Biological Sciences Vocab 1

Nervous System

The body’s speedy, electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous systems.

Central Nervous System (CNS)

The brain and spinal cord.

Peripheral Nervous System (PNS)

The sensory and motor neurons that connect the central nervous system to the rest of the body.

Nerves

Bundled axons that form neural cables connecting the central nervous system with muscles, glands, and sensory organs.

Sensory Neurons

Neurons that carry incoming information from the body’s tissues and sensory receptors to the brain and spinal cord.

Motor Neurons

Neurons that carry outgoing information from the brain and spinal cord to the muscles and glands.

Interneurons

Neurons within the brain and spinal cord; they communicate internally and process information between the sensory inputs and motor outputs.

Somatic Nervous System

The division of the peripheral nervous system that controls the body’s skeletal muscles. Also called the skeletal nervous system.

Autonomic Nervous System

The part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms.

Sympathetic Nervous System

The division of the autonomic nervous system that arouses the body, mobilizing its energy.

Parasympathetic Nervous System

The division of the autonomic nervous system that calms the body, conserving its energy.

Reflex

A simple, automatic response to a sensory stimulus, such as the knee-jerk response.

Neuron

A nerve cell; the basic building block of the nervous system.

Cell Body

The part of a neuron that contains the nucleus; the cell’s life-support center.

Dendrites

A neuron’s often bushy, branching extensions that receive and integrate messages, conducting impulses toward the cell body.

Axon

The segmented neuron extension that passes messages through its branches to other neurons or to muscles or glands.

Myelin Sheath

A fatty tissue layer segmentally encasing the axons of some neurons; it enables vastly greater transmission seed as neural impulses hop from one node to the next.

Gilal Cells

Cells in the nervous system that support, nourish, and protect neurons; they may also play a role in learning, thinking, and memory.

Action Potential

A neural impulse; a brief electrical charge that travels down an axon.

Threshold

The level of stimulation required to trigger a neural impulse.

Refractory Period

In neural processing, a brief resting pause occurs after a neuron has fired; subsequent action potentials cannot occur until the axon returns to its resting state.

All or Nothing Response

A neuron’s reaction of either firing (with a full-strength response) or not firing.

Synapse

The junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The tiny gap at this junction is called the synaptic gap or synaptic cleft.

Neurotransmitter

Chemical messengers that cross the synaptic gaps between neurons. When released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neural impulse.

Endorphins

“Morphine within”--natural, opioid like neurotransmitters linked to pain control and to pleasure.

Agonist

A molecule that increases a neurotransmitter’s action.

Antagonist

A molecule that inhibits or blocks a neurotransmitter’s action.

Endocrine System

The body’s "slow" chemical communication system; a set of glands and fat tissue that secrete hormones into the bloodstream.

Hormones

Chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues.