Nervous System

Nerve

A bundle of hundreds to thousands of axons plus associated connective tissue and blood vessels that lies outside the brain and spinal cord; in PNS

Polarized

A cell that exhibits a membrane potential is said to be ____________________

Excitatory post synaptic potential (EPSP)

A depolarizing postsynaptic potential. Cell is moved towards firing an Action Potential. voltage change approaches threshold Na++ channels opening Occurs when ion channels allow negatively charged ions to move out, and positively charged ions to move in.

Inhibitory postsynaptic potential (IPSP)

A hyperpolarizing postsynaptic potential. Cell is moved farther away from firing an Action Potential. voltage change away from threshold Cl- or K+ channels opening Occurs when more negatively charged ions are added to an already negatively charged receptor cell.

Postsynaptic neuron

A nerve cell that carries a nerve impulse away from a synapse

Presynaptic neuron

A nerve cell that carries a nerve impulse toward a synapse.

Nervous System

A network of billions of neurons and even more neuroglia that is organized into two main division: central nervous system (brain and spinal cord) and peripheral nervous system (nerves, ganglia, enteric plexuses, and sensory receptors outside the central nervous system).

Schwann cells

A neuroglia cell of the peripheral nervous system that forms the myelin sheath and neurolemma around a nerve axon by wrapping around the axon in a jelly-roll fashion. Participate in axon regeneration.

Neuron

A neve cell, consisting of a cell body, dendrite, and an axon. They possess electrical excitability. They are highly irritable, receive stimuli and transmit action potential.

Graded Potential

A small deviation from the resting membrane potential that makes the membrane either more polarized or less polarized.

Node of Ranvier

A space along a myelinated axon between the individual Schwann cells that form the myelin sheath and the neurolemma; appear at intervals along the axon

motor or efferent neurons

Action potentials away from CNS; most are multipolar in structure

Threshold

An action potential occurs in the membrane of the axon of a neuron when depolarization reaches a certain level termed the _____________________.

Action potential

An electrical signal that propagates along the membrane of a neuron or muscle fiber(cell); A rapid change in membrane potential that involves a depolarization followed by a repolarization. Also called a nerve action potential or nerve impulse as it relates to a neuron, and a muscle action potential as it relates to muscle fiber.

Stimulus

Any change in the environment that is strong enough to initiate an action potential.

Ependymal cells

Are cuboidal to columnar cells arranged in a single layer that possess microvilli and cilia. Neuroglia cells that cover choroid plexuses and produce cerebrospinal fluid(CSF); They also line the ventricles of the brain and probably assist in the circulation of CSF; Form the blood-cerebrospinal fluid barrier.

Electrical

At an _______________________ synapse, action potentials (impulses) conduct directly between the plasma membranes of adjacent neurons through structures called gap junctions. Less common

Myelinated axons

Axons with myeline sheath covering.

Unmyelinated axons

Axons without myelin sheath covering

Brain and Spinal cord

Central nervous system consists of:

Motor (bundle of motor axonss), sensory (bundle of sensory axons), and mixed (bundle of motor and sensory axons)

Classifications of nerves

nerves, ganglia, enteric plexus, and sensory receptors

Components of PNS include

Brain, spinal cord, nerves, sensory receptors

Components that make up nervous system

Autonomic nervous system

Consists of (1) sensory neurons that convey information to the CNS from autonomic sensory receptors, located primarily in visceral organs such as the stomach and lungs, and (2) motor neurons that conduct nerve impulses from the CNS to smooth muscle, cardiac muscle, and glands. motor responses are not normally under conscious control , so actions are involuntary.

Somatic nervous system

Consists of (1) sensory neurons that convey information to the CNS from somatic receptors in the head, body wall, and limbs and from receptors for the special senses of vision, hearing, taste, and smell, and (2) motor neurons that conduct impulses from the CNS to skeletal muscles only; action of this part of PNS is voluntary since actions can be continuously controlled.

