1.5- Reflexes and Cranial Nerves Flashcards
What happens when a spinal nerve is cut?
both motor and sensory fibers are destroyed
What type of cell bodies are found in the dorsal root ganglion?
sensory
What type of cell bodies is in the ventral horn of the SC?
Motor
What type of gated channel starts a sensory impulse?
modality
What starts a motor impulse?
an upper motor neuron
A modality gated receptor starts a sensory impulse, which is then carried along the neuron via _________.
voltage gated channels
A motor impulse is started by an upper motor neuron via a ___________ through a __________ and continues via _________.
synapse in the brain through a ligand gated channel and continues via voltage gated channel
After an upper motor neuron synapses it continues via the _______ until it reaches the ________ and causes a ________.
lower motor neuron (alpha motor neuron) until it reaches the motor end plate and causes a contraction
What is a reflex?
an involuntary response to a stimuli
What type of reflex is a multisynaptic reflex?
a withdrawal reflex
A withdrawal reflex is a _____________.
multisynaptic reflex
What type of reflex is a deep tendon (stretch) reflex?
monosynaptic reflex
What type of reflex is a monosynaptic reflex?
a deep tendon (stretch) reflex
What type of reflex occurs at the SC level- cortex not directly involved?
multisynaptic reflex (withdrawal reflex)
Explain a multisynaptic reflex from stimulation until it enters the SC.
sensory receptor is stimulated -> impulse travels along the peripheral process of the afferent nerve and into the dorsal root ganglion -> the central process of the afferent nerve continues into the spinal cord
In addition to a multisynaptic reflex going up the cord, the afferent neuron will _________.
synapse on an interneuron in the ventral horn -> the interneuron synapses onto an alpha motor neuron resulting in muscle activation to move a body part
Due to the multisynaptic interneuron synapsing in other areas of the SC, a LE reflex will also have influence over ______________.
the opposite extremity
- occurs with 1 single synapse (no interneurons)
- faster because fewer synapses
Monosynaptic reflex
When a muscle is quickly stretched it fires a _______.
modality gated sensory nerve
Monosynaptic reflex~
impulse travels ________ and synapses __________ -> stimulates a _________
impulse travels back to the spinal cord and synapses directly onto the motor neuron -> stimulates muscle contraction
If the CNS/brain influence is removed (like with spinal cord injury) a ___________ occurs
hyperactive reflex
- brain through descending control has an inhibitory effect
With a hyperactive reflex, brain through descending control has ____________.
an inhibitory effect
How many pairs of cranial nerves?
12 pairs
- some sensory, some motor, some both
Name the 12 cranial nerves in order.
Oh Oh Oh To Touch And Feel Very Good Vaginas And Hooters
- olfactory
- optic
- oculomotor
- trachlear
- trigeminal
- abducens
- facial
- vestibulocochlear
- glossopharyngeal
- vargus
- accessory
- hypoglossal
I. Olfactory
a.
b.
c.
a. sensory- sense of smell
b. only cranial nerve that goes directly into the cortex via the olfactory bulb
c. has large input into the brain (helps establish memory)
II. Optic
a.
b.
c.
a. sensory- visual input
b. very large & heavily myelinated- very fast
c. due to large amounts of myelin, it is susceptible to demyelinating diseases (MS)
III. Oculomotor a. b. c. d.
a. motor
b. controls 4 different eye muscles controlling eye movements up, down, and medial
c. controls eyelids opening
d. autonomic component- pupillary constriction, size of lens to focus eye
IV. Trochlear
a.
b.
a. motor
b. controls 1 eye muscle- turns eye down and in
V. Trigeminal
a.
b.
c.
a. both motor and sensory
b. sensory- sensation for areas of the face
c. motor- muscles of mastication (chewing)
VI. Abducens
a.
b.
c.
a. motor
b. turns eye lateral (Lateral Rectus)
c. primary control for coordination of eye movement
VII. Facial a. b. c. d. e.
a. both motor and sensory
b. sensory- taste (anterior 2/3 of tongue)
c. motor- muscles of facial expressions
d. autonomic- causes salivation & tearing of eyes
e. Corneal blink reflex- touch cornea & eyelid shuts
VIII. Vestibulocochlear
a.
a. sensory- hearing and balance (vestibular)
IX. Glossopharyngeal
a.
b.
c.
a. both sensory and motor
b. sensory- taster posterior 1/3 tongue & sensation back of throat
c. motor- helps with swallowing
X. Vagus a. b. c. d.
a. both sensory and motor
b. sensory- external ear sensation
c. motor- gag reflex (with IX- glossopharyngeal)
d. Autonomic- heart, lungs, viscera
XI. Accessory
a.
b.
c.
a. motor
b. arises in the SC, ascends up the cranium & then exits the cranium (not truly a cranial nerve)
c. trapezius & SCM (shrug should, turn head to opposite side; loss causes winging of the scapula)
XII. Hypoglossal
a.
a. motor- muscles of the tongue
What cranial nerves are motor, sensory, or both?
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