Response to Stimuli: Nervous System, Endocrine System, and Homeostasis

Comprehensive vocabulary flashcards covering multicellular organization, the structure and function of the human nervous and endocrine systems, neural transmission, reflex arcs, and homeostatic regulation.

Cells

The basic building blocks of life, with different types performing specialized functions.

Tissues

Groups of similar cells working together to perform a specific task, such as muscle tissue or nervous tissue.

Organs

Structures composed of different tissues that work together to carry out a more complex function, such as the heart, lungs, or brain.

Systems

Groups of organs that work together to perform a larger physiological function, such as the digestive or circulatory systems.

Organism

The complete living being, functioning through the coordinated action of all its organ systems.

Stimulus

A change in the internal or external environment of an organism that is detected by a receptor and triggers a physiological or behavioral response.

Response

An action or behavior exhibited by an organism, or a part of an organism, that occurs as a direct result of a stimulus.

Neurons

The fundamental units of the nervous system responsible for transmitting information throughout the body using electrochemical signals.

Endocrine system

A network of glands that produce and secrete hormones into the circulatory system to regulate various bodily functions.

Hormones

Chemical messengers produced and secreted by endocrine glands that travel through the bloodstream and bind to specific receptors on target cells to trigger responses.

Hypothalamus

An area of the brain that connects the brain to the hormonal system and releases hormones that help control the pituitary gland.

Pituitary gland

A small gland at the base of the brain referred to as the 'master gland' because it regulates many other endocrine glands, including the thyroid, adrenal glands, ovaries, and testes.

Thyroid gland

A gland located in the front of the neck that secretes Tri-iodothyronine (T3), Thyroxine (T4), and Calcitonin to influence metabolism, energy levels, body temperature, and calcium levels.

Parathyroid glands

Four small glands in the neck that secrete parathyroid hormone (PTH) to regulate calcium levels in the blood.

Adrenal glands

Glands located above the kidneys that secrete adrenaline, cortisol, aldosterone, dehydroepiandrosterone (DHEA), and small amounts of testosterone to regulate stress, blood pressure, and metabolism.

Pineal gland

A small gland near the centre of the brain that secretes melatonin to regulate the body clock (circadian rhythm).

Pancreas

A gland situated behind the stomach that acts as both an exocrine and endocrine gland, producing insulin, glucagon, vasoactive intestinal peptide (VIP), and somatostatin to control blood sugar levels and digestion.

Ovaries

Paired glands in females found on each side of the womb that store and release eggs and produce hormones including oestrogen, progesterone, testosterone, AMH, and inhibin A and B for puberty and reproduction.

Testes

Paired glands in males located in the scrotum that produce sperm and hormones including testosterone, AMH, estradiol, and inhibin B for puberty and reproduction.

Central Nervous System (CNS)

The primary division of the nervous system composed of the brain and spinal cord that coordinates bodily thoughts, actions, and responses.

Spinal cord

A column of nerve fibres extending from the base of the brain to the lower back that carries sensory information to the brain, delivers motor commands to skeletal muscles, and controls spinal reflexes.

Dendrite

A neuronal branch whose function is to receive information from other neurons and conduct nerve impulses toward the cell body (soma).

Cell body (Soma)

The central part of a neuron containing the nucleus, responsible for initiating messages to be passed down to adjacent neurons.

Axon

A nerve fibre that carries electrical nerve impulses away from the cell body toward other cells that communicate with the neuron.

Myelin sheath

A layer of fatty tissue surrounding the axon of a neuron that serves as an electrical insulator and facilitates faster signal transmission.

Nodes of Ranvier

Unmyelinated gaps located along the length of an axon between segments of the myelin sheath.

Axon terminal

The branching endpoint of an axon terminating in a button that releases neurotransmitters to transmit impulses across a synapse to neighbouring cells.

Sensory neurons (Afferent neurons)

Specialised bottom-up neurons that receive and transmit incoming sensory information from sensory receptors to the Central Nervous System.

Interneurons

Relay neurons located exclusively within the Central Nervous System that process and transmit information between sensory neurons and motor neurons.

Motor neurons (Efferent neurons)

Specialised top-down neurons that transmit motor messages outward from the brain and Central Nervous System to skeletal muscles and glands.

Upper Motor Neurons (UMNs)

Motor neurons located in the motor cortex (precentral gyrus) of the brain that send signals down the spinal cord to initiate, plan, and refine motor commands.

Lower Motor Neurons (LMNs)

Motor neurons located in the spinal cord anterior horn cells and cranial nerve nuclei that receive signals from upper motor neurons and directly innervate muscles and glands.

Spinal reflex

An involuntary, innate, and rapid automatic motor response controlled solely by neural circuits in the spinal cord without brain initiation.

Reflex arc

The neural pathway underlying a spinal reflex, typically composed of a sensory neuron and a motor neuron communicating through an interneuron in the spinal cord.

Action potential

An electrical impulse originating in the soma that propagates down the axon to transmit signals through the nervous system.

Synapse

The specialized junction where an axon terminal of a presynaptic neuron transmits a chemical message across the synaptic gap to a postsynaptic neuron.

Neurotransmitter

A chemical messenger stored in synaptic vesicles and released into the synaptic cleft to bind to specific receptors on a postsynaptic neuron.

Homeostasis

The process by which organisms maintain a stable internal environment for their cells by regulating factors such as temperature, water, salt, and blood sugar levels.

Negative feedback

The primary homeostatic control mechanism that works by counteracting a detected deviation in a physiological variable to bring it back toward its set point.

Insulin

A hormone released by pancreatic beta cells when blood glucose rises, lowering blood glucose by promoting cellular glucose uptake and liver storage as glycogen.

Glucagon

A hormone released by pancreatic alpha cells when blood glucose falls, raising blood glucose by stimulating the liver to break down glycogen and release glucose.

Modulator

The control centre component of the stimulus-response model (such as the brain or spinal cord) that processes incoming sensory information and coordinates a response.

Effector

A muscle, organ, or gland in the stimulus-response model that receives instructions from a motor pathway and executes the physiological response.