Neuroanatomy Exam 2 Flashcards
Why are arteries black on a T2 weighted MRI?
Fluids are usually white on a T2 MRI. However, the blood within arteries is moving relatively quickly, which makes it appear darker on the image.
What regions of the brain (think vesicles) do the internal charotid arteries supply?
Most of the telencephhalon and diencephalon
What does the vertebral system supply?
Brainstem, cerebellum and parts of the diencephalon, spinal cord, and occipital and temporal lobes
Desrcibe the path the internal chharotid artery takes to reach the brain.
Ascends through each side of the neck, traverses the petrous temporal lobe, passes through the cavernous sinus, and finally reaches the subarachnoid space at the base of the brain
What is the ophthalamic artery?
Off shute of the internal charotid artery as it leaves the cavernous sinus. This artery travels along the optic nerve to th orbit to supply the eye and other orbital structures.
What happens after the internal charotid artery passes the optic chiasm?
Bifurcates into the middle and anterior cerebral arteries
Which artery is often involved in cerebrovascular accidents?
The anterior choroidal artery
What artery supplies the amygdala and portions of the internal capsule?
Anterior Choroidal Artery
What artery supplies the optic tract?
Anterior Choroidal Artery
What artery supplies the choroid plaxus of the inferior horn of the lateral ventricle?
Anterior Choroidal Artery
Describe the general travel of the posterior communicating artery.
Passes posteriorly, inferiorily to the optic tract and toward the cerebral peduncle. Joins the posterior cerebral artery
What connects the two anterior cerebral arteries?
Anterior Communicating Artery
What structure does somatosensory information have to pass through going from the thalamus to the somatosensory cortex?
The internal capsule
What are lenticulostriate arteries?
Branches of the middle cerebral artery that penetrate the brain near their origin and supply deep brain structure of the telencephalon and diencephalon
Where doo the two vertebral arteries fuse to give rise to the basilar artery?
At the junction of the pons and medulla
What branches does the vertebral artery give rise to?
Posterior Spinal Artery
Anterior Spinal Artery
Posteriior Inferior Cerebellar Artery
(Each one gives rise to these 3)
What does the posterior spinal artery supply?
The posterior third of the spinal cord
What does the anterior spinal artery supply?
Anterior two thirds of the spinal cord
What does the posterior inferior cerebellar artery (PICA) supply?
Much of the interior surface of the cerebellar hemispheres
What artery supplies the more anterior portions of the inferior surface of the cerebellum (like the Flocculus) and parts of the caudal pons?
Anterior Inferior Cerebellar Artery (AICA)
What does the superior cerebelar artery supply?
the superior surface of the cerebellum and much of the caudal midbrain and rostral pons
What artery supplies the inner ear?
Internal auditory/labyrinthine artery; occlusion can lead to vertigo and ipsilateral deafness
Which artery sends branches to the thalamus and the splenium?
Posterior Cerebral Artery
What do the posterior choroidal arteries supply?
Choroid plexus of the third ventricle and body of the lateral ventricle
What is cerebral angiography?
uses the intravenous injection of iodinated dyes to make blood much more opaque than brain to x-rays
What is autoregulation?
A way to control cerebral blood flow. Arterial and arteriolar smooth muscle cells are directly stretch sensitive, so the vessels constrict (thus increasing their resistance) in response to increased blood pressure, and they relax in response to decreased pressure
What types of vibers innervate cerebral vessels?
sympathetic autonomic fibers and fibers from several locations within the brain
What is an ischemic infarct?
A necrotic region of tissue resulting from the lack of blood supply
What are the two types of strokes?
Hemorrhagic and Ischemic Infarct
What is a hemorhhagic stroke?
due to either a bursting of a brain aneurysm (an excessive localized enlargement of an artery) or a weakened blood vessel leak
What is the difference between a transient ischemic stroke and an ischemic stroke?
deficits associated with a transient ischemic attack (as the name implies) persist for only a few minutes to a few hours and are followed by an essentially complete recovery
What are the three regions of the blood brain barrier?
(1) the arachnoid barrier layer
(2) the blood–cerebrospinal fluid (CSF) barrier
(3) the true blood brain barrier
What is the Blood-CSF barrier formed by?
tight junctions of the choroid epithelial cells
What forms the “true blood brain barrier”?
rows of tight junctions between adjacent endothelial cells of CNS capillaries together with a lack of pinocytotic vesicles in these endothelial cells
How is the blood-CSF barrier selective?
Lipid-soluble substances can diffuse across it, and glucose can cross it by a process of facilitated diffusion, but other molecules of similar size and solubility cannot. In addition, various substances can be actively transported in both directions across this endothelial wall.
What are circumventricular organs?
