Podcast
Questions and Answers
What is the primary distinction between nervous system structures within and outside the brain and spinal cord?
What is the primary distinction between nervous system structures within and outside the brain and spinal cord?
- Structures inside are part of the peripheral nervous system.
- Structures outside are part of the central nervous system.
- Structures outside are part of the peripheral nervous system. (correct)
- There is no structural difference, only functional.
Which statement accurately describes the composition of white matter in the peripheral nervous system?
Which statement accurately describes the composition of white matter in the peripheral nervous system?
- White matter contains a mix of both axons and dendrites.
- White matter consists of ganglia, housing clusters of cell bodies.
- White matter is primarily made up of Schwann cells.
- White matter is composed of nerves, which are bundles of axons. (correct)
How many pairs of spinal nerves directly connect to the central nervous system?
How many pairs of spinal nerves directly connect to the central nervous system?
- 12 pairs
- 43 pairs
- 31 pairs (correct)
- 24 pairs
What is the fundamental role of the motor components within the peripheral nervous system?
What is the fundamental role of the motor components within the peripheral nervous system?
What is the primary function of sensory neurons (afferent) in the peripheral nervous system?
What is the primary function of sensory neurons (afferent) in the peripheral nervous system?
What role do Schwann cells play in the peripheral nervous system (PNS)?
What role do Schwann cells play in the peripheral nervous system (PNS)?
The diameter of an axon is directly related to its conduction velocity. Which of the following statements accurately describes this relationship?
The diameter of an axon is directly related to its conduction velocity. Which of the following statements accurately describes this relationship?
What is the term for a connective tissue layer that immediately surrounds individual axons in a peripheral nerve?
What is the term for a connective tissue layer that immediately surrounds individual axons in a peripheral nerve?
In the hierarchical structure of a peripheral nerve, what do fascicles consist of?
In the hierarchical structure of a peripheral nerve, what do fascicles consist of?
Which connective tissue layer forms the outermost covering of a peripheral nerve?
Which connective tissue layer forms the outermost covering of a peripheral nerve?
What is the functional role of the somatic sensory division of the peripheral nervous system (PNS)?
What is the functional role of the somatic sensory division of the peripheral nervous system (PNS)?
Which of the following is primarily regulated by the visceral sensory receptors?
Which of the following is primarily regulated by the visceral sensory receptors?
What type of information is transmitted by proprioceptors?
What type of information is transmitted by proprioceptors?
The synapse between the axon terminal of a lower motor neuron and a skeletal muscle fiber is called what?
The synapse between the axon terminal of a lower motor neuron and a skeletal muscle fiber is called what?
Where are the cell bodies of somatic motor neurons located?
Where are the cell bodies of somatic motor neurons located?
Which division of the autonomic nervous system is responsible for 'fight or flight' responses?
Which division of the autonomic nervous system is responsible for 'fight or flight' responses?
Which of the following best characterizes the role of the parasympathetic nervous system?
Which of the following best characterizes the role of the parasympathetic nervous system?
In a spinal nerve, what type of information is carried via the dorsal root?
In a spinal nerve, what type of information is carried via the dorsal root?
What type of information is transmitted via the ventral root of a spinal nerve?
What type of information is transmitted via the ventral root of a spinal nerve?
Spinal nerves are formed by a merging of what?
Spinal nerves are formed by a merging of what?
How many spinal nerve pairs are responsible for mapping dermatomes on the body?
How many spinal nerve pairs are responsible for mapping dermatomes on the body?
What is a plexus in the context of the peripheral nervous system?
What is a plexus in the context of the peripheral nervous system?
Which nerve plexus innervates the lower abdominal, genital areas and thighs?
Which nerve plexus innervates the lower abdominal, genital areas and thighs?
Damage to the brachial plexus is most likely to result in a loss of what?
Damage to the brachial plexus is most likely to result in a loss of what?
How many pairs of cranial nerves directly interact with the brain?
How many pairs of cranial nerves directly interact with the brain?
Which cranial nerve does NOT carry parasympathetic (autonomic visceral motor) information?
Which cranial nerve does NOT carry parasympathetic (autonomic visceral motor) information?
What is the primary function of cranial nerve I (Olfactory)?
What is the primary function of cranial nerve I (Olfactory)?
