Study notes Flashcards
The peripheral nervous system gathers input from?
sensory receptors
The PNS sends motor output where?
to effectors
Provide links from and to the world outside our bodies
Peripheral nervous system (PNS)
What does the PNS include?
All neural structures outside the brain and spinal cord
What are the neural structures outside the brain and spinal cord the PNS include?
sensory receptors, peripheral nerves and associated ganglia, efferent motor endings
How are sensory receptors activated?
by changes in the internal and external environment
What are environmental changes called?
stimuli
Awareness of stimulus
Sensations
Interpretation of the meaning of the stimulus
Perception
Where does sensation and perception occur?
In the brain
What are 3 ways to classify sensory receptors?
type of stimulus they detect, by their body location, and by their structural complexity
How are stimulus type classified?
named according to the activating stimulus
Respond to mechanical force such as touch, pressure (bp), vibration, and stretch
Mechanoreceptors
Respond to temperature changes
Thermoreceptors
Of the retina of the eye, respond to light
Photoreceptorsthose
Respond to chemicals in solution (molecules smelled or tasted, or changes in blood or interstitial fluid chemistry)
Chemoreceptors
respond to potentially damaging stimuli that result in pain
Nociceptors
Receptors can be grouped into three receptor classes according to what?
location and location of activating stimulation
What are the 3 receptor classes according to location?
Exteroceptors, interoceptors, and proprioceptors
Exteroceptors
sensitive to stimuli arising outside of the body such as touch, pressure, pain, and temperature in the skin and most receptors of special senses (vision, hearing, equilibrium, smell, and taste)
Interoceptors
visceroceptors; respond to stimuli w/i the body such as internal visceral and blood vessels
What stimuli do interoceptors monitor?
chemical changes, tissue stretch, temperature
Interoceptors activity causes us to feel what?
pain, discomfort, hunger, thirst
Proprioceptors
respond to internal stimuli
T or F. Proprioceptors have a more restricted location
True
Where do proprioceptors occur?
skeletal muscles, tendons, joints, ligaments, connective tissue coverings of bones and muscles
What do proprioceptors advise our brain about?
body movements by monitoring how much the organs are stretched
The majority of sensory receptors belong to what?
general senses
What is considered our special senses?
vision, hearing, equilibrium, smell, taste
Where are receptors for the special senses housed?
complex sense organs
How are receptors classified structurally?
simple and complex receptors
General sensory receptors are involved in ?
tactile sensation, temperature monitoring, pain, muscle sense provided by proprioceptors
What are general sensory receptors anatomically?
nerve endings that are nonencapsulated (free) or encapsulated nerve endings
What type of nerve endings are present nearly everywhere in the body?
Nonencapsulated (free or naked) nerve endings
Nonencapsulated (free or naked) nerve endings are particularly abundant where?
epithelial and connective tissue
Nonencapsulated (free or naked) nerve endings respond chiefly to what?
temperature and painful stimuli; some respond to tissue movements caused by pressure
What are 2 examples of nonencapsulated nerve endings?
Tactile (Merkel) discs and hair follicle receptors
What are Tactile (Merkel) discs function?
function as light touch
What are Tactile (Merkel) discs?
Enlarged, disc-shaped epidermal cells
Free nerve endings that wrap basket-like around hair follicles
Hair follicle receptors
What do hair follicles detect?
bending of hairs (light touch receptors)
What do encapsulated nerve endings consist of?
One or more fiber terminals of sensory neurons enclosed in a connective tissue capsule
What is another name for Tactile corpuscles?
Meissner’s carpuscles
Where are tactile corpuscles found?
beneath epidermis in dermal papillae
Where are tactile corpuscles numerous?
sensitive and hairless skin areas such as nipples, fingertips, soles of feet
Tactile corpuscles are receptors for what?
discriminative touch
What is another name for lamellar corpuscles?
Pascinian corpuscles
Where are lammelar (Pascinian) corpuscles found?
scattered deep in dermis and in subcutaneous tissue underlying the skin
What are lammelar (Pascinian) corpuscles stimulated by?
deep pressure
When does lammelar (Pascinian) corpuscles respond?
only when the pressure is first applied
What do lammelar (Pascinian) corpuscles monitor?
Vibration
What are the largest corpuscular receptors?
lammelar (Pascinian) corpuscles
Bulbous corpuscles are also known as?
