Neuro Flashcards
What are the steps of neurotransmission?
- Action potential reaches terminal
- Voltage gated Ca channels open
- Synaptic vesicles fuse with terminal membrane
- ACh released into synaptic cleft
- ACh binds to receptors
- Ligand gated Na/K channels open → end plate potential
- ACE degrades ACh
Which cranial nerves have general somatic efferent components?
3, 4, 5, 6, 7, 9, 10, 11, 12
Where are the cell bodies for spinal nerve GSE LMN for the thoracic limbs located?
C6-T2
Where are the cell bodies for spinal nerve GSE LMN for the pelvic limbs located?
L4-S3
Where is the cell body located for cranial nerve 3?
Oculomotor N
Midbrain
Where is the cell body located for cranial nerve 4?
Trochlear N
Midbrain
Where is the cell body located for cranial nerve 5?
Trigeminal N
Pons
Where is the cell body located for cranial nerve 7?
Facial N
Rostral medulla
Where is the cell body located for cranial nerve 9?
Glossopharyngeal N
Medulla
Where is the cell body located for cranial nerve 10?
Vagus N
Medulla
Where is the cell body located for cranial nerve 11?
Accessory N
Medulla
Where is the cell body located for cranial nerve 12?
Hypoglossal N
Medulla
What is the function of general somatic efferent fibers?
- Final motor innervation of muscles
2. Motor component of reflexes
What is the function of general somatic afferent fibers?
- Detect temperature, touch, and nociception
- For conscious awareness
- For reflex arcs
General somatic afferent fiber ascending tracts will reach the (ipsalateral/contralateral) cerebral cortex
CONTRALATERAL
What is the function of general proprioception pathways?
- Detects position and movement in muscles and joints
What are the components of all reflex arcs?
- Peripheral sensory component (GSA)
- Central Component
- In spinal cord for spinal reflexes
- In brain region for cranial nerve reflexes - Peripheral motor component (GSE)
A lesion anywhere in a reflex arc will lead to (increased/decreased) reflexes
Decreased
A spinal cord lesion cranial to a reflex arc can lead to (increased/decreased) reflexes
Increased
Withdrawal Reflex (Thoracic Limb)
- Spinal Cord Segment
- Nerves
- Muscles
- C6-T2
- All thoracic limb nerves
- All flexors
Patellar Reflex
- Spinal Cord Segment
- Nerves
- Muscles
- L4-L6
- Femoral n.
- Extensors
Withdrawal Reflex (Pelvic Limb)
- Spinal Cord Segment
- Nerves
- Muscles
- L6-S1
- Sciatic n.
- Flexors
Cutaneous Trunci Reflex
- Spinal Cord Segment
- Nerves
- Muscles
- C8-T1
- Sensory: Segmental spinal nerves.
Motor: Lateral thoracic nerve - Cutaneous trunci muscle
Perineal Reflex
- Spinal Cord Segment
- Nerves
- S1-S3
2. Pudendal
Anal Sphincter Tone
- Spinal Cord Segment
- Nerves
- Muscles
- S1-S3
- Caudal rectal n.
- External anal sphincter
Which cranial nerves are associated with the prosencephalon?
1 and 2
Which cranial nerves are associated with the midbrain?
3 and 4
Which cranial nerves are associated with the pons?
5
Which cranial nerves are associated with the medulla?
6-12
All cranial nerves enter/exit their respective brain region (ipsilaterally/contralaterally)
Ipsilaterally
The prosencephalon processes sensory information from (ipsilateral/contralateral) cranial nerves
Contralateral
- ex. visual information from the right eye is processed by the left cerebrum
Pupillary light reflex
- Sensory nerve
- Motor nerve
- Normal result
- CN 2
- CN 3
- Pupil constriction
Menace response
- Sensory nerve
- Motor nerve
- Normal result
- CN 2, contralateral cerebral cortex
- CN 7
- Blink
Palpebral reflex
- Sensory nerve
- Motor nerve
- Normal result
- CN 5
- CN 7
- Blink
Temporal muscle symmetry
- Sensory nerve
- Motor nerve
- Normal result
- -
- CN 5
- Should be symmetrical, no atrophy
Lip tone/symmetry
- Sensory nerve
- Motor nerve
- Normal result
- -
- CN 7
- Should be symmetrical
Physiological nystagmus
- Sensory nerve
- Motor nerve
- Normal result
- CN 8
- CN 3 and 6
- Fast phase in direction of movement
Fixed strabismus
- Sensory nerve
- Motor nerve
- Normal result
- -
- CN 3, 4, or 6
- Normal pupil vector
Positional strabismus
- Sensory nerve
- Motor nerve
- Normal result
- CN 8
- -
- Eyes track with head position
Nasal sensation
- Sensory nerve
- Motor nerve
- Normal result
- CN 5, contralateral cerebral cortex
- -
- Respond to noxious stimulus
Gag reflex
- Sensory nerve
- Motor nerve
- Normal result
- CN 9 and 10
- CN 9 and 10
- Cough/Repel finger
What are the functions of general visceral efferent fibers?
