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introduction: CNS organisation & neurons, . ( (, ), (, )), other…
introduction: CNS organisation & neurons
"geography" of the brain & spinal cord
medial-lateral
anterior-posterior
rostral-caudal is traditional European terminology
ventral-dorsal
the mammalian brain
tend to do a lot of study on the way the nervous system works in animals as difficult to do in humans
human brain is significantly more complex than other mammals or rodents
human brain is much bigger, more gyri and sulci etc.
function specialisation in the cerebral cortex
frontal lobe in front of central fissure (sulcus)
memory & movement
parietal lobe behind frontal lobe
somatosensory
temporal lobe below parietal lobe
speech and hearing
occipital love at the back of the head
vision
association cortex between parietal, temporal, occipital lobes
complex behaviours, thinking
forebrain
cerebral cortex
corpus callosum
amygdala
pituitary gland
limbic structures
hippocampus
thalamus
hypothalamus
midbrain
midbrain
pons
cerebellum
medulla oblongata
structure of the spinal cord
dorsal root on each side conveys sensory information to the spinal cord
ventral root conveys motor commands to the muscles
sensory nerve
motor nerve
grey matter surrounded by white matter
autonomic innervation
each organ recieves innervation from sympathetic and parasympathetic fibers
sympathetic chains along side of spinal cord
cervical
dilates pupil
inhibits salivstion
relaxes bronchi
accelerates heart
thoracic
inhibits digestive activity
stimulates glucose release by liver
lumbar
secretion of epinephrine and norepinephrine from kidney
relaxes bladder
contracts rectum
parasympathetic localised to relevant organs
constricts pupil
stimulates salivation
.
inhibits heart
constricts bronchi
stimulates digestive activity
relaxes rectum
contracts bladder
relaxes rectum
fibers of both divisions meet & commingle at plexuses to innervate organs close to those centers
names of plexuses derived from locations or organs involved
the ganglia
singular - ganglion
in the PNS
- discrete collections of cell bodies and supporting glia
sensory
dorsal root ganglia line up along outside of spinal cord in a chain
cranial nerve sensory ganglia
autonomic
sympathetic - found in chains next to the spinal cord
parasympathetic - ganglia closer to organs
in the CNS
some brain regions referred to as ganglia
i.e. the basal ganglia (neurons which perform functions in midbrain and hindbrain
organisation of the nervous system
central
brain
forebrain
midbrain
hindbrain
spinal cord
peripheral
autonomic
sympathetic (arousing)
reciprocal inhibition
parasympathetic (calming)
sensory/motor
the human brainstem
composite structure that extends from the top of the spinal cord into the centre of the forebrain
the pons, pineal glad, and colliculi are ordinarily surrounded by the cerebral cortex
structures
pineal gland
thalamus
superior colliculus
inferior colliculus
textum
tegmentum
pons
medulla
types of cells in the nervous system
nerve cells - neurones or neurons
convey information
anatomy of a neuron
dendrites - input
can be 1000s of inputs to one cell body
short extensions that receive signals
soma (cell body)
decision making
graded potential
functional portion
has nucleus, mitochondria, nissil bodies
axon hillock
initiation of action potential
connects soma to axon
axon
transmits action potential
long extension that transmits impulses
axon terminals
multiple endings/neuron
end of cell
connects to next cell
synapses
communication with target cells
gap between axon terminal and next cell
machinery to create and release neurotransmitters
neurotransmitters - chemical 'messages' diffuse across synapse from presynaptic axon terminal to postsynaptic dendrite
lots of mitochondria in presynaptic component - process of generating neurotransmitters requires a lot of energy
electrical information is transformed at the synapse
there are different types of signals
electrophysiology
receptor potentials
synaptic potentials
action potentials
principle of connectional specificity
information conversions
between chemical (or physical) and electrical
chemical messengers are neurotransmitters
electrical signals require ion channels
these conversions occur across synapses
stimulus
sensory reception
sensory filtering
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classifying neurons
classification based on dendritic and somatic morphologies
stellate cells (star shaped) and pyramidal cells (pyramid shaped)
spiny or aspinous
based on shape can be classified as
unipolar
bipolar
multipolar
nerve cells can be distinguished on the basis of shape
sensory neuron
motor neuron
local interneuron
most common in vertebrates
projection interneuron
neuroendocrine cell
model neuron
information generally flows from dendrite to axon
can be classified by role
sensory
afferent
bring information in (senses and muscles)
motor
efferent
command muscles and glands
interneurons
coordinate
local
relay or project interneurons
information is sent to various cells and can result in mechanical action
aka reflex arc
polysynaptic reflex arc
receptor cell
afferent sensory neuron
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nerve cells working in systems can converge or diverge
divergence
usually sensory
.
convergence
usually motor
glial cells
support, help convey information
can be divided into macroglia and microglia
macroglia include
oligodendrocytes
convey information
astrocytes
Schwann cells
related to myelination (sheath around axon of neuron)
microglia are resident macrophages, originally from the blood
nerve packaging
connective tissue coverings of peripheral nerves
endoneurium
surrounds peripheral (myelinated) nerve fibre
fibre made up of neurilemmal (myelin) sheath formed by neurolemma(schwann) cells
surround axon
perineurium
surrounds fascicle (bundle of fibres)
epineurium
outer layer with blood vessels supplying nerve (vasa nervorum)
.
other sensory input
past experience
