Nerve Tissue and CNS

Question 1

What two body systems provide the regulation and control of all other body systems that is necessary for homeostasis? What is the basic mechanism of action used for each?

Answer 1

Nervous system – master controlling and communicating system of body. Quick and short lived with other neurons and effector cells.
Endocrine system – various glands that secrete messenger products (hormones) to circulate in blood and bind to receptors in a receptor cell. Better at regulatory processes with longer duration.

Question 2

What are the three basic functions of the nervous system?

Answer 2

sensory input – info gathered about changes occurring both inside and outside the body through sensory receptors
Integration – process in which the nervous system processes and interprets sensory input and decides what should be done at each movement
Motor output – activating effector organs (muscles and glands) to cause a response

Question 3

Identify the two major divisions of the nervous system.

Answer 3

Central nervous system and peripheral nervous system

Question 4

What was the anatomical components of each of these divisions?

Answer 4

CNS – brains and spinal cord that occupy dorsal cavity
PNS – nerves that extend from brains (cranial nerves) and spinal cord (spinal nerves), ganglia (collections of neuron cell bodies)

Question 5

Distinguish between cranial nerves and spinal nerves.

Answer 5

Spinal nerves carry impulses to and from the spinal cord. Cranial nerves carry impulses to and from the brain

Question 6

Distinguish between afferent and efferent functions of the PNS.

Answer 6

Afferent – axons convey impulses to CNS from sensory receptors and contain somatic (skeletal muscles, skin and joints) sensory fibers and visceral sensory fibers

Efferent – transmits impulses from CNS to effector organs (muscles and glands) that activate muscles to contract and glands to excrete

Question 7

What is the function of the somatic sensory neurons?

Answer 7

Convey impulses from skin, skeletal muscles, joints

Question 8

What is the function of the visceral sensory neurons?

Answer 8

Transmit impulses from visceral organs

Question 9

Why is the motor portion of the somatic nervous system called the voluntary nervous system?

Answer 9

Because the somatic nervous system allows us to consciously control our skeletal muscles

Question 10

Identify divisions of the ANS.

Answer 10

sympathetic division and parasympathetic division

Question 11

What division of the PNS is considered involuntary?

Answer 11

autonomic nervous system

Question 12

Where are the two basic cell types found in nervous tissue? Which of these basic cell types is most numerous?

Answer 12

Neurons and neuroglial cells. Glial cells are most numerous

Question 13

Name the four types of supporting cells of CNS

Answer 13

astrocyte, microligal ells, ependymal cells, oligodendrocytes

Question 14

describe astrocytes

Answer 14

most abundant and largest neuroglia

• • numerous radiating processes that cling to neurons and their synaptic endings
• • connected by gap junctions

Support and braces neurons and anchor them to their nutrient supply lines

• -guides formation of synapses
• -controls chemical environment around neurons: “mop up” leaked K+ ions and recapture and recycle released neurotransmitters
• • influences neuronal functioning for infor processing to brains

Question 15

Describe microglial cells

Answer 15

• important protective role because immune system cells have limited access to CNS
• -small and ovoid with relatively long thorny process that touch nearby nearby neurons
• -monitor neuron health and migrate to those injured
• -transforms into special type of macrophage that phagocytizes invading microorganisms or dead neurons that are present

Question 16

Describe ependymal cells.

Answer 16

• squamous to columnar
• lines central cavities of brain and spinal cord to form permeable barrier between cerebrospinal fluid in those cavities and fluid of cells in CNS to circulate it

Question 17

Describe oligodendrocytes

Answer 17

• branches but less processes than astrocytes
• lines up along thicker nerve fibers in the CNS and wrap their processes tightly around the fibers, producing an insulating cover called a myelin sheath

Question 18

Name the two types of supporting cells in PNS.

Answer 18

Schwann cells and satellite cells

Question 19

Describe satellite cells.

Answer 19

surrounds neuron cell bodies located in PNS.

–same function as astrocytes in PNS.

Question 20

Describe Schwann cells.

