PERIPHERAL NERVOUS SYSTEM Flashcards by Syeda Mahira Masood

The PNS includes all neural structures outside the brain and spinal cord. These structures are

sensory receptors, afferent and efferent nerves and their associated ganglia, and motor endings.

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are specialized to respond to changes in their environment, which are called stimuli.

Sensory receptors

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respond to mechanical force such as touch, pressure (including blood pressure), vibration, and stretch.

Mechanoreceptors

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respond to temperature changes.

Thermoreceptors

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respond to potentially damaging stimuli that result in pain.

Nociceptors

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respond to chemicals in solution

Chemoreceptors

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such as those of the retina of the eye, respond to light.

Photoreceptors,

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are sensitive to stimuli arising outside the body

Exteroceptors

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also called visceroceptors, respond to stimuli within the body

Interoceptors

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respond to internal stimuli. However, their location is much more restricted.

Proprioceptors

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They are found throughout the body and monitor most types of general sensory information.

general senses

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Receptors that are housed in complex sense organs.

special senses

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general sensory receptors are nerve endings that are

either nonencapsulated (free) or encapsulated.

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nonencapsulated (free) nerve endings of sensory neurons are particularly abundant

epithelia and connective tissues.

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Free nerve endings respond chiefly to

painful stimuli and temperature

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Nerve endings that respond to cold (10–40°C, or 50–104°F) are located in the

superficial dermis.

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Those responding to heat (32–48°C, or 90–120°F) are deeper in

the dermis

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A key player in detecting painful stimuli is a plasma membrane protein called the

vanilloid receptor.

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Another sensation mediated by free nerve endings is Located in the dermis

itch

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which lie at the junction of the epidermis and dermis, function as light pressure receptors.

Epithelial tactile complexes

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free nerve endings that wrap basketlike around hair follicles, are light touch receptors that detect bending of hairs

Hair follicle receptors

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which nerve endings consist of one or more fiber terminals of sensory neurons enclosed in a connective tissue capsule.

encapsulated nerve endings

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what is also called as Meissner’s corpuscles and are small receptors in which a few spiraling sensory terminals are surrounded by Schwann cells and then by a thin egg-shaped connective tissue capsule.

tactile corpuscles

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what is also called Pacinian corpuscles, are scattered deep in the dermis, and in subcutaneous tissue underlying the skin. Although they are mechanoreceptors stimulated by deep pressure, they respond only when the pressure is first applied, and thus are best suited to monitoring vibration (

lamellar corpuscles

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what is or Ruffini endings, which lie in the dermis, subcutaneous tissue, and joint capsules, contain a spray of receptor endings enclosed by a flattened capsule. They bear a striking resemblance to tendon organ

bulbous corpuscles

what are fusiform (spindle-shaped) proprioceptors found throughout the perimysium that wraps individual fascicles of skeletal muscle.

muscle spindles

Each muscle spindle consists of a bundle of modified skeletal muscle fibers,

called intrafusal fibers

what are proprioceptors located in tendons, close to the junction between the skeletal muscle and the tendon.

tendon organs

what are proprioceptors that monitor stretch in the articular capsules that enclose synovial joints.

Joint kinesthetic receptors

the part of the sensory system serving the body wall and limbs

somatosensory system

what are Three main levels of neural integration operate in the somatosensory

STEP 1 Receptor level: sensory receptors STEP 2 Circuit level: processing in ascending pathways STEP 3 Perceptual level: processing in cortical sensory areas

are fast adapting, often giving bursts of impulses at the beginning and the end of the stimulus.

phasic receptors

provide a sustained response with little or no adaptation.

tonic receptors

The stimulus energy must be converted into the energy of a graded potential, a process called

transduction

what is the ability to detect that a stimulus has occurred.

Perceptual detection

what is the ability to detect how intense the stimulus is.

Magnitude estimation

what allows us to identify the site or pattern of stimulation.

spatial discrimination

what is the mechanism by which a neuron or circuit is tuned to one feature, or property, of a stimulus in preference to others.

feature abstraction

what is the ability to differentiate the submodalities of a particular sensation

Quality discrimination

what is the ability to take in the scene around us and recognize a familiar pattern, an unfamiliar one, or one that has special significance for us.

pattern recognition

which pain is in which pain stimuli arising in one part of the body are perceived as coming from another part.

referred pain

what is a cordlike organ that is part of the peripheral nervous system.

nerve

Each axon (or nerve fiber) is surrounded by , a delicate layer of loose connective tissue that also encloses the fiber’s associated Schwann cells.which is called ?

endoneurium

A coarser connective tissue wrapping, the perineurium, binds groups of axons into bundles called

fascicles

A tough fibrous sheath, that encloses all the fascicles to form the nerve.

epineurium

what contain both sensory and motor fibers and transmit impulses both to and from the central nervous system.

mixed nerves

carry impulses only toward the CNS.

Sensory (afferent) nerves

carry impulses only away from the CNS.

Motor (efferent) nerves

what are the tiny sensory nerves (filaments) of smell, which run from the nasal mucosa to synapse with the olfactory bulbs.

olfactory

this sensory nerve of vision develops as an outgrowth of the brain, it is really a brain tract.

