Counseling/Anatomy of the Brain and Neurosystem

Central nervous system, or CNS

 * skull
 * spine

Peripheral nervous system, or PNS

 * Outside skull and spine
 * Two divisions, external and internal

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

Somatic nervous system (SNS)
Relates to external environment

nerves

 * afferent -- sensory signals from:
 * skin
 * skeletal muscles
 * joints
 * eye, ears


 * efferent -- motor signals to:
 * skeletal muscles

Autonomic nervous system (ANS)
Regulates internal environment

nerves
Afferent and Efferent

afferent nerves

 * carry sensory signals from internal organs to CNS

efferent nerves

 * 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
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
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
electrochemical signals:
 * reception
 * conduction
 * transmission

external

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

internal
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

 * synaptic vesticules -- store neurotransmitters
 * neurotransmitters -- chemicals that influence post-synaptic cells

cell membrane

 * 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

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

bundles of axons:
 * tracts in CNS
 * nerves in PNS

glial cells
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

axis
anterior / posterior dorsal / ventral
 * front / back
 * front of brain, but upwards in body
 * 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

 * medial -- towards midline
 * lateral -- away from midline towards lateral, or outside, surfaces

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

sections

 * 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

gray matter

 * core
 * H-shaped
 * cell bodies
 * unmyelated neurons
 * horns
 * dorsal
 * ventral

white matter

 * surrounding
 * myelated axons (white lipid)

attached nerves

 * 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
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

 * tracts for signals between brain and body
 * also called medulla

rectiliniar formation
spans:
 * network of 100 tiny nuclei within central core of brain stem
 * 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
thalamus and hypothalmus

thalamus

 * 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

 * 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

 * 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
circuit of mid-line structures in brain

motivated behaviors members:
 * fleeing
 * feeding
 * fighting
 * sex
 * hippocampus
 * cingulate cortex

sub-cortical
 * mamillary bodies
 * amygdala
 * fornix
 * septum

basal ganglia

 * voluntary movement
 * sub-cortial structures

members:
 * amygdala
 * caudate (circle)
 * putamen (within circle, straitum with caudate)
 * globus pallidus