Nervous Tissue Flashcards
1
Q
what are the 2 subdivisions of the nervous system?
A
peripheral and central
2
Q
what makes up the central nervous system? (2)
A
brain and spinal cord
3
Q
what are the 2 divisions of the peripheral nervous system?
A
autonomic and somatic
4
Q
what are the 2 divisions of the autonomic nervous system?
A
sympathetic and parasympathetic
5
Q
what is the autonomic nervous system used to motor? (3)
A
- cardiac muscle
- smooth muscle
- glands
6
Q
what does the somatic nervous system motor?
A
voluntary skeletal muscle
7
Q
what is the function of the sympathetic division of the autonomic peripheral nervous system?
A
active and alert
8
Q
what is the function of the parasympathetic division of the autonomic peripheral nervous system?
A
rest and digest
9
Q
what are the 3 components of the peripheral nervous system?
A
- cranial nerves
- spinal nerves
- associated nerve roots and ganglia
10
Q
what components make up the autonomic nervous system?
A
motor ganglia and the nerves that innervate viscera
11
Q
what components make up the somatic nervous system?
A
motor nerves that innervate skeletal muscle
12
Q
what is nervous tissue composed of?
A
nerve cells (neurons) and their supportive cells (glial cells)
13
Q
how are nerve cell bodies (neurons) often found? what are these called in the CNS and PNS?
A
nerve cell bodies (neurons) are often found in clusters or groups that have common functions;
groups of neurons in CNS: nuclei
groups of neurons in PNS: ganglia
14
Q
what is a nerve fiber?
A
a single axon
15
Q
what is a peripheral nerve?
A
a bundle of nerve fibers (axons) surrounded by their CT sheaths
16
Q
what is all nervous tissue surrounded by?
A
connective tissue
17
Q
what is an organized collection of axons called in the CNS?
A
tract
18
Q
what is an organized collection or axons called in the PNS?
A
nerve
19
Q
what 2 types of fibers does every nerve have?
A
motor and sensory fibers
20
Q
what are the 2 types of nervous tissue in the CNS?
A
white matter and grey matter
21
Q
describe white matter
A
nervous tissue consisting mainly of axons and their myelin sheaths
22
Q
describe grey matter
A
nervous tissue consisting mainly of nerve cells bodies (neurons) and unmyelinated axons (nerve fibers)
23
Q
what are the 3 basic autonomical classifications of neurons?
A
- unipolar (pseudounipolar)
- bipolar
- multipolar
24
Q
describe the structure of unipolar (pseudounipolar) neurons
A
nerve cell body gives off a single axon that bifurcates into a central and a peripheral branch
25
what is the function of unipolar (pseudounipolar) neurons?
afferent neurons that convey sensory information TO the CNS
26
where are unipolar (pseudounipolar) neurons found?
found in sensory ganglia located in specific cranial nerves and in the dorsal roots of all spinal nerves
27
describe the structure of bipolar neurons
nerve cell body gives off two processes
28
describe the function of bipolar neurons
like unipolar, are afferent neurons that convey sensory information to the CNS
29
where are bipolar neurons found (3)/associated with?
associated with special senses, so found in
1. visual retina
2. olfactory epithelium
3. ganglia of vestibulocochlear nerve (used for balance and hearing)
30
describe the structure of multipolar neurons
nerve cell body gives off many dendrites and an axon
31
what is the most common type of axon based on anatomical classification?
multipolar
32
describe the function of multipolar neurons (2)
1. are motor neurons that carry signals AWAY from the CNS
2. are also interneurons that connect sensory neurons to spinal motor neurons
33
what are the 3 groups of neurons based on function?
1. sensory
2. motor
3. interneuron
34
describe sensory neurons
Afferent neurons that transmit sensory impulses TO the CNS
35
describe motor neurons
Efferent neurons that transmit motor impulses away from the CNS
36
describe interneurons
neurons that transmit impulses between neurons; connect sensory Afferent neurons to Efferent motor neurons OR with the next neuron in a chain
37
define neurons (3)
1. nerve cells
2. the structural and function units of the nervous system
3. highly specialized/modified cells which are capable of receiving and transmitting stimuli, often involving sensory transduction
38
what is sensory transduction?
converting a physical or chemical sensory stimulus into an electric signal that results in neuronal activity
39
what are the 2 parts of neurons?
