Chapter 14 Flashcards
The three components of the PNS are:
A) Sensory receptors, nerves, and motor endings
B) Sensory receptors, nerves, and reflexes
C) The brain, the spinal cord and nerves
D) Cranial nerves, spinal nerves, and reflexes
A) Sensory receptors, nerves, and motor endings
Explanation: The Peripheral Nervous System (PNS) consists of the following components:
Sensory receptors: These detect changes in the environment and send this information to the central nervous system.
Nerves: These are bundles of axons that carry sensory information to the CNS and motor commands from the CNS to the muscles and glands.
Motor endings: These are the terminations of motor neurons that connect to muscles and glands, enabling them to respond to commands from the CNS.
These components work together to connect the central nervous system to the rest of the body, facilitating sensory input and motor output.
The two major branches of the peripheral nervous system (PNS) are the ___________________ and __________________ divisions.
A) Somatic motor and autonomic motor
B) Somatic sensory and visceral (autonomic) sensory
C) Sympathetic and parasympathetic
D) Sensory and motor
D) Sensory and motor
Explanation: The Peripheral Nervous System (PNS) has two major branches:
Sensory (afferent) division: This branch transmits sensory information from sensory receptors to the central nervous system (CNS). It includes sensory receptors that detect stimuli such as touch, pain, temperature, and proprioception.
Motor (efferent) division: This branch carries motor commands from the CNS to muscles and glands. It includes the somatic nervous system (which controls voluntary movements by innervating skeletal muscles) and the autonomic nervous system (which controls involuntary functions by innervating cardiac muscle, smooth muscle, and glands).
These two divisions ensure that the PNS effectively communicates between the body and the CNS.
Sensory receptors are nerve endings specialized to respond to changes in the environment.
True
False
True
Explanation: Sensory receptors are indeed nerve endings specialized to respond to changes in the environment. They detect various stimuli such as light, sound, temperature, pressure, and chemical changes, and then send this information to the central nervous system for processing.
Mechanoreceptors of the peripheral nervous system respond to touch, pressure, vibration and stretch.
True
False
True
Explanation: Mechanoreceptors of the peripheral nervous system respond to mechanical stimuli such as touch, pressure, vibration, and stretch. These receptors play a crucial role in sensing physical changes in the environment and transmitting this information to the central nervous system.
Nerves found in the PNS carry either sensory or motor fibers.
True
False
False
Explanation: Nerves found in the PNS can carry sensory fibers, motor fibers, or both. These mixed nerves are quite common and contain both afferent (sensory) and efferent (motor) fibers, allowing them to transmit sensory information to the CNS and carry motor commands from the CNS to the muscles and glands.
Most spinal and cranial nerves contain both somatic and autonomic fibers.
True
False
True
Explanation: Most spinal and cranial nerves contain both somatic and autonomic fibers. This allows them to transmit both voluntary motor commands (somatic) and involuntary motor commands (autonomic) to various parts of the body, as well as receive sensory information from both somatic and autonomic sensory receptors.
The 31 pairs of spinal nerves innervate all parts of the body including the head and neck.
True
False
False
Explanation: The 31 pairs of spinal nerves innervate most parts of the body, but the head and neck are primarily innervated by the cranial nerves. The spinal nerves primarily provide sensory and motor innervation to the trunk and limbs. Cranial nerves, which emerge directly from the brain, are responsible for the sensory and motor functions of the head and neck.
Which of the following statements about nerves is not true?
A) Nerves are bundles of axons.
B) The connective tissue sheath that surrounds a fascicle of nerve fibers (axons) is the endoneurium.
C) Nerves found in the PNS carry both sensory and motor fibers.
D) Nerves found in the PNS are usually a mix of somatic and autonomic fibers.
E) All are true statements.
B) The connective tissue sheath that surrounds a fascicle of nerve fibers (axons) is the endoneurium.