- LMNs of the autonomic nervous system
2. Innervate smooth muscle of blood vessels, visceral structures, glands, and cardiac muscle
Where are the preganglionic neurons located for the parasympathetic nervous system GVE?
- Brainstem nuclei of CN 3, 7, 9, and 10
2. Spinal cord segments S1-S3
Where are the preganglionic neurons located for the sympathetic nervous system GVE?
- Spinal cord segments T1-L4/5
What is the primary integrating center for the autonomic nervous system?
- Hypothalamus
Parasympathetic
The preganglionic axon is (long/short) and the postganglionic axon is (long/short)
- Long
2. Short
Sympathetic
The preganglionic axon is (long/short) and the postganglionic axon is (long/short)
- Short
2. Long
Postganglionic Neurotransmitter
- Parasympathetic
- Sympathetic
- ACh
2. Norepinephrine
Where are the preganglionic cell bodies located for the GVE parasympathetic
- Nuclei in midbrain and medulla
2. Nuclei in lateral horn of sacral spinal cord segments
What receptor is used for GVE parasympathetic neurotransmitters?
- Muscarinic ACh receptors
Where are the preganglionic cell bodies for the GVE sympathetic fibers located?
- Lateral/ventral horn of spinal cord segments T1-L4
The general visceral afferents travel to the CNS mainly through which cranial nerves?
- Facial n → from salivary and lacrimal glands
- Glossopharyngeal n → pharyngeal mucosa, caudal 1/3 of tongue, and carotid sinus
- Vagus n → larynx, trachea, esophagus, thoracic and abdominal viscera
- Vagus is 80% GVA fibers
- Cell body location: distal vagal ganglion
Which nucleus is shared by the general visceral afferents? Where is it located?
- Solitary nucleus
2. Medulla
What are the important GVE LMN components?
- Control of the pupils
- Control of micturition and defecation
- Control of the enteric system
- Control of the cardiorespiratory system
Describe the parasympathetic innervation to the eye
- Preganglionic cell body location
- Cranial nerve carrying preganglionic fibers
- Ganglion
- Effector organ
- Effect
- Parasympathetic nucleus of cranial nerve 3, rostral midbrain
- Cranial nerve 3
- Ciliary ganglion
- Postganglionic axons to the ciliary body
- Pupillary constriction
What would you expect with dysfunction of the parasympathetic portion of CN 3?
- Mydriasis
Describe the sympathetic innervation to the eye
- Preganglionic cell body location
- Cranial nerve carrying preganglionic fibers
- Ganglion
- Effector organ
- Effect
- UMNs from hypothalamus via lateral tectotegmentospinal tract
1. Lateral horn T1-T4
2. Ventral root → ramps communicans → sympathetic trunk → vagosympathetic trunk
3. Cranial cervical ganglion, pass through tympanic bulla, travel with CN V to orbit
4. Orbitalis muscle, ciliary body, pupillary dilator
5. Pupillary dilation
What is the only sensory system that lacks a thalamic nucleus for projection to the cerebral cortex?
Olfaction
An abnormal mentation indicates a general localization to which area?
Intracranial
If an animal is showing abnormal mentation there is a problem in either the ______ or ______.
- Prosencephalon (Telencephalon + Diencephalon)
* Rarely causes stupor or coma but can cause obtundation or dementia - Caudal Fossa (Midbrain, pons, medulla)
* Can lead to obtundation, stupor, or coma
Define
- Paresis
2. Plegia
- Decreased voluntary motor function
2. NO voluntary motor function (paralysis)
What would be indicated by short, choppy steps, crouched stance, look weak?
- LMN paresis/plagia
How would the gait of an animal with a LMN paresis/plageia appear?
Short, choppy steps, crouched stance, look weak
What would be indicated by long, lopey steps, exaggerated, look stiff?
- UMN paresis/plagia
How would the gait of an animal with an UMN paresis/plagia appear?
Long, lopey steps, exaggerated, look stiff
Where does a head tilt (eyes are not parallel to the floor) localize?
Vestibular
Where does a head turn (entire head facing one direction) localize?
