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Organ Systems III > Exam 1 > Flashcards

Exam 1 Flashcards

0
Q

What do Shh and BMP growth factors do?

A

Differentiate neural tube along dorsal/ventral axis with use of concentration gradients

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1
Q

What is the neural plate?

A

Derivation of ectoderm that eventually forms the neural tube (4th wk)

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2
Q

What is primary neurulation

A

The columnarization of existing epithelium followed by rolling of the epithelium along the rostro-caudal axis

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3
Q

What is secondary neurulation?

A

The condensation of mesenchyme to the rod, which undergoes an epithelial transition to form the neural tube

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4
Q

What is the mechanism by which the neural tube closes?

A

5 waves of closure beginning in brain stem/upper spinal cord, followed by head, face, neck, and finally ending at the caudal region (sacral part) of spinal cord

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5
Q

What is unique about the sacral part of the spinal cord?

A

It is formed by secondary neurulation as opposed to primary neurulation as seen in thee rest of the spinal cord

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6
Q

What is anencephaly?

A

Lack of skull/cerebrum formation due to the failure of wave 2 neural tube closure

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7
Q

What is spina bifida?

A

Incomplete formation of spinal cord and vertebrae due to incomplete closure of neural tube and caudal spinal cord (wave 5)

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8
Q

What is the hind brain?

A

Medulla and pons

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9
Q

What is the midbrain?

A

Mesencephalon

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10
Q

What makes up the forebrain (prosencephalon)?

A

Diencephalon (thalamus, hypothalamus, epithalamus)

Telencephalon (cerebral hemispheres)

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11
Q

What do rostral/caudal refer to?

A

Rostral - towards front of brain

Caudal - towards spinal cord

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12
Q

What are the flexures of the brain?

A

Cephalic flexure - ensures optical axes are at proper angle to vertebral column
Pontine flexure - at area of 4th ventricle, edges give rise to cerebellum

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13
Q

What are the rexeds lamina?

A

Functionally specific areas of grey matter

dorsal - sensory
intermediate - autonomic
ventral - motor

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14
Q

What is the dorsal funiculus? What information is carried?

A

Dorsal spinal tracts of white matter comprised of cuneate and gracile fasciculi (smaller tracts)

Carries tactile info to brainstem/thalamus

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15
Q

What info is carried in the lateral corticospinal tract?

A

descending motor info

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16
Q

What info is carried in the spinocerebellar tracts?

A

Tactile/proprioceptive info to cerebellum

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17
Q

Where is pain/temperature carried through spinal cord?

A

Anterolateral system

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18
Q

Besides lateral corticospinal tract, where else is descending motor info carried through spinal cord?

A

Anterior corticospinal, vestibulospinal, and reticulospinal tracts

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19
Q

What does the propriospinal tract do?

A

Surrounds grey matter, interconnecting various spinal levels

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20
Q

What is the substantia nigra?

A

dopamine modulation and motor control center in midbrain

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21
Q

What is the periaqueductile grey (PAG)?

A

Regulation of pain/stress response in midbrain

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22
Q

What are the superior/inferior colliculi?

A

Midbrain structures
superior - vision pathway
inferior - auditory pathway

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23
Q

What is the red nucleus?

A

Part of descending motor pathway in midbrain

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24
Q

What is the cerebral peduncle?

A

White matter of the midbrain involved with sensory/motor pathways to/from spinal cord, brainstem, and cortex

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25
Q

What is the epithalamus?

A

part of diencephalon containing pineal gland

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26
Q

What is the major difference between the anterior and posterior pituitary?

A

anterior is derived from ectoderm and communicates via connecting blood vessels (portal system) from hypothalamus
posterior is derived from neural tube and communicates directly with hypothalamus

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27
Q

What are the 5 main divisions of the cerebral cortex?

A

Frontal lobe - motor cortex, broca’s speech
Parietal lobe - somatosensory, wernicke’s language
Temporal lobe - auditory, memory
Occipital lobe - visual cortex
Insula (between frontal/temporal) - gustatory, visceral, emotional cortex

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28
Q

What are basal ganglia?

A

Gateway of fiber tracts from cortex located in central white matter

globus pallidus, caudate/putamen striatum, substantia nigra, subthalamus

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29
Q

What structures make up the limbic system?

A

Limbic cortex - cingulate gyrus, parahippocampal gyrus, orbital/medial prefrontal cortex
Anterior/medial dorsal thalamic nuclei
Amygdala
Ventral striatum

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30
Q

What is the fovea?

