Neuroscience Flashcards
what is parenchyma?
functional neural tissue
Neurons and Glia
what are the directional terms for the brain?
- rostral = anterior
- caudal = posterior
- ventral = inferior
- dorsal = superior
what are the different structures on a neuron?
- dendrites
- soma (cell body)
- axon hillock
- axon
- axon terminal
- synapse
where does a neuron receive afferent input?
at the dendrite and soma
mechanical/chemical stimuli open channels on the dendrite and soma to generate a graded potential
what types of stimuli can effect a neuron?
- mechanical (sensor/receptors like stretch receptors = baroreceptors )
- chemical (neurotransmitters)
T/F: a graded potential is always excitatory?
FALSE
can be excitatory, inhibitory, depolarizing, hyperpolarizing
define spatial summation
summing of graded potentials from 2 separate inputs/terminals
define temporal summation
summing a graded potential from one single terminal/input
ex: very intense stimuli like hitting thumb with hammer
what is the axon hillock?
trigger zone for action potential
regin at base of axon connected to soma
what are axon terminals?
final destination for the AP traveling down an axon
generally many axon terminals assocaited with a single axon due to collateral and terminal branching
T/F: a single AP generated at the axon hillock reaches all axon terminals?
TRUE
what are the types of axonal transport?
- fast anterograde
- slow anterograde = axioplasmic flow
- fast retrograde
what is fast anterograde axonal transport?
the movement of proteins associated with vesicles from the golgi apparatus in the soma to synaptic terminals
(peptide NT, enzymes, and membrane proteins)
what occurs during slow anterograde axonal transport?
movement of solube cytoskeletal, proteins from soma to axon terminals
*stop and go microtubule transport
what occurs during fast retrograde axonal transport?
movement of endocytosis vesicles from axon terminals to soma
Nonstop microtubule transport
(recycled membrane, chemical messengers, pathogens)
what axon structural factors impact signal conduction velocity?
fiber diameter (bigger = faster)
thickness of myelin (thicker = faster)
what are the different conduction velocity classifications of axons?
Type A, B, C from fastest to slowest
what are the different fiber diameter classifications for axons?
Type I, II, III, IV from biggest to smallest
What are the different functional types of neurons?
- Sensory - carry afferent signals from sensory/receptors to CNS (brain and spinal cord)
- Motor - carry efferent signals to effectos (muscles and glands)
what are the subtypes of sensory neurons?
- special sensory
- viscerosensory
- somatosensory
what are the special senses?
- vision
- auditory
- equilibrium
- olfaction
- gustatory
what are viscerosensory neurons?
single neurons from interoreceptors to subcortical CNS
relfexes that maintain homeostasis (BP, temp)
what are somatosensory neurons?
single neuron from skin, muscle, and joint receptors to cortex
touch, pressure, pain, proprioception, tempature (highly localized)
which sensory neuron is unconscious?
viscerosensory
what are the subtypes of motor neurons?
- somatomotor
- autonomic motor
which motor neuron subtype is a single neuron pathway and generally under conscious control?
somatomotor
T/F: Autonomic motor neurons are 2 neuron pathways
TRUE
involuntary and run from CNS to smooth muscle, cardiac muscle or glands
what are the differnet types of autonomic motor neurons?
- sympathetic
- parasympathetic
- associative (interneuron)
What are the different types of structural neurons?
- multipolar
- bipolar
- pseudo-unipolar
what are multipolar neurons?
soma with a single axon and multiple dendrites
common in CNS
what are bipolar neurons?
soma with a single axon and single dendrite stalk
common in special sensory organs
what are pseudo-unipolar neurons?
single axon with a proximal (efferent) and distal (afferent) branch
found in sensory neurons of dorsal root ganglion (soma for this neuron)
describe the components/make-up of a pseudo-unipoalr neuron
- proximal branch - CNS to soma
- soma/cell body - dorsal root ganglion
- distal branch - dendrite end to the soma
describe the structures in a negative feedback neuron loop
- sensor/receptor
- sensory neuron
- control center (brain/spinal cord)
- motor neuron
- effector: muscle or gland
what are the different classifications of neuron circuits?
- diverging
- converging
- reverberating
- parallel after discharge
what is the function of glial cells?
support neurons
typically 10 glia for every neuron
what does a diverging neural circuit do?
allows amplification or mass activation of many targets
what does a converging neural circuit do?
increase stimulation or inhibition of postsynaptic neuron
what is a reverberating neuron circuit do?
allows circular, self stimulation perpetuation of signal (essentially creating a tone)
what are parallel after discharge neuron circuits?
they diverge then converge to increase the frequency of output
what are the types of glia in the CNS?
- astrocytes
- oligodendrocytes
- microglial
- ependymal cells
what is the function of astrocytes?
provide support:
- physically (hold neuron in place)
- protective
- nutritional
- regulation of intracellular Ca2+
- NT regulation and uptake at synapse
- blood brain barrier
- tissue repair of CNS lesion
what is the role of oligodendrocytes?
form myelin sheaths in CNS (white matter)
what do microglia do?
phagocytosis
what are ependymal cells?
line ventricles and central canal facilitating exchange between CSF and interstitial fluid of brain
they are ciliated to facilitate flow of CSF
what is CSF?
cerebrospinal fluid
a blood plasma filtrate
what produces CSF?
choroidal epithelial cells - cover capillary tufts of choroid plexus; forms a unit with endothelial cells of choroid plexus
what are the different types of glial cells in the PNS?
- Schwann cells
- satellite cells
what do Schwann cells do?
form myelin sheaths in PNS
what are the structural layers of a nerve?
- fiber = singel cell
- endoneurium = CT covering of a fiber
- fascicle = bundle of fibers
- perineurium = CT covering of a fascicle
- whole nerve = bundle of fascicles
- epineurium = CT covering of whole nerve
describe the different section of a spinal nerve and what type of neurons are found there
- horns
- roots
- rami
what are rami communicants?
connect ventral rami to:
- paravertebral ganglia
- prevertebral ganglia
what are dermatomes?
a region of skin whose somatosensory signals are carried by a particular spinal nerve
what are myotomes?
all muscles innervated by a particualr spinal nerve
what pneumotic device is used to remember the cranial nerves?
Oh Oh Oh To Touch And Feel Very Good Velvet Such Heaven
what pneumotic device is used to remember the function of the cranial nerves?
Some Say Marry Money But My Brother Says Big Brains Matter More
S = sensory
M = motor
B = both
what are meninges?
connective tissue coverings encircling the brain and spinal cord
organized in a -tissue, fluid, tissue, fluid, tissue- arrangement
what are the3 CT layers in the meninges?
- Dura mater
- Arachnoid mater
- Pia mater
where is CSF found?
subarachnoid space
What is the role of CSF?
forms a protective cushion and buoys the brain and spinal cord
how is CSF produced?
mostly by filtration of blood plasma through specialized capillaries called choroid plexuses which have an outer covering of ependymal cells that contribute to the blood brain barrier.
where are choroid plexi located?
all 4 ventricles
List the 4 ventricles
- R/L ventricles (lateral ventricles)
- R/L hemisphere in all 4 lobes
- 3rd ventricle
- between hemispheres at level of thalamus hypothalamuc (diencephalon)
- 4th ventricle
- brain stem at level of pons/cerebellum and upper medulla
*all are interconnected
what is the foramen of Monroe?
also called interventricular foramen
connects lateral ventricles to 3rd ventricles
what is the cerebral aqueduct of Sylvius?
connects 3rd ventricle to 4th ventricle
what connects the 4th ventricle to the subarachnoid space?
- foramena of Lushka - 2 lateral apetures
- foramen of Magendie - single medial aperture
what does the blood brain barrier block?
exchange of hydrophilic substances
what does the blood brain barrier consist of?
- continuous capillar endothelium with tight junctions
- thick basement membrane
- covering of astrocytes
which organs do not have a blood brain barrier?
circumventricular organs:
hypothalamus
pituitary
pineal gland
why do circumventricular organs not have a blood brain barrier?
in order to monitor chemical composition of blood
what are the different causes of an axonal injury in the PNS?
- Stretch
- Crush
- Shear
- Laceration
what are the 2 ways axons in the PNS will regrow?
- axonal sprouting
- collateral
- regenerative
what are the steps in axonal regeneration following injury in the PNS?