Locations where cerebral capillaries are fenestrated and allow free communication between the blood and the brain’s extracellular fluid.
Areas lakcing the red line on the attached picture are where there is no BBB
Name the 6 circumventricular organs
Pineal Gland, Median Eminence (of the hypothalamus), posterior lobe of the pituitary gland, area postrema of the brainstem, and the subfornical organ and lamina terminalis of the hypothalamus
What are tanycytes?
Specialized ependymal cells that overlie each circumventricular organ and form a barrier b/w the organ and the ventricular CSF
What do the dural venous sinuses ultimately drain into?
The internal jugular veins
What is unique about cerebral veins as compared to veins in the rest of the body?
They are valveless
The superficial veins drain the lateral surfaces of the cerebral cortex by way of the….
Superior Sagittal Sinus
The blood-brain barrier (BBB) is present in
The arachnoid barrier and the endothelial cells within the brain parenchyma
What are sensory receptor?
cells that detect various stimuli and produce receptor potentials in response
What are interoceptors?
monitor events within the body, such as distention of the stomach or changes in the pH of blood
What ar exteroceptors?
respond to stimuli that arise outside the body, such as the receptors involved in touch, hearing, and vision
What are nociceptors?
Receptors that respond to pain
What is receptor adaptation?
receptors become less sensitive during the course of a maintained stimulus; can be slowly adapting (don’t change sensitivty much) or rapidly adapting
What are the three parts of a sensory receptor?
1) Receptive Area
2) Area rich in mitochondria (near receptive area)
3) Synaptic Area
Where do the cell bodies of somatosensory receptors lie?
The dorsal root ganglia of the spinal cord
Where do the central processes of somatosensory receptors terminate?
Either in the spinal cord, or in the brainstem
What is a capsule on a receptor?
serves as a mechanical filter, modifying mechanical stimuli before they reach the sensory ending. For example, receptors with layered capsules are rapidly adapting, in large part because of these mechanical properties of the capsules. The capsules also have barrier properties
What is a merkel ending?
found in hairy and non-hairy skin. Terminates on a Merkel Cell which is situated in the basal layer of the skin. It is VERY sensitive to deformation (and general tactile information such as pressure, indentation, etc.)
What are Meissner Corpuscles?
Located in the dermal paillae of hairless skin just beneath the epidermis (responds to touch). It is encapsulated and rapidly adapting.
What are Meissner Corpuscles primarily responsible for?
Feeling pressure; work with merkel endings to perform fine tactile discriminations with FINGERTIPS
What type of receptor is reposnible for feeling vibrations?
Pacinian Corpuscle; the’re also all over the body.
What are polymodal nociceptors?
Nociceptors that respond to multiple modalities (intense mechanical stimuli, high levels of heat or cold, and chemicals released by damaged tissues - these are three modalities, like different types of pain)
What are delta fibers?
Fast conducting (myelinated) fibers for pain, reponsible for that initial sharp feeling of pain
What are C fibers?
Unmyelinated fibers that are slow to conduct pain information, thus resulting in an aching pain usually following an abrupt pain.
What receptors supply muscles?
Muscle spindles
Golgi Tendon Organ (similar to Ruffini Ending)
**These are both encapsulated**
What are muscle spindles?
long, thin stretch receptors scattered throughout almost every striated muscle in the body. These muscle spindles sense muscle length and proprioception
What are the two types of intrafusal muscle fibers?
Nuclear Chain Fibers: nuclei are lined up single file
Nuclear Bag Fibers: nuclei are not single file, they are several apart
What are the two types of sensory endings in the muscle spindle?
1) Primary Ending
2) Secondary Ending
Describe primary endings in muscle spindles.
Selectively sensitive to the onset of muscle stretch but discharge at a lower rate while the stretch is maintained. Sensitive to vibration
Describe secondary endings in muscle spindles
Less sensitive to onset of stretch, but discharge rate does not decline much while stretch is maintained
What are alpha motor neurons?
large motor neurons that supply extrafusal muscle fibers in muscle spindle
What are gamma motor neurons?
the smaller motor neurons supplying the contractile portions of intrafusal fibers
What do golgi tendon organs detect?
Muscle tension; make fine adjustments in muscle tension when called for (such as when handling a raw egg)
T/F: Extensions of the Meninges Envelop Peripheral Nerves
True (see picture)
What does the perineurium form?
perineurial cells are connected to one another by tight junctions - isolate the epineurial spaces from the endoneurial spaces around peripheral nerve fibers. The endothelial cells of capillaries within the perineurium are connected to one another by tight junctions too.
FORMS BLOOD-NERVE BARRIER
How does axon diameter relate to conductance?
Larger diamters mean faster conductance