Ruffini endings
Where do bulbous corpuscles/rufinni endings lie?
in the dermis, subcutaneous tissue, and joint capsules
What do bulbous corpuscles/rufinni endings respond to?
deep and continuous pressure
What do bulbous corpuscles/rufinni endings detect?
when a muscle is stretched and initiate a reflex that resists the stretch
Proprioceptors located in tendons, close to skeletal muscle insertion
(Golgi) tendon organs
What stimulate (Golgi) tendon organs?
associated muscle contract and stretches the tendon
What happens when the (Golgi) tendon organs are activated?
contracting muscle is inhibited, causing it to relax
Proprioceptors monitoring stretch in the articular capsules that enclose synovial joints are?
joint kinesthetic receptors
What are the 4 joint kinesthetic receptor types?
bulbous corpuscles/rufinni, lammelar (Pascinian) corpuscles, free nerve endings, receptors resembling (Golgi) tendon organs
Joint kinesthetic receptor types provide information on what?
joint position and motion
Cordlike organ that is a part of the PNS
nerve
Each nerve axon is surrounded by?
endoneurium
An axon is also referred to as?
axon
Delicate layer of loose connective tissue that also encloses the fiber’s associated Schwann cells, myelin sheath, neurilemma
endoneurium
Coarser connective tissue wrapping that binds fascicles
perineurium
Groups of axons (fibers) into bundles
fascicles
Tough fibrous sheath that encloses all the fascicles to form the nerve
epineurium
The PNS is divided into what divisions?
sensory (afferent) and motor (efferent)
Nerves containing both sensory and motor fibers and transmitting impulses both to and from the CNS are
Mixed nerves
Nerves carrying impulses only toward the CNS
sensory (afferent) nerves
Nerves carrying impulses away from the CNS
motor (efferent) nerves
How are nerve fibers classified?
according to the region they innervate (somatic afferent, somatic efferent, visceral afferent, and visceral efferent)
How many pairs of cranial nerves are there?
12
Nerves of smell
Olfactory nerve
Nerve of vision; outgrowth of the brain
optic nerve
Mean eye mover; supplies 4 of 6 extrinsic muscles that move the eyebal in orbit
Oculomotor nerve
Innervates an extrinsic eye muscles that loops through pulley shaped ligament in the orbit
Trochlear nerve
Three branches, largest of the cranial nerves; sensory fibers to the face and motor fibers to the chewing muscles
Trigeminal nerve
Controls the extrinsic eye muscles that abducts the eyeball (turns it laterally)
Abducens nerve
Innervates muscles of facial expressions
Facial nerve
Sensory nerve for hearing and balance, formerly auditory nerve
Vestibulocochlear nerve
Means tongue and pharynx and helps innervate these structures
Glossopharyngeal nerve
Only cranial nerve to extend to the abdomen
Vagus nerve
Accessory part of the vagus nerve; formerly called the spinal accessory nerve
Accessory nerve
Runs inferior to the tongue and innervates some tongue moving muscles
Hypoglossal nerve
What is the acronym to remember the order of cranial nerves?
On occasion, out trusty truck acts funny-very good vehicle any how
How many pairs of spinal nerves
31
Spinal nerves supply all parts of the body except what?
head and some areas of the neck
How many pairs of cervical spinal nerves are there?
8 pair (C1-C8)
How many pairs of thoracic nerves?
12 (T1-T12)
How many pairs of lumber nerves?
5 (L1-L5)
How many pairs of sacral nerves?
5 (S1-S5)
How many pair of coccygeal nerves?
1 (C0)
Each spinal nerve connects to the spinal cord by?
dorsal root and a ventral root
Contains motor (efferent) fibers that extend to and innervate the skeletal muscles
Ventral roots
Contains sensory (afferent) fibers
Dorsal roots
Conduct impulses from peripheral receptors to the spinal cord
spinal nerves
____ and ____ fibers mingle together in a spinal nerve, containing both ____ and ____ fibers
Motor, sensory
efferent, afferent
The most important nerve from the cervical plexus
phrenic nerve
Where do the phrenic nerves receive fibers from?
C3, C4, C5
Supplies motor and sensory fibers to the diaphragm
phrenic nerve
Chief muscle causing breathing movements
diaphragm
Gives rise to virtually all the nerves that innervate the upper limbs
brachial plexus
From medial to lateral, what are the four major groups of branches in the brachial plexus?
ventral rami trunks divisions cords Really tired? Drink coffee acronym
Five ____ (ventral ram C5-T1) unite to form ___, ___, and ____ trunks, each dividing almost immediately into and ____ and _____.
roots
upper, middle, and lower
anterior and posterior
What happens all along the brachial plexus?
small nerves branch off
The small nerves that branch off supply what part of the brachial plexus?
muscles and skin of the shoulder and superior thorax
The brachial plexus ends where and gives rise to what?