Which cranial nerve is responsible for transmitting visual information to the brain?
Which cranial nerve is responsible for transmitting visual information to the brain?
Which cranial nerves primarily control the movement of the eye?
Which cranial nerves primarily control the movement of the eye?
Which cranial nerve is the major somatosensory nerve for the face?
Which cranial nerve is the major somatosensory nerve for the face?
Flashcards
Peripheral Nervous System
Peripheral Nervous System
Structures outside the brain and spinal cord
Nerves (PNS)
Nerves (PNS)
Bundle of axons
Ganglia
Ganglia
Cluster of cell bodies
Sensory Information
Sensory Information
Information from receptors to the CNS
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Motor Commands
Motor Commands
Commands from the CNS to muscles or glands
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Sensory Neurons
Sensory Neurons
Neurons that carry sensory information
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Motor Neurons
Motor Neurons
Neurons that carry motor commands
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Schwann Cells
Schwann Cells
Glia cells in PNS
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Peripheral Nerves
Peripheral Nerves
Axons grouped together
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Fascicles
Fascicles
Bundles of axons within a nerve
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Endoneurium
Endoneurium
Connective tissue around individual axons
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Perineurium
Perineurium
Connective tissue around fascicles
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Epineurium
Epineurium
Connective tissue around the entire nerve
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Afferent Division
Afferent Division
The sensory division of the PNS
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Somatic Efferent Division
Somatic Efferent Division
Motor division of the PNS controlling skeletal muscle
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Autonomic Efferent Division
Autonomic Efferent Division
Motor division of the PNS regulating automatic functions
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Somatic Sensory
Somatic Sensory
From skin, skeletal muscle, joints
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Proprioceptors
Proprioceptors
From muscles, tendons, joints
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Interoceptors
Interoceptors
Visceral sensory receptors
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Somatic Motor
Somatic Motor
Skeletal muscle motor neurons
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Neuromuscular Junction
Neuromuscular Junction
Synapse between motor neuron and skeletal muscle
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Visceral Motor
Visceral Motor
Autonomic motor control
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Sympathetic Division
Sympathetic Division
Fight or flight
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Parasympathetic Division
Parasympathetic Division
Rest and digest
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Spinal Nerve
Spinal Nerve
A nerve interacting with the spinal cord
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Plexus
Plexus
network of intersecting nerves
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Cranial Nerve
Cranial Nerve
Interact directly with the brain.
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Olfactory Nerve (CN I)
Olfactory Nerve (CN I)
Responsible for the sense of smell.
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Optic Nerve (CN II)
Optic Nerve (CN II)
Carries visual information
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Oculomotor Nerve (CN III)
Oculomotor Nerve (CN III)
Innervates muscles for eye movement, pupil constriction
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The Peripheral Nervous System
- The peripheral nervous system consist of nervous system structures outside of the brain and spinal cord
- Its structure contains white and grey matter
- White matter consists of nerves (bundles of axons)
- Grey matter consists of ganglia (clusters of cell bodies)
- The peripheral nervous system is connected to the CNS via 31 pairs of spinal nerves and 12 pairs of cranial nerves
- The main functions are to deliver sensory information from receptors in the periphery to the CNS, and deliver motor commands from the CNS to muscles and glands (both involuntary and voluntary)
Cells of the PNS
- Neurons are either sensory (afferent) or motor (efferent)
- Glia primarily consist of Schwann cells, and are responsible for myelinating and non-myelinating
Structure of a Peripheral Nerve
- Axons group together and travel in peripheral nerves
- Each peripheral nerve is made of several bundles of axons called fascicles
