Nervous System Vocabulary

Action Potential

Axons

Cell Body

Dendrites

Myelin sheath

Nervous System

Neurons

The function of the 1) ______________ ____________ is to control and coordinate functions of the body and respond to external stimuli. It is composed of billions of cells called 2) _____________. These cells can be the longest cells in the body and have three distinct divisions. The impulse travels first into the neuron through the extensions called 3)_______________, then to the part of the neuron that contains the nucleus called the 4)_________ __________, and finally out of the neuron through one or more 5)____________. The nerve impulse is also called an 6)_________ ___________. It sweeps along a neuron at only one meter per second if the axons and dendrites do not have a 7) ________ _________ to insulate them, and at 100 meters per second if the neuron is myelinated with Schwann Cells.

diffuse

K+

Na+

Negative

Polarized

Positive

Repolarizes

Sodium-Potassium

Actions potentials can happen because the cell membrane around neurons becomes 8)_________________ with positive (+) charges on its outside and negative (-) charges on the inside. This difference in charge is forced by carrier proteins in the membrane called the 9) __________-____________. These pump 3 positive 10) ______ ions out of the neuron while pumping 2 positive 11) _____ ions into the cell. The membrane is more leaky to potassum ions (K+) than sodium ions (Na+) which 12)________________ with the concentration gradient across the membrane. Both of these mechanisms result in more 13)_____________ charges outside and more 14)_____________ charges inside. When an action potential (impulse) travels through the neuron the membrane becomes leaky to diffusion through its sodium and potassium channels. This causes a momentary reversal of charges as sodium rushes in and potassium rushes out with the concentration gradient. The sodium-potassium pump immediately 15)__________________ the membrane so that it can be ready for the next impulse.

Excitatory

Inhibitory

Neurotransmitters

Synapses

Neurons never really touch each other, so impulses cannot simply travel from one neuron to the next without jumping across gaps called 16)____________________. To jump these gaps, chemicals called 17)__________________ are released into the synapse. A neurotranmitter that stimulates the next neuron to "fire" is called an 18)_____________ neurotransmitter while one that keeps the next neuron from "firing" is called 19)________________. People that have seizures where their brain is flooded with too many neurons firing at once lack inhibitory neurotransmitters or may have too many excitatory neurotransmitters.

autonomic

central nervous system (CNS)

cerebrospinal

meninges

motor

peripheral nervous system (PNS)

reflexes

sensory

somatic

The nervous system is divided into two major divisions. The 20)___________________ consists of the brain and spinal cord. It is protected by 3 layers of membranes called the 21)________________. The CNS is bathed in a fluid called 22)________________________ fluid that acts as a shock absorber and allows exchange of nutrients between the neurons and blood. The other division of the nervous system that extends from the CNS to all body parts is the 23)___________________. There are two major types of neurons extensions from the PNS. 24)____________ neurons are axons that go from the brain and spinal cord to control muscles and organs. 25)________________neurons are dendrites that take messages of touch, taste, hearing, sight, and sound to the CNS for processing. The PNS also be divided into two more sections according to whether it is under conscious or unconscious control. The 26)____________ nervous system is under conscious control and controls movement of the skeletal muscles. This system also involves unconscious 27)_________ that allow you to act more quickly to dangerous stimuli, such as putting your hand onto a hot burner of a stove. The 28)________________ nervous system regulates automatic or involuntary activities such as the heartrate and control of the digestive system.

100

brain stem

cerebellum

cerebrum

death

gray

voluntary

white

The brain is composed of three main parts. The largest and most prominent region is the 29)________________ which is responsible for the 30)______________ or conscious activities of the body. It is composed of both 31)____________ matter which is unmyelinated and 32)_________ matter which is myelinated with Schwann cells. Gray matter is where connections and learning occur between neurons with synapses, while white matter is just taking messages to other parts of the CNS. Impulses travel 33)______ times faster in white matter. The 34)_____________ is located it the back of the skull and is responsible for coordination, muscle programming (such as juggling), balance, and proprioception (keeping track of body parts in space). The 35)_________ ______ connects the brain and the spinal cord. This is the part of the brain where our bodies' most basic functions of heart rate, breathing, swallowing, and blood pressure are controlled. Damage to this will result in 36)_____________.