Explanation: The correct term for the connective tissue sheath that surrounds a fascicle of nerve fibers is the perineurium. The endoneurium is the connective tissue that surrounds individual nerve fibers (axons) within a fascicle.
Which of the following statements about cranial nerves is not true:
A) There are 12 pairs of cranial nerves.
B) The cranial nerves only innervate the head and neck.
C) Most cranial nerves are mixed sensory and motor, though two are purely sensory.
D) The vagus nerve is the only cranial nerve that travels to the thoracic and abdominal cavities.
E) All are true statements.
B) The cranial nerves only innervate the head and neck.
Explanation: This statement is incorrect because the vagus nerve (cranial nerve X) travels beyond the head and neck to innervate structures in the thoracic and abdominal cavities.
Which of the following statements about spinal nerves is not true:
A) The 31 pairs of spinal nerves innervate all parts of the body other than the head and part of the neck.
B) The spinal nerves carry both sensory and motor fibers.
C) Rami carry both sensory or motor fibers.
D) The dorsal roots contain motor fibers from ventral horn motor neurons.
E) All are true statements
D) The dorsal roots contain motor fibers from ventral horn motor neurons.
Explanation: This statement is incorrect because the dorsal roots contain sensory fibers, not motor fibers. The motor fibers are located in the ventral roots, which carry motor commands from the ventral horn motor neurons to the muscles and glands.
Which of the following divisions is responsible for transmitting information from sensory receptors to the CNS?
A) Motor division
B) Sensory division
C) Autonomic nervous system
D) Sympathetic division
B) Sensory division
Explanation: The sensory (afferent) division of the PNS involves sensory neurons that send information from sensory receptors to the CNS.
Which type of sensory receptor responds to chemical stimuli?
A) Mechanoreceptors
B) Thermoreceptors
C) Photoreceptors
D) Chemoreceptors
D) Chemoreceptors
Explanation: Chemoreceptors respond to chemical stimuli, such as those involved in smell, taste, and changes in blood chemistry.
Which connective tissue layer surrounds a fascicle of nerve fibers?
A) Endoneurium
B) Perineurium
C) Epineurium
D) Myelin sheath
B) Perineurium
Explanation: The perineurium is the connective tissue sheath that surrounds a fascicle of nerve fibers (axons).
Which cranial nerve is the only one that extends into the thoracic and abdominal cavities?
A) Vagus nerve
B) Trigeminal nerve
C) Optic nerve
D) Facial nerve
A) Vagus nerve
Explanation: The vagus nerve (cranial nerve X) extends beyond the head and neck to innervate structures in the thoracic and abdominal cavities.
Which statement about spinal nerves is not true?
A) The 31 pairs of spinal nerves innervate all parts of the body other than the head and part of the neck.
B) The spinal nerves carry both sensory and motor fibers.
C) Rami carry both sensory or motor fibers.
D) The dorsal roots contain motor fibers from ventral horn motor neurons.
D) The dorsal roots contain motor fibers from ventral horn motor neurons.
Explanation: The dorsal roots contain sensory fibers, not motor fibers. Motor fibers are located in the ventral roots.
Sensory receptors are nerve endings specialized to respond to changes in the environment.
True
False
True
Explanation: Sensory receptors are specialized nerve endings that respond to various environmental changes or stimuli.
Mechanoreceptors of the peripheral nervous system respond to touch, pressure, vibration, and stretch.
True
False
True
Explanation: Mechanoreceptors are sensitive to mechanical changes such as touch, pressure, vibration, and stretch.
Nerves found in the PNS carry either sensory or motor fibers.
True
False
False
Explanation: Nerves in the PNS can carry sensory fibers, motor fibers, or both (mixed nerves).
Most spinal and cranial nerves contain both somatic and autonomic fibers.
True
False
True
Explanation: Most spinal and cranial nerves contain both somatic and autonomic fibers, allowing them to perform both voluntary and involuntary functions.
The 31 pairs of spinal nerves innervate all parts of the body including the head and neck.
