Nervous Tissue

Question 1

What does the CNS consist of?

Answer 1

the brain and the spinal cord, located in the cranial cavity and spinal canal

Question 2

what kind of nerves are in the PNS?

Answer 2

cranial, spinal and peripheral nerves, they conduct impulses from and to the CNS, ganglia and specialised nerve endings

Question 3

what are neural pathways?

Answer 3

neural pathways are formed by interactions between sensory nerves that recieve stimuli, the CNS that interprets them and motor nerves that initiate responses

Question 4

the nervous system is divided into:

1. anatomically
2. functionally - one further subdivided into…

Answer 4

1. anatomically into the CNS and PNS
2. Functionally into the somatic and autonomic nervous system

autonomic nervous system is further subdivided into:

    1. sympathetic
    2. parasympathetic
    3. enteric

Question 5

what are the two principal cell types of nerve tissue?

Answer 5

neurons

supporting cells

Question 6

what are synapses?

Answer 6

an axon of the presynaptic neuron terminates into an enlarged tip called the bouton termnal/bulb end. synapses are specialised junctions between neurons that facilitate the transmission of impulses from one (presynaptic) neuron to the other (postsynaptic) neuron. they also occur between axons and effector cells.
they can be stained using siver preparation methods and show up as oval bodies on the surface of receptor neurons.

Question 7

what are glia/neuroglial cells of the nervous tissue?
4 types in CNS
2 types in PNS

Answer 7

CNS: astrocytes, oligodendrocytes, microglia, ependymal cells

PNS: schwann cells, satellite cells

Question 8

what are the functions of neuroglial cells? (6)

Answer 8

1. physical support for neurons (protection)
2. insulation for nerve cell bodies and processes
3. repair of neuronal injury
4. regulation of the internal fluid enviroment of the CNS
5. clearence of neurotransmitter from the synatic clefts
6. metabolic exchange between the vascular system and the neurons of the nervous system

Question 9

what does the autonomic nervous system do?

what do the specific effectors in the internal organs that respond to information of the ANS include?

Answer 9

the ANS regulates the function of internal organs
respond sites include:
smooth muscle
cardiac conduction cells (Purkinje fibres)
Glandular epithelium

Question 10

what is a neuron and how many are there in the human nervous system?
what are the thre general catagories of neurons?

Answer 10

the neuron is the structural and functional unit of the nervous system. there are more than 10 billion in a human NS

three catagories of neurons:
sensory neuron
motor neuron
interneuron (intercalated neuron)

Question 11

what are sensory neurons?

in what fibres are the processes of these neurons included?

Answer 11

sensory neurons convey impulses from receptors to the CNS

somatic afferent fibres: convey sensations of pain, touch, temperature and pressure from the body surface, as well as pain and proprioreception from organs within the body

visceral afferent fibres convey pain impulses and other sensations from internal organs, mucous membranes, glands and blood vessels

Question 12

what are motor neurons?

in what fibres are the processes of these neurons included?

Answer 12

motor neurons convey impulses from the CNS or ganglia to effector cells.

somatic efferent neurons convey voluntary impulses to skeletal muscle

visceral efferent neurons transmit involunary impulses to smooth muscle, cardiac conducting cells and glands

Question 13

what are interneurons?
what is another name?
what percentage of all neurons are interneurons?

Answer 13

interneurons or intercalated neurons form a communications and integrating network between sensory and motor neurons.
interneurons make up about 99.9% of all neurons

Question 14

what are the functional components of a neuron?

Answer 14

cell body (perikaryon,)
dendrites (short processes that recieve impulses and transmit them toward the cell body)
axon (long process that transmit impulses away from cell body)
synapse (specialised terminal of axon, contacts other neurons or effector cells)

Question 15

based on the number of processes, how are neurons anatomically classified and define each class?

