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Physiology > CNS > Flashcards

CNS Flashcards

1
Q

CNs made up of?

A

Brain(Cerebrum,cerebellum,brainstem and spinal cord)

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2
Q

Functions of CNS

A

Patterns of action potentials encode information leading to:

1.Sensory perception
2.Information processing, 3.integration, & storage
Motor and Behavior

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3
Q

Required terms

A

White matter: High density of myelin covering axon pathways (and very few neurons)
Gray matter: High density of neurons and dendrites (Axons also present).
Nucleus: cluster of neurons within the CNS
Ganglion: cluster of neurons outside the CNS
Cortex: dense layers of neurons
Tract: axons within the CNS traveling as a group/usually named based on region of origin & termination (i.e. spinocerebellar tract)
Pathway: similar to tract however it relates more to synaptically connected neurons performing a function

grey matter externally,white matter internally

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4
Q

Cytology of the CNS

A

Neuron…cell to cell communication or signaling
Neuroglia….
CNS
Astrocytes…maintain extracellular environment…buffer…glutamate
Oligodendroglia…myelin sheaths
Microglia (latent phagocytes)…..removing infectious agents
Ependymal cells (line ventricles/CSF production)
PNS
Schwann cells
Satellite cells…similar to astrocytes

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5
Q

BAsic functional unit of the neuron

A

Dendrite,cell body,axon,synapses,spinal cord,

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6
Q

What does Excitatory synapses focus on dendrites or Axon?

A

Dendrites

Axonal dendritic communications

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7
Q

What does Inhibitory synapses focus on dendrites or Axon?

A

Axosomal communication

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8
Q

Contents of the Axon Hilux is

A

High density of sodium Chanel that moves in 1 direction after Excitation(its activated a refractory phase)…greatest probability of generating an action potential

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9
Q

Characteristics of Uni-polar cell type

A

invertebrates have these.

axon and a dendrite coming out as a sngular process

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10
Q

Characteristics of pseudo-uni-polar cell type

A

Primary sensory neurons.

cell body,axon and bifurcates to receive sensory inputs and the other end to spinal cord

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11
Q

Characteristics of bipolar cell type

A

Sensory organs to the eyes, dendritic sites at the and
internurones
middleman

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12
Q

Characteristics of Multi-polar cell type

A

cell body and 2 ends of dendrite sites

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13
Q

Axonal Transports

A

powered by ATP:
Kinesin: anterograde Dynein: retrograde
Motor Neurone-axon to the toe.
.presynaptic terminal relies on generation of protein in the cell body…
active axonal transport allow for energy and ca use for movement of substance from soma to the axon and synaptic terminal
Micro filament and neuro filament
Atp and calcium used by protein for transport..
A lot Atp calcium dependent….
Kinesin…antegrade…to the presynaptic region
Dynein..retrograde..from the presynaptic neurone
expensive
lysosomal degradation as an example.

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14
Q

Neuroglia components

A 
Astrocytes --projection everywhere.
Epindymal cells….produce csf…
Astrocytes may regulate csf production since its connected to Epindymal cells
Can pick up potassium ions
Management of glutamate concentration

Oligodendrocyte…produces myelin

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15
Q

AP

A

they are the same size,needs frequency altered to be able to use more or less

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16
Q

Myelination

A

produced by Oligodencrocytes

Greater conduction velocity

Increases the effective membrane resistance (length constant)

Decreases the capacitance

Restricts action potential generation to the Nodes of Ranvier

Nodes are rich in sodium and potassium channels

+ and – forces attract each other ,blocks the charges from seeing each other so capacitance is decreased.

Ap regeneration does not need to happen throughout the axonal length.
Minimize Atp,conduction at nodes of Ranvier

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17
Q

Myelination benefits

A

Fast reflexes
“Complex mental processing”
Metabolic Advantage

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18
Q

Types of fibres

A

A fibers (myelinated) 1 to 22 microns Subdivided into: α β γ δ in order of decreasing

B fibers (myelinated) 1 to 3 micrometers
C fibers (unmyelinated fibers) 0.1 to 2.5 micrometers
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19
Q

