Chapter 12 - Nervous System Terminology

BIO 047

The nervous system is also known as the __________ system. Why?

It is also known as the master control and communication system because it controls the working of all other organ systems.

What are the 3 overlapping functions of the nervous system?

1. Sensory input - sensory receptors monitor changes in and outside of the body

2. Integration / processing - processes & interprets sensory input and makes decisions through integration

3. Motor output - Dictates a response by activating effector organs

“Nerve fibers” strictly refer to what portion of the neuron?

The long axon portion

Describe the basic divisions of the nervous system & their structures.

• Central Nervous System (CNS) - brain & spinal cord

• Peripheral Nervous System (PNS) - nerves extending from the brain and spinal cord, ganglia

Neuronal cell bodies are normally found in the CNS, however, there is an exception for _____.

Ganglia. Ganglia are clusters of neuronal cell bodies found within the PNS.

Motor signals innervate _____.

Muscles & glands

The somatic body region includes organs lying _____ the ventral body cavity and is under _____ control.

Outside (ex. skin, skeletal muscles, glands), voluntary

The visceral body region includes organs lying _____ the ventral body cavity and is under _____ control._

Within (ex. heart, lungs), involuntary

Name the sensory input subdivisions.

• Somatic sensory

• Visceral sensory

Name the motor output subdivisions.

• Somatic motor

• Visceral motor (ANS)

The visceral motor system (ANS) can be further divided into _____ and _____ divisions.

• sympathetic - fight or flight

• parasympathetic - rest & digest

Receptors for general somatic/visceral senses are _____. Name some examples of general somatic and visceral senses.

Widespread

Somatic senses: touch, pain, vibration, pressure, temperature

Visceral senses: stretch, pain, temperature, nausea, hunger (widely felt in digestive & urinary tracts, and reproductive organs)

Receptors for special somatic/visceral senses are _____. Name some examples of special somatic and visceral senses.

Confined within a small space (mostly in the head)

Somatic examples: hearing, balance, vision

Visceral examples: taste & smell

The visceral motor system regulates contradiction of ______ muscle.

Smooth & cardiac

What are the two main cell types occupying nervous system and what do they do.

• Neurons —> transmit electrical signals

• Neuroglial cells —> provide nourishment & insulation for neurons

What is nerve impulse (or action potential)?

Nerve impulses are electrical signals that occur specifically along the axon of a neuron.

What are some special characteristics of neurons?

• Long-lived

• Do not undergo mitotic cell division & cannot regenerate

• High metabolic rate / constantly active

Neurons require a continuous supply of _____ and _____, and you will shortly die after being deprived of this.

Oxygen and glucose

Chromatophilic (nissl) bodies are only found within the _____ of a neuron and only extend into the basal part of dendrites.

Cell body

What are neurofibrils? What structures do they form a network for?

Neurofibrils are bundles of intermediate filaments that fill the cell body. They form a network between chromatophilic bodies for protein transport.

True or false, branching axons carry electrical signals out, but cell bodies are NOT repeated?

True

What are the two types of neuronal processes and their characteristics?

Dendrites

• short, highly branched

• relay electrical signals TOWARDS cell body

Axons

• long, singular

• relay electrical signals AWAY from cell body

• lack organelles but rich in neurofilaments, actin filaments, and microtubules

Name the following structures:

• multiple branches at the end of an axon

• knob-like structures at the end of these branches

• terminal branches

• axon terminals

What is released at axon terminals?

Neurotransmitters

What are synapses? Explain the two different types that can occur.

A synapse is the site at which neurons communicate.

• Axodendritic (most common) - between axon terminals of one neuron and dendrites of another

• Axosomatic - between axons & neuronal cell bodies

What is the difference between a presynaptic neuron and a postsynaptic neuron?

• Presynaptic neuron - conducts signal towards a synapse

• Postsynaptic neuron - conducts a signal away from a synapse

Describe the different structural classifications of neurons.

• Multipolar - possess three or more processes (numerous dendrites & ONE axon)

• Bipolar - possess only two processes (one dendrite, one axon)

• Unipolar - possess one short, single process (one axon w/ a peripheral & central process)

Most unipolar neurons and all bipolar neurons are _____ neurons.

Sensory

A small percentage of multipolar neurons are _____ neurons.

Motor

Most multipolar neurons are ______ neurons.

Interneurons (a.k.a. association neurons)

What are the four types of supporting cells found in the CNS and their characteristics?

Astrocytes

• most abundant type of neuroglia

• resemble star shape

• extract blood sugar from blood capillaries

• regulate ion levels around neurons

Microglia

• Oval / elongated body

• Called macrophages of the CNS bc they’re highly phagocytic

• Derived from monocytes (blood cells)

Ependymal cells

• Either simple columnar or simple cuboidal cells

• Line the walls of the central cavity of the brain & spinal cord

• Bears cilia to help propel CSF

Oligodendrocytes

• Have few branches

• Produce myelin sheaths within CNS

What are the two types of supporting cells found within the PNS and their characteristics?

Satellite cells

• Surround neuronal cell bodies within ganglia

• Exact function remains unknown

Schwann cells (neurolemmocytes)

• Forms myelin sheath within PNS

True or false, neuroglia cannot divide throughout life?

False

What are myelin sheaths and what do they do?

Myelin sheaths are segmented structures composed of the lipoprotein myelin. They form an insulating layer for thicker axons & prevent leakage of electrical currents.

True or false, Schwann cells fully wrap around bundles of axons?

False, they SURROUND axon bundles but don’t fully wrap around them.

Thick axons are myelinated or unmyelinated?

Thin axons are myelinated or unmyelinated?

Thick axons are myelinated.

Thin axons are unmyelinated.

True or false, nerves contain all 4 types of tissue?

True

True or false, myelin naturally appears white?

True

Describe the layers of connective tissue found wrapped within neurons.

• Endoneurim - delicate layer surrounding the axon

• Perineurim - surrounding a nerve fascicle

• Epineurim - tough sheath surrounding the whole nerve

True or false, interneurons transport information from one area of the CNS to one area of the PNS?

False, interneurons primarily transport information from one area of the CNS to another.

List the components making up a reflex arc.

1) Sensory receptor - help pick up stimulus

2) Sensory neuron - carry the sensory impulses toward the CNS organ

3) Integration center

4) Motor neuron - transmit motor impulses towards the effector

5) Effector - receives impulse & results in muscle contraction or gland secretion

What are the two types of reflexes and their characteristics?

Monosynaptic reflex

• Involves only one synapse & no interneuron

• Simplest & fastest reflex

Polysynpatic reflex

• Involves two or more synapses & one or more interneurons

• “Withdrawal” reflex bc it involves withdrawal from danger

What are neuronal circuits and what are the different types?

Neuronal circuits are the pathways that allow interneurons to connect to other neurons.

• Diverging circuit - one presynaptic neuron synapses with several other neurons, creating multiple outputs

• Converging circuit - many neurons synapse on a single postsynaptic neuron

• Reverberating circuit - circuit that receives feedback via a loop that is created when a neuron in the circuit sends a signal back to a previous neuron

What is serial processing and parallel processing?

• Serial processing - concerns a single file positioning of the neurons to a specific destination

• Parallel processing - input is delivered along many pathways, and thus, a single sensory stimulus will bring abt multiple perceptions of a situation

What is a three-neuron reflex arc?

It is the basis of the structural plan of the nervous system & involves a sensory neuron, interneuron, and motor neuron, hence the name “three-neuron”.