Most Important Coordination and Control MCQs with Answers

Nervous coordination is defined as the system of the body that provides coordination through electric signals among different body parts for the response to a particular stimulus.

Receptors act as transducers because they convert one form of energy, such as light energy from a stimulus, into another form, specifically electrochemical energy in the form of a nerve impulse.

An example of a receptor acting as a transducer is found in the retina of the eye, where rod and cone cells convert light energy into nerve impulses (electrochemical energy).

Muscles and glands are identified as the effectors, which carry out the response to a stimulus after receiving commands from the nervous system.

Neurons are explicitly stated as the basic structural and functional unit of the nervous system.

While a myelin sheath may cover some axons, the three basic components found in all neurons are the cell body, dendrites, and an axon.

The function of the dendrite is to receive stimuli and conduct impulses to the cell body.

Axons functionally conduct action potentials from the neuron cell body to the presynaptic terminals, meaning they conduct signals away from the cell body.

Schwann cells are covered by a fatty substance called myelin sheath that acts as an insulator, making these axons myelinated fibers.

A non-myelinated part of an axon between two Schwann cells is called a node of Ranvier.

Sensory neurons are responsible for conducting impulses towards the central nervous system from the sensory receptors.

Interneurons occur entirely within the CNS and convey messages between various parts of the CNS.

Motor neurons conduct impulses away from the central nervous system, and their terminal branches are connected to an effector.

The myelinated axons transmit information much faster than other neurons, and the velocity of nerve impulse is faster in myelinated neuron fibers due to saltatory conduction.

Saltatory conduction is the rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelinated regions of membrane.

Thick neuron fibers conduct faster impulses than thin fibers because resistance to electrical current flow is inversely proportional to the cross-sectional area of the conductor, meaning increased thickness leads to decreased resistance.

The cytoplasm of the cell body is characterized by the presence of Nissl's granules, which are groups of ribosomes and rough ER associated with protein synthesis.

Multipolar neurons are characterized by having three or more processes, specifically several dendrites and one axon.

Schwann cells are neuroglial cells in the peripheral nervous system that support, protect, and nourish the neurons. They typically wrap around axon fibers and are covered by a myelin sheath.

A reflex action is defined as a rapid, involuntary, and unconscious response to a stimulus, occurring almost instantaneously.

In a reflex arc, the interneuron (also called associative neuron) acts as a link between the sensory neuron and the motor neuron, processing the signal within the CNS.

If the sensory neuron is damaged, the stimulus cannot be successfully received by the CNS and thus no reflex action will occur.

Motor neurons conduct impulses away from the central nervous system to the muscles or glands (effectors).

The withdrawal reflex is a classic example of a reflex arc involving all three types of neurons: sensory (detects heat), interneuron (processes in spinal cord), and motor (activates muscles to withdraw).

The cell body of a sensory neuron is generally located in the dorsal root ganglion, which is part of the Peripheral Nervous System, outside the CNS.

Effectors are the structures that respond to the nerve impulse, such as muscles contracting or glands secreting.

The knee-jerk reflex is a monosynaptic reflex, meaning it involves only one synapse between the sensory and motor neuron, without an interneuron.

The typical pathway of a reflex arc is: Receptor detects stimulus, Sensory neuron transmits to CNS, Interneuron processes (in CNS), Motor neuron transmits to effector, Effector produces response.

A nerve impulse is defined as an electrochemical change which travels along the length of a neuron.

When a neuron is at its resting potential, it is in a polarized state, meaning there is a difference in electrical charge across the membrane.

During the resting membrane potential, there is a higher concentration of potassium ions (K+) inside the cell compared to the outside.

The Na+/K+ pump actively transports 3 Na+ ions out of the cell and 2 K+ ions into the cell, which significantly contributes to maintaining the negative resting membrane potential.

The presence of negatively charged organic ions (proteins, amino acids) inside the cytoplasm, which cannot easily cross the membrane, contributes to the overall negative charge inside.

When a stimulus reaches the threshold level, voltage-gated Na+ channels open rapidly, causing Na+ ions to rush into the cell, leading to depolarization.

Depolarization is the phase during an action potential where the rapid influx of Na+ ions causes the inside of the membrane to become positive relative to the outside.

Repolarization occurs as voltage-gated K+ channels open, allowing K+ ions to rush out of the cell, making the inside of the membrane negative again.

Hyperpolarization is a brief period after repolarization where the membrane potential becomes even more negative than the resting potential, due to the slow closing of K+ channels.

A threshold stimulus is the minimum strength of a stimulus required to generate an action potential.

A sub-threshold stimulus is one that is too weak to reach the threshold potential and therefore does not generate an action potential.

The refractory period is a brief period immediately following an action potential during which the neuron is unable to generate another action potential, ensuring one-way propagation.