Peripheral nerve fibres and thier reactions

A

A-alpha fibers: motor & proprioception
A-beta fibers: motor, touch, pressure
A- gamma fibers: motor/muscle tone (muscle spindle)
A-delta fibers: pain, temperature,touch
B-fibers: PREganglionic autonomic
C- fibers: dull pain, temperature, touch, POSTganglionic autonomic– NO MYELIN

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20
Q

Synaptic Signaling

A

-Classic Neuron-Neuron Junction
Electrical ..found in brain astrocytes neurons,fast signal transmission

Gap Junctions(cell to cell communication through open channels)
-Chemical

Neurotransmitter mediated

-Neuron-Glial(neurons and astrocytes)

-Extra-synaptic – we now know NT released at a synapse can have actions at locations distal to the original synapse.
Receptors outside synapse

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21
Q

Electrical synapses/Gap junctions

A

found in brain astrocytes neurons,fast signal transmission

Low-resistance pathway between cells that allows current to flow directly from one cell to another
Allows the exchange of small molecules between cells.
Fast & bidirectional
Synchronization of network activity/Electronically coupled neurons
Gap junctions regulated by voltage, intracellular pH, Ca++, and G protein—coupled receptors

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22
Q

Chemical synapsis

A

ACh—nicotinic(NMJ)

Nicotinic(GAnglia site)

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23
Q

Neuropeptide

A

Neuropeptides. In Neuron dense vesicles…co released with something else

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24
Q

Gaseous transmitter

A

nitric oxide…Direct transmission.

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25
Q

Characteristics of a neurotransmitter

A

Criteria
Present in presynaptic terminal
Cell must be able to synthesize the substance
Released upon depolarization of presynaptic membrane
Specific receptor on the postsynaptic membrane (+/- extrasynaptic locations) to respond to it

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26
Q

Differencies between peptide and non peptide neuro transmitters

A

Non peptide or classic neurotransmitter/Peptide transmitter.

Synthesized and packaged in the nerve terminal/Synthesized and packaged in the cell body; transported to the nerve terminal by fast axonal transport

Synthesized in active form/Active peptide formed when it is cleaved from a much larger polypeptide that contains several neuropeptides

Usually present in small, clear vesicles/Usually present in large, electron-dense vesicles

Released into a synaptic cleft/May be released some distance from the postsynaptic cell
There may be no well-defined synaptic structure

Action of many terminated because of uptake by presynaptic terminals via Na+-powered active transport/Action terminated by proteolysis or by the peptide diffusing away

Typically, action has short latency and short duration (msec)/Action may have long latency and may persist for many seconds

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27
Q

Classic neurotransmitters examples(small molecules)

A 
Class I
Acetylcholinexx
Class II: Biogenic Amines
Norepinephrine xx
Epinephrine
Dopamine
Serotonin
Histamine
Class III: Amino Acids
Gamma-aminobutyric acid (GABA)
Glycine…inhibitory….spine
Glutamate….excitate…brain
Aspartate
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28
Q

Classes of neuro peptides and peptide transmitters

A
  1. Hypothalamic-releasing hormones…Luteinizing hormone
  2. Pituitary peptides
  3. Peptides that act on gut and brain…Substance P…increase the number of pain signal coming to brain .opiod will reduce that signal.
  4. Other tissues…
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29
Q

Examples Gaseous Neurotransmitters

A

Are NOT released from “vesicles”
Nitric oxide (NO)(Blood vessels and in the Brain)
Carbon monoxide

Nmda stimulate NO production(Brain)…….Ca from NMDA…calmodulin….activates endothelial nitric oxide synthase which promotes…arginine to convert into….NO

Cerebral vessel tone influenced

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30
Q

Glutamate Activity

A

major excitatory….

Brought into the vesicle by Vglut…..
Glutamatergic neuron stimulated by AP…
after VGCC opens and releases calcium.
..
Glutamate released and stimulates a lot of other receptors
Ligand gated ion channels(NMDA,AMPA, Kainate and gprotein coupled receptors
Metabotropic glutamate receptors.

Glutamate levels are controlled by EAAT1,2,3,4,5(Excitatory Amino Acid transporters)
Excitotoxicity happens because we have glutamate hanging around for too long ..
Major TBI release glutamate into the brain and stimulate glutamate receptors to release calcium too much calcium may cause Apoptosis.

