STUDY GUIDE Flashcards
What are the 4 structures of the forebrain?
- Cerebral cortex (telencephalon)
- Basal Ganglia (telencephalon)
- Thalamus (diencephalon)
- Hypothalamus (diencephalon)
What is the major structure of the midbrain?
- tectum (mesencephalon)
What are the 3 structures of the hindbrain?
- Cerebellum (metencephalon)
- Pons (metencephalon)
- Medulla Oblongata (myelencephalon)
What are the 3 divisions of the central nervous system?
- forebrain
- midbrain
- highbrain
what are the lobes of the brain?
FPOT frontal parietal occipital temporal
What is the fissure in the back? What does it separate
calcarine sulcus (or fissure) -separates parietal and occipital
what is the middle sulcus? What does is separate?
central sulcus
-separates frontal and parietal
what is the sulcus at the bottom?
lateral sulcus (or fissure) -separates frontal and temporal
What are the 3 planes of section?
- coronal
- sagital
- horizontal
What does the CNS comprise?
- Cerebrum
- Cerebellum
- Brainstem
- Spinal cord
What does the PNS comprise?
- somatic (voluntary)
- visceral (autonomic)
What is the primary difference between upper and lower motor neurons?
upper: movement planning
lower: movement execution
Where are upper neurons?
-In brainstem + cortex
Where are lower neurons?
-In spinal cord or brainstem
What are lower motor neurons?
-motor neurons that innervate proximal mucles
What is a motor pool?
group of motor neurons that innervate a single muscle (can comprise more than one type of motor unit)
What is a motor unit?
group of muscle fibers that receive input from a single motor neuron
What are smaller motor units responsible for?
fine movements (EX: soleus)
what are larger motor units responsible for?
course, forceful movements (jumping)
Which region of the spinal cord houses motor neurons?
Ventral horn + ventral roots (?)
Which type of muscle do you think would be more resistant to fatigue? Associated with posture or with attack/escape?
- smaller motor neurons generate lasting contractions
- posture
Smaller (S) alpha motor neurons
- conduct slowly
- innervate muscle fibers that generate small, lasting contractions (EX: postural muscles like soleus)
Larger (FF) alpha motor neurons?
- fast
- innervate larger groups of muscle that generate larger forces (EX muscles for jumping)
Intermediate (FR) alpha motor neurons
-innervate muscles with intermediate properties
When are gamma motor neurons likely to fire?
?
Which might trigger the reflex involves muscle spindles?
?
What are Group 1a sensory afferents? When are they most active?
- wrap around the bag and chain fibers
- most active when muscle length changes (EX stretching)
What are group II sensory afferents? When are they most active?
- wrap around chain fibers only
- most active when muscle is stretched
Nuclear bag
sensitive to rate of change in muscle length (velocity)
Nuclear chain
fibers sensitive to muscle length
What sort of information does the Golgi tendon organ convey, via which type of afferent?
- signal information about force (activity greatest when muscle contracts)
- capsules encasing group 1b afferents
What cortical regions supply the fibers that descend trough the corticospinal and corticobulbar tracts?
?
What are the 2 descending motor tracts that originate in the motor and premotor cortices?
- corticobublar (ends in brainstem)
2. corticospinal (ends in spinal cord)
The corticobulbar tract is ______ while the corticospinal tract _____ at the _____
- uncrossed
- crosses, midline
What is the anterior (ventral) corticospinal tract?
- crosses at the cord
- makes bilateral + polysynaptic connections with medial motor neurons that are used to maintain posture
What is the lateral cortico-spinal tract?
- comprises most of corticospinal tract
- originates from premotor cortex + primary motor cortex
What is a main difference between motor and premotor cortex?
Motor cortex: execution
Premotor cortex: planning
Which pathway acts as the accelerator and which as the brake on movements?
direct: accelerator
indirect: brake
Loss of dopamine correlates with which disease, Huntington’s or Parkinson’s?
Parkinson’s = loss of dopaminergic neurons in substania nigra
Loss of striatal neurons, on balance, results in which disease, Huntington’s or Parkinson’s?
Huntingtons = loss of striatum (caudate, putamen)
Dopamine _____ the direct pathway via ____ receptors
excites, D1
Dopamine _____ the indirect pathway via _____ receptors
inhibits, D2
Medium spiny cells that project to the _______ are ____ by dopamine D1 receptors
Glob. Pal. Int., excited
Medium spiny cells that project to the _______ are ___ by dopamine D2 receptors
Glob. Pal. Ext., inhibited
Does the loss of dopamine affect only one pathway or both?
- dopamine affects both pathways
direct: reduce disinhibition of thalamus
indirect: increases inhibition of thalamus
What is the movement deficit associated with loss of dopamine?
-rigidity, rolling pill tremor
What structure is hemiballismus it associated with?
- Ipsilateral loop that controls the contralateral side of the body
- Affects one subthalamic nucleus at a time
Why do you think that hemiballismus affects only one side of the body?
- only affects one sub thalamic nucleus
- controls
What are 6 muscles that move the eye?