Answer 15

multipolar: one axon and one or more dendrites. mostly found to be motor neurons and interneurons
bipolar: one axon and one dendrite. rare. generally receptors for special senses.
psuedounipolar: one process, an axon, that divides close to the cell body. two long axonal processes, one toward the periphery the other toward the CNS. majority are sensory neurons close to the CNS. cell bodies found in dorsal root ganglia and cranial nerve ganglia.

Question 16

neuron cell body:

describe the nucleus

Answer 16

the neuron contains a large, euchromatic nucleus with prominent nucleolus

Question 17

neuron cell body:

describe the perinuclear cytoplasm

Answer 17

the perinuclear cytoplasm contains abundant rER and free ribosomes - protein synthetic activity
nissl bodies can be seen, ribosomal content, small bodies that stain intensly with basic dyes. each body corresponding to a stack of rER
perinuclear cytoplasm also contains numerous mitochondria, a large golgi apparatus, lysosomes, microtubules,d neurofilaments, transport vesicles adn inclusions.

Question 18

what is the axon hillock and how can it be distinguished from dendrites?

Answer 18

the axon hillock is the area of the cell body that is connected to the axon.
the axon hillock is devoid of any cytoplasmic organelles whereas the dentrites may contain Nissl bodies, free ribosomes and golgi .

Question 19

what are dendrites?

what are the characterists of dendrites?

Answer 19

dendrites are short receptor processes that receive information from other neurons or from external enviroment and carry that information to the cell body.
dendrites:
generally located in hte vicinity of the cell body
have a larger diameter than axons
are unmyelinated
are usually tapered
form dendritic trees (increases receptor surface area of a neuron)
have cytoplasm similar to the perinuclear cyto;plasm of the cell body, with the exception of the presence golgi apparatus

Question 20

what are axons?

what are the two types of neurons characterised by axon length?

Answer 20

axons are the effector processes of neurons that convey information from the cell body to another neuron or to an effector cell.

golgi type I neurons contain axons that originate in the motor nuclei of the CNS and may travel for more that a meter to their effector targets, skeletal muscles.

golgi type II neurons are interneurons of the CNS and have short axons.

Question 21

what is the axon hillock and what organelles pass through it to the axon?

Answer 21

the axon hillock is the area between the cell body and the axon and is devoid of large perinuclear cytoplasmic organelles.
microtubules, neurotubules, vesciles and mitochindria may pass through it to the axon.

Question 22

what is the initial segment of the axon?

Answer 22

the initial segment of the axon is the region between the apex of the axon hillock and the beginning of the myelin sheath.
it is the site where the action potential of the axon is generated.

Question 23

what is the area between the apex of the axon hillock and the beginning of the myelin sheath? and why is it important?

Answer 23

initial segment

site where the action potential is generated

Question 24

what are periaxoplasmic plaques?

Answer 24

discrete areas in larger axon terminals capable of local protein synthesis modulated by neuronal activity
may be involved in the processes of neuronal cell memory.

Question 25

morphologically classify synapses between neurons:

Answer 25

axodentritic: between axons and dendrites axosomatic: between axons and cell bodies of neurons axoaxonic: between axons and axons

Question 26

synapses are classified dependent on two critera, what are they? what are the two classifications of synapses?

Answer 26

classification of synapses are dependent on: 1. the mechanism of conductance of the nerve impulse 2. the way the action potential is generated in target cells synapses are classified are chemical or electrical synapses

Question 27

what are chemical synapses?

Answer 27

conductance is achieved by the release of chemical substances (neurotransmitters) from the presynatic neuron. neurotransmitters then diffuse across the narrow intercellular pace that separates the presynaptic neuron and postsynaptic neuron/effector cell

Question 28

what are electrical synapses?

Answer 28

common in invertebrates. contain gap junctions that permit movements of ions between cells and consequently permit the direct spread of electrical current from one cell to another. electrical synapse does not require neurotransmitters. in humans this type of synapse is seen in smooth muscle and cardiac musce cells.

