Biology Chapter 9

moving

moto-

somatic nervous system

motor pathways of peripheral nervous system that lead to skin and skeletal muscles

True

Neurons that are deprived of oxygen can be irreversibly damage T/F

rind or peel

-lemm

Synapse

A ____ is the junction between two neurons

negative

A cell membrane is usually polarized, with an excess of _____ charges on the inside of the membrane; polarization is important to the conduction of nerve impulses.

Action potential

A nerve impulse consist of a wave of ____ moving away from a point of stimulation

cell body

A neuron has a ___ ___ with mitochondria, lysosomes, a Golgi apparatus, chromatophilic substance containing rough endoplasmic reticulum, and neurofibrils.

sensory sensory interneuron motor effector

A reflex arc includes a ____ receptor, a ____ neuron, a _____ in the spinal cord, a ____ neuron, and a/an ____.

D.) are not completely myelinated

And infants responses to stimuli are coarse and undifferentiated because it's nerve fibers____. A.) have not yet appeared B.) are incapable of carrying impulses C.) have not yet developed connections to the brain D.) are not completely myelinated

True

Astrocytes are thought to provide structural support within the nervous system T/F

If a neuron responds at all, it responds completely. If threshold is reached, the impulse is conducted whenever a stimulus of threshold intensity or above is applied to an axon and impulses carried on that axon of the same strength no matter the intensity.

Define all-or-none response as it relates to nerve impulse conduction.

Myelin sheaths are produced by Schwann cells. These cells wind tightly around axons somewhat like a bandage wrapped around a finger, coating them with many layers of cell membrane that have little or no cytoplasm in them.

Describe how the myelin sheath forms. Pg. 215

See figure 9.4 and pages 214 & 215

Describe the components of a neuron.

The neurons are not in direct physical contact with each other but are separated by a gap called the synaptic cleft. The presynaptic neuron releases a neurotransmitter. the neurotransmitter diffuses across the synaptic cleft and binds to a receptor specific to that neurotransmitter found in the dendrites of the postsynaptic neuron. the action of the neurotransmitter on the postsynaptic cell is either excitatory or inhibitory.

Describe the events that occur at a synapse.

Microglial cells- scattered through CNS and support neurons and phagocytize bacterial cells and cellular debris Oligodendrocytes- align along nerve fibers and provide insulating layers of myelin, called a myelin sheath, around axons with the brain and spinal cord. Astrocytes- found between neurons and blood vessels, provide structural support, join parts by abundant cellular processes and help regulate concentrations of nutrients and ions within tissue. They also form scar tissue that fills spaces following injury to the CNS. Ependymal cells- form an epithelia- like a membrane that covers specialized brain parts and forms inner linings that enclose spaces within the brain and spinal cord.

Distinguish among the types of neuroglia cells in the CNS.

Dendrites carry impulses from other neurons (or from receptors) toward the cell body. Axons transmit the impulse away from the axonal hillock of the cell body and may give off side branches.

Distinguish between an axon and an dendrite.

Sodium Potassium negative positive

Due to active transport, the cell maintains a greater concentration of ____ ions outside and a greater concentration of ____ions inside the membrane. The inside of the membrane has excess ____ charges, while the outside has more ___ charges.

Potassium ions defusing to the outside of the cell membrane

During an action potential, repolarization occurs as a result of

Unmyelinated axon conducts an impulse over its entire surface. A myelinated axon functions differently because myelin insulates and prevents almost all ion flow through the membrane it encloses. Nodes of Ranvier between Schwann cells allow action potentials to occur at the nodes. A nerve impulse traveling along a myelinated axon appears to jump form node to movers faster than an impulse in an unmyelinated axon.

Explain how impulse conduction differs in myelinated and unmyelinated nerve fibers.

They gather information by detecting changes inside and outside the body. They monitor external environmental factors such as light, sound intensities and conditions of the body's internal environment such as temperature and oxygen level. The receptors convert this information into nerve impulses that travel to the CNS. Sensory receptors gather information by detecting changes inside and outside the body. Examples outside the body: touch, temperature of air, and changes in light. Examples inside the body: intestinal pressure causes cramps and chemical receptors in circulatory system monitoring glucose levels, salt levels, and H20 levels. Sensory receptors convert environmental information into nerve impulses which are transmitted to the central nervous system.

How do sensory receptors collect information?

complete depolarization is required for the nerve impulse to be able to travel along the axon

How does all or none relate to nerve impulse transmission?

