superior/cranial
towards head end of body; upper
inferior/caudal
away from the head; lower
anterior/rostral
front (in rat, towards nose)
posterior/caudal
back (in rat, towards tail)
dorsal
back (in rat, towards spine)
ventral
front (in rat, towards belly)
midline
runs down middle of nervous system
medial
towards midline of body
lateral
away from midline of body
ipsilateral
two structures on same side of midline
contralateral
opposite sides of midline
midsagittal plane
split brain into equal right and left halves, rostral to caudal
sagittal plane
sections parallel to mid-sagittal plane
horizontal plane
parallel to ground
coronal plane
perpendicular to ground and sagittal plane, splits brain into anterior and posterior parts
cerebrum
rostral most and largest part of brain; right hemisphere receives sensations from and controls movements of left side; left hemisphere monitors sensations and movement from right side of body
deep sagittal fissure
splits cerebrum down the middle into two cerebral hemispheres
cerebellum
behind cerebrum; movement control center with extensive connections to cerebrum and spinal cord; left side cerebellum coordinates movements on left side of body; right side cerebellum coordinates movements on right side of body; though smaller, contains as many neurons as entire cerebrum
brain stem
fibers and cells relay information from cerebrum to spinal cord and cerebellum and vise versa; site where vital functions are regulated (breathing, consciousness, body temperature); damage to brain stem is usually fatal
spinal cord
attached to brain stem, encase in bony vertebral column; conduit of information from skin, joints, and muscles of body to the brain and vise versa; transection of spinal cord results in paralysis caudal to cut (muscles function but cannot be controlled by brain)
spinal nerves
how spinal cord communicates with body, exist spinal cord through notches between vertebra
dorsal root: brings information into spinal cord, sensory
ventral root: carries information away from spinal cord, motor
somatic PNS
spinal nerves that innervate skin, joints, and muscles under voluntary control
somatic motor neurons
command muscle contraction; derive from motor neurons in ventral spinal cord; cell bodies lie in CNS but axons lie in PNS
somatic sensory axons
innervate and collect information from skin, muscles, and joints, enter spinal cord via dorsal roots
dorsal root ganglia
somatic sensory cell bodies lie outside spinal cord in clusters; one for each spinal nerve
visceral PNS
involuntary, vegetative, or autonomic nervous system; consists of neurons that innervate internal organs, blood vessels, and glands and bring information about visceral function to CNS
visceral motor fibers
command contraction and relaxation of smooth muscles, rate of cardiac muscle contraction, and secretory function of glands
afferent neurons
bring information into CNS
efferent neurons
emerge from CNS to innervate muscles and glands
cranial nerves
12 pairs arise from spinal cord and innervate head; numbered anterior to posterior
I. olfactory
special sensory axons; sensation of smell
II. optic
special sensory axons; sensation of vision
III. oculomotor
somatic motor and visceral motor axons; movements of eye/eyelid and parasympathetic control of pupil size
IV. trochlear
somatic motor axons; movements of eye
V. trigeminal
somatic sensory and somatic motor axons; sensation of touch to face, movement of muscles of mastication
VI. abducens
somatic motor axons; movements of eye
VII. facial
somatic motor, special sensory axons; movement of muscles of facial expression and sensation of taste in anterior two-thirds of tongue
VIII. auditory-vestibular
special sensory axons; sensation of hearing and balance
IX. glossopharyngeal
somatic motor, visceral motor, special sensory, and visceral sensory axons; movement of muscles in throat, parasympathetic control of salivary glands, sensation of taste in posterior 1/3 of tongue, detection of blood pressure changes in aorta
X. vagus
visceral motor, visceral sensory, and somatic motor axons; parasympathetic control of heart, lungs, and abdominal organs; sensation of pain associated with viscera; movement of muscles in throat
XI. spinal accessory
somatic motor axons; movement of muscles in throat and neck
XII. hypoglossal
somatic motor axons; movement of tongue
meninges
three membranes protecting CNS from overlying bone
dura mater
“hard mother”, outermost covering; tough, inelastic bag surrounding brain and spinal cord
arachnoid membrane
under dura, has appearance and consistency resembling a spider web
subdural hematoma
ruptured blood vessels passing through dura are ruptured, blood collects and disrupts brain function due to compression of CNS
pia mater
“gentle mother”, thin membrane adheres to brain surface; many blood vessels dive into brain surface; separated from arachnoid by subarachnoid space filled with salty clear liquid (CSF)
ventricular system
fluid filled caverns and canals inside brain
