D312 ANATOMY AND PHYSIOLOGY I - Set 4 - Part 1

Correct Answer: Gastrocnemius and soleus

Option c is correct because the autonomic nervous system controls involuntary functions including heart rate, blood pressure, digestion, and other visceral organ activities through sympathetic and parasympathetic pathways. Option a is incorrect because the somatic nervous system handles voluntary motor output to skeletal muscles and receives sensory input from the body surface, not visceral organ regulation. Option b is incorrect because the enteric nervous system specifically innervates the gastrointestinal tract using chemoreceptors and stretch receptors, and does not broadly regulate heart rate or blood pressure. Option d is incorrect because the central nervous system processes and integrates information within the brain and spinal cord but does not directly regulate organs without peripheral pathways.

Correct Answer: Sympathetic nervous system

Option a is correct because the sympathetic nervous system activates the fight-or-flight response, increasing breathing rate, dilating pupils, and diverting energy away from digestion during emergencies. Option b is incorrect because the parasympathetic nervous system promotes rest-and-digest functions, which would slow heart rate and stimulate digestion rather than suppress these calming activities. Option c is incorrect because the enteric nervous system specifically controls peristalsis and glandular secretions within the gastrointestinal tract and does not coordinate the broader emergency survival response. Option d is incorrect because the somatic nervous system manages voluntary skeletal muscle control and conscious sensory input, not the involuntary organ responses triggered during a sudden emergency.

Correct Answer: Enteric nervous system

Option d is correct because the enteric nervous system creates nerve plexuses innervating the gastrointestinal tract, using chemoreceptors and stretch receptors to independently control peristalsis and glandular secretions. Option a is incorrect because the sympathetic nervous system broadly activates fight-or-flight responses across multiple organ systems and does not form dedicated plexuses within the intestinal wall. Option b is incorrect because the somatic nervous system receives sensory input from body surfaces and limbs and sends motor output to skeletal muscles, not smooth muscle in digestive organs. Option c is incorrect because while the parasympathetic system can influence digestion, the dedicated nerve plexuses within the intestinal wall specifically belong to the enteric nervous system division.

Correct Answer: Central and peripheral nervous systems

Option b is correct because the central nervous system contains the brain and spinal cord, while the peripheral nervous system handles sensory input and motor output throughout the rest of the body. Option a is incorrect because the sympathetic and parasympathetic divisions are both subdivisions within the autonomic nervous system of the peripheral nervous system, not the two major structural divisions. Option c is incorrect because the somatic and autonomic systems are functional divisions within the peripheral nervous system and do not include the brain and spinal cord as a separate unit. Option d is incorrect because afferent and efferent describe the directional pathways of nerve signals rather than the two main structural divisions of the entire nervous system.

Correct Answer: Sensation, integration, response

Option a is correct because the nervous system first detects stimuli through sensation, then processes and interprets the information through integration, and finally activates effector organs through the response function. Option b is incorrect because integration cannot occur first since the brain must receive sensory input before it can process and interpret any information about the stimulus that was detected. Option c is incorrect because a response cannot precede sensation since the body must first detect a stimulus before any withdrawal action or effector activation can logically occur. Option d is incorrect because the response cannot come before integration since the brain must first process and interpret the sensory information before sending a motor command to pull away.

Correct Answer: Meninges

Option c is correct because the meninges are three protective membrane layers surrounding the brain and spinal cord, consisting of the dura mater, arachnoid mater, and pia mater. Option a is incorrect because the choroid plexus is a specialized structure responsible for producing cerebrospinal fluid within the ventricles, not a group of protective membrane layers around the brain. Option b is incorrect because cerebrospinal fluid is a liquid shock absorber contributing to the blood-brain barrier, not a term describing the physical membrane layers that protect the central nervous system. Option d is incorrect because the epineurium is a fibrous connective tissue layer covering the outer surface of peripheral nerves, not a membrane protecting the brain and spinal cord structures.

Correct Answer: Pia mater

Option d is correct because the pia mater is the innermost thin fibrous tissue layer of the meninges, permeable to water and small solutes, allowing blood vessels to pass through and nourish the brain. Option a is incorrect because the arachnoid mater is the middle meningeal layer, described as a thin transparent membrane forming a loosely fitting sac around the brain, not the innermost layer. Option b is incorrect because the dura mater is the outermost and toughest meningeal layer providing durable protection, not the delicate innermost membrane allowing vascular nourishment of brain tissue. Option c is incorrect because the epineurium is a fibrous connective tissue covering peripheral nerves in the peripheral nervous system and is not one of the three meningeal membrane layers.