- injury to peripheral nerve
- macrophages rapidly remove myelin debris
- expression of growth-related factors
- axon regrowth
what are the causes of axonal injury in the CNS?
- trauma
- decreased blood flow (ischemia)
- neurodegenerative disease
T/F: CNS axons can regrow after injury
FALSE
typically cannot, instead the brain creates new pathways to compensate for axons lost
what doesn’t the CNS regenerate axons?
- CNS damage triggers necrosis and apoptotic cell death of severed axons
- Clean up is slow
- CNS environment is hostile to regenerative attempts
- astrocytes - glial scarring
- microglial activation
what is glial scarring?
astrocytes enter injuried area and form a scar to block the apoptosis and further damage → problem with this is that it is a physical blockade/scar which blocs future attempts for regrowth of that axon
what is the significance of microglial activation following CNS axonal damage?
microglial cells clear out debris from damage, but cannot differeniate between good and bad cells which ends up cleaning out more than they should
T/F: there is a low level of glial cells that can proliferate throughout our lifetime
TRUE
what are two areas in the brain that are an exception to the regeneration rule?
- olfactory bulb
- hippocampus
define neuroplasticity
the ability of the nervous system to reorganize its structure, function and connections in response to injury or the environment, in support of learning, or in relation to therapy
What are the neuroplasticity mechanisms based off of effect size?
- chemical
- short term memory
- structural
- strong sustained exposure to activities resulting in structural changes
- functional
- when sufficientyly stimulated, neurons can adopt new function and pass new info along (cortical remapping)
what is synaptic pruning?
the ability to pick up on what is important and what is not important
prioritize the pathways that stay “open” and running
what are the 2 neuroplasticity mechanisms, based off of how the brain responses to a stimulus?
- Habituation
- Learning and memory
what is habituation?
a decrease in response to a repeated, benign stimulus
allows us to tune out non-important stimuli and focus on important stimuli
what short term habituation
- short term
- stimulus given around 30 minutes → tends to be transient
- presynaptic in nature → presynaptic neuron will dump less NT into the synaptic cleft which will blunt the reponse
what is long-term habituation?
- long term
- over an hour
- postsynaptic changes observed → changes in receptors and proteins being synthesized, tend to be more long lasting changes
what are the different types of learning and memory development?
- Experience-dependent plasticity
- long-term potentiation and depression
what is Long-term potentiation (LTP)?
process by which the synaptic connections between neurons become stronger by frequent activation
requires high intensity stimulation
which does LTP require a high intensity stimulation?
- it will alloow more glutamate to be dumped into synaptic cleft
- more Na enters the cell
- results in a larger depolarization event
- this repels Mg out of the NMDA channel (electrostatic repulsion)
- Ca can now move into the cell and act as a secondary messenger
- this results in an increase in structural changes to the postsynaptic cell
- increased in AMPA receptors (Na channel)
- growth factors = creation of more synapses = cortical remapping
what is long-term depression (LTD)?
conversino of active synapses into silent ones
“reset button”
low-intensity, prolonged stimulation required
what are the 10 principles of Neuroplasticity?
- Use it or Lose it
- Use it and Improve it
- Specificity matters
- repetition matters
- intensity matters
- time matters
- salience matters
- age matters
- transference or generalization
- interference
what is CINT?
constraint induced movement therapy → restraining the strong arm following a stroke for 23 out of 24 hours of the day, forces pt to use their paralytic arm
what is the brain made up of?
over 100 billion neurons (mostly inter-neurons = associative) and 1 trillion neuroglia
what are the 5 vesicles of the brain?
- Telencephalon
- Diencephalon
- Mesencephalon (midbrain)
- Metencephalon
- Myelencephalon
what parts of the brain are in the Telencephalon?
- Cerebral hemispheres
- basal ganglia
- limbic system
what parts of the brain are in the Diencephalon?
- thalamus
- hypothalamus
- epithalamus
What parts of the brain are in the Mesencephalon (midbrain)?
- cerebral peduncle
- corpus quadrigemina
- Superior colliculi
- inferior colliculi
- CN3 and CN4 nucleus
- Red nucleus
- Substantia nigra
what parts of the brain are in the Metencephalon?
Pons
what parts of the brain are in the Myelencephalon?
- Medulla oblongata
what are the components of the brain stem?
- medulla oblongata
- pons
- midbrain (mesencephalon)
Mesencephalon, Metencephalon and Myelencephalon
what does SCALP stand for?
skin
connective tissue
aponeurosis
lipid
periosteum
*protective coverings of the brain
what are the protective coverings of the brain?
- cranial bones (skull)
- epidural space with fat
- dura mater
- subdural space w/interstitial fluid
- arachnoid mater
- subarachnoid space w/CSF
- pia mater
name the folds of dura mater that hold the brain in place
- falx cerebri
- falx cerebelli
- tentorium cerebelli
what is the falx cerebri?
a sagittal fold between cerebral hemispheres
what is the falx cerebelli?
a sagittal fold between cerebellar hemispheres
what is the tentorium cerebelli?
a transverse fold between cerebrum and cerebellum
what are the 3 components of the blood brain barrier?
- tight junctions between blood vessel endothelial cells
- continuous endothelial cell basement membrane
- astrocytes wrapped around the endothelial cell basement membrane
T/F: the BBB allows free passage of hydrophillic substance into the brain?
FALSE
allow free passage of lipid soluble, hydrophobic substances
what are the components of the medulla oblongata?
- nerve tracts (both sensory ascending and motor descending)
- pyramids
- decussation of pyramids
- olives
- dorsal medulla
- fasciculus gracilis
- fasiculus cuneatus
- decussation of the medial lemniscus
- nuclei
- cranial nerve nuclei for CN, 8 - 12
what is the overall function of the brain stem?
- contains nuclei for vital centers and cranial nerves
- signal propagation via ascending (sensory signals) and descending (motor signals) tracts
what are the pyramids in the medulla oblongata?
paried ventral surface ridges that contain motor descending tracts
what are the decussation of pyramids?
where motor tracts from R/L brain cross to control muscles on the opposite side
what are the olives in the medulla oblongata?
paired bulges lateral to pyramids which contain the inferior olivary nuclei
these link the brain and spinal cord motor signals to the cerebellum for perception of time
what do the fasciculus gracilis and cuneatus do?
relay sensory ascending input to the opposite side of the brain
what is the decussation of the medial lemniscus?
crossover of ascending sensory input to the contralateral brain hemisphere
What is contained within the Pons?
- cranial nerve nuclei for CN 5, 6, and 7
- ascending and descending tracts
what is the function of the Pons?
information relay for cerebellar hemmispheres
what is located in the midbrain?
- cerebral peduncles
- corpora quadrigemina
- cranial nerve nuclei for CN 3, 4
- red nucleus and substantia nigra
what are the cerebral peduncles?
they contain descending motor axaon tracts from cerebral hemispheres to spinal cord, medulla, and pons
and
ascending sensory axons going to the cerebrum
what is the corpora quadrigemina made up of?
- superior colliculi
- inferior colliculi
what does the superior colliculi control?
reflex movement of eye, head, and neck to visual and other stimuli
what do the inferior colliculi control?
reflex movement of head and neck to auditory stimuli
what is the function of the red nucleus and substantia nigra?
modify motor signals
what is the overall function of the midbrain?
- relay motor impulses from cerebral cortex
- relay sensory impulses from spinal cord to thalamus
what is the reticular formation?
a diffuse structure, composed of areas of gray matter interspersed among areas of white matter in central portions of the Diencephalon, brain stem, and spinal cord
what is the function of the reticular formation?
- alerting cerebral cortex to sensory signals
- reticular activating system → functions in maintaining consciousness and awakening from sleep by stimulating the cortex
- filter sensory input to remove unimportant input (prevents sensory overload)
- efferent motor function in maintaining muscle tone
what is the cerebellum (metencephalon) comprised of?
- vermis (worm)
- cerebellar hemispheres
- peduncles
describe the cross section anatomy of the cerebellum
- cortex = gray matter
- folia ridges
- arbor vitae (nerve tracts = white matter)
- cerebellar nuclei
what is the function of the cerebellum?
- smooth and coordinate (refine) cerebral control of skeletal muscle movements to facilitate complex muscle activity
- regulate muscle tone
- posture and balance
what makes up the Diencephalon?
- thalamus
- hypothalamus
- epithalamus
- subthalamus
describe the structure of the thalamus
composed of paired masses of mixed gray (nuclei) and white (tracts) matter that are connected by intermediate mass (crossover point)
what is the function of the thalamus?
