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Anatomy 300L > ANA 303 Meninges, Synapses & Blood Supply To The Brain > Flashcards

ANA 303 Meninges, Synapses & Blood Supply To The Brain Flashcards

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1
Q

The cranial meninges are composed of 3 membranous connective tissue layers namely:

A

Dura mater (dura): tough, thick external fibrous layer
Arachnoid mater (arachnoid): thin intermediate layer
Pia mater (pia): delicate internal vasculated layer

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2
Q

Dura mater is also called the__________

A

pachymeninx

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3
Q

The dura mater is adherent to the internal table of the_________

A

calvaria

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4
Q

Layers of the dura mater

A

external periosteal layer
an internal meningeal layer

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5
Q

what is the epidural space?

A

The internal meningeal layer is intimately fused with the external periosteal layer, but separation can occur pathologically creating an actual (blood or fluid filled) space

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6
Q

The____________forms dural infoldings which divide the cranial cavity into compartments, forming partial partitions (dural septa) between certain parts of the brain

A

internal meningeal layer

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7
Q

list the dural infoldings of the internal meningeal layer

A

Cerebral falx (falx cerebri)
Cerebellar tentorium ( tentorium cerebelli)
Cerebellar falx ( falx cerebelli)
Sellar diaphragm (diaphragma sellae)

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8
Q

Describe the falx cerebri (shape, size and location)

A

is a sickle shape structure
the largest dural infolding
lies in the longitudinal cerebral fissure and separates the right and left cerebral hemispheres

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9
Q

Attachments of falx cerebri

A

Anteriorly: median plane from the frontal crest of the frontal bone and crista galli of the ethmoid bone
posteriorly: to the internal occipital protuberance

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10
Q

Boundaries of the cerebri falx

A

The superior sagittal sinus runs in its upper fixed margin
the inferior sagittal sinus runs in its lower concave free margin
It ends by becoming continuous with the cerebellar tentorium
and the straight sinus runs along its attachment to the tentorium cerebelli

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11
Q

Discuss the size and shape of the Cerebellar tentorium

A

the 2nd largest dural infolding
is a wide crescentic septum

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12
Q

Cerebellar tentorium separates the__________ from the cerebellum

A

occipital lobes of the cerebral hemispheres

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13
Q

Cerebellar tentorium it covers the____________ and supports the occipital lobe

A

upper surface of the cerebellum

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14
Q

The cerebellar tentorium divides__________

A

the cranial cavity into supratentorial and infratentorial compartments

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15
Q

The supratentorial compartment is divided into right and left halves by the__________

A

cerebral falx

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16
Q

Describe the Cerebellar falx and its role

A

is a vertical dural infolding that lies inferior to the cerebellar tentorium in the posterior part of the posterior cranial fossa
It is attached to the internal occipital crest
partially separates the cerebellar hemispheres

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17
Q

Describe the Sellar Diaphragm and its role

A

the smallest dural infolding
is a circular sheet of dura that is suspended between the clinoid processes
forms a partial roof over the hypophysial fossa in the sphenoid
The sellar diaphragm covers the pituitary gland in this fossa and has an aperture for passage of the infundibulum and hypophysial veins

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18
Q

The arterial supply to the dura mater travels in the_________ of the dura

A

outer periosteal layer

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19
Q

The arterial supply to the dura mater consists of:

A
  • anterior meningeal arteries in the anterior cranial fossa
  • middle and
  • accessory meningeal arteries in the middle cranial fossa
  • posterior meningeal artery and other meningeal branches in the posterior cranial fossa
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20
Q

All are small arteries except for the__________

A

middle meningeal artery which is much larger

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21
Q

Which artery supplies the greatest part of the dura?

A

middle meningeal artery

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22
Q

The anterior meningeal arteries are branches of the___________

A

ethmoidal arteries

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23
Q

The middle meningeal artery is a branch of the __________

A

maxillary artery

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24
Q

The middle meningeal artery enters the middle cranial fossa through the_____________
divides into;

