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)
editRelates 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)
editRegulates internal environment
nerves
editAfferent 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:
- 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
edit12 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
editCNS 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
editelectrochemical signals:
- reception
- conduction
- transmission
external
edit- membrane
- dendrites
- axon
- axon hillock
- myelin
- nodes of ranveir
- buttons -- ends of axons
- synapses
internal
editcommon 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
editnuclei -- clusters of cell bodies in CNS ganglia -- clusters of axons in PNS
bundles of axons:
- tracts in CNS
- nerves in PNS
glial cells
edit90% 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
editaxis
editanterior / 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
editdistal -- 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
editgray 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
edit5 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
editthalamus 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
editcircuit 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