- relay sensory info to correct region of cerebral cortex
- refine motor signals with the basal nucleus
describe the composition of the hypothalamus
composed of:
- dozen nuclei
- mammillary bodies (visible on inferior surface)
- infundibulum (connects pituitary to the hypothalamus)
what is the overall function of the hypothalamus?
control of body activities to maintain homeostasis
T/F: the hypothalamus is a circumventricular organ?
TRUE
what are the specific functions of the hypothalamus?
- control of ANS: heart, gut, bladder
- control of endocrine system via control of the pituitary gland
- regulates emotional behavior (part of limbic system)
- regulates eating and drinking
- control body temp
- regulates circadian rhtyhms and states of consciousness
describe the structure of the epithalamus
composed of:
- pineal gland
- habenular nuclei (paired structure)
what is the function of the epithalamus?
more of a modulator
functions in:
- melatonin production (at pineal gland)
- habenular nuclei involved in the emotional response to smell
what is the subthalamus composed of?
- subthalamic nuclei (paired)
- parts of red nuclei (paired)
- parts of substantia nigra (paired)
what is the function of the subthalamus?
connects to cerebellum and motor cortex for control of body movement
what are circumventricular organs?
areas of the brain that do not have a BBB, therefore they are able to monitor chemical changes in the blood
tend to be endocrine organs
where are circumventricular organs found?
- hypothalamus
- pineal
- pituitary (hypophysis)
what region of the brain are the basal ganglia in?
Telencephalon
what are the basal ganglia?
consist of paired nuclei (gray matter)
function in control of skeletal muscle movement and muscle tone. Refine movement from uncoordinated jerky motion to smooth motion
what region of the brain is the limbic system in?
Telencephalon
Diencephalon
what is the limbic system comprised of?
- paired nuclei
- tracts
- cortex (parts of frontal, parietal, and temporal lobes)
what is the function of the limbic system?
“primitive brain” function in emotion aspects of behavior and memory-pain, pleasure, affection, and anger → to determine feelings
What portion of the brain is the cerebrum in?
Telencephalon
describe the composition of the cerebrum
- cerebral cortex (gray matter)
- cerebral white matter
what is cerebral cortex (gray matter)?
10s of billions of associate (inter) neurons
typically arranged in 6 layers to allow vertical integration
what is cerebral white matter made of?
3 types of neurons:
- association fibers
- commissural fibers
- projection fibers
what do association fibers in the cerebral white matter do?
connect different gyri in same hemisphere
what do commissural fibers in cerebral white matter do?
connect different gyri in opposite hemisphere (found in corpus collosum)
what do projection fibers in the cerebral white matter do?
connect the cerebrum to rest of body (sensory and motor tracts)
Cerebrum is the highest of the brain regions, what are it’s functions?
- conscious sensation
- voluntary motor activity
- higher brain functions
- cognition
- association of sensory input with memory to produce more memory
- language
- astract though
describe the surface anatomy of the cerebrum
- gryi = ridges
- sulci = shallow grooves
- fissures = deep grooves
- longitudinal fissures = separate R/L hemispheres
- hemispheres = R/L side of cerebru
- corpus callosum
- lobes
- central sulcus
- precentral gyrus
- lateral cerebral fissure (sulcus)
- parieto-occipital sulcus)
what is the corpos callosum?
large collection of commissural tracts connecting R/L hemispheres
what is the central sulcus of the cerebrum?
separates frontal and parietal lobes
what is the precentral gyrus of the cerebrum?
anterior to central sulcus
voluntary (somato-) motor area
what is the postcentral gyrus of the cerebrum?
posterior to central sulcus
conscious (somato-) sensory area
what is the lateral cerebral fissure (sulcus) of the cerebrum?
separates frontal and temporal lobes
what is the parieto-occipital sulcus of the cerebrum?
separates parietal and occiptal lobes
Name the Lobes of the cerebrum
- Frontal
- Parietal
- Temporal
- Occipital
- Insula
where is the frontal lobe?
anterior of central sulcus and medial to lateral sulcus
what are the different sections of the frontal lobe?
- precentral gyrus
- premotor area (supplemental motor area)
- frontal eye field
- Broca’s area
- prefrontal cortex
- cingulate gyrus
what are the components of the precentral gyrus?
- primary motor cortex
- somatotopic
- homunculus
what does the primary motor cortex do?
control voluntary movement on contralateral side of the body
what does the term somatotopic mean?
refers to specific regions of the precentral gyrus that control muscles in specific body regions
what is a homunculus?
it depicts somatotopic organization of precentral gyrus and relative cortical contributions to a particular body region
what is the premotor area (supplemental motor area) of the frontal lobe?
associative area next to precentral gyrus functions to initiate and sequence motor activity
what is the function of the frontal eye field of the Frontal lobe?
coordinated R and L eye movement = conjugate eye movements
What is Broac’s area on the Frontal Lobe?
on L hemisphere only
coordinates motor speech
where is the prefrontal cortex?
rostral most part of the frontal lobe
primary target of lobotomy
significance of the prefontal cortex?
input from all regions of cortex and limbic system
output to wide variety ⇒ subcortical nuclei-thalamus, basal ganglia, brain stem
functions to regulate visceral, emotional, and cognitive processes
what is the cingulate gyrus of the frontal lobe?
medial surface (within longitudinal fissure) of frontal and parietal lobes
limbic cortex for emotional behavior, autonomic reponse, and learning
where is the Insula lobe located?
within the lateral sulcus where frontal, parietal and temporal lobes come together
what is the function of the Insula Lobe?
integration of sensory input for:
- taste and olfaction
- viscerosensation (interoreceptors)
- pain
what are the sections of the Parietal Lobe?
- post central gyrus
- supramarginal and angular gyrus
- Wernicke’s area
- superior parietal lobe
what part of the Parietal Lobe is located at the post central gyrus?
Somatosensory Cortex
primary sensory area for tactile and proprioceptive sensation → end destination for conscious somatosensory signals
what does the supramarginal and angular gyrus do?
receive visual and auditory input for perceptional discrimination and integration
where is Wernicke’s area and what does it do?
located in both parietal and temporal lobes of the Left hemisphere
functions in comprehension of spoken language and works with Broca’s area to formulate a verbal reponse
what is the superior parietal lobe?
an association area integrating sensory and motor areas to program complex motor responses
where is the occipital lobe of the cerebrum located?
caudal to the parietal-occipital sulcus on the medial border
what is located in the occipital lobe?
primary visual cortex
visual association cortex
name the structures at the temporal lobe
- primary auditory cortex
- superior temporal gyrus
- middle temporal gyrus
- inferior temporal gyrus
- parahippocampal gyrus and uncus
where is the primary auditory cortex located?
medial aspect of superior temporal gyrus → transverse gyri Heschl
what is located at the superior temporal gyrus?
auditory association cortex
what is the function of the middle temporal gyrus?
perception and analysis of motion in the visual field
what is the function of the inferior temporal gyrus?
facial recognition in response to visual input
where is the parahippocampal gyrus and uncus and what is it’s function?
located on the inferior surface of temporal lobe
function w/limbic system
how are hemispheres in the cerebrum divided?
separated by longitudinal fissure and connected by commissural fibers
what is hemispheric localization?
refers to the functional differences that exist between hemispheres = cerebral dominance
what is the left hemisphere primarily responsible for?
- language interpretation and execution
- numerical and scientific skills (abstract)
- reasoning
what is the right hemisphere primarily responsible for?
- musical, artistic
- special pattern interpretation
- facial recognition
- emotional content of language
- mental images of visual, auditory, somatic, taste, olfactory input
what is cerebral dominance due to?
- unequal cortical representation of function in homologous regions of the 2 hemispheres
- diminished commissural cross connection between the regions
- visual cortex → temporal eye field is uncrossed
- primary motor and sensory areas of distal arm and leg
describe the course of the internal carotid through the skull
- external opening of carotid canal
- carotid canal (petrous part of temporal bone)
- internal opening of carotid canal
- crosses over foramen lacerum
- runs along base of sella turcica in carotid groove
- joins the optic nerve at prechiasmatic groove
what are the branches of the internal carotids proximal to distal?
