L51 Autonomic Control Circuits Flashcards
define micturition.
urination, passage of urine
define Zeitgeber.
environmental signal which triggers the circadian clock
light with an intensity of more than 3000 lux is the most potent circadian zeitgeber
what do parasympathetics do to the pupil?
constrict
midbrain –> ciliary ganglion –> short ciliary n.
what do sympathetics do to the pupil?
dilate
*hypothalamo-spinal fibers important here + for motor efferents
where do the hypothalamo-spinal fibers originate and where do they head?
- in the hypothalamus and descend to the upper thoracic intermediolateral cell column level of the spinal cord
- they exit to reach the superior cervical ganglion and post ganglionics constrict the pupil
what does disruption of the descending peripheral sympathetic division of the pupil result in?
tonically constricted pupil
what are the 3 levels of control of the urinary bladder?
- supratentorial = frontal cortex (motor strip) + hypothalamus
- Subtentorial = pontine micturition center
- spinal =
- lower thoracic and upper lumbar - sympathetic
- midsacral - parasymapthetic + somatic (voluntary)
where does bladder control originate?
frontal cortex (motor strip) and hypothalamus
what controls micturition
the pontine micturition center
where do the sympathetic efferent originate wrt autonomic control of the bladder?
in the lower thoracic/upper lumbar segments
what role does sympathetics have on the bladder?
relax detrusor
constriction of internal sphincter
allows for filling
where do the parasympathetics efferent originate wrt autonomic control of the bladder?
sacral segments
what role does the parasympathetic have on the bladder?
constriction detrusor
relaxation of internal spinster
allows for emptying
where do somatic efferents originate wrt autonomic control of the bladder?
sacral segments
what role does somatic efferents have on the bladder?
relax the external sphincter which allows for emptying
describe filling of the bladder.
sympathetic innervation maintains the detrusor relaxes and the internal sphincter constricted to allow filling
describe emptying of the bladder.
- sensory afferents (soma in DRG) int he bladder wal relay info back to the ventral horn of S2-4
- they synapse on both parasympathetic efferents - one to detrusor and one to internal sphincter
- info is also relayed back to high centers (pontine micturition center) and the cortex to reach out consciousness – the cortex and the pons provide meaningful bladder control
what are the 2 major levels of control of autonomic control of reproductive organs?
brain and spinal cord
what is the brains role in the control of autonomic control of reproductive organs?
contributes to sexual arousal via erotic stimuli including visual, olfactory and somatosensory
what is the spinal cords role in the control of autonomic control of reproductive organs?
- receives sensory input from the genitalia and descending input from the brain
- also controls reproductive function via ANS efferents
- -sympathetic - prostate gland (ejaculation), uterine and vaginal walls (contraction)
- -parasympathetics - vagina, clitoris and erectile tissue of the penis
define circadian rhythm?
periods of activity alternate with period of inactivity
what is an example of a physiological parameter that will vary as the active and inactive periods vary?
body temperature
*it does not follow the sleep wake cycle exactly, but the temperature of the body begins to rise as the person approaches their time of awakening triggered by the “internal clock”
daily activity patterns persisted in the absence of ____ hence the concept of “Internal clock”.
external time cues
the clock ____ precisely represent the exact 24-hour cycle of a calendar day.
does NOT
why does the internal clock drift to the right?
because the clock is slow running on an average of 25-hour days
in the absence of external time cues, the biological clock ____ maintain precise timing.
CANNOT
what is the “home of the biological clock” and the very thing that generates rhythmic output and resets every morning at the onset of light?
suprachiasmic nucleus
what activates the clock?
light sensitive cells in the retina (different from your average photoreceptor)
the signal from the light sensitive retina cells is sent via _____ and synapse in the suprachiasmic nucleus.
retino-hypothalamic tract
neuronal output from the suprachiasmic nucleus controls ____ from the pineal gland.
melatonin –“dark hormone”
what does melatonin influence?
metabolic rate
humoral output form the suprachiasmic nucleus may also include rhythmic secretion of?
ADH
describe Horner’s syndrome.
unilateral myosis
- ptosis
- facial anhydrosis
- facial flushing
- due to underactive ipsilateral sympathetic outflow
what are the possible causes of Horner’s syndrome?
- lesion/transection of the hypothalamospinal pathway in the cervical region
- preganglionic lesion (on the chain)
- postganglionic lesion at the level of the internal carotid (tumor in cavernous sinus)
describe automatic bladder.
- some its with spinal cord transections will regain sacral reflexes
- in this case, the reflex to empty the bladder recovers and when the bladder reaches threshold, the reflex response will spontaneously empty the bladder
describe atonic bladder.
- dorsal nerve root lesions interrupt afferent sensory fibers making the pt lose the sensation of fullness
- as the bladder fills, a constant dribbling will occur
describe jet lag.
dark/light cycle no longer parallels the endogenous circadian clock system typically causing temporary insomnia which is sometimes treated with mild dose of melatonin prior to falling asleep
describe the sleep/wake disorders in the blind.
- very common in the absence of visual input (zeitgeber)
- pacemakers are not entrained to social cues and suffer from sx similar to jet lag
describe SAD.
- “winter depression” changing moods and sleep patterns
- due to daylight changes and its tx with light therapy to suppress melatonin synthesis
