Handout 6



Handout 6

Sexually dimorphic behaviors:

Definition: Anatomical, physiological, and behavioral differences between males and females of the

same species

Is sexual identity learned?

Story: Bruce ( Brenda ( David

What does it show demonstrate? The possibility that biology is more important than sociology

Chromosomal identity

- Typically, males have XY sex chromosomes, females have XX but hormone activity is what ultimately determines gender!

- A person’s genetic sex is determined by the father.

-Y chromosome dictates:

1. SRY gene on the Y chromosome dictates the development of the fetal testis (testis-determining factor) and triggers action of receptors to receive message of hormones

2. Control the development of glands that produce male sex hormones

- Default sex is female

Three categories of sex organs (primary sex characteristics)

1. Gonads

-Can become either testes or ovaries

-If there is SRY, gonads will become testes

-Absence of SRY, gonads will by default, become ovaries

-Critical period of development: Gestational 7-12 weeks

2. Internal sex organs

-Precursors:

Mullerian system ( female

- eventually become uterus, fallopian tubes, upper part of vagina

Wolffian system ( male

- eventually become epididymis

Important! All embryos contain the precursors for BOTH female and male sex organs

|If TDF is NOT present ( female |If TDF IS present ( male |

|a. Ovaries differentiate |a. Testes differentiate producing androgens which have a masculinizing effect |

|b. Mullerian system develops, Wolffian regresses |b. Testes also produce anti-Mullerian hormone (defeminizing effect) which |

|c. Female genitalia develop |inhibits the development of the Mullerian system. |

3. External Sex Organs

|Female |Male |

|-Labia, clitoris, and outer vagina |-Penis and scrotum |

Sexual Development Dysfunctions

a. Androgen insensitivity syndrome

- People with this syndrome have no androgen receptors

- Testes STILL produce androgens and Anti-Muellerian Hormone

- Results:

- Gonads become testes, defeminization (Muellerian system inhibited)

- Lack of masculinization = epididymis, vas deferens, seminal vesicles, and prostate do not

develop

b. Persistent Mullerian duct syndrome

- Failure to produce anti-Mullerian hormone

- Absence of receptors for this hormone

- Results:

- Defeminization does NOT occur but masculinization DOES

- Person is born with both sets of internal sex organs

c. Turner’s syndrome

- Fetus only has one sex chromosome: X

- Results:

- Will develop internally and externally as female

- But! Will be infertile because need XX to produce eggs

Puberty (development of secondary sex characteristics)

Process:

a. Hypothalamus begins to secrete gonadotropin-releasing hormones (GnRH)

b. Causes the pituitary to release Follicle-stimulating hormone (FSH) and Lutenizing hormone (LH)

c. MALES: These hormones stimulate TESTES to produce sperms and testosterone

FEMALES: These hormones stimulate the ovaries to produce estradiol (estrogens)

What else can affect puberty?

- Nutrition (dysregulation of a chemical, leptin, triggers hormone release)

Secondary sex characteristics:

- In FEMALES:

- Effects of estradiol: enlarged breasts, growth of lining of uterus, widened hips, maturation of genitalia, beginnings of menstrual cycle (just know general events)

- Effects of androgens: underarm, pubic, facial hair

- In MALES:

- Effects of estradiol: enlarged breasts

- Effects of androgens: hair growth, deepening of voice, altered hairline, muscle development, maturation of genitalia

Sexual behavior

- Hormones have organizational effects on sexual behavior by altering the development of brain

- In female mammals (EXCEPT for higher primates)

- hormones and pheromones control willingness and ability to mate

|HUMAN females |HUMAN males |

|- Effect of hormones: may affect sexual interest, for example sexual activity |- Level of hormones DIRECTLY affects sexual behavior of human males (like male |

|peaks during ovulation when estradiol levels are highest. |mammals) |

|- Other factors are important: emotions, desire to get pregnant, cognition, | |

|learning. More higher level control | |

Neural control

|Female |Male |

|- Ventro-medial hypothalamus (VMH) |- Erection and ejaculation = controlled by spinal reflex |

|- Medial amygdala |- spinal nucleus of the bulbocavernosus (SNB) controls muscle attached to penis, |

|- Periaqueductal gray matter (PAG) |directly responsive to testosterone |

|- Nucleus paragigantocellularis (PGi) in the medulla |- Medial preoptic area (MPA) |

| |- Medial amygdala |

| |- Bed nucleus of the stria terminalis (BNST) |

| |- Periaqueductal gray (PAG) |

| |- Nucleus paragigantocellularis (PGi) in the medulla |

Sexual Orientation

- Biological events appear to play a role in determining sexual orientation

- Evidence: LeVay found evidence of a structure in the hypothalamus (MPA) that is smaller in women and in homosexual males than in heterosexual males.

