AP Biology : Understanding Afferent and Efferent Neurons
Study concepts, example questions & explanations for AP Biology
All AP Biology Resources
Example Questions
Example Question #1 : Understanding Afferent And Efferent Neurons
Which of the following correctly pairs the signal to the type of nervous pathway?
Blinking follows an efferent pathway
Cold water on your hand follows an efferent pathway
A bug walking on your leg follows an efferent pathway
Walking follows an afferent pathway
Breathing follows an afferent pathway
Blinking follows an efferent pathway
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 : Understanding Afferent And Efferent Neurons
Where do motor outputs from the brain exit the spinal cord?
Anterior root
Posterior root
Intervertebral foramen
Ventral root
Dorsal root
Ventral root
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?
Interneuron, efferent neuron, afferent neuron
Afferent neuron, interneuron, efferent neuron
Afferent neuron, efferent neuron, interneuron
Efferent neuron, interneuron, afferent neuron
Afferent neuron, interneuron, efferent neuron
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
sympathetic . . . parasympathetic
parasympathetic . . . sympathetic
peripheral nervous system . . . central nervous system
efferent . . . afferent
afferent . . . efferent
afferent . . . efferent
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 #1 : Understanding Afferent And Efferent Neurons
Afferent neurons are often associated with __________ function, while efferent neurons are often associated with __________ function.
motor or input . . . sensory or effector
sensory or input . . . motor or effector
sensory or effector . . . motor or input
motor or effector . . . sensory or input
sensory or input . . . motor or effector
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.
Certified Tutor
All AP Biology Resources
