection for the neuron.

A) Neurolemmocytes form a myelin sheath around axons in the peripheral nervous system, and oligodendrocytes form a myelin sheath around axons in the central nervous system.

Identify the important anatomical features of a neuron on an appropriate image.

Axon- A threadlike extension of a neuron that carries nerve impulses away from the cell body. Dendrites- a short branched extension of a nerve cell, where impulses received from other cells at synapses are transmitted to the cell body. Myelin sheats- a dielectric material that forms a layer Neurotransmission- communication between neurons

What is the white matter of the nervous system made up of?

Axons

List the six types of neuroglial, and indicate where each is found in the nervous system.

CNS 1. Astrocytes 2. Oligodendrocytes 3. Microglia PNS 1. Satellite cells 2. Schwann cells 3. Macrophages

What does the CNS consist of? PNS?

CNS consist of brain & spinal cord PNS, which includes all the nervous elements located outside the central nervous system. Consist of: - spinal nerves to and from spinal cord -cranial nerves to from brain

What cells are found in the CNS neuroglia (glial cells)? In the PNS?

CNS- astrocytes, oligodendrocytes, microglia PNS- satellite cells, schawaan cells, macrophages

In the CNS, bundles of axons are called? In the PNS, bundles of axons are called?

CNS: tracts PNS: nerves

What two primary divisions make up the nervous system?

Central nervous system (CNS) Peripheral nervous system (PNS)

State the function of myelin sheaths-

Main functions include protecting the nerves from other electrical impulses, and speeding the time it takes for a nerve to travel an axon.

What's the function of glial cells?

Maintain micro-environment & provide neurons w/ structural support

Structure of a motor neuron

Motor neurons are neurons located in the central nervous system, and they project their axons outside of the CNS to directly or indirectly control muscles. The structure of motor neurons is multipolar, meaning each cell contains a single axon and multiple dendrites.

What are some functional differences between neurons & neuroglia (glial cells)?

Neurons transmit messages from one part of the body to another in the form of nerve impulses. Neuroglia (glial cells) serve primarily to support and protect the neurons.

Ependymal cell

One of the 4 types of glial cells in the CNS line cerebrospinal fluid-filled cavities

There are two types of glial cells found in the peripheral nervous system. Which of the following is found in the peripheral nervous system?

Schwann Cells

What two functional divisions does the peripheral nervous system consist of?

Sensory (afferent) division - Convey impulses from skin, skeletal muscles, and joints to CNS - Visceral sensory fibers: convey impulses from visceral organs to CNS Motor (efferent) division - Transmits impulses from CNS to effector organs. - Muscles & glands - Two divisions: Somatic nervous system and autonomic nervous system

Classify neurons structurally and functionally. Pg. 256

Structurally: Unipolar - one very short process, which divides into peripheral and central processes, extends from the cell body. Bipolar - two processes attached to the cell body. (found only Multipolar- neurons have many processes that issue from the cell body. Functionally: Sensory (afferent) - neurons carrying impulses from sensory receptors in the internal organs(viscera), skin, skeletal muscles, joints, or special sensory. Motor (efferent) - neurons carrying impulses from the CNS to the viscera and/or body muscles & glands Interneurons- connect sensory & motor neurons, their cell bodies are always located within the CNS, and they are multipolar neurons structurally.

Explain how a nerve impulse is transmitted from one neuron to another?

Within a neuron an impulse travels from a dendritre to the cell body and then moves along the axon to the end. There the impulse encounters a synapse separating it from a dendrite or cell body of another neuron. After they are released, some neurotransmitters are decomposed by enzymes in the synaptic cleft.

Impulses that are going toward the CNS are called __________ and impulses going away from the CNS are called __________.

afferent; efferent

The myelin sheath (formed by neurolemmocytes) wrap around the __________ of a neuron to provide protection and insulation.

axon

Which part of the neuron is involved in sending an impulse to the synapse area or to an effector?

axon

Is a motor neuron in the CNS or PNS?

both

These branching neuron processes serve as receptive regions and transmit electrical signal toward the cell body. They are: a. axons b. collaterals c. dendrites d. neuroglia

c . dendrites

Neuroglia of the peripheral nervous system include: a. ependymal cells & satellite cells b. oligodendrocytes & astrocytes c. satellite cells & Schwann cells

c . satellite & schwann cells

Neurons can be classified according to structure. ______ neurons have many processes that issue from the cell body. a. bipolar b. multipolar c. unipolar

c. multipolar

What is the name of the glial cells that act as phagocytes to aid in protecting CNS neurons?

microglia

The axons of some neurons in the CNS are protected by glial cells that form a myelin sheath around the axons. These glial cells are called __________.

oligodendrocytes

Axons running through the central nervous system from ____ of white matter a. tracts b. nerves

tracts