Chapter 13 bold terms Flashcards
Peripheral nervous system (PNS)
Links CNS to body and to external environment
Sensory division
Consists of sensory (afferent) neurons that detect and transmit sensory stimuli to CNS; has 2 anatomical subdivisions
Somatic sensory division
Detects both internal and external stimuli, detect stimuli from skin
Visceral sensory division
Relays information (like blood pressure) from organs of abdominopelvic and thoracic cavaties
Motor division
Consists of motor (efferent) neurons; carry out motor functions of nervous system
Somatic motor division
Responsible for voluntary motor functions; composed of lower motor neurons (somatic motor neurons), directly trigger skeletal muscle contractions
Visceral motor division (autonomic motor nervous system, ANS)
responsible for maintaining many aspects of homeostasis by controlling involuntary motor functions in the body; innervate cardiac muscle cells
Sympathetic nervous system (fight or flight division)
involved in homeostasis activities surrounding physical work and visceral responses of emotions
Parasympathetic system (rest and digest division)
involved in digestion and maintaining body’s homeostasis at rest
Peripheral nerves
Main organs of PNS; consist of axons of many neurons bound together by connective tissue
Mixed nerves
Contain both sensory and motor neurons
Sensory nerves
Contain only sensory neurons while motor nerves contain mostly motor neurons
Spinal nerves
Originate from spinal cord and innervate structures below head and neck
Epineurium
outermost layer of connective tissue that holds motor and sensory axons together
Fascicles
Small groups of bundled axons surrounded by connective tissue called perineurium
Cranial nerves
Attach to brain and mostly innervate structures in head and neck; allows for purely sensory, mixed and mostly motor nerves
Spinal nerve
Short and divides into following 2 mixed nerves; both carry both somatic motor and sensory information
Posterior ramus
Travels to posterior side of body
Anterior ramus
Travels to anterior side of body and/or to an upper or lower limb
Hiccups
annoying spasms of diaphragm that cause a forceful inhalation of air
Sciatic nerve
longest and largest nerve in body; contains axons from both anterior and posterior divisions of sacral plexus
Exteroceptors
usually close to bodys surface; detect stimuli originating from outside body
Interoceptors
usually found within bodys interior; detect stimuli originating from within body itself
Mechanoreceptors
Depolarize in response to anything that mechanically deforms tissue where receptors are found; mech gated ions allow for sensory transduction (vibration, light touch, stretch, and pressure)
Themoreceptors
Exteroceptors, most of which are slowly adapting receptors; depolarize in response to temp change
Chemoreceptors
can be interoceptors or exteroceptors; depolarize in response to binding to specific chemicals (in fluids or air); generate a receptor potential as sodium ion channels open
Photoreceptors
special sensory exteroceptors found only in eye; depolarize in response to light
Nociceptors
Usually slowly adapting exteroceptors; depolarize in response to noxious stimuli
Referred pain
Phenomenon whereby pain that originates in an organ is perceived as cutaneous pain
Upper motor neurons
neurons of primary motor cortex make decision to move and initiate that movement; but not in contact with muscle fiber itself
Lower motor neurons
receive messages from upper motor neurons; in contact with skeletal muscle fibers; release acetylcholine onto muscle fibers to initate contraction
Reflexes
Programmed, automatic responses to stimuli; occur in a three-step sequence of events called a reflex arc; usually protective negative feedback loops
Monosynaptic reflexes
simplest reflex arcs; involve only a single synapse within spinal cord between a sensory and motor neuron
Polysynaptic reflexes
More complicated types of reflex arcs; involve multiple synapses
Simple stretch reflex
Bodys reflexive response to stretching of muscle to shorten it back to within its “set” optimal length
Simple stretch reflexes
Patellar reflex and jaw jerk reflex
Golgi tendon reflexes
polysynaptic reflexes; protect muscles and tendons from damaging forces
Flexion or withdrawal reflex
Involves rapidly conducting nociceptive afferents and multiple synapses in spinal cord; act to withdraw limb from painful stimuli
Crossed extension reflex
Occurs simultaneously on opposite side of body for balance and postural support while other limb is withdrawn from a painful stimulus
Cranial nerve reflexes
Polysynaptic reflex arcs that involve cranial nerves
Gag reflex
Triggered when visceral sensory nerve endings of glossopharyngeal nerve in posterior throat are stimulated
Corneal blink reflex
triggered when a stimulus reaches somatic sensory receptors of trigeminal nerve in thin outer covering of eye (cornea); something contacts eye leading to a blink response
Amyotrophic lateral scelrosis (ALS) or Lou Gehrig’s disease
Involves degeneration of cell as well as upper motor neurons in cerebral cortex; cause of degeneration is unknown at present
