Chapter 13 Part 1 Flashcards
name the components of the central nervous system and the peripheral nervous system
central nervous system = brain and spinal cord
peripheral nervous system = cranial nerves and spinal nerves
define spinal reflex
a rapid, automatic response triggered by specific stimuli. spinal reflexes are controlled in the spinal cord
do spinal reflexes function with or without input from the brain?
may or may not have input from the brain. not required
does the human body have more sensory, motor, or interneurons?
rank them
most – interneurons (20 billion)
next - sensory neurons (10 million)
least - motor neurons (half a million)
what are “neuronal pools”?
functional groups of interneurons
do neuronal pools have excitatory or inhibitory neurons?
may contain both
name the 5 classifications by organization of neuronal pools
divergence
convergence
serial processing
parallel processing
reverberation
“divergence” is a mechanism for doing what?
spreading stimulation to multiple neurons or neuronal pools in the CNS
are interneurons only in the CNS?
YES
Convergence is a mechanism for…
providing input to a SINGLE neuron from multiple sources
serial processing is a mechanism in which….
neurons or neuronal pools work SEQUENTIALLY
straight line
parallel processing is a mechanism in which…
neurons/neuronal pools process the SAME information AT THE SAME TIME (simultaneously)
reverberation is…
a positive feedback mechanism
once a reverberating circuit has been activated, it will continue until synaptic fatigue or an inhibitory stimulus breaks the cycle
highly complicated examples of reverberation among neuronal pools in the brain may help with what?
maintaining consciousness, muscle coordination, and normal breathing
when sensory neurons bring information to the CNS, what organization of neuronal pools is involved?
DIVERGENCE. the CNS spans over a wide area – the brain and the spinal cord
before parallel processing can take place, __________ must occur
divergence
classify reflexes based on DEVELOPMENT
innate reflexes – connections that form between neurons during development. withdrawal from pain, chewing, suckling, tacking objects with the eyes
r
acquired reflexes – more complex and learned. ie: driver stepping on break
can reflexes be modified over time, or suppressed through conscious effort?
YES
if youre walking a tightrope, you can suppress the feeling of the bee sting on your hand, where under other circumstances your reflexes may cause you to do otherwise
classify reflexes based on RESPONSE
somatic reflexes – skeletal muscle contraction. superficial and stretch reflexes
visceral (automatic) reflexes – smooth and cardiac muscles, glands, and adipose tissue
somatic reflexes provide a mechanism for the ______ control of the muscular system (voluntary or involuntary?)
INVOLUNTARY
differentiate between superficial reflexes and stretch reflexes
superficial reflexes are triggered by stimuli at the SKIN or MUCOUS MEMBRANES
stretch reflexes are triggered by the sudden elongation of a tendon, and thus of the muscle to which it attaches
give an example of a stretch reflex
patellar or “knee jerk” reflex
are the movements by somatic reflexes delicate or precise?
NO
why are somatic reflexes needed, being that we HAVE voluntary control over the skeletal muscular system?
because somatic reflexes are IMMEDIATE. voluntary responses take more time, and in an emergency, you don’t have that extra time
can somatic reflexes be modified later?
yes
classify reflexes based on the complexity of the circuit
monosynaptic (1 synapse)
polysynaptic (multiple synapses. 2-several hundred)
classify reflexes based on the PROCESSING SITE
spinal reflexes (processed in spinal cord)
cranial reflexes (processed in the brain)
do spinal reflexes go to the brain?
NO — therefore they are much faster
do monosynaptic reflexes involve an interneuron?
NO – just the presynaptic and postsynaptic neuron
are most reflexes polysynaptic or monosynaptic
poly
“polysynaptic reflexes can produce far more complicated responses than monosynaptic.”
explain this statement
the interneurons involved in a polysynaptic reflex can control motor neurons that activate several muscle groups simultaneously
in a monosynaptic reflex, what serves as the processing center?
the motor neuron
which are faster - monosynaptic or polysynaptic reflexes
mono
what is the best known monosynaptic reflex
the stretch reflex (patellar reflex)
in the patellar stretch reflex, what is the stimulus?
increased muscle length
the receptors in stretch reflexes are called….
muscle spindles
explain what happens during the patellar reflex
the sensory receptors (muscle spindles) detect an increase in muscle length. this then triggers the sensory nuclei to trigger the motor nuclei to coordinate and send a response to an effector (muscle) to COUNTERACT the stimulus and contract the muscle, shortening it
many stretch reflexes are ____ reflexes
postural — reflexes that help us to maintain an upright posture
ex: standing
explain 2 reasons why polysynaptic reflexes can produce far more complicated responses than monosynaptic
-polysynaptic has more interneurons
-the interneurons can produce IPSP’s or EPSP’s at CNS motor nuclei. therefore, the response can involve the stimulation of some muscles and the inhibition of others
give an example of a withdrawal reflex
the flexor reflex – ie: touching a hot stove
during the flexor reflex, ___ are stimulated and ____ are inhibited
what is the term for this and what accomplishes it?
flexors are stimulated and extensors are inhibited
this is called reciprocal inhibition
this is accomplished by interneurons in the spinal cord.
in theory, the contraction of a flexor muscle should trigger the stretch reflex in extensors would cause the extensors to contract, opposing the movement
the crossed extensor reflex is coupled with what other reflex?
explain
the flexor reflex (withdrawal)
when we step on a tack, the flexor reflex causes our foot to move up from the ground.
the crossed extensor reflex works on the OTHER leg. (uninjured). it EXTENDS the muscles on the uninjured leg to maintain balance since our injured foot is being lifted off of the ground due to the flexor reflex
what reflexes are ipsilateral? what reflexes are contralateral?
ipsilateral – sensory stimulus and motor response occur on SAME SIDE OF THE BODY
contralateral – the motor response occurs on the side OPPOSITE the stimulus
ipsilateral = stretch reflex, flexor (withdrawal) reflex, tendon reflex
contralteral = crossed extensor reflex
spinal reflexes can be activated by which 2 things?
-external stimuli
-higher centers of the brain
motor control involves a series of interactive levels.
name the lowest level of control and the highest level
lowest level = monosynaptic reflexes. rapid, stereotyped, and inflexible
highest level = centers in the brain that can modulate or build on reflexive motor patterns
if a single EPSP does not depolarize the presynaptic neuron enough to generate an action potential, what has happened instead?
that neuron is now more sensitive to excitatory stimuli.
this process is called FACILITATION
an IPSP makes the neuron _____ responsive to excitatory stimuli.
this is called ______
less
inhibition
when many of the excitatory synapses are chronically active, what can happen to the postsynaptic neuron?
it can enter a state of generalized facilitation. this facilitation of reflexes can result in REINFORCEMENT — an enhancement of spinal reflexes
can spinal reflexes be suppressed consciously?
YES – as long as they’re not reinforced
reinforced reflexes are usually too strong to consciously suppress
in adults, stroking the lateral sole of the foot will cause what?
what if this is done in babies?
in adults, the toes will curl. this is called the plantar reflex. it is in inhibitory response by descending fibers
in babies, they will spread their toes (called the babinski sign, or positive babinski reflex)
when does the babinski sign disappear?
as descending motor pathways develop
if the babinski sign appears in an adult, what does this indicate?
the higher centers or descending tracts are damaged. CNS injury
