Anp Unit 3

Common CNS misconceptions

we only use 10% of brains

brain is supercomputer

listening to classical music increases intelligence

discrete limit to memories that can be stores

male and females process differently

CNS Operational

sense internal and external enviorment

specific and general controls of cell activites

control ranges from fast to slow

top down

nerurons with same process in same space

plasticity

chemically separate from blood and protected by bone and connective tissue

CNS

brain and spinal cord

physically separate from PNS from BBB

Afferent neurons

inward axonal projections

sensory

Efferent Neurons

outward axonal projections

motor

CNS compositions

10% neurons 50% volume

90% neuroglia 50% volume

nucleus

cluster of neuronal cell bodies in CNS

ganglion

Cluster of neuronal cell bodies in PNS

Grey matter

rich in neuronal cell bodies, dendrites, synapses

closer to surface

White matter

rich in myelinated axons

deep to grey matter

Circuts

anatomical and functional connections between neurons

Multipolar neurons

common CNS neuron with single axon and short dendrites

Pyramidal neurons

common

largest CNS neurons

multiple long axons and long dendrites

chart

CNS needs chemical isolation from rest of the body and from blood. Why?

needs stable environment because neurons are sensitive to ion changes. Blood also changes constantly.

Common ideas

Cranial bones provide protections against mechanical forces

CNS covered in meninges which are multiple layer connective tissue

isf - interstitial space fluid

csf - cerebral spinal fluid

bbb - blood brain barrier

Dura Mater

outermost

tough mother

made of 2 fibrous layer

space between has blood vessels, extracellular fluid, and lymphatic vessels

subdural space - between dura and arachnoid

dural venous sinus - drainage system allows CSF to re enter blood

Subdural Hematoma

Physical trauma leds to bleeds into brain surface

increased fluid pressure leads to neuronal cell damage

MRI

Arachnoid Mater

between layer

spiderlike mother

has epithelial layer that does not follow the sulci and gyri of brain

subarachnoid space - between dura and pia

Arachnoid villi move through venous sinuses allowing CSF to exit subarachnoid space

Pia Mater

Gentle mother

on surface of brain

accompanies branches of cerebral blood vessels

coverage and protection of CNS tissue. blood vessles

meningittis

Meningittis

viral or bacterial infection leading to pia matter inflammation

cause headaches

Vascularization

brain has 15-20% cardiac output

internal carotid and vertebral arteries supply along with internal jugular vein

anastomose

fusion of blood vessels

Circle of Willis

alternative path for blood flow

ensures blood supply in the face of blockage

Brain Interstitial System

Fluid filled space between neurons and capillaires

has ISF and EM

15-20% of brain volume

not ISF outside CNS

Originate from CSF and blood vessels

Immediate environment surrounding neurons

Blood Brain Barrier

Made of capillary endothelial cells in tight junctions with basal lamina, astrocytic endfeet, pericytes

is highly selectively permeable with limits paracellular path and control of ISS

Neurovascular Unit

has capillary endothelial cells, pericytes, astrocytes, microglia, neurons

Regulation of blood flow and BBB

Blood Brain Barrier Transport

Limited transport capacity

carrier mediated - selective and saturable, aa glucose nucleotides

Receptor mediated - binding and internalization; hormones growth factor

Hydrophobic molecules: diffusion

lipid soluble come through water soluble do not

adsorptive transcytosis - fuse with membranse come out other end in vessicle

CSF acess

Hydrophobic diffusion is very fast so hydrophilic drugs have limited acess and bacterial infections are rare

ISF vs Plasma

ISf has lower Ph, protien content, buffering, glucose, K, HCO3

CNS very sensitive to changes in plasma CO2

CO2 levels

decreased medullary extracellular PH and increased phrenic nerve activity

CSF

located around and within CNS

Source of water an dolsutes for ISF

Gives brain boancy, protection against trauma, ISF functional stability and removes waste

made via ependymal cells lining ventricles

Ependymal cells

line ventricles

form choroid plexus with capillaries

secretion and movement of CSF

CSF Pathway

Ventricle choroid plexus

exits 4th ventricle via paired lateral apparatus of lone median aperture

flows thorugh subarachnoid

into arachnoid vili

drains into dura venous sinuses

CSF composition

More like ISF than plasma

plasma has more protien and K+

500 ml per day

150 ml at one time

Sleep and CSF

Sleep triggers rhythmic alternating slow waves of blood and CSF

operational dynamic

Neuroglia

>50% volume and 90% cells in CNS

are the internal environment responsible for communication, guiding axons, making synapses, bbb, remove waste, make CSF and myelin, generate electrical currents, and take up NT and ions

