Tracts
Which tracts are in the Dorsal Medial area of the spinal cord?
Which are in the lateral column of the SC?
Which are in the ventromedial column of the SC? (McLean)
Dorsal/Medial- Dorsal Column Medial Leminscal tracts (take up the Fasiculus cuneatus and fasciculus gracilis) ASCENDING
Lateral column- corticospinal and rubrospinal DESCENDING!!! Also, dorsal/ventral spinocerebellar tracts and spinothalamic tract ASCENDING
ventromedial column - vestibulospinal tracts, reticulospinal tracts, corticospinal tract, tectospinal tract DESCENDING
The cochlea has 3 chambers associated with it. What are the 3 chambers and what do they contain?
What organ is housed in one of them? (Parsons)
Scala vestibuli - upper, contains perilymph
Scala tympani - lower, contains perilymph
Scala media - middle, contains endolymph and organ of corti!
What are the 3 things the hypothalamus controls and how? (vite)
Endocrine system - via pituitary gland
Autonomic nervous system (symp and parasymp) - via axon projections into this nervous system
Homeostatic behaviors - via connections to the forebrain, limbic system, brainstem, and spinal cord
The cells/axons that go into the DORSAL horn of the spinal cord are what type of cells? (Answer Afferent/efferent and sensory/motor) - What is special about these neuron's path?
The cells/axons that go out of the VENTRAL horn of the spinal cord are what type of cells? (McLean)
SENSORY AFFERENTS go into the dorsal horn of the SC- They have dorsal root ganglia where all their cell bodies are because the body comes off the middle of the axon
MOTOR EFFERENTS go from the ventral horn of the SC to peripheral tissues
**both of these are visceral AND somatic neurons (ones that control organ peristalsis, for example, and skeletal muscle)
What are the main uses of benzodiazepines in vet med? What receptors does this drug work on? (Gianotti)
Main uses: prevent muscle rigidity from ketamine, synergistic effect with other drugs so that you can use less induction agents, inhalants, and opioids (safer induction), first line for seizures
GABAa RECEPTORS ONLY
The corticospinal and rubriospinal tracts are what kind of tracts?
How many neurons do they have in series? Where do they originate, cross over, and terminate? (McLean)
DESCENDING MOTOR TRACTS with 2 neurons in series
The upper motor neuron originates in the Primary motor cortex
The upper motor neuron crosses over in the caudal medulla/SC junction and courses down the other side
The UMN and LMN synapse in the lateral white matter of SC and it innervates the desired muscle
Sweet, bitter, and umami tastes are produced by taste receptors via a 3 member family of GPCRS called T1R's (T1R1, T1R2, and T1R3). Which combination of 2 receptors creates the sweet receptor? What about an umami receptor? (Lewandowski)
**Bonus: One of the receptors is used twice in both combinations, which one would prevent you from not tasting these two tastes all?
Sweet: T1R2 and T1R3
Umami: T1R1 and T1R3
T1R3 is the most important!!!
What are the cellular layers of the cerebellum?
Can you explain how purkinje cells are operated and how they get information to the brain? (Vite)
Purkinje cell layer
granular cell layer
Afferent fibers are always excited (mossy and climbing fibers). They excite Purkinje cells which are always inhibitory fibers going from the cerebellum to cortex. When interneurons overcome the afferent fibers and tell the P cells to turn off, the neurone of the cerebellar nuclei and vestibular nuclei get to work properly and excite the cerebral cortex because they are no longer being smothered by inhibitory signals
If you were to have a laceration of the spinal cord in the level of the thoracic vertebrae (C6-T2), what symptoms would you see? Explain motor reflexes, paralysis type, and postural reactions for all the limbs (Vite)
Bonus points if you can tell me what disease happens concurrently to this injury in some animals
Front limbs: flaccid paralysis
Back Limbs: spastic paresis
Postural deficits will be ipsilateral to a lesion or in all legs if the injury was a through-and-through
Decreased sensation all limbs
Ipsilateral hyper (in hind) and hypo (front) reflexia
HORNER SYNDROME
What do alpha 2 agonists cause and what is the difference between the immediate and long-term effects?
Where do they act upon in the CNS (Gianotti)
bradycardia and hypertension (vasoconstriction)!
