Spinal Cord Nervous Tissue Quiz

The spinal cord is divided into different regions, namely cervical, thoracic, lumbar, and sacral. The pelvic region is not a division of the spinal cord. This is because the pelvic region refers to the lower part of the abdomen and pelvis, which is not directly associated with the spinal cord. Therefore, the correct answer is pelvic.

The spinal cord is composed of 31 pairs of spinal nerves. These nerves emerge from the spinal cord and branch out to various parts of the body. Each pair of spinal nerves is connected to a specific segment of the spinal cord, allowing for communication between the brain and different areas of the body. Therefore, the correct answer is 31.

A mixed nerve consists of both afferent and efferent fibers. Afferent fibers transmit sensory information from the peripheral nervous system to the central nervous system, while efferent fibers transmit motor information from the central nervous system to the peripheral nervous system. Therefore, a mixed nerve contains both types of fibers, allowing for the bidirectional transmission of signals between the central and peripheral nervous systems.

Descending tracts carry motor commands from the brain along the spinal cord. These tracts are responsible for transmitting signals from the brain to the muscles, allowing voluntary movement. They are part of the central nervous system and are located within the spinal cord. Descending tracts play a crucial role in coordinating and controlling movements throughout the body.

A reflex where the sensory input and motor output are on opposite sides of the spinal cord is called a contralateral reflex arc. This means that the sensory information is received on one side of the body and the motor response occurs on the opposite side. This type of reflex allows for quick and coordinated movements, as the sensory information can be processed and responded to rapidly.

A fracture of vertebra L4 would be the least likely to cause a spinal cord injury because the spinal cord ends at the level of the first lumbar vertebra (L1). Therefore, a fracture of vertebra L4 would be below the level of the spinal cord, reducing the risk of injury to the spinal cord.

Gray matter is a region in the central nervous system that contains the cell bodies (neurosomas) of neurons, along with their dendrites and the proximal parts of their axons. This is where most of the information processing occurs in the brain. The other options are incorrect because they either do not include the cell bodies and dendrites of neurons or include additional components such as glial cells, axons of motor neurons, and Schwann cells, which are not typically found in gray matter.

The correct answer is cauda equina. The cauda equina is a bundle of nerve roots that occupy the vertebral canal from L2 to S5. It is located below the level of the spinal cord and resembles a horse's tail, hence the name "cauda equina". This bundle of nerve roots is responsible for transmitting sensory and motor signals to and from the lower limbs and pelvic organs.

When the nurse pricks your finger and you flinch at the pain, pulling your hand back, this is an example of the flexor (withdrawal) reflex. This reflex is an automatic response that helps protect the body from potential harm. When the pain receptors in your finger are stimulated, sensory neurons send signals to the spinal cord, which then activates motor neurons to contract the muscles in your arm and pull your hand away from the source of pain. This reflex occurs without conscious thought and is a protective mechanism to prevent further injury.

The sensory function that involves neurons in the posterior root ganglia is touch. The posterior root ganglia are clusters of cell bodies located along the posterior roots of the spinal nerves. These ganglia contain sensory neurons that transmit touch sensations from the skin to the central nervous system. This allows us to perceive and interpret tactile stimuli such as pressure, temperature, and pain.

The sciatic nerve originates in the coccygeal plexus.

A muscle spindle is a sensory organ located within skeletal muscles that detects changes in muscle length and tension. It consists of specialized muscle fibers called intrafusal fibers, which are surrounded by connective tissue and sensory nerve endings. These muscle fibers are responsible for providing feedback to the central nervous system about muscle length and tension. Therefore, the correct answer is muscle fibers.

The correct answer is "to protect neurons in both the ascending and descending tract." The functions listed in the question all pertain to the role of the spinal cord in motor and sensory processing. However, the spinal cord does not have a specific function to protect neurons in both the ascending and descending tracts. Its primary role is to transmit motor commands from the brain to the body and sensory information from the body to the brain.

The patellar tendon reflex arc involves the stretching of the patellar ligament, which in turn stretches the quadriceps femoris muscle. This reflex causes the quadriceps femoris to contract, resulting in the extension of the leg. Additionally, the reflex also causes the antagonist muscles, the hamstrings, to relax. This is a normal response to maintain balance and stability during movements such as kicking or jumping.

Tendon organs are sensory receptors located in tendons that detect changes in muscle tension and provide information about the position and movement of the body. They are classified as proprioceptors because they contribute to proprioception, which is the sense of the body's position and movement in space. These receptors help the body maintain balance, coordination, and posture by providing feedback to the central nervous system about the length and tension of muscles.

