Unit A Practice Questions: Neurons, Nervous System, Brain, Senses & Endocrine System

Vocabulary study flashcards created from Unit A active-recall review questions covering neurobiology, sensory structures, endocrine glands, and homeostatic regulation mechanisms.

Neuron

A specialized cell whose main function is to receive, process, and transmit information using electrical and chemical signals.

Dendrites

Structures of a neuron that receive signals from other neurons or sensory receptors.

Cell Body (Soma)

The part of a neuron containing the nucleus and organelles that keeps the neuron functioning.

Axon

The structure of a neuron that carries an action potential away from the cell body toward the axon terminals.

Axon Terminals

Structures at the end of an axon that release neurotransmitters to communicate with another cell.

Myelin Sheath

An insulating layer around an axon that helps an action potential travel faster.

Nodes of Ranvier

Small gaps between sections of myelin where the action potential can be regenerated.

Resting Membrane Potential

The neuron's normal resting electrical state, with the inside more negative than the outside, Na+ relatively more concentrated outside, and K+ relatively more concentrated inside.

Depolarization

The phase of an action potential when voltage-gated sodium channels open and Na+ enters the neuron, making the inside less negative.

Repolarization

The phase of an action potential when voltage-gated potassium channels open and K+ moves out of the neuron, making the membrane more negative again.

Hyperpolarization

A phase where the neuron's membrane briefly becomes more negative than its normal resting level because K+ channels stay open slightly too long.

Threshold

The minimum membrane potential needed to trigger an action potential.

All-or-None Response

The principle stating that a neuron either produces a full action potential or does not produce one at all.

Reflex

A rapid, automatic response to a stimulus.

Sensory Receptor

A structure that detects a stimulus such as touch, temperature, light, or chemicals.

Sensory Neuron

A neuron in a reflex arc that carries information from a receptor toward the spinal cord.

Interneuron

A neuron located within the central nervous system (such as the spinal cord) that connects neurons and helps process signals.

Motor Neuron

A neuron that carries a signal from the central nervous system to an effector.

Effector

A muscle or gland that carries out a response.

Reflex Arc

The neural pathway of a reflex, following the order: Sensory receptor -> sensory neuron -> interneuron -> motor neuron -> effector.

Central Nervous System (CNS)

The division of the nervous system consisting of the brain and spinal cord.

Peripheral Nervous System (PNS)

The division of the nervous system consisting of nerves outside the brain and spinal cord.

Somatic Nervous System

The part of the nervous system mainly involved in voluntary control of skeletal muscles and sensory information.

Autonomic Nervous System

The part of the nervous system that controls many involuntary functions such as heart rate, digestion, and gland activity.

Sympathetic Nervous System

The division of the autonomic nervous system that prepares the body for action and stress (fight-or-flight response).

Parasympathetic Nervous System

The division of the autonomic nervous system that promotes rest, digestion, and recovery.

Cerebrum

The largest part of the brain, responsible for higher functions such as thinking, memory, senses, and voluntary movement.

Frontal Lobe

The lobe of the cerebrum mainly responsible for planning, decision-making, personality, problem-solving, and voluntary movement.

Parietal Lobe

The lobe of the cerebrum mainly responsible for processing touch and other body sensations and helping with spatial awareness.

Temporal Lobe

The lobe of the cerebrum mainly responsible for hearing, memory, language, and processing some aspects of emotion.

Occipital Lobe

The lobe of the cerebrum mainly responsible for processing visual information.

Cerebellum

The brain structure that mainly controls balance, posture, coordination, and smooth, precise movement.

Grey Matter

Brain tissue containing many neuron cell bodies that is mainly involved in processing information.

White Matter

Brain tissue containing many myelinated axons that mainly carries signals between different areas.

Neurilemma

The outer layer of a Schwann cell around a peripheral axon that supports and helps with repair/regeneration.

Cornea

The clear front surface of the eye that helps bend incoming light.

Iris

The eye structure that controls the size of the pupil and helps control how much light enters.

Pupil

The opening in the center of the iris through which light enters the eye.

Lens

The eye structure that focuses light onto the retina.

