CHAP. 8 Nervous System

The master control and communication system of the body

Nervous system

2 major divisions of nervous system

Central & peripheral nervous system

What does the CNS comprise of?

brain and spinal cord

What does the PNS consist of?

all nerves and ganglia outside the brain and spinal cord

Receives and processes sensory information, initiates responses, stores memories, generates thoughts and emotions.

Brain

Conducts signals to and from the brain, controls reflex activities

Spinal cord

What are the functions of the nervous system?

1. Receiving sensory input

2. Integrating information

3. Controlling muscles and glands

4. Maintaining homeostasis

5. Establishing and maintaining mental activity

Communicate with body cells using electrical impulses, causing almost immediate responses.

CNS

Thick bundles of axons (nerves) carrying messages back and forth between the CNS and the rest of the body

PNS

2 functional classification of the PNS

Sensory division & Motor division

Conducts action potentials from sensory receptors to the CNS

Sensory division (afferent)

Conducts action potentials to effector organs, such as muscles and glands.

Motor division (efferent)

Main divisions of nervous system

1. Somatic nervous system

2. Autonomic nervous system

3. Enteric nervous system

Transmits action potentials from the CNS to skeletal muscles. All the nerves throughout the body that carry information from the senses

Somatic nervous system

Transmits action potentials from the CNS to most of the internal organs.

Autonomic nervous system

A special nervous system found only in the digestive tract

Enteric nervous system

What is the involuntary branch of the nervous system?

Autonomic nervous system

Autonomic nervous system consist of only what nerve

Motor nerves

Two divisions of autonomic nervous system

• Sympathetic division

• Parasympathetic division

“fight-or-flight”; Response to unusual stimulus

Sympathetic

What are the “E” division that we need to remember in sympathetic?

Exercise, excitement, emergency, and embarassment

Maintains daily necessary body functions; “rest-and'-digest” body processes.

Parasympathetic

What are the “D” that are remembered in parasympathetic?

Digestion, defecation, diuresis.

What is defecation?

Regulates the storage and elimination of stool.

A complex network of nerve cells within the walls of the gastrointestinal (GI) tract.

enteric nervous system

The enteric nervous system is composed of millions of neurons arranged in plexuses, which regulate key digestive functions:

• swallowing

• enzyme release

• nutrient absorption

• blood flow

• waste elimination

Specialized cells that can receive and transmit chemical or electrical signals

Neurons

What are the cells of the nervous system?

Neurons and glial cells

Receive stimuli, conduct action potentials, and transmit signals to other neurons or effector organs

Neurons

What is the function of the neurons?

They receive stimuli, conduct action potentials, and transmit signals to other neurons or effector organs

What cell is this?

Glial cell

cells that provide support functions for the neurons

Glial cell

What are the functions of glial cells?

They enhance neuron function and maintain normal conditions within nervous tissue.

What are the neuron structures?

• Dendrites

• Cell body

• Axon

The main part of the cell; contains a single nucleus and the organelles found in other types of cells

Cell body

Another term for cell body

Soma

Tree-like structures that extend away from the cell body to receive messages from other neurons at specialized junctions (synapses)

Dendrites

What do you all the specialized junctions where dendrites interface and receive signals from other neurons.

Synapses

A tube-like structure that propagates the integrated signal to specialized endings (axon terminals)

Axon

What do you call the specialized endings found at the end of an axon.

Axon terminals

What are the functional classification of neurons?

• Sensory neurons

• Motor neurons

• Interneurons

Carry signals from the outer parts of your body (periphery) into the CNS

Sensory neurons

Carry signals from the central nervous system to the outer parts (muscles, skin, glands) of your body

Motor neurons

Connect various neurons within the brain and spinal cord

Interneurons

What are the structural classification of neurons?

• Pseudounipolar neurons

• Bipolar neurons

• Multipolar neurons

Describe pseudounipolar neurons

only one nerve process extending from the cell body: an axon that extends into dendrites

Describe bipolar neurons

one axon and one dendrite

Describe multipoalr neurons

many dendrites and a single axon from the cell body

Bipolar neuron

Multipolar neuron

Pseudounipolar neuron

The supportive cells of the CNS and PNS; most retain the ability to divide.

