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PHGY 209 > CNS/sensory 2 - blood/sensory > Flashcards

CNS/sensory 2 - blood/sensory Flashcards

1
Q

what is usually the only substrate metabolized by brain

A

glucose

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2
Q

what is very little in the brain

A

Glycogen

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3
Q

what does brain need

A

continuous supply of glucose and oxygen (to metabolize glucose constantly)
brain does not store glucose so it needs constant supply

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4
Q

does glucose transport into brain require insulin

A

no

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5
Q

what happens when diabetes

A

if too much insulin = affect formation of nervous system
makes them act drunk - too much insulin = causes glucose to be absorbed by tissues = not enough for brain
can get a candy and eat sugar to bring glucose back

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6
Q

how much blood does brain receive

A

15% of total blood
but 2% of total mass
blood hog
body will do everything it can to keep glucose flowing to brain - breaks down muscle/fat

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7
Q

what happens if blood supply interruption

A

loss of consciousness
a few mins = neuronal death - stroke - neurons die

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8
Q

describe flow of blood supply to brain

A

common carotid artery - branch off aorta
vertebral artery - carry blood to brain (and vertebrae/brain stem)
internal carotid artery = base of brain
external carotid artery = outside head, arterial blood to outside surface of head

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9
Q

what is basilar artery - brain blood supply

A

2 vertebral arteries join and form basilar artery

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10
Q

what is circle of willis

A

basilar artery + 2 internal carotid arteries join at base of brain
forms loop

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11
Q

what does circle of willis act as

A

safety factor
allows blood to be shunted from one side to other side
like if arteries are not doing well = other side compensates

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12
Q

describe CSF and blood circulation

A

CSF
heart to choroid plexus –> (ventricles) subarachnoid space –> (arachnoid villi) dural sinus –> venous system –> heart

blood
from heart –> vertebral and carotid arteries –>
(basilar artery) circle of willis (also carotid arteries go straight to circle of willis) –> brain –> venous system –> heart

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13
Q

what is blood brain barrier

A

capillary wall

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14
Q

what does blood brain barrier do

A

regulates brain internal composition

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15
Q

what moves easy through blood brain barrier

A

water
carbon dioxide
oxygen
lipid soluble substances

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16
Q

what is weakly transported in blood brain barrier

A

na
k
cl

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17
Q

what will not cross blood brain barrier

A

plasma proteins
large organic molecules

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18
Q

how is glucose and some aas transported in blood brain barrier

A

active transport of glucose
some aas
or passively diffuse

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19
Q

what does capillary of blood brain barrier have

A

tight junctions between endothelial cells
endothelial cells line capillary
in other parts of body = gap junctions, allows things to easily flow out but not good for brain, very careful about what is allowed into ECF of brain

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20
Q

describe foot processes of astrocytes of blood brain barrier

A

glial cell
when attached to capillaries = induce tight junctions between endothelial cells

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21
Q

if treating disease what must you consider about blood brain barrier

A

must make sure it can cross barrier

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22
Q

describe effect of caffeine on brain

A

very lipid soluble
flies across blood brain barrier

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23
Q

describe effect of alcohol in brain

A

alcohol can cross

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24
Q

describe effect of drugs in brain

A

certain drugs like heroins, opiods
morphine does not cross but when converted to heroin = crosses blood brain barrier and then in brain enzymes convert heroin back to morphine but then morphine cannot get out

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25
Q

what is an astrocyte

A

network of glial cells that maintain structure of brain and extracellular environment around neurons in brain

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26
Q

name and describe 5 functions of astrocytes

A

phagocytosis of debris (collect debris or garbage floating around and keep things working well)
glutamate (takes up excess neurotransmitters)
K+ (regulate concentration of ions)
provide structural support
induce tight junctions

27
Q

what is sensation

A

awareness of sensory stimulation

28
Q

what is perception

A

Understanding of a sensations meaning

29
Q

what do we perceive

A

we do not perceive energy of sensory stimulus directly
only perceive neural activity that is produced by sensory stimulation
like ear = sound is changes in pressure = do not perceive that but do perceive changes in neural activity coming from auditory afferent

30
Q

what is law of specific nerve energies

A

Regardless of how a
sensory receptor is activated, the sensation felt
corresponds to that of which the receptor is specialized
designed to transduce

31
Q

give ex of law of specific nerve energies

A

rub eyes hard and see light
intraocular pressure
neuron activate by mechanical energy

