Through which pathway would a command from the brain to signal muscle contraction pass?
The command from the brain to signal muscle contraction would pass through the descending pathway.
The correct answer is option b) Descending pathway
Understanding the Descending Pathway:
The descending pathway is the neural pathway responsible for transmitting commands from the brain to the muscles, initiating muscle contraction. This pathway involves the brain sending motor commands to the spinal cord, which then relays these commands to the appropriate muscles.
What is the Descending Pathway?
The term "descending pathway" typically refers to neural pathways within the central nervous system that carry signals from higher brain centers to lower levels of the spinal cord. These pathways are involved in transmitting motor commands from the brain to the muscles, allowing for voluntary movements and motor control.
How Does the Descending Pathway Work?
To signal muscle contraction within the somatic nervous system, the brain uses the descending pathway. Axons of upper motor neurons travel from the CNS to form synapses with lower motor neurons in the spinal cord, which are part of the PNS and stimulate muscle activity.
Neural Transmission in the Descending Pathway:
The command from the brain to signal muscle contraction would pass through the descending pathway. This pathway is part of the somatic nervous system that governs voluntary movements. The descending motor pathways are responsible for conveying signals from the brain, specifically the motor areas of the cerebral cortex, down through the brainstem and into the spinal cord to reach the motor neurons that stimulate the muscles.
Structure of Neurons Involved:
When considering the structure of the neurons involved: neuron A would be in the central nervous system (CNS), and its axon would travel down to the spinal cord. Neuron A forms a chemical synapse with neuron B, through which the signal is transmitted using neurotransmitters. The axon of neuron B, which carries the signal to a skeletal muscle cell, is part of the peripheral nervous system (PNS) and represents an efferent nerve, as it carries information away from the CNS to elicit muscle contraction.
Role of Upper Motor Neurons:
The upper motor neuron's target is the lower motor neuron, which in turn innervates skeletal muscle, leading to contraction. Upper motor neurons reside in the CNS and their primary function is to carry motor information from the brain to the lower motor neurons in the spinal cord, which then directly control muscles.