A

foramen spinosum
anterior branch
posterior branch

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25
Describe the Venous drainage of the dura, particularly the m.m.a and where it drains
The veins of the dura accompany the meningeal arteries The middle meningeal veins accompany the middle meningeal artery, leave the cranial cavity through the foramen spinosum and drain into the pterygoid venous plexus
26
Describe the innervation of the dura in the anterior cranial fossa meningeal branches from the ethmoidal nerves (branches of the ophthalmic nerve [V1]) supply______________
the floor and the anterior part of the falx cerebri
27
Additionally a meningeal branch of the ophthalmic nerve [V1] supply____________
the tentorium cerebelli and the posterior part of the falx cerebri
27
Describe the innervation of the middle cranial fossa
the middle cranial fossa is supplied medially by meningeal branches from the maxillary nerve [V2] laterally by meningeal branches from the mandibular nerve [V3]
27
Describe the innervation of the posterior cranial fossa
The posterior cranial fossa is supplied by meningeal branches from the 1st , 2nd , and sometimes, 3rd cervical nerves
27
The arachnoid mater and pia mater are together refer to as_____________
leptomeninges
27
Clinical significance of the pterion
The pterion is an important area because it overlies the middle meningeal artery Fracture to the pterion can rupture the anterior branch of this artery resulting in hematoma which exerts pressure on the underlying cerebral cortex An untreated meningeal artery can cause hemorrhage which can lead to death in a few hours
28
The pia and arachnoid mater develop from a single layer of mesenchyme surrounding the embryonic brain, becoming the________________
parietal part (arachnoid mater) and visceral part (pia mater) of the leptomeninx
29
Describe the arachnoid mater
is a thin, avascular membrane It is not adherent to the inner surface of the dura mater
30
From its inner surface thin processes called____________arise and cross the subarachnoid space
trabeculae
31
In between the arachnoid and the pia, is a real space called the___________ What does the space contain?
subarachnoid space This real space contains CSF, trabecular cells, arteries, and veins
32
Describe the subarachnoid space
The subarachnoid space surrounds the brain and spinal cord and in certain locations it enlarges into expanded areas called subarachnoid cisterns
33
The arachnoid and pia enter the grooves of the brain T/F
FALSE Unlike the pia, the arachnoid does not enter the grooves or fissures of the brain
34
Describe the pia mater
is an even thinner membrane that is highly vascularized by a network of fine blood vessels The pia is difficult to see, but it gives the surface of the brain a shiny appearance The pia adheres to the surface of the brain and follows all its contours
35
Define a synapse
A synapse is described as a special zone of contact at which one neuron communicates with another It is a specialized junction where axon terminals contact another neuron or cell type
36
Describe electrical transmission
In electrical transmission between nerve cells, the current generated by an impulse in one neuron spreads to another neuron through a pathway of low electrical resistance via gap junctions In an electrical synapse, ion channels connect the cytoplasm of the presynaptic and postsynaptic cells
36
Several neurons may take part in forming complex synapses encapsulated by neuroglial cells to form__________
synaptic glomeruli
36
The importance of electrical synapses
In the adult mammalian CNS, electrical synapses are present where the activity of neighboring neurons needs to be highly synchronized. For example, hormone-secreting neurons in the mammalian hypothalamus are connected with electrical synapses so that they fire almost simultaneously and secrete a burst of hormones into the circulation.
36
Two types of synaptic transmission
electrical and chemical
37
Directionality of electrical synapses
Most electrical synapses in the mammalian nervous system are believed to be the non-rectifying or bidirectional type of synapse.
37
What is a gap junction?
The area where the two neurons are apposed to each other, at an electrical synapse
38
The channels that connect neurons at the gap junction are called
gap junction channels
39
The extracellular space between presynaptic and postsynaptic neurons at an electrical synapse is___________ Compare it to the usual extracellular space
3 to 3.5 nm, which is much smaller than the usual extracellular space (about 20–50 nm) between neurons.
40
connexons
41
connex
42
Describe chemical synapse and its directionality
There is no continuity between the cytoplasm of the presynaptic terminal and the postsynaptic neuron at chemical synapses. Instead, the cells are separated by synaptic clefts, which are fluid-filled gaps (about 20–50 nm). The presynaptic and postsynaptic membranes adhere to each other due to the presence of a matrix of extracellular fibrous protein in the synaptic cleft. unidirectional
43
What is a neurotransmitter?
Neurotransmitters are substances which neurons use to communicate with one another and with their target tissues in the process of synaptic transmission (neurotransmission). Neurotransmitters are synthetized in and released from nerve endings into the synaptic cleft. From there, neurotransmitters bind to receptor proteins in the cellular membrane of the target tissue. The target tissue gets excited, inhibited, or functionally modified in some other way.
44
What is the active zone?
Active zones are the specialized release sites in the presynaptic terminal. The vesicles containing the neurotransmitter are aggregated near the active zones.
45
Types of synapses
axodendritic axosomatic axoaxonic dendrodendritic symmetrical asymmetrical
46
Axodendritic synapse
A synapse in which the postsynaptic membrane is on a dendrite of another neuron. This type of synapse can occur at the spine or shaft of the dendrite. About 30% of the synapses in the CNS are estimated to be axodendritic type.
47
Axosomatic synapse:
A synapse in which the postsynaptic membrane is on the cell body (soma) of another neuron. About 6% of the synapses in the CNS are estimated to be axosomatic type.
48
Axoaxonic synapse
A synapse in which the postsynaptic membrane is on the axon of another neuron This type of synapse is rare.
49
Dendrodendritic synapse
A synapse in which dendrites of specialized neurons form synapses with each other.
50
Symmetrical synapse
A synapse in which the postsynaptic and presynaptic membranes are similar in thickness. This type of synapse is usually inhibitory
51
Asymmetrical synapse
A synapse in which the postsynaptic membrane of a synapse is thicker than the presynaptic membrane. This type of synapse is usually excitatory
52
The brain is supplied by
two internal carotid two vertebral arteries
53
The four arteries lie within the_____________and their branches anastomose on the inferior surface of the brain to form the_________________
subarachnoid space Circle of Willis
54
Internal carotid arteries arise in the neck from which artery?
the common carotid artery
55
Terminal branches of the ICA
Anterior cerebral arteries Middle cerebral arteries
56
The anterior cerebral arteries are joined together by the__________
anterior communicating artery
57
The internal carotid arteries are joined by the posterior communicating arteries to the________________
posterior cerebral arteries
58
the cortical branches of each cerebral artery supply
branches to deeper parts of the brain, the supply a surface and a pole of the cerebrum
59
The cortical branches of the: Anterior cerebral artery supply
most of the medial and superior surfaces of the brain and the frontal pole
60
The cortical branches of the: Middle cerebral artery supply
the lateral surface of the brain and the temporal pole
61
The cortical branches of the: Posterior cerebral artery supply
the inferior surface of the brain and the occipital pole
62
Describe the vertebral arteries Where is arises from, what it forms etc.
•They arise from the first part of subclavian arteries •They unite at the lower border of the pons to form the basilar artery •The basilar artery ends by dividing into two posterior cerebral arteries •Other branches such as the anterior inferior cerebellar arteries, several small pontine arteries, and the superior cerebellar arteries arise from the basilar artery
63
What does the basilar artery supply?
The basilar artery supply the brainstem, cerebellum and cerebrum
64
What’s the main blood vessel that forms the posterior circulation of the brain?
Basilar artery

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