32
Q

what is law of projection

A

regardless of where in the brain you stimulate a sensory (afferent) pathway, sensation is always felt at the sensory receptors location
perception is it location of receptor - receptor location = sensation

33
Q

give 1st ex of law of projection

A

penfield electrically stimulated somatic sensory cortex and patients perceived somatic sensation in body
stimulate somatosensory info in cortex and felt in foot - where receptor started off

34
Q

give 2nd ex of law of projection

A

phantom limb pain
somatosensation
axons severed but afferents do not die since cell bodies are in dorsal root ganglion
as amputation heals afferents try to regrow and sprout and connect to things
then activated by movement or somatosensory stimuli that would not normally cause pain
perception = hurting body part that isnt there, due to the 2 laws

35
Q

what is modality

A

general class of a stimulus
brain knows

36
Q

what are sensory inputs represented by

A

labeled line code

37
Q

what is labelled line

A

brain knows modality and location of every sensory afferent
see laws

38
Q

what is an exception to labelled line code

A

pain - referred pain
miswiring of painful stimuli and labeled line code breaks down a bit

39
Q

describe sensory receptors

A

proteins designed to respond to specific stimulus energy
in specialized membranes - can be part of axon - sends info to brain
or be a receptor cell

40
Q

describe what happens - sensory receptor pathway

A

adequate stimulus - specificity
1 - stimulus energy
2 - receptor membrane
3 - transduction
4 ion channel activation
5 afferent - to cns

41
Q

describe transduction

A

stimulus energy converted to neural activity by opening or closing of ion channels

42
Q

describe receptors - neurons/cells

A

specialized intermediate neurons or cells that encode stimulus and transmit to other neurons and send ap to brain

43
Q

name an ex of receptor cell

A

retina = more than one
circuitry in eye that initially processes visual input and then info sent via afferent from eye to brain via optic nerve

44
Q

describe how stimulus energy is converted to afferent activity

A

stimulus energy
receptor potential - membrane depolarization
action potential - if bigger than threshold
propagation of action potentials
release of neurotransmitter

45
Q

describe stimulus intensity and afferent response

A

diff amounts of stimulus energy encoded by afferent activity in 3 ways

46
Q

name 3 ways stimulus intensity is told by afferent response

A

magnitude of receptor potential
frequency of action of potentials
magnitude of neurotransmitter release

proportional to frequency of aps

47
Q

what do majority of afferents show

A

adaptation
allows up to be sensitive to changes in sensory input

48
Q

describe non adapting afferent response

A

encodes stimulus intensity and slow changes
not change frequency of ap

49
Q

describe slowly adapting afferent response

A

faste change = initiate stimulus
some stimulus intensity and moderate stimulus changes

50
Q

describe rapidly adapting afferent response

A

ap frequency changes but stimulus does not change
on response and off response
fast stimulus changes

51
Q

what is more important to know about a stimulus

A

more important to know when things are changing

52
Q

what is receptive field

A

region in space that activates a sensory receptor or neuron

53
Q

describe response across receptive field

A

graded response
not uniform
issue since brain only listens to afferent info
brain does not know if light stimulus or strong at edge of receptive field
middle is highest afferent response - lowers toward edges

54
Q

describe receptive fields overlapping

A

one somatosensory response produce effects in overlapping receptive fields
produce population code - pinpoint where it is located

55
Q

what is acuity

A

ability to differentiate one stimulus from another
linked to size of receptive field

56
Q

describe acuity and receptor field size

A

small RF - High acuity - like lips
large RF - low acuity - Like BAck
poke with 2 points - further apart but feel one = low acuity

57
Q

what does lateral inhibition do

A

sharpens sensory acuity

58
Q

describe lateral inhibition - generally

A

interneurons inhbit neurons around it
stimulus in center of receptive field = largest inhibitory effect

59
Q

what do descending pathways modulate

A

sensory inputs

60
Q

what is sensory info shaped by

A

top down
bottom up mechanism

61
Q

what can brain do - sensory info shaped by

A

brain can inhibit neurons and turn off neurons carrying info up spinal cord = descending top down modulation

62
Q

give ex of top down mechanisms

A

attention mechanisms
pain highly modulated by state of brain
descending pathway that modulates sensory input
can shut off pain - which does happen
synapses have opiate receptors = why morphine works

63
Q

give example of bottom up processing

A

lateral inhibition - occurs all by itself as sensory into going to brain

PHGY 209 (19 decks)

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