- Environmental role not ruled out

Sex differences in cognitive function

|Female superiority: |Male superiority: |

|- tests that emphasize: perceptual, psychomotor abilities, face recognition, |- tests that emphasize visual-spatial functions, mental rotation, navigation, |

|object memory, object location memory, language and processing speed |targeting, mechanical reasoning, and math |

|- In object tracking experiments, better at naming the ball’s color |- In object tracking experiments, better at both egocentric and allocentric tasks|

Anatomical differences

|Females: |Males: |

|Less hemispheric lateralization |More lateralization of functions |

|Circuitry important |Tissue volume important |

Emotions

Definition: responses of the whole organism involving

a) physiological arousal (autonomic/hormonal)

b) expressive behaviors (behavioral)

c) conscious experience (cognitive)

Evolutionary advantage to emotion

- Emotions are an important component of rational thinking!

Example: fight or flight response

Biological purpose?

- Emotions signal actions we might need to take, provide a strong impulse to take action, promote patterns of physiological change and behavior

Psychological reasons for emotions?

- Catharsis

- belief that emotions are needed to release energy (such as aggression)

- Feel-good, do-good phenomenon

- people tend to be helpful when already in a good mood

- Subjective state of well-being

Classes of emotions

|Negative: motivation for moving away from what you don’t want |Positive: motivation drawing you toward something |

|Examples: fear, anger, grief, hate |Examples: love, empathy, caring, joy |

Universal emotions

- Definition: emotions that presumably experienced by all people regardless of culture

- 6 universal emotions: joy, surprise, sadness, anger, disgust, fear

Physical arousal is controlled by Autonomic nervous system (sympathetic and parasympathetic systems)

Theories of Emotion

|James Lange Theory |Cannon-Bard Theory |Schacter-Singer Theory |

|- Experience of emotion is awareness of physiological |- Emotion-arousing stimuli stimulatenously trigger |- To experience emotion one must both be physically |

|responses to emotion-arousing stimuli |physiological response and the subjective experience |aroused and cognitively label the arousal |

|- i.e. Our subjective “feelings” are an interpretation|of emotion |- i.e. physiology determines how strong emotion is, |

|we make of our body’s reaction to stimuli |- i.e. once we perceive threat, visceral and |but ID’ing emotion depends on a cognitive appraisal of|

| |subjective experience of emotion is simultaneous |situation |

Arousal and performance

Their relationship: Performance peaks at lower levels of arousal for difficult tasks, and at higher levels for easy or well-learned tasks

Neurobiology

General comments:

- In general, most structures are near the middle of the brain (for protection)

- Sensory information can go directly to amygdala (structure important for emotional processing) without being fully processed

|Structure |Location |Function |

|Hypothalamus |- Base of the fore brain |- Integration of emotional response from forebrain, brainstem, spinal cord |

| |- Behind the optic chiasm |- Sexual response |

| |- Forms part of the walls of the 3rd |- Endocrine responses |

| |ventricle |(How do we know this? Ablation studies: cats without hemispheres and hypothalamus |

| |- Contiguous with infundibular stalk to |did not show rage. Stimulation studies: stimulated lateral hypothalamic stimulation,|

| |pituitary |cats showed rage/attack) |

| | |- Routes of information: |

| | |Input from: cortex |

| | |Output to Reticular formation |

|Reticular formation |In brainstem |- Controls sleep-wake rhythm, arousal, and attention |

| | |- Relay center between brain and autonomic nervous system |

|Limbic System |- Extends from cingulate gyrus to |- Integrates information from cortical association areas |

| |parahippocampal gyrus and encircles the upper|(How do we know this? Kluver-Bucy Syndrome: behavior changed after removing parts of|

| |brain stem |the limbic system) |

| |Includes many structures including the | |

| |amygdala, hippocampus, mammillary bodies, | |

| |cingulate gyrus, circuit of papez | |

|Amygdala |-Front of hippocampus |- Connects to: olfactory bulb, cortex, brainstem, hypothalamus, cortical sensory |

| |-Almond shaped |association areas (basically everywhere) |

| | |- Learned emotions: for example fear conditioning. Normal rat, can condition them to|

| | |fear a stimulus. Lesion amygdala and you get rid of fear response ability |

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