Peripheral nervous system

Consists of all nervous tissue outside the CNS

Cell body (perikaryon) or soma

Contains a nucleus surrounded by cytoplasm that includes typical cellular organelles such as lysosomes, mitochondria, and a Golgi complex.

Gray matter

Contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia. Located outside of brain (peripheral), and located on inside of spinal cord (central).

sensory or affarent neurons

Convey action potentials toward CNS; most are unipolar in structure

Voltage and resistance

Current is dependent upon which two factors?

Voltage;Resistance

Current is directly related to __________________, and inversely related to _________________ .

Complete insensitivity exists to another stimulus. It is present from beginning of action potential until near end of repolarization.

Describe the absolute refractory period

Repolarization

During the ____________________ stage, the membrane potential is restored to the resting state of -70mV. Returns to more negative state.

Depolarization

During the ________________________ stage, the negative membrane potential becomes less negative, reaches zero, and then becomes positive.

Faster communication and Synchronization

Electrical synapses have two main advantages:

Enteric Plexus

Extensive networks of neurons located in the walls of organs of the gastrointestinal tract.

Myelination, axon diameter, and Temperature

Factors that effect the speed of propagation

Satellite cells

Flat neuronal cells that surround cell bodies of peripheral nervous system ganglia to provide structural support and regulate the exchange of material between a neuronal cell body and interstitial fluid.

Current

Flow of charge

Current

Flow of ions across the membrane

after-hyperpolarizing phase

Following the repolarizing phase there may be an __________________________ _____________, during which the membrane potential temporarily becomes more negative than the resting level.

Chemical synapse

Function synapse that is specialized for release and reception of neurotransmitters.

sensory function, integrative function(CNS), and motor function

Functions of the nervous system

Potential energy

Generated by separated charges

Postsynaptic potential

Graded potential (change) that develops in postsynaptic membrane in response to neurotransmitter

Unipolar

Have dendrites and one axon that are fused together to form a continuous process that emerges from the cell body. The dendrites of these neurons function as sensory receptors that detect a sensory stimulus such as touch, pressure, pain, or thermal stimuli.

Bipolar neurons

Have one main dendrite and on axon. They are found in the retina of the eye, the inner ear, and the olfactory area of the brain. Rarest

Sympathetic division

Helps support exercise or emergency actions, the "fight or flight" responses. increases heart rate

all-or-none principle

If a stimulus depolarizes a neuron to theshold, the neuron fires at its maximum voltage (all); if threshold is not reached, the neuron does not fire at all (none). Given above threshold, stronger stimuli do not produce stronger action potentials

Selective;charge;size

Ion channels are ________________, they select ions based on the _____________, _______________, and their affinity for water

Inhibitory Neurotransmitter

Kind of neurotransmitter that causes hyperpolarization of postsynaptic membranes; supresses action potentials

Interneurons or association neurons

Located within CNS between sensory and motor neurons. Process incoming sensory information from sensory neurons and then elect a motor response by activating the appropriate motor neurons; Within CNS from one neuron to another; most are multipolar in structure

GABA

Most common neurotransmitter that we find in our CNS is

sensory perceptions, mental activities, stimulating muscle movements, stimulation of glands

Nervous system is responsible for

Astrocytes, oligodendrocytes, microglia, and ependymal cells

Neuroglia of CNS

Schwann cells, and Satellite cells

Neuroglia of PNS

Graded potentials, and action potentials

Neurons communicate with each other using what two types of electrical signals?

Motor function

Once sensory information is integrated, the nervous system may elicit an appropriate motor response by activating effectors (muscles and glands) through cranial and spinal nerves. Stimulation of the effectors causes muscles to contract and glands to secrete.

