Chapter 11 Nervous system

how many mV is the resting state?

-70

What are the three requirements for transmembrane potential?

1) anything tht alters ion concentrations on the 2 sides of membranes 2) anything that changes membrane permeability to any ion

What are the three characteristics of an axon

1) it generates and conducts an impulse 2) when large it is heavy myelinated 3)it has a uniform diameter and is indistinguishable microscopically from an Axon

What are the special characteristics of neurons

1.They have extreme longevity-can function over a lifetime 2. They are amitotic-lose their ability to divide & cannot be replaced if destroyed 3.high metabolic rate & require continuous oxygen and glucose

What is a Unipolar neuron

A neuron that has a single process that emerges from the cell body

What is depolarization? What channels are open and closed?

A reduction in membrane potential where the inside of the membrane becomes less negative. Voltage gated channels of Na+ are open and voltage gated K+ channels are closed

What is an action potential

A reversal in membrane potential(graded potential) which causes an electrical impulse that propagates along the axon to trigger synapse activity

What is continuous conduction

A type of AP propagation where the channels are adjacent to each other and conductor is slow.

What is saltatory conduction/propagation?

A type of conduction where APs are triggered at the nodes

what is continuous conduction/propagation?

A type of conduction where APs are triggered at unmylinated axons

What is multiple sclerosis?

And autoimmune disease in which Myelin sheaths in the CNS are destroyed and reduced to nonfunctional lesions called the sclerosis

What is the most abundant and most versatile neuroglia cell?

Astrocyte

What type of neuroglia cells are in the CNS

Astrocytes, microglia, ependymal and oligodendrocytes.

Each neuron has only one..

Axon

What are the two factors that affect the rate of impulse propagation

Axon diameter and the degree of myelination

What are unmyelinated fibers

Axons bearing a myelin sheath and conduct nerve impulses SLOWLY

What is myelinated fibers and its function?

Axons bearing a myelin sheath that conduct nerve impulses RAPIDLY

Why are there voltage decays in bare plasma membrane

Because the current leaks across the membrane and there is no voltage gated channels

What are neurofibrils and its function

Bundles of intermediate filaments (neurofilaments) . Function; maintains cell shape and integrity

What are tracts?

Bundles of neuron processes in the CNS

what is the somatic nervous system and what is it also known as and why?

Composed of somatic motor nerve fibers that conduct impulses from the CNS to skeletal muscles. Also known as the voluntary nervous system b/c it allows us to consciously control our skeletal muscles

What is parasympathetic division

Conserves energy and promote housekeeping functions during rest (part of the autonomic nervous system)

What is the autonomic nervous system and what is it also known as and why?

Consist of visceral Motor nerve fibers that regulate the activity of smooth muscle cardiac muscles and glands. Also known as involuntary nervous system because you cannot control activities such as pumping the heart

What are the two types of neuron processes

Dendrites and axons

What do axons depend on

Depends on its cell body to renew the necessary proteins and membrane components and on efficient transport can isms to distribute them

What are group C fibers

Fiber is in the autonomic nervous system motor fibers serving the visceral organs that has the smallest diameter and are unmyelinated

Where do you find unipolar neurons and what do they function as?

Found in ganglia in the PNS where they function as sensory neurons

Clusters of cell bodies in the PNS that lie along the nerves are called

Ganglia

What is another name for neuroglia cells

Glia cells

What is lipofuscin? What is it also called

Golden brown pigment that's a by product of lysomal activity. Aka aging pigment b/c it accumulates in neurons of elderly individuals

The _____ the resistance, the ____ the current

Greater, smaller

The greater the difference in charge between 2 points the ____ the voltage

Higher

How is voltage measured

In either volts or millibolts and is always measured between 2 points called potential difference or potential

What are myelin sheaths

Insulating coverings

The _____ the axon diameter, the faster it conducts impulses

Larger

The least amount of difference in charge between 2 points, the _____ the voltage

Lower

What is the sympathetic division

Mobilizes body systems during activity (part of the autonomic nervous system)

What are group A fibers?