Optic

This nerve supplies four of the six extrinsic muscles that move the eyeball in the orbit.

oculomotor

it innervates an extrinsic eye muscle that loops through a pulley-shaped ligament in the orbit.

trochlear

Three branches spring from this, the largest cranial nerve. It supplies sensory fibers to the face and motor fibers to the chewing muscles.

trigeminal nerve

This nerve controls the extrinsic eye muscle that abducts the eyeball

abducens

A large nerve that innervates muscles of facial expression (among other things).

facial

This mostly sensory nerve for hearing and balance was formerly called the auditory nerve.

Vestibulocochlear.

“tongue and pharynx,” the structures that this nerve helps to innervate.

glossopharyngeal

it is the only cranial nerve to extend beyond the head and neck to the thorax and abdomen.

vagus

Considered an accessory part of the vagus nerve, this nerve was formerly called the spinal accessory nerve.

accessory

This nerve runs inferior to the tongue and innervates the tongue muscles.

hypoglossal nerve

how many pairs of spinal and cranial nerves are present ?

31 pairs of spinal 12- cranial nerves

distribute the spinal nerves

8 pairs of cervical nerves (C1-C8) 12 pairs of thoracic nerves (T1-T12) 5 pairs of lumbar nerves (L1-L5) 5 pairs of sacral nerves (S1-S5) 1 pair of tiny coccygeal nerves (Co1)

What is the discrepancy of cranial nerves

The first seven pairs exit the vertebral canal superior to the vertebrae for which they are named, but C8 emerges inferior to the seventh cervical vertebra

what contain motor (efferent) fibers that arise from ventral horn motor neurons and extend to and innervate the skeletal muscles.

ventral Roots

contain sensory (afferent) fibers that arise from sensory neurons in the dorsal root ganglia and conduct impulses from peripheral receptors to the spinal cord.

dorsal roots

which plexus receives fibers from C3, C4 and C5 . The phrenic nerve runs inferiorly through the thorax and supplies both motor and sensory fibers to the diaphragm (phren = diaphragm), which is the chief muscle causing breathing movements.

phrenic nerve

The brachial plexus ends in the axilla, where its three cords wind along the axillary artery and give rise to the main nerves of the upper limb

the axillary, musculocutaneous, median, ulnar, and radial nerves.

It innervates the deltoid and teres minor muscles and the skin and joint capsule of the shoulder.

axillary nerve

the major end branch of the lateral cord, courses inferiorly in the anterior arm, supplying motor fibers to the biceps brachii, brachialis, and coracobrachialis muscles.

musculocutaneous nerve

descends through the arm to the anterior forearm, where it gives off branches to the skin and to most flexor muscles

median nerve

branches off the medial cord of the plexus. It descends along the medial aspect of the arm toward the elbow, swings behind the medial epicondyle, and then follows the ulna along the medial forearm.

ulnar nerve

the largest branch of the brachial plexus, is a continuation of the posterior cord. This nerve wraps around the humerus (in the radial groove), and then runs anteriorly around the lateral epicondyle at the elbow.

radial nerve

The lumbar plexus arises from spinal nerves

L1-L5 and lies within psoas major muscle

the largest terminal nerve of this plexus, runs deep to the inguinal ligament to enter the thigh and then divides into several large branches.

femoral nerve

The sacral plexus arises from spinal nerves

L4-S4 and lies immediately caudal to the lumbar plexus

what is The largest branch of the sacral plexus is the the thickest and longest nerve in the body.

sciatic nerve

The sciatic nerve is actually two nerves, name them

tibial and common fibular

Circuits that control locomotion and other specific and oft-repeated motor activities are called

central pattern generators (CPGs).

Two other systems of brain neurons, located in the cerebellum and basal nuclei

regulate motor activity.

which reflex is a rapid, predictable motor response to a stimulus. It is unlearned, unpremeditated, and involuntary, and is built into our neural anatomy.

inborn (intrinsic) reflex

learned (acquired ) reflex

results from practice or repetition.

Two types of information about the current state of a muscle are required. The nervous system needs to know:

The length of the muscle. The amount of tension

what are the endings of large axons that wrap around the spindle center. They are stimulated by both the rate and degree of stretch.

Anulospiral endings

are formed by smaller axons that supply the spindle ends. They are stimulated only by degree of stretch.

Flower spray endings

which reflex causes automatic withdrawal of the threatened body part from the stimulus

flexor/ withdrawal reflex

Each muscle spindle consists of three to ten modified skeletal muscle fibers called

intrafusal muscle fibers

motor neurons in spinal cord circuits supplying the contracting muscle are inhibited and antagonist muscles are activated, a phenomenon

called reciprocal activation.

Which of the following best describes the peripheral nervous system (PNS)?

It connects the central nervous system to limbs and organs.

The two main divisions of the peripheral nervous system are:

Somatic and autonomic nervous systems

The somatic nervous system is responsible for:

Voluntary muscle movements

Which neurotransmitter is commonly released by the sympathetic nervous system to prepare the body for 'fight or flight'?

Norepinephrine

The sympathetic and parasympathetic nervous systems are branches of which of the following?

Autonomic nervous system

In the autonomic nervous system, the 'rest and digest' response is primarily controlled by:

Parasympathetic nervous system

Which nerve is the longest in the body and is part of the PNS?

Sciatic nerve

The cranial nerves are part of the peripheral nervous system and serve primarily which function?

Connecting the brain to various head and neck structures

The main function of sensory (afferent) nerves in the PNS is to:

Relay information from the body to the central nervous system

The vagus nerve is significant because it:

Extends into the chest and abdomen, controlling various organs