Astrocytes(express these transporters EAAT 1 and 2 that take up glutamate and they contain an enzyme called glutamine synthase which convert glutamate to glutamine that is not active at glutamate receptors.
Glutamine can be excreted from cell and taken back up by presynaptic terminals and in the presynaptic terminal there is an enzyme glutaminase which will convert glutamine back to glutamate.

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31
Q

Post-synaptic responses to neurotransmitter

A

EPSP (or IPSP) occurs when neurotransmitter binds to a post-synaptic receptor
ligand gated ion channel (“fast” transmission)
G-protein coupled receptor (“slow” transmission)
Gaba is main Inhibitory

EPSP…depolarize…….Glutamate NeurotransmitTer(AMpA receptor)…..passess …na and will depolarise
IPSP…

hyperpolarize…….Gaba NT(Gaba receptor) ..passes chloride for increase chloride conductance which then comes in and hyper polarize the cell and cause IPSP
between excitation and inhibitory, the one the happens depends on the membrane potential
the nernst potential of the ions involved..

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32
Q

EPSP excitatory response

A

Increased Na+ influx
Decreased Cl- influx or K+ efflux
Change in receptor expression or enzymatic/metabolic activity (delayed effect)
potassium channel closes or potassium stays in the cell.

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33
Q

IPSP inhibitory response

A

Increased Cl- influx or K+ efflux
pre-synaptic
post-synaptic
Change in receptor expression or enzymatic/metabolic activity (delayed effect)

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34
Q

in IPSP 1 synapse chnahges membrane potential by how much

A

*Each EPSP changes membrane potential by 0.5-1mV at most for <15ms.
What magnitude of change is generally required to reach threshold?
so we need multiple synapse to reach threshold easily by multiple firing
must be done with 15Ms

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35
Q

Spatial and Temporal Summation is Required to Reach the Threshold Potential

A

It is the sum total of all synaptic activity that determines if threshold is reached and and if an action potential is triggered
Facilitation (sub-threshold stimulation)

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36
Q

Function of reverbatory circuit

A

used for short term memory

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37
Q

Most synaptic events occur at the ?

A

Dendrites.

Majority of Synapses are dendritic.

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38
Q

ALkalosis and acidosis does what to neuronal excitability

A

Alkalosis greatly increases neuronal excitability

Acidosis greatly depresses neuronal activity;

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39
Q

What does Hypoxia do to neuronal excitability

A

Decreases.

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40
Q

Drugs can increase or decrease excitability.T or F

A

T

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41
Q

Cerebral cortex

A 
Cranial nerve 1 
Fine tune lower brain functions
Sensory perception
Cognition
Learning 
Large “memory storehouse” 
Motor planning &amp; voluntary movement
Language
Essential for “higher level thought”

2 hemispherer connected by the Corpus Colusum

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42
Q

Fontal lobe

A

Planning and carrying out motor behavior (motor, premotor, cingulate motor, and supplementary motor areas, frontal eye field)
Speech (Broca’s area, inferior frontal gyrus of the dominant hemisphere)
“Intellectual activities”
Personality and emotional behavior (rostral frontal lobe)
MOTOR

Broca’s area

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43
Q

Parietal Lobe

A

Sensory perception and processing (somatosensory cortex/parietal association cortex)
Projections to the frontal lobe carrying somatosensory information modulates voluntary motor behavior
Parietal association cortex processes visual information from the occipital lobe and then sends projections to the frontal lobe to influence motor behavior.
In dominant hemisphere sends somatosensory information to Wernicke’s area.
Establishment of spatial context (non-dominant hemisphere)

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44
Q

Occipital LoBe

A

Visual perception and processing
Projections to the frontal eye fields influence motor behavior of the eyes
Projection to the midbrain modulates convergent eye movements, pupillary constriction, and accommodation.

45
Q

Temporal lobe

A

Processing and perception of sound and vestibular information.
Higher-order visual processing (i.e. facial recognition)
Optic pathways transverse the temporal lobe.
A portion of Wernicke’s area (posterior region of the temporal lobe).
Emotional behavior (medial temporal lobe: limbic system)
Autonomic nervous system regulation (medial temporal lobe)
Learning and memory (hippocampus).

46
Q

Somatosensory Cortex feature,primary motor cortex.

