Nervous System PP #1

Function of the Nervous System:

Communication

What system has the same function as the Nervous System?

Endocrine System

What does the Nervous System consist of?

Brain, Spinal Cord, & Nerves

Organization of the Nervous System:

Organized to detect changes in internal & external environments, evaluate the information, and initiate an appropriate response.

What are the subdivided smaller systems?

Central Nervous System & Peripheral Nervous System

Somatic Nervous System & Autonomic Nervous System

Which system is the structural and functional center of the entire nervous system?

Central Nervous System

Which system consist of the brain and spinal cord?

Central Nervous System

Which system integrates sensory information, evaluates it, and initiates an outgoing response?

Central Nervous System

Which system has the nerves that lie in the outer regions of the nervous system?

Peripheral Nervous System

Which system uses cranial & spinal nerves that originate in the brain/spinal cord that lies in other regions?

Peripheral Nervous System

Somatic Nervous System:

Somatic motor divison carries information to the somatic effectors.

What are the somatic effectors?

Skeletal Muscles

What division has somatic sensory division that carries feedback information to somatic integration centers in the CNS?

Somatic Nervous System

Autonomic Nervous System:

Efferent Division of ANS carries information to the autonomic or visceral effectors (smooth & cardiac muscles and glands).

Which division does the sympathetic & parasympathetic division apart of?

Autonomic Nervous System

Sympathetic Division:

Prepares the body to deal with immediate threats to the internal environment; produces fight or flight response.

Parasympathetic Division:

Coordinates the body’s normal resting activities; sometimes called the rest and repair division/

What is the function of the Visceral Sensory Division?

Carries feedback information to autonomic integrating centers in the CNS.

Afferent Divison:

Consist of all incoming sensory pathways.

Efferent Division:

Consist of all outgoing motor pathways.

What are the two main cell types of the CNS?

Neurons (Nerve Cells)

Neuroglia (Glial Cells)

Neurons:

Excitable cells that initiate and conduct impulses that make possible all nervous system functions.

What are the components of Neurons?

Cell Body

Cytoskeleton

Dendrite

Axon

Cell Body (Perikaryon)

Contains organelles including mitochondria, rough endoplasmic reticulum, and the Golgi apparatus.

Cell Body: Some protein molecules serves as what to send signals from one neuron to another & are packaged into vesicles?

Neurotransmitters

Cell Body: Other proteins serves to maintain and regulate what?

Nerve Fibers

Cytoskeleton:

Made of microtubules and microfilaments that allows the rapid transport of small organelles such as vesicles & mitochondria.

Dendrites:

Each neuron has one or more dendrites, which branch from the cell body and conducts nerve signals to the cell body of the neuron.

Dendrites: Receptors

Distal ends of dendrites of sensory neurons.

Axons:

A single process, sometimes covered by a fatty layer called a myelin sheath.

A fatty layer that covers nerves?

Myelin Sheath

What increase the velocity of impulse conduction?

Myelin

Axon conducts nerves impulses _____ from the cell body of the neuron.

Away

Functional regions of the Neuron:

Input Zone

Summation Zone

Conduction Zone

Output Zone

Input zone:

Dendrite & cell body

Summation Zone:

Axon hillock

Conduction Zone:

Axon

Output Zone:

Telodendria & synaptic knobs of axon.

Classification of Neurons: Structural Classification

According to number to processes extending from cell body.

Multipolar Classification:

One axon & several dendrites

Bipolar Classification

Only one axon and one dendrite; least numerous kind of neuron.

Unipolar (Pseudounipolar) Classification:

One process comes off neuron cell body but divides almost immediately into two fibers (central and peripheral fibers).

What are the two fibers included in the Unipolar Classification:

Central & Peripheral Fibers.

Functional Classification: Afferent (Sensory) Neurons

Conducts impulses to spinal cord or brain.

Classification of Neurons: Efferent (Motor) Neurons

Conduct impulses away from spinal cord or brain toward muscles or glandular tissue.

Classification of Neurons: Interneurons

A connector

Glia:

Aka neuroglia; glial cells support the neurons.

How many major types of glia are there?

5

What are the 5 major types of glia?

Astrocytes

Microglia

Ependymal Cells

Oligodendrocytes

Schwann Cells

Astrocytes: CNS

Form tight sheaths around brain capillaries, which, with tight junctions between capillary endothelial cells, constitutes the blood brain barrier; transfers nutrients from blood to neurons. (STAR SHAPED)

Microglia: CNS

Small stationary cells; carryout phagocytosis if inflammation in brain.

Ependymal Cells: CNS

Some produce fluid (cerebrospinal fluid), others aid in circulation, they form thin sheets that line fluid filled cavities in the CNS.

Oligodendrocytes: CNS

Smaller than astrocytes with less processes, hold nerve fibers together and produce the myelin sheath.

