Neuro II White

7/24/2019 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


9/25Figure 12.3c

CerebellumPons

Medullaoblongata

Spinal cord

Cerebral

hemisphere

(c) Week 26


10/25Figure 12.6a

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


11/25Figure 12.6b

Central

sulcus

(b)

Frontal lobe

Temporal lobe

(pulled down)

Gyri of insula


12/25Figure 12.6c

Parietallobe

Frontal lobe

Right cerebralhemisphere

Occipital

lobe

Left cerebralhemisphere

Cerebral veins

and arteriescovered by

arachnoid

mater

Longitudinalfissure

Poster ior (c)

Anter ior


13/25Figure 12.6d

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


17/25Figure 12.20b

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.


20/25Figure 12.26a

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


21/25Figure 12.24

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

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