Download Human Sexual Response A. Signs of arousal Divisions of the

Human Sexual Response
A. Signs of arousal
1. physical signs
a. increased cardiovascular activity
increased :
respiration
blood pressure
heart rate
b. increased blood flow to: penis (male) erection
clitoris, vagina and vulva (female)
2. generalized hormal changes during arousal
a. epinephrine(E) and norepinephrine (NE)
“sympathetic adrenal hormones” produced and secreted by adrenal glands
norepinephrine
Divisions of the Nervous System
released as
neurotransmitter
I. CNS (central nervous system)
from neurons in
II. PNS (peripherial nervous system)
sympathetic
A. Somatic nervous system
nervous system
voluntary/skeletal muscle control
i. cardiovascular
B. Autonomic nervous system
activity because acts on smooth muscle, cardiac muscles, and glands
metabolic rate
1. parasympathetic
ii. inhibit many nonsends signals to conserve and store energy
immediately
2. sympathetic
essential
sends signals to expend energy
activities
(fight or flight response)
such as digestion
and blood
flow to penis/clitoris
Notes:
E and NE return to normal when stimulus removed
NE released when anxious, afraid, or cold
NE inhibits erection:
by binding to specific receptors (α-adrenoreceptors) in penis
erection only possible/maintained if antagonists present
antagonists bind to and block α-adrenoreceptors
b. slight of lutenizing hormone (LH)
role in arousal unknown
general functions: stimulates production of
estrogens in females
androgens in males
c. slight of testosterone
role in arousal unknown
d. of prolactin
only if climax
sexual response notes
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B. Pathways to arousal/erection
1. the non-aroused state
flaccid – low blood flow to penis (5ml/min)
a. muscles in penis are contracted
allows blood to enter and leave
b. brain sends signals that inhibit erection
inhibit “erection generating center” (EGC) in spinal cord
through sympathetic nerves – release serotonin – inhibits EGC
(Note: inhibition is turned off during REM sleep)
c. anything that stimulates the sympathetic n.s. (or increases E & NE)
inhibits EGC by sympathetic neuron activity
2. A reflex arc – the spinal erection reflex
general
stimulus
receptors
sensory (afferent) neuron
integrating center in spinal cord
motor (efferent) neuron
effector - muscle
specific
tactile receptors in genitals
erection generating center (EGC)
parasympathetic (excitatory) neurons in penis
3. the erection process
a. stimulation of excitatory parasympathetic neurons in penis
b. parasympathetic neurons release neurotransmitters:
acetylcholine
stimulates endothelial cells in penis to release NO
nitric oxide (NO)
NO causes in production of cGMP
cGMP causes smooth muscles to relax
blood vessels dilate
blood flow (penis/clitoris)
spongy tissue fills with blood
veins compressed
blood can’t leave (more enters than exits)
erection
4. Sources of stimulation = pro-erectile messages.
signals initiate in…
a. tactile receptors
i. in genitals – requires direct stimulation
signal sent to reflex arc
ii. in other areas
signal sent to hypothalamus
b. other sensory organs/receptors
-smell
-images
-tastes
-sounds
signals sent to brain
sexual response notes
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c. brain
areas interconnected
-cerebral cortex
signals that originate in cortex and limbic system sent to hypothalamus
-limbic system
- other areas
i-hypothalamus
organizes and integrates signals from many sources
if releases oxytocin
parasympathetic neurons stimulated
erection/arousal
if releases something other than oxytocin
sympathetic neurons stimulated
inhibits erection/arousal
ii-learning and memory can have a strong influence on erections
cues: fetish objects
iii-mood
can effect pro-erectile messages
5. the effect of some chemicals on the pathway
a. parasympathetic neurons release nitric oxide (NO)
NO causes in production of cGMP
cGMP is normally broken down by the enzyme, phosphodiesterase
Viagra blocks phosphodiesterase
cGMP causes smooth muscles to relax
papaverine injected
induces smooth muscle relaxation
blood vessels dilate
blood flow
spongy tissue fills with blood
veins compressed
blood can’t leave
erection
b. sympathetic neurons release norepinephrine (NE)
pentolamine, injected into penis, blocks NE
NE inhibits erection
sexual response notes
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C. Orgasm
A reflex
general
stimulus
receptors
sensory (afferent) neuron
integrating center
motor (efferent) neuron
effectors
sexual response notes
specific
physical or mental
in penis or clitoris and G-spot
in spinal cord
sympathetic neurons
glands secrete (emission in males)
organ
secretes
sperm
vas deferens%
prostate
fluid
prostate %
seminal
fluid
seminal vesicles %
Skenes glands &
muscles contract
males
females
muscles in pelvic region
penis
uterus
parts of vagina
(causes ejaculation)
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