Question 29

what 3 components does a typical chemical synapse contain?

Answer 29

1. presynaptic element 2. synaptic cleft 3. postsynaptic membrane

Question 30

what is the presynaptic element? | what is it characterised by?

Answer 30

the presynaptic element is the end of the neuron process from which neurotransmitters are released. the presynaptic element is characterised by the presence of synaptic vesicles, membrane bound structures that range from 30-100nm in diameter and contain neurotransmitters.

Question 31

describe the binding and fusion of synaptic vesicles to the presynaptic plasma membrane.

Answer 31

synaptic vesicles bind and fuse to the presynaptic plasma membrane mediated by a family of transmembrane proteins called SNAREs. v-SNAREs and t-SNAREs specifically. another vesicel-bound protein (synaptotagmin I) then replaces th SNARE complex which is subsequently dimenteled and recycled by NSF/SNAP25 protein complexes.

Question 32

what are active zones of the presynaptic plasma membrane?

Answer 32

active zones are dense accumulations of proteins present on the cytoplasmic side of the presynaptic plasma membrane. they are specialised areas where synaptic vesicles dock and release neurotransmitters into the synaptic cleft. active zones are rich in Rab-GTPaase docking complexes, t-SNAREs and synaptotagmin binding proteins.

Question 33

what is the synaptic cleft?

Answer 33

the synaptic cleft is the 20-30nm space separating the presynaptic element and the postsynaptic membrane or target cell, where neurotransmitters must cross.

Question 34

where is the vesicle membrane added to the presynaptic membrane and retrieved by endocytosis reprocessed into synaptic vesicles?

Answer 34

synaptic vesicles are formed in the smooth endoplasmic reticulum located in the nerve ending.

Question 35

are mitochondria present in the presynaptic element?

Answer 35

yes, numerous small mitochondria

Question 36

what is the postsynaptic membrane? | how is it characterised?

Answer 36

the postsynaptic membrane contains receptor sites in which the neurotransmitters interact. it is formed from a portion of postsynaptic neuron membrane and is characterised by an underlying layer of dense material, an elaborate complex of interlinked proteins.

Question 37

what is the function of the postsynaptic density?

Answer 37

the postsynaptic density is an elaborate complex of interlinking proteins with serveral functions: 1. translation of neurotransmitter-receptor interaction into an intracellular signal 2. anchoring of and trafficking neurotransmitter receptors to the plasma membrane 3. anchoring various proteins that modulate receptor activity

Question 38

what kind of responses can the release of neurotransmitter cause on the postsynaptic membrane? describe...

Answer 38

excitatory synapse: excitatory neurotransmitters opens Na+ channels, prompting an influx of Na+ that causes local reversal of votage across the postsynaptic membrane to a threshold lever, initiating an action potential and generating a nerve impulse inhibitory synapse: inhibitory neurotransmitters opens Cl- channels in the postsynaptic membrane causing an influx of Cl- which hyperpolarises the the membrane. the generation of an action potential becomes more difficult.

Question 39

what is axonal transport and why is it necessary? | how can axonal transport systems be described?

Answer 39

synthetic activity is concentrated in the nerve cell body and so transport to the periphery is required. axonal transport is a bidirectional mechanism axonal transport carries molecules and information along microtubules and intermediate filaments from the axonal terminal to the nerve cell body and vice-versa. axonal transport can be described as: 1. anterograde transport 2. retrograde transport axonal transport systems can be distinguished by the rate at which substances are transported: 1. slow transport system 2. fast transport system

Question 40

what is anterograde transport?

Answer 40

anterograde transport carries material from the nerve cell body to the periphery using the microtubule-associated motor protein, Kinesin, ATP-dependent.

Question 41

what is retrograde transport?

Answer 41

retrograde transport uses the microtubule-associated motor protein dynein to transport substances from the axonal terminal to the nerve cell body.

Question 42

what is the slow axonal transport system?