A

density of receptors and its specifically organised to the regions of the body

47
Q

Premotor area features

A

coordination of multiple muscle group ….high conc of mirror neurons…learning a motor task…learning things from watching someone perform a motor movement

48
Q

Cerebellum features

A

Associated nerves: Cranial nerve VIII
Primary functions:
Coordination & Equilibrium
(somatosensory input from spinal cord, cerebral cortex, vestibular organs inner ear)
Sensory association/language
Essential for complex highly coordinated muscular movements (playing tennis, talking, typing, etc.)
Sequencing of motor movement
Makes corrective adjustments to movement in real time based on continuous sensory information from the periphery
Motor learning/muscle memory “learns from its mistakes”

Balancing antagonististic muscle group
Adjust muscle tone
Fine tune movements
Receives input from spinal cord

49
Q

Basal Ganglia features

A

Primary functions:
Influences thalamocortical motor inhibition
Control of fine motor movements and relative intensity, direction, and sequencing of complex movement patterns
Includes the striatum, globus pallidus, substantia nigra, & subthalamic nucleus
No input from the spinal cord, but does receive direct input from the cerebral cortex via the thalamus.
Lesions produce abnormal movement and posture.

50
Q

The brainstem

Medulla,pons,midbrain

A

Associated Nerves: 12 cranial nerves
Primary functions:
Sensation from & motor control of the head neck & face
Input of several special senses (hearing, balance & taste)
Mediate ANS functions (cardiac output, BP, peristalsis of the gut, & pupillary constriction)
Conduit of ascending and descending pathways that carry sensory and motor information to other areas in the CNS
Reticular formation receives a summary of much of the information that enters the spinal cord and brain stem, filters information (excludes irrelevant stimuli) & regulates arousal

51
Q

Medulla

A

Associated nerves: Cranial nerves VIII-XII
Primary functions:
Subconscious CV & respiratory control
Early relay nuclei in auditory, balance/equilibrium, gustation, head and neck control input
Brainstem reflexes

52
Q

Pons

A 
Associated nerves: Cranial nerves V-VIII
Primary functions:
Respiratory control 
Urinary control
Motor control of the eye 
Sensation and motor control of the face
Ventral: Pontine nuclei relay movement and sensation info from cortex to cerebellum
Dorsal: Taste &amp; Sleep
53
Q

Midbrain

A

Associated nerves: Cranial nerves III-IV
Primary functions:
Acoustic relay & mapping
Eye movement, lens & pupillary reflexes
Pain modulation
Contains nuclei and relay pathways critical for motor coordination (i.e. substantia nigra)

54
Q

Thalamus

A

Associated nerves: Cranial Nerve II
Primary functions:
Sensory & motor relay/coordination between cerebral hemispheres and lower CNS regions
Sensory modulation and gating
Regulation of cortical activation (attention & consciousness)
Visual input

Need a functional thalamus to get to a higher level brain function

55
Q

Hypothallamus

A

Associated nerves: Cranial Nerve II
Primary functions:
Sensory & motor relay/coordination between cerebral hemispheres and lower CNS regions
Sensory modulation and gating
Regulation of cortical activation (attention & consciousness)
Visual input
Drive to eat and drive to do things for reward.

56
Q

Amygdala and hypocampus

A

Amygdala primary function:
Social behavior and expression of emotion
Hippocampus primary functions:
Memory

57
Q

Spinal cord Consist of?

A 
Associated Nerves: 
Dorsal ....Sensory
Ventral ...Motor
Primary Functions: 
Sensory input
Reflex circuits
Somatic and autonomic motor output
58
Q

Whats the work of the sensory receptors

A

Transduce changes in environmental energy into electronic signals

59
Q

How do sensory receptors send the environmental enery received to the brain and spinal cord

A

Via action potential

60
Q

Where are the primary afferent neuron cell bodies housed

A

Dorsal root

crainial nerve ganglia

61
Q

Features of the of primary afferent neuron cell body

A

a peripheral process that extends distally within a peripheral nerve to appropriate sensory receptors & (2) a central process that enters the spinal cord/brain through a dorsal root or a cranial nerve

62
Q

Dermatomes are determined by?

A

Embryonic development

63
Q

Groups of Info from the environment is grouped as follows.

