Key Terms

action potential

a momentary change in the electrical potential of a neuron (or muscle) membrane

adrenal gland

the endocrine gland associated with the kidneys

alveolus

(plural: alveoli) (also, air sacs) the terminal structure of the lung passage where gas exchange occurs

amygdala

a structure within the limbic system that processes fear

amylase

an enzyme found in saliva and secreted by the pancreas that converts carbohydrates to maltose

anus

the exit point of the digestive system for waste material

aorta

the major artery that takes blood away from the heart to the systemic circulatory system

appendicular skeleton

the skeleton composed of the bones of the upper limbs, which function to grasp and manipulate objects, and the lower limbs, which permit locomotion

artery

a blood vessel that takes blood away from the heart

atrium

(plural: atria) a chamber of the heart that receives blood from the veins

auditory ossicles

(also, middle ear bones) the bones that transduce sounds from the air into vibrations in the fluid-filled cochlea

autonomic nervous system

the part of the peripheral nervous system that controls bodily functions

axial skeleton

skeleton that forms the central axis of the body and includes the bones of the skull, the ossicles of the middle ear, the hyoid bone of the throat, the vertebral column, and the thoracic cage (ribcage)

axon

a tube-like structure that propagates a signal from a neuron’s cell body to axon terminals

basal ganglia

an interconnected collections of cells in the brain that are involved in movement and motivation

bicuspid valve

a one-way opening between the atrium and the ventricle in the left side of the heart

bile

a digestive juice produced by the liver; important for digestion of lipids

bolus

a mass of food resulting from chewing action and wetting by saliva

brainstem

a portion of brain that connects with the spinal cord; controls basic nervous system functions like breathing and swallowing

bronchi

(singular: bronchus) smaller branches of cartilaginous tissue that stem off of the trachea; air is funneled through the bronchi to the region where gas exchange occurs in the alveoli

bronchiole

an airway that extends from the main bronchus to the alveolar sac

capillary

the smallest blood vessel that allows the passage of individual blood cells and the site of diffusion of oxygen and nutrient exchange

cardiac cycle

the filling and emptying the heart of blood caused by electrical signals that cause the heart muscles to contract and relax

cardiac muscle tissue

the muscle tissue found only in the heart; cardiac contractions pump blood throughout the body and maintain blood pressure

cartilaginous joint

a joint in which the bones are connected by cartilage

central nervous system (CNS)

the nervous system made up of the brain and spinal cord; covered with three layers of protective meninges

cerebellum

the brain structure involved in posture, motor coordination, and learning new motor actions

cerebral cortex

the outermost sheet of brain tissue; involved in many higher-order functions

cerebrospinal fluid (CSF)

a clear liquid that surrounds the brain and fills its ventricles and acts as a shock absorber

chyme

a mixture of partially digested food and stomach juices

closed circulatory system

a system that has the blood separated from the bodily interstitial fluid and contained in blood vessels

colon

the largest portion of the large intestine consisting of the ascending colon, transverse colon, and descending colon

corpus callosum

a thick nerve bundle that connects the cerebral hemispheres

dendrite

a structure that extends away from the cell body to receive messages from other neurons

depolarization

a change in the membrane potential to a less negative value

diaphragm

a skeletal muscle located under lungs that encloses the lungs in the thorax

diastole

the relaxation phase of the cardiac cycle when the heart is relaxed and the ventricles are filling with blood

down-regulation

a decrease in the number of hormone receptors in response to increased hormone levels

ectotherm

an organism that relies primarily on environmental heat sources to maintain its body temperature

electrocardiogram (ECG)

a recording of the electrical impulses of the cardiac muscle

endocrine gland

the gland that secretes hormones into the surrounding interstitial fluid, which then diffuse into blood and are carried to various organs and tissues within the body

endotherm

an organism that relies primarily on internal heat sources to maintain its body temperature

esophagus

a tubular organ that connects the mouth to the stomach

essential nutrient

a nutrient that cannot be synthesized by the body; it must be obtained from food

exocrine gland

the gland that secretes chemicals through ducts that lead to skin surfaces, body cavities, and organ cavities.

fibrous joint

a joint held together by fibrous connective tissue

frontal lobe

the part of the cerebral cortex that contains the motor cortex and areas involved in planning, attention, and language

gallbladder

the organ that stores and concentrates bile

glia

(also, glial cells) the cells that provide support functions for neurons

hippocampus

the brain structure in the temporal lobe involved in processing memories

hormone

a chemical released by cells in one area of the body that affects cells in other parts of the body

hyoid bone

the bone that lies below the mandible in the front of the neck

hypothalamus

the brain structure that controls hormone release and body homeostasis

inferior vena cava

the major vein of the body returning blood from the lower parts of the body to the right atrium

interstitial fluid

the fluid found between cells in the body, similar in constitution to the fluid component of blood, but without the high concentrations of proteins

intracellular hormone receptor

a hormone receptor in the cytoplasm or nucleus of a cell

joint

the point at which two or more bones meet

kidney

the organ that performs excretory and osmoregulatory functions

large intestine

a digestive system organ that reabsorbs water from undigested material and processes waste matter

larynx

the voice box, located within the throat

limbic system

a connected brain area that processes emotion and motivation

liver

an organ that produces bile for digestion and processes vitamins and lipids

membrane potential

a difference in electrical potential between the inside and outside of a cell

meninges

(singular: meninx) the membranes that cover and protect the central nervous system