Mostly somatic sensory and motor fibers serving the skin skeletal muscles and joints and they have the largest diameter and take my insurance and conduct impulses at high speeds

What is retrograde movement?

Movement away from the Axon terminal that includes organelles that need to be returned to the somebody for degration or recycling

What is anterograde movement?

Movement toward the Axon terminal that includes mitochondria cytoskeletal elements membrane components and enzymes

What is the major type of neuron in the CNS

Multipolar neuron

What is the most common type of neuron in humans

Multipolar neuron

What increases the rate of AP propagation and why

Myelin sheaths b/c it acts as an insulator preventing almost all leakage of charge from the Axon and allowing the membrane voltage to change more rapidly

What are group B fibers

Myelinated fibers of intermediate diameter that transmit impulses at the average speed and it includes autonomic nervous system,motor fibers serving the visceral organs and visceral sensory fibers

What is gray matter

Nerve cell bodies and unmyelinated fibers

Any long axon is called a

Nerve fiber

What are bundles of neuron processes called in the PNS

Nerves

What 2 cells make up the nervous tissue

Neuroglia - supporting cells that surround and wrap the neurons Neurons-excitable nerve cells that transmit electrical signals

What are Schwann cells? What is it also known as?

Neuroglia cells tht surround and form myelin sheaths around nerve fibers in the PNS. Aka neurolemmocytes

Where are multipolar neurons

Neurons with three or more processes one being the axon and the rest dendrites

What are bipolar neurons and where are they found

Neurons with two processes a axon and a dendrite that extend from opposite sides of the cell body, found in some of the special sense organs such as the eye

Clusters of the cell bodies in the CNS are called

Nuclei

What cells form the CNS myelin sheath

Oligodendrocytes

What is a neuron cell body also called

Perikaryon or soma

What part of the cell body acts as part of the receptor region that receives info from other neurons

Plasma membrane

What is a axolemma?

Plasma membrane of an axon

What is the function of oligodendrocytes

Produce myelin sheaths and line up the thicker neurons in the CNS

What is saltatory conduction ?

Propagation along myelinated axons

What is the function of myelin sheaths

Protects, electrically insulates fibers and it increases the speed of transmission of nerve impulses

What is another word for Unipolar neurons and why is it called that?

Pseudounipolar neurons b/c they originate as bipolar neurons

What replaces dendrites in Unipolar neurons?

Receptive endings (sensory terminals) at the end of the peripheral process

What is white matter

Regions of the brain and spinal cord containing dance collections of myelinated fibers

What is the Ohms law?

Relationship between Voltage current and resistance which tells us that current is directly proportional to voltage and it tells us that current is inversely related to resistance

Myelin sheaths are formed by what in the PNS

Schwann cells

what are the three functions of the nervous system?

Sensory input- process in which gathered info from sensory receptors that monitors changes in the inside and the outside of the body Integration- process in which the nervous system processes & interprets sensory input and decides what should be done at each moment Motor output- the response which happens by activating effector organs (muscles,glands)

The _____ the axon diameter, the slower it conducts impulses

Slower

What is the function of the astrocyte

Support and brace the neurons and anger them to their blood capillaries. They help determine couple a permeability and g

Terminal branches are also called what?

Telodendria, axon terminals, synaptic knobs, or boutons.

What part if the neuron is the biosynthetic center

The cell body

What is a current

The flow of electrical charge from one point to another and can be used to do work ex. Power a flashlight

What is resistance

The hinderance to charge flow provided by substances through which the current must pass

What is the all or none phenomenon

The idea that AP either happens completely or doesn't happen at all

What is the relative refractory period

The interval following the absolute refractory in which most Na+ channels have returned to their resting state and some k+ Channels are still open aand the membrane will not respond to an additional stiumuli

Where is the nerve impulse generated in a motor neuron

The junction of an axon hillock and axon

What are dendrites?