A

Exteroceptive information: interaction of the skin with the environment
Fine discriminatory touch …mechanoreceptors

Pain and temperature…pain receptors/thermal receptors

Proprioceptive information: body and limb position informing movement…receptors located in our joints .muscle and tendons..

Enteroceptive information:From different organs in our body.. internal status of the body

64
Q

In all receptor instances,ehats the common underlying fact that is happening

A

Permeability of membrane to ions is changed in all instances by the receptors

65
Q

Sensory Transduction: Receptor Activation

A 
Mechanical (Mechanoreceptor)
Chemical (Chemoreceptor)
Thermal (Thermoreceptors)
Pain (nociceptors)
Electromagnetic (detect photons) lights hitting the eyes.
Etc.
66
Q

Sensory receptors adapt but pain do not adapt…T/F

A

T

67
Q

Ways to change memebrane potential by Receptors

A

(1) by mechanical deformation (2) by chemical activation (3) by alterations in temperature (4) by the effects of electromagnetic radiation

68
Q

3 major types of mechanosensitive Afferent fibres

A

Tactile fibers Fast (FA)
FAI….adapts fast but
able to pinpoint where stimulus is coming from.
or Slow Adaptation (SA)..they continue to fire as long as stimulus is there.(SA1) continue to fire as long as stimulus is there but small receptive field
Type I fibers: small receptive field..tell what exact point with a pin prick
Higher density type I fibers= better two point discrimination
small receptor field

Type II fibers: large receptive field ..tell something stuck ur finger but not specific spot

69
Q

How does receptor density affect info received

A

More receptors u have more clarity of image and information and info received.

70
Q

Stimulus Intensity VS Receptor Potential graph

A

Low stimulation ..u can tell the diff be heavy and light stimuli.
Mild stim we will tell discrete difference
When signal strength is high we will have the ability to diff pressure at the top range
there is no maxing out

71
Q

IN a Linear relationship between Stimulus Intensity VS Receptor Potential graph what will happen

A

There will be a maxing out and pain and thermal receptors are linear and they max out.

72
Q

How do we perceive stimulus

A

Spatial summation
-Multiple receptors firing in a small area at the same time and this depends on receptor density.

Temporal Summation
….how often does a fibre fire…

73
Q

Stimulus interpretation requires sensory coding

A

Sensory modality
Touch, pressure, flutter, vibration, cold, hot, pain, etc.
Taste, smell, position, vision, etc.
Spatial location
Population of neurons within a receptive field
Stimulus intensity
Frequency of AP, # of sensory receptors involved
Stimulus frequency
Temporal and spatial sumation
Interstimulus interval
Stimulus duration

74
Q

Explain the labeled line principle

A

Each nerve tract terminates at a specific point in the CNS and carries a selective sensory modality (i.e. low-threshold mechanoreceptors VS pain)
Sensation is perceived when a specific stimulated nerve leads to specific areas in the CNS (i.e. “separate dedicated cell populations in the thalamus and somatosensory cortex”)
Alteration of the specific nerve tracts activity will only change the intensity of the stimulus (quantitative)amount of pressure felt will b changed. VS changing the type of stimulus perceived (i.e. qualitative)
For example the sensation of pressure will change in intensity but it will not “turn into” the sensation of pain ( a different set of afferents will carry the nociceptive afferents).

75
Q

Sensory info is carried by 2 alternative pathways namely?

A
  1. Dorsal column- Medial Lemniscal

2. Anterolateral System

76
Q

Dorsal Column-Medial Lemniscal features

A

Highly Localized Touch sensations

Touch sensations (fine gradations of intensity)

Phasic sensations (vibratory)

Skin contact sensation
Joint position

Pressure sensations (fine gradations of intensity)

Composed of large myelinated fibers transmit
signals at rate of 30-110 m/sec

More spatial orientation
mechanofibres

77
Q

Anterolateral system

features

A 
Pain
Thermal sensations (warm/cold)

Crude touch and pressure

Tickle & itch

Sexual sensations

Composed of smaller myelinated fibers that transmit signals at a rate of 40m/sec
Less spatial orientation

