Neuro II White
Transcript of Neuro II White
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The Nervous System Part II - Chapter 12
Developmental Regions of Brain - originates from ectoderm
- Neural Groove which becomes Neural Tube by week 4 of gestation
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(a)
Neural
tube
(b) Primary brain
vesicles
Anterior
(rostral)
Posterior
(caudal)
Rhombencephalon
(hindbrain)
Mesencephalon
(midbrain)
Prosencephalon
(forebrain)
Figure 12.2a-b
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(d) Adult brain
structures
(c) Secondary brain
vesicles
Spinal cord
Cerebellum
Brain stem: medulla
oblongata
Brain stem: pons
Brain stem: midbrain
Diencephalon
(thalamus, hypothalamus,epithalamus), retina
Cerebrum: cerebral
hemispheres (cortex,
white matter, basal nuclei)
Myelencephalon
Metencephalon
Mesencephalon
Diencephalon
Telencephalon
Central canal
Fourth
ventricle
Cerebral
aqueduct
Third ventricle
Lateral
ventricles
(e) Adult
neural canal
regions
Figure 12.2c-e
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1. Prosencephalon = Forebrain
a. Telencephalon - Cerebrum - see lobes of cerebrum later in these notes.
b. Diencephalon
(1) Thalamus - major connection between the cerebral cortex to "lower" centers
of brain
- sorts out the information and sends it to the appropriate centers of the cortex
(2) Hypothalamus - major visceral control to regulate homeostasis
- regulates the Autonomic Nervous System - cardiac and smooth muscle
control
- emotional behavior
- thermoregulation
- hunger & thirst centers
- sleep/wake cycles & biological clock
- Endocrine control - produces "releasing" hormones which regulate the
pituitary gland
- memory
- Mammillary Bodies - relay signals for olfaction
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Figure 12.3d
Cerebellum
Diencephalon
Cerebral
hemisphere
(d) Birth
Brain stem
Midbrain Pons Medulla
oblongata
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(3) Epithalamus = Pineal Gland - biological clock
- produces serotonin by day & melatonin by night
- melatonin production increases w/ exposure to light and is related to our
biological clocks
- Seasonal Affective Disorder (SAD) & Premenstrual Syndrome (PMS) are
both associated w/ reduced melatonin levels - phototherapy used
2. Mesencephalon - Midbrain - contains Substantia Nigra which is damaged in
Parkinson's D in which sufficient quantities of Dopamine are NOT prodcuced by the
Substantial Nigra
- connects hindbrain to forebrain
- Corpora Quadrigemina = 2 superior colliculi (vision) + 2 inferior colliculi
(hearing)
3. Rhombencephalon = Hindbrain
a. Metencephalon
(1) Cerebellum - fine motor control & muscle coordination
(2) Pons - respiration, sleep, sensory functions, etc.
b. Myelencephalon - Medulla Oblongata - cardiac, vasomotor, respiratory centers
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- Lobes of Cerebrum
1. Frontal Lobe
- motivation, foresight, planning, memory, mood, emotion, social judgment,
aggression
- Primary Motor Cortex = Precentral Gyrus - axons to spinal cord to control
skeletal muscles
- Premotor Cortex - just anterior to precentral gyrus - for learned
motor skills
- Broca's Area - if damaged causes Expressive or Motor Aphasia - understand
the words but cannot speak them due to loss of relative motor abilities
- Aphasia = loss of speech
- Prefrontal Cortex - intellect, planning, behavior, emotions
- Frontal Lobotomy - surgical destruction of this area to alter criminally violent
behavior
- check out the story on Phineas Gage- just google it
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2. Temporal Lobe - hearing, smell, taste, balance, learning, memory, visual
recognition, emotional behavior
- Primary Auditory Cortex - superior margin of Temporal Lobe
- Olfctory Cortex - medial portion of Temporal Lobe
3. Parietal Lobe - sensory reception, taste, some vision
- Primary Sensory Cortex = Postcentral Gyrus from skin, muscles, joints,
tendons
- Wernicke's Area - Receptive Aphasia - the inability to recognize spoken &
written language
4. Occipital Lobe
- Primary Visual Cortex = Occipital Lobe
5. Insula -memory, addictive behaviour, language, taste, visceral sensory info
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CerebellumPons
Medullaoblongata
Spinal cord
Cerebral
hemisphere
(c) Week 26
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Postcentral
gyrus
Central
sulcus
Precentral
gyrusFrontal
lobe
(a)
Parietal lobe
Parieto-occipital sulcus(on medial surface
of hemisphere)Lateral sulcus
Transverse cerebral fissure
Occipital lobeTemporal lobe
CerebellumPons
Medulla oblongataSpinal cord
Cortex (gray matter)
Fissure(a deepsulcus)
Gyrus
Sulcus
White matter
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Central
sulcus
(b)
Frontal lobe
Temporal lobe
(pulled down)
Gyri of insula
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Parietallobe
Frontal lobe
Right cerebralhemisphere
Occipital
lobe
Left cerebralhemisphere
Cerebral veins
and arteriescovered by
arachnoid
mater
Longitudinalfissure
Poster ior (c)
Anter ior
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Left cerebralhemisphere
Transverse
cerebralfissure
Cerebellum
Brain stem
(d)
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- Limbic System - regulates emotions, learning, and gratification vs aversion
- Amygdaloid Body - the ability to evaluate potentially dangerous conditions - does
not mature until mid-late 20,s....think about it...hmmmm!
- Hippocampus - memory
- Fornix
- Cingulate Gyrus
- Right Cerebral Hemisphere - Right Brain - visual-spatial skills, intuition, emotion,
artistic & musical skills
- Left Cerebral Hemisphere - Left Brain - 90% of people, this side dominates
language, math, logic, rote memory - most people w/ left cerebral dominance are
right handed.