Answer 20

• aka neurolemmocytes
• surrounds all nerve fibers in the PNS
• functionally similar to oligodendrocytes in CNS, form myelin sheaths around thicker nerve fibers
• **vital to generating damaged peripheral nerve fibers

Question 21

What cell produces myelin the PNS? in CNS?

Answer 21

CNS: oligodendrocytes
PNS: Schwann cells

Question 22

What cell serves as a phagocyte in the CNS?

Answer 22

microglial cells

Question 23

What is the largest cell in the CNS? the most numerous?

Answer 23

astrocytes

Question 24

What glial cell participates in forming the blood-brain barrier?

Answer 24

ependymal cells

Question 25

Identify the special characteristics of neurons.

Answer 25

Extreme longevity (can last a lifetime)

Amitotic (as they assume roles in nervous system, they los ability to divide and CANNOT BE REPLACED IF DESTROYED) ** olfactory epithelium cells are exception

High metabolic rate (requires continuous and abundant supply of oxygen and glucose. Cannot survive more than a few minutes without oxygen

Question 26

Identify the three parts of a neuron.

Answer 26

cell body (soma), dendrite and axon

Question 27

What organelles are typically present in the neuron cell body? are noticeably absent?

Answer 27

all are normally present except

rough ER, Golgi apparatus

Question 28

What is the function of the neurofibrils?

Answer 28

bundles of intermediate filaments important in maintaining cell shape and integrity as a network throughout cell body

Question 29

What are Nissl bodies (sometimes called chromatophilic substance)? Why are they so prominent in the soma of neurons?

Answer 29

Neuron cell body’s protein most active and developed in body

• rough er that stains darkly with dyes as color pigment
• -lipofuscin called aging pigment because it occurs in neurons of elderly individuals

Question 30

Which neuron process conducts impulses toward the cell body? away from the cell body?

Answer 30

dendrites toward body

axon away from body

Question 31

What is the axon hillock?

Answer 31

conical shaped area of cell body that forms the initial region of an axon
–trigger zone where action potential is initated

Question 32

Where are the synaptic vesicles located

Answer 32

axons branch into axon collateral at the end, called terminal branches that have bulb-shaped synaptic knobs called axon terminals that contain synaptic vesicles

Question 33

What is axonal transport? Why is it important?

Answer 33

Means of moving molecules along the length of the axon or toward the cell body

Question 34

What are the two directions of axonal transport??

Answer 34

anterograde direction allows certain components to renew the axon plasma membrane and enzymes needed to synthesize certain NT

retrograde direction is important as a means for intracellular communication. Allows cell body to be advised of conditions at axon terminals and delivers to the cell body vesicles containing signal molecules, like nerve growth factor activating certain nuclear genes promoting growth

Question 35

What is myelin? What is its function?

Answer 35

whitish, fatty protein-lipoid that creates a sheath that protects and electrically increases transmission speed of nerve impulses
-myelinated fibers conduct nerve impulses rapidly
only associated with axons because dendrites are always non-myelinated

Question 36

Describe the process of myelination in both PNS and the CNS.

Answer 36

PNs: formed by Schwann cells, which indent to receive an axon and then wrap themselves in a jelly roll rashion

Question 37

What are nodes of Ranvier?

Answer 37

myelin sheath gaps because adjacent Schwann cells do not touch each other, occur at regular intervals along a myelinated axon

Question 38

What is the neurilemma? Do all myelinated nerve fibers have neurilemma?

Answer 38

Aka outer collar of perinuclear cytoplasm, all myelinated nerve fibers have a neurilemma because nucleus and cytoplasm of Schwann cells bulge external to myelin sheath

Question 39

Describe association between Schwann cells and unmyelinated fibers of the PNS

Answer 39

Schwann cells form myelinated sheaths in PNs and on-myelinated fibers conduct impulses more slowly. sometimes they surround peripheral nerve fibers but coiling does not occur so they only partially enclose and these fibers are un-myelinated an typically thin fubers