Introduction to the Nervous System P1 (ANATOMY)

Sensory Receptors

Structures that monitor changes in the internal and external environment.

How is the motor part of the ANS divided?

Sympathetic and Parasympathetic

Both Terminal Boutons and Varicosities Contain:

Synaptic Vesicles Neurotransmitters Neuromuscular Junctions Neuroglandular Synapse

Axon regeneration is easier in the CNS or the PNS

The PNS

Electrical Excitability

The ability to respond to a stimulus and convert it into a nerve impulse.

Integration

The activity in which the nervous system process sensory information by analyzing and storing some of it and by making decisions for appropriate responses.

Neurogenesis

The birth of new neurons from undifferentiated stem cells. Epidermal Growth Factor stimulated cells taken from the brains of adult mice to proliferate into both neurons and astrocytes. Hippocampus makes new neurons.

Neurology

The branch of medicine that deals with the normal functioning and disorders of the nervous system.

Regeneration

The capability to replicate or repair themselves. Mammalian neurons have very limited abilities in this.

Postsynaptic Cell

The cell that receives a signal

Axon Hillock

The cone shaped elevation located on the cell body which links the Axon to the cell body.

Axoplasm

The cytoplasm of an axon.

Demyelination

The loss or destruction of Myelin sheath around axons. It may result from disorderes such as MS or Tay-Sachs, or from medical treatments such as radiation or chemotherapy. Any single episode of demyelination may cause deterioration of affected nerves.

Diverging Circuit

The nerve impulse from one presynaptic neuron causes the stimulation of increasing numbers of cells along the circuit. This has the affect of amplifying the signal.

Afferent System

The part of the PNS that sends messages to the CNS.

Initial Segment Part of Axon

The part of the axon closest to the axon hillock.

Axolemma

The plasma membrane of a axon, it envelopes the Axoplasm.

Somatic Gemmules

The plasma membrane of the neuronal cell body which is bumpy, caused by many small projections, called somatic Gemmules or somatic spines, which increase the surface area available for interactions with other cell.s

Electrical Synapses

The plasma membranes of the presynaptic and postsynaptic neurons are tightly bound by gap junctions that contain connexons. Not common in brain but common in visceral smooth muscles, cardiac muscle tissue, and the developing embryo. They permit very rapid communication and uniform, coordinated movements, such as those required to make a heart beat.

Converging Circuit

The postsynaptic neuron receives nerve impulses from several different sources. IE: A single motor neuron that synapses with skeletal muscle fibers at neuromuscular junctions receives input from several pathways that originate in different brain regions.

Dendrites

The receiving or input portions of the neuron.

Synapses

The site of communication between two neurons or between and neuron and a effector cell.

Neuromuscular Junction

The synapse between a motor neuron and a muscle fibers.

Neuroglandular Synapse

The synapse between a neuron and a glandular cell.

Unipolar Neurons

They are sensory neurons that begin in the embryo as bipolar neurons. Single axon branches a short distance from the soma, on branch (peripheral fiber) carries impulse from source of sensation, the other (central fiber) carries impulse into the spinal cord.

Somatic Motor Neurons

They convey information from the CNS to Skeletal Muscles. (Voluntary)

Somatic Sensory Neurons

They convey information from the sensory receptors of the skin, skeletal muscles, joints, and special senses to the CNS.

Chemical Synapses

They involve the release of a neurotransmitter from a presynaptic neuron, occur between most neurons and between all neurons and effectors (muscle cells & glandular cells).

Nodes of Ranvier

This is a gap in the myelin sheath, they appear at intervals along the axon. Each Schwann cell warps one axon segment between two nodes. Allows for impulses to leap form node to node thus increasing speed.

Synaptic Vesicle

Tiny membrane enclosed sacs that store a chemical called a neurotransmitter.

Collection of nerve fibers in the CNS is called what?

Tract

True or False...Once begun a nerve impulse travels rapidly and at a constant rate.

True.

Multipolar Neurons

Usually have several long dendrites and one axon. Most neurons in the brain and spinal cord are multipolar, as are all motor (efferent) neurons.

Divergence

When a single presynaptic neuron may synapse with several postsynaptic neurons. It permits one presynaptic neuron to influence several postsynaptic neurons (or several muscle fibers of gland cells) at the same time.

Myelination

When axons are covered by Myelin

Can neuroglia divide?

Yes, they continue to divide throughout a persons lifetime.