1. cell body (also called soma or perikaryon)
2. neuronal processes
40
describe the size and shape of cell bodies of neurons
highly variable based on type
41
describe the nucleus of neurons (2)
1. typically large, centrally located, and euchromatic
2. nucleolus is large and can be mistaken for nucleus!
42
describe the cytoplasm of neurons
typically highly granular and basophilic due to chromatophilic substance (Nissl substance)
43
what is Nissl substance?
the chromatophilic substance that makes cytoplasm of neurons highly granular and basophilic
44
what can be found in the cytoplasm of neurons? (3)
1. rough ER
2. polyribosomes
3. free ribosomes
45
is there cytoplasm in the axon hillock and the axon of a neuron?
nope
46
why do neurons have abundant cytoplasm with abundant protein/ribosomes?
nerve cells can turnover >30% of their protein in a single day
47
what are the 2 neuronal processes of neurons?
1. dendrites
2. axon
48
what are dendrites? (2)
1. the input region of a neuron where excitation is received
2. extensions of the nerve cell body designed to receive synaptic contacts from other neurons
49
what do dendrites contain? compare to axons?
contain Nissl substance and generally much shorter than axons, which DO NOT contain Nissl substance
50
what are axons?
long cytoplasmic projections which conduct excitation between the dendritic and telodedritic zones
51
what is the axon hillock?
the part of the cell body where the axon begins
52
what are 2 other names for neuroglia?
glial cells or gliocytes
53
what are neuroglia/glial cells/gliocytes?
a network of specialized cells (neural glue) that not only form a support structure for the neurons but also perform vital roles in neural development, activity, and injury recovery
54
what are the 2 glial cells of the PNS?
1. ganglionic gliocytes (satellite cells)
2. neurolemmocytes (Schwann cells)
55
describe ganglionic gliocytes/satellite cells of the PNS
form a protective capsule around neuron cell bodies in cranial and spinal nerve (sensory) ganglia
56
describe neurolemmocytes/Schwann cells of the PNS
ensheath or myelinate axons
57
what are the 3 parts of myelinated axons?
1. myelin
2. neurokeratin
3. nerve fiber nodes (nodes of Ranvier)
58
describe how axons are myelinated
an individual neurolemmocyte wraps itself around a portion of an axon in a jelly roll or cinnabon fashion, forming concentric rings of modified plasma membrane that constitute the myelin sheath
59
how many neurolemmocytes are required to myelinate an axon? why?
many; because and individual neurolemmocyte is <1mm in length
60
what accounts for the pale staining quality of peripheral nerves in the white matter of the CNS?
the high concentration of lipid in the myelin sheath
61
what is neurokeratin?
routine tissue processing extracts most of the lipid from the myelin, leaving behind neurokeratin protein which takes up stains and makes myelinated axons look lacy or moth eaten (kind of like elastic cartilage tbh)
62
what are nerve fiber nodes (nodes of Ranvier)?
breaks in the continuity between adjacent neurolemmocytes in myelinated axons, although axons remain uninterrupted
63
what are unmyelinated axons also called?
enclosed or ensheathed
64
are unmyelinated axons truly unmyelinated?
no! in the case of small axons, a single neurolemmocyte will form a protective enclosure around multiple axons, but not jelly roll wrap them
65
what are the 4 glial cells of the CNS?
1. astrocytes/astroglial cells
2. oligodendrocytes/oligodendroglia
3. microglia
4. ependymal cells
66
describe astrocytes (3)
1. ID'd by their large euchromatic nuclei (larges of all glial cells but not as large ar interneurons!)
2. located in both white and grey matter
3. of their many important functions, contribute to the blood brain barrier
67
describe oligodendrocytes (3)
1. ID'd by their round euchromatic nuclei with thick nuclear envelope (eyeliner)
2. in white matter: forms myelin sheaths but myelinates multiple axons
3. in grey matter: serves are a perineuronal satellite cell, providing support to nearby neurons
68
describe microglia (2)
1. small, heterochromatic, cigar-shaped nucleus on sagittal section surrounded by scant cytoplasm
2. macrophages of the CNS
69
describe ependymal cells
specialized neuroglial cells that line the central canal of the spinal cord and the 4 ventricles of the brain
70
describe ependymal cells in the ventricles of the brain
modified ependymal cells fuse to pia mater and form the choroid plexus; simple cuboidal
71
describe ependymal cells in the choroid plexus
in close contact wit the capillaries of pia mater, from which blood plasma is filtered and altered to form cerebrospinal fluid!
