Cells, Organs & Tissues, NAS-PLA
Even if you feel you have nothing in common with a stinkbug or a ficus, you're guaranteed to share one crucial aspect of life with these beings: you are all made up of cells, the fundamental molecules of life, of which all living things are composed. As an individual unit, the cell is capable of metabolizing its own nutrients, synthesizing many types of molecules, providing its own energy, and replicating itself. In a multicellular organism, cooperative assemblies of similar cells form tissues, and a cooperation between tissues in turn forms organs, which carry out the functions necessary to sustain the life of an organism.
Cells, Organs & Tissues Encyclopedia Articles By Title
Nasal gland
Nasal gland, in marine birds and reptiles that drink saltwater, gland that extracts the salt and removes it from......
nectar
nectar, sweet viscous secretion from the nectaries, or glands, in plant blossoms, stems, and leaves. Nectar is......
nematocyst
nematocyst, minute, elongated, or spherical capsule produced exclusively by members of the phylum Cnidaria (e.g.,......
Nephridium
Nephridium, unit of the excretory system in many primitive invertebrates and also in the amphioxus; it expels wastes......
nephron
nephron, functional unit of the kidney, the structure that actually produces urine in the process of removing waste......
nerve
nerve, in anatomy, a glistening white cordlike bundle of fibres, surrounded by a sheath, that connects the nervous......
Nerve net
Nerve net, primitive nerve arrangement forming the entire nervous system of many cnidarians and a part of more......
nervous system
nervous system, organized group of cells specialized for the conduction of electrochemical stimuli from sensory......
- Introduction
- Organelles, Cells, Functions
- Neurons, Signals, Reflexes
- Axon, Signals, Neurotransmitters
- Astrocytes, Oligodendrocytes, Microglia
- Ionic Signals, Neurons, Synapses
- Neurons, Membrane, Signals
- Signaling, Neurons, Impulses
- Sodium-Potassium Pump, Active Transport, Neurotransmission
- Neurotransmitters, Neuromodulators
- Neurotransmitter, Dopamine, Signaling
- Evolution, Development, Structure
- Autonomic, Reflexes, Sensory
- Annelids, Reflexes, Sensory
- Arthropods, Reflexes, Sensory
- Brain, Spinal Cord, Neurons
- Brain, Control, Communication
nervous system, human
human nervous system, system that conducts stimuli from sensory receptors to the brain and spinal cord and conducts......
- Introduction
- Morphology, Development, Anatomy
- Brain, Spinal Cord, Neurons
- Cerebrum, Brainstem, Cortex
- Brain Lobes, Cortex, Neurons
- Brainstem, Reflexes, Cranial Nerves
- Medulla, Brainstem, Reflexes
- Cerebellum, Motor Control, Coordination
- Spinal Cord, Reflexes, Sensory-Motor
- Descending Tracts, Motor Control, Sensory Input
- Peripheral Nerves, Sensory-Motor Pathways, Reflexes
- Cervical Plexus, Nerve Fibers, Nerve Impulses
- Cranial Nerves, Anatomy, Function
- Ophthalmic Nerve, Brain, Spinal Cord
- Vestibulocochlear, CN VIII, 8
- Autonomic, Neurotransmitters, Anatomy
- Parasympathetic, Autonomic, Reflexes
- Functions, Anatomy, Control
- Receptors, Signals, Pathways
- Reflex Actions, Motor Pathways, Sensory Pathways
- Motor, Sensory, Reflex
- Motor, Sensory, Reflex
- Motor Control, Reflexes, Movement
- Vestibular, Sensory, Motor
- Vestibular, Balance, Coordination
- Eye, Optic Nerve, Visual Cortex
- Reproduction, Anatomy, Physiology
- Pain, Sensory Receptors, Nerve Impulses
- Pain Pathways, Neurotransmitters, Sensory Receptors
- Perception, Sensory Organs, Signals
- Emotion, Behaviour, Control
- Urination, Defecation, Control
- Circadian Rhythms, Neurotransmitters, Anatomy
- Brain Functions, Neurons, Signals
- Brain, Neurons, Signals
- Memory, Brain, Neurons
neural oscillation
neural oscillation, synchronized rhythmic patterns of electrical activity produced by neurons in the brain, spinal......
neural stem cell
neural stem cell, largely undifferentiated cell originating in the central nervous system. Neural stem cells (NSCs)......
neuroglia
neuroglia, any of several types of cell that function primarily to support neurons. The term neuroglia means “nerve......
