Chapter 12 Nerve Tissue
CNS basics
-CNS is divided into regions of gray matter and white matter
diverging circuit
- 1 presynaptic neuron whose branches, goes to multiple postsynaptic neurons
what does efferent mean
- going away from something, this is motor neurons
Satellite cells
- in the PNS, supporting cell -surround neuron cell bodies within the ganglia
Central Nervous system
-CNS -includes the brain and spinal cord -integrating and command center
Peripheral Nervous system
-PNS -outside the CNS -nerves from brain and spinal cord -includes cranial nerves, spinal nerves -the peripheral nerves link all regions of the body to the CNS
reverberating circuit
-a pathway has influence over itself, its like breathing once you start it it will continue
what is a sensory neurons
-afferent -the nerve impulse travels transmit impulses towards the CNS -virtually all are unipolar neurons -cell bodies in ganglia outside the CNS -ganglia are in the PNS
Multiple sclerosis
-an autoimmune disease -immune system attacks the myelin around axons in the CNS -neuralgia deficits, you have trouble controlling movement, hard to speak, sensory deficits -reaction time is slower
types of neuroglia cells
-astrocytes -microglia -Ependymal -oligodendrocytes
why is there white matter
-because of mylenated axons
**where are cell bodies found in the spinal cord
-cell bodies are in the anterior portion of the spinal cord -anterior gray matter
what are ganglia
-cell bodies in the PNS
What are neurons
-conduct electrical signals
What are nerves
-cord like organs in the PNS -consists of numerous axons wrapped in connective tissue -Schwann cells
What is stimulation of a neuron called
-depolarization
Motor neurons
-efferent -carry impulses away from the CNS to effector organs -most motor neurons are multipolar -cell bodies are within the CNS (nucleus) -form junction with effector cells
Oligodendrocytes
-form the myelin sheaths in the CNS -have multiple processes -coil around several different axons
What is bipolar neuron
-found in the eye -posses two processes -they are rare neurons, found in some special sensory organs
Where are interneurons found
-found only in the CNS
Node of ravin
-in-between Schwann cells -the action potential can jump over insulated portion
Inhibitory synapse
-inside becomes more negative -action potential is less likely
Visceral motor
-involuntary motor control -this includes the autonomic nervous system
excitatory synapses
-leads to an inflow of positive ions -depolarizes the postsynaptic membrane -drives the postsynaptic neuron towards impulse generation
What is the nervous system and what are the three overlapping functions
-master control center 1. sensory receptor: monitors inside and outside the body, from the PNS to the CNS 2. Process and interprets sensory input: makes decision and integration 3. Dictates a response by activating effector organs: response, muscles, glands, from CNS to PNS
resting neuron
-membrane is polarized more negative on the inside then on the outside -the voltage is about -65mv -the outside is high in Na and the inside is high in K+
Interneurons
-most are multipolar -lies between motor and sensory neurons -confided to the CNS -known also as association neurons
converging circuit
-multiple presynaptic neurons going to 1 post synaptic neuron
Polysynaptic reflex
-multiple synapses -more then 2 neurons
Neuronal Regeneration CNS
-neuroglia never form bands to guide regrowing axons and may hinder axon growth with growth-inhibiting chemicals • No effective regeneration after injury to the spinal cord and brain
Supporting cells are what?