- Three levels of connective tissue wrap around the nerve bundle hierarchy
- Endoneurium wraps around axons
- Perineurium wraps around fascicles
- Epineurium wraps around the entire nerve
- In a transverse section of a peripheral nerve, myelin stains blue/turquoise and connective tissue stains pink/purple
Organization of the PNS
- The PNS separates into sensory and motor components
- Sensory (afferent) neurons categories
- Visceral relates to organs
- Special category includes cranial nerves
- Somatic includes everything else
- Motor (efferent) neurons categories:
- Somatic relates to skeletal muscle
- Visceral (autonomic) nerves relate to organs and glands
The Peripheral Sensory System
- Somatic sensory components include information from skin, skeletal muscle, tendons, joints, connective tissue and meninges
- Exteroceptors relate to the skin, and include sensations like touch, pressure, thermal and pain
- Proprioceptors relate to muscles, tendons, and joints, and provide information about the body's location in space
- Interoceptors (visceral sensory receptors) relate to thermal, pain, changes in blood composition and pressure in internal organs in the thoracic and abdominal cavities
- Primary sensory neurons have their cell body in ganglia and deliver information from the receptors into the CNS
Peripheral Motor System (Somatic)
- Consists of somatic motor neurons that control skeletal muscle (lower motor neurons)
- Cell bodies are located in the CNS
- Motor axons exit the spinal cord via the ventral roots, spinal nerves, and peripheral nerves
- Axons can also exit the brainstem via cranial nerves and travel to the muscle
- Somatic motor system allows for voluntary movements and somatic reflexes
- The synapse between the axon terminal of the lower motor neuron and the skeletal muscle refers to the neuromuscular junction
Peripheral Motor System (Visceral)
- Visceral motor control equates to the autonomic nervous system
- It regulates cardiovascular, respiratory, digestive, urinary, reproductive functions, and internal environment composition
- It is mostly involuntary and subconscious, and controls smooth/cardiac muscles and glands
- It has 2 divisions, sympathetic and parasympathetic
- CNS → effectors = 2 neurons
- The first neuron is located in the spinal cord and brainstem, with its axon exiting the CNS via selected spinal nerves and cranial nerves
- The second neuron is found entirely in the PNS, with the cell body in autonomic ganglia
- CNS → effectors = 2 neurons
Spinal Nerves
- A spinal nerve directly interacts with the spinal cord
- Spinal nerves deliver sensory and motor information from a similar area - Sensory information travels via the dorsal root (cell bodies located in the dorsal root ganglion) - Motor information travels via the ventral root (cell bodies in the ventral horn or autonomic ganglion)
- Nerve branches form dorsal (posterior) and ventral (anterior) rami, carrying both sensory and motor information
Segmental Organization of Spinal Cord and Nerves
- 31 spinal nerve pairs is mapped to approximately 31 dermatomes
Spinal Nerve Plexuses
- Several ventral rami of spinal nerves innervating the neck, upper, and lower limbs reorganize to form interwoven networks referred to as plexuses
- Cervical plexus - Provides motor innervation to some muscles of the neck and diaphragm - Provides sensory innervation to the head, neck, and chest
- Brachial plexus
- Provides sensory and motor information from the arm and hand
- Damage can result in sensory loss and upper limb paralysis
- Lumbar plexus innervates the muscles on the lower abdominal, genital areas, and thighs
- Sacral plexus innervates the skin and muscles of the thigh, lower leg, and foot
- overlap can occur at T4, so often grouped as lumbosacral plexus
Plexus Organization
- The ventral rami combine to form superior, middle, and inferior trunks → anterior and posterior divisions (innervate ventral and dorsal upper limbs) → converge to form posterior, medial, and lateral cords → splitting into five terminal branches: the axillary, median, musculocutaneous, radial, and ulnar nerves
Cranial Nerves
- The 12 pairs of nerves that directly interact with the brain
- These nerves carry sensory and motor information from head and neck structures (with the exception of CNX)
- These nerves carry special sensory information such as taste, smell, vision, hearing and balance
- Cranial nerves project to
- Cortex- I
- Diencephalon-II
- Midbrain-III and IV
- Pons- V
- Pons-Medulla border- VI, VII and VIII
- Medulla- IX, X, XI and XII
- Nerves III, VII, IX and X are parasympathetic (autonomic visceral motor control)
Cranial Nerve Mnemonic
- I - Olfactory "Only"
- II - Optic "One"
- III - Oculomotor "Of"
- IV - Trochlear "The"
- V - Trigeminal "Two"
- VI - Abducens "Athletes"
- VII - Facial "Felt"
- VIII - Vestibulocochlear "Very"
