AP Biology : Neural Physiology

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #1 : Understanding Afferent And Efferent Neurons

Which of the following correctly pairs the signal to the type of nervous pathway?

Possible Answers:

A bug walking on your leg follows an efferent pathway

Walking follows an afferent pathway

Cold water on your hand follows an efferent pathway

Breathing follows an afferent pathway

Blinking follows an efferent pathway

Correct answer:

Blinking follows an efferent pathway

Explanation:

Efferent pathways carry signals away from the central nervous system. Essentially, they are signals that your brain sends to tell your body to do something, like blinking. Afferent signals come from outside stimuli and tell your brain what they are sensing, such as temperature. Afferent neurons bring stimuli to the brain, where the signal is integrated and processed. The brain then coordinates a response via efferent signals back to the rest of the body.

Example Question #1 : Neural Physiology

Where do motor outputs from the brain exit the spinal cord?

Possible Answers:

Dorsal root

Ventral root

Posterior root

Anterior root

Intervertebral foramen

Correct answer:

Ventral root

Explanation:

The ventral root of the spinal cord is located anteriorly, while the dorsal root is located posteriorly. Afferent neurons enter the spinal cord through the dorsal root, carrying signals from the body to the brain. Efferent neurons exit the spinal cord from the ventral root before interfacing with their target muscles.

Example Question #1 : Understanding Afferent And Efferent Neurons

Which of the following answers explains the typical succession of neuronal communication from receiving sensory input to generating a muscle response?

Possible Answers:

Afferent neuron, interneuron, efferent neuron

Interneuron, efferent neuron, afferent neuron

Efferent neuron, interneuron, afferent neuron

Afferent neuron, efferent neuron, interneuron

Correct answer:

Afferent neuron, interneuron, efferent neuron

Explanation:

The typical response pattern is that a sensory afferent neuron receives the external stimulus and communicates with an interneuron. The information is then interpreted, and a response is sent through efferent motor neurons to the appropriate portion of the body. Afferent neurons communicate information from the stimulus to the brain/spinal cord. Efferent neurons communicate information from the brain/spinal cord to the appropriate portion of the body.

Example Question #1 : Understanding Afferent And Efferent Neurons

If you touch a hot pan, __________ neurons tell your brain "it's hot!" and __________ neurons are used to quickly move your hand away

Possible Answers:

efferent . . . afferent

afferent . . . efferent

sympathetic . . . parasympathetic

peripheral nervous system . . . central nervous system

parasympathetic . . . sympathetic

Correct answer:

afferent . . . efferent

Explanation:

Afferent neurons are sensory neurons that carry nerve impulses from sensory stimuli towards the central nervous system and brain, while efferent neurons are motor neurons that carry neural impulses away from the central nervous systme and towards muscles to cause movement.

In this case, the afferent neuron would carry sensory information from your hand to your brain, letting it know your body is touching something hot. Your brain would then process this information and use efferent neurons to tell the arm muscle to contract and move your hand away.

Example Question #2 : Understanding Afferent And Efferent Neurons

Afferent neurons are often associated with __________ function, while efferent neurons are often associated with __________ function.

Possible Answers:

sensory or input . . . motor or effector 

motor or effector . . . sensory or input

motor or input . . . sensory or effector

sensory or effector . . . motor or input

Correct answer:

sensory or input . . . motor or effector 

Explanation:

A good way to remember afferent vs. efferent neurons is: Afferent Arrives, Efferent Exits.

Afferent neurons are neurons whose axons travel towards (or bringing information to) a central point, while an efferent neuron is a cell that sends an axon (or carries information) away from a central point. For example, if the central point in question is the brain, sensory neurons are afferent because they send information to the brain, while motor neurons are efferent because they carry information from the brain to effector organs like muscles or glands. It is crucial to keep in mind exactly which structure is the current focus of the discussion, since the terms "afferent" and "efferent" are relative to the direction of information transmission.

Example Question #21 : Nervous System

What kind of reflex does not require processing by the brain?

Possible Answers:

Monosynaptic reflex

Suckling reflex

Acoustic reflex

Accomodation reflex

Somatic reflex

Correct answer:

Monosynaptic reflex

Explanation:

Monosynaptic reflexes do not require a neuron between the pre-synaptic and post-synaptic neuron, and do not require input from the brain. These reflexes can be triggered even in brain-dead individuals. The knee-jerk reflex is an example of a monosynaptic reflex.

The accommodation reflex is used to adjust the focus of the eye. The acoustic reflex reduces sound intensity by adjusting the bones of the middle ear. The suckling reflex is the complicated reflex of an infant mammal being able to breast feed. Somatic reflexes are a broad category simply involving muscle reflexes. Some of these reflexes involve input from the brain, while others (like the knee-jerk reflex) do not.

Example Question #22 : Nervous System

Which of these physiological changes occurs when the sympathetic nervous system is activated?

Possible Answers:

Glucose is converted to glycogen

Rate of digestion increases

Heart rate increases

Reproductive processes are heightened

Pupils constrict

Correct answer:

Heart rate increases

Explanation:

The sympathetic nervous system is activated during times of stress, and is responsible for initiating the "fight or flight" response. Part of this response in an increase in heart rate, allowing better conduction of blood and delivery of oxygen throughout the body.

The other answer options are effects of parasympathetic stimulation, which allows for rest. During this time, the body stores energy from glucose into glycogen, and allows for digestion and reproduction.

Example Question #21 : Nervous System

Which of the following is true about cells at resting potential?

Possible Answers:

A sodium-potassium pump keeps the membrane polarized

There is a higher concentration of sodium inside of the cell

They have a resting potential of –30mV relative to the outside of the cell

There is a higher concentration of potassium outside of the cell

Correct answer:

A sodium-potassium pump keeps the membrane polarized

Explanation:

By pumping two positively-charged potassium molecules in for every three positively-charged sodium molecules that are pumped out of the cell, the sodium-potassium pump maintains a resting potential of –70mV relative to outside of the cell. This function is important for creating an electrochemical gradient along the neuron.

Remember that sodium flows down its gradient to enter the cell during depolarization, while potassium flows down its gradient to exit a cell after an action potential, causing hyperpolarization during the refractory period.

Example Question #1 : Understanding Action Potentials

The opening of a neuron's voltage-gated sodium channels is followed by all except which of the following actions?

Possible Answers:

Sodium continues to flood in due to a lower concentration of the molecule inside of the membrane

Action potential is propagated in both directions of the axon

Depolarization, as the membrane potential climbs to +35mV

Opening of the potassium channel to allow for repolarization of the membrane

Correct answer:

Action potential is propagated in both directions of the axon

Explanation:

After the sodium channel is opened, sodium rushes into the cell down its concentration gradient (as previously created by the sodium-potassium pump). This causes depolarization of the membrane as its potential reaches a value of +35mV, which is eventually lowered by the opening of the potassium channels. This leads to hyperpolarization, which prevents the signal from traveling backwards.

Example Question #2 : Understanding Action Potentials

Which of the following is characterized by having a membrane potential below –70mV?

Possible Answers:

Threshold

Refractory period

Resting potential

Action potential

Correct answer:

Refractory period

Explanation:

The refractory period, a phase in which action potentials cannot be fired, is the result of hyperpolarization, during which the membrane potential drops below –70mV. The membrane potential is at this –70mV level while the threshold, which needs to be reached to fire action potential, is slightly higher at –50mV. During the period of extreme hyperpolarization, an action potential will not form.

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