Oligodendrocytes

myelin production

regulational axonal growth

cerebral palsy - loss of oligodendrocutes

Astrocytes

most abundant

multiple types

provides surface coverage, limits solute into ISF

Part of BBB

Regulation of CSF content

Microglia

specialized macrophages

removal of debris, cells, foreign

Radial Glia

scaffolding in which new neurons migrate

Circuitry

based on synaptic connections between cells

vary from simple to complex

made during fetal stage

emergent - consciousness

Convergent Circuit

many axons to one target neuron

intergate electrical info

trade sensitivity over spatial info

Divergent Circut

one axon project to many cells

skeletal muscle

coordinated activities of multiple cells

Rhythm Generating Circuit

central pattern generator with minimum of 2cells

complex movement with few cells like running breathing

Complex Circuits

emergent properties and unpredictable

whole is greater than parts

human consciousness

Circuit Formation

multiple levels

10^14 connections

each neuron has 7000 connections

Process of forming circuit

axon guided to right spot during fetal development

state function: right connection at the right time under right conditions

EM has attractive and repulsive proteins and cells

this is why repair of spinal cord is hard

Growth cone helps be guided through chemotaxis of proteins and chemicals

Growth Cone Filopodia

membrane projection based on chemical cues

attract: both release Ca

repel: only external release Ca

Circuit Physiology

neuronal circuits develop during fetal and neuronatal growth

maintained by use

plasticity - changeable

wiring dictates functionality

complex behaviors are generated by simple circuits

Hemispheric Specialization

The left and right halves of your brain handle different jobs (like logic vs. spatial reasoning), but this specialization happens down at the cellular/circuit level rather than a major structural difference.

Uniform Signals, Diverse Functions

Even though every single neuron fires using the exact same basic electrical mechanism (ion fluxes across the membrane), complex groups of neurons can be assigned to completely different tasks depending on how they are wired.

Computational Power = Brain Volume

Harder tasks require more brain power, which is why larger areas of brain volume are dedicated to complex processing like vision.

Top-Down Control

the brain doesn't just react; it actively modifies and oversees activities happening down in the spinal cord.

SRMI

structural imaging

located differences in water content to outline shapes

examines shape not function

determine correct structure vs somthing wrong

Diffusion Tensor Imaging

structural

how water travels along axonal projections in brain brownian motion

info about neuron interconnectivity

Fmri

functional

past - association of brain trauma in region with change in physiology ie phinneas

now: measure small changes in blood flow different brain activities

EEG

functional

electrical brain activity with scalp electrodes

Phineas Gage

iron rod destroyed left frontal lobe

personality changes, loss of restraint

CNS common infections

need ct or mri that helps detect small bleeds

meningitis has high resolution and differentiates tissues

Brain mapping

normal surface structure

longitudinal fissures: left and right lobes

Latitudinal: top and bottom

has gyri/ridges sulci/valley and fissures

names for overlaying bones

Cerebrum

largest

cerebral cortex is outer layer

neocortex is largest part with 90% brain volume

higher level processing and cognition

Brainstem

autonomic and reflex center

Cerebellum

little brain

movement coordination

Diencephalon

homostatic control centers

Contralateral control

right side brain controls left side body and vice versa

Frontal lobe

motor speech memory formation personality and emotion

frontal cortex has : prefrontal, motor, and broccas area

Parietal lobe

somatosensory cortex

touch, taste, sight, smell

collection of info from multiple sources

proprioception: awareness of physical structures in #D space

Occipital lobe

visual processing and visual memories

primary visual cortex in back

visual association area to interpret info from cortex just before it

Temporal lobe

hearing speech language smell

passage of time - grey hair here

orginazation and language comprehension

memory formation and retreival

Primary motor cortex

back of frontal lobe

motorneurons betz cells that controls striated muscle

volume of area is indicative of control

middle finger neurons near pinky neurons

Myotome

PMC

representation of motoneurons controlling muscles on different regions of the body

Somatosensory cortex

sensory input from thermal, touch(mechanoreceptors), proprioception, pain

Hommunculus: visual representation of how much of cortex used by what

inputs from contralateral cord and thalmus

integration

Werinicke’s area

temporal lobe

speech comprehension

Wernicke’s aphasia

cant understand words and communicate

Brocas area

frontal lobe

helps speak

Primary language areas

broca

wernicke

angular gyrus which is superior edge of temporal lobe

arcutate fasiculus which is axonal tracts connecting broca and werinick allowing for coordination

Aphasia

cant comprehend or formulate languaue

many types

Brain Lateralization

left for language math reasoning logic

right for spatial, face recog, visual, music

caused by minute temporal delays in other hemispshere neuronal cells

CNS fibers

CNS made of interconnecting neurons

White matter

myeling coated axon projections

Projection

connects subcortical regions: telecenphalon, diencephalon, brain stem, spinal cord

commissural

connections between lobes

association

connections within lobes