- IX - Glossopharyngeal "Good"
- X - Vagus "Victorious"
- XI - Accessory "And"
- XII - Hypoglossal "Healthy"
Cranial Nerves – Type of Info
- I - Olfactory "Some" - Sensory
- II - Optic "Say" - Sensory
- III - Oculomotor "Marry" - Motor
- IV - Trochlear "Money" - Motor
- V - Trigeminal "But" - Both
- VI - Abducens "My" - Motor
- VII - Facial "Brother" - Both
- VIII - Vestibulocochlear "Says" - Sensory
- IX - Glossopharyngeal "Big" - Both
- X - Vagus "Brains" - Both
- XI - Accessory "Matter" - Motor
- XII - Hypoglossal "More" - Motor
CN I- Olfactory
- A special sensory nerve involved in the sense of smell
- Receptors are located in the olfactory epithelium in the nasal cavity
- 1° neurons (detect stimuli) located in the olfactory bulb above the cribriform plate with axons traveling through the bone
- 2° neurons (relay stimuli) form the olfactory tract into the cerebrum
CN II- Optic Nerve
- Main function is special sensory for vision
- This nerve carry visual information from the retina of the eye
- Optic nerves merge in the optic chiasm where fibers cross the midline before entering the CNS via the optic tract
- Nerve destination is the diencephalon (thalamus, LGN)
CN III, IV, VI - Muscles of the Eye
- Motor information included
- One of 4 extrinsic eye muscles moves eyeball up, medially, down and rotation, as well as eyelid closure
- Visceral motor control includes pupil constriction and lens accommodation
- Trochlear is an extrinsic eye muscle
- Abducens controls movement of the extrinsic eye muscle-lateral
CN V- Trigeminal
- Function as mixed sensory and motor nreve
- It is major somatosensory nerve for the face, top of scalp, nasal cavity and oral cavity
- Nerve is attached laterally in the pons and then branches into three divisions- ophthalmic (top), maxillary (middle) and mandibular (lower)
- Trigeminal ganglion contains the cell bodies of the primary sensory neurons (equivalent to the dorsal root ganglia)
- Axons of LMN for muscles of mastication travel in the mandibular branch (equivalent to the ventral root) from cell bodies in the brainstem (pons)
CN VII- Facial
- Emerges from the medulla-pons border
- Functions as a mixed sensory and motor nerve
- Somatic motor innervates the muscles of facial expressions
- Visceral carries motor signal for innervation of saliva and tear glands
- Special sensory component taste sensations from the anterior two thirds of the tongue
CN VIII - Vestibulocochlear
- Only carries sensory information related to hearing and balance
- Enters the brainstem at the medulla-pons border
- Contains two branches originating in the inner ear
- Vestibular branch innervates the vestibular apparatus and carries information regarding head movements to vestibular nuclei
- Cochlear branch innervates the cochlea and carries audio information to cochlear nuclei
CN IX- Glossopharyngeal
- Carries both sensory and motor information
- Emerges from the medulla lateral to the olives
- Somatosensory sensations from the back of the oral cavity and upper pharynx
- Visceral sensory sensation from chemoreceptors (CO2 and pH) and baroreceptor (blood pressure) in the carotid body and sinus
- Special taste sensations from the back third of the tongue
- Visceral motor function, and is associated with parotid gland (saliva)
CN X- Vagus
- Functions as a mixed motor and sensory nerve
- CN X nerve emerge from the brainstem close to each other on the lateral side of the olives in the medulla, and is the only CN that is distributed below the head and neck - Major visceral functions include both motor and sensory innervation, the thoracic and abdominal regions - Most of the Vagus fibres carry sensory information from visceral tissue in the thoracic and abdominal regions, as well as chemoreceptors and stretch receptors in the aortic arch, letting the brain know about the internal environment of the body General and somatosensory component is associated from the pharynx, larynx and regions of the meninges - Motor signals regulate airways, digestive and cardiovascular functions. - Innervates the muscles of the pharynx and larynx, soft palate and epiglottis
CN XI- Spinal Accessory
- A motor nerve that innervates two muscles: - The trapezius, which tilts the head back and to the side and elevates the shoulders - Thee sternocleidomastoid, and rotates the head and jaw to the opposite side The cell bodies of the axons in the nerve are found in the ventral horn of the cervical spine, and exit through ventral roots. They travel up in the subarachnoid space, through the foramen magnum and then out through the cranium to travel to muscles
CN XII- Hypoglossal
- The rootlets of the hypoglossal emerge between the pyramids and the olives of the medulla
- All fibers are somatic motor, innervating muscles of the tongue (all but one, which is innervated by the vagus)
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