Answer 42

slow transport system conveys structural elements that form neurofilaments from the nerve cell body to the periphery at the rate of 0.2-0.4mm/day, only in the anterograde direction.

Question 43

what is the fast axonal transport system? | -fast anterograde/retrograde

Answer 43

fast transport system transports material in both directions at a rate of 20-400mm/day. fast anterograde system transports membrane bound vesicles such as sER, synaptic vesicles, mitochindria. plus sugars, amino acids, nucleotides, neurotransmitters and calcium. fast retrograde system transports much of the same material plus endocytosed proteins from the axonal terminal. fast transport system in both directions uses ATP

Question 44

schwann cells and satellite cells are...?

Answer 44

supporting cells of the peripheral nervous system | peripheral neuroglia

Question 45

astrocytes, oligodendrocytes, microglia and ependymal cells are...?

Answer 45

the supporting cells of the central nervous system | central neuroglia

Question 46

what is the main function of schwann cells? | what are two other functions?

Answer 46

the main function of schwann cells is to support myelinated and unmyelinated nerve fibres. they produce a lipid-rich layer that surrounds the axon. this myelin sheath isolates the axon from the surrounding extracellular compartnet of the endoneurium. and ensures rapid conduction of nerve impulses. axon hillock and terminal arborisations are not covered by myelin other functions include the aid of cleaning PNS debris and guiding the growth of PNS axons

Question 47

what do schwann cells develop from? | and how do they differentiate?

Answer 47

schwann cells develop from neural crest cells | and differentiate by expressing transcription factor Sox-10

Question 48

what are the three domains of the schwann cell plasma membrane?

Answer 48

1. abaxonal plasma membrane exposed to external enviroment or endoneurium 2. adaxonal plasma membrane directly exposed to the axon once the schwann cells enclose the axon a thrid domain is created: 3. mesaxon: double membrane that connects the abaxonal and adaxonal domains and encloses the narrow extracellular space.

Question 49

how much of an axon is enclosed within each schwann cell?

Answer 49

a schwann cell encloses a 0.08 and 0.1mm segment of axons.

Question 50

how is the myelin sheath of an axon from a schwann cell develop?

Answer 50

myelination is initiated when the schwann cell mesaxon surrounds the axon. a sheetlike extension of the mesaxon then wraps around the axon in a spiralling motion.

Question 51

what transmembrane myelin-specific protein are expressed in the compaction of the myelin sheath?

Answer 51

protein 0 (P0) peripheral myelin protein 22kD (PMP22) myelin basic protein (MBP) the positively charged domains of P0 and MBP are used to bring together the inner cytoplasmic leaflets of the plasma membrane

Question 52

what are the major dense lines and intraperiod lines of the myelin sheath?

Answer 52

the major dense lines are the cytoplasmic inner leaflets. inbetween the major dense lines are interperiod lines which are narrow 2.5nm gaps formed by closely apposed but not fused membrane leaflets, the gaps contain extracellular domain of P0.

Question 53

what is the thickness of the myelin sheath determined by? | what is the growth factor involved and where is it expressed?

Answer 53

the thickness of the myelin sheath is determined by the diameter of the axon it is myelinating. the growth factor that regulated the thickness of the myelin sheath is Ngr1, which is expressed on the axolemma (the axon membrane)

Question 54

what are the nodes of ranvier?

Answer 54

nodes of ranvier are located between adjacent schwann cells devoid myelin. they are used in the transport of action potentials along the axon.

Question 55

why is myelin sheath in the schwann cell 80% of lipid? | in what 4 specific locations are small amounts of cytoplasm found in a schwann cell?

Answer 55

the myelin sheath is 80% lipid because as the schwann cell plasma membrane winds around the axon cytoplam is extruded from between opposing layers of the plasma membranes. 1. inner collar of schwann cell cytoplasm between the axon and myelin 2. schmidt-lanterman clefts 3. perinodal cytoplasm, at the node of ranvier 4. outer collar of perinuclear cytoplasm, around the myelin

Question 56

what are schmidt-lanterman clefts?