choroid plexus
produces cerebral spinal fluid (CSF) in ventricles of cerebral hemispheres
flow of CSF
choroid plexus in lateral ventricles → interventrical foramina → third ventricle → cerebral aqueduct → fourth ventricle → median aperture → subarachnoid space → absorbed by blood vessels at arachnoid villi
gray matter
generic term for a collection of neuronal cell bodies in CNS
cortex
collection of neurons that form a thin sheet, usually at brain’s surface
nucleus
distinguishable mass of neurons, deep in brain
substantia
related neurons deep within brain, usually with less distinct border than those of nuclei
locus
small, well-defined group of cells
ganglion
collection of neurons in peripheral nervous system
nerve
bundle of axons in PNS
white matter
collection of CNS axons
tract
collection of CNS axons with common site of origin and common destination
bundle
collection of axons that run together but do not necessarily have same origin and destination
capsule
collection of axons connect cerebrum with brain stem
commissure
collection of axons that connect one side of brain with other side
lemniscus
tract meanders through brain like ribbon
sulci and gyri formation
result from expansion of cerebral cortex expansion during fetal development, which folds and wrinkles to fit into skull
cerebral cortex
thin sheets of neurons just under surface of cerebrum, parallel to brain surface; human reasoning and cognition: lack of cerebral cortex is blind, deaf, dumb and unable to initiate voluntary movement
cerebral cortex layer I
layer of neurons closest to surface (most superficial cell layer), separated from pia mater by a zone that lacks neurons
cerebral cortex apical dendrites
one cell layer contains pyramidal cells that extend to layer one to form branches
deep central sulcus
marks posterior border of frontal lobe, caudal to which lies the parietal lobe
frontal lobe
“action cortex”, emotion center, reasoning
parietal lobe
integrating sensory information
insula
sensation of pain is judged
occipital lobe
visual processing center
temporal lobe
sensory processing, long-term memory and modulation
hippocampus
medial to lateral ventricle; single cell layer; learning and memory; spatial memory and consolidation of declarative memory
amygdala
emotional learning, fear and behavior
corpus callosum
connects hemispheres
cingulate gyrus
links motivational outcomes to behavior
fornix
output tract on hippocampus (learning and memory)
thalamus
major sensory relay center
hypothalamus
body homeostasis, hormones release
pineal body
melatonin
midbrain
relay center, substantia nigra
pons
regulation of respiration, control of involuntary actions
medulla
transmitting signals between spinal cord and the brain, controls autonomic activities such as heartbeat and respiration
olfactory cortex
continuous with olfactory bulb; connected ventrally and laterally; two cell layers (connected to olfactory bulb, sits further anterior)
rhinal fissure
separates olfactory cortex from neocortex
neocortex
neocortex only found in mammals; cytoarchitectural map of neocortex divides into different zones; brodmann proposed that neocortex expanded by insertion of new areas
primordial neocortex of common mammalian ancestor
primary sensory areas, secondary sensory areas, motor areas
primary sensory areas
first to receive signals from ascending sensory pathways
secondary sensory areas
heavy interconnections with primary sensory areas
motor areas
intimately involved with control of voluntary movement; receive inputs from thalamic nuclei that relay information from basal telencephalon and cerebellum, send outputs to motor control neurons in brain stem and spinal cord
association areas
areas in frontal and temporal lobes remaining after primary/secondary sensory areas and motor area; more recent evolutionary development
flavor detection
unique combination of distinct tastes; flavors result from simultaneous taste and smell; sensory modalities such as temperature, texture, and pain sensations
organs of taste
tongue, palate, pharynx, epiglottis
papillae
small ridge, pimple or mushroom projections containing 1-several hundred taste buds; each taste bud has 50-150 taste receptor cells; each papilla has multiple types of taste receptor cells
taste receptor cells
apical end: near tongue surface, chemically sensitive part with microvilli that extend into taste pore
form synapses with endings of gustatory afferent axons near the bottom of the taste bud; electrical and chemical synapses onto basal cells which many then synapse onto sensory axons to form simple information-processing circuit within each taste bud
taste receptor membrane potential
voltage shift (depolarization) when appropriate chemical activates taste receptor may fire action potential, triggering synaptic transmission from taste cell to sensory axon and ultimately to brain stem
taste receptor transmitters
acetylcholine, GABA, glutamate: unknown functions
ATP: umami, sweet, bitter taste cells
serotonin: sour, salty