Neurohormone
Neurohormone, any of a group of substances that are produced by specialized neurosecretory cells of the nervous......
neuromuscular junction
neuromuscular junction, site of chemical communication between a nerve fibre and a muscle cell. The neuromuscular......
neuron
neuron, basic cell of the nervous system in vertebrates and most invertebrates, appearing in organisms as simple......
neuroplasticity
neuroplasticity, capacity of neurons and neural networks in the brain to change their connections and behaviour......
neurosecretory cell
neurosecretory cell, a type of neuron, or nerve cell, whose function is to translate neural signals into chemical......
neurotransmitter
neurotransmitter, any of a group of chemical agents released by neurons (nerve cells) to stimulate neighbouring......
neurotransmitter release
neurotransmitter release, discharge of chemical substances known as neurotransmitters from a neuron in response......
neutrophil
neutrophil, type of white blood cell (leukocyte) that is characterized histologically by its ability to be stained......
Nitroplast
A nitroplast is a nitrogen-fixing organelle found in the unicellular marine alga Braarudosphaera bigelowii. It......
node of Ranvier
node of Ranvier, periodic gap in the insulating sheath (myelin) on the axon of certain neurons that serves to facilitate......
normoblast
normoblast, nucleated normal cell occurring in red marrow as a stage or stages in the development of the red blood......
nose
nose, the prominent structure between the eyes that serves as the entrance to the respiratory tract and contains......
nucleolus
nucleolus, spherical body within the nucleus of most eukaryotic cells, involved in the synthesis of ribosomal RNA......
nucleus
nucleus, in biology, a specialized structure occurring in most cells (except bacteria and blue-green algae) and......
occipital
occipital, bone forming the back and back part of the base of the cranium, the part of the skull that encloses......
Odour
Odour, the property of certain substances, in very small concentrations, to stimulate chemical sense receptors......
Ohsumi, Yoshinori
Yoshinori Ohsumi is a Japanese cell biologist known for his work in elucidating the mechanisms of autophagy, a......
Oil gland
Oil gland, any of a variety of skin structures that secrete oily or greasy substances of various functions. In......
olfactory bulb
olfactory bulb, structure located in the forebrain of vertebrates that receives neural input about odours detected......
olfactory receptor
olfactory receptor, protein capable of binding odour molecules that plays a central role in the sense of smell......
olfactory system
olfactory system, the bodily structures that serve the sense of smell. The system consists of the nose and the......
oligodendrocyte
oligodendrocyte, a type of neuroglia found in the central nervous system of invertebrates and vertebrates that......
oogenesis
oogenesis, in the human female reproductive system, growth process in which the primary egg cell (or ovum) becomes......
optic nerve
optic nerve, second cranial nerve, which carries sensory nerve impulses from the more than one million ganglion......
Organ
Organ, in biology, a group of tissues in a living organism that have been adapted to perform a specific function.......
Organelle
Organelle, any of the specialized structures within a cell that perform a specific function. Organelles may be......
Osmoregulation
Osmoregulation, in biology, maintenance by an organism of an internal balance between water and dissolved materials......
osteoblast
osteoblast, large cell responsible for the synthesis and mineralization of bone during both initial bone formation......
osteoclast
osteoclast, large multinucleated cell responsible for the dissolution and absorption of bone. Bone is a dynamic......
osteocyte
osteocyte, mature bone cell that maintains bone tissue and coordinates the continual remodeling of bone. Embedded......
osteon
osteon, the chief structural unit of compact (cortical) bone, consisting of concentric bone layers called lamellae,......
ovary
ovary, in zoology, female reproductive organ in which sex cells (eggs, or ova) are produced. The usually paired......
Oviparity
Oviparity, expulsion of undeveloped eggs rather than live young. The eggs may have been fertilized before release,......
ovulation
ovulation, release of a mature egg from the female ovary; the release enables the egg to be fertilized by the male......
ovum
ovum, in human physiology, single cell released from either of the female reproductive organs, the ovaries, which......
Owen, Richard
Richard Owen was a British anatomist and paleontologist who is remembered for his contributions to the study of......
P blood group system
P blood group system, classification of human blood based on the presence of any of three substances known as the......
Paget, Sir James, 1st Baronet
Sir James Paget, 1st Baronet was a British surgeon and surgical pathologist. Working at St. Bartholomew’s Hospital,......
pain
pain, complex experience consisting of a physiological and a psychological response to a noxious stimulus. Pain......
Palade, George E.
George E. Palade was a Romanian-born American cell biologist who developed tissue-preparation methods, advanced......
palate
palate, in vertebrate anatomy, the roof of the mouth, separating the oral and nasal cavities. It consists of an......
pancreas
pancreas, compound gland that discharges digestive enzymes into the gut and secretes the hormones insulin and glucagon,......
Paneth’s cell
Paneth’s cell, specialized type of epithelial cell found in the mucous-membrane lining of the small intestine and......
Panting
Panting, a method of cooling, used by many mammals, most birds, and some reptiles, accomplished by means of the......
parasympathetic nervous system
parasympathetic nervous system, division of the nervous system that primarily modulates visceral organs such as......
parathyroid gland
parathyroid gland, endocrine gland occurring in all vertebrate species from amphibia upward, usually located close......
parenchyma
parenchyma, in plants, tissue typically composed of living cells that are thin-walled, unspecialized in structure,......
parietal bone
parietal bone, cranial bone forming part of the side and top of the head. In front each parietal bone adjoins the......
parietal cell
parietal cell, in biology, one of the cells that are the source of the hydrochloric acid and most of the water......