Correct Answer: Cauda equina

Option a is correct because the cauda equina is a bundle of lumbar, sacral, and coccygeal nerve roots below the conus medullaris that resembles a horse's tail in its appearance. Option b is incorrect because the conus medullaris is the tapered lower end of the spinal cord itself near lumbar vertebral level one, not the bundle of nerve roots extending below it. Option c is incorrect because the filum terminale is an extension of the pia mater attached to the coccygeal segments providing structural anchoring, not the collection of nerve roots below the cord. Option d is incorrect because the foramen magnum is the opening at the base of the skull through which the spinal cord enters and exits, not a structure found in the lumbar region.

Correct Answer: Sensory fibers enter via posterior roots

Option b is correct because sensory afferent fibers enter the spinal cord through the posterior dorsal nerve roots, carrying information from receptors toward the central nervous system for processing. Option a is incorrect because motor efferent fibers exit the spinal cord through the anterior ventral roots carrying commands to effector organs, and dorsal roots are the entry point for sensory information. Option c is incorrect because sensory fibers carry information inward toward the central nervous system through posterior roots and do not exit through anterior roots like motor neurons do. Option d is incorrect because motor efferent fibers exit through the anterior ventral roots to reach muscles and glands, and posterior dorsal roots are exclusively the entry pathway for sensory information.

Correct Answer: Choroid plexus

Option c is correct because the choroid plexus is the specialized structure that produces cerebrospinal fluid, which acts as a shock absorber and contributes to the blood-brain barrier protecting brain tissue. Option a is incorrect because the pia mater is the innermost meningeal membrane that allows blood vessels to nourish the brain but does not produce cerebrospinal fluid within the ventricles. Option b is incorrect because the dura mater is the tough outermost meningeal layer providing physical protection to the central nervous system, not the structure responsible for producing cerebrospinal fluid. Option d is incorrect because the arachnoid mater is the thin transparent middle meningeal membrane forming a loosely fitting sac and does not produce cerebrospinal fluid in the ventricles.

Correct Answer: Axon

Option d is correct because the axon is the elongated neuronal structure that transmits nerve impulses away from the cell body toward other neurons, muscles, or glands at the synaptic terminal. Option a is incorrect because dendrites are the branching extensions of a neuron that receive incoming signals and conduct them toward the cell body, not away from it to target cells. Option b is incorrect because the synapse is the specialized junction or gap between two neurons where information transfer occurs, not a structural part of a single neuron that transmits impulses. Option c is incorrect because the soma is the cell body of the neuron that houses the nucleus and organelles, serving as the metabolic center rather than the structure transmitting impulses outward.

Correct Answer: Interneuron

Option a is correct because interneurons are located within the central nervous system and serve as the bridge between sensory afferent neurons and motor efferent neurons in neural pathways like reflex arcs. Option b is incorrect because efferent neurons are the motor neurons that relay impulses away from the central nervous system to effector organs like muscles, not the bridging neurons within the cord. Option c is incorrect because afferent neurons are sensory neurons that transmit information from receptors toward the central nervous system, not the neurons that bridge sensory and motor pathways. Option d is incorrect because satellite cells are a type of neuroglia found in the peripheral nervous system that provide structural support to neuron cell bodies, not signal bridging functions.

Correct Answer: Oligodendrocytes

Option c is correct because oligodendrocytes are the glial cells located in the central nervous system responsible for producing the myelin sheath that insulates axons within the brain and spinal cord. Option a is incorrect because Schwann cells are the myelinating glial cells of the peripheral nervous system and perform the same insulating function but only for axons outside the brain and spinal cord. Option b is incorrect because satellite cells are peripheral nervous system glial cells that provide structural support to neuron cell bodies in ganglia, not insulation or myelination of central nervous system axons. Option d is incorrect because astrocytes are central nervous system glial cells that provide structural support to neurons but do not produce the myelin sheath that insulates axons within the brain.

Correct Answer: Microglia

Option b is correct because microglia are the specialized glial cells of the central nervous system that perform immune surveillance and phagocytosis, engulfing and destroying pathogens and cellular debris within the brain. Option a is incorrect because ependymal cells are glial cells responsible for creating cerebrospinal fluid within the ventricles of the brain, not performing immune defense or phagocytosis of pathogens. Option c is incorrect because astrocytes are central nervous system glial cells that provide structural support to neurons and contribute to the blood-brain barrier, not immune surveillance and pathogen destruction. Option d is incorrect because oligodendrocytes are central nervous system glial cells that produce the myelin sheath for insulation of axons, not immune surveillance or phagocytic defense against infections.

