PSYC 280 Lecture Notes - Lecture 5: Verbascum, Brainstem, Internal Fertilization
8 Jun 2018
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PSYCHOLOGY 280: MODULE 5
3. Copulation (also consider Coolidge effect, many animals can resume mating sooner
if they are provided with new partners)
• The female tends to be the one who decides if copulation occurs
or not (if so, she is said to be sexually receptive, in estrus)
4. Postcopulatory behaviors: behaviours are specialized and varied among species
(could occur copulatory lock like in rates and dogs)
Copulation brings gametes together
• All birds, mammals, and reptiles employ internal fertilization (fusion of gametes,
sperm and egg within female body to form a zygote)
• Other vertebrates (aquatic species like fish and amphibians) employ external
fertilization, release gametes into outside world
• Reproductive behaviours varies according to ecological niche
• Parthegenosis- process of reproduction by which a female produces live offspring
without the need of a male
• Ovulation- the production and release of an egg
• Most of the research is done with rats (attracted largely by smell, and once they are
ready display ultrasonic vocalizations)
Gonadal steroids activate sexual behaviour
• Hormones play an important role in mating behaviour
• Activational effect- temporary change in behaviour resulting from the administration
of a hormone to an adult animal
• e.g. castration of a rat and then giving in testosterone treatment to
bring about the mating behaviour again
• Animals displaying different levels of sexual vigor do not show reliable differences in
blood levels of testosterone (individual differences not determined by testosterone)
• Ovulatory cycle- estrogen is produced in day 4 or 5 of this cycle facilitating
proceptive behaviours of female rats, and therefore subsequent production of
progesterone which increases proceptive behaviour and activates receptivity
• Only correct combination of these two hormones will activate copulatory behaviour
in rats
Neural Circuitry of the Brain Regulates Reproductive Behaviors
• Steriod-sensitive brain regions include the cortex, brainstem nuclei, medial
amygdale, hippocampus, and others
Estrogens and Progesterone
• regulate a lordosis circuit that spans from brain to muscle
• The ventromedial hypothalamus (VMH, hypothalamic region involved in eating and
sexual behaviors) is crucial for lordosis, lessons there abolish response
• Estradiol in tiny quantities injected directly in the brain can increase the receptivity
of females (placed in VMH)
• Estrogen can affect neurons of VMH, causing production of progesterone receptors
• Estrogen can also retract the long primary dendrite of each VMH neuron, and they
reorganize the oxytocin input received by this dendrite from neighboring lateral
regions
• When both estrogen and progesterone are present in the VMH, effect of estrogens
on the length and connectivity of dendrite is reversed
• VMH sends axons to periaqueductal gray region of the midbrain (neuronal body-rho
region of the midbrain surrounding cerebral aqueduct that connects thrid and fourth
ventricles) , lesions diminish lordosis
• Neurons from this area project to the medullary reticular formation (hindmost portion
of the brainstem reticular formation and descending to the spinal cord to modulate
movement), which in turn projects to the spinal cord via the reticulospinal tract
(tract of axons arising from the brainstem reticular formation and descending to the
spinal cord to modulate movement)
• In the spinal cord, this descending signal from the brain is integrated with sensory
inputs from the flanks and rump, stimulated by the mounting of the male. Results
producing a pattern of motor activity which produces lordosis
•ROLE OF VMH: monitor steroid hormone concentrations and, at right time of
ovulatory cycle, activate multi synaptic pathway that induces spinal motor neurons
to contract back muscles, producing lordosis in response to male mounting
Androgens act on neural system for male reproductive behavior
•The hypothalamic medial preoptic are (mPOA, region of the anterior hypothalamus
implicated in the control of many behaviours including thermoregulation, sexual
behaviour, and gonadotropin secretion)
• Chock-full of steroid-sensitive neurons, lesions can abolish male copulatory
behaviour.
• mPOA does not interfere with male motivation to copulate, but are unable to
commence mounting
• mPOA coordinates copulatory behaviour by sending axons to ventral
midbrain, projects to:
1. basal ganglia to coordinate mounting behaviour
2. spinal cord, via several cerebral nuclei
One brainstem nuclei: paragigantocellular nucleus in pons (region of the brainstem
reticular formation implicated in sleep and modulation of spinal reflexes), send
serotogenic fibers down the spinal cord, inhibit circuit responsible for penile erection
For erection to occur mPOA must inhibit inhibitory PGN projection, thereby releasing
spinal spinal circuit to permit erection
Antidepressant drugs boost serotogenic activity in the brain (problems with
erections and orgasm)
Hallmark of Human Sexual Behaviour is Diversity
• Variety of reproductive behaviours is what differentiates human sexuality from other
species
• Humans can experience subjective experiences of sexual behaviour
(ORGASM- climax of sexual experience, marked by extremely pleasurable
sensations)
Response pattern involves four phases:
Document Summary
Psychology 280: module 5: copulation (also consider coolidge effect, many animals can resume mating sooner if they are provided with new partners) Neural circuitry of the brain regulates reproductive behaviors: steriod-sensitive brain regions include the cortex, brainstem nuclei, medial amygdale, hippocampus, and others. One brainstem nuclei: paragigantocellular nucleus in pons (region of the brainstem reticular formation implicated in sleep and modulation of spinal reflexes), send serotogenic fibers down the spinal cord, inhibit circuit responsible for penile erection. For erection to occur mpoa must inhibit inhibitory pgn projection, thereby releasing spinal spinal circuit to permit erection. Antidepressant drugs boost serotogenic activity in the brain (problems with erections and orgasm) Hallmark of human sexual behaviour is diversity: variety of reproductive behaviours is what differentiates human sexuality from other species, humans can experience subjective experiences of sexual behaviour (orgasm- climax of sexual experience, marked by extremely pleasurable sensations) Response pattern involves four phases: excitement (phallus penis and clitoris becomes engorged with blood,