Glial cells

Name the glial cells

• Astrocytes

• Microglia

• Ependymal cells

• Oligodendrocytes

• Satellite cells

• Schwann cells

Abundant, star-shaped cells that serve as the major supporting cells in the CNS.

Astrocytes

Name the glial cell

Astrocytes

Spider-like phagocytes; Dispose of debris

Microglia

Name the glial cell

Microglia

Line cavities of the brain and spinal cord ; Circulate cerebrospinal fluid

Ependymal cells

Name the glial cell

Ependymal cells

Produce myelin sheath around nerve fibers in the central nervous system.

Oligodendrocytes

Name the glial cell

Oligodendrocytes

This glial cell protect neuron cell bodies

Satellite cells

This glial cell form myelin sheath in the peripheral nervous system

Schwann cells

Name the glial cell

Schwann cells

Specialized layers that wrap around the axons of some neurons (myelinated).

Myelin sheath

What forms the myelin sheath in the CNS?

Oligodendrocyte

What forms the myelin sheath in the PNS?

Schwann cells

An excellent insulator that prevents almost all ion movement across the cell membrane.

Myelin sheath

This lacks the myelin sheaths

Unmyelinated neurons

A typical small nerve, consisting of multiple neuron axons, usually contains more unmyelinated axons than myelinated axons

Unmyelinated neurons

What do you call the gaps in the myelin sheath that occur about every millimeter?

Nodes of Ranvier

True or False:

Ion movement can occur at the nodes of Ranvier.

True

A disease of the myelin sheath that causes loss of muscle function.

Multiple sclerosis

What is multiple sclerosis?

A disease of the myelin sheath that causes loss of muscle function.

A chronic autoimmune disease of the central nervous system where the immune system mistakenly attacks the protective myelin sheath covering nerve fibers.

Multiple sclerosis

What are the two primary types of tissues that make up the CNS?

Gray & White matter

Neuron cell bodies and their dendrites, very little myelin

Gray matter

Parallel axons with their whitish myelin sheaths

White matter

Where does the spinal nerves come out?

Spine

Where does the cranial nerves come out?

Brain

How many pairs of cranial nerves are there?

12 pairs

How are cranial nerves numbered?

Roman numerals

These nerves are linked directly to the brain, without having to pass through the spinal cord.

Cranial nerves

2 categories of cranial nerves

Sensory and motor

What are the 12 pairs of cranial nerves?

• CN I – Olfactory Nerve

• CN II – Optic Nerve

• CN III – Oculomotor Nerve

• CN IV – Trochlear Nerve

• CN V – Trigeminal Nerve

• CN VI – Abducens Nerve

• CN VII – Facial Nerve

• CN VIII – Vestibulocochlear Nerve

• CN IX – Glossopharyngeal Nerve

• CN X – Vagus Nerve

• CN XI – Accessory Nerve

• CN XII – Hypoglossal Nerve

What is the 1st cranial nerve?

Olfactory nerve

Sensory nerve for smell.

Olfactory nerve

Outside of the CNS, olfactory nerves are called

Olfactory nerve

inside of the CNS, olfactory nerves are called

Olfactory tract

A patient says "Ah," and their uvula deviates to the right side. They also have a weakened gag reflex. Which cranial nerve is damaged?

Cranial Nerve X (Vagus Nerve)

• The functional right side pulls the uvula toward itself, away from the weak left side.

Transmits information from the eye’s retina; Vision

Optic nerve

Controls muscles that move the eyeball.

Oculomotor nerve

What is cranial nerve II?

Optic nerve

What is cranial nerve III?

Oculomotor nerve

What is cranial nerve IV?

Trochlear nerve

What is cranial nerve V?

Trigeminal nerve

What is cranial nerve VI?

Abducens nerve

What is cranial nerve VII?

Facial nerve

What is cranial nerve VIII?

Vestibulocochlear nerve

What is CN IX?

Glossopharyngeal nerve