The Nervous System
This basic structural and functional cell of the nervous system influences thinking, affects memory, and regulates organs.
What is a neuron?
Injury to this lowermost part of the brainstem can be instantly fatal because it houses cardiac, vasomotor, and respiratory vital centers.
What is the medulla oblongata?
Endocrine glands are classified as ductless because they secrete regulatory hormones directly into this system.
What is the bloodstream?
These two hormones, secreted by alpha and beta cells in the pancreatic Islets of Langerhans, directly raise and lower blood sugar.
What are glucagon and insulin?
This tough, white, fibrous outer layer of the eyeball protects internal structures and maintains eyeball shape.
What is the sclera?
These star-shaped neuroglial cells supply nutrients to neurons and form part of the protective blood–brain barrier in the CNS.
What are astrocytes?
Located specifically in the left frontal lobe, Broca’s area is responsible for controlling this function.
What is motor speech?
Steroid hormones are lipid-soluble compounds synthesized from this lipid precursor.
What is cholesterol?
A lack of dietary iodine can prevent normal thyroid hormone synthesis and lead to this enlarged thyroid condition.
What is a goiter?
Listed from the eardrum inward, these three tiny auditory ossicles transmit sound vibrations through the middle ear.
What are the malleus, incus, and stapes?
Within a peripheral nerve, axon extensions are organized and bundled together into these distinct groups.
What are fascicles?
The spinal cord extends downward from the medulla oblongata to the approximate level of these vertebrae.
What are the 1st or 2nd lumbar vertebrae (L1–L2)?
Attached to the pituitary gland by the infundibular stalk, this tiny brain area serves as the major link between the nervous and endocrine systems.
What is the hypothalamus?
Produced by the pineal gland, this antioxidant hormone plays a central role in maintaining the body's sleep–wake cycle.
What is melatonin?
Located inside the snail-shaped cochlea of the inner ear, this structure is known as the true organ of hearing.
What is the Organ of Corti?
This division of the autonomic nervous system prepares the body for extreme stress or emergency by producing a "fight-or-flight" response.
What is the sympathetic division?
Following head trauma, fluid leaking from the nose or ears that tests positive for glucose indicates a leak of this substance.
What is cerebrospinal fluid (CSF)?
The pituitary gland (hypophysis) is housed and protected within this depression of the sphenoid bone.
What is the sella turcica?
Secreted by the adrenal cortex, this mineralocorticoid promotes sodium reabsorption in the kidneys to regulate electrolyte balance.
What is aldosterone?
This clinical term refers to a high-pitched buzzing or ringing sound in the ears.
What is tinnitus?
If this part of a nerve cell is completely destroyed, the neuron is lost forever and cannot regenerate.
What is the cell body?
These three cranial nerves innervate the extraocular muscles to assist with voluntary eye movements.
What are CN III (Oculomotor), CN IV (Trochlear), and CN VI (Abducens)?
This primary homeostatic mechanism signals a gland to halt hormone secretion once a target response reaches its desired effect.
What is negative feedback?
When oxygen levels are low, the kidneys secrete this hormone to stimulate red blood cell production in the bone marrow.
What is erythropoietin (EPO)?
Caused by irregularities in the curvature of the cornea or lens, this visual defect prevents horizontal and vertical lines from focusing simultaneously.
What is astigmatism?