PNS and reflex activity (ch 13) Flashcards
the CNS sends info
out
effectors are activated when
a NT is secreted onto an effector organ
where does innervation of skeletal muscle take place
at the level of the neuromusculojunction (NMJ)
what is the neurotransmitter involved in skeletal muscle innervation
Acetylcholine (ACh)
steps of skeletal muscle innervation
nerve impulse reaches axon terminal to release ACh, which binds to receptors and results in excitation (movement of Na+/K+ across the membrane, depolarization of muscle cell), end plate potential triggers an AP in the cell, resulting in contraction
autonomic motor endings and visceral effectors are _____ than somatic junctions
simpler
steps of visceral muscle and gland innervation
branches form synapses en passant via varicosities, two different NTs (ACh and NE(norepinephrine)) act indirectly via second messenger systems
compared to somatic, visceral motor responses are
slower
in skeletal muscle, the cerebellum and basal nuclei are
the main coordinators of muscle control
_____ motor behavior depends on _____ patterns of control
complex, complex
what are the three levels of motor control in skeletal muscle
segmental, projection, pre-command
the segmental level of motor control is
the lowest level of motor hierarchy
the segmental level involves
reflexes, spinal cord circuits, and central pattern generators (CPGs)
T/F: the segmental level is not conscious
true
CPGs are
segmental circuits that activate networks of ventral horn neurons to stimulate specific groups of muscles
the projection level of motor control consists of
the precentral gyrus (cortex, brain stem motor areas)
the cortex contains _____ that initiate the _____
upper motor neurons, direct (pyramidal) system
the brain stem motor areas oversee the _____
indirect (extrapyramidal) system
the direct pyramidal system involves
voluntary movement
the indirect (extrapyramidal) system involves
reflexes and CPGs
projection level motor pathways send information to _____ and let _____ know what is happening
lower motor neurons, higher command levels
the precommand level is
the highest level of motor control
what occurs in the precommand level
neurons in the cerebellum and basal nuclei control outputs of the cortex and brainstem
functions of the cerebellum
- act on motor pathways through projection areas located in the brainstem
- act on motor cortex via the thalamus (sensory relay station)
functions of the basal nuclei
- at rest, acts to inhibit motor centers
- when you need to move of change movement, it stops motor inhibition
parkinson’s results in
a resting tremor and stiffness/lack of movement
a reflex is
a rapid, predictable, involuntary motor response to a given stimulus
two categories of reflexes
autonomic and somatic
there are more of this type of reflex
autonomic
autonomic reflexes involve
smooth muscle, cardiac muscle, and glands
examples of autonomic reflexes
sweating when hot, increasing heart rate when exercising, salivating when eating
somatic reflexes involve
skeletal muscle
examples of somatic reflexes
knee jerk, shivering, cough, sneeze
steps of the reflex arc
receptor picks up a stimulus, sensory neurons carry the info (APs) to the CNS, integration of synapses occurs in the CNS, motor neurons carry APs away from the CNS, effector gives a response
speed of skeletal muscle
quick
parts of the muscle stretch reflex
muscle spindle (receptor), alpha motor neurons (outside)
parts of the muscle spindle
- intrafusal muscle fibers (made of skeletal muscle cells)
- sensory neurons
- motor neurons
types of sensory neurons and their functions
- type I responds to stretch speed
- type II responds to stretch degree/amount
function of gamma motor neurons
adjust spindle/intrafusal therefore adjusting the spindle response
function of alpha motor neurons
acts on extrafusal fibers
alpha and gamma motor neurons are stimulated _____ so _____
together, the spindle can still respond at various muscle lengths
events of the muscle stretch reflex
stretched muscle increases APs to CNS via a sensory neuron, sensory neuron synapses with alpha motor neuron of the stretched muscle and inhibitory interneuron to inhibit the alpha motor neuron of the antagonist muscle, stretched muscle contracts and the antagonist relaxes
example of muscle stretch reflex
knee jerk reflex (knee/quads contract, hamstrings relax)
examples of somatic reflexes
- withdrawal reflex
- crossed extensor reflex
- golgi tendon organ reflex
- superficial spinal reflexes (babinski)
the withdrawal reflex is
pulling away from painful stimuli
the crossed extensor reflex is
where one side flexes and the other side extends
the crossed extensor reflex is
where one side flexes and the other side extends
the golgi tendon reflex
acts to inhibit the muscle from pulling too hard on a tendon
the babinski reflex is
when the toes flex in response to a stimulus on the bottom of the foot
the babinski reflex develops around age
1-2
examples of autonomic reflexes
digestive - stomach stretch moves colon
cardiovascular - heart rate, BP, vessel flow
integument/skin - sweat, goosebumps
senses (eyes) - pupil, focus
urinary - bladder contracts
reproductive - childbirth, orgasm
what information is gained by testing the reflexes
- function of nerves
- spinal cord/brain function at various levels
- degree of stimulation or inhibition of motor areas from brain