Saltatory conduction, which involves the action potential "jumping" between Nodes of Ranvier, occurs only in myelinated fibers, significantly increasing the speed of impulse transmission.

Larger diameter axons conduct impulses faster because their larger cross-sectional area offers less resistance to the flow of local currents, allowing depolarization to spread more rapidly.

The "All-or-None Law" states that if a stimulus reaches threshold, an action potential will occur with full strength, or it won't occur at all if the stimulus is sub-threshold. The magnitude of the action potential is independent of the stimulus strength once threshold is reached.

The opening of voltage-gated K+ channels and the subsequent efflux of K+ ions are primarily responsible for the repolarization phase, bringing the membrane potential back towards resting levels.

During depolarization, voltage-gated sodium channels open, causing a large influx of Na+ ions, making the membrane highly permeable to sodium.

The axon hillock is the specialized region where the axon originates from the cell body, and it is typically where the summation of graded potentials occurs to trigger an action potential.

The resting membrane potential is maintained by both the active transport of ions via the Na+/K+ pump (pumping 3 Na+ out and 2 K+ in) and the higher permeability of the membrane to K+ ions through leak channels, leading to a net efflux of K+ and a negative internal charge.

A synapse is the specialized junction or point of contact where an impulse is transmitted from one neuron to another or to an effector organ like a muscle or gland.

The synaptic knob (or terminal) is the swollen end of the presynaptic axon, which contains synaptic vesicles filled with neurotransmitters.

The synaptic cleft is the narrow space that separates the presynaptic membrane from the postsynaptic membrane.

Neurotransmitters are chemical substances stored in synaptic vesicles within the presynaptic terminal, which are released into the synaptic cleft to transmit signals.

When an action potential reaches the presynaptic terminal, voltage-gated Ca2+ channels open, and the influx of Ca2+ ions triggers the exocytosis of synaptic vesicles, releasing neurotransmitters into the cleft.

Neurotransmitters diffuse across the synaptic cleft and bind to specific receptor proteins on the postsynaptic membrane, causing a change in its permeability to ions.

Excitatory neurotransmitters cause a depolarization of the postsynaptic membrane, making it more likely for an action potential to be generated.

Inhibitory neurotransmitters cause hyperpolarization or stabilization of the resting potential of the postsynaptic membrane, making it less likely for an action potential to be generated.

Neurotransmitters must be quickly removed from the synaptic cleft (by enzymatic degradation or reuptake) to ensure that the postsynaptic neuron is not continuously stimulated or inhibited, allowing for precise and rapid control over neural signaling.

The binding of a neurotransmitter to its receptor directly causes ion channels to open or close, leading to a change in the postsynaptic membrane potential (either depolarization for excitation or hyperpolarization for inhibition).

The human nervous system consists of the central nervous system (CNS) and the peripheral nervous system (PNS).

The CNS is identified as the coordinating center and lies in the midline of the body, comprising the brain and spinal cord.

The PNS transmits information from receptors to the CNS and transmits orders and commands from the CNS to effectors.

The Somatic Nervous System controls voluntary movements.

The Sympathetic Division of the Autonomic Nervous System is responsible for the "Fight or Flight" response.

The Parasympathetic Division of the Autonomic Nervous System controls involuntary responses and is associated with "Rest and Digest" activities.

The Central Nervous System (CNS) consists of the Brain and Spinal Cord.

The brain receives and processes sensory information, initiates responses, stores memories, and generates thoughts and emotions. Reflex activities are primarily controlled by the spinal cord.

The spinal cord conducts signals to and from the brain and controls reflex activities.

Cranial and spinal nerves are components of the Peripheral Nervous System (PNS) that connect the CNS to receptors and effectors throughout the body.

Heroine is a narcotic drug, which affects the nervous system by acting on opiate receptors, producing feelings of euphoria and pain relief.

Convulsions are explicitly mentioned as a withdrawal symptom of alcohol, indicating the severe impact of alcohol dependence on the nervous system.

Drug addiction is characterized by both psychological dependence (craving the drug) and physiological dependence (withdrawal symptoms upon cessation), meaning the body has adapted to the drug's presence.

Drug tolerance refers to the phenomenon where, with repeated exposure, the body adapts to a drug, requiring increasingly larger doses to produce the same initial effect.

Cannabis (Marijuana) is classified as a hallucinogen, affecting perception and mood.

Stroke is a vascular disorder of the nervous system, typically caused by a disruption of blood flow to the brain, leading to brain damage.

Meningitis is an infectious disease of the nervous system characterized by inflammation of the meninges, the protective membranes surrounding the brain and spinal cord.

Magnetic Resonance Imaging (MRI) is a diagnostic test that utilizes strong magnetic fields and radio waves to produce detailed images of organs and soft tissues, including the brain and spinal cord.

