a “textbook” view of sexual-behavior anatomy. the nervous system nervous system responsible for...

A “Textbook” View ofSexual-Behavior Anatomy

The Nervous System

• nervous system responsible for communication – between us and environment– among regions of the body

• coordinates and integrates information

• regulates activity; maintains homeostasis

• memory & consciousness

• Nervous system has unique organization– functional and structural

• Functional Organization

CENTRAL NERVOUSSYSTEM

PERIPHERAL NERVOUSSYSTEM

• brain• spinal cord

• cranial nerves• spinal nerves

integration & control communication (signaling)

A nerve cellshowingdendrites andan incomingaxon.

D

A

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Histology slideillustratingthe physicallayout of somenerves.

Cognitive area

Limbic System of the Brain

The limbic system is responsible for generating our emotional feelings (pleasure, frustration, anger) based on our cognitive interpretation of our environment

Our sensory nerves inform our brain about our physical environment

• Sensory Areas– sensory association

cortex• posterior to primary• integrate inputs• sensory memory

– visual cortex• occipital lobe• maps visual space• association area

interprets

– auditory• temporal lobe• hearing• sound perception

– olfactory• frontal above orbit

Pain vs. Pleasure

Sensory areas of the brain receive input from nerve fibers which originate from different types of receptors (touch, visual, auditory, pain, taste).

Sensory nerves originating from Pacinian corpuscles in the skin (mechanoreceptors) respond to touch.

A-delta nerves originating from free nerve endings (Noci receptors) respond to tissue damage.

Primary (SI) and secondary (SII) sensory cortex involved with the localization of pain

Anterior portion of insular is most likely concerned with pain perception

Reflexes• Independent level of neural integration

– acts without brain control

– rapid predictable motor response

• components

– receptor

– sensory neuron

– integration center:

• monosynaptic, polysynaptic

• motor neuron

– effector

All sensory information is relayed throughout different parts of the brain and our conscious interpretation of the stimuli generates an emotional response which we “feel”.

Our CNS response to stimuli also includes (selective) changes in the (autonomic) sympathetic and parasympathetic nerve pathways; selective changes based on our interpretation of the stimuli.

Neurotransmitter secretions In ANS

Sympathetic N.S.

Fight or Flight Reflexes - increase BP, metabolism, CNS activity

Regulate autonomic functions

Parasympathetic N.S.

• craniosacral motor nerves– synapse in wall of

organ

• vegetative functions– internal housekeeping,

recovery, rest G.I. activity• digestive organs

– inhibit brain & muscle

Learning and memory play a very important role in how we respond to specific stimuli

Memory

A “memory” is not a discrete location in the brain made up of a cluster of cells which are independent of other cells.

A “memory” is actually comprised of a “pattern” of nerve-cell activities made up of interconnected nerve cells which are scattered throughout the cerebral cortex. These cells are in turn interconnected to all other brain cells.

Memory/Learning

We do not remember facts as discrete pieces of independent information.

We have memories of “facts” only in association with other memories.

We develop new memories only in association with existing memories.

Memory/Learning

New memories are created by rearranging existing patterns of activated nerve cells into new patterns of activity.

This process demands synthesis of new proteins in “some” nerve cells to modify their ability to be activated by other nerves and thereby create a new patterns of activation.

Learning

Parts of the brainthat are importantfor learning.

Learning

Hippocampus coordinatesenvironmental stimuliand activates existingmemory.

Learning

New memory is constructedbased on novel stimulus incomparison to existingmemory.

“Strength” of the memory isdependent on the frequencyand strength of the neural activity.

Learning

The new memory isactivated either throughthe “novel” stimulus orthrough the associatedmemory.

Memory

We remember facts as pieces of “information” in relation to other pieces of “information” which in turn are related to other …

The most basic connection between behavior and memory is that we desire to perform behaviors which produce responses that we want….if we can’t remember that a particular behavior resulted in a desirable outcome, there is little chance we will seek out to repeat the same behavior.

In addition, if a particular behavior results in an unpleasant experience, there is a strong likelihood that we will avoid that behavior.

On the other hand, if a behavior is not particularly pleasant, but does result in a highly desirable outcome, there is a high likelihood that the unpleasant behavior will be continued in order to get the pleasant payoff.

Memory / Learning / Behavior

There is no doubt that sexual activities can be pleasurable; but they are still part of a learned behavior. One has to learn that specific physical touch sensations (or even just thoughts of sexual activities) are associated with the future pleasure (well… very near future) of sexual activity before they can lead to the reflexive parasympathetic responses that lead to arousal.

Very young children commonly get aroused as a result of random physical events but do not recognize the feelings as sexual arousal. (What parent hasn’t seen a male baby with an erection when changing their diaper?) We not only have to learn that these events are sexual in nature but also have to remember these facts of association to control these arousal reflexes. (Erections in “inappropriate” places and times in young adolescents are common and it is only through the negative personal and social responses to these erections that they learn to associate negative feelings with “inappropriate” erections and because of the negative feelings the parasympathetic reflexes are shut down to inactivate an “inappropriate” erection; thus developing control)

One learns that there are specific environments where arousal is appropriate and in these specific environments one learns to allow the reflexes to occur and with continual appropriate thoughts and actions these reflexive responses can continue through to the additional sympathetic reflexes to produce orgasm.

Note the “continual appropriate thoughts and actions”… in many cases all it takes is a loud phone, or a crying child, or a barking dog “jumping into the fray” to derail the process and remind us that these are purely CNS reflexes that we have learned to control and if the appropriate environment suddenly changes, our thoughts change and the desirable responses almost immediately shut down…