A

Central point of retina with only cones and no rods
point of visual acuity
avascular - reduces vascular interference

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31
Q

What is the macula lutea?

A

Yellow area surrounding fovea

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32
Q

Why is the macula lutea yellow?

A

Accumulated lutein and zeaxanthin (carotenoids) from diet that absorb excess blue/UV light, leaving yellow

33
Q

What is the optic disc?

A

Blind spot on retina containing axons of ganglion cells but no photoreceptors

34
Q

Where does the blood come from the feed the retina?

A

central artery of retina branches from internal carotid and travels through the optic tract

35
Q

What are the layers of cells that light passees through to produce visual info to be processed?

A

Retinal pigmented epithelium
Photoreceptors (rods/cones)
Neural cells - bipolar, amacrine cells integrate info
Ganglion cells - project visual info to thalamus

36
Q

What are the pigments in cones? and rods?

A

Iodopsin in cones

Rhodopsin in rods

37
Q

Where in the photoreceptor cells are rhodopsin/iodopsin stored?

A

Vesicular discs

they respond to different parts of the visible spectrum

38
Q

What is the process of photoreceptor signal transduction?

A

Light converts 11-cis retinal to trans-retinal
Opsin activates phosphodiesterase
Phosphodiesterase reduces cGMP, closing Na/Ca channels
Cell hyperpolarizaes
LESS GLUTAMATE IS RELEASED

39
Q

Are rods or cones more sensitive to light?

A

Rods are more sensitive, allowing vision in dim light, but are achromatic and therefore do not permit color vision
Cones allow visual acuity and color vision, but only in well lit conditions

40
Q

Where are rods and cones located on the retina?

A

Rods are primarily located in the periphery

Cones are concentrated at the fovea, but spread thinly throughout

41
Q

What are the main functions of the retinal pigment epithelium (RPE)?

A

Visual acuity - absorption of light
Antioxidant - absorption of blue light
Maintain photoreceptor excitability - reforms 11-cis retinal
Provides nutrients - glucose/retinol
Phagocytosis of cell debris from light absorption

42
Q

What is found in the optic tract?

A

Axons of ganglion cells transmitting visual info to thalamus
CNS glia (oligodendrocytes/astrocytes)
Central artery
Surrounded by meninges

43
Q

How are ON cells stimulated?

A

Glutamate receptors respond to low levels of glutamate (in light)
Ganglion cells are depolarized/excited and transmit AP

44
Q

How are OFF cells stimulated?

A

In darkness, increased glutamate stimulates OFF cells to depolarize
*There is an active response to darkness

45
Q

How is the receptor field organized in the retina?

A

Center-surround fields of ON/OFF cells
Circular areas of retina are organized into concentric rings where inner receptors activate ganglion cells in one way, and surrounding region activates in the opposite way

46
Q

What does center-surround organization of receptor field allow?

A

Lateral inhibition accentuates contrast and allows small objects to be seen in contrast

47
Q

What types of cells code for color?

A

Ganglion cells

Reciprocal excitation/inhibition by cones with different pigments differentiates colors

48
Q

What would result from a lesion of optic nerve, distal to chiasm?

A

Complete blindness of one eye

49
Q

What would result in a lesion at the optic chiasm?

A

Heteronomous hemianopsia - loss of half of visual field, opposite sides from each eye (tunnel vision)

50
Q

What would result in a lesion of the optic tract, proximal to chiasm?

A

Homonymous hemianopia - loss of half of visual field, same side in both eyes

51
Q

What information is transmitted via the parvocellular pathway? What cells are involved?

A

Color and shape info for object identification involving midget cells, which comprise ~90% of optic nerve axonal cells, allowing acute vision with smaller center-surround receptor fields

52
Q

What type of info is transmitted via the magnocellular pathway? What cells are involved?

A

Information regarding motion and direction, involving parasol cells, which grasp visual attention, but with low acuity (larger center-surround receptor fields)

53
Q

Where in the brain do the magnocellular and parvocellular pathways transmit visual information to?

A

Visual info is transmitted via magnocellular/parvocellular pathways through optic tract to the 6 cellular layers of lateral geniculate nucleus (LGN) of thalamus

54
Q

Where does visual information go to from the LGN?

A

LGN neurons carry visual info to the primary visual cortex (V1) on medial surface of occipital lobe

55
Q

What are 2 different types of cells that are found in the primary visual cortex?

A

Simple cells and complex cells, organized in columns

56
Q

Differentiate between the actions of simple and complex cells.