Alzheimer's disease is a common neurodegenerative disorder primarily affecting older adults, characterized by progressive memory loss, cognitive decline, and changes in behavior.

An Electroencephalogram (EEG) is a diagnostic tool that measures and records the electrical activity of the brain, useful in diagnosing conditions like epilepsy and sleep disorders.

Hormones are chemical messengers secreted by endocrine glands that travel through the bloodstream to target cells, regulating a wide range of physiological processes.

The endocrine system coordinates most body cells by secreting hormones (chemical messengers) directly into the bloodstream, which then travel to target cells.

Endocrine glands are ductless glands that secrete hormones directly into the bloodstream, which then transports them to target cells or organs.

Exocrine glands secrete their products, such as digestive enzymes or sweat, into ducts that carry them to a specific external or internal surface.

Salivary glands are exocrine glands that secrete saliva through ducts into the mouth. The pancreas has both endocrine (insulin, glucagon) and exocrine (digestive enzymes) functions, but for this question, salivary gland is a clear example of a solely exocrine function.

Steroid hormones (e.g., testosterone, estrogen) are lipid-soluble hormones derived from cholesterol.

Insulin and growth hormone are examples of protein or peptide hormones, which are composed of amino acids.

Protein (and peptide) hormones, being water-soluble, cannot directly cross the cell membrane. They bind to receptors on the cell surface and activate a second messenger system, such as cAMP, to trigger intracellular responses. Insulin is a protein hormone.

Steroid hormones are lipid-soluble and can directly diffuse across the cell membrane. They bind to intracellular receptors (in the cytoplasm or nucleus) and the hormone-receptor complex then acts directly on DNA to activate or repress gene transcription, leading to protein synthesis.

Catecholamines (like epinephrine and norepinephrine) are amine hormones derived from amino acids (specifically tyrosine).

Hormones that are lipid-soluble (like steroid hormones and thyroid hormones) can readily diffuse across the lipid bilayer of the cell membrane to bind to receptors inside the cell.

Cyclic AMP (cAMP) is a common second messenger activated when water-soluble protein/peptide hormones bind to their receptors on the cell surface.

The binding of a protein hormone to its cell surface receptor typically activates an enzyme (like adenylate cyclase) that then produces a second messenger, such as cAMP, inside the cell.

Thyroxine (T4) is an amine hormone derived from the amino acid tyrosine, similar to catecholamines, but with different synthesis and action mechanisms.

The second messenger system provides signal amplification, meaning a single hormone molecule binding to its receptor can lead to the production of many second messenger molecules, resulting in a large and rapid cellular response.

The hypothalamus is described as the "master control center" because it plays a crucial role in regulating the anterior pituitary gland and influencing various endocrine functions.

The hypothalamus produces various releasing hormones (e.g., GnRH, TRH) and inhibiting hormones (e.g., GHIH, PIH) that regulate the secretion of hormones from the anterior pituitary gland.

Antidiuretic Hormone (ADH) and Oxytocin are neurohormones produced by neurosecretory cells in the hypothalamus, but they are transported down axons and stored in the posterior pituitary gland until their release.

ADH (Vasopressin) primarily acts on the kidneys to increase water reabsorption, thus conserving body water and concentrating urine.

Oxytocin is known for its role in stimulating uterine contractions during labor and promoting milk ejection during breastfeeding.

The pituitary gland is a pea-sized gland located at the base of the brain, beneath the hypothalamus, to which it is functionally and structurally connected.

The pituitary gland consists of three lobes: the anterior lobe, the posterior lobe, and the median (intermediate) lobe.

The anterior lobe of the pituitary gland is often called the "master gland" because it produces and secretes several hormones that regulate the function of other endocrine glands, such as the thyroid, adrenal cortex, and gonads.

Growth Hormone (GH), also known as Somatotropic Hormone (STH), is secreted by the anterior pituitary and promotes overall body growth, particularly in bones and muscles.

Acromegaly is a disorder resulting from the oversecretion of GH in adults, causing abnormal growth of bones in the face, hands, and feet after epiphyseal plates have closed.

Undersecretion of Growth Hormone (GH) during childhood leads to dwarfism, characterized by stunted growth.

Thyroid Stimulating Hormone (TSH), also known as thyrotropin, is secreted by the anterior pituitary and stimulates the thyroid gland to produce and release thyroid hormones.

The anterior pituitary secretes two gonadotropic hormones: Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH), which regulate the function of the gonads.

Prolactin (LTH - Luteotropic Hormone) primarily stimulates and maintains milk production after childbirth.

The median (intermediate) lobe of the pituitary gland secretes Melanocyte Stimulating Hormone (MSH).

ADH (Antidiuretic Hormone) and Oxytocin are produced by neurosecretory cells in the hypothalamus and then transported to and stored in the posterior pituitary for release.