- opthalmic
- posterior communicating
- anterior choroidal artery
- anterior cerebral artery
- middle cerebral artery
where does the opthamic artery run?
with CN2 supplying blood to the choroid/retina of the eye
via central artery of the retina
what does the posterior communicating artery connect the internal carotid to?
Circle of Willis
what does the posterior communicating artery eventually supply?
Circle of Willis which supplies:
- diencephalon
- pituitary
- infundibulum
- hypothalamus
- thalamus
where is the anterior choroidal artery and what does it supply?
arises near middle cerebral artery
supplies choroid plexus of lateral ventricles, optic tract, internal capsule, globus pallidus (basal nucleus)
*supplies deep structures of telencephalon
where does the anterior cerebral artery run?
runs in longitudinal fissure above corpus callosum to medial aspect of frontal and parietal lobes
what is the anterior communicating artery?
an anastomosis between R/L anterior cerebral arteries
what does the middle cerebral artery supply?
runs in lateral sulcus to:
- lateral frontal
- lateral parietal
- insula
- lateral occipital
- M/L temporal
- sub-cortical deep structures
- basal ganglia
- internal capsule
- limbic structures
after the vertebrals pass through the foramen magnum where do they head next?
they ascend the clivus and then fuse into basilar artery
what are the branches of the vertebral arteries from proximal to distal?
- anterior spinal artery - medial medulla
- posterior inferior cerebellar - lateral medulla
- posterior spinal artery - dorsal medial medulla
what are the branches of the basilar artery from proximal to distal?
- anterior inferior cerebellar
- labyrinthine arteries
- pontine arteries
- superior cerebellar arteries
- posterior cerebral arteries
what does the anterior inferior cerebellar artery supply?
it is a branch of the basilar artery
supplies cerebellum and pons
what do the labyrinthine arteries supply?
branch of basilar artery that enters internal acoustic meatus
supplies cochlea and vestibular apparatus
what do the pontine arteries supply?
branch of basilar artery
supplies pons
what do the superior cerebellar arteries supply?
branch of basilar artery
supplies cerebellum, pons, and midbrain
what do the posterior cerebral arteries supply?
branch of basilar artery
supplies cortex (medial and inferior occipital, inferior temporal) and subcortical structures of midbrain, subthalamus, and thalamus
what is the Circle of Willis?
an anastomosis between internal carotid arteries and basilar arteries
what forms the Circle of Willis?
- anterior communicating arteries
- anterior cerebral arteries
- posterior communcating arteries
- posterior cerebral arteries
what is the dural artery?
middle meningeal from the maxilary artery (from external carotid) via foramen spinosum
what is the venous drainage of the brain?
Dural sinuses
what is the path of venous blood flow in the brain?
- superior sagittal sinus, inferior sgittal sinus (to straight sinus) and occipital sinus all drain into:
- confluence of sinuses
- transverse sinus
- superficial veins
- sigmoid sinus
- internal jugular vein
name the venous plexi in the brain
- cavernous sinus
- pterygoid sinus
- basilar
- superior and inferior petrosal drain into sinuses or jugular veins
Name the grooves in the spinal cord cross section
- anterior median fissure
- posterior median sulcus
what is gray matter in the spinal cord?
located in an H shaped central core
contains neurons and neuroglial cell bodies as well as unmyelinated neuron processes (axons and dendrites)
what are all the gray matter structures within the spinal cord?
- dorsal horn
- ventral horn
- lateral horn
- rexed’s laminae
- grey commissure
T/F: the ventral horn of the spinal cord is somatotpically organized?
TRUE
how is the ventral horn somatopically organized?
- medial ventral horn → controls axial muscles
- lateral ventral horn → controls appendicular muscles
- posterior section of ventral horn → controls flexors
- anterior section of ventral horn → controls extensors
which regions of the spine have lateral horns?
Thoracic, Lumbar and Sacral
T1-L2 = sympathetic preganglionic neurons
S2-S4 = parasympathetic preganglionic neurons
What are Rexed’s Laminae?
10 histological/functional regions of gray matter in the dorsal and ventral horns
what are the lamina in Rexed’s laminae responsible for?
- Lamina 1 = marginal layer for noxious stimuli
- lamina 2 = substatia gelantinosa for noxious stimuli etc.
what is the grey commissure in the spinal cord gray matter?
connection between R and L gray matter
allows signals to cross to the opposite side
what is located in the white matter of the spinal cord?
ascending (sensory) and descending (motor) tracts (fasiciculi) which are bundles of myelinated axons with a similar origin and terminal destination
list the organization of the white matter columns in the spinal cord
- Dorsal Column = bundle of tracts
- Lateral Column
- A/P lateral column
- Anterior Column
- Propriospinal = axons that begin and end within the cord providing interconnections between tracts and gray matter for context
what is the central canal?
a continuation of the 4th ventrile of the brain, contains CSF
what does the term funiculus mean? what about fascicula?
funiculus = column
fascicula = tract
what is the function of the spinal cord?
- propagate nerve impulses between the periphery and the brain
- somatic reflex control center
what is the primary arterial supply to the spinal cord?
- cervical = spinal branches from vertebral arteries
- thoracic = spinal branches from posterior intercostal arteries
- lumbar = spinal branches from lumbar arteries
what do the spinal branches of the primary arteries of the spinal cord branch into?
dorsal and ventral segmental arteries
what do the dorsal and ventral segmental arteries of the spinal cord form?
- deep anterior region = anterior spinal artery
- deep posterior region = 2 posterior spinal arteries
- superficial regions = A/P radicular
List the veins of the spinal cord
- anterior medial spinal vein
- anterolateral spinal vein
- posteromedian spinal vein
- posterolateral spinal vein
What are the 2 types of NT receptors?
- Ionotropic → ligand-gated ion channels
- Metabotropic → G-coupled receptors
Name some of the more prominent neutrotransmitters
- Glutamate
- GABA
- Glycine
- Acetylcholine
- Serotonin
- Dopamine
- Norepinephrine
T/F: Glutamate is the most abundate NT in our brain and CNS?
TRUE
what type of NT is glutamate?
Excitatory post-synaptic response
what functions are associated with glutamate?
learning and memory
synaptic plasticity
what types of receptors bind glutamate?
- Ionotropic:
- NMDA
- AMPA
- Kainate
- Metabotropic
- 3 groups and 8 subgroups
- modulate glutamate release
- affect postsynaptic excitability
T/F: Kinate receptors have both resynaptic and postsynaptic actions?
TRUE
presynaptic: GABA
postsynaptic: Glutamate
Name some agonists/antagonists to glutamate
Antagonists:
phencyclidine
Riluzole
What are some clinical pathologies assocaited with glutamate?
- glutamate excitotoxicity
- schizophrenia
- epilepsy
- Alzheimer’s disease
what is glutamater excitotoxicity?
increased glutamate → excess intracellular Ca2+ → apoptosis
What is the major inhibitory NT in the CNS?
GABA
particularly at interneurons wihtin the spinal cord
what is the function of the GABA NT?
- used in trx of anxiety, reha for drug abuse
- inhibits motor, sensory, and cognitive neurons
- sedation, muscular/cardiorespiratory relaxation, pain inhibition
What are the receptors for GABA?
Ionotropic: GABAA
Metabotropic: GABAB
Name some agonists/antagonists to GABA
Agonists:
Alcohol
Benzodiazepines
Barbiturates
Baclofen
what are some clinical pathologies that GABA is used in?
Epilepsy trx
Huntington’s disease
where is glycine found and what does it do?
brainstem and spinal cord
inhibitory post-synaptic response
functions → inhibits spinal interneurons
What are some receptors for Glycine?
Ionotropic: Cl- channel (inhibitory)
Name some agonists/antagonists to Glycine
antagonist
Strychnine
What are some clinical pathologies that glycine is used in?
spasticity
spinal shock
where is ACh found?
widely distributed
in motor neurons, basal ganglia and ANS
found in NMJ
what type of NT is ACh?
Excitatory post-synaptic response
what is the function of ACh?
- triggers muscle contraction
- ANS involvement
- stimulates excretion of certain hormones
- in CNS, involved in wakefulness, attentiveness, anger, sexuality, amongst other things
T/F: ACh is a major converyer of info in the PNS?
TRUE
what are some receptors for ACh?