Nerve impulses from the sensory receptors are brought together (integrated) creating sensations, adding memory or helping produce thoughts, which form perceptions. As a result of the integrative function, we make conscious or subconscious decisions, and then we use motor functions to act on them.

How does the CNS integrate incoming information?

Fill spaces, provides structural framework, produce the components of electrical insulator myelin and carry on phagocytosis.

List the functions of the cells that support neurons

When a neuron is stimulated, its resting potential decreases (becomes less negative because Na+ floods in). If the membrane reaches -55millivolts, it is said to have reached threshold potential. If threshold potential is reached, an action potential results. When threshold is reached, Na+ channels open and Na+ floods into the cell. The membrane potential changes and becomes depolarized. At the same time, potassium channels open to allow potassium ions to leave the cell, the membrane becomes re-polarized and resting potential is reestablished. This rapid sequence of events is the action potential. the active transport mechanism then works to maintain the original concentrations of sodium and potassium ions

List the major events of an action potential.

A.) white

Masses of myelinated nerve fibers appear____. A.) white B.) gray C.) brown D.) transparent

Somatic Nervous System Autonomic Nervous System

Motor functions can be divided into the consciously controlled_____ and the unconscious ______.

True

Myelinated fibers form the white matter in the central nervous system T/F

False

Myelination begins in prenatal development and is complete by the time of birth T/F

False

Neurons are the most abundant cells in the nervous system T/F

False

Nodes of Ranvier occur between adjacent neurons. T/F

Effectors

Parts such as muscles and glands that are capable of responding to nerve impulses are called

True

Release of neurotransmitter from the presynaptic neuron is dependent upon diffusion of calcium ions into the cell T/F

Schwann

Sheaths of _____ cells often enclose the axons outside of the brain and spinal cord

False

Sodium ions pass more easily through the cell membrane than potassium ions T/F

pumps sodium ions out and potassium ions in

Sodium/ Potassium pump: What is its role?

-The cell membrane is selectively permeable. -K+ can pass through the cell membrane more easily than Na+. -Na+ and K+ follow the laws of diffusion. -More K+ diffuses out of the cell than Na+ diffuses into the cell resulting in more positive charges on the outside of the cell than inside the cell. -Inside the cell, there are many large, impermeable, negatively charged proteins and ions that cannot diffuse out of the cell. -At resting potential, there is always more positive ions outside of the cell making the membrane polar (positive on the outside and negative on the inside). -The difference in electrical charge between the two regions is called potential difference or resting potential. -Na+ and K+ pumps maintain resting membrane potential when the neurons are at rest. -The voltage inside a neuron is at rest at -70 millivolts.

Summarize how a nerve fiber becomes polarized.

False

The amount of change in the resting potential of a cell membrane is proportional to the intensity of the stimulus T/F

meninges

The brain and spinal cord are surrounded by membranes called _____ that lie between the bone and the soft tissues.

Neuroglial

The cells within the nervous system that fill spaces and give support to neurons are called ______.

Brain and spinal cord

The central nervous system is made up of the ____ and _____.

D.) dendrites

The cytoplasmic extensions that provide the main receptive services for neurons are _____. A.) neurofibrals B.) Nissl fibers C.) axons D.) dendrites

False

The dendrite arises from a hillock or elevation of the cell body and carries impulses away from the cell body T/F

Resting potential

The difference in electrical charge between the inside and outside of a polarized nerve cell membrane is called the____.

channel proteins

The distribution of ions is determined by the membrane ____ ____ that are selective for certain ions.

synapse synaptic cleft synaptic transmission

The junction between two communicating neurons is called a ____; there exists a _____ between them across which the impulse must be conveyed. _____ is the process by which the impulse in the presynaptic neuron is transmitted across the synaptic cleft to the postsynaptic neuron.

Neurons and Neuroglia

The nervous system is composed of ____ and ____.

Receptors and peripheral

The peripheral nervous system is made up of the ____ and ____ nerves.

resting potential

The separation of charge, or potential difference, is called the ______.

31

The spinal cord consists of __ segments each of which gives rise to a pair of spinal nerves.

1.) CNS(Central Nervous System) -consists of brain and spinal cord 2.) PNS - connect central nervous system to other body parts

What are the two major subdivisions of the nervous system?

