PHYL 141L EXAM 3 Study Guide
19. What extrinsic eye muscle turns the eye down and laterally?
Superior Oblique Muscle
23. What extrinsic eye muscle turns the eye up and medially?
Superior Rectus Muscle
Why are fewer action potentials recorded at R2 when TTX is applied between R1 and R2?
TTX blocked the sodium channels, preventing the propagation of the action potential from R1 to R2.
What does TTX do to voltage-gated Na+ channels?
TTX blocks the diffusion of sodium through the voltage-gated sodium channels.
What elicits a stretch reflex?
Tapping on the Tendon
How did the action potential at R1 (or R2) change as you increased the stimulus voltage about the threshold voltage?
The action potential didn't change as the stimulus voltage increase. This is because once threshold is met, the event is all or none, not graded.
Why was there a difference observed in the amplitude of depolarization values between reflexes with and without reinforcement?
The brain is distracted
What is the importance of reflex testing in a routine physical examination?
The condition of the nervous system can be accessed
An action potential is an "all-or-nothing" event. Explain what is meant by this phrase.
This means that once threshold is met an action potential occurs. If the stimulus is too small an action potential does not occur.
Define the term threshold as it applies to an action potential.
Threshold is the voltage that must be reached in order to generate an action potential.
What nerve innervates the superior oblique muscle?
Trochlear Nerve
True or false, injury and pathology is indicated by exaggeration, distortion, or absence of reflexes normally present
True
What humor is in the vitreous chamber?
Vitreous Humor
What happened to the amount of neurotransmitter release when you switched from the extracellular fluid with no Ca2+ to the extracellular fluid with low Ca2+?
When a small amount of calcium is added back, a small amount of synaptic vesicles are released.
How does Mg2+ block the effect of extracellular calcium on neurotransmitter release?
When magnesium is added to the extracellular fluid, it blocks the calcium channels and inhibits the release of neurotransmitter.
A nerve is a bundle of axons, and some nerves are less sensitive to lidocaine. If a nerve, rather than an axon, had been used in the lidocaine experiment, the responses recorded at R1 and R2 would be the sum of all the action potentials (called a compound action potential). Would the response at R2 after lidocaine application necessarily be zero? Why or why not?
With a compound action potential, the results would not necessarily be zero because some axons would remain unaffected.
What is the response to the withdraw reflex?
Withdraw the body
What happened to the amount of neurotransmitter release when you switched from the control extracellular fluid to the extracelluar fluid with no Ca2+?
Without calcium present, no neurotransmitter was released because the exocytosis of the synaptic vesicles is dependent upon calcium.
Axon Collateral
branches off the axon
Spinal Nerve
bundle of axons outside the CNS
Ventral Root Ganglion
collection of motor nerve cell bodies within the CNS collection of motor nerve cell axon outside the CNS
Dorsal Root Ganglion
collection of sensory neuron cell bodies outside the CNS collection of sensory neuron central process outside the CNS
Axon
conducts and transmits nerve impulse
Axon Hillock
generates nerve impulse
Myelinated Sheath
insulates nerve fibers; increases the speed of impulse conduction
Multipolar
motor neurons are of this type of neurons interneurons are of this type of neurons
Interneuron
neuron serving as part of the conduction pathway between sensory and motor neurons; confined entirely to the CNS
Motor or Efferent
neuron that conducts impulses away from the CNS to the viscera and/or muscles and glands
Sensory or Afferent
neuron that conducts impulses toward the CNS from the body periphery
Dendrites and Cell Body
receptive regions of a neuron
Pseudounipolar
sensory neurons are of this type of neurons
Axon Terminal
stores and releases neurotransmitters
Neuron
the basic functional unit of the nervous system
What is the function of the ciliary body?
Change the shape of the lens
What structures are comprised in the vascular layer?
Choroid, Ciliary Body, and Iris
What 3 structures contain melanocytes and produce melanin to absorb strayed light rays to prevent visual confusion?
Choroid, Iris, and Retina
What channels are opened by an inhibitory interneuron?
Cl- Channels
Define reciprocal innervation
Contraction of agonist muscles result in simultaneous relaxation of its antagonist muscles to prevent conflict between opposing muscles
What role does the brain play in the patellar reflex?
Coordinating Movement
What structures are comprised in the fibrous layer?
Cornea and Sclera
What happened to the average amplitude of depolarization when the subject reinforces the patellar reflex by hooking together and pulling apart their flexed fingers?
Higher for reinforced reflex
Explain why increasing extracellular K+ reduces the net diffusion of K+ out of the neuron through the K+ leak channels
Increasing the extracellular potassium reduces the steepness of the concentration gradient and so less potassium diffuses out of the neuron.
21. What extrinsic eye muscle turns the eye up and laterally?
Inferior Oblique Muscle
25. What extrinsic eye muscle turns the eye down and medially?
Inferior Rectus Muscle
How does an inhibitory interneuron inhibit an action potential?
Inhibits by hyperpolarizing the neuron or stabilizing the resting membrane potential
What structure divides the anterior cavity into the anterior and posterior chamber?
Iris
What extrinsic eye muscle turns the eye laterally?
Lateral Rectus Muscle
What structure divides the interior of the eyeball into the anterior cavity and vitreous chamber?
Lens
Does fatigue result in a more or less vigorous reflex response?
Less vigorous
Why are fewer action potentials recorded at R2 when lidocaine is applied between R1 and R2?
Lidocaine blocked the sodium channels, preventing the propagation of action potential from R1 to R2.