Astrocytes

[CNS] - Are the largest and most numerous of the neuroglia. They are star shaped cells with lots of arm like processes. They are strong and support neurons, they aid endothelial cells in filtering CSF and make the blood-brain barrier. In the embryo they secrete chemicals that regulate; growth, migration, and interconnections among neurons of the brain. Help maintain chemical balances. Also play a role in learning and memory by influencing the formation of neural synapses.

Ependymal

[CNS] - Cuboidal to Columnar cells in a single layer that possess microvilli and cilia. Line the ventricles of the brain and central canal of the spinal cord. Produce, monitor, and assist in the circulation of CSF. Also the blood-cerebrospinal fluid barrier.

Oligodendrocytes

[CNS] - Resemble astrocytes but smaller and contain fewer processes. Responsible for forming and maintaining the covering around CNS axons.

Microglia

[CNS] - Small cells with slender processes with numerous spine like projections. From Red Bone Marrow and migrate to the CNS. Function as phagocytes. They remove

Schwann Cells

[PNS] - "Neurolemmocytes" - flat cells the encircle PNS axons. They form the myelin sheath around axons. Participate in axon regeneration which is easier in the PNS than the CNS.

Satellite Cells

[PNS] - Flat cells that surround the cell bodies of neurons of PNS ganglia. Provide structural support, regulate the exchange of materials between neuronal cell bodies and interstitial fluid.

Nerve Impulse

"Action Potential" - An electrical signal that travels along the surface of the membrane of a neuron. It begins and travels due to the movement of ions (sodium, potassium) between interstitial fluid and the inside of a neuron through specific ion channels in the neuron's plasma membrane.

Dendritic Gemmules

"Dendritic Spines" - Receptor sites for biding chemical messengers from other cells. These are small bumps or projects found on the dendrites plasma membrane to increase surface area and thus receptor sites.

Neurons

"Nerve Cells" - Possess electrical excitability and convey messages.

Glial Cells

"Neuroglia" or "Glia" - 1/2 the volume of the CNS. They can reproduce and are not involved in impulses. In injury or disease they multiply to fill in the spaces formerly occupied by neurons.

Synaptic End Bulbs

"Terminal Boutons" - The tip of some axon terminals which swell into bulb shaped structures.

Acetylcholine

(ACh) - Released by many PNS neurons and by some CNS neurons. Excitatory neurotransmitter at the neuromuscular junction. It is also known to be a inhibitory neurotransmitter at other synapses.

Gamma Aminobutryric Acid

(GABA) - A amino acid neurotransmitter which is an important inhibitory neurotransmitter. Antianxiety drugs such as diazepam enhance the action of GABA.

Neurolemma

(Sheath of Schwann) - The outer nucleated cytoplasmic layer of the Schwann cell, which encloses myelinated or unmyelinated axons. Only found around axons in the PNS. When a axon is injured it aids in regeneration of the axon by making a regeneration tube that guides and stimulates regrowth of the axon.

What are some Neurotransmitters?

-Acetylcholine -Glutamate -Asparate -Gamma Aminobutryric Acid -Norepinephrine -Dopamine -Serotonin -Neuropeptides -Nitric Oxide -Carbon Monoxide

What are the 4 types of cells in the CNS?

1. Astrocytes 2. Oligodendrocytes 3. Microglia 4. Ependymal

What are the 3 ways that Neurotransmitters are removed?

1. Diffuse Away 2. Destroyed By Enzymes 3. Reuptake and Uptake

3 Main Types of Neuron

1. Interneuron 2. Sensory Neuron 3. Motor Neuron

What are the 3 types of Neurons?

1. Multipolar Neurons 2. Bipolar Neurons 3. Unipolar Neurons

What are the 2 types of cells in the PNS?

1. Schwann Cells 2. Satellite Cells

What are the 3 ways that the PNS is divided?

1. Somatic Nervous System 2. Autonomic Nervous System 3. Enteric Nervous System

How many pairs do cranial nerves have?

12 pairs

How many pairs do spinal nerves have?

31 pairs

Asparate

A amino acid neurotransmitter which has a powerful excitatory effect.

Glutamate

A amino acid neurotransmitter which has a powerful excitatory effect.

Nerve

A bundle of hundreds to thousands of axons (nerve cell fibers)

What is a Nucleus?

A cluster of cell bodies in the CNS

What is a Ganglion?