Motor neurons carry impulses to effectors which carry out a response. Effectors can be muscles or glands. Motor functions of the peripheral nervous system can be divided into 2 categories: 1.) somatic nervous system- consciously controlled and controls the skeletal muscles 2.) autonomic nervous system- controls involuntary effectors such as smooth muscle, glands, and the heart

What are the two types of motor functions of the nervous system?

neurons and neuroglia

What are two major types of cells that form nervous tissue?

causes enough Na channels to open to bring about complete depolarization

What is a threshold stimulus doing to the membrane?

chromatophilic substances

membranous sacs in cytoplasm of nerve cells that have ribosomes attached to their surfaces

They form a myelin sheath around axons.

What is the function of Schwann cells in peripheral nervous system?

it surrounds the myelin sheaths

What is the function of the neurilemma?

The propagation of action potentials along a nerve axon constitutes the nerve impulse.

What is the relationship between action potential and nerve impulses?

terminal vesicles neurotransmitters cleft

When an impulse reaches the knob-like synaptic ____ of an axon, synaptic ____ release chemicals called _____ into the synaptic ____.

Sodium ions are higher on the outside of its membrane and potassium ions are higher on the inside

Where a nerve fiber is polarized the concentration of_____.

to and from the brain

Where does the spinal cord relay information to?

the middle

Where is gray matter located in the spinal cord?

D.) Nissl cell

Which of the following is not a type of neuroglial cell? A.) astrocyte B.) Oligodendrocyte C.) Ependymal cell D.) Nissl cell

Unmyleinated Myelinated saltatory

____ fibers conduct impulses over their entire membrane surface. _____ fibers conduct impulses from node of Ranvier, a phenomenon called ____ conduction. This conduction is many times faster.

enzymes

____ in synaptic clefts and on postsynaptic membrane rapidly decompose the neurotransmitters after their release.

Potassium Sodium

____ ions pass through the membrane more readily than do ____ ions, making the former a major contributor to membrane polarization.

Sensory Receptors

____ neurons (afferent neurons) conduct impulses from peripheral ____ to the CNS.

Sensory receptors perceptions effectors

_____ at the ends of peripheral nerves gather information and convert it into nerve impulses. When sensory impulses are integrated in the brain as _____, this is the integrative function of the nervous system. Conscious or subconscious decisions follow, leading to motor functions via ____.

nerves

a bundle of axons in the peripheral nervous system

membrane

mening-

microglial cells

are small neuroglial cell that supports neurons and phagocytes

axis

ax-

interneurons

between a sensory neuron and motor neuron; internuncial or association neuron

tree

dendr-

nerve impulse

depolarization and repolarization along an axis

myelin sheaths

fatty layers formed from certain neuroglia that surrounds axons, providing insulation

myelin

fatty material that forms a sheath like covering around some axons

neurofibrils

fine, cytoplasmic threads that extend from the cell bodies into the processes of neurons

small cord or fiber

funi-

a swelling

gangli-

effectors

muscles or glands that affect changes in body

nodes of Ranvier

narrow gaps between schwann cells

neurons

nerve cells

axons

nerve fiber that conducts a nerve impulse away from the neuron cell body

astrocytes

neuroglial cell that connects neurons to blood vessels, support structures, aid in metabolism, and respond to brain injury by filling in spaces

schwann cells

neuroglial cell that surrounds an axon of a peripheral neuron, forming the neurilemma sheath and myelin

ependymal cells

neuroglial cells that line the ventricles of the brain and form choroid plexuses within the ventricles

autonomic nervous system

part of nervous system that controls the viscera

peripheral nervous system

part of the nervous system outside the central nervous system

around

peri-

interweaving

plex-

cell body

portion of nerve cell that includes a cytoplasmic mass and nucleus, and front which nerve fibers extend

dendrites

process of a neuron that receives input from other neurons

feeling

sens-

neurilemma

sheath formed from schwann cells on the exterior of some axons

neuroglial cells

specialized cells of the nervous system that produce myelin, communicate between cells, maintain ionic environment, and nurture the differentiation of neurons. They fill spaces, support neurons, provide structural frameworks, produce myelin, and carry on phagocytosis

sensory receptors

specialized structures associated with the peripheral ends of sensory neurons specific to detecting a particular sensation and triggering nerve impulses in response, which are transmitted to the central nervous system

together

syn-

central nervous system

the brain and spinal cord

sensory neurons

transmits impulses from receptors to central nervous system

motor neurons

transmits impulses from the central nervous system to an effector

oligodendrocytes

type of neuroglial cell that forms myelin in the central nervous system

belly or stomach

ventr-