Correct Answer: Endoneurium, perineurium, epineurium

Option d is correct because endoneurium wraps individual axons as the innermost layer, perineurium surrounds fascicles as the middle layer, and epineurium covers the entire nerve as the outermost fibrous layer. Option a is incorrect because this sequence places perineurium as the innermost layer, but perineurium wraps around fascicles which are bundles of axons, making it the middle connective tissue layer instead. Option b is incorrect because this sequence reverses the correct order entirely by placing the outermost layer first, when epineurium is the fibrous covering on the outer surface of the whole nerve. Option c is incorrect because while endoneurium is correctly placed as innermost, this sequence incorrectly positions epineurium as the middle layer when it is actually the outermost covering of the nerve.

Correct Answer: Water-soluble hormones

Option a is correct because water-soluble hormones cannot cross the lipid cell membrane, so they must bind surface receptors and rely on second messenger systems to relay signals inside the cell. Option b is incorrect because lipid-soluble hormones dissolve in fats and pass directly through the cell membrane to bind intracellular receptors, allowing them to change gene expression without second messengers. Option c is incorrect because cholesterol-based hormones are a type of lipid-soluble hormone that can cross the cell membrane and bind receptors inside the cell without needing a relay system. Option d is incorrect because intracellular hormones is not a recognized classification in hormone signaling, and all hormones originate outside their target cells before binding to specific receptor proteins.

Correct Answer: It requires transport proteins in blood

Option d is correct because lipid-soluble hormones often require transport proteins to travel through the aqueous blood, and they pass through cell membranes to directly bind intracellular receptors and alter gene expression. Option a is incorrect because binding to plasma membrane receptors is a characteristic of water-soluble hormones, which cannot cross the cell membrane and must use surface receptor signaling pathways. Option b is incorrect because relying on second messenger systems is a hallmark of water-soluble hormones that cannot enter the cell and must relay their signal through intracellular messenger molecules. Option c is incorrect because signal transduction through the cytosol between the membrane and nucleus is the mechanism used by water-soluble hormones, not the direct intracellular receptor binding of lipid-soluble hormones.

Correct Answer: Hormones

Option c is correct because hormones are chemical messengers secreted by glands that travel through the bloodstream to selectively affect target cells carrying specific receptors designed for that particular hormone. Option a is incorrect because enzymes are protein catalysts that accelerate cellular chemical reactions within the body and do not travel through the bloodstream to selectively bind receptors on distant target cells. Option b is incorrect because a primer is a molecule required for the formation of another molecule in biological processes and does not describe chemical messengers traveling through blood to target cells. Option d is incorrect because an antagonist is a substance that blocks agonist binding at hormone receptors to prevent the expected response, not a chemical messenger that activates target cells through bloodstream delivery.

Correct Answer: Permissive hormone

Option d is correct because a secondary or permissive hormone promotes and enhances the effect of another primary hormone at target tissue without directly causing the physiological effect by itself. Option a is incorrect because an antagonist hormone blocks agonist binding at hormone receptors and prevents the expected physiological response, which is the opposite of enhancing or supporting another hormone. Option b is incorrect because a primer is a molecule required for the formation of another molecule in biochemical pathways and does not describe a hormone that enhances the effectiveness of other hormones. Option c is incorrect because an enzyme is a protein catalyst that accelerates cellular chemical reactions and does not describe a hormone that supports or promotes the physiological effect of another hormone.

Correct Answer: Endocrine glands

Option a is correct because endocrine glands are ductless glands that secrete hormones directly into the bloodstream, allowing chemical messengers to travel to distant target cells throughout the entire body. Option b is incorrect because exocrine glands secrete substances onto body surfaces or into body cavities through ducts, which is the defining characteristic that distinguishes them from ductless endocrine glands. Option c is incorrect because sweat glands are a specific example of exocrine glands that use ducts to secrete sweat onto the skin surface for thermoregulation, making them ducted rather than ductless. Option d is incorrect because salivary glands are another example of exocrine glands that use ducts to deliver saliva into the oral cavity, and they do not release hormones directly into the bloodstream.