Chapter 9 Nervous System

Basic Functions of the Nervous System

Sense Changes (Sensory)
Interpret these changes (Integrative)
React to change (Motor)

Number of Neurons in the Brain

100 Billion

Neurons Involved in Sensory Activities

Afferent

Neurons Involved in Motor Activities

Efferent

Cranial Nerves

I. Olfactory VII. Facial
II. Optic VIII. Vestibulocochlear
III. Oculomotor IX. Glossopharyngeal
IV. Trochlear X. Vagus
V. Trigeminal XI. Accessory
VI. Abducens XII. Hypoglossal

Nerve

a bundle of hundreds to thousands of axons plus connective tissue and blood that lie outside the brain and spinal cord

Ganglia

small masses of nervous tissue that is located outside of the brain and spinal cord

Central Nervous System
CNS

Includes the Brain and Spinal Cord
Integrates and controls all incoming information
Thoughts, emotions and memories
Stimulate muscles to contract and glands to secrete

Peripheral Nervous System
PNS

All the nervous tissue outside the CNS
Sonamic, Autonomic and Enteric

Somatic Nervous System

-Controls the motor neurons to move skeletal muscle.
-Voluntary control

Autonomic Nervous System

-Controls things that are involuntary like smooth and cardiac muscle
-Sympathetic-speed up heart rate, fight or flight
-Parasympathetic-slow down hear rate, rest and digest

Enteric Nervous System

-Involuntary
-Known as the brain of the gut, controls all the smooth muscles and glands of the GI tract

Neurons

process information and send out nerve impulses (action potentials)

Dendrites

receiving or input parts of the neuron

Axons

conducts nerve impulses toward another neuron or muscle fiber or to a gland

Neuroglia

“nerve glue”, Helps to nourish and protect the neurons and maintain homeostasis. No nerve conduction.

Myelin Sheath

-many layered covering made of lipids and proteins
-Increases speed of nerve conduction
-About 100 layers around each axon.
-Nodes of Ranvier-Gaps in the myelin, appear at intervals along the axon

White Matter

-Nervous tissue primarily made of myelinated axons of many neurons
-Blood vessels are present

Gray Matter

-Nervous Tissue contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals and neuroglia.
-Blood vessels are present

Tracts

Much of the CNS white matter has these, they are bundles of axons in the CNS that extend for some distance up and down the spinal cord or connective parts of the brain with each other or with the spinal cord

Neuroglia Cells

--CNS
-----Oligodendrocytes- produce and maintain myelin sheath
-----Astrocytes- Support and protect neurons
--PNS
-----Schwann Cells-Produce and maintain the myelin sheath

Maintaining Homeostasis

The nerve impulse or action potential is the body’s quickest way of controlling and maintaining homeostasis

Electrical Exciteability

The ability of a neuron (or muscle fiber) to respond to a stimulus and convert it into a nerve impulse

Repolarization

Restoration of the resting membrane potential

Refractory Period

The brief period of time during which the membrane recovers and cannot initiate another action potential

Refractory Period

The brief period of time during which the membrane recovers and cannot initiate another action potential

All-or-Nothing Potential

if a stimulus is strong enough to cause depolarization to threshold, the impulse will travel the entire length of the neuron at a constant and maximum strength

Saltatory Conduction

When nerve impulses leap from Node of Ranvier to Node of Ranvier, found principally in myelinated fibers

Continuous Conduction

impulse conduction in unmyelinated axons (and in muscle fibers) is much slower than salutatory conduction

Excitatory Transmitter

Receptor interaction is one that can depolarize or lower the postsynaptic neuron’s membrane potential, so that new impulses can be generated across the synapse

Inhibatory Transmitter

Receptor interaction is one that can increase the postsynaptic neuron’s membrane potential (hyperpolarization), so that new impulses are impeded from being generated across the synapse

Neurotransmitter is removed from the synaptic cleft by 3 methods

 Diffusion
 Enzymatic degradation
 Re-uptake