Second-order neurons synapse with third-order neurons in the thalamus. The thalamus is a relay station in the brain that receives sensory information from various parts of the body and sends it to the cerebral cortex for further processing. In the sensory pathway, the first-order neurons transmit signals from the sensory receptors to the spinal cord or brainstem, where they synapse with second-order neurons. These second-order neurons then carry the signals to the thalamus, where they synapse with third-order neurons. The thalamus acts as a gateway, filtering and directing sensory information to the appropriate areas of the cerebral cortex for perception and interpretation.

The corticospinal tract is responsible for controlling voluntary movements, including handwriting. This pathway starts in the motor cortex of the brain and travels down the spinal cord, allowing signals to be transmitted from the brain to the muscles involved in handwriting. The other options listed are involved in different functions such as reflexes, coordination, and balance, but they are not specifically related to controlling handwriting.

White matter is the correct answer because it contains a high concentration of myelinated nerve fibers, which are composed mainly of lipids. Myelin is a fatty substance that surrounds and insulates nerve fibers, allowing for efficient transmission of electrical signals. Therefore, white matter, which is primarily made up of myelinated axons, has a higher lipid content compared to the other structures listed.

The cervical plexus is a network of nerves that originates from the spinal cord in the neck region. It supplies motor and sensory innervation to various structures in the neck and upper thorax. The phrenic nerve is one of the major branches of the cervical plexus. It arises from the third, fourth, and fifth cervical nerves and provides motor innervation to the diaphragm, the main muscle involved in respiration. Therefore, the correct answer is phrenic.

The posterior (dorsal) root of a spinal nerve contains somas of solely sensory neurons. This means that these neurons are responsible for transmitting sensory information from the body to the central nervous system. The other options, such as the anterior (ventral) root, posterior ramus, anterior ramus, and meningeal branch, do not exclusively contain sensory neurons.

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A nerve is a cordlike organ composed of numerous axons.

A ganglion is a cluster of neurosomas in the peripheral nervous system (PNS). Neurosomas are the cell bodies of neurons, and ganglia are collections of these cell bodies. Ganglia are found outside of the brain and spinal cord, and they play a role in processing and relaying sensory information. This explanation aligns with the given answer choice, which states that a ganglion is a cluster of neurosomas in the PNS.

The gracile fasciculus is an ascending tract of the spinal cord that carries sensory information related to proprioception, vibration, and deep touch from the lower limbs and lower trunk to the brain. It is located in the posterior column of the spinal cord and ascends on the same side of the body from where the sensory information is received. The other options listed are descending tracts or tracts that carry motor information, making the gracile fasciculus the correct answer.

Cerebrospinal fluid fills in the space between the arachnoid mater and pia mater. The arachnoid mater is the middle layer of the meninges, which are the protective membranes that surround the brain and spinal cord. The pia mater is the innermost layer of the meninges. The space between the arachnoid mater and pia mater is known as the subarachnoid space, and it is filled with cerebrospinal fluid. This fluid acts as a cushion, protecting the brain and spinal cord from injury and providing nutrients and waste removal for these structures.

The term somatosensory refers to sensory signals from various parts of the body, including the bones and muscles, joints, proprioceptors, and the skin. However, it does not include sensory signals from the viscera, which refers to the internal organs of the body.

The ventral rami of the spinal nerves form plexuses in all regions except the thoracic region. Plexuses are networks of nerves that form by the merging of ventral rami from adjacent spinal nerves. These plexuses are responsible for innervating different areas of the body. The brachial plexus is formed by the ventral rami of the spinal nerves in the brachial region, the cervical plexus is formed in the cervical region, the lumbar plexus is formed in the lumbar region, and the sacral plexus is formed in the sacral region. However, in the thoracic region, the ventral rami do not form a plexus but rather continue as intercostal nerves that innervate the muscles and skin of the thoracic wall.

The stretch (myotatic) reflex is the correct answer. This reflex occurs when a muscle is stretched, causing a reflexive contraction of that muscle to prevent overstretching or damage. In this scenario, as the person's head starts to lower due to nodding off, the stretch reflex is activated, causing the muscles in the neck to contract and raise the head back up. This reflex helps to maintain posture and prevent injury.

The endoneurium is a connective tissue layer that surrounds individual nerve fibers. It acts as a protective barrier and helps to keep the nerve fibers insulated from one another. This insulation is important because it allows for efficient transmission of electrical signals along the nerve fibers. The endoneurium also provides support and nutrition to the nerve fibers, helping to maintain their health and function.