Retina

The inner layer of the eye containing photoreceptors that detect light and begin visual signaling.

Hyperopia

Farsightedness; a condition where nearby objects are harder to see clearly because the image tends to focus behind the retina, corrected using a converging/convex lens.

Myopia

Nearsightedness; a condition where distant objects are harder to see clearly because the image tends to focus in front of the retina, corrected using a diverging/concave lens.

Glaucoma

An eye disorder involving damage to the optic nerve, often associated with increased pressure inside the eye.

Cataracts

A clouding of the eye's lens that can make vision blurry.

Ossicles

Three bones in the ear (malleus, incus, and stapes) that amplify and transmit vibrations from the eardrum to the inner ear.

Cochlea

An inner ear structure that converts sound vibrations into nerve signals.

Auditory Nerve

The nerve that carries hearing information from the inner ear to the brain.

Semicircular Canal System

A structure in the inner ear that helps detect head movement and balance.

Endocrine System

A system of glands that releases hormones into the bloodstream to regulate body functions.

Hormone

A chemical messenger released by an endocrine gland that affects target cells.

Pituitary Gland

An endocrine gland often called the master gland because it controls or influences several other endocrine glands.

Human Growth Hormone (hGH)

A hormone released by the anterior pituitary gland that promotes growth and influences metabolism and tissue development.

Hypothalamus

A brain structure that links the nervous and endocrine systems and helps regulate processes such as temperature, hunger, thirst, and hormone control.

Thyroid Gland

An endocrine gland located in the front of the neck below the larynx that produces thyroxine.

Thyroxine

A hormone produced by the thyroid gland that helps regulate metabolic rate and energy use.

Thyroid-Stimulating Hormone (TSH)

A tropic hormone that targets the thyroid gland and stimulates it to release thyroxine.

Parathyroid Glands

Glands that release parathyroid hormone (PTH) to regulate blood calcium levels.

Adrenal Glands

Glands that produce hormones involved in stress responses, such as epinephrine, norepinephrine, cortisol, and aldosterone.

Epinephrine and Norepinephrine

Hormones produced by the adrenal glands that mediate short-term stress responses by increasing heart rate, breathing rate, and blood flow to muscles.

Cortisol

A hormone produced by the adrenal cortex involved in long-term stress, helping provide energy and maintain response to ongoing stress.

Pancreas

An organ that releases insulin and glucagon to help keep blood glucose within a normal range.

Negative Feedback

A control system in which a change triggers responses that reverse or reduce that change, helping maintain homeostasis.

Tropic Hormone

A hormone that acts on another endocrine gland and causes it to release hormones.

Adrenocorticotropic Hormone (ACTH)

A tropic hormone that targets the adrenal cortex to stimulate the release of cortisol.

Insulin

A hormone released by the pancreas when blood glucose is too high that lowers blood glucose by helping cells take up glucose and promoting its storage.

Glucagon

A hormone released by the pancreas when blood glucose is too low that raises blood glucose by signaling the body to release stored glucose.

Antidiuretic Hormone (ADH)

A hormone released by the posterior pituitary gland that increases water reabsorption in the kidneys to conserve water.

Aldosterone

A hormone released by the adrenal cortex that helps the kidneys retain sodium, causing water to follow, which increases blood volume and blood pressure.

Calcitonin

A hormone released by the thyroid gland that lowers blood calcium levels by promoting calcium storage in bone.

Parathyroid Hormone (PTH)

A hormone released by the parathyroid glands that raises blood calcium levels by promoting release from bone and increasing kidney conservation.

Chemoreceptor

A sensory receptor that detects chemicals, such as changes in oxygen, carbon dioxide, or taste molecules.

Mechanoreceptor

A sensory receptor that detects mechanical forces such as pressure, touch, stretch, or vibration.

Photoreceptor

A sensory receptor that detects light.

Thermoreceptor

A sensory receptor that detects temperature changes.

Diabetes Mellitus

A disorder involving insulin and blood glucose regulation that causes abnormally high blood glucose levels.

Diabetes Insipidus

A disorder involving ADH or the kidneys' response to ADH that causes excessive water loss and very dilute urine.