Prosencephalon
When does decerebrate rigidity occur?
- Severe brainstem lesions
- Cerebrum is disconnected from brainstem
* UNCONSCIOUS
When does decerebellate rigidity occur?
- Cerebellum significantly affected
* NORMAL mentation
When does Schiff Sherrington posturing occur?
- Severe thoracolumbar spinal cord injury
2. ASCENDING UMNs from pelvic limbs to thoracic limbs are lost → loss of UMNs to pelvic limbs
White matter is (axons/cell bodies) and gray matter is (axons/cell bodies)
- Axons
2. Cell Bodies
The dorsal white matter is (ascending/descending) (sensory/motor) projections and are involved in _____.
- Ascending
- Sensory
- Postural reactions
The ventral white matter is (ascending/descending) (sensory/motor)
- Descending
- Motor
* These are upper motor neurons
The ventral horn cells bodies are what?
Lower motor neurons
UMNs are generally (excitatory/inhibitory) to the LMNs they synapse with
Inhibitory
Loss of LMNs to the pelvic limbs will affect which region of the spinal cord and will affect which muscular groups?
- L4-Caudal*
1. Pelvic limbs - Flaccid paraparesis/paraplegia
- Decreased/absent PL reflexes
- Decreased PL tone
2. External urethral sphincter - LMN urinary incontinence
- Constant dribbling
3. Anal sphincter - Dilated anus
- LMN fecal incontinence
What happens to the pelvic limbs with a T3-L3 lesion?
- Loss of UMNs*
1. Pelvic limbs - Spastic paraparesis/paraplegia
- Normal to increased PL reflexes
- Increased muscle tone
2. External urethral sphincter - UMN urinary incontinence
3. Loss of ascending sensory projections from pelvic limbs - General proprioceptive ataxia → crossing midline when walking
What happens in C6-T2 lesions?
- Loss of LMNs to thoracic limbs
- Flaccid paresis/plegia
- Decreased/absent TL reflexes
- Decreased/absent TL muscle tone - Loss of UMNs to pelvic limbs
- Spastic paresis/plegia
- Normal to increased PL reflexes
- Increased muscle tone
- GP ataxia
What happens in C1-C5 lesions?
- Loss of UMNs to both thoracic and pelvic limbs
- Spastic tetraparesis/tetraplegia
- Normal to increased TL and PL reflexes
- Increased muscle tone
What happens in diffuse neuromuscular lesions?
- Loss of LMNs to thoracic and pelvic limbs
- Flaccid tetraparesis/tetraplegia
- Decreased to absent TL and PL reflexes
- Decreased muscle tone x4
Neuromuscular disease (does/does not) affect ascending sensory projections. What does this mean?
- Does not
2. Postural reactions are intact → if there is enough motor function and the examiner is supporting
Lesions in the caudal fossa will have deficits (ipsilateral/contralateral) to the lesion
Ipsilateral
What deficits would you anticipate with a caudal fossa lesion?
- Abnormal mentation (obtundation, stupor, coma)
- Proprioceptive ataxia
- Upper motor neuron tetraparesis
- Cranial nerve deficits
- Reduced eye movements
- Increased pupil size
- Inability to close eyelids
- Abnormal gag reflex
Lesions in the prosencephalon will have deficits (ipsilateral/contralateral) to the lesion
Contralateral
The prosencephalon (is/is not) involved in gait generation
Is not
- NO GAIT DEFICITS with prosencephalic lesion
What are anticipated deficits with prosencephalic lesions?
- Abnormal mentation (obtundation/demented)
- Normal gait BUT circling TOWARD lesion, head turned TOWARD lesion
- Contralateral deficits
- Postural reaction deficits
- Cranial nerve deficits - Seizures = prosencephalon
What are the three anatomical components of the vestibular system?
- Peripheral vestibular system (CN 8 in inner ear)
- Central vestibular system (vestibular nuclei in rostral medulla)
- Flocculonodular lobe of cerebellum and caudal cerebellar peduncle
What are the four hallmarks of vestibular disease?
- Head tilt
- Vestibular ataxia
- Spontaneous nystagmus
- Positional strabismus
The cerebellum is inhibitory to the (ipsilateral/contralateral) vestibular nuclei
Ipsilateral
*The cerebellum tones down the ipsilateral vestibular system
The fast phase of nystagmus will be (toward/away from) the lesion with vestibular dysfunction
Away from
* The lesion will remove the vestibular input from the affected side, therefore the brain interprets this as an increase in input from the unaffected side → the brain thinks you are turning toward the unaffected side → nystagmus is generated away from the lesion