Ionotropic: nicotinic (excitatory)
Metabotropic: muscarinic (excitatory or inhibitory)
Name some agonists/antagonists to ACh
Agonist: Nicotine
Antagonist: Botulinum toxin, Atropine
What are some clinical pathologies that ACh is used in the treatment
Alzheimer’s Disease, Dementia
Myasthenia Gravis
Tobacco addiction
where is serotonin found?
brain and brainstem (pineal gland, raphe nuclei in pons, limbic system) and GI tract
T/F: serotonin is both excitatory and inhibitory postsynaptically?
TRUE
what are some functions of serotonin?
- emotions
- sleep-wake cycles and other autonomic functions
- GI tract regulation, appetite
- cardiovascular growth factor
what are some receptors for serotonin?
Ionotropic: 5-HT3 (excitatory)
Metabotropic: 5-HT1-7 (excitatory or inhibitory)
Name some agonists/antagonists to serotonin
Agonists: SSRIs
What are some clinical pathologies that serotonin is used in the treatment?
Depression
OCD
Autism
Serotonin Syndrome
Where is dopamine found?
CNS: substantia nigra, midbrain, hypothalamus
ANS: aympathetic neurons
T/F: dopamine has both excitatory and inhibitory post-synpatic responses
TRUE
what are some functions of dopamine?
- movement
- reward
- memory, attention, motivation
- and a lot more!
what class of NT is dopamine?
Amine
these function as neuromodulators
what are some receptors for dopamine?
ionotropic: none
Metabotropic: excitatory and inhibitory
Name some agonists/antagonists to dopamine
agonists:
amphetamines
L-dopa
what are some clinical pathologies that dopamine is used in the treatment?
Parkinson’s Disease
Schizophrenia
ADHD
Substance dependency
where is NE found?
cortex: locus ceruleus (pons) and medulla
ANS: sympathetic neurons
what type of NT is NE?
excitatory post synaptic response
*there are some inhibitory responses linked to NE
what is the function of NE?
- plays a vital role in active surveillance by increasing attention to sensory info
- SNS: essential for “fight or flight” reaction to stress
What are some receptors for NE?
Ionotropic: none
Metabotropic: alpha 1 and 2, and beta
Name some agonists/antagonists to NE
Antagonist: Beta blocker
Agonist: Amphetamines, Cocaine, TCA
what are some clinical pathologies that NE is used to treat?
ADHD
Hypotension
PTSD
Parkinson’s Disease
what is located in the inferior cerebellar peduncle?
afferent fibers from spinal cord and medulla to cerebellum
(posterior spinocerebellar tract, cuneocerebellar tract)
what general nuclei are located in the medulla?
- CN 8-12
- nuclei of vital centers
- nuclei of reticular formation
list the anterior surface anatomy structures of the medulla
- paired pyramids
- decussation of pyramids
- CN 6 - 12 emerging
- inferior olivary nuclei
what are the paired pyramids on the anterior surface of the medulla?
corticospinal tracts
carrying descending somatomotor signals
What is the decussation of pyramids on the anterior surface of the medulla?
where the descending corticospinal tracts cross to the opposite side of the body
T/F: 75% of the corticospinal tracts from the cerebrum cross at the decussation and form the lateral corticospinal tract?
FALSE
90% do
these mostly supply appendicular muscles
what is the medial corticospinal tract?
the remaining 10% of descending corticospinal tracts that do not cross to the opposite side at the decussation of pyramids in the medulla
mostly axial muscles
what is the role of the inferior olivary nuclei?
cerebellar relay center for perception of time
list the posterior surface anatomy structures of the medulla
- fasciculata cuneatus
- fasciculata gracilis
- tuberculum cuneatus and gracilis
- nuclei cuneatus and gracilis
- open part associated w/4th ventricle underlying the cerebellum
- area postrema
what is the area postrema?
floor of 4th ventricle leading to opening of central canal
vomit center
list the fiber tracts located at the caudal closed medulla (level of pyramid decussation)
- pyramids: corticospinal
- decussation of pyramids
- fasciculus gracilis
- fasciculus cuneatus
- spinothalamic tracts
- anterior spinocerebellar
- posterior spinocerebellar
- CN 5 spinal trigeminal tract
what type of information is carried in the pyramids at the medulla?
efferent voluntary from cerebral cortex to muscles of trunk and appendages
what type of information is carried in the fasciculus gracilis?
sensory touch and proprioception from the legs
(touch, pressure, pain, etc.)
what type of information is carried in the fasciculus cuneatus?
sensory touch and proprioception from the arms
from the brachial plexus (touch, pressure, pain, etc.)
what type of information is carried in the spinothalamic tracts?
sensory pain and temperature from trunk and appendages
what type of information is carried in the anterior spinocerebellar tract?
sensory info from thoracolumbar ventral horn to cerebellum
what type of information is carried in the posterior spinocerebellar tract?
sensory from legs to cerebellum
what type of information is carried by the CN 5 spinal trigeminal tract in the medulla?
localized pain from the face/head
what nuclei are found in the caudal closed medulla
(level of the pyramid decussation)
spinal trigeminal nucleus CN5 = afferent pain and temp of the head
list the fiber tracts found in the rostral closed medulla
(level of decussation of medial lemniscus)
- decussation of medial lemniscus
- pyramids
- CN 5 spinal tract
- anterior spinocerebellar
- posterior spinocerebellar
- spinothalamic tracts
- medial longitudinal fasciculus
what is the decussation of medial lemniscus in the medulla?
crossover point for ascending fibers for proprioception and tactile sensation from the nuceli gracilis and cuneatis (ie. dorsal column tracts)
what type of information is carried by the medal longitudinal fasciculus?
(*list tracts and nuclei)
BALANCE
- afferent ascending sensory from vestibular nuclei
- descending motor from medial vestibulospinal tract
- tectospinal tract (head turner)
list the nuclei found in the rostral closed medulla
- nucleus gracilis
- nucleus cuneatis
- accessory cuneate nucles
- spinal trigeminal nucleus CN5
- reticular formation
- inferior olivary nuclei
- nucleus ambiguous
what is the accessory cuneate nucleus associated with?
cuneocerebellar tract
(sensory info from arms to cerebellum via inferior cerebellar peduncle)
what is the role of the reticular formation?
- modulates sensory signaling to cortex
- modulates motor signaling (reticulospinal tracts)
- autonomic activity
- sleep/wake
- emotions
what makes up the nucleus ambiguous?
CN9 and 10 (for swallowing)
what differentiates the open medulla from the closed medulla?
central canal in the closed medulla is replaced with the 4th ventricle in the open medulla
what is the basal plate?
the floor of the 4th ventricle medially
at the open medulla
contains motor nuclei
what is the alar plate?
floor of the 4th ventricle laterally
open medulla
contains sensory nuclei
list the nuclei found in the basal plate (from medial to lateral)
- hypoglossal nuclei (CN 12)
- nucleus ambiguus (CN 9 and 10)
- dorsal motor nucleus (CN 10 = PNS)
- inferior salivatory nucleus (CN9 to parotid)
what does the hypoglossal nucleus in the basal plate contain?
somatomotor to skeletal muscle of tongue
what does the nucleus ambiguus at the basal plate do?
contain special visceral efferent to skeletal muscles of larynx and pharynx for swallowing
list the nuclei found in the alar plate of the open medulla (moving medially to laterally)
- solitary nucleus (CN 7, 9, 10)
- spinal nucleus of CN 5
- vestibular nuclei of CN 8 (inferior and medial)
- cochlear nucleus of CN 8
what is role of the solitary nucleus in the alar plate?
- viscerosensory from CN 9 and 10 for cardiovascular and respiratory input
- special sensory for taste (CN 7, 9, 10)
what does the spinal nucleus of CN 5 in the alar plate contain?
general somatic afferent for somatosensory (pain and temp) of head
what does the vestibular nuclei of CN 8 (inferior and medial) in the alar contain?
special sensory afferent for balance
what does the cochlear nuclei of CN 8 in the alar plate do?
special sensory afferent for auditory
What fiber tracts are found in the open medulla?
- inferior cerebellar peduncle
- medial longitudinal fasciculus with tectospinal tract
- medial lemniscus
- spinothalamic tract
- pyramids (corticospinal tract)
what type of info does the inferior cerebellar peduncle carry?
afferent sensory from arms and legs to cerebellum
what is the function of the medial longitudinal fasciculus and the tectospinal tract?
coordinates movements of eyes and body with vestibular input for overall balance/equilibrium
what nuclei are not found in the alar and basal plate of the open medulla?