True
False
False
Explanation: The spinal nerves innervate most parts of the body, but the head and neck are primarily innervated by cranial nerves.
The peripheral nervous system (PNS) can be divided into two major branches: the ___________ and ___________ divisions.
Sensory, motor
Explanation: The PNS is divided into the sensory (afferent) and motor (efferent) divisions.
The connective tissue sheath that surrounds an individual nerve fiber (axon) is the ____________.
Endoneurium
Explanation: The endoneurium is the loose connective tissue that encloses individual nerve fibers and their myelin sheaths.
The __________ nerve is the only cranial nerve that travels to the thoracic and abdominal cavities.
Vagus
Explanation: The vagus nerve extends into the thoracic and abdominal cavities, unlike other cranial nerves which mainly serve the head and neck.
The sensory receptors that respond to light energy are called ____________.
Photoreceptors
Explanation: Photoreceptors respond to light energy and are primarily involved in vision.
The area of the skin served by a single spinal nerve root is called a ____________.
Dermatome
Explanation: A dermatome is an area of skin innervated by the sensory fibers of a single spinal nerve root.
Motor endings are PNS structures that activate effectors (muscle or glands) by releasing neurotransmitters.
True
False
True
Explanation: Motor endings are part of the peripheral nervous system (PNS) and they activate effectors such as muscles or glands by releasing neurotransmitters.
Innervation of skeletal muscle takes place at:
A) Ganglia
B) Synapses en passant
C) The neuromuscular junction
D) Diffusion junctions
C) The neuromuscular junction
Explanation: The neuromuscular junction is the specialized synapse between a motor neuron and a skeletal muscle fiber. It is the site where the motor neuron releases neurotransmitters, specifically acetylcholine, which bind to receptors on the muscle fiber’s membrane, leading to muscle contraction. This precise and efficient communication ensures the proper activation of skeletal muscles.
Which of the following is not a correct statement about reflexes and reflex arcs:
A) Reflex responses are very stereotyped and predictable.
B) Reflexes are nearly instantaneous responses of the nervous system that require a stimulus.
C) Reflexes are involuntary.
D) Reflex arcs typically only involve a few synapses.
E) Reflexes are found only in the autonomic nervous system.
F) All are true statements.
E) Reflexes are found only in the autonomic nervous system.
Explanation: This statement is incorrect because reflexes can be found in both the autonomic nervous system (involuntary control, such as heart rate and digestion) and the somatic nervous system (voluntary control, such as the knee-jerk reflex).
Which of the following best describes the order of a somatic reflex arc?
A) Somatic receptor –> efferent nerve fiber –> interneuron –> afferent nerve fiber –> skeletal muscle
B) Somatic receptor –> interneuron –> afferent nerve fiber –> efferent nerve fiber –> skeletal muscle
C) Somatic receptor –> afferent nerve fiber –> interneuron –> efferent nerve fiber –> smooth muscle
D) Somatic receptor –> afferent nerve fiber –> interneuron –> efferent nerve fiber –> skeletal muscle
D) Somatic receptor –> afferent nerve fiber –> interneuron –> efferent nerve fiber –> skeletal muscle
Explanation: In a somatic reflex arc, the process begins with a somatic receptor detecting a stimulus. This information is then transmitted via an afferent nerve fiber (sensory neuron) to the central nervous system, where it often connects to an interneuron. The interneuron processes the information and sends a response through an efferent nerve fiber (motor neuron) to the skeletal muscle, resulting in a reflexive action. This pathway ensures a rapid and automatic response to the stimulus.
Reflexes may be inborn (intrinsic) or learned (acquired).
True
False
True
Explanation: Reflexes can be inborn (intrinsic), such as the knee-jerk reflex, which are natural responses present at birth, or they can be learned (acquired), such as braking a car quickly in response to an obstacle, which are developed through experience and practice.