78
Q

Dorsal Column Medial Lemniscal Pathway action

A 
Transmits signals upward to the medulla via the dorsal columns of the spinal cord in somatotopic fashion. 
 Signals synapse synapse in dorsal column nuclei
Nucleus gracilis (lower body/leg)
Nucleus cuneatus (upper body/arm)
 2nd order neuron axons (internal arcuate fibers) then cross to the opposite side of the medulla and project to the thalamus (3rd order neurons) via the medial lemniscus (pons, midbrain).
79
Q

The ANterolateral System

Spinothalamic

A

Enters the spinal cord from the dorsal spinal nerve roots, immediately synapses in the dorsal horns
Cross to the contralateral cord
Travel upward through the anterior and lateral white columns
Tracts terminate at all levels of the lower brain stem and in the thalamus

80
Q

Spinocerebellar Proprioceptive Pathway

A

Perception of position, conscious awareness of body movements & local reflexes
These pathways carry both cutaneous and proprioceptive information to cerebellum and cerebral cortex

81
Q

Central pain pathways

A

Aδ (fast, well localized pain) & C fibers (slow, dull, less localized) synapse in the gray matter of the dorsal horn of the spinal cord
Aδ at lamina I, V, and X
C at lamina I, and II

Central pain pathways
Spinothalamic
Spinoreticular
Spinomesencephalic

82
Q

Mechanism of Action of Moro Neurons

A

Function is Dependent on Intact Efferent Cellular Circuits.

Behavior (reflective & voluntary muscle movement or glandular secretion) is triggered by central neurons which activate motor neurons .

Upper motor neurons (brain) synapse on lower motor neurons (spinal cord or anterior root) whose axons leave the CNS to affect the periphery.

83
Q

What location is the motor neuron controlling somatic musculature located

A

Ventral horn of the spinal cord

84
Q

What location is the inter-neuron of the motor neuron located

A

Intermediate/lateral horn.

if they supply the axial muscle they are located in the medial ventral horn

85
Q

Descending Motor Pathways are ?

A

Lateral and Medial

86
Q

Lateral descending motor pathways

A

Lateral corticospinal, lateral corticobulbar tract, rubrospinal tract

Terminate in the lateral portions of the spinal cord gray matter.
Excite interneurons (primary) but can also excite motor neurons directly.

influence reflex arcs that control fine movement of the distal ends of limbs, as well as those that activate supporting musculature in the proximal ends of limbs.

87
Q

Medial descending motor pathways

A

Pontine/medullary reticulospinal tracts, vestibulospinal tracts, tectospinal tract

Terminate in the medial ventral horn on the medial group of interneurons
These interneurons connect bilaterally with motor neurons that control the axial muscles (balance and posture) and help control of proximal limb muscles.

88
Q

Corticospinal (pyramidal Tract)

A

Very fast signals Betz cells 70m/sec
Controls the limbs
voluntary skeletal movement controlling muscle in the trunk and proximal limb

ventral …trunk muscles
lateral…control limbs

89
Q

Blood supply to the brain are

A

2 vertebral arteries and 2 carotid arteries

allows collateral circuation

90
Q

Spinal cord blood supply

A

Lack of collateralization in the spinal cord

Artery of Adamkwitz can be cut off and there will be a problem

91
Q

Components of CSF

A

CNS “lymphatic system” & protection from mechanical force
Cavity enclosing the brain & spinal cord has capacity of ~ 1600-1700ml
~ 125ml is CSF (remainder brain & spinal cord)
~ 30 ml of CSF is in cerebral ventricles
Formed from choroid plexuses @ 0.35 ml/min
Reabsorbed by arachnoid villi – function like one way valves
fluid flows when CSF pressure is 1.5mmHg > than venous pressure

naCsf > nablood
148/145
Kcsf

92
Q

CSF flow

A

Fluid from lateral ventricles passes through intraventricular foramina (of Munro) to the third ventricle additional fluid is added and then it flows downward along the aqueduct of Sylvius into the fourth ventricle, more fluid is added and then it passes out of the fourth ventricle through three small openings two lateral foramina of Luschka, and a midline foramen of Magendie entering the cisterna magna ( a large fluid space that lies behind the medulla and beneath the cerebellum) which is continuous with the subarachnoid space surrounding the spinal cord

93
Q

Blood brain barrier structure

A

Tight junctions between CNS capillary endothelial cells.
Fenestrations in brain 1/8th size of fenestrations in other areas
Astrocytes also restrict movement (ex. by taking up potassium ions) and provide structural support.