-non excitable -maintenance -insulator (increase conduction)
sensory neuron cell body found where
-out in the periphery in the ganglion
Neuroglia
-outnumber neurons 10 to 1 -make up half the mass of the brain -
What is a unipolar neuron
-possess one short, single process, also known as pseudounipolar -Usually sensory neurons
What is multipolar neuron
-possesses more than 2 processes -numerous dendrites and one axon -can be a motor neuron that could go from spinal cord to the muscle
What are oligodendrocytes
-provide insulation around axons in the CNS
Reflex arch and the 5 different parts
-responsible for reflexes -rapid, autonomic motor response -can be visceral or somatic 1. receptor: hot touch 2. sensory neuron: takes to your posterior side of the spinal cord 3. integration center 4. motor neuron 5. effector
Myelin sheath
-segmented structures composed of the lipoprotein myelin -surround thicker axons -form an insulating layer -prevent leakage of electrical current -increase the speed of impulse conduction
Visceral sensory
-sensing coming from internal organs -stretch, pain, nausea, and hunger
What are nucleus in reference to motor neurons
-several cell bodies clumped together, within the CNS
Action potential on Axons
-strong stimulus applied to the axon so it triggers -nerve impulse or action potential -membrane becomes negative externally -impulse travels the length of the axon, and then the membrane repolarizes itself
describe a neuron
-surrounding the myelin sheath is endometrium, this is a connective tissue -several axons travel side by side these make up a fascicle -this fascicle is wrapped in connective tissue called perineurium -several fascicles together are wrapped in epineurium
What is repolarization
-the inside of the cell will once again be negatively charged
Monosynaptic reflex
-there is one synapse -2 neurons -no interneuron
Somatic sensory
-things we can feel through our skin -touch, pain, pressure, temperature
Somatic motor
-voluntary motor movement -motor innervation of all skeletal muscle
what does visceral mean
0is the internal organs, contains those that get innervated
Regeneration of the peripheral nerve fibers
1.the axon becomes fragmented at the injury site 2. macrophages clean out the dead axon distal to the injury 3. axon sprouts, or filaments, grow through a regeneration tube formed by Schwann cells 4. the axon regenerates and a new myelin sheath forms
How are gray matter and white matter arranged in the CNS? Gray matter and white matter are intermingled in both the brain and spinal cord, depending on whether the axons are myelinated or unmyelinated. White matter surrounds the central cavity of the spinal cord and gray matter surrounds this white matter. Gray matter is deep to the superficial white matter in the spinal cord. White matter is deep to gray matter in the brain, except in the region of the cerebral cortex, where there is an extra superficial layer of white matter.
Gray matter is deep to the superficial white matter in the spinal cord.
Gray matter in spinal cord
H shaped region- surround central cavity -cell bodies are clustered in the gray matter -the H par consists of all the cell bodies -the white matter is all axons
In what instance is axonal regeneration possible? In the CNS, neuroglia form parallel bands to guide axonal extensions to allow reconnection to the original target. If the cell body of a PNS neuron dies, but the axon remains intact, the axon can regenerate a new neuronal cell body. Axon filaments extend through a regeneration tube formed by oligodendrocytes. If the cell body of a PNS neuron survives when an axon is damaged, axon filaments can extend peripherally from the injured site toward the original target.
If the cell body of a PNS neuron survives when an axon is damaged, axon filaments can extend peripherally from the injured site toward the original target.
Which of the following statements describes interneurons? Interneurons are unipolar neurons whose cell bodies are located in the dorsal root ganglia. Interneurons are an embryonic cell type that becomes a neuron. Interneurons are multipolar neurons that are confined to the CNS and are linked together in chains that form complex neuronal pathways. Interneurons are neurons only found in the autonomic nervous system.
Interneurons are multipolar neurons that are confined to the CNS and are linked together in chains that form complex neuronal pathways.
Where is a schwann cell in the motor neuron
It would be F
Which statement below describes the nervous tissue damage associated with multiple sclerosis (MS)? Myelin sheaths produced by oligodendrocytes are destroyed. Myelin sheaths produced by Schwann cells are destroyed. Damage to ependymal cells enable infectious agents in the cerebral spinal fluid to invade the gray matter of the central nervous system and thus disrupt neural processing. Astrocytes fail to regulate ion levels in surrounding nervous tissue, thus nerve signals are disrupted. Microglia over-respond to infectious agents and destroy neurons in the central nervous system.
Myelin sheaths produced by oligodendrocytes are destroyed. Multiple sclerosis is due to an autoimmune response that destroys myelin in the central nervous system. Oligodendrocytes produce the myelin in the central nervous system.
Neuronal regeneration
Neural injuries may cause permanent dysfunction • If axons alone are destroyed, cells bodies often survive and the axons may regenerate
Which statement is true concerning neuronal regeneration? After injury, most neurons are prompted to undergo mitosis. In the CNS, if neuroglial cells form parallel bands to guide new axonal extensions, some return of function to the damaged region of the brain or spinal cord is possible. Reinnervation of the target organ with partial recovery of function is sometimes possible in the PNS. According to recent studies, regions of the thalamus and medulla oblongata have been shown to form new neurons. None of the listed choices is correct.