A cluster of cell bodies in the PNS

Nerve Fibers

A general term for any neuronal process (extension) that emerges from a cell body of a neuron. Process are termed dendrites and axons. Most neurons have multiple dendrites and one axon.

Serotonin

A modified amino acid, and is thought to be involved in sensory perception, temperature regulation, control of mood, appetite, and the onset of sleep.

Dopamine

A modified amino acid, which is active during emotional responses, addictive behaviors, and pleasurable experiences. It also regular upper motor neuron that ultimately affect skeletal muscle tone and some aspects of movement due to contraction of skeletal muscles. One form of schizophrenia is due to accumulation of excess dopamine.

Norepinephrine

A modified amino acid, which plays a role in arousal (awakening from deep sleep), dreaming, and regulating mood.

Neurotransmitters

A molecule released from a synaptic vesicle that excites or inhibits postsynaptic neurons, muscle fibers, or gland cells.

Myelin Sheath

A multilayer lipid and protein covering around a Axon. It electrically insulates the axon of the neuron and increases the speed of nerve impulse conduction.

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.

Endorphins

A neuropeptide that serves as the body's natural pain killer. They have also been linked to improved memory and learning, and to feelings of euphoria.

Neuropeptides

A neurotransmitter consisting of amino acids linked by peptide bonds. Such as endorphins.

Neurologist

A physician who specializes in the diagnosis and treatment of disorders of the nervous system.

Simple Series Circuit

A presynaptic neuron stimulates a single postsynaptic neuron. The second neuron then stimulates another and so on.

Nitric Oxide

A simple gas which is different from all previously known neurotransmitters because it is not synthesized in advance and packaged into synaptic vesicles. Formed on demand, acts immediately. An excitatory neurotransmitter secreted in the brain, spinal cord, adrenal glands, and nerves to penis. May play a role in memory and learning. Also function in immune response and blood vessel dilatation.

Parallel After-Discharge Circuit

A single presynaptic cell stimulates a group of neurons, each of which synapses with a common post synaptic cell. May be involved with precise activities such as math.

Varicosities

A string of swollen bumps found on the tips of some axon terminals.

Axons

A type of nerve fiber. Axons vary in length. The single axon of a neuron carries nerve impulses toward another neuron, a muscle fiber, or a gland cell. Axons are thin, long, cylindrical projections that often joins the cell body at a cone shaped elevation called the Axon Hillock.

White Matter

Aggregations of myelinated and unmylinated axons of many neurons.

Perception

An important integrative function. It is the conscious awareness of sensory stimuli. Perception occurs in the brain.

Stimulus

Any change in the environment that is strong enough to initiate a nerve impulse.

Cytoskeleton Microtubules

Assist in moving materials between the cell body and axon

Neuroglia

Cells that support the activities of the neurons.

CNS

Central Nervous System. Composed of the Brain and Spinal Cord. Processes many different incoming sensory information. Also the source of thoughts, emotions, and memories. Most nerve impulses that stimulate muscles to contract and glands to secrete come from the CNS.

Cytoskeleton Neurofibrils

Composed of bundles of intermediate filaments and microtubules that provide the cell shape and support.

Gray Matter

Contains neuronal cell bodies, dendrites, unmylinated axons, axon terminals, and neuroglia. It appears grayish because the Nissl bodies impart a gray color and there is little or no myelin in these areas.

Parasympathetic

Controls "Rest & Digest" activities. Major regulator in the smooth muscle of the digestive and respiratory systems.

Efferent System

Conveys message from the CNS by way of somatic nervous system (muscles in hand wrist and hand contract and the fingers brush the fly from the face).

Dendrite Branching

Dendrites are normally short, tapering, and highly branched: the greater the branching the greater the surface area of the neuron for receiving synaptic communication from other neurons.

True or False...Most Synapses are two way information transfer centers.

FALSE...Most synapses are one way information transfer centers.

Purkinje Cells

Found in the cerebellum of the brain. Named after the guy who found them.

Pyramidal Cells

Found in the cerebral cortex of the brain. Named after their shape.

Axoaxonic

From presynaptic axon to post synaptic axon.

Axosomatic

From presynaptic axon to postsynaptic cell body (soma)

Collection of nerve cell bodies in the PNS is called what?

Ganglion

Bipolar Neurons

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

Neural Circuits

How the CNS organizes its billions of neurons. Each is a function group of neurons that processes a specific kind of information.

Sympathetic

In general helps support exercise or emergency actions. "Fight or Flight" responses. Major regulator in the smooth muscle of the cardiovascular system.

