Counseling/Anatomy of the Brain and Neurosystem

Central nervous system, or CNS

edit
  • skull
  • spine


Peripheral nervous system, or PNS

edit
  • Outside skull and spine
  • Two divisions, external and internal

PNS nerves project from spinal cord to organs (with exceptions)

Somatic nervous system (SNS)

edit

Relates to external environment

nerves

edit
  • afferent -- sensory signals from:
    • skin
    • skeletal muscles
    • joints
    • eye, ears
  • efferent -- motor signals to:
    • skeletal muscles

Autonomic nervous system (ANS)

edit

Regulates internal environment

nerves

edit

Afferent and Efferent

afferent nerves
edit
  • carry sensory signals from internal organs to CNS
efferent nerves
edit
  • carry motor signals from CNS to organs

two kinds:

  1. sympathetic
  2. parasympathetic

functions:

  • each organ, or autonomic target, receives opposing sympathetic and parasympathetic input
  • organ is controlled by level of sympathetic and parasympathetic activity

sympathetic

  • arousal
  • threatening situations
    • stimulate
    • organize
    • mobilize

parasympathetic

  • relaxation
  • conserve energy

location:

  • sympathetic project from CNS to lumbar and thoratic (chest) regions
  • parasympathetic project from CNS to brain and sacral (lower back) regions

nature: both have two stage neural paths that synapse on other neurons between organs and spinal cord

  • sympathetic synapse farther from organs
  • parasympathetic synapse nearer to organs

cranial nerves

edit

12 parasympathetic cranial nerves project from brain

purely sensory:

  • olafactory
  • optic

sensory and motor:

  • vagus nerves -- gut

disease diagnosis:

  • disruption of nerves can pinpoint tumors and other pathologies

CNS protection

edit

CNS tissue covering

  • meninges -- three membranes that cover CNS (meninx, singular)

cerebrospinal fluid (CSF) -- CNS cushion and physical support, single connected reservoir

  • sub-arachnoid space -- between inner and middle meninges
  • central canal -- runs length of spinal cord
  • ventricles -- four large internal chambers
    • 2 lateral
    • 3rd and 4th vertical

blood brain barrier:

  • tightly-packed blood vessels
  • filters passage of molecules by type
  • filters differently by location (sex hormones)

Neurons

edit

electrochemical signals:

  • reception
  • conduction
  • transmission

external

edit
  • membrane
  • dendrites
  • axon
    • axon hillock
  • myelin
  • nodes of ranveir
  • buttons -- ends of axons
  • synapses

internal

edit

common to all cells:

  • endoplasmic reticulum -- folded membranes
    • ribosomes (rough area) -- synthesis of proteins
    • smooth -- synthesis of fats (without ribosomes)
  • cytoplasm -- clear internal fluid
  • golgi complex -- packages molecules in vesticules (makes vesticules?)
  • micro tubules -- transport tubes

neural transmission

edit
  • synaptic vesticules -- store neurotransmitters
  • neurotransmitters -- chemicals that influence post-synaptic cells

cell membrane

edit
  • lipid bilayer -- membrane surfaces, inside and out
  • thru-membrane passages
    • channel proteins -- allow specific molecules to pass
    • signal proteins -- transfer signal from outside to inside when molecule binds on outside

classes of neurons

edit
  • multipolar (most common) -- two or more processes (axons/dendrites) extending from body
  • unipolar -- one process extending from body that can divide into multiple extentions
  • bipolar -- two processes extending from body
  • interneurons -- short, or no, axons conduct signals within a single brain structure

gross neural structures

edit

nuclei -- clusters of cell bodies in CNS ganglia -- clusters of axons in PNS

bundles of axons:

  • tracts in CNS
  • nerves in PNS

glial cells

edit

90% of brain cells, primarily support neurons

  • oligodendrocytes -- CNS
    • create myelin sheaths around
    • wrap around axons in CNS sending out extensions (does it stay connected, or release myelin?)
  • schwann cells -- PNS
    • create myelin sheaths
    • creates only one sheath and can regenerate myelin
  • astrocytes -- some in blood barrier system
    • transport chemicals from blood to neuron bodies
    • extensions cover blood vessels
    • connect to neuron bodies
  • micoglia -- respond to injury or disease
    • engulf cellular debris
    • trigger inflammatory responses

