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
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