- Superior rectus
- Inferior rectus
- Lateral rectus
- Medial rectus
- Superior oblique
- Inferior oblique
Which brainstem nuclei innervate the medial and lateral rectus muscles?
- Medial rectus – oculomotor nucleus
2. Lateral rectus – abducens nucleus
Which brainstem nuclei innervate the inferior and superior obliques?
- Superior oblique – trochlear nucleus
2. Inferior oblique – oculomotor nucleus
What is a saccade?
immediately direct our gaze somewhere else (jerky movements)
What is slow pursuit?
tracking targets as they move
What is conjugate eye movement?
bilateral fixation on a single object
Do vergence movements involve conjugate or disconjugate eye movements?
Vergence movements: eyes moving in opposite directions
-disconjugate eye movements
What happens to eye moments when the superior colliculus is damaged?
short term (not long term) loss in ability to make saccades(immediate direct gaze)
What happens when the frontal cortex (frontal eye fields) is damaged?
impairs ability to make voluntary movements away from
salient stimulus in visual field towards “remembered” positions
What happens if both structures are damaged?
permanent loss of ability to make saccades
What, in a nutshell, does the horizontal gaze center do?
?
Is there a motor map in the superior colliculus and, if so, how does it line up with the retinotopic map?
- The motor map and the visual map are both organized on spatial coordinates
- preservation of spatial relationship
- morphed/rotated
Sympathetic nervous system
fight or flight
Parasympathetic nervous system
rest and digest
What are ganglia?
clumps of cells (nerve cells) outside of CNS
Preganglionic
lies within CNS (output goes to ganglia)
Postganglionic
lies within PNS (output goes to effectors)
Where are preganglionic cells in the sympathetic nervous system?
lie in lateral horn in thoracic + lumbar
Where are the symapthetic ganglia?
lie in prevertebral sympathetic trunk (chain)
-remaining prevertebal ganglia tucked elsewhere
Where are preganglionic cells in the parasympathetic nervous system?
lie in brainstem + sacral vertebrae (S1-5)
Where are postganglionic nuclei in the parasympathetic nervous system?
near/within organs they innervate (unlike sympathetic)
Where are sympathetic postganglionic cells?
-paravetebral (sympathetic chain, ganglia, sympathetic trunk
What happens to heart rate when baroreceptors send signals that blood pressure is high?
afferents send impusles to brain stem, excites parasympathetic preganglionic cells
What happens when blood pressure is low?
Noradrenaline release is reduced
Vagus nerve
projects directly to neurons in wall of gut (input from parasympathetic)
Preganglionic (receptor class)
nicotinic receptors (ionotropic)
Postganglionic (receptor class)
noradrenergic
Parasympathetic (receptor class)
muscarinic receptors (metabotropic, G proteins)
Myenteric plexus
controls smooth muscle
Submucosal plexus:
controls secretions
Why are the white communicating rami white?
-axons myelinated (of preganglionic neurons)
Why are the gray communicating rami gray?
axons unmyelinated (of post ganglionic neurons)
What do white communicating rami do?
-help neurons reach sympathetic chain ganglia
What do gray communicating rami do?
-help axons reach effectors
It there ever an intersection of the somatic and visceral systems?
Yes, they do intersect? (EX: peeing?)
What is a peduncle?
fiber bundles carrying inputs and outputs
What are the 3 cerebellar cortical zones?
- Dentate
- Interposed
- Fastigial
Dentate
Input: cerebrocerebellar zone
Projects to: contralateral premotor cortex + association cortices of frontal lobe (planning)
Interposed
Input: spinocerebellar zone
Projects to: contralateral motor cortex (executing)
Fastigial
Input: spinocerebellar zone
Projects to: upper motor neurons in ipsilateral brainstem (executing)
Where does the vestiublocerebellum project?
To the vestibular nuclei
Afferent
arrives
Efferent
exits
What are the 3 types of peduncles?
- superior
- middle
- inferior
What is the superior peduncle?
- efferent pathway(mainly)
- made of fibers exiting from deep cerebellar nuclei
What is the middle peduncle?
- afferent pathway
- made of fibers carrying information from the cortex (via pons)
What is the inferior peduncle?
afferent fibers from brainstem + spinal cord
-efferent fibers from eh vestibulocerebellum
Do all peduncles carry afferent or efferent information or is one or more “mixed”?
-inferior peduncle is mixed afferent and efferent
What is the function of the cerebrocerebellum division?
influences premotor cortex via the dentate (planning)
What is the function of the spinocerebellum division?
influences motor cortex via interposed nuclei (execution)
-influences brainstem structures via fastigial nucleus (execution)
What is the function of the vestibulocerebellum division?
projects directly to vestibular nuclei (adjustment, balance)
What are climbing fibers?
- convey input from inferior olive
- mediates motor learning + involves complex spikes
- originate in inferior olive vs pontine nuclei
What is the climbing fiber loop?
- detect errors + correct them over longer term
- learning loop
- monkey learns to compensate for changes
Why is light adaptation in rods and cones important?
- sensitivity of phototransduction cascade could lead to early saturation
- adaption dependent on Ca2+
- decrease of Ca2+ increases activity of rhodopsinkinase
Why is arrestin important?
