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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
what is the simplest reflexes
monosynaptic: has one synapse
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
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
what does the bainski sign show?
as descending inhibitory synapses develop, an adult will respond by curling the toes instead, called plantar reflex
what is the autonomic nervous system?
- controls unconscious adjustment of homeostatically essential visceral responses
- consists of sympathetic and parasympathetic division
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)
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
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)
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
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
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
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
what is dual innervation
- refers to both divisions affecting the same organs
- mostly have antagonistic effects
- some organs are innervated by only one division