- reticular formation
- inferior olivary nuclei
describe the gross anatomy of the pons
- basilar pons = ventral surface
- pontine tegmentum = dorsal surface and floor of 4th ventricle
where are ascending sensory tracts generally found in the pons?
tegmental area (dorsal surface)
where are descending motor tracts generally found in the pons?
basilar area (ventral surface)
list the fiber tracts that are found in the basilar pons
- transverse pontine (pontocerebellar)
- corticospinal fiber tract
- corticobulbar fiber tract
what type of info is carried by the transverse pontine (pontocerebellar) tract?
relayed afferent signals to cerebellum via middle cerebellar peduncle
what type of fibers is the transverse pontine (pontocerebellar) tract made up of?
commissural and afferent fibers
where are the corticospinal and corticobulbar fiber tracts?
run longitudinally through basilar pons
what type of info is carried by the corticobulbar tract?
somatomotor from precentral gyrus to the head
what type of info is carried by the corticospinal tract?
somatomotor from precentral gyrus prior to decussation of pyramids heading to the body
what nuclei are found in the basilar pons?
deep pontine nuclei
list the fiber tracts that are found in the tegmental pons
- facial colliculus
- S/M/I cerebellar peduncle
- medial lemniscus
- medial longitudinal fasciculus
- spinothalamic
- trigeminothalamic
- lateral lemniscus
- rubrospinal tract
- tectospinal tract
- spinal nucleus tract of CN 5
- descending limbic and hypothalamic fibers
what type of info is carried by the facial colliculus
facial nerve CN7 fibers
what type of info is carried by the superior cerebellar peduncle?
efferent fibers from cerebellum to brain stem and cortex
what type of info is carried by the middle cerebellar peduncle?
afferent fibers from cortex to cerebellum
what type of info is carried by the inferior cerebellar peduncle?
afferent fibers from medulla and spinal cord to cerebellum
what type of info is carried by the medial lemniscus at the level of the tegmental pons?
touch, pressure and proprioception from the entire body ascending to the cortex
what type of info is carried by the spinothalamic tract in the tegmental pons?
somatosensory (pain and temperature) from body
what type of info is carried by the trigeminothalamic tract in the tegmental pons?
afferent somatosensory from head to cortex
what type of info is carried by the lateral lemniscus in the tegmental pons?
auditory relay circuit to inferior colliculus for auditory reflex movement of head
what type of info is carried in the rubrospinal tract?
efferent motor signals to the arms
what type of info is carried by the tectospinal tract?
efferent somatomotor signals to muscles of neck and shoulders (head turning reflex)
what type of info is carried by the spinal nucleus tract of CN 5?
pain and temperature sensation from head
this transitions into the trigeminothalamic tract (in the medulla)
what type of info is carried by the descending limbic and hypothalamic fibers of the tegmental pons?
info that is carried to autonomic control centers in medulla and spinal cord
list the nuclei that are located in the caudal portion of the tegmental pons
- facial nucleus CN 7
- abducens nucleus CN 6
- spinal trigeminal nucleus CN 5
- superior olivary nucleus (not pictured below)
- trapezoid body
- M/I vestibular nucleus
- superior salvatory nucleus
what does the facial nucleus of CN 7 control?
muscles of facial expression
what does the abducens nucles of CN 6 control?
eye muscles (lateral rectus)
what do the superior olivary nucleus and trapezoid body do?
they are relays in the auditory pathway
what does the superior salvatory nucles do?
fibers are part of CN7 to lacrima, submandibular, and sublingual salivary glands
list the nuclei that are located in the rostral pons
- main sensory nucleus of CN5
- motor nucleus of CN 5
- mesencephalic nucleus CN5 (not pictured below)
- S/L vestibular nucleus
- locus ceruleus
- raphe nuclei
what is the main sensory nucleus of CN 5?
continuation of spinal trigeminal nucleus (light touch from face via trigeminal ganglion synapses here)
what does the motor nucleus of CN 5 supply?
somatomotor
to muscles of mastication
what does the mesencephalic nucleus of CN 5 do?
proprioception of jaw (from trigeminal ganglion)
what is the locus ceruleus?
part of reticular formation (NE)
involved in pain modulation
what is the raphe nucleus?
part of reticular formation (serotonin)
involved in pain modulation
what tracts merge together in the rostral pons to form a single tract to the postcentral gyrus?
medial lemniscus
spinothalamic
trigeminothalamic
lateral lemniscus
all merge together into the medial lemniscus
what are the 3 general layers of the Midbrain?
- Tectum = dorsal
- Tegmentum = intermediate
- Crus Cerebri = ventral
what structures are on the tectum of the Midbrain?
(dorsal layer)
Corpus quadrigemina = S/I colliculi
what is the superior colliculi responsible for?
visual reflex response to unexpected stimuli in visual field
what is the inferior colliculi responsible for?
auditory reflex respone
what is the tegmentum of the midbrain a continuation of?
the pontine tegmentum
what are the cerebral peduncles?
crus + tegmentum
what is the cerebral aqueduct?
connection between the 3rd and 4th ventricle
what are the fiber tracts within the tectum of the midbrain?
posterior commisure
what does the posterior commissure do?
coordinate eye movements
list the fiber tracts in the tegmentum at the level of the inferior colliculus
- decussation superior cerebellar peduncle
- medial longitudinal fasciculus
- lateral lemniscus
- medial lemniscus
- trigeminothalamic
- spinothalamic
what info is carried in the decussation of the superior cerebellar peduncle?
efferent output from cerebellum crosses here
what info is carried in the medial longitudinal fasciculus?
balance with efferent limb of balance reflex
what info is carried in the lateral lemniscus?
afferent to inferior colliculus for auditory reflex
list the tracts located in the tegmentum of the midbrain at the level of the superior colliculus
- medial longitudinal fasciculus
- medial lemniscus
- trigeminothalamic
- spinothalmic
what are the crus cerebri?
descending axons from cerebrum that form corticospinal or corticobulbar tracts
divided into 4 segments
tracts in the most lateral segment of the crus cerebri are coming from where?
descending from parietal, temporal, and occipital cortex to pontine nuclei/cerebellum
tracts in the most medial segment of the crus cerebri are coming from where?
descending from frontal lobe to pontine nuclei/cerebellum
where is the corticospinal tract located in the crus cerebri
lateral middle segment
where is the corticobulbar tract located in the crus cerebri?
median middle segment
what nuclei are located in the tectum of the midbrain?
- inferior colliculus (auditory reflex)
- superior colliculus (visual reflex)
- pretectal region
what supplies the input to the inferior colliculus?
afferent input from:
cochlear, superior olivary, trapezoid nuclei via
lateral lemniscus
efferent output from the inferior colliculus heads where?
thalamus
via brachium of inferior colliculus (tectospinal)
what supplies the input to the superior colliculus?
retina
efferent output from the superior colliculus heads where?
cervical spine
via tectospinal for head turning, and tracking
where is the pretectal region located?
rostral to superior colliculus
what is the pretectal region responsible for?
papillary light reflex
associated with CN 3
what nuclei are located in the tegmentum of the midbrain at the level of the inferior colliculus?
- substantia nigra
- periaqueductal gray
- trochlear nerve nuclei
- reticular formation
what is the substantia nigra?
part of basal ganglia
motor efferent signaling
what is the periaqueductal gray responsible for?
autonomic regulation, emotion, and modulation of pain
what is the trochlear nerve nuclei CN 4 responsible for?
eye movement superior oblique muscle (down and medial)
what is in the reticular formation at the tegmentum of the midbrain at the level of the inferior colliculus?
raphe nuclei
list the nuclei that are located in the tegmentum of the midbrain at the level of the superior colliculus
- oculomotor nerve nuclei CN 3
- red nucleus
- ventral tegmental area
what is the function for the occulomotor nerve nuclei CN 3 in the tegmentum of the midbrain?
- somatomotor = S/M/I rectus, inferior oblique, levator palpebrae
- autonomic motor = iris constriction, ciliary muscle for accommodation (PNS component)
what is the red nucleus responsible for?
motor modulation of flexor muscles
via rubrospinal tract
what is the ventral tegmental area?
part of the basal ganglia motor modulators
what types of sensory information is associated with skin sensation?
- touch
- superficial pressure
- vibration
- pain
- proprioception
what type of sensory information is associated with musculskeletal sensation?
- proprioception
- pain
proprioception can be further broken down to include what?