Mechanically-gated channels

Opens and closes in response to mechanical stimulation in the form of vibration (such as sound waves), touch pressure, or tissue stretching. They are found in auditory receptors in the ears, in receptors that monitor stretching of internal organs, and in touch receptors and pressure receptors in the skin

Ligand-gated channels

Opens and closes in response to the binding of a ligand (chemical) stimulus such as neurotransmitters, hormones, and particular ions. They are located in the dendrites of some sensory neurons, such as pain receptors, and in dendrites and cell bodies of interneurons and motor neurons

Voltage-gated channel

Opens in response to a change in membrane potential(voltage). They participate in the generation and conduction of action potentials in the axons of all types of neurons.

Cranial nerves, and spinal nerves

Peripheral nervous system consists of:

The CNS

Processes many different kinds of incoming sensory information, and is the source of thoughts, emotions, and memories. Most signals that stimulate muscles to contract and glands to secrete originate here.

Axon

Propagates nerve impulses toward another neuron, a muscle fiber, or a gland cell; its a long, thin, cylindrical projection that often joins to the cell body at a cone shaped elevation called the axon hillock.

Continuous conduction

Propagation of an action potential (nerve impulse) in a step-by-step depolarization and repolarization of each adjacent area of an axon membrane. Occurs in unmyelinated axons and in muscle fibers.

detecting internal and external stimuli. Then sensory information is sent to CNS by cranial and spinal nerves(SNS)

Sensory function is responsible for

exteroceptors

Sensory receptors located externally are called

interoceptors

Sensory receptors located internally are called

Ganglia

Small masses of nervous tissue, consisting primarily of neuron cell bodies, that are located outside of the brain and spinal cord. They are closely related to cranial and spinal nerves

Neurology

Study of the nervous system

neuroglia or glial cells

Support and protect neurons; maintains the interstitial fluid that bathes them.

Multipolar structure

The PNS is composed of which neural structural classification

Postsynaptic cell

The cell that receives a signal.

Resistance

The cellular plasma membrane in flow of ion plays the role of ________________________

properties of the receptor; neurotransmitter

The effect of a neurotransmitter on the postsynaptic membrane depends on the _________________ ______ _____ _________________, not on the nature of the ____________________

Leak channels, ligand-gated channels,mechanically gated channels, and voltage-gated channels.

The electrical signals produced by neurons and muscle fibers rely on four types of ion channels:

Leak Channels

The gates randomly alternate between open and closed positions. They are found in nearly all cells, including the dendrites, cell bodies, and axons of all types of neurons

postive and negative ions

The imbalance of ______________________________, gives us our resting membrane potential

Sympathetic division, and parasympathetic division

The motor divisions of the ANS consist of two branches:

The central nervous system and the peripheral nervous system

The nervous system is divided into two main subdivisions:

Integrative function

The nervous system processes sensory information by analyzing it and making decisions for appropriate responses.

Negative;positive

The net charge inside the cell is __________________, and the net charge outside the cell is _____________________.

Refractory Period

The period of time after an action potential begins during which an excitable cell cannot generate another action potential in response to a normal threshold stimulus.

Relative refractory period

The period of time during which a second actin potential can be initiated, but only by a larger than normal stimulus. It coincides with the period when the voltage-gated K+ channels are still open after inactivated Na+ channels have returned to their resting state.

Dendrites

The receiving or input portions of a neuron; usually are short, tempering, and highly branched.

synapse

The site of communication between two neurons or between a neuron and an effector cell (muscle cell of glandular cell) is called a _______________

Saltatory conduction

The special mode of action potential propagation that occurs along myelinated axons, occurs because of the uneven distribution of voltage-gated channels.

Foramen magnum of the occipital bone

The spinal cord is connected to the brain through the:

Sensory Receptor

This term refers to a structure of the nervous system that monitors changes in the external or internal environment.