Paulescu, Nicolas C.
Nicolas C. Paulescu was a Romanian physiologist who conducted groundbreaking research on the antidiabetic hormone......
Pavlov, Ivan
Ivan Pavlov was a Russian physiologist known chiefly for his development of the concept of the conditioned reflex.......
Pectin
Pectin, any of a group of water-soluble carbohydrate substances that are found in the cell walls and intercellular......
pectoral girdle
pectoral girdle, in anatomy, the bony structure on either side of the body that connects the arm to the upper portion......
pectoralis muscle
pectoralis muscle, any of the muscles that connect the front walls of the chest with the bones of the upper arm......
pelage
pelage, hairy, woolly, or furry coat of a mammal, distinguished from the underlying bare skin. The pelage is significant......
pelvis
pelvis, in human anatomy, basin-shaped complex of bones that connects the trunk and the legs, supports and balances......
penis
penis, the copulatory organ of the male of higher vertebrates that in mammals usually also provides the channel......
periodontal membrane
periodontal membrane, fleshy tissue between tooth and tooth socket that holds the tooth in place, attaches it to......
periosteum
periosteum, dense fibrous membrane covering the surfaces of bones, consisting of an outer fibrous layer and an......
peripheral immune tolerance
peripheral immune tolerance, the set of mechanisms that prevent immune cells—especially T cells and B cells—from......
peristalsis
peristalsis, involuntary movements of the longitudinal and circular muscles, primarily in the digestive tract but......
peritoneum
peritoneum, large membrane in the abdominal cavity that connects and supports internal organs. It is composed of......
peroxisome
peroxisome, membrane-bound organelle occurring in the cytoplasm of eukaryotic cells. Peroxisomes play a key role......
perspiration
perspiration, in most mammals, water given off by the intact skin, either as vapour by simple evaporation from......
Peyer patch
Peyer patch, any of the nodules of lymphatic cells that aggregate to form bundles or patches and occur usually......
Pfeffer, Wilhelm
Wilhelm Pfeffer was a German botanist whose work on osmotic pressure made him a pioneer in the study of plant physiology.......
phagocyte
phagocyte, type of cell that has the ability to ingest, and sometimes digest, foreign particles, such as bacteria,......
phagocytosis
phagocytosis, process by which cells known as phagocytes ingest or engulf other cells or particles. The phagocyte......
phantom limb syndrome
phantom limb syndrome, the ability to feel sensations and even pain in a limb or limbs that no longer exist. Phantom......
pharynx
pharynx, cone-shaped passageway leading from the oral and nasal cavities in the head to the esophagus and larynx.......
phenylthiocarbamide tasting
phenylthiocarbamide tasting, a genetically controlled ability to taste phenylthiocarbamide (PTC) and a number of......
pheromone
pheromone, any endogenous chemical secreted in minute amounts by an organism in order to elicit a particular reaction......
phloem
phloem, plant vascular tissue that conducts foods made in the leaves during photosynthesis to all other parts of......
photophore
photophore, light-emitting organ present in fireflies and certain other bioluminescent animals. Photophores are......
Photoreception
Photoreception, any of the biological responses of animals to stimulation by light. In animals, photoreception......
photosynthesis
photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical......
Physiology
Physiology, study of the functioning of living organisms, animal or plant, and of the functioning of their constituent......
pineal gland
pineal gland, endocrine gland found in vertebrates that is the source of melatonin, a hormone derived from tryptophan......
pinocytosis
pinocytosis, a process by which liquid droplets are ingested by living cells. Pinocytosis is one type of endocytosis,......
pituitary gland
pituitary gland, ductless gland of the endocrine system that secretes hormones directly into the bloodstream. The......
pivot joint
pivot joint, in vertebrate anatomy, a freely moveable joint (diarthrosis) that allows only rotary movement around......
plane joint
plane joint, in anatomy, type of structure in the body formed between two bones in which the articular, or free,......
Plant cell
Plant cell, the basic unit of all plants. Plant cells, like animal cells, are eukaryotic, meaning they have a membrane-bound......
plasma
plasma, the liquid portion of blood. Plasma serves as a transport medium for delivering nutrients to the cells......
plasma cell
plasma cell, short-lived antibody-producing cell derived from a type of leukocyte (white blood cell) called a B......
plasmodesma
plasmodesma, microscopic cytoplasmic canal that passes through plant-cell walls and allows direct communication......
plasmodium
plasmodium, in fungi (kingdom Fungi), a mobile multinucleate mass of cytoplasm without a firm cell wall. A plasmodium......
platelet
platelet, colourless, nonnucleated blood component that is important in the formation of blood clots (coagulation).......