- muscle stretch (tension)
- tendon stretch (tension)
- deep vibration
- joint position (angle)
- during movement
- while static
what are the different functional receptor types? (based off of stimuli)
- mechanoreceptors = stretch
- thermoreceptors = temperature
- chemoreceptors = any chemical stimuli
- nociceptors = pain
what are the different receptor types based off of response time?
- tonic = respond the entire time a stimulus is present
- phasic = adapt to a constant stimulus and stop responding while the stimulus is present
what type of receptor is slow adapting? Rapid adapting?
slow = tonic
rapid = phasic
what are the different types of sensory neurons?
- viscerosensory
- somatosensory
- special sensory
what are viscerosensory neurons?
general visceral afferent (GVA)
carry unconscious signals
what are somatosensory neurons?
general sensory afferent (GSA)
carry conscious singals
what are special sensory neurons?
special sensory afferent (SSA)
carry sensory info from special senses
what structural type of neuron are all viscerosensory and somatosensory neurons?
pseudo-unipolar
made up of:
peripheral (distal) axon/process → soma → central (proximal) axon/process
where are the soma of most sensory neurons located?
dorsal root ganglia
OR
cranial nerve sensory ganglia
most sensory information will travel in what fiber types?
II or Aβ: medium dia., myelinated
III or Aδ: small dia., myelinated
skin sensation is _______sensory
somatosensory
what is a receptive field?
an area of skin that is innervated by a single sensory neuron
what is the difference between a receptive field and a dermatome?
dermatome = single nerve
receptor field = single neuron
the sensation of touch can be broken down into what 2 categories?
Fine and Course touch
what type (specific names) of receptors are sensitive to fine touch?
- Merkel’s
- Meissner’s
- Pacinian
- hair follicle receptor
- Ruffini
what type (specific names) of receptors are sensitive to course touch?
- free nerve endings
pain is sensed by what type of receptor and carried by what type of neuron?
nociceptive receptors (a type of free nerve ending)
Aδ and C neurons carry pain signals
temperature is sensed by what type of receptor and carried by what type of neuron?
thermoreceptor
Aδ neurons carry cooling sensation and C neurons carry heat sensation
proprioception is primarily sensed by ________
musculoskeletal receptors
BUT
skin receptors make secondary contributions from stretch (Ruffini) and pressure changes
proprioception is awareness of joint position and movement that are a result from what receptors?
- muscle spindles
- joint receptors
- cutaneous mechanoreceptors
where are muscle spindles?
inside of a muscle, parallel to muscle fibers
structure is referred to as an intrafusal fiber
what are the components of a muscle spindle?
- nuclear chain muscle fiber
- nuclear bag muscle fiber
- afferent sensor/receptor
- gamma motor neuron
what are the 2 types of afferent sensor/receptor within a muscle spindle?
- annulospiral receptor/group Ia sensory neuron
- flower spray/group II sensory neuron
what do annulospiral receptors detect?
dynamic length/stretch (speed of contraction)
associated with both bag and chain intrafusal fibers
what do flower spray sensory neurons detect?
static length/stretch (static angle of the joint/degree of stretch)
what is the role of the gamma motor neuron within a muscle spindle?
when whole muscle contracts via alpha motor neurons the muscle spindle fibers (intrafusal fibers) may also contract via gamma motor neurons to keep the spindle stretched/tense so it will remain sensitive even when the whole muscle is shortening during contraction
what and where are Golgi tendon organs?
a proprioceptive receptor
found in dense CT of tendons
what is the role of Golgi tendon organs?
sensitive to changes in tension of the tendon
part of a reflex that inhibits muscle contraction to reduce stretch on muscle/tendon
list the different types of joint receptors
- Paciniform
- Ruffini
- free nerve endings
- ligament receptors
what do joint receptor sense?
mechanical deformation of joint capsule and ligaments
(they are mechanoreceptors that are sensitive to stretch)
what is the difference between a tract and a pathway?
- tract = a bundle of axons in CNS with a common origin and destination
- pathway = peripheral nerve + tract that together carry info to a final destination
T/F: pathways are isolated from one another and protected from interference?
FALSE
pathways can communicate and interact via collateral branches and interneurons
what are the 3 different classifications of pathways?
- conscious
- divergent
- unconscious
what is a conscious pathway?
a pathway that ends in the cerebral cortex
what is a divergent pathway?
a pathway that branches and ends in many CNS locations for both conscious and unconscious perception
what is an unconscious pathway?
a pathway that ends at brain locations below the cerebral cortex
(brainstem, limbic, cerebellum, diencephalon)
Information carried in different pathways can be described as/by ________, _________ and __________
- fidelity
- discriminative
- somatotopic
what is fidelity?
describes the location that the signal originates from
high = pinpoint location of origin
low = signals have a general origin
discriminative allows ____________
precise identification of stimuli
generally conscious pathways have what 3 characteristics?
- they are 3 projection neuron pathways
- carry touch, proprioception, pain and temperature info
- tracts are somatotopically organized (high fidelity)
List the conscious pathways
- Dorsal column/medial lemnsicus tracts
- Trigeminal nerve
- Spinothalamic tract
what info is carried in the dorsal column/medial lemnsicus tract?
- discriminative touch
- localization of stimulus
- 2-point discrimination
- conscious proprioception
- relative position and movement of body parts
what is sterognosis?
identification of an object by touch and proprioception
cortex accomplishes this by processing discriminative touch and proprioceptive info together
where/what is the primary/first-order neuron in the dorsal column/medial lemnsicus tract?
pseudo-unipolar neuron
carries signals from periphery to the medulla of the brain stem
describe the pathway of the distal axon to the soma of the first-order neuron in the dorsal column/medial lemnsicus tract
- discriminative touch and proprioceptor receptors
- peripheral nerve
- spinal nerve rami (dorsal or ventral)
- spinal nerve
- dorsal root
- DRG (this is the soma)
describe the pathway for the proximal axon to the synapse of the second-order neuron in the dorsal column/medial lemnsicus tract
- DRG
- dorsal root
- dorsal column of spinal cord
- fasciculus cuneatus/gracilis
- synapses in medulla w/second-order neuron
- nucleus cuneates/gracilis
where/what is the 2 order neuron in the dorsal column/medial lemniscus tract?
soma = nucleus cuneatus/gracilis
axons = cross midline and ascend to VPL of thalamus
where does the 3rd order neuron of the dorsal column/medial lemniscus tract originate and terminate?
soma of VPL of thalamus
thru internal capsule
to post central gyrus of parietal lobe
what type of sensory info is carried by the Trigeminal nerve?
- discriminative touch
- conscious proprioception
from face to contralateral cortex
describe the origin, soma and destination of the 1st order neuron in the trigeminal nerve pathway
- distal axon = receptors located in V1, V2, or V3 branch of the trigeminal nerve
- soma = trigeminal/semilunar ganglion outside of pons
- proximal axon = synapses with 1 of 2 nuclei in the pns
- main sensory = sensory info from face
- mesencephalic = proprioception of jaw
describe the origin and destination of the 2nd order neuron in the Trigeminal nerve
- origin
- soma of main sensory nucleus
- soma of mesencephalic nucleus
- axon = cross to contralateral side and ascend in trigeminal lemnsicus (part of medial lemnsicus)
- terminal synapse = VPM of thalamus
describe the origin and destination of the 3rd order neuron in the trigeminal nerve pathway
origin = VPM nucleus of thalamus
destination = post central gyrus via internal capsule
what type of sensory info is carried by the spinothalamic tract?
- discriminative pain
- temperature
- course touch
- non discriminative pleasant touch
- skin to skin contact
describe the origin and destination of the 1st order neuron carrying temperature sensation in the spinothalamic tract
- distal axon = receptors are free nerve endings
- soma = DRG
- proximal axon = synapses in dorsal horn
- Rexed’s laminae I and II = substantia gelatinosa
describe the origin and destination of the 2nd order neuron carrying temperature sensation in the spinothalamic tract
- soma = dorsal horn
- axon = crosses at spinal cord and ascends in the contralateral anteriolateral column
- this becomes the spinothalamic tract
- synapse = VPL nucleus of thalamus
describe the origin and destination of a tertiary neuron carrying temperature sensation in the spinothalamic tract
- origin = VPL nucleus of thalamus
- destination = post central gyrus
how are the neurons carrying localized, fast pain sensation in the spinothalamic tract different from those carrying temperature sensation?