Reinnervation of the target organ with partial recovery of function is sometimes possible in the PNS.
Which structure is responsible for formation of the regeneration tube following injury to an axon? endoneurium Schwann cells myelin droplets neurofilaments
Schwann cells
The difference between myelinated and unmyelinated axons is that Schwann cells simultaneously surround multiple axons in myelinated axons. Schwann cells form more widely spaced nodes of Ranvier in unmyelinated axons. Schwann cells are not associated with unmyelinated axons. Schwann cells wrap around myelinated axons in concentric layers.
Schwann cells wrap around myelinated axons in concentric layers.
Which of the following statements concerning sensory neurons is incorrect? They contain only dendrites. They have peripheral and central processes. Most are pseudounipolar. Most have their cell bodies in ganglia outside the CNS.
They contain only dendrites
Motor innervation to the stomach is classified as __________ . somatic sensory visceral sensory visceral motor somatic motor
Visceral Motor
Of the following, which is the only structure that is found in the PNS, as opposed to in the CNS? gray matter a ganglion white matter a tract
a ganglion
An axon collateral from one neuron that circles back and synapses with a previous neuron describes serial processing. parallel processing. a reverberating circuit. a converging circuit.
a reverberating circuit
This neuronal region transmits electrical impulses away from the cell body. synapse axon terminal axon cell body dendrite
axon
Action potentials travel along the axon membrane. cell body. myelin. dendrite membrane.
axon membrane
Which of the following is the correct path an impulse takes across a synapse? axon of presynaptic neuron, synaptic cleft, dendrite of postsynaptic neuron synaptic cleft, dendrite of postsynaptic neuron, axon of presynaptic neuron axon of postsynaptic neuron, dendrite of presynaptic neuron, synaptic cleft dendrite of presynaptic neuron, synaptic cleft, axon of postsynaptic neuron
axon of presynaptic neuron, synaptic cleft, dendrite of postsynaptic neuron
The ________ of a presynaptic neuron associates with the dendrite of a postsynaptic neuron. synapse axon terminal axon cell body dendrite
axon terminal
Which relatively rare type of neuron has two processes extending from opposite sides of the cell body? pseudounipolar multipolar unipolar bipolar
bipolar
What important function could be diminished if the cilia on ependymal cells were absent? circulation of cerebrospinal fluid phagocytosis of microorganisms or dead neurons in the CNS nerve impulse transmission formation of myelin sheath around PNS axons
circulation of cerebrospinal fluid, Circulation of cerebrospinal fluid could be negatively affected if cilia on ependymal cells were absent.
in the brain where is the gray matter
deep, and the white is superficial
Ciliated neuroglial cells that form an epithelium and play an active role in forming and moving cerebrospinal fluid are Schwann cells. astrocytes. ependymal cells. oligodendrocytes.
ependymal cells
The entire nerve is surrounded by a tough fibrous sheath called the ectoneurium. perineurium. endoneurium. epineurium.
epineurium
Gray matter in the CNS contains all of the following except neuron cell bodies. fiber tracts. neuroglia. dendrites.
fiber tracts
Motor neurons __________. are located exclusively in the CNS originate as bipolar neurons whose processes divide during development have their cell bodies located in ganglia in the PNS form junctions with effector cells, stimulating muscles to contract or glands to secrete have their cell bodies located in the dorsal half of the gray matter in the spinal cord
form junctions with effector cells, stimulating muscles to contract or glands to secrete
Regeneration of peripheral axons requires migration of neural stem cells from the hippocampus. construction of a collateral that branches from the point of damage. formation of a tube by Schwann cells to guide growth. deposition of neurofilaments to bridge the gap between the original axon fragments.
formation of a tube by Schwann cells to guide growth.
What is found in the PNS and is a collection of cell bodies
ganglia
The peripheral nerve fibers that speed up the movement of the digestive tract are classified as general visceral sensory (afferent). special somatic motor. special visceral sensory. general visceral motor (efferent).
general visceral motor (efferent).
