# 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:
* sympathetic
* 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

## Directional references
#### axis

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

* 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

## 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

* 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

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
* fleeing
* feeding
* fighting
* sex
members:
* 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