mineral

an inorganic, elemental molecule that carries out important roles in the body

myelin sheath

a cellular extension containing a fatty substance produced by glia that surrounds and insulates axons

myofibril

the long cylindrical structures that lie parallel to the muscle fiber

myofilament

the small structures that make up myofibrils

nasal cavity

an opening of the respiratory system to the outside environment

nephron

the functional unit of the kidney

neuron

a specialized cell that can receive and transmit electrical and chemical signals

occipital lobe

the part of the cerebral cortex that contains visual cortex and processes visual stimuli

open circulatory system

a circulatory system that has the blood mixed with interstitial fluid in the body cavity and directly bathes the organs

oral cavity

the point of entry of food into the digestive system

osmoregulation

the mechanism by which water and solute concentrations are maintained at desired levels

osmotic balance

the appropriate values of water and solute concentrations for a healthy organism

pancreas

a gland that secretes digestive juices

pancreas

the organ located between the stomach and the small intestine that contains exocrine and endocrine cells

parasympathetic nervous system

the division of autonomic nervous system that regulates visceral functions during relaxation

parathyroid gland

the gland located on the surface of the thyroid that produces parathyroid hormone

parietal lobe

the part of the cerebral cortex involved in processing touch and the sense of the body in space

pectoral girdle

the bones that transmit the force generated by the upper limbs to the axial skeleton

pelvic girdle

the bones that transmit the force generated by the lower limbs to the axial skeleton

pepsin

an enzyme found in the stomach whose main role is protein digestion

peripheral nervous system (PNS)

the nervous system that serves as the connection between the central nervous system and the rest of the body; consists of the autonomic nervous system and the sensory-somatic nervous system

peristalsis

wave-like movements of muscle tissue

pharynx

the throat

pituitary gland

the endocrine gland located at the base of the brain composed of an anterior and posterior region; also called hypophysis

primary bronchus

(also, main bronchus) a region of the airway within the lung that attaches to the trachea and bifurcates to form the bronchioles

pulmonary circulation

the flow of blood away from the heart through the lungs where oxygenation occurs and then back to the heart

rectum

the area of the body where feces is stored until elimination

renal artery

the artery that delivers blood to the kidney

renal vein

the vein that drains blood from the kidney

salivary gland

one of three pairs of exocrine glands in the mammalian mouth that secretes saliva, a mix of watery mucus and enzymes

sarcolemma

the plasma membrane of a skeletal muscle fiber

sarcomere

the functional unit of skeletal muscle

sensory-somatic nervous system

the system of sensory and motor nerves

set point

the target value of a physiological state in homeostasis

skeletal muscle tissue

forms skeletal muscles, which attach to bones and control locomotion and any movement that can be consciously controlled

skull

the bone that supports the structures of the face and protects the brain

small intestine

the organ where digestion of protein, fats, and carbohydrates is completed

smooth muscle tissue

the muscle that occurs in the walls of hollow organs such as the intestines, stomach, and urinary bladder, and around passages such as the respiratory tract and blood vessels

spinal cord

a thick fiber bundle that connects the brain with peripheral nerves; transmits sensory and motor information; contains neurons that control motor reflexes

stomach

a saclike organ containing acidic digestive juices

superior vena cava

the major vein of the body returning blood from the upper part of the body to the right atrium

sympathetic nervous system

the division of autonomic nervous system activated during stressful "fight-or-flight” situations

synapse

a junction between two neurons where neuronal signals are communicated

synaptic cleft

a space between the presynaptic and postsynaptic membranes

synovial joints

the only joints that have a space between the adjoining bones

systemic circulation

the flow of blood away from the heart to the brain, liver, kidneys, stomach, and other organs, the limbs, and the muscles of the body, and then back to the heart

systole

the contraction phase of cardiac cycle when the ventricles are pumping blood into the arteries

temporal lobe

the part of the cerebral cortex that processes auditory input; parts of the temporal lobe are involved in speech, memory, and emotion processing

thalamus

the brain area that relays sensory information to the cortex

thoracic cage

(also, ribcage) the skeleton of the chest, which consists of the ribs, thoracic vertebrae, sternum, and costal cartilages

threshold of excitation

the level of depolarization needed for an action potential to fire

thymus

the gland located behind the sternum that produces thymosin hormones that contribute to the development of the immune system

thyroid gland

an endocrine gland located in the neck that produces thyroid hormones thyroxine and triiodothyronine

trachea

the cartilaginous tube that transports air from the throat to the lungs

tricuspid valve

a one-way opening between the atrium and the ventricle in the right side of the heart

up-regulation

an increase in the number of hormone receptors in response to increased hormone levels

ureter

the urine-bearing tubes coming out of the kidney

urethra

the tube that conducts urine from the urinary bladder to the external environment

urinary bladder

the structure that the ureters empty the urine into

vein

a blood vessel that brings blood back to the heart

ventricle

(of the heart) a large chamber of the heart that pumps blood into arteries

vertebral column

(also, spine) the column that surrounds and protects the spinal cord, supports the head, and acts as an attachment point for ribs and muscles of the back and neck

vitamin

an organic substance necessary in small amounts to sustain life