Afferent means what
going to something (CNS) -sensory neurons
Ganglia represent groups of synapses. groups of neuron cell bodies. groups of dendrites. groups of axons.
groups of neuron cell bodies
Schwann cells
in the PNS, supporting cells -also known as neurolemmocytes -surround the axons in the PNS -form myelin sheath around axons of the PNS
Where are interneuron cell body found where
in the posterior part of gray matter
The somatic sensory division of the PNS __________. stimulates contraction of skeletal muscles includes sensation of nausea and hunger includes general senses of pressure, pain, vibration, and temperature in body wall and limbs includes motor innervation of smooth muscle, cardiac muscle, and glands
includes general senses of pressure, pain, vibration, and temperature in body wall and limbs
What are ependymal cells
line the cavities of our brain
Which part or parts of the neuron are found in the white matter of the central nervous system? all parts of the neuron: dendrites, cell bodies, axonal process central processes of unipolar neurons long axonal processes cell bodies and dendrites
long axonal processes
Neuronal regeneration in PNS
macrophages invade and destroy axon distal to the injury • Axon filaments grow peripherally from injured site • Partial recovery is sometimes possible
A somatic motor neuron carries information, such as pain, from the viscera in the ventral cavity to the CNS. motor commands to the skeletal musculature. information that signals muscle contraction in the organs in the ventral cavity. information from the skin to the CNS.
motor commands to the skeletal musculature.
The majority of neurons in the body are pseudounipolar. multipolar. bipolar. unipolar.
multipolar
White matter represents dendrites traveling together in the ANS. myelinated axons traveling together in the CNS. aggregations of neuron cell bodies in the spinal cord. aggregations of neuron cell bodies in the brain.
myelinated axons traveling together in the CNS
What are a bundle of axons in the PNS
nerves
A nerve cell is the same as a nerve fiber. neurilemmocyte. neuron. nerve.
neuron
The chemical substance that is released at axon terminals is called a Nissl body. synaptic vesicle. hormone. neurotransmitter.
neurotransmitter
What is found in the CNS and is a collection of cell bodies
nucleus
Which cells provide the myelin sheath for neurons in the CNS? oligodendrocyctes microglial cells astrocytes Schwann cells
oligodendrocytes
Where are dendrites located
on the receiving end of a neuron
Interneurons are found only in the visceral nervous system. only in the CNS. only in the PNS. only in the autonomic nervous system.
only in the CNS
The covering of a fascicle within a nerve is the perineurium. endoneurium. ectoneurium. epineurium.
perineurium
Which of the following sequences puts the components of a reflex arc in the correct order of their activation? sensory neuron, CNS integration center, motor neuron, receptor, effector motor neuron, receptor, effector, CNS integration center, sensory neuron effector, CNS integration center, sensory neuron, receptor, motor neuron receptor, sensory neuron, CNS integration center, motor neuron, effector receptor, motor neuron, CNS integration center, sensory neuron, effector
receptor, sensory neuron, CNS integration center, motor neuron, effector
The visceral motor division of the PNS __________. includes taste and smell regulates the contraction of smooth and cardiac muscle and regulates secretion by the body's many glands regulates only the sympathetic division of the autonomic nervous system regulates only the parasympathetic division of the ANS
regulates the contraction of smooth and cardiac muscle and regulates secretion by the body's many glands
These glial cells surround the cell bodies of sensory neurons within ganglia of the PNS. microglia Schwann cells satellite cells astrocytes
satellite cells
What is the function of synaptic vesicles inside axon terminals? increase the speed of nerve transmission store and release neurotransmitters generation of nerve impulses conduction of nerve impulses storage of Nissl (chromatophilic) bodies
store and release neurotransmitters
In the brain where is the gray matter located
superficial
Chemical signals diffuse between neurons at this location. synapse axon terminal axon cell body dendrite
synapse
What does somatic mean
the body as a whole
In the region of the spinal cord, the cell bodies of most interneurons lie in the dorsal half of the gray matter. the PNS. sensory ganglia. the ventral half of the white matter.
the dorsal half of the gray matter
What are bundles of axons in the CNS
tracts
What are most sensory neurons
unipolar neurons