Schwann Cells: PNS

Found only in peripheral neurons; support nerve fibers & form myelin sheaths; Nodes of Ranvier are where saltatory conduction occurs; satellite cells (Schwann cells) that support cell body.

Neurilemma is formed by:

Cytoplasm of Schwann cell wrapped around the myelin sheath; essential for nerve growth.

Nodes of Ranvier:

Myelin sheath gaps

Neuronal sheath:

Myelin sheath plus the neurilemma (whole Schwann wrapping around the axon).

Satellite cells:

Schwann cells that cover and support cell bodies in the PNS.

Reflex Arc:

A signal conduction route to and from the CNS, with the electrical signal beginning in receptors & ending in effectors.

Three-Neuron Arc: (Reflex Arc)

Most common that consists of afferent neurons, interneurons, and efferent neurons

Two Neuron Arc: (Reflex Arc)

Simplest form; consist of afferent & efferent neurons

Synapse:

Where nerve signals are transmitted from one neuron to another.

What are the two types of synapses?

Electrical and Chemcial

Which synapse is more typical in adults?

Chemical Synapses

Location of Chemical Synapses:

Located at the junction of the synaptic knob of one neuron and the dendrites or cell body of another neuron.

Nerves:

Bundles of peripheral nerve fibers held together by several layers of connective tissue.

Endoneurium:

Delicate layer of fibrous connective tissue surrounding each nerve fiber.

Perineurium:

Connective tissue holding together fascicles (bundles of fibers) that protects from a foreign substances.

Epineurium:

Fibrous coat surrounding numerous fascicles and blood vessels to form a complete nerve.

Tracts:

Within the CNS, bundle of nerve fibers are called this instead of nerves.

White Matter of PNS:

Myelinated Nerves

White Matter of CNS:

Myelinated Tracts

Gray Matter:

Composed of cell bodies and unmyelinated fibers

Gray Matter in CNS:

Nuclei

Gray Matter in PNS:

Ganglia

Mixed nerves:

Contain both sensory and motor neurons

Sensory Nerves have:

Predominantly sensory neurons.

Motor neurons have:

Predominantly motor neurons

Which type of neurons are incapable of cell division; therefore damage to nervous tissue can be permanent.

Mature Neurons

What has limited capacity to repair themselves?

Neurons

What happens if the damage is not extensive with the repair of nerve fibers?

The cell body and neurolemma are intact, and scarring has not occurred, nerve fibers can be repaired.

Membrane Potentials: All living cells maintain a:

Difference in the concentration of ions across their membranes.

Membrane Potential:

Slight excess of positively charged ions on the outside of the membrane and slight deficiency of positively charged ions on the inside of the membrane.

Potential:

Difference in electrical charge; called this because its a type of stored energy.

Polarized Membrane:

Membrane that exhibits a membrane potential

Magnitude of potential difference between the two sides of a polarized membrane is measured in:

Volts (V) or Millivolts (mV).

The sign of a membranes voltage indicates what?

The charge on the inside surface of a polarized membrane.

Resting Membrane Potenital:

Membrane potential maintained by a non-conduction neuron’s plasma membranes; typically ~70 mV; Membrane’ selective permeability characteristics help maintain a slight excess of positive ions on the outer surface of the membrane.

Sodium Potassium Pump:

Active transports mechanism in plasma membrane that transports sodium (Na+) and potassium (K+) ions in opposite directions and at different rates.

In the sodium potassium pump, it maintains an:

Imbalance in the distribution of positive ions, resulting in the inside surface becoming slightly negative compared with its outer surface.

Local Potentials:

Slight shift away from the resting membrane in a specific region of the plasma membrane

Excitation:

When a stimulus triggers the opening of additional Na+ channels, allowing the membrane potential to move toward zero (depolarization)

Inhibition:

When a stimulus triggers the opening of additional K+ channels, increasing the membrane potential (hyper polarization).

Graded Potentials:

Local potentials called this because the magnitude of deviation from the resting membrane potential is proportional to the magnitude of the stimulus.

Action Potential:

The membrane potential of a neuron conducting an impulse; also known as a nerve impulse.

Mechanism that produces the action potential:

When an adequate stimulus triggers stimulus gated Na+ channels to open, allowing Na+ to diffuse rapidly into the cell, which produces a local depolarization.

Mechanism that produces the action potential: As threshold potential is reached:

Voltage gated Na+ channels open and more Na+ enters the cell, causing further depolarization.

The action potential is an:

All or None response

Mechanism that produces the action potential: Voltage gated Na+ channels:

Stay open for only about 1 ms before they automatically close.

Repolarization:

After action potential peaks, membrane begins to move back toward the resting membrane potential when K+ channels open, allowing outward diffusion of K+