Fast Pain
- receptors = nociceptors
- tertiary neurons headed to primary and secondary (associative) somatosensory cortex
T/F: fast pain from the face is carried within the trigeminal tract and has the same course as other sensations from the face?
FALSE
it is unique and will first descend to the medulla before ascending to the VPM
describe the origin and destination of primary neurons carrying fast pain sensation from the face (trigeminal)
- distal axon = nociceptive receptors
- soma = trigeminal/semiulnar ganglion
- proximal axon = descending tract of trigeminal nerve
- synapse = spinal nucleus of CN 5 in medulla
describe the origin and destination of the 2nd order neuron carrying fast pain sensation from the face
- origin = spinal nucleus of trigeminal nerve in medulla
- axon = crosses to contralateral side at the medulla and ascends in trigeminal lemnsicus
- synapses = VPM nucleus of Thalamus
describe the origin and destination of a tertiary neuron carrying fast pain from the face
- origin = VPM nucleus of thalamus
- destination = postcentral gyrus and associative cortex
Divergent pathways carry both __________ and ___________ signals
conscious
unconscious
the medial pain system is a divergent pathway that is generally responsible for carrying info used for what?
- pain modulation
- motivational
- withdrawal
- arousal
- autonomic reponse to pain
*low fidelity and not localizable
describe the origin and destination of a first order neuron in the medial pain system
- distal axon = nociceptor receptors
- soma = DRG
- proximal axon = branches to multiple spinal cord segments and synapses w/dorsal horn (lamina I, II, and V) using substance P as a NT
describe the origin and destination of a 2nd order neuron in the medial pain pystem
- origin = soma of dorsal horn
- axon = crosses to contralateral side in spinal cord then ascends in 1 of 3 divergent neurons
what are the 3 different divergent neurons that are 2nd order neurons in the medial pain system?
- spinomesencephalic
- spinoreticular
- spinolimbic
the spinomesencephalic tract is headed to what structures in the mesencephalon and for what purpose?
- superior colliculus
- turns head to position eyes on pain source
- activate descending neurons that modulate pain
- periaqueductal gray
- descending pain modulation
where is the spinoreticular tract headed?
what is it’s role?
reticular formation (raphe nuclei, locus ceruleus)
modulates pain sensation to thalamus
what is another name for the spinolimbic tract?
paleospinothalamic tract
where is the spinolimbic tract headed and what is it carrying?
- to anterior cingulated cortex = links pain sensation to emotional response
- to posterior insula = pain sensation
generally, unconscious pathways do what?
carry proprioceptive and feedback info about activity in motor tracts (via interneuron links) to cerebellum to adjust and refine conscious movement
what tracts are included in the unconscious pathways?
- posterior spinocerebellar
- cuneocerebellar
- anterior spinocerebellar
- rostrospinocerebellar
which unconsious pathways are high fidelty?
posterior spinocerebellar
cuneocerebellar
which unconscious pathways remain ipsilateraly?
posterior spinocerebellar
cuneocerebellar
rostrospinocerebellar
what is the posterior spinocerebellar tract?
2 neuron pathway carrying high fidelity, somatotopic info
from lower body to cerebellar cortex
on ipsilateral side
describe the origin and destination of a first order neuron in the posterior spinocerebellar tract
- distal axon = afferent signals from proprioceptors in legs and lower body
- soma = DRG
- proximal axon = ascends dorsal column
- synpases with = dorsal horn >> nucleus dorsalis in T1 to L2 region
describe the origin and destination of a 2nd order neuron in the spinocerebellar tract
- soma = nucleus dorsalis (dorsal horn)
- axon = ascends ipsilaterally as spinocerebellar tract to the medulla
- gets to cerbellum via inferior cerebellar peduncle
- synapses with cerebellar cortex ipsilaterally
what is the cuneocerebellar pathway?
2 neuron pathway carrying high fidelity, somatotopic info
from upper body to ipsilateral cerebellar cortex
describe the origin and destination of a first order neuron in the cuneocerebellar tract
- distal axon = afferent signals from proprioceptors in arms and upper body
- soma = DRG
- proximal axon = enters spinal cord and ascends in posterior column
- synapses = lateral (accessory) cuneate nucleus in medulla
describe the origin and destination of a second order neuron in the cuneocerebellar tract
- soma = lateral (accessory) cuneate nucleus of medulla
- axon = ascends in cunecerebellar tract until it enters the cerebellum via the inferior cerebellar peduncel
- synapses with ipsilateral cerebellar cortex
what is the anterior spinocerebellar tract?
1 neuron pathway that provides cerebellum with feedback from spinal cord ventral horn
monitors motor activity of lower body
describe the origin and destination of the neuronal pathway of the anterior spinocerbellar tract
- soma = interneurons of spinal cord in the thoracolumbar lateral and ventral horns
- axon crosses to contralateral side
- ascends in anterior spinocerebellar tract
- enteres cerebellum via superior cerebellar peduncle
- collaterals branch to synapse with both cerebellar hemispheres
what is the rostrospinalcerebellar tract?
1 neuron pathway that provides the cerebellum with feedback from spinal cord interneurons and motor activity of the upper body
describe the origin and destination of the neuronal pathway in the rostrospinocerebellar tract
- soma = interneurons of cervical spinal cord ventral horns
- axons asend ipsilaterally in the rostrospinocerebellar tract
- enter the cerbellum via the S/I cerebellar peduncles
- synapses w/ipsilateral cerebellar hemisphere
where are olfactory receptor cells located?
olfactory epithelium in the roof of the nasal cavity (ethomoid)
what is the olfactory epithelium composed of?
- olfactory sensory/receptor cells (hair cells)
- supporting cells
- basal stem cell
- olfactory glands
describe the structure of an olfactory sensory cell
bipolar neurons w/cilia (olfactory hairs) on the end of dendrite
T/F: the olfactory sensory/receptor cells are referred to as hair cells but are not neuron
FALSE
these ARE neurons
describe the supporting cells in the olfactory epithelium. What are they and what is their function?
mucous membrane lining of nasal cavity, neuroglia cells
function is to support, nourish, insulate, and detoxify olfactory receptor cells
what is unique about basal stem cells in the olfactory epithelium?
these are neuronal stem cells
olfactory receptor cells have a lifespan of 1 month and are then replaced
what is the function of the olfactory glands?
provide mucous to cover surface of olfactory epithelium to dissolve odor molecules so that they can interact with receptor cells
Describe the olfactory pathway up to the point that an AP is generated on CN 1
- odor molecule dissovles in mucous of nasal surface
- odor molecule binds to olfactory receptor protein (ligand binding)
- chemical interaction w/olfactory receptor opens chemical gated channels (Ca and Cl)
- graded potential on dendrite/soma in olfactory epithelium
- graded potenials sum at axon hillock to generate and AP on axon of olfactory receptor cell
describe the olfactory pathway from when an AP on CN 1 is generated to integration
- CN 1 axon goes through the cribiform plate to olfactory bulb
- signlas from olfactory receptor cell activate multiple cells in olfactory bulb for processing signals and discriminating signals
- olfactory bulb changes the pattern of signaling in response to a new odor
- olfactory tract carries new pattern to:
- ipsi and contralateral limbic structures
- temporal cortex
T/F: the olfactory bulb is always sending signals
TRUE
List the various ipsi and contralateral limbic structures
- Amygdale
- Entorhinal cortex
- hippocampus
- prefrontal cortex
- Insula
where is odor discrimination occuring?
temporal cortex
List the accessory structures of the eye
- eye lid
- eye brow
- eye lashes
- muscles
- lacrimal apparatus
what is the function of the eye lid?
protect the eye
what muscles and nerves are responsible for closing the eye lid?
obicularis occuli orbital and palpebral regions
CN VII
what muscles and nerves are responsible for opening the upper eyelid?
levator palpebrae superioris
CN 3
what is the inner lining of the eyelid called?
palpebral conjuctiva
it is continuous with the sclera
what is the function of the lacrimal apparatus?
what controls it?
produce lacrimal fluid (tears)
secreted superior/lateral and will flow diagonally to inferior/medial lacrimal canals which empty into nasal cavity
CN 7
List the extrinsic eye muscles
- Superior rectus
- inferior rectus
- lateral rectus
- medial rectus
- superior oblique
- inferior oblique
the eyeball can be divided into what 3 layers?
- fibrous outer layer
- Vascular middle layer
- retina-inner layer