Answer 56

schmidt-lanterman clefts are small islands within succesve lamellae of the myelin. the cytoplam contains lysosomes, occassional mitochondria and microtubules. the number of clefts correlates to the axon diameter, the larger the axon the more clefts.

Question 57

what are unmyelinated axons in the PNS?

Answer 57

unmyelinated axons are enveloped by schwann cells and their external lamina. the schwann cells are elongated in parallel to the long axis of the axons, and the axons fit into grooves of the surface of the schwann cell.

Question 58

in the PNS what are satellite cells?

Answer 58

satellite cells are PNS support cells. they surround neuronal cell bodies of ganglia, forming a complete layer. in the paravertebral and peripheral ganglia, neuroal cell processes must penetrate between the satellite cells to form synapses they help establish and maintain a controlled microenviroment around the neuronal body, providing extra insulation as well as pathways for metabolic exchanges.

Question 59

what are astrocytes?

Answer 59

astrocytes are the largest of the neuroglial cells that form a network of cells within the CNS and communicate with neurons to support and modulate many of thier acitivies. some stretch their processes from blood vessels to neurons the ends of astrocyte processes expands, forming end feet that cover large areas of the outersurface of the vessel of axolemma.

Question 60

do astrocytes form myelin?

Answer 60

no they do not!

Question 61

what are the two types of astrocytes? and decribe them

Answer 61

1. protoplasmic astrocytes - most common in the outermost covering of the brain - grey matter. they have numerous, short, branching cytoplasmic processes. 2. fibrous astrocytes - mor common in the inner core of the brain - white matter. have fewer processes that are relatively straight both tyoes contain prominent bundles of intermediate filaments composed of glial fibrillary acidic protein, GFAP. but the filaments are much more prominent in fibrous astrocytes

Question 62

what are the functions of astrocytes?

Answer 62

astrocytes play important roles in the movement of metabolites and wastes to and from the neurons. they help maintain the tight junctions of the capillaries that form the blood-brain-barrier. they also provide covering of the 'bare areas' of myelinated axons - at synapses and nodes of ranvier. they may confine neurotransmitters to the synaptic cleft and remove excess neurotransmitters by pinocytosis.

Question 63

what are protoplasmic astrocytes?

Answer 63

protoplasmic astrocytes on the brain and spinal cord surfaces extend their processes (subpial feet) to the basal lamina of the pia mater to form the glia limitans (impermeable barrier surrounding the CNS)

Question 64

what is the glia limitans?

Answer 64

glia limitans is a near impermeable barrier surrounding the CNS

Question 65

how do astrocytes modulate neuronal activites?

Answer 65

by buffering the K+ concentration on the extracellular space of the brain. astrocytes do this by using K+ pumps and K+ channels that mediate the transfer k+ions from areas of high to low concentration. they maintain the K+ concentration in the brains extracellular space - potassium spatial buffering

Question 66

what is potassium spatial buffering?

Answer 66

the maintainance of the K+ concentration in the brains extracellular space by astrocytes.

Question 67

what are oligodendrites? | how do they myelinate axons?

Answer 67

oligodendrocytes are responsible for producing the myelin sheath in the CNS. oligodendrocytes appear as small cells with few processes compared to astrocytes. they are ofen arranged in rows between axons and each cell gives off several tounge like processes that find their way to the axons, where it wraps around a peice of axon and forms an internodal segment of myelin. a single oligodendrocyte can myelinate one or multiple axons near by.

Question 68

what is the difference between unmyelinated neurons of the CNS and PNS?

Answer 68

unmyelinated neurons in the PNS are embedded in neuroglia however most unmyelinated neurons in the CNS are "Bare", they are not embedded in the neuroglia of the CNS.

Question 69

what are microglia? | features of microglia...