Diabetes insipidus is a condition characterized by excessive urination and thirst, caused by the undersecretion of ADH (Vasopressin) from the posterior pituitary, leading to impaired water reabsorption by the kidneys.

Oxytocin's main functions include stimulating strong uterine contractions during labor and promoting milk ejection ("let-down") during breastfeeding.

Low levels of ADH would result in the kidneys reabsorbing less water, leading to increased urine output and potentially dehydration.

Many hormones from the anterior pituitary are "tropic hormones" (or tropins) because they target and stimulate other endocrine glands to secrete their own hormones (e.g., TSH on thyroid, ACTH on adrenal cortex).

The thyroid gland is located in the neck, anterior to the trachea, below the larynx.

Thyroxine (T4) and Triiodothyronine (T3) are the two iodine-containing hormones produced by the thyroid gland that play a crucial role in regulating basal metabolic rate.

Calcitonin is involved in calcium homeostasis; it works to decrease blood calcium levels by inhibiting osteoclast activity and promoting calcium deposition in bones.

Graves' disease is associated with hyperthyroidism (overactive thyroid), which leads to symptoms like increased metabolic rate, weight loss, heat intolerance, and nervousness.

Cretinism is caused by severe hypothyroidism (underactive thyroid) during infancy or early childhood, leading to impaired physical and mental development.

The parathyroid glands are usually four small glands embedded in the posterior surface of the thyroid gland.

The parathyroid glands secrete Parathyroid Hormone (PTH), which is the primary regulator of calcium levels in the blood.

PTH acts to increase blood calcium levels by stimulating osteoclasts to break down bone, enhancing calcium reabsorption in the kidneys, and promoting the synthesis of vitamin D, which aids in intestinal calcium absorption.

The endocrine cells of the pancreas are organized into clusters called Islets of Langerhans, which produce hormones.

Insulin, secreted by the beta cells of the Islets of Langerhans, acts to lower blood glucose levels by promoting glucose uptake by cells and its conversion to glycogen.

Glucagon, secreted by the alpha cells of the Islets of Langerhans, raises blood glucose levels primarily by stimulating the liver to release stored glucose (glycogenolysis) and produce new glucose (gluconeogenesis).

Insulin is released in response to high blood glucose levels to facilitate glucose uptake by cells and lower blood sugar.

The secretion of both insulin and glucagon is regulated by a negative feedback mechanism to maintain stable blood glucose levels. When glucose is high, insulin is released to lower it; when glucose is low, glucagon is released to raise it, thus opposing the initial change.

The adrenal gland is divided into two main parts: the outer adrenal cortex and the inner adrenal medulla.

The adrenal medulla is responsible for secreting the catecholamines Epinephrine and Norepinephrine, which are involved in the "fight or flight" response.

Cortisol is a glucocorticoid hormone produced by the adrenal cortex that plays a vital role in metabolism, immune response, and the body's response to stress.

Aldosterone, a mineralocorticoid from the adrenal cortex, is essential for maintaining electrolyte balance by regulating sodium and potassium levels in the blood, thereby influencing blood pressure.

The adrenal cortex also produces small amounts of androgens, which are male sex hormones, in both males and females.

Testosterone is the primary male sex hormone secreted by the interstitial cells of the testes.

Estrogens are the female sex hormones primarily produced by the ovaries, responsible for the development of female secondary sex characteristics and various aspects of the menstrual cycle.

Progesterone is produced by the corpus luteum (and later the placenta during pregnancy) and is vital for preparing the uterine lining for implantation and maintaining pregnancy.

Inhibin, secreted by Sertoli cells in the testes and granulosa cells in the ovaries, acts to inhibit the secretion of Follicle-Stimulating Hormone (FSH) from the anterior pituitary.

Undersecretion of progesterone during the menstrual cycle decreases the chance of pregnancy and may cause early menstruation or, if pregnancy occurs, may lead to miscarriage.

The pineal gland secretes Melatonin, a hormone that plays a crucial role in regulating the body's circadian rhythms, including sleep-wake cycles.

Thymosins, secreted by the thymus gland, are essential for the maturation and differentiation of T lymphocytes (T cells), which are crucial components of the immune system.

The heart secretes natriuretic peptides (e.g., ANP), which primarily act to lower blood pressure and blood volume by promoting sodium and water excretion by the kidneys.

Erythropoietin (EPO) is a hormone secreted by the kidneys in response to low oxygen levels, which stimulates the bone marrow to produce more red blood cells.

The kidneys convert an inactive form of Vitamin D into its active form, Calcitriol, which is crucial for the absorption of calcium from the digestive tract.

Adipose tissue produces and secretes Leptin, a hormone that signals satiety to the brain, helping to regulate energy balance and metabolism.

Gastrin is a hormone produced by the stomach that stimulates the secretion of gastric acid (HCl) by the parietal cells, playing a key role in digestion.