The Nervous System
Juliana Soto
P.6

Divisions Of The Nervous System

Central NS
consist of brain and spinal cord
where memories are formed & stored

Peripheral NS
consist of cranial and spinal nerves

Somatic NS
brings information from skin, special senses, body wall & limbs to CNS & motor neurons to skeletal muscles
voluntary portion of PNS

Automatic NS
brings information from receptors in internal organs to CNS & motor neurons to smooth and cardiac muscles and glands. Voluntary responses.

Sympathetic Nervous System
“Fight or Flight”
kicks in when you are in emergency or non-normal situations (angry, nervous, scared)

Parasympathetic Nervous System
”Feed and Breed”
Normal, everyday situations (calms you, happy)

Major Functions of the Nervous System

Tissues (structure & function of neuron and neuroglia)

Major parts and functions of the spinal cord

Action potential
A strong enough stimulation or nerve impulse causes Na+( sodium) gates to open

Cranial nerves and Spinal nerves

Neurotransmitters
chemical messenger that carries, boosts, and balances signals between neurons (also known as nerve cells) and target cells throughout the body.

Anatomy of the spinal cord

Compare & contrast the autonomic nervous system

Reflex arc (major parts & functions)
direct root from sensory neuron to an interneuron, motor neuron to an effector

Sensory Function
detects changes (stimuli) within & outside body

Motor Functions
May respond to stimuli by initiating muscular contractions or glandular secretions

Integrative Function
Analyzes sensory information, stores some aspects, & makes decisions regarding appropriate behaviors (thinking portion)

Sensory/ Afferent Neurons
carry information from body to CNS

Motor/ Efferent Neurons
Carry instructions away from CNS to target

Nerve Tissues
Made of neuron (nerve cell) & neuralgia

Neuron
Made up of
•Cell Body- contains nucleus & other organelles
•Dendrites- receiving portions, short, tapered & highly branched
•Axons- start as a single fiber, but may give off branches called collateral axon

Neuralgia
Act in support, guiding development & stimulation & maintenance

Types of Neuroglia in CNS
Astrocytes- star shaped cells with many processes
Oligodendrocyte- most common, from the myelin sheath for neurons
Microglia- small, have fewer processes, & are phagocytes. They protect the CNS by phagocytizing microbes and clearing away debris from inflammation & tissue damage

Types of Neuralgia in PNS
Schwann Cells- supply myelin sheathes to axons in the PNS & aids the regrowth of damaged peripheral axons
Satellite Cells- flattened cells found around cell bodies

Classifications of Neurons & Coverings

Unipolar
just one process & are always sensory neurons, axon terminals are in CNS & cell bodies in ganglia

Multipolar
several dendrites & one axon
(most neurons in CNS are this type)

Bipolar
one main dendrite & one main axon, usually in special sense organs

Functional Classification

Sensory or Afferent Neurons
transmit sensory impulses (toward CNS) & have specialized receptor ends at tips of dendrites or the dendrites are in contact with specialized receptor cells in skin or sense organs. Most are unpolar some are bipolar

Motor or Efferent Neurons
transmit motor nerve impulses from CNS to effectors

Interneurons
multipolar neurons in CNS that form links between other neurons. Found between the sensory and motor neuron. Relays information to multiple areas.

Coverings
Mylelin
Most axons are surrounded by a myelin sheath. Acts as an insulator. Increases speed, which impulse travels. Gaps between myelin sheath (nodes of ranvier)

Two Enlargements
Lumbar Enlargement- T9-T12- nerves to & from lower limbs
Cervical Enlargement
C4-T1- Nerves to & from upper limbs

Two Functions of the Spinal Cord
White Matter Tracts- serve as information highways to and from brain
Gray Matter- receives & integrates information especially for spinal reflexes

Then the Na+ rush into the cell causing depolarization, membrane potential) goes towards or unpolarized & momentarily becomes positively charged

If strong enough, depolarization occurs, threshold potential is reached (+30) & impulse is sent down axon

Spinal Nerves
-Posterior/ dorsal roots contain sensory fibers whose cell bodies are located in dorsal root ganglion

Cranial Nerves

Anterior/ Ventral rods contain motor axons & conduct impulses from brain & cord to periphery

Attached to spinal cord by dorsal & ventral roots

Allows body & brain to communicate

Epinephrine & Norepinephrine

Effector Organs
Eyes, heart, lungs etc.

Remember
“E” exercise, excitement, emergency, & embarrassment.

Acetylcholine

Effector Organs
Salivary glands, digestive & responsive organs

Remeber “O”
digestion, defection, & diuresis (urination)

I Olfactory Nerve
Function: Smell

II Optic Nerve
Function: Vision

III Oculomotor Nerve
Function: Eye movement; pupil constriction

IV Trochlear Nerve
Function: Eye movement

V Trigeminal Nerve
Function: Somatosensory information (touch, pain) from the face and head; muscles for chewing.

VI Abducens Nerve
Function: Eye movement

VII Facial Nerve
Function: Taste (anterior 2/3 of tongue); somatosensory information from ear; controls muscles used in facial expression.

VIII Vestibulocochlear Nerve
Function: Hearing; balance

IX Glossopharyngeal Nerve
Function: Taste (posterior 1/3 of tongue); Somatosensory information from tongue, tonsil, pharynx; controls some muscles used in swallowing.

X Vagus Nerve
Function: Sensory, motor and autonomic functions of viscera (glands, digestion, heart rate)

XI Spinal Accessory Nerve
Function: Controls muscles used in head movement.

XII Hypoglossal Nerve
Function: Controls muscles of tongue

C367B1C3-1CF2-4B22-A736-E25098D667F1

Two Spinal Nerves
-Dorsal Root (back)
-Ventral Root (front)
Two nerve roots join to become the 31 pairs of spinal nerves

Two Grooves Divide Spinal Cord
-Anterior Median Fissure (deeper)
-Posterior Median Sulcus

Receptor
Responds to signals

Sensory Neurons
sends information from the body to the central nervous system, the brain and spinal cord

Interneurons
connect sensory input to other cells that are required for action

Motor Neurons
send messages from the central nervous system to the body & muscles

Muscles
cause us to take action

The SNS has sensory and motor pathways, whereas the ANS has only motor pathways

The ANS controls internal organs and glands, while the SNS controls muscles and movement.

They both respond to external stimuli.

They both are controlled by the CNS