What does lidocaine do to voltage-gated Na+ channels? How does the effect of lidocaine differ from the effect of TTX?
Lidocaine blocks the diffusion of sodium through the voltage-gated sodium channels.
Pain-sensitive neurons (called nociceptors) conduct action potentials from the skin or teeth to sites in the brain involved in pain perception. Where should a dentist inject the lidocaine to block pain perception?
Lidocaine should be applied to the receptors to prevent the generation of an action potential that would lead to the perception of pain.
What extrinsic eye muscle turns the eye medially?
Medial Rectus Muscle
Does mental distraction result in a more or less vigorous reflex response?
More vigorous
Does simultaneous muscle activity result in a more or less vigorous reflex response?
More vigorous
What is the receptor to muscle stretch?
Muscle Spindle
Where does the nerve impulse transmit to the conduction pathway?
Muscle spindle >>> Sensory Neuron >>> Axon collateral >>> Inhibitor Neuron >>> Hamstring Muscles
Where does the nerve impulse transmit to the conduction pathway?
Muscle spindle >>> Sensory Neuron >>> Axon collateral >>> Interneuron >>> Brain
Where does the nerve impulse transmit to the conduction pathway?
Muscle spindle >>> Sensory Neuron >>> Motor Neuron >>> Quadratic Femoris
Describe depolarization
Na+ channels are open; most channels open; goes inside the cell K+ channels closed Membrane Potential at +30mV
Describe resting membrane potential.
Na+ channels closed K+ channels closed Membrane Potential at -70mV
Describe hyperpolarization
Na+ channels closed K+ channels closed Membrane Potential at -90mV Na+/K+ Pump restores hyperpolarization back to resting membrane potential
Describe repolarization
Na+ channels closed K+ channels open; Most channels open; K+ flow out of the cell
Describe threshold.
Na+ channels open; some channels open; Na+ flow inside the cell K+ Channels closed Membrane Potential at -60mV No AP if depolarization never reaches the threshold
What is the receptor to potential dangerous stimuli?
Nociceptors
Where does the nerve impulse transmit to the conduction pathway?
Nociceptors >>> Sensory Neuron>>> Interneuron>>> Motor Neuron >>> Muscle
20. What nerve innervates the inferior oblique muscle?
Ocular Motor Nerve
22. What nerve innervates the superior rectus muscle?
Ocular Motor Nerve
24. What nerve innervates the inferior rectus muscle?
Ocular Motor Nerve
What nerve innervates the medial rectus muscle?
Ocular Motor Nerve
Which type of reflex is reciprocal innervation?
Polysynaptic Reflex
Define inhibitory synapse.
Presynaptic neuron takes membrane potential away from the action potential threshold
What muscles dilate the pupil in dim light and to distant vision?
Pupillary Dilator
What muscles constrict the pupil in bright light and to close vision?
Pupillary Sphincter
What muscle contracts in response to the patellar reflex?
Quadratic Femoris
Define reflex.
Rapid automatic response to a stimulus
What is the function of the cornea?
Refract Light Rays
What is the function of the lens?
Refract Light Rays
What structures are comprised in the nervous layer?
Retina Optic Disc
What muscles relax in response to the patellar reflex with reciprocal innervation?
Hamstring muscles
What structures connect to the interneurons that synapse with axon collaterals of a sensory neuron from a muscle spindle in the patellar reflex?
Hamstring muscles and brain
Explain why a change in extracellular Na+ did not alter the membrane potential in the resting neuron.
There are less leakage sodium channels that leakage potassium channels, and more of the potassium channels are open.
Discuss how a change in Na+ and K+ conductance would affect the resting membrane potential.
A change in the potassium conductance would have a greater effect on the resting membrane potential than a change in sodium would.
What change in membrane potential (depolarization or hyperpolarization) triggers an action potential?
A depolarization in the membrane potential results in an action potential. The membrane potential must become less negative to generate an action potential.
Define monosynaptic reflex
A monosynaptic reflex that does not involve interneurons
Define polysynaptic reflex
A reflex arc involves one or more interneurons
What nerve innervates the lateral rectus muscle?
Abducen Nerve
What factors contribute to the resting membrane potential?
An unequal distribution of ions; Inability of anions to leave the cell
What humor is in the anterior cavity?
Aqueous Humor
What forms the optic nerve?
Axon of the Ganglion Cells
What eye color does a person have if they have high amount of melanin on the anterior surface of the iris?
Black or Brown Eyes
What eye color does a person have if they have low amounts of melanin on the anterior surface of the iris?
Blue Eyes
What is the response to the patellar reflex?
Extension of the Leg
What is the function of the sclera?
Give the eye its shape; protect the inside; provide an attachment
What neurotransmitters are released by an inhibitory interneuron?
Glycine
Explain why increasing extracellular K+ causes the membrane potential to change to a less negative value.
The membrane potential becomes less negative because less potassium diffused out. If more potassium stays in, it is more positive or less negative.
How did neurotransmitter release in the Mg2+ extracellular fluid compare to that in the control extracellular fluid?
The neurotransmitter release was less when magnesium was added.
When the stimulus intensity is increased, what changes: the number of synaptic vesicles released or the amount of neurotransmitter per vesicle?
The number of synaptic vesicles released increases when the stimulus intensity increases.
Discuss the relative permeability of the membrane to Na+ and K+ in a resting neuron.
The resting neuron is 4-5 times more permeable to potassium because of the increased number of leakage channels.
What part of a neuron was investigated in this activity?
The trigger zone was investigated. This is where the axon hillock and the initial segment come together.