-arrestin interferes with ability of metarhodopsin to activate transducin
(tranducin mediates most amplified step of phototransduction cascade)
What are 2 characteristics of rods?
- code for black and white
2. discs stacked in the membrane
What are 3 characteristics of cones
- faster at conducting receptor potentials
- code for color
- condensed in the fovea
Where is the region in the visual field (think in terms of retinal coordinates) in which our acuity is greatest?
-acuity is greatest in the fovea
What is the fovea?
- highest concentration of cells in foveal pit
- tightest packing density
- only cones
Cones are _____ in the periphery
widely spaced
Off bipolar cells like change from ____ to _____
brighter to darker
On bipolar cells like change from ______ to _______
dark to brighter
ganglion cells in off bipolar are tonically _____
excited
ganglion cells in on bipolar are tonically _____
inhibited
Which cells are involved in generating the center + surround of the receptive field of a bipolar cell?
horizontal cells generate surround
What are horizontal cells?
- receive excitatory input from photoreceptors (sign-conserving synapses)
- inhibit (sign-inverting synapse) photoreceptors in return
- connected to each other via gap junctions
most of the visual field is seen by _____
both eyes
____ side of the brain sees ____ visual field
contralateral, ipsilateral
What is the pathway for binocular representations of visual field?
- retinal axons travel from eye to thalamus
- project to cortex
- myelinated axons of relay cells form thick stripe in V1
How do the response properties of cells in retina differ from those of cells in V1?
-there is no orientation selectivity in the retina
What is an orientation column
- vertically aligned cells across cortical depth
- share same pref for stimulus orientation
- overlapping visual fields
Ocular dominance column
-important for ability to judge depth
What is a hypercolumn?
-region that represents one point in visual space
(receptive fields are overlapping
-orientation analyzed for all permutations
What are the 2 different visual streams?
- P ganglion cell - ventral
2. M ganglion cell - dorsal
What is the dorsal stream? where does it end up?
- “where,” spatial
- parietal lobe
What is the ventral stream? where does it end up?
- “what,” form/object recognition
- temporal lobe
What do lesions in the dorsal (M) stream lead to?
akinetopsia (motion blindness)
What doe lesions in the ventral(P) stream lead to?
- achromatopsia (V4)
- prosopagnosia (fusiform face area)
What does the middle ear do?
- Impedance Matching
2. Gating (protect inner ear from loud noises), reduce transmission efficiency of ossicles
How would your hearing suffer without the middle ear?
-too loud of sounds
Why have a pinna?
- grooves/hollows act like filters + resonance chambers
- alter spectrum of sound that reaches cochlea
- some amplified, others dampened
What is the principal role of the basilar membrane?
- location of (inner) hair cells (rocks up and down)
- basilar membrane bends hair cells bend
- K+ enters depolarize (towards)
- K+ does not enter hyperpolarize (away)
What is the principal role the tectorial membrane?
location of (outer) hair cells (sheers back and forth)
What is the difference in the roles played by inner vs. outer hair cells?
Inner hair cells: sends signals to the brain
Outer hair cells: amplification
What is the mechanical basis for the hair cell receptor potential:
- basilar membrane rocks up and down
- tectorial membrane sheers
- stereocilia of the OHCs are bent in tectorial membrane, depolarized
How is tonotopy achieved – what properties (width, stiffness) of the basilar membrane (base vs apex) lead to resonances at different frequencies? How is tonotopy maintained in the central auditory pathway?
- mechanical properties of basilar membrane organizatinos of freq. from high(base) low(apex)
- each fiber responds best to the frequency that it is most effective in driving its presynaptic hair cell
Do the outer, middle and inner ear all help to amplify sound in some way? How or how not?
Outer
-pinna, resonance chambers
Middle
- impedance matching/concentrating force
- small surface area of the oval window
- lever system with ossicles
Inner
-outer hair cells amplify sound
Bushy cells
cells: preserve stimulus timing (Anteroventral Cochlear Nucleus, AVCN)
Stellate cells
head acts as sound shadow, interaural intensity differences
What are the two main ways we localize sound in the azimuthal (horizontal) plane?
Low frequencies: coincidence detecting circuits in MSO
high frequencies: head acts as sound shadow, interaural intensity differences
Does the pinna help localize sound in the vertical plane?
used for monaural sound localization
How do (should) the two main types of auditory cortex (core and belt) remind you of the dorsal and ventral streams of visual processing?
Core: where pathway
Belt: what pathway
What are the two main types of organ in the labyrinth?
Otolith organs: utricle + sacculus
Semicircular canals: superior, posterior, horizontal
Otolith organs
-detect linear acceleration + head position
Semicircular canals
-signal information about rotational motion
What is the main difference between the two otolith organs?
Utricular macula plane: roughly horizontal
Saccular macula plane: roughly vertical
Amblyopia
- reduced vision through an eye
- even when optics of that eye are ultimately repaired
What is strabismus? Name two types.
Strabismus: deficits caused by the inability of the two eyes to focus on the same target
Esotropia: one eye deviates inwards
Extropia: one eye diviates outwards
