Examples of motor neuron in the following topics:
- There are upper and lower motor neurons in the corticospinal tract.
- These are the upper motor neurons of the corticospinal tract.
- These axons also synapse with lower motor neurons in the ventral horns.
- The midbrain nuclei include four motor tracts that send upper motor neuronal axons down the spinal cord to lower motor neurons.
- The lateral tract contains upper motor neuronal axons that synapse on the dorsal lateral lower motor neurons, which are involved in distal limb control.
- A reflex arc defines the pathway by which a reflex travels—from the stimulus to sensory neuron to motor neuron to reflex muscle movement.
- This characteristic allows reflex actions to occur relatively quickly by activating spinal motor neurons without the delay of routing signals through the brain, although the brain will receive sensory input while the reflex action occurs.
- The relay neuron in turn makes a synapse with one or more motor neurons that transmit the impulse to the muscles of the limb causing them to contract and pull away from the sharp object .
- When a reflex arc consists of only two neurons, one sensory neuron, and one motor neuron, it is defined as monosynaptic.
- It causes the stimulation of sensory, association, and motor neurons.
- The peripheral nervous system (PNS) consists of sensory neurons, motor neurons, and neurons that communicate either between subdivisions of the PNS or connect the PNS to the CNS .
- The nervous system has three broad functions: sensory input, information processing, and motor output .
- After information is processed, signals return to the PNS by way of motor neurons to muscles and glands, which respond with a motor output.
- Central neurons, which in humans greatly outnumber the sensory and motor neurons, make all of their input and output connections with other neurons.
- Electrical impulses travel along the axon of a neuron.
- A motor unit is comprised of a single alpha-motor neuron and all the muscle fibers it innervates.
- A motor unit consists of a single alpha motor neuron and all of the corresponding muscle fibers it innervates; all of these fibers will be of the same type (either fast twitch or slow twitch).
- The activation of more motor neurons will result in more muscle fibers being activated, and therefore a stronger muscle contraction.
- Motor unit recruitment is a measure of how many motor neurons are activated in a particular muscle.
- These small motor units may contain only 10 fibers per motor unit.
- Afferent neurons convey information from tissues and organs into the central nervous system (e.g. sensory neurons).
- Efferent neurons transmit signals from the central nervous system to the effector cells (e.g. motor neurons).
- Another way in which neurons are classified is by their effect on target neurons.
- A neuron releases a neurotransmitter that binds to chemical receptors on the target neuron .
- Other types of neurons include excitatory motor neurons in the spinal cord that release acetylcholine, and inhibitory spinal neurons that release glycine.
- The motor unit is the functional unit of muscle contraction and includes the motor nerve fiber and the muscle fibers it innervates.
- A motor unit consists of the motor neuron
and the grouping of muscle fibers innervated by the neuron.
- Thus, small motor units can
exercise greater precision of movement compared to larger motor units.
- Groups of motor units are innervated to
coordinate contraction of a whole muscle and generate appropriate movement; all
of the motor units within a muscle are considered a motor pool.
- These multiple motor units of different
sizes within a motor pool allow for very fine control of force either spatially
- A typical neuron consists of a cell body and neuronal processes such as dendrites and axon.
- These extensions are the conducting region of the neuron.
- The cell body is the major biosynthetic center of the neuron.
- Motor neurons receive signals from the brain and spinal cord to initiate muscle contractions and affect glands.
- 1: Unipolar neuron, 2: Bipolar neuron, 3: Multipolar neuron, 4: Pseudounipolar neuron
- A neuromuscular junction exists between the axon terminal and the motor end plate of a muscle fiber where neurotransmitters are released.
- A neuromuscular junction is the synapse or junction of the axon terminal of a motor neuron with the motor end plate, as shown in Figures 1 and 2.
- Upon the arrival of an action potential at the presynaptic neuron terminal, voltage-dependent calcium channels open and Ca2+ ions flow from the extracellular fluid into the presynaptic neuron's cytosol.
- Acetylcholine diffuses into the synaptic cleft and binds to the nicotinic acetylcholine receptors located on the motor end plate.
- The binding of acetylcholine at the motor end plate leads to intracellular calcium release and interactions between myofibrils to elicit contraction.
- They also help in the guiding the migration of young neurons.
- Astrocytes control the chemical environment around the neurons.
- Neurons consist of cell body and one or more slender processes.
- Arm like processes extend from the cell body to all neurons.
- Dendrites are motor neurons that are short and have a large surface area for receiving signals from other neurons.
- The motor areas of the brain are located in both hemispheres of the cortex.
- The right half of the motor area controls the left side of the body, and the left half of the motor area controls the right side of the body.
- Premotor cortex: Located anterior
to the primary motor cortex and responsible for some aspects of motor
- The majority of neurons in the motor cortex project to the spinal cord synapse on interneuron
circuitry in the spinal cord.
- $$Topography of the human motor cortex, including the premotor cortex, SMA, primary motor cortex, primary somatosensory cortex, and posterior parietal cortex.