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- Basal Nuclei - motor control
(1) Caudate Nucleus
(2) Lentiform Nucleus
(a) Globus Pallidus
(b) Putamen
Reticular Formation - within Midbrain, Pons, and Medulla Oblongata
- regulate: muscle control for balance & posture
- cardiac and vasomotor centers in medulla oblongata
- pain regulation
- regulation of sleep vs consciousness - location for actions of general anesthetic
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- Electroencephalogram (EEG)
1. Alpha Waves - when awake & resting, "day dreaming" w/ eyes closed
2. Beta Waves - when mentally active, problem solving, and during sensory \
stimulation
3. Theta - in children & sleeping adults - indicate stress in awake adults
4. Delta - awake infants, adults in deep sleep - indicate serious brain damage in
awake adults
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Alpha wavesawake but relaxed
Beta wavesawake, alert
Theta wavescommon in children
Delta wavesdeep sleep
(b) Brain waves shown in EEGs fall into
four general classes.
1-second interval
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Memory - based on a series of new or modified synapses called the Memory Trace
Synaptic Plasticity - the ability to add or remove synapses. Adding synapses is how
we remember things.
Potentiation - the process that makes it easier to evoke a particular pathway that calls
up a certain memory. Potentiation develops by "training" the pathway of neurons thatbring about the memory.
- types of memory
(1) Immediate - retained for few seconds
(2) Short-Term - from seconds - hours.- Working Memory - only last long enough to carry out a task, then you forget it
- Tetanic Stimulation - repeated series of stimulations that cause memory to last a
few hours
- stimuli occur so quickly, 2nd neuron is facilitated i.e. it becomes easier to fire
- Posttetanic Potentiation - these cells remain so sensitive (for hours) they onlyneed the slightest stimulation to fire. These last two items remind me of
"cramming" for tests
(3) Long-Term - may last your entire life
- Long-Term Potentiation - process by which neurons are changed (synapses,
receptors, NT release, etc) resulting in long-term memory
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Meninges - also see lab handout
- covering of the brain
- Epidural Space-just outside of Dura
- Epidural Block - effects local spinal nerves only (between L3-4) as seen during labor
- Layers of Meninges
1. Dura Mater - thickest, outermost
2. Arachnoid Mater- middle layer
- Subarachnoid Space - filled w/ Cerebral Spinal Fluid (CSF)
- Choroid Plexuses - one in each ventricle produce CSF
- Arachnoid Granulations - remove CSF & return it to the blood at the Superior
Sagittal Sinus, preventing hydrocephalus
3. Pia Mater- innermost layer. Attached to brain & spinal cord
- Cerebrospinal Fluid (CSF) fills subarachnoid space so brain sort of floats in it.
During a spinal injection (or an epidural that went too far), if CSF leaks out, the brain
touches the cranium causing an intense headache known as a spinal headache.
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Superiorsagittal sinus
Arachnoid villus
Subarachnoid space
Arachnoid mater
Meningeal dura mater
Periosteal dura mater
Right lateral ventricle
(deep to cut)Choroid plexusof fourth ventricle
Central canalof spinal cord
Choroidplexus
Interventricularforamen
Third ventricle
Cerebral aqueduct
Lateral aperture
Fourth ventricle
Median aperture
(a) CSF circulation
CSF is produced by thechoroid plexus of eachventricle.
CSF flows through the
ventricles and into thesubarachnoid space via themedian and lateral apertures.Some CSF flows through thecentral canal of the spinal cord.
CSF flows through thesubarachnoid space.
3
CSF is absorbed into the dural venoussinuses via the arachnoid villi.
4
3
4
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Skin of scalpPeriosteum
Falx cerebri(in longitudinal
fissure only)
Blood vesselArachnoid villusPia materArachnoid mater
Duramater
Meningeal
Periosteal
Bone of skull
Superiorsagittal sinus
Subduralspace
Subarachnoidspace
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Spinal Cord
- ends in an enlarged region called the Medullary Cone or Conus Medularis
- ends between L1 - L2 but Dura Mater doesn't end until S2-S3
- take spinal taps/lumbar punctures or administer spinal anesthesia between L3-L4 to
miss the spinal cord
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Figure 12.30
Ligamentumflavum
Supra-spinousligament
Lumbar punctureneedle enteringsubarachnoidspace
Filum
terminale
Inter-vertebraldisc
T12
L5
Cauda equinain subarachnoidspace
Duramater
L5
L4
S1
Arachnoidmatter
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Figure 12.29a
Cervical
enlargement
Dura and
arachnoid
mater
Lumbar
enlargementConus
medullaris
Cauda
equina
Filumterminale
Cervical
spinal nerves
Lumbar
spinal nerves
Sacral
spinal nerves
Thoracic
spinal nerves
(a) The spinal cord and its nerve
roots, with the bony vertebral
arches removed. The dura mater
and arachnoid mater are cut
open and reflected laterally.
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Reflexes - Ch 13, pg 514 of 8th edition, pg 522 of 7th edition
circuit is:(1) sensory component (2) Spinal Cords (interneurons) (3) motor
component
- Muscle Spindle - stretch a muscle, this causes it to contract against the stretch
- Knee Jerk Reflex - by tapping the patellar ligament (was once part of quadriceptstendon), you stretch the tendon/muscle - msg to spinal cord to interneurons
then a motor msg back to the muscles of that tendon to contract - so, you tap the
ligament and the leg pops forward a little bit
- checks the circuit as well as the nervous system generally
- Golgi Tendon Organ - stretch a muscle/tendon too far, this sends inhibitory signal to
stop the contraction of the muscle to prevent over-stretching or tearing a muscle
- Withdrawal Reflexes - to avoid painful stimuli