A

Simple cells combine info from several LGN cells that is then transmitted to complex cells - allow perception of object (edges)
Complex cells combine info from several simple cells, or directly from LGN cells - allow perception of position/orientation

57
Q

What are visual cortical columns?

A

Vertical zones of visual cortex including simple and complex cells that sort information into properties based on orientation of edges, shape, size, direction of movement, R or L eye dominance

58
Q

What are ‘blobs’?

A

Areas within columns of primary visual cortex that process info from red-green or blue-yellow center-surround RFs of the retina in order to form the perceptual palate

59
Q

What is stereopsis?

A

Depth perception - gathered primarily by means of binocular retinal disparity
Some depth perception can be gathered from monocular vision

60
Q

What is the function of cortical feeedback?

A

Cortical feedback from the visual cortex to the LGN helps shape sensory input to allow for greater visual acuity

61
Q

What is the mechanism for cortical feedback?

A

Lateral inhibition of LGN cells increases the number of LGN responding to sensory input to enhance cortical transmission of information

62
Q

Besides cortical cells, what is another source of input to the LGN?

A

Pathways from the brainstem release serotonin, NE, AC, and NO (reticular formation) which stimulates visual transmission, also causing cortical feedback

63
Q

What information is transmitted via the ventral pathway from V1?

A

Ventral, parvocellular pathway transmits information from fovea (cones) through infratemporal gyrus to answer the question of WHAT? (ie color, texture, shape, size - detail)

64
Q

What information is transmitted via the dorsal pathway from V1?

A

Dorsal, magnocellular pathway transmits info from peripheral retina (rods) to posterior parietal cortex to answer the question WHERE? (ie location, movement, spatial relations)

65
Q

What information is processed by V2? And V4?

A

V2 cells process more complex info - angles/orientation

V4 cells process color and other complex info concerning shape

66
Q

What is the function of the inferotemporal cortex?

A

IT neurons respond to shape/color from ventral/parvocellular pathway for perception of complex images (faces/hands/emotions)
Activity of IT neurons can be modulated by attention and memory from limbic system and amygdala

67
Q

Where is the fusiform gyrus? What information is processed?

A

Fusiform gyrus is part of the inferotemporal cortex

Processes visual information in association with emotions (ie facial recognition)

68
Q

What is synesthesia?

A

Hereditary condition where one experiences different modalities simultaneously - ie numbers associated with colors

69
Q

What is the koniocellular pathway?

A

Large receptor fields (no center-surround) are projected to superior colliculus for spatial resolution in order to orient head/eyes to the visual stimulus

70
Q

What are saccadic eye movements?

A

Quick, simultaneous movements of both eyes initiated cortically or by superior colliculus to modulate CN III, IV, VI
Vision is fixated between saccades, with seeing only occurring at pauses between movements

71
Q

What are 2 types of saccadic eye movements?

A

Reflex saccade - exogenous - triggered by peripheral stimulus
Scanning saccade - endogenous - exploring visual environment/reading

72
Q

Describe the phenomenon of blindsight.

A

Lesion in V1 leads to complete lack of consciousness of visual info, yet info is processed by extrastriate pathway to parietal areas of brain
Koniocellular pathway via superior colliculus could also allow for some processing of visual info.

73
Q

What is the pathway connecting vision and emotions?

A

Koniocellular pathway to superior colliculus transmits info to pulvinar nucleus of thalamus that interconnects many area of cortex - amygdala, cingulate, and orbitofrontal cortex

74
Q

What is the suprachiasmatic nucleus?

A

Hypothalamic nucleus just above the optic chiasm involved with the circadian rhythm

75
Q

How does the SCN set the circadian rhythm?

A

Melanopsin ganglion cells (intrinsically photosensitive) project to SCN
SCN projects to PVN of hypothalamus which regulates sympathetic/parasympathetic systems and release of pituitary hormones
Light and dark entrains this rhythm

76
Q

What is melatonin? Where does it come from and what does it do?

A

SCN regulates melatonin release in the dark from pineal gland through sympathetic activation
Melatonin helps regulate various organs, sleep/wake cycles, and cortisol release

77
Q

What is the purpose of the pupillary light reflex?

A

Maintains homeostatic level of light entering eye

consensual pupillary response causes constriction of both pupils in response to light entering one eye

78
Q

What muscles are sympathetically innervated to increase light entering eyes?

A

Dilator pupillae - opens pupil

Tarsal muscle - raises upper eyelid

79
Q

What is Horner’s Syndrome?

A

Sympathetic damage, causing ptosis (drooping eyelid), due to inactive tarsal muscle

Organ Systems III (5 decks)

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