Immediate effects will cause vasoconstriction which will increase heart afterload so the heart will slow down. NOT DIRECT EFFECT ON HEART, it happens by proxy so DO NOT MEDICALLY INCREASE HEART RATE BECAUSE IT WILL HURT HEART. Reverse drug if necessary
Long-term effects: It tones down the Sympathetic NS which also causes bradycardia (looks the same as short term effects), but this time, you can give an anticholinergic to mess with the heart because the afterload is not being affected
They act upon the LOCUS COERULEUS.
The dorsal column medial lemniscal tracts is what kind of tract? How many neurons does it have
Where does it originate, cross over, and terminate? What is it’s function?(McLean)
ASCENDING SENSORY TRACT - vibration, touch, two point discrimination, and proprioception
Sensory nerve/afferent has a cell body in the dorsal root ganglion and goes into the SC (axon collaterals split out)
Axon travels up the DC of the white matter of the SC where is synapses with the secondary neuron at the medulla
Secondary axon crosses the body of the medulla and synapses with a third neuron in the thalamus
third neuron goes from thalamus --> cerebral cortex
What is the glomerulus when talking about olfaction? Does it contain cell bodies?
How does the olfactory system organize the inputs? (Lewandowski)
The glomeruli are the functional synaptic units of the olfactory bulb. Olfactory sensory neurons pick up a scent and send one axon to one glomerulus. The glomerulus is comprised of AXONS of these sensory neurons and they are being met with the dendrites/axons of the olfactory bulb interneurons. NO CELL BODIES HERE.
all activity associated with activation of a particular receptor is sent to one single glomerulus and they are able to compartmentalize all the different smells
What does each of these areas of the thalamus do? (hand)
Midline/medial nuclei
Intralaminar nuclei
Lateral thalamic nuclei
ventral tier thalamic nuclei
Midline/medial nuclei - functionally non-specific, state of consciousness/alertness?
Intralaminar nuclei - non-specific, integrate/modulate other thalamic nuclei?
Lateral thalamic nuclei - they project to specific areas of the cerebral cortex (ventral tier and dorsal tier groups)
ventral tier thalamic nuclei- sensory pathways that go to primary sensory receiving areas of the cerebral cortex. TOPOGRAPHIC ORGANIZATION
If you were just given a random cross-sectional slide of the SC, how would you know what level it is at (McLean)?
**Look at the shape and size of the grey matter!!
Cervical: The dorsal grey matter touches the outside of the SC. The ventral grey matter is small and pointed downward
Thoracic: Very small wings of the ventral AND dorsal grey matter
Lumbar: The dorsal grey matter touches the outside of the SC AND The ventral horn is very large
Sacral:
What receptor do phenothiazines and butyrophenones work on? Antagonist or agonist? Is this drug reversible? What is an example of the drug? (Gianotti)
Antagonist of the dopamine receptor
NOT REVERSIBLE
Acepromazine
What do the dorsal spinocerebellar tract and cuneocerebellar tracts do? Are they ascending or descending?
The outputs of the cerebellum have different functions. What are the functions of the cerebro-cerebellum, spinocerebellum, and vestibulacerebellum? (ANATOMY LAB PPT McLean)
Both ascending!
dorsal spinocerebellar tract - proprioception to the hindlimbs and lower trunk
cuneocerebellar tracts - proprioception to the neck, forelimb, and upper trunk
cerebro-cerebellum- motor learning
spinocerebellum - compare intended and actual movements
vestibular cerebellum - posture, balance, locomotion, and eye movements
What are the parts of the ANTERIOR segment of the eye?
What are the parts of the POSTERIOR segment of the eye? (Lassaline)
Anterior: Middle tunic of the Uvea (contains iris, ciliary body, and choroid) and Lens
Posterior: Vitreous humor, retina, choroid, and optic disc
What is the difference between the pre-motor cortex and the motor cortex? What types of behaviors would cause them each to light up? (McLean)
Pre-motor cortex is for PLANNING movements. If you sit and close your eyes and just think about playing piano, this area will light up
Motor cortex is ACTUAL MOVEMENTS. While physically moving your fingers while playing piano, this will light up
What are the components of the brainstem, and how do you know, on cross-section, which one you are at (McLean)?
midbrain (most cranial)-You DO NOT see any ventricles at all (you start to see a sliver of the 4th ventricle toward the end)
pons - You see the AQUEDUCT
medulla oblongata (most caudal) - you see the CEREBRUM
T/F: Injectable anesthetic drugs like propofol provide analgesia to the patient as well as unconsciousness
What is the effect of propofol on the respiratory and cardiovascular systems? (Driessen)
FALSE - there is none or no clinically relevant analgesic effect with many injectable anesthetics, they just make the patient unconscious so you need pain meds with them!