72
do all ependymal cells secrete cerebrospinal fluid?
no! only those in the choroid plexus of the brain (simple cuboidal)
73
what is CNS connective tissue also called?
meninges
74
what are the meninges?
3 layers of connective tissue sheaths completely surrounding the brain, spinal cord, and spinal roots
75
what is found between the arachnoid and the pia matter? what is its function?
cerebrospinal fluid; supplies nutrients, removes waste, and cushions during trauma
76
describe the dura mater (3)
1. outer most meninge, very tough covering (TOUGH MOTHER)
2. dense regular to irregular CT
3. thick collagen bundles with elastic fibers
77
what does the dura mater contain? (3)
blood vessels, lymphatic vessels, nerves
78
what are the 2 laminae of the cranial (skull) dura mater?
1. outer lamina fused to periosteum, no epidural space
2. dural venous sinuses located between the two laminae; which are otherwise fused
79
describe the dura mater of the vertebral column
periosteum is not fused to dura mater, so there is a space between the 2 CT layers that becomes fat filled and can be used to deposit anesthetic
80
describe the arachnoid (2)
1. deep to the dura mater
2. consists of a distinct outer membrane of fibrocytes called the arachnoid membrane, with many fine fibrous trabeculae (arachnoid trabeculae) that radiate outward from its inner surface and act as a supportive framework for the subarachnoid space where CSF flows
81
describe the pia mater (2)
1. tightly adherent to the surface of the brain and spinal cord
2. highly vascular layer that surrounds all small vessels traveling in the sulci and fissures to penetrate and supply the nervous tissue
82
describe the PNS connective tissue (2)
1. surrounds the peripheral nerves (like the radial nerve)
2. similar to skeletal muscle CT
83
list and describe the 3 layers of PNS connective tissue
1. endoneurium: strands of collagenous fibers and CT matrix that occupy space between individual, adjacent nerve fibers (axons)
2. perineurium: CT fibers arranged chiefly longitudinally interposed between bundles of nerve fibers (fascicles)
3. epineurium: thicker layers of longitudianlly arranged collagen and matrix surrounding nerve trunks (around groups of fascicles)
84
describe the blood brain barrier (structure and function)
1. a filter that regulates the movement of molecules from blood to the brain
2. endothelial cells of the brain capillaries have occluding/tight junctions and continuous basement membranes, additionally surrounded by/fortified by the foot processes of the astrocytes
85
describe the spinal cord, generally
part of the CNS, surrounded by meninges
86
describe grey and white matter of the spinal cord
grey matter is dee and surrounded by superficial white matter (Opposite of CNS)
87
what does the spinal cord have to communicate with what part of the brain?
central canal communicates with the 4th ventricle of the brain
88
describe the nerves of the spinal cord
spinal nerves on both sides that separate into dorsal and ventral roots between the cord and the intervertebral foramina
89
what do dorsal roots house? what about ventral roots?
dorsal roots house the sensory dorsal root ganglia; ventral roots do not have ganglia
90
describe the white matter of the spinal cord (2)
1. contains axons that are both afferent and efferent
2. subdivided into columns that contain axon tracts (groups)
91
describe the afferent axons of the white matter of the spinal cord
ascending, transmit sensory info to the brain and brainstem
92
describe the efferent axons of the white matter of the spinal cord
descending, relaying motor information from the brain or brainstem to muscles and glands
93
describe the grey matter of the spinal cord
subdivided into dorsal, lateral, and ventral horns
94
describe the dorsal horn of the grey matter of the spinal cord
houses the interneuron cell bodies; afferent sensory neuron fibers synapse on the interneurons
95
describe the ventral horn of the grey matter of the spinal cord
houses motor neuron cell bodies; interneurons synapse on the motor neurons, which send efferent axons out to innervate muscles (somatic motor) and glands (autonomic motor)
96
describe lateral horns of grey matter of the spinal cord
primarily located in the thoracic cord; contain the cell bodies of the autonomic motor neurons that will synapse on a second neuron in the sympathetic ganglia
97
describe the spinal reflex
this is a placeholder if this becomes relevant
