Lecture 11: Sensory III and The Endocrine System

Vocabulary practice flashcards covering the animal olfactory system, cranial nerve classifications, principles of the endocrine system, hormone secretion dynamics, feedback loops, pituitary-hypothalamic interactions, and oxytocin-mediated neuroendocrine reflexes.

Olfactory Receptor Neurons

Specialized sensory neurons located within the olfactory epithelium of the nasal cavity that act as chemoreceptors, with distinct receptor types dedicated to specific odor molecules.

Olfactory Glomeruli

Spherical clusters or ball-like structures in the olfactory bulb that function as smell collection centers where olfactory receptor axons for a specific odor molecule collectively synapse onto mitral cells.

Mitral Cells

Second-order neurons in the olfactory bulb that receive synaptic input from olfactory receptor neurons within glomeruli and relay olfactory signals directly to the limbic system and temporal lobe of the brain.

Cribriform Plate

The porous, sieve-like horizontal segment of the ethmoid bone that allows passage of olfactory nerve fiber bundles from the nasal cavity into the olfactory bulb.

Vomeronasal Organ (Jacobson's Organ)

An auxiliary olfactory organ found in mammals and reptiles that possesses chemoreceptors for detecting pheromones and sends action potentials to the hypothalamus to modulate reproductive and social behaviors.

Flehmen Response

A characteristic behavioral response in animals involving the exaggerated curling of the upper lip and opening or flaring of the nasal passages to facilitate the uptake of pheromones into the vomeronasal organ.

Endocrine System

A communication network of glands and tissues that secretes chemical messengers (hormones) directly into the blood to regulate metabolism, reproduction, and general physiology at a slower rate than the nervous system.

Endocrinology

The biological study of hormones, the specific endocrine tissues that secrete them, and their physiological actions throughout the animal body.

Arnold Berthold's Experiment (1849)

The foundational endocrine study in which reimplanting or transplanting a testis into the abdominal cavity of a castrated rooster prevented the loss of male physical traits and behaviors, proving testes act via a blood-borne substance.

Episodic Hormone Secretion

A secretion pattern characterized by hormone release occurring in distinct, intermittent pulses or bursts over time.

Basal Hormone Secretion

A secretion profile where a hormone is continuously released at a low, steady baseline concentration in the bloodstream.

Sustained Hormone Secretion

A secretory mode marked by elevated and continuous release of a hormone into circulation over an extended duration.

Hormone Half-Life

The time required for 50% of a hormone's circulating concentration to be degraded and cleared from the blood, primarily accomplished by metabolic processes in the liver, kidneys, or lungs.

Endocrine Axis

A coordinated regulatory feedback system typically involving multiple endocrine components, such as the hypothalamus, the pituitary gland, and a downstream target gland.

Negative Feedback

The primary homeostatic regulatory mechanism in endocrinology, wherein a secreted hormone or downstream response acts upstream to inhibit and reduce its own production.

Positive Feedback

A less common, typically short-lived regulatory process in which a hormone or physiological change stimulates its own increased production to accomplish a rapid or dramatic physiological shift.

Anterior Pituitary (Adenohypophysis)

The glandular anterior lobe of the pituitary gland consisting of glandular cells (such as the pars distalis and pars intermedia) controlled by hypothalamic releasing hormones delivered through the hypophyseal portal bloodstream.

Posterior Pituitary (Neurohypophysis)

The neural lobe of the pituitary gland (pars nervosa) connected via unmyelinated axons directly to hypothalamic neurosecretory neurons, storing and releasing hormones such as oxytocin directly into circulation.

Hypothalamic Nuclei

Clusters of specialized neurosecretory cell bodies within the hypothalamus (such as the paraventricular and supraoptic nuclei) that process inputs and secrete neuroendocrine hormones directed toward the pituitary gland.

Neuroendocrine Reflex

A physiological reflex arc where sensory nerve stimulation initiates afferent neural signals to the central nervous system, prompting the release of a hormone into the blood that subsequently produces an effect on target tissues.

Oxytocin

A peptide neurohormone synthesized primarily by the paraventricular and supraoptic nuclei of the hypothalamus and secreted by the posterior pituitary to stimulate uterine smooth muscle contraction and milk ejection.

Ferguson Reflex

A neuroendocrine positive-feedback reflex where pressure of the fetus against the maternal cervix stimulates sensory afferents to the hypothalamus, causing posterior pituitary oxytocin release and progressive uterine contractions until birth.

Milk Let-Down Reflex

A neuroendocrine reflex initiated by suckling stimuli from nursing offspring, triggering sensory signals to the hypothalamus that prompt posterior pituitary oxytocin secretion and subsequent alveolar milk ejection.

Pitocin

A synthetic pharmaceutical preparation of oxytocin routinely administered clinically to induce labor, stimulate uterine contractions during parturition, or manage postpartum hemorrhage.

Cranial Nerve I (Olfactory Nerve)

A sensory cranial nerve arising from the olfactory bulb that supplies the nasal mucosa to mediate the sense of smell (olfaction).

Cranial Nerve II (Optic Nerve)

A sensory cranial nerve originating from the diencephalon that innervates the retina to transmit visual information.

Cranial Nerve III (Oculomotor Nerve)

A motor cranial nerve arising from the midbrain providing somatic motor innervation to extraocular eye muscles as well as parasympathetic fibers to the iris sphincter and ciliary muscles.

Cranial Nerve IV (Trochlear Nerve)

A motor cranial nerve arising from the midbrain that specifically innervates the dorsal oblique muscle of the eye.

Cranial Nerve V (Trigeminal Nerve)

A mixed cranial nerve emerging from the pons that divides into ophthalmic (sensory to eye/dorsal head), maxillary (sensory to upper head/palate/teeth), and mandibular (sensory to lower jaw/tongue; motor to muscles of mastication) divisions.

Cranial Nerve VI (Abducens Nerve)

A motor cranial nerve originating from the medulla that innervates the lateral rectus and retractor bulbi muscles of the eye.

Cranial Nerve VII (Facial Nerve)

A mixed cranial nerve emerging from the medulla responsible for taste sensation on the rostral two-thirds of the tongue, parasympathetic secretomotor supply to salivary and lacrimal glands, and motor control of muscles of facial expression.

Cranial Nerve VIII (Vestibulocochlear Nerve)

A sensory cranial nerve arising from the medulla comprising a cochlear division for hearing and a vestibular division for detecting acceleration, balance, and equilibrium.

Cranial Nerve IX (Glossopharyngeal Nerve)

A mixed cranial nerve emerging from the medulla providing taste to the caudal third of the tongue, parasympathetic fibers to salivary glands, and motor innervation to pharyngeal muscles.

Cranial Nerve X (Vagus Nerve)

A mixed cranial nerve arising from the medulla conveying sensory innervation from pharyngeal/laryngeal mucosa and viscera, parasympathetic control to thoracic and abdominal organs, and motor innervation to pharyngeal and laryngeal muscles.

Cranial Nerve XI (Accessory Nerve)

A motor cranial nerve arising from the medulla and cervical spinal cord that provides somatic motor innervation to neck and shoulder musculature, including the trapezius muscle.

Cranial Nerve XII (Hypoglossal Nerve)

A motor cranial nerve emerging from the medulla that innervates and coordinates the intrinsic and extrinsic muscles of the tongue.