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what is a reflex
- a rapid, automatic, typically unlearned motor response to a stimulus
- usually removes or opposes the orignial stimulus
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what is the simplest reflexes
monosynaptic: has one synapse
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describe the reflex arc
- a stimulus activates a sensory pain receptor (nociceptor)
- an action potential travels down an afferent neuron
- information processing occurs wiht the interneuron
- an action potential travels down an efferent neuron
- the effector organ responds
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what are the different complex reflexes?
- polysynaptic reflexes: are slower than monosynaptic but can activate more than one effector
- withdrawl reflexes: move a body part away from stimulation
- cross-extensor reflex:
- reciprocal inhibition: blocks the flexor's antagonist stretch to ensure that flexion is in no way interfered with
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what does the bainski sign show?
as descending inhibitory synapses develop, an adult will respond by curling the toes instead, called plantar reflex
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what is the autonomic nervous system?
- controls unconscious adjustment of homeostatically essential visceral responses
- consists of sympathetic and parasympathetic division
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what is the difference in peripheral branches of the SNS and ANS
- they are anatomically different
- SNS: lower motor neurons exert direct control over skeletal muscle (one neuron to skeletal muscle)
- ANS: a second motor neuron always separates the CNS and the peripheral effector (two neurons to cardiac/smooth muscle, glands and fat cells)
- -preganaglionic neuron has cell body in spinal cord, synapses at the ganglion with the ganglionic neuron (postganglionic fiber)
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what is the difference between somatic and autonomic nervous system?
- preganglionic neurons of the ANS send their axons (preganglioinc fibers) to synapse with autonomic ganglia (ganglionic neurons) outside the CNS
- ganglionic neurons send their axons (postganglionic fibers) to innervate effector organs or cells
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Are NT at specific synapses excitatory or inhibitory?
- All synapses between pre and post ganglionic fibers are cholinergic (ACh) and excitory
- most postganglionic sympathetic synapses are adrenergic and usually excitatory
- postganglionic parasympathetic synapes are cholinergic (some excitatory, some inhibitory depending on receptor)
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what is the sympathetic division?
- part of ANS: fight or flight response
- effects are:
- increase in alertness, metabolic rate, sweating, heart rate, blood flow to skeletal muscle
- dilates the respiratory bronchioles and pupils
- blood flow to digestive organs is decreased
- E and NE from the adrenal medullae support and prolong the effect
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describe the process of the sympathetic chain
- arises from spinal segments T1-L2
- preganglionic fibers enter the sympathetic chain ganglia just outside the spinal column
- postganglionic neurons innervate abdominopelvic cavity
- one exception is the adrenal medulla
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what is the parasympathetic division of the ANS?
- has less divergence than the sympathetic division, so effects are more localized
- also called "rest and digest" division
- effects include:
- constriction of pupils, increase in digestive secretions, increase in digestive tract smooth muscle activity
- stimulates urination and defecation
- constricts bronchioles, descrease heart rate
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describe the process of parasympathetic divison
- preganglioninc neurons arise from brain stem and sacral spinal cord
- ganglia very close to or within the target organ
- preganglionic fibers of the sacral areas form the pelvic nerves
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what is dual innervation
- refers to both divisions affecting the same organs
- mostly have antagonistic effects
- some organs are innervated by only one division
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