The main receptive and input regions that provide surface area for receiving signals from other neurons

What is a voltage?

The measure of potential energy generated by separated charges

What is the nissl body and what is another name for it

The rough ER in the cell body of a neuron. Aka chromatophilic substance.

What is the absolute refractory period

The time when the Na+ channels open until the Na+channels begin to reset to their original resting state and the membrane will not respond to an aadditional stimuli

Why are myelin sheaths good electrical insulators

They have no channel and carrier proteins

What type of neuron is found mainly in the PNS and the spinal cord and cranial nerves

Unipolar neuron

What are the two factors that determine the amount of charge that moves between the two points?

Voltage and resistance

What triggers chemically gated or ligand gated channels to open

When the appropriate channel(neurotransmitter) binds

What is repolarization

When the internal negativity and electrical conditions of the resting neuron is restored. However it does NOT restore resting ionic conditions

What is hyperpolarization? What channels are open and what channels are closed?

When the membrane potential increases. becoming more negative than the resting potential. Some K+ channels remain open and Na+ channels are close.

When is a membrane polarized?

When the potential difference in a resting neuron (aka resting membrane potential)

What is a postsynaptic potential

When the stimulus is a neurotransmitter released by another neuron the graded potential is called the postsynaptic potential

What is the resting membrane potential?

all gated channels are closed and only the leakage channels are open

Organelles for degradation in the axon, are moved by

anterograde

which cell maintains a blood brain barrier in the CNS

astrocytes

what are collaterals?

branches of a single axon that emerge on the nodes of Ranvier

What triggers voltage gated channels to open and close

changes in the membrane potential

what is multiple sclerosis?

disorder in which myelin is destroyed causing loss of motor activity

What are somatic fibers

efferent division sensory fibres conveying impulses from skin, skeletal muscles and joints to the CNS

which cell lines the central canal of the spinal cord and the ventricles of the brain?

ependymal cells

During which stage of action potential generation are both of the voltage Na+ and K+ channels opened?

hyperpolarization

where are neurotransmitters released?

in the presynaptic membrane

what type of neurons makes up 99% of the body's neurons

interneurons (association neurons)

what causes faster propagation

larger axon and mylination

what is the function of the sodium potssium atpase pump?

maintains resting potential by balancing the passive forces of diffusion and carries 3 Na+ out and 2 K+ in

what are spinal nerves

nerves that carry impulses to & from the spinal cord

what are cranial nerves

nerves that carry impulses to and from the brain

what is the basic structural unit of the nervous system?

neurons

what division of the autonomic nervous system has a relaxing effect?

parasympathetic division

What is the peripheral nervous system (PNS) and its function?

part of the nervous system outside the CNS and consist mainly of nerves(bundles of axons) that extend from the brain and spinal cord. Function is to serve as the communication lines that link all parts of the body to the CNS

What is the central nervous system (CNS) and its function? what is it also know as?

part of the nervous system that contains the brain and the spinal cord in the dorsal body cavity. Function is integration and dictates motor responses based on reflexes, current conditions, & past experiences. also known as the command center and integrating center of the nervous system

Which of the following substances plays the major role in generating the membrane potential of a neuron

potassium

what are the types of neuroglia found in the PNS

sattelite cells and schwann cells

what are the two subdivisons of the peripheral nervous system?

sensory afferent division - consist of nerve fibers(axons) that convey impulses to the central nervous system from sensory receptors located throughout the body motor efferent division - consists of transmission of impulses from the CNS to effector organs (muscles, glands) in which activate the muscles to contract and glands to secrete

what are visceral afferent fibers?

sensory fibers that transmit input from visceral organs to the CNS

what are the two parts of the motor efferent division?

somatic nervous system- composed of somatic nerve fibers that make impulses from the CNS to skeletal muscles.

what division of the autonomic nervous system has a stimulating effect?

sympathetic division

What are graded potentials? where are they produced?

temporary change in resting potential caused by a stimulus that can be either depolarization or hyperpolarization. Produced in postsynaptic membrane.