Sexual reflexes Flashcards
MPOA
medial preoptic area of hypothalamus
projects to:
- hypothalamic paraventricular nucleus
- midbrain (ventral tegmental area)
- brainstem nuclei (raphe and gigantocellular)
then project to autonomic and somatic spinal centres commanding peripheral nerves
Sexual hormone function
Estrogen: permissivity
Testosterone: initiation
Progesterone: receptivity
Peripheral effects of hormones on sexual function
VIP –> v/c
NPY and substance P –> unknown effect on v/c
Serotonin sexual function
inhibits interest, genital arousal and orgasm
ACh sexual functions
? effect on interest
facilitates genital arousal and orgasm
Noradrenaline sexual functions
facilitates interest and orgasm
inhibits genital arousal
Dopamine sexual functions
facilitates interest and genital arousal
? effect on orgasm
Psychogenic centre of sexual function
T10-L3
Reflexogenic centre of sexual function
sacral afferents and efferents
Cervical injury (T11-L3) - sexual function
Reliant on sacral reflex erection/vaginal arousal (need sexual touch)
the higher/more complete the lesion, the better the sacral reflex responses
Sacral injury - sexual function
below T9
reliant on mental erection/vaginal arousal
Injury between cervical and sacral centres - sexual function
communication between centres disrupted;
get both psychogenic and reflex dysfunction
Tx of ED
PDE5 inhibitor
viagra
cialis
levitra
Women sexual dysfunction Tx
only erectile tissue will be affected by PDE5i
SCI may help if incomplete
since it only affects erectile tissue, may increase sensation due to vasocongestion –> helps 1/3 women with MS
does not directly influence sexual drive or orgasmic capacity
Physiology of ejaculation
spinal cord reflex involving coordination between T10-S4
Central inhibitory control over spinal cord reflex
Ejaculatory inevitability - closure of the bladder neck with seminal emission with concomitant closure of external sphincter, increasing intraprostatic pressure
Phases of ejaculation
Seminal emission: sympathetic T10-L1; some voluntary control Propulsatile ejaculation (expulsion): parasympathetic and somatic, loss of voluntary control
Ejaculation centres
T12-L1: sympathetic centres (emission)
L3-L4: lumbar spinothalamic: spinal generator of ejaculation
S1-3: somatic (expulsion); PSNS (secretion)
Ejaclation with out orgasm causes
spinal cord injury
MS
Anhedonic ejaculation
Orgasm without ejaculation cause
prostate removal
Retrograde ejaculation
Retroperitoneal lymph node dissection
Tx of ejaculatory dysfunction
penile vibrostimulation
Reliant on an intact lumbosacral reflex
Reflex erections and +BCR promising signs
higher the lesion - less interference
Electroejaculation: more invasive etc. reliant on efferent component of reflex
Bulbocavernosus reflex
squeeze glans penis and watch for responsive pelvic floor contraction
Reflective of intact sensory and motor sacral pathways (not autonomic)
Predictive for: reflex erection/vaginal arousal, ejaculation to VS
Positive is confirmatory
Voluntary anal contraction
downgoing CST
rectal insertion for true voluntary anal contraction
Testicular squeeze test
positive:
innervation of T9 to brain must still eb intact - injury must be below T9
pain upon squeezing both testes