Exists in tissue capillary membranes in all areas of the brain parenchyma except hypothalamus, pituitary, and area postrema

94
Q

Movement across BBB depends on what?

A

Movement across BBB depends on size, charge, lipid solubility, and degree of protein binding in the blood

95
Q

Permeable/slightly permeable and Impermeable things to the blood brain barrier

A

Permeable: H20, C02, O2, lipid soluble substances (anesthetics, ETOH)

Slightly permeable: Na, Cl, K, Ca, Mg

Impermeable: polar molecules, plasma proteins, glucose (facilitated diffusion only), non-lipid soluble large organic molecules (mannitol)

96
Q

ICP range

A

8-12

97
Q

What makes up the ICP

A

Rigid cranial vault fixed volume
Brain (cellular and ICF) (80%)
Blood (arterial and venous)(12%)
CSF (8%)

98
Q

calculate CPP

A

MAP-ICP or CVP
80-100(Normal)

grey matter flow is higher than white matter flow…more metabolic activity here.

below 50 is bad.

99
Q

Factors that will influence cerebral blood flow

A

Normal Adult 50ml/100g/min =750ml/mi

Factors impacting CBF
Level of arousal/neural metabolism 
Temperature
Concentration of  CO2 and H+ ions
 O2 (only when extremely low)
Blood Viscosity
Decrease in hematocrit will increase CBF but decrease O2 carrying capacity of the blood
Severe polycythemia can reduce CBF
100
Q

WHAT is Flow metabolism coupling

A

more activity…more action potential…na/k pump and Atp use…so blood flow higher.

Neuronal Activity (metabolism) and Local CBF

Metabolic by-products (glial, neuronal, vascular)
CBF to localized brain regions change up to 100-150% within seconds in response to local neuronal activity changes (sensory input/arousal)

101
Q

CBF and relationship with CO2

A

CO2 + H20 = carbonic acid
Carbonic acid disassociates into H+
H+ ions cause “almost” proportional vasodilation of cerebral vessels
Each 1 mmHg change in PaCO2
CBF changes approximately 1-2ml/100g/min
CBV changes 0.05ml/100g brain tissue
= 10 ml difference for 15 mmHg change
Effect lasts ~ 6hrs and then in will return to normal despite maintenance of altered CO2 levels (bicarb transport)

Blood and co2 level relate linearly…..
Co2 goes up….neuronal activity goes up.

102
Q

Brain metabolism

A

Only 2% of total body mass, 15-20% of total body metabolism and cardiac output

Cerebral Metabolic Rate (CMRO2) =
3-3.8ml/100g/min = 50ml/min of O2
Pediatric patients =5.2ml/100g/min

Brain not capable of much anaerobic metabolism (high metabolism coupled with low local glycogen and oxygen stores)
Brain glucose consumption 5.5mg/100g/min

103
Q

FYI

A

Energy consumption of teh brain is high,it is used mainly for used to support electrophysiologic function - meaning the depolarization repolarization (ionic gradient maintenance) and synthesis, transport and reuptake of neurotransmitters. The other 40% is just to maintain cell integrity.

104
Q

If PO2 of brain tissue drops below 30mmHg (35-45mm Hg normal) or PaO2 drops below 50-60mmHg

A

CBF increases

105
Q

How does the Auto-regulation of CBF & Arterial Blood Pressure happen

A

CBF auto-regulated really well between MAP of 70-150mmHG or 50-150
Cerebral vasculature adjusts to changes in CPP/MAP after 1-3 minutes
HTN will shift auto-regulatory range to higher minimum values and maximums of 180-200mmHg

106
Q

Review SLide 45

A

green,blue ,orange

107
Q

Does the autoregulation mechanism always override?

A

Yes,Neither transection of these nerves or mild to moderate stimulation causes much change

108
Q

When does The SNS kick in

A

May shift the auto-regulation curve to the right

SNS minor role unless sudden extreme BP rise (stroke prevention) or hemorrhagic shock

109
Q

Whats is the effect of temp with CBF

A

CBF changes 5-7% per 1 degree C change
Hypothermia decreases CBF and CMRO2
Hyperthermia opposite effect

Physiology (11 decks)

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