Resp- central respiratory depression. if you are passing out/sleeping, your RR is much much lower
Cardio- hypotension because of blood vessels dilating
The spinothalamic tracts is what kind of tract? How many neurons does it have? Where does it originate, cross over, and terminate? What is the function? (McLean)
SENSORY DESCENDING TRACT -- pain and temperature
1st neuron originates in the cerebral cortex and has its body in the DRG and goes to the spinal cord
synapses directly in the dorsal horn with 2nd neuron
2nd neuron crosses over immediately in the SC to the thalamus
in thalamus, 2nd synapsed with 3rd neuron to the cortex
Name the layers of the retina (you can do this from either direction - superficial to deep or deep to superficial). What cells can you see in the top and bottom layers? (Lassaline)
LIGHT
Nerve fiber layer- has retinal ganglion cells
Ganglion cell layer
inner plexiform layer
inner nuclear layer
outer plexiform layer
outer nuclear layer
photoreceptor layer - has cones and rods (end neuroretina)
retinal pigment epithelium
What thalamic nucleus goes to each of these sections of the telencephalon? (McLean)
Vision (cortical area V1)
Hearing (cortical area A1)
Somatosensory (cortical area S1)
Motor (cortical area M1)
Vision (cortical area V1) - Lateral geniculate nucleus
Hearing (cortical area A1) - Medial geniculate nucleus
Somatosensory (cortical area S1) - Ventral Posterior lateral/medial nucleus
Motor (cortical area M1) - Ventrolateral/Ventral
List the cranial nerves and tell me if they are somatic/visceral or Afferent/efferent
CN I - Olfactory nerve: Smell to the brain - Sensory
CNII - Optic nerve: Sensory, technically not a nerve but part of the eye that collects visual information and transmits it to the brain via axons
CNIII - Oculomotor: Motor, pupillary constriction/dilation, lens becomes more convex for close up vision (SE/VE)
CNIV - Trochlear: Motor (SE), tilts the eyeball
CNV- Trigeminal: Both motor for mastication and sensory for all face and head
CNVI - Abducent: Motor (SE only), rectus and retractor muscles of the eye
CNVII - Facial: Both sensory and motor (SE, VE, SA), muscles of facial expression, salivary gland secretion, and ear sensation. Taste buds on tip of tongue
CNVIII - Auditory/Vistibulocochlear: Sensory only, hearing and balance
CNIX- Glossopharyngeal: Both sensory and motor (SA, VA, SE, VE, and taste), innervation of the skin of ear, caudal tongue/pharynx for BP and chemoreception, swallowing, salivary secretion and caudal tongue receptors
CNX - Vagus: Both Sensory and motor ((SA, VA, SE, and VE). Sensory of skin of auditory canal, sensory to pharynx, larynx/trach/esoph/abd viscera, swallowing, respiration, vocalization, conduct taste info to the brain
CNXI - Accessory: Motor/SE, innervates the neck
CNXII - Hypoglossal: Motor/SE, innervates motor to the tongue for swallowing, chewing, and vocalizing
Where do inhalant anesthetics work on the CNS (x2)?
What is an MAC value? What types of things inc and dec it? (Driessen)
Spinal cord and brainstem to inhibit the sensations of pain from going up or down AND the brain for loss of consciousness and analgesia!
MAC= minimum alveolar concentration of an inhaled drug necessary to create desired effects (preventing motor response to a very noxious stimulus in 50% of subjects).
The MAC is dependent on patient parameters. You will need decreased MAC with inc age, pregnancy, hypothermia, and hypotension,and other drug interactions. The only clinically relevant thing that can INCREASE the MAC needed is hyperthermia