The correct answer is the anterior horns. Upper motor neurons are responsible for carrying signals from the brain to the spinal cord, where they synapse with lower motor neurons. These synapses occur in the gray matter of the spinal cord, specifically in the anterior horns. The anterior horns contain cell bodies of lower motor neurons, which then send signals to the muscles to initiate movement.

The quickest reflex arcs involve only two neurons, thus forming monosynaptic reflex arcs. In a monosynaptic reflex arc, the sensory neuron directly synapses with the motor neuron, allowing for a rapid response to a stimulus. This direct connection between the sensory and motor neuron eliminates the need for additional processing and synaptic connections, resulting in a faster reflex response.

The correct answer is "special." This is because the statement "fibers innervate eyes and ears" refers to sensory fibers that are responsible for transmitting information from the special senses of vision and hearing. These special senses are distinct from the general senses (such as touch and pain) and the visceral senses (such as those related to internal organs). Therefore, the correct classification for the fibers innervating the eyes and ears would be "special."

The muscles of the hand have the most muscle spindles. Muscle spindles are sensory receptors located within the muscles that detect changes in muscle length and help regulate muscle contraction. The muscles of the hand are responsible for fine motor control and precise movements, requiring a high degree of proprioception. Therefore, they have a greater number of muscle spindles compared to other muscle groups like the back, thigh, middle-ear, and torso.

Reflexes are not spontaneous actions of the nervous system because they are involuntary and occur in response to sensory inputs. Unlike voluntary actions, reflexes do not require conscious thought or decision-making. They are quick responses that are triggered automatically and are often predictable.

Gamma motor neurons are responsible for maintaining the sensitivity of the muscle spindle. These neurons innervate the intrafusal muscle fibers within the muscle spindle, which are specialized sensory receptors that detect changes in muscle length and tension. By controlling the contraction of the intrafusal fibers, gamma motor neurons adjust the sensitivity of the muscle spindle, allowing it to accurately detect muscle stretch and contribute to the stretch reflex. This ensures that the muscle spindle can effectively provide feedback to the central nervous system about changes in muscle length, helping to regulate muscle tone and coordination.

Alpha motor neurons are responsible for carrying action potentials from the central nervous system to the skeletal muscles, causing them to contract. These neurons directly innervate the extrafusal fibers, which are the main contractile units of skeletal muscle. Gamma motor neurons, on the other hand, innervate intrafusal fibers, which are specialized muscle fibers found within muscle spindles. Anulospiral endings are sensory receptors found within muscle spindles that detect changes in muscle length and rate of change. Therefore, the correct answer is alpha motor neurons as they directly stimulate the contraction of skeletal muscles.

The tendon reflex prevents overcontraction of a muscle. When a muscle is being stretched, the tendon reflex is activated to protect the muscle from excessive contraction. This reflex causes the muscle to relax, preventing it from contracting too much and potentially causing damage. By inhibiting further contraction, the tendon reflex helps maintain the muscle's integrity and prevents it from overexerting or tearing.

The neurosomas of the posterior root are located in the posterior root ganglion, which is a collection of cell bodies of sensory neurons. On the other hand, the neurosomas of the anterior root are located in the gray matter, which is a region of the spinal cord that contains cell bodies of motor neurons.

The correct answer is the precentral gyrus of the cerebrum. The precentral gyrus is located in the frontal lobe of the cerebrum and is responsible for initiating voluntary muscle movements. It contains the primary motor cortex, which sends signals to the lower motor neurons in the spinal cord to control skeletal muscles.

The flexor (withdrawal) reflex involves the activation of a parallel after-discharge circuit. This circuit allows for a sustained contraction of the muscles involved in the reflex. After the initial stimulus, the circuit continues to send signals to the muscles, causing them to remain contracted for a longer period of time. This sustained contraction is important for the withdrawal reflex to effectively remove the body part from a potentially harmful stimulus.

The tendon reflex is the correct answer because it involves the least synaptic delay. In this reflex, the sensory neurons detect tension in a muscle tendon and send a signal to the spinal cord. The signal is then quickly relayed to motor neurons, causing the muscle to contract and relax. Since the reflex only involves a few synapses in the spinal cord, the transmission of the signal is faster compared to other reflexes that may involve more complex neural pathways.

An intersegmental reflex refers to a reflex that involves communication between different segments or levels of the spinal cord. In this scenario, when a bee sting on the right side causes a quick involuntary reaction of the right arm, it suggests that the reflex arc involves multiple segments of the spinal cord. The signal travels from the sensory receptor in the right arm to the spinal cord, where it is processed and then sent to the motor neurons that control the muscles in the right arm, resulting in the quick involuntary reaction. This indicates the involvement of multiple segments or levels of the spinal cord, making it an intersegmental reflex.