Reflex arcs may involve:
A) Only the brain
B) Only the spinal cord
C) Both the brain and the spinal cord
D) Neither the brain nor the spinal cord
C) Both the brain and the spinal cord
Explanation: Reflex arcs can involve processing in the spinal cord, the brain, or both, depending on the complexity of the reflex.
Which neurotransmitter is released at the neuromuscular junction to stimulate skeletal muscle contraction?
A) Dopamine
B) Serotonin
C) Acetylcholine
D) Norepinephrine
C) Acetylcholine
Explanation: Acetylcholine is the neurotransmitter that binds to receptors on the muscle fiber membrane, causing depolarization and muscle contraction.
Reflexes are found only in the autonomic nervous system.
True
False
False
Explanation: Reflexes can occur in both the autonomic nervous system (e.g., heart rate, digestion) and the somatic nervous system (e.g., knee-jerk reflex).
Reflex responses are very stereotyped and predictable.
True
False
True
Explanation: Reflexes occur in a predictable manner in response to specific stimuli, making them stereotyped and consistent.
The neurotransmitter released at the neuromuscular junction is __________.
Acetylcholine
Explanation: Acetylcholine is the chemical released by motor neurons to stimulate muscle contraction at the neuromuscular junction.
The type of reflex that involves only one synapse between the afferent and efferent neurons is called a __________ reflex.
Monosynaptic
Explanation: A monosynaptic reflex involves a single synapse, leading to a rapid response, such as the stretch reflex.
Which of the following is NOT a characteristic of reflexes?
A) Reflexes are involuntary.
B) Reflexes involve conscious thought.
C) Reflexes are quick.
D) Reflexes are stereotyped.
B) Reflexes involve conscious thought
Explanation: Reflexes occur without conscious thought; they are automatic responses to stimuli.
The primary neurotransmitter involved in activating skeletal muscles at the neuromuscular junction is:
A) Dopamine
B) Serotonin
C) Acetylcholine
D) Norepinephrine
C) Acetylcholine
Explanation: Acetylcholine is the neurotransmitter that binds to receptors on muscle fibers, leading to muscle contraction.
Which type of reflex arc involves an interneuron?
A) Monosynaptic reflex arc
B) Polysynaptic reflex arc
C) Both monosynaptic and polysynaptic reflex arcs
D) Neither monosynaptic nor polysynaptic reflex arcs
B) Polysynaptic reflex arc
Explanation: A polysynaptic reflex arc includes one or more interneurons between the afferent and efferent neurons, allowing for more complex responses.
In a reflex arc, the component that detects the stimulus is called the:
A) Effector
B) Receptor
C) Integrating center
D) Efferent neuron
B) Receptor
Explanation: The receptor is the structure that detects the stimulus and initiates the reflex arc.
Reflex arcs can involve either the spinal cord or the brain.
True
False
True
Explanation: Reflex arcs can be processed at different levels of the central nervous system, including the spinal cord and brain.
The autonomic nervous system controls skeletal muscles through reflex arcs.
True
False
False
Explanation: The autonomic nervous system controls involuntary functions such as heart rate and digestion, while the somatic nervous system controls skeletal muscles.
Reflexes can be categorized as either monosynaptic or polysynaptic.
True
False
True
Explanation: Reflexes are classified based on the number of synapses involved between the sensory input and motor output.
The response of a muscle to being stretched, which is a monosynaptic reflex, is known as the __________ reflex.
Stretch
Explanation: The stretch reflex involves a direct pathway from sensory to motor neuron, resulting in a quick response to muscle stretching.
The junction where a motor neuron communicates with a muscle fiber is called the __________.
Neuromuscular junction
Explanation: The neuromuscular junction is the site where the motor neuron releases neurotransmitters to stimulate muscle contraction.
Reflexes that are learned through practice or repetition are referred to as __________ reflexes.
Acquired
Explanation: Acquired reflexes develop through experience, such as driving skills or playing a musical instrument.
