Physiology of Sexual Action and Sexual Response

Physiology of Sexual Action and Sexual Response

• The presentation will cover female and male anatomy, the limbic system, the autonomic nervous system, the endocrine basis of female and male sexuality, the physiology of sexual action, and the sexual response in men and women

Female External Genitalia

• The labia majora are folds of fat and connective tissue extending down from the mons pubis
• The skin covering the labia majora is covered with hairs after puberty
• Labia majora protect the labia minora, urethral and vaginal openings
• The labia majora contain many veins and nerves
• The labia minora are located below the labia majora and are rich in vessels and nerves
• The labia minora are covered with a thin layer of epidermis, and do not contain hair follicles
• The clitoris is a short, cylindrical, erectile organ located at the top of the labia minora
• The clitoris contains many veins and nerves, which means tears and injuries can cause a lot of bleeding
• The vestibule allows both the urethra and vagina to open
• The bilateral Bartholin glands and hymen are located in the vestibule on the outer portion of the vagina
• The surface of the vestibule has a thin mucosal structure, so it is easily irritated by chemicals, heat, discharge, and tight clothing
• The hymen is an elastic mucous membrane that partially covers the vaginal opening with holes
• The holes will allow menstrual blood to flow out
• Rarely, the hymen may be completely closed (imperforated hymen), trapping menstrual blood inside, which ultimately requires a hymenotomy

Bartholin Glands

• The Bartholin glands are the largest glands in the vulva
• They’re located on both sides of the vagina and open the vestibula with its ducts
• The Bartholin glands provide vaginal lubrication by secreting secretions during sexual stimulation

Vagina

• The vagina has a length of 8-10cm, connecting the vulva to the uterus
• It's tubular, and made of muscle and membranes
• In the unborn, the front and back walls touch each other
• The upper part wraps around the cervix from the outside in a ring, adhering to the wall of the cervix
• The part of the cervix that remains inside the vagina is referred to as the "Porsio"
• The recesses between the porsio and the walls of the vagina are called the "Fornix"
• The vaginal mucosa is made up of layers with folds, called rugae, allowing for expansion during childbirth
• The vaginal mucosa responds to estrogen and progesterone, therefore pH is acidic helping to prevent infection
• When estrogen is withdrawn during menopause, the pH of the vagina shifts to alkaline resulting in senile vaginitis
• In addition to being the birth canal, the vagina is a channel through which menstrual blood flows and coitus takes place

Male Reproductive System

• The penis and scrotum form the external reproductive organs in the male reproductive system

Penis

• The penis has three cylindrical spongios (spongy) layers
• 2 corpus cavernosa
• Corpus spongiosum
• The urethra is enclosed in the corpus spongiosum
• Blood vessels and nerves also pass through this spongios layer
• The fullness in the blood vessels causes the penis to erect during sexual excitement
• The tip of the penis is called the glans penis and is highly sensitive for having many nerve endings

Scrotum

• The scrotum carries the testicles and spermatic cords in it
• Blood vessels, nerves, muscle fibrins, and the ductus-vas deferens pass through the spermatic cords
• The spermatic cord enters the abdomen through the inguinal canal
• The internal reproductive organs in men are the duct system that allows for storage and transport for both the testicles and spermatazoa

Testicles

• There are two testicles located inside the scrotum, each approximately 4 cm in length
• Each testicle is suspended inside the scrotum by the spermatic cord (Funiculus spermaticus)
• Each spermatic cord is made up of seminal ducts, arteries, veins, lymphatic vessels, and nerves
• The testicles have two functions: Exocrine to make sperm and endocrine by secreting hormones

Physiology of Sexual Behavior

• The Limbic system, Autonomic nervous system, Central nervous system, and Medulla spinalis all contribute towards the physiology of sexual behavior

Limbic System

• The limbic system controls the affective state and the factors that motivate action, especially in relation to fear, anger, and sexual behavior
• It regulates the basic function of processing and regulating emotions and memory as well as sexual arousal and learning
• Located in the lower right side of the cerebrum, or on either side of the Thalmus, the limbic system helps manage emotional reactions
• Issues in the limbic system can cause psychological triggers and negative consequences
• The Limbic system contains the hypothalamus, hippocampus, thalamus and amygdala

Limbic System Tasks

• Behaviors necessary for sustaining existence like eating, drinking, anger, rage, fighting, or escape
• Behaviors related to the continuation of species through coupling for reproduction, offspring care and nurture
• Adapting the visceral activities in relation to the above behaviors