Trigger Zone

In most neurons, impulses arise at the junction of the axon hillock and the initial segment. This area is called the trigger zone.

Tell me about nerve regeneration.

In the PNS damage to dendrites and myelinated axons may be repair if the cell body remain intact and if the Schwann Cells that produce myelination remain active. In the CNS, little or no repair of damage to neurons occurs. Even when the cell body remain intact, a severed axon cannot be repaired or regrown.

Reverberating Circuit

Incoming impulse stimulates the first neuron, which stimulates the second, which stimulates the third and so on. Branches from later neurons synapse with earlier ones. Thus this arrangement sends impulses back through the circuit again and again. Thought to be involved in; breathing, coordinated muscle activity, waking up, sleeping, and short term memory.

Enteric Plexus

Located in the walls of organs of the GI tract, extensive networks of neurons help regulate the digestive system.

Nervous System

Mass of 2kg(4.5lb) about 3% of total body weight. Composed of a highly organized network of neurons and neuroglia. Composed of the CNS and PNS

Axodendritic

Most synapses between neurons are Axodendritic - from presynaptic axon to postsynaptic dendrite.

Effectors

Muscles or glands that at stimulated by motor neurons which cause them to contract or secrete.

Collection of nerve fibers in the PNS is called what?

Nerve

What aids in regeneration of Myelin in the PNS?

Neurolemma

Sensory Afferent Neurons

Neurons that carry sensory information from sensory receptors into the brain and spinal cord.

Interneurons

Neurons that interconnect with other neurons. Their axons only extend for a short distance and contact nearby neurons in the brain of spinal cord. These neurons make up a majority of the CNS.

What needs to be removed for normal synapse function?

Neurotransmitters after they are used

Can neurons divide?

No they can not undergo mitotic divisions.

Carbon Monoxide

Not formed in advance and formed PRN. Diffuses through cells. A excitatory neurotransmitter produced in the brain in response to some neuromuscular and Neuroglandular functions. May be related to dilation of blood vessels, memory, olfaction, vision, thermoregulation, insulin release, and anti-inflammatory activity.

Collection of nerve cell bodies in the CNS is called what?

Nucleus

What produces Myelin in the CNS?

Oligodendrocytes

Motor Efferent Neurons

Once sensory information is integrated, the nervous system responds via Motor Efferent Neurons. They carry information from the brain toward the spinal cord or out of the brain and spinal cord to effectors through cranial and spinal nerves.

Autonomic Motor Neurons

Part of ANS and Conveys information from the CNS to smooth muscle, cardiac muscle, and glands and cause the muscles to contract and glands to secrete. Divided into Sympathetic and Parasympathetic Divisions.

Autonomic Visceral Sensory Neurons

Part of ANS and Conveys information to the CNS from autonomic sensory receptors, located mainly in the visceral organs (smooth muscle organs of the thorax, abdomen, and pelvis).

Enteric Nervous System

Part of the PNS. "Brain of the Gut" - It consists of over 100 million neurons and can act independent of the CNS. The ENS has both sensory and motor components. Sensory neurons monitor chemical changes of the GI and the stretching of its walls. Motor neurons govern contraction of GI tract and control secretions of the GI. Involuntary.

Somatic Nervous System

Part of the PNS. Composed of Somatic Sensory Neurons and Somatic Motor Pathways. Actions of the SNS are normally voluntary.

Autonomic Nervous System

Part of the PNS. Has sensory and motor components. Composed of Autonomic Visceral Sensory Neurons and Autonomic Motor Neurons (Sympathetic/Parasympathetic Division). Actions of the ANS are involuntary.

PNS

Peripheral Nervous System. Composed of the; Cranial Nerves, Spinal Nerves, Ganglia, Enteric Plexuses in Small Intestine, and Sensory Receptors in Skin (All nervous structures outside of the brain and spinal cord).

Effector

Responds to the impulse from a neuron at the synapse.

What produces Myelin in the PNS?

Schwann Cells

How are the activities of the nervous system divided?

Sensory (input) Integrative (control) Motor (output)

Convergence Circuit

Several presynaptic neurons synapse with a single postsynaptic neuron. This arrangement permits more effective stimulation or inhibition of the postsynaptic neuron.

Ganglia

Small masses of nervous tissue, consisting mainly of neuron cell bodies, that are outside the brain and spinal cord. They are closely associated with brain and spinal nerves.