Depolarization, depolarization, and opening of ion channels

Transmittance of information is done by ____________________ ,_________________, and ______________________

Somatice nervous system (SNS), and autonomic nervos system (ANS)

Two subcategories that make up the PNS

Axoaxonic

Type of synapse between axon to axon. It will stop stuff from happening on the true synapse

axosomatic

Type of synapse between axon to cell body. A common synapse connection

axodendritic

Type of synapse that connects exon to dendrite. The most common

Multipolar

Usually have several dendrites and one axon. Most neurons in the brain and spinal cord are of this type, as well as all motor neurons. Most common

C axons

What axon diameter are sensory neurons classified as?

Action potentials propagate more rapidly along myelinated axons than along unmyelinated axons

What happens to the speed of propagation when there is a large amount of myelination?

There is a release of energy, and work is done as a result

What happens when opposite charges come together?

Passive leaking channels

What is the name of the channels that are always open?

Larger diameter axons propagate action potentials fasten than smaller ones due to their larger surface areas

What is the relationship that axon diameter has with speed of propagation?

Axons propagate action potentials at lower speeds when cooled.

What is the relationship that temperature has with speed of propagation?

-55 mV

What is the threshold of action potential?

Continuous

What kind of conduction do unmyelinated axons exhibit?

Saltatory

What kind of conduction to myelinated axons exhibit?

Chemical

What type of functional synapse is more common?

In cardiac muscle, and many types of smooth muscle, and in brain

Where are electrical synapses found?

In the dendrites of some sensory neurons, such as pain receptors, and in dendrites and cell bodies of interneurons and motor neurons

Where are ligand-gated channels located?

In auditory receptors in the ears, in receptors that monitor stretching of internal organs, and in touch receptors and pressure receptors in the skin

Where are mechanically-gated channels found?

12 pairs ;31 pairs

________ pairs of cranial nerves emerge from the brain, and _________ pairs of spinal nerves emerge from the spinal cord.

Cells

____________ have a charge due to imbalances in negatively and positively charged ions inside and outside the cell

Graded Potentials

________________ __________________ are used for short distance communication only. There is a change in RMP

Myelin

_________________ protects and insulates axons from one another, Not continuous.

Action Potentials

__________________ _________________ allow communication over long distances within the body. There is a change in RMP

Energy

___________________ is required to keep charges separate

Ganglion

a group of neuronal cell bodies lying outside the central nervous system; in the PNS

norepinephrine

a hormone secreted by the adrenal medulla that produces actions similar to those that result from sympathetic stimulation

Astrocytes

a neuroglia cell having a star shape that participates in brain development and the metabolism of neurotransmitters, helps form the blood-brain barrier, helps maintain the proper balance of K+ for generation of nerve impulses and provides a link between neurons and blood vessels.

Oligodendrocytes

a neuroglia cell that supports neurons and produces a myelin sheath around axons of neurons of the CNS.

Muscle action potential

an action potential in a muscle fiber is called ?

White matter

composed primarily of myelinated axons. Located inside the brain (central), and outside the spinal cord (peripheral).

Excitatory neurotransmitter

kind of neurotransmitter that causes depolarization of postsynaptic membranes; promotes action potentials

Myelin sheath

multilayered lipid and protein covering, formed by Schwann cells and oligodendrocytes, around axons of many peripheral and central nervous system neurons. Increases the speed of nerve impulse conduction.

Microglial cells or Microglia

small neuroglial cells with slender processes that give off numerous spikelike projections. They carry on phagocytosis

Parasympathetic division

takes care of "rest and digest" activities. Slows down heart beat

Electrical excitability

the ability to respond to a stimulus and convert it into an action potential

Coulomb's Law

the force of attraction or repulsion acting along a straight line between two electric charges is directly proportional to the product of the charges and inversely to the square of the distance between them

Ohm's law

the law that for any circuit the electric current is directly proportional to the voltage and is inversely proportional to the resistance.

At a neuromuscular junction, Axon to gland

what are examples of axosomatic synapse

Resting membrane potential

work;voltage; charge at rest