Answer 69

microglia are the smallest of the neuroglial cells. they make up 5% of the glial cells in an adult CNS. microglia are the phagocytic cells of the CNS; as they are a part of the mononuclear phagocytic system and originate from granulocyte/monocyte progenitor cells (GMP). microglia have relatively small elongated nuclei they have short twisted processes the body and processes are covered in spikes (equivilent to brush border of other phagocytic cells) they contain numberous lysosomes, inclusions and vesicles but little rER, few microtubules or actin filaments

Question 70

what are ependymal cells?

Answer 70

ependymal cells form an epithelial-like lining that covers the fluid-filled cavities of the CNS. they form a single cuboidal to columnar layer that have fluid transporting cell characteristics.

Question 71

what are the features of an ependymal cell in the CNS?

Answer 71

ependymal cells are tightly bound by junctional complexes at the apical surface. the basal cell surface exhibits numerous infolding that interdigitate with adjacent astrocyte processes the apical surface contains cilia and microvilli (the latter involved in CSF absorption) ependymal cells do not have an external lamina - unlike typical epithelial cells

Question 72

what is the choroid plexus?

Answer 72

the chorid plexus is formed from modified ependymal cells and associated capillaries. (ependymal cells modified to produce the CSF by transporting and secertion of materials derived from adjacent capillary loops)

Question 73

what is saltatory conduction?

Answer 73

saltatory conduction occurs in myelinated axons. the nerve impulse travels along the axons but "jumping" from one node of ranvier to the next. voltage reversal can only occur at the nodes of ranvier where there is a high concentration of voltage gated na+ and k+ channels. the myelin insulates the reversal of internodal segments. the speed is much more rapid than in an unmyelinated axon and is related to the thickness of the myelin sheath and the diameter of the axon (conduction is faster the greater the diameter of the axon)

Question 74

what are neurons and central glia cells derived from? | what glia type is the exception and what is it derived from?

Answer 74

neurons and central glia cells (astrocytes, oligodendrites and ependymal cells) are derived neuroectodermal cells from the neural tube. microglia is the exception as they migrate into the CNS as GMP cells (Granulocyte/Monocyte Precursor cells) derived from peripheral mesendymal cells

Question 75

what are PNS ganglion and PNS glia derived from?

Answer 75

ganglion and glia of the PNS are derived from neural crest cells. PNS ganglia develop processes that reach the cells' target cells. initally more are produced than needed; those that do not make contact with atarget cell undergo apoptosis.

Question 76

what are schwann cells derived from and how do they develop?what are the associated genes involved?

Answer 76

Schwann cells arise from migrating neural crest cells that become associated with an axon during early development. genes associated with schwann cell development include: Y (SRY) Box10 (Sox10) - generation of all PNS glia from NCC Nrg-1 (neuragulin 1) - axon derived growth factor tht sustains schwann cell precursors.

Question 77

what are the three distinct components that hold together the nerve fibres of a peripheral nerve?

Answer 77

endoneurium - loose connective tissue surrounding each individual nerve fibre perineurium - specialised connective tissue surrounding each nerve fascicle epineurium - irregular connetive tissue surrounding each peripherial nerve and fills space between fascicle

Question 78

what are the characteristics of the endoneurium?

Answer 78

not seen under light microscope at the electron microscope level, collagen fibrils of the endoneurium can be seen running parallel and around the nerve fibres, binding them together int a bundle (fascicle) fibroblasts are sparse in the interstial space of nerve fibres and so most of the collagen fibrils are secreted from schwann cells. connective tissue cells seen within the endoneurium are occasional macrophages, mast cells and macrophages. macrophages mediate immunological surveilland and also participate in nerve tissue repair. they proliferate after nerve injury and actively phagocytose myelin debris.

Question 79

what are the characteristics of the perineurium?

