Chapter 8: The Nervous System and Homeostasis - Vocabulary Flashcards

Flashcards for reviewing key vocabulary from Chapter 8: The Nervous System and Homeostasis.

Homeostasis

The tendency of the body to maintain a relatively constant internal environment.

Sensor

A body structure that monitors and detects changes in the internal environment.

Control Centre

A body structure that sets the range of values within which a variable should be maintained, receives information from the sensor, and sends signals to effectors when needed.

Effector

A body structure that responds to signals from a control centre to effect change in a variable.

Negative Feedback System

Mechanism of homeostatic response by which the output of a system reverses a change in a variable, bringing the variable back to within normal range.

Positive Feedback System

Mechanism of homeostatic response by which the output of a system strengthens or increases a change in a variable.

Central Nervous System

Network of nerves that includes the brain and spinal cord; integrates and processes information sent by nerves.

Peripheral Nervous System

Network of nerves that carry sensory messages to the central nervous system (CNS) and send information from the CNS to the muscles and glands; consists of the autonomic and somatic system.

Neuron

Nerve cell; the structural and functional unit of the nervous system, consisting of a nucleus, cell body, dendrites, and axons; specialized to respond to physical and chemical stimuli, to conduct electrochemical signals, and to release chemicals that regulate various body processes.

Nerve

Message pathway of the nervous system; made up of many neurons grouped into bundles and surrounded by protective connective tissue.

Glial Cell

Support cell of the nervous system that nourishes neurons (nerve- impulse conducting cells), removes their wastes, defends against infection, and provides a supporting framework for all the nervous- system tissue.

Myelin Sheath

The fatty, insulating layer around the axon of a nerve cell, composed of Schwann cells; protects myelinated axons and speeds the rate of nerve impulse transmission.

Reflex Arc

Simple connection of neurons that results in a reflex action in response to a stimulus.

Membrane Potential

Electrical charge separation across a cell membrane; a form of potential energy.

Resting Membrane Potential

Potential difference across the membrane in a resting neuron.

Polarization

Lowering the membrane potential of the cell below its equilibrium value; in nerves, the process of generating a resting membrane potential of −70 mV.

Sodium-Potassium Pump

System involving a carrier protein in the plasma membrane that uses the energy of ATP to transport sodium ions out of and potassium ions into animal cells; important in nerve and muscle cells.

Action Potential

In an axon, the change in charge that occurs when the gates of the K+ channels close and the gates of the Na+ channels open after a wave of depolarization is triggered.

Synapse

Junction between two neurons or between a neuron and an effector (muscle or gland).

Neurotransmitter

Chemical messenger secreted by neurons to carry a neural signal from one neuron to another, or from a neuron to an effector, such as a gland or muscle fibre.

Acetylcholine

The primary neurotransmitter of both the somatic nervous system and the parasympathetic nervous system.

Meninges

Three layers of tough, elastic tissue within the skull and spinal column that directly enclose the brain and spinal cord.

Blood-Brain Barrier

Protective barrier formed by glial cells and blood vessels that separates the blood from the central nervous system; selectively controls the entrance of substances into the brain from the blood.

Cerebrospinal Fluid

Dense, clear liquid derived from blood plasma, found in the ventricles of the brain, in the central canal of the spinal cord, and in association with the meninges; transports hormones, white blood cells, and nutrients across the blood-brain barrier to the cells of the brain and spinal cord; acts as a shock absorber to cushion the brain.

Cerebral Cortex

Thin outer covering of grey matter that covers each cerebral hemisphere of the brain; responsible for language, memory, personality, conscious thought, and other activities that are associated with thinking and feeling.

Corpus Callosum

Bundle of white matter that joins the two cerebral hemispheres of the cerebrum of the brain; sends messages from one cerebral hemisphere to the other, telling each half of the brain what the other half is doing.

Occipital Lobe

Lobe of the cerebral cortex that receives and analyzes visual information, and is needed for recognition of what is being seen.

Temporal Lobe

Lobe of the cerebral cortex that shares in the processing of visual information but its main function is auditory reception.

Parietal Lobe

Lobe of the cerebral cortex that receives and processes sensory information from the skin, and helps to process information about the body’s position and orientation.

Frontal Lobe

Lobe of the cerebral cortex that integrates information from other parts of the brain and controls reasoning, critical thinking, memory, and personality.

Somatic System

In vertebrates, division of the peripheral nervous system that controls voluntary movement of skeletal muscles.

Autonomic System

In vertebrates, the division of the peripheral nervous system that controls involuntary glandular secretions and the functions of smooth and cardiac muscle.

Sympathetic Nervous System

Division of the autonomic system that regulates involuntary processes in the body; works in opposition to the parasympathetic nervous system; typically activated in stress-related situations.

Norepinephrine

Neurotransmitter released by sympathetic neurons of the autonomic system to produce an excitatory effect on target muscles; also a hormone produced by the adrenal medulla.

Parasympathetic Nervous System

Division of the auto- nomic system that regulates involuntary processes in the body; works in opposition to the sympathetic nervous system; typically activated when the body is calm and at rest.