axilla, main nerves of the upper limb
What are the important branches of the brachial plexus
axillary, musculocutaneous, median, ulnar, radial nerves
What area does the lumbosacral plexus serve?
mainly lower limb but sends some branches to the abdomen, pelvis, and buttock
Lumbar plexus spinal nerves L1-L4 innervates parts of the what?
abdominal wall musles and the psoas muscle
The sacral plexus arises from?
spinal nerves L4-S4
The branches of the sacral plexus serves what area?
half serve the buttock and lower limb; the other innervate pelvic structures and the perineum
What is the largest branch of the sacral plexus?
sciatic nerve
The thickest and longest nerve in the body
sciatic nerve
What does the sciatic nerve supply?
entire lower limb except the anteromedial thigh
Enables rapid and predictable responses
reflex arc
Rapid, predictable motor response to a stimulus
inborn (intrinsic) reflex
It’s unlearned, unpremeditated, involuntary, and built into our neural anatomy
inborn (intrinsic) reflex
T or F We are aware of the final response of a basic reflex activity
T
T or F Reflex activities go on without any awarenes on our part
T
What kind of reflex results from practice or repetition?
learned (acquired) reflex
What are the five essential components of the reflex arc?
receptor, sensory neuron, integration center, motor neuron, and effector
What is the receptor of the reflex arc?
site of stimulus action
Transmits afferent impulses to the CNS in the reflex arc
sensory center
May be a single synapse between sensory neurons and a motor neuron or more complex reflex arcs involving multiple synapses with chains of interneurons; always within the CNS
Integration center
May be a single synapse between sensory neurons and a motor neuron
monosynaptic reflex
more complex reflex arcs involving multiple synapses with chains of interneurons
polysynaptic reflex
Conducts efferent impulses from the integration center to an effector organ
motor neuron
Muscle fiber or gland cell that responds to the efferent impulses (by contracting or secreting)
effector
Reflexes classified functionally and activate skeletal muscle
somatic reflexes
Reflexes that activate visceral effectors (smooth or cardiac muscle or glands)
autonomic (visceral) reflexes
Somatic reflexes mediated by the spinal cord
Spinal reflexes
T or F. Spinal reflexes occur without the involvement of higher brain centers
T
Why is testing somatic reflexes important clinically?
to assess the conduction of the nervous system
What do exaggerated, distorted, or absent reflexes indicates what?
degeneration or pathology of specific nervous system regions
What two ways are muscle spindles stretched (and excited)?
By either applying an external force that lengthens the entire muscle
By activating the gamma motor neurons that stimulate the distal ends of the intrafusal fibers to contract. stretching the middle of the spindle (internal stretch)
What does the stretch stimulus cause the antagonists to do?
Relax so they can’t resist the shortening of the stretched muscle
Where is the stretch reflex most important?
large extensor muscles that sustain upright posture and in postural muscles of the trunk
Stretch reflex is essential for what?
Normal muscles tone and activity
How is the patellar or knee jerk reflex elicited?
striking the patellar tendon
What happens when the patellar tendon is striked?
tendon stretches quadriceps
stimulate muscle spindle
quadriceps contract
inhibits antagonist, the hamstrings
Stretch reflexes can be elicited in any skeletal muscle by doing what?
suddenly striking its tendon or muscle itself
All stretch reflexes are?
monosynaptic and ipsilateral
Is the golgi tendon reflex polysynaptic?
Yes
What happens to the muscle in a golgi tendon reflex?
the muscle relaxes and lengthens in response to contraction
Motor neurons in the spinal cord circuits supplying the contracting muscle are inhibited and antagonist muscles are activated
Reciprocal activation
In the golgi tendon reflex, the contracting muscle ____ as the antagonist is ______
relaxes, activated
Protect muscles and tendons subjected to possibly damaging stretching force from tearing and help ensure smooth onset and termination of muscle contraction
Golgi tendon reflex
Initiated by painful stimulus and causes automatic withdrawal of the threatened body part from the stimulus
flexor reflex or withdrawal reflex
Important to our survival, override the spinal pathways and prevent any other reflexes from using them at the same time
protective reflexes
Complex spinal reflex consisting of an ipsilateral withdrawal reflex and a contralateral extensor reflex
crossed extensor reflex
What is an example of a crossed extensor reflex?
stepping barefoot on broken glass
What is important in maintaining balance?
crossed extensor reflex
Elicited by gentle cutaneous stimulation, produced by stroking the skin with a tongue depressor
superficial reflexes
What are two examples of superficial reflexes
plantar, abdominal reflexes