Answer 79

perineuirum is specialised connective tissue surrounding a nerve fascicle that contriubtes to the formation of the blood-nerve barrier. the blood-nerve barrier maintain the ionic enviroment of the ensheathed nerve fibres. perineurial cells possess receptors, transporters and enzymes that provide for the active transport of substances across the perineurium. the number of layers in a perineurim depends of the axon diameter, may be one or more layers thick. each layer of cells in a perineurium has external (basal) lamina on both sides. the cells are contractile, smooth muscle-like, and contain an approriate number of actin filaments. with two or more perineurial cell layers, collagen fibrils are found between the layers - fibroblasts are absent tight junctions between the cells of the same layer of perineurium are present and form the basis of the blood-nerve barrier. perineurium is both epithelial-like (tight junctions) and smooth muscle-like (contractile) typical immunological cells are not found within the perineurium compartment. (other than mast cells and macrophages). the reason being the blood-nerve barrier created by perineurial cells. perineurial plays a protective role.

Question 80

what are the characteristics of the epineurium?

Answer 80

the epineurium forms the outermost tissue of the peripheral nerve. typically the epineurium is a dense connective tissue that surrouns the fascicles formed by the perineurium. adipose tissue is associated the epineurium of larger nerves. the blood vessles that supply the nerves travels through the epineurium. they branch and penetrate the nerve fibres and run in the perineurium. the tisse at the endoneurial level is poorly vascularised; metabolic exchange depends on diffussion through the perineurial sheath to the blood vessels.

Question 81

what are afferent receptors? (another name and define) what are the 3 classifications of afferent receptors?

Answer 81

afferent receptors are sensory. they are specialised sturctures located at the distal tips of teh peripheral processes of sensory neurons. they can initiate a nerve impulse in response to stimuli. classified into: 1. exteroceptors - react to stimuli from external enviroment 2. enteroceptors - react to stimuli within the body 3. proprioceptors - react to stimuli within the body (self awareness)

Question 82

how is the Autonomic nervous system organised? | what does the ANS do?

Answer 82

ANS: 1. sympathetic 2 parasympathetic 3. enteric the ANS controls and regulates the body's internal enviroment. the ANS is a part of the PNS that conducts involuntary impulses to smooth and cardiac muscles and glandular epithelium.

Question 83

describe the sympathetic nervous system 1. presynaptic neurons located 2. cell bodies of postsynaptic neurons located

Answer 83

the sympathetic nervous system is a part of the ANS. 1. the presynaptic neurons of the sympathetic division are located in the thoractic and upper lumbar regions of the spinal cord 2. the cell bodies of the postsynaptic effector neurons of the sympathetic nervous system are located in the paravertebral ganglia in the sympathetic trunk

Question 84

describe the parasympathetic nervouse system

Answer 84

the presynaptic neurons of the parasympathetic divsion are located in the brain stem and sacral spinal cord and send axons to visceral gangial.

Question 85

what is the connective tissue surrounding the CNS called? how many layers? name them

Answer 85

the CNS is covered by 3 layers of connective tissue forming the meninges the brain and spinal cord is surrounded by: 1. dura mater - outermost layer 2. arachnoid layer 3. pia mater - innermost layer

Question 86

what is the dura mater?

Answer 86

the dura mater is the outermost layer of the connective tissue that covers the CNS. the dura mater is a thick sheet of dense connective tissue, continuous with the peristeum of the skull

Question 87

describe the arachnoid and pia mater layers of the meninges.

Answer 87

the arachnoid layer of the meninges is a delecate sheet of connective tissue adjacent to the inner surface of the dura mater. the arachnoid space extends arachnoid trabeculae to the pia mater the trabeculae is formed of loose connective tissue fibre containg elongated fibroblasts the space between the arachnoid space and piamater formed by the arachnoid trabeculae is called the subarachnoid space. this is where the CSF is found. the pia mater is a delicate sheet of connective tissue that lies directily on the brain and spinal cord. it is continuous with the perivascular connective tissue sheath of the blood vessels of the brain and spinal cord.