Directional references

edit

axis

edit

anterior / posterior

  • front / back
  • front of brain, but upwards in body

dorsal / ventral

  • top / bottom
  • dorsal is top of brain, but back of body
  • ventral is bottom of brain, but front of body

superior -- top

inferior -- bottom

in / out

edit
  • medial -- towards midline
  • lateral -- away from midline towards lateral, or outside, surfaces

far / close

edit

distal -- far from CNS proximal -- close to CNS

sections

edit
  • sagittal -- vertically divides left and right
  • frontal -- vertically divides front and back
  • horizontal -- divides top and bottom
  • cross section -- cut across nerve or spinal cord

Spinal cord

edit

gray matter

edit
  • core
  • H-shaped
  • cell bodies
  • unmyelated neurons
  • horns
    • dorsal
    • ventral

white matter

edit
  • surrounding
  • myelated axons (white lipid)

attached nerves

edit
  • 31 pairs of nerves attached
    • left and right (bundles of axons)
  • axons go to ventral and dorsal horns
  • sensory neurons (unipolar) go to dorsal horns with bodies outside in nerve bundle forming dorsal root ganglia
  • motor axons emerge from ventral with neuron bodies in horn
    • somatic project to the skeletal system
    • autonomic connect to ganglia (clusters of cell bodies) that synapse on neurons that connect to organs

Brain

edit

5 divisions from top to bottom:

  • telenephalon
  • diencephalon
  • mesencephalon
  • metencephalon
  • myenlencephalon (medulla)

spinal cord is beneath myenlencephalon

From 3 sections:

  • forebrain, telenephalon and diencephalon
  • midbrain, mesencephalon
  • hindbrain, metencephalon and myenlencephalon

myenlencephalon

edit
  • tracts for signals between brain and body
  • also called medulla

rectiliniar formation

edit
  • network of 100 tiny nuclei within central core of brain stem

spans:

  • posterior boundary of myelencephalon (bottom of medulla)
  • anterior boundary of mesencephalon (top of midbrain)

rectiliniar activation system:

  • sleep
  • attention
  • movement
  • muscle tone maintenance
  • heart beat
  • circulation
  • respiratory reflexes

diencephalon

edit

thalamus and hypothalmus

thalamus

edit
  • 2 lobes joined by massa intermedia
  • top of brainstem
  • on top of third ventricle
  • pairs of nuclei that project to cortex (most)
  • sensory relay nuclei (many)
    • receive signals from sensory receptors
    • process signals
    • transmit to specific areas of sensory cortex

lateral geniculate nuclei visual sensory relay nuclei

hypothalamus

edit
  • below (hypo) thalamus
  • regulation of motivated behaviors
    • regulates release of hormones from pituitary gland (attached below/front)

attached structures:

  • pituitary gland
  • optic chasm
    • decussate or contralateral (cross over to other side)
    • ipsilateral (staying on same side)
  • mammilary bodies
    • behind pituitary

telencephalon

edit
  • largest division
  • voluntary movement initiation
  • interprets (processes) sensory movement
  • mediates complex cognitive processes
    • learning
    • speaking
    • problem solving

cerebral cortex

also cortex

  • layer of tissue
  • convoluted, or furrowed
      • increase amount of cerebral cortex from same tissue mass

convolutions:

  • fissures, large furrows
  • singular suclcus, small furrows
  • gyri, ridges between fissures

longitudinal fissure:

  • separates hemispheres
  • largest fissure
  • connections between hemispheres (tracts)
    • cerebral commisures
    • largest, corpus callosum
    • minimal number of tracts

lateral fissure: major horizontal fissure

four lobes divided by horizontal and latteral fissures:

  • frontal
  • parietal
  • temporal
  • occipital

major gyri:

  • precentral, contain motor cortex
  • postcentral, somatosensory cortex (body sensation)
  • superior temporal gyri, auditory cortex

neocortex:

  • 6-layered cortex
  • 90% of cortex
  • evolutionary recent
  • numbered I through VI

two types of neurons:

pyramidal

  • multipolar
  • large
  • apex runs to surface of cortex
  • long axon

stellate

  • interneurons
  • star-shaped
  • small with short or no axon

non-neo cortex

  • fewer layers
  • hippocampus
    • memory
    • medial edge of cerebral cortex
    • curves back on itself in medial temporal lobe
  • cingulate cortex


limbic system

edit

circuit of mid-line structures in brain

motivated behaviors

  • fleeing
  • feeding
  • fighting
  • sex

members:

  • hippocampus
  • cingulate cortex

sub-cortical

  • mamillary bodies
  • amygdala
  • fornix
  • septum

basal ganglia

edit
  • voluntary movement
  • sub-cortial structures

members:

  • amygdala
  • caudate (circle)
  • putamen (within circle, straitum with caudate)
  • globus pallidus