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.