Motor Systems

• There are two parts of the nervous system that control motor functions
• Somatic motor system which works voluntarily like moving limbs
• Autonomic engine system which works involuntarily like hormone secretion

Autonomic Nervous System

• Consists of nerve fibers that do not have a myelin sheath
• Controls the operation of involuntary activities
• Physiologically, divided into two parts: Sympathetic and Parasympathetic Nervous System
  • The Sympathetic Nervous System is mostly activated in times of stress, danger and excitement
    • Speeds up the vessel beats and breathing
    • Pupils dilate, increases sweating, and blood sugar rises
    • Capillaries constrict
    • Saliva secretion decreases
    • The movements of the stomach and intestines decrease (digestion slows down)
    • Kidney activity slows down
    • Bladder relaxes
  • The Parasympathetic nervous system balances when danger or excitement pass
    • Salivation increases
    • The movements of the stomach and intestines are accelerated (digestion is accelerated)
    • Kidney activity increases
    • The bladder contracts
    • Beats and breathing slow down
    • Pupils shrink
    • Capillaries dilate
    • Blood sugar decreases

Sexual Function and Behavior Neuroendocrine Regulation

• Determined from the interplay of the sexual organs, nervous and endocrine systems and neurochemical, neurophysiological and psychological systems
• Diseases, adverse environmental conditions, drugs, alcohol, can affect sexual function
• Signals for the genitals and other areas are focused in the brain
• Chemical and electrical impulses travel through the peripheral nerves and spinal cord to the relevant parts of the body
• The genitalia and pelvic floor muscles are regulated by the sympathetic and parasympathetic nervous system which can be controlled
• The autonomic nerves regulate blood flow and help in involuntary smooth-muscle contractions accompanying arousal
• Somatic nerves control the voluntary or striated muscle responses that often occur during orgasm

Hypothalamus Functions

• The hypothalamus helps Coordinate somato-motor and viscera-motor activities
• Body water balance and control of thirst and Body weight control
• It is key for controlling reproduction and sexual behavior
• The hypothalamus helps regulate body temperature as well as and sleep
• Excitement, Fear and Anger, and Control of the endocrine system is regulated by the hypothalamus

Endocrine Basis for Female Sexuality

• A first in line influence is both estrogen and progesterone
• Ovaries under the control of gonadotropin are responsible for production
• Estrogen is necessary to help maintain the normal condition of the vaginal mucosa, and helps for lubrication
• Androgens, made in the ovary and cortex also change the level of the ovulation

Androgen Role

• Desire and interest, for sexuality is often associated

Estrogen Roles

• Is is key for sexual intercourse desire

Progesterone Role

• Can suppress feelings of active lovemaking, and sexuality but increase those connected to maternity and cuddling

Three basic sex hormones for males

• Testosterone, dihydrotestosterone, and androstenedione
• Testosterone and androstenedione are produced in leydig cells
• Testes under the control of hormone LH are a control factor
• Although, amounts are small adrogens which are essential are mainly in dihydrotestosterone
• Basal cell sex hormones: main roles include sustaining sexual and desire, assisting capacity to eject, formation and and or maintenance of an erection

Physiology of Sexual Action

• Human sexual response is normally inactive
• Prepares the genital organs for intercourse with the opposite sex
• It is highly organized
• It is a regular biochemical, physiological and psychological process

Female Sexual Behavior

• Similarities in sexuality between men and women exist
• Women have an accumulation of arousal with sex, that don't require specific physical stimuli
• It takes place as a psychological experience
• Accumulation of the psycho-sexual arousals, are essential for sexuality to be released in the Clitoris

Phases of sexual response

• There are four key phases of sexual response including arousal, plateau, orgasm, and thawing

Sexual Response Cycle

• The divisions within the response including arousal and orgasm can further be divided into several phases
• Sexual desire phase in 1 second to years in can last which is linked to sexuality
• Excitation is connected to the male errotic feelings, diffused vaso congestion which is a blood supply boost in the female
• Intensity of of thoughts can be increase from stimuli both sexual and stimuli, both physical and stimuli emotional
• Arousal phase as well as the stimulation should be both psychologically and physically pleasing
• Arousal phase in female, from mucous the phase is increased by some time
• Wetting from the vagian is common
• Clitoris stimulanion by contact also increases

G Spot

• Area on the anterior wall that is connected to the cervix which is deep/pressure sensitive

Male Arousal

• Hardening occurs from stimulant touch
• The blood vessels inflate during the hardening of the penis
• Men as well are not often affected by reflexes and have difficulty at times