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Nervous System: Gabriela Orellana P.5 - Coggle Diagram
Nervous System:
Gabriela Orellana
P.5
Major functions of the nervous system:
Sensory function:
-Detect internal or external changes
-Information travels from receptors to sensory neurons, which transport information into the CNS.
Integrative Function:
-Coordination of sensory information in the CNS
-The process of this information is the basis for decision-making.
Motor Function:
-Nerve impulses (CNS) are conducted along motor neurons to effectors
Major divisions and subdivisions of the nervous system (subdivisions of CNS and PNS):
Central Nervous System (CNS):
A.
Brain
B.
Spinal cord
Pheripheral Nervous System (PNS):
A:
Cranial nerves arising from the brain and brainstem
1.
Sensory fibers connecting peripheral sensory receptors to the CNS
2.
Somatic fibers connecting to skin and skeletal muscles
3.
Automatic fibers connecting to viscera
B.
Spinal nerves arising from the spinal cord
1.
Sensory fibers connecting peripheral sensory receptors to the CNS
2.
Somatic fibers connecting to skin and skeletal muscles
3.
Autonomic fibers connecting to viscera
Tissues (structure & function of neurons and neuroglia):
Neurons:
Dendrites:
Receive signals from other cells
Cell body:
Organizes and keeps the cell functional
Cell membrane:
Protects the cell
Axon Hillock:
Generates impulse in the neuron
Node of Ranvier:
Allow diffusion of ions
Schwann cell:
Produces the myelin sheath
Axon terminal:
Forms junctions with other cells
Myelin Sheath:
Increases the speed of the signal
Axon:
Transfers signals to other cells and organs
Nucleus:
Controls the entire neuron
Neuroglia:
Astrocytes:
Origin:
Neural tube
Location:
CNS
Function:
-Structural support, repair processes
-Blood-brain barrier, metabolic exchanges
Oligondendrocytes:
Origin:
Neural tube
Location:
CNS
Function:
Myelin production, electric insulation
Schwann cells:
Origin:
Neural tube
Locations:
PNS
Function:
Myelin production, electric insulation
Ependymial Cells:
Origin:
Nueral tube
Location:
CNS
Function:
Lining cavities of central nervous system
Microglia:
Origin:
Bone marrow
Location:
CNS
Functions:
Macrophagic activity
Classification of neurons:
Structural Classification:
Multipolar neurons:
-Many dendrites
-One axon arising from their cells bodies
-Most neurons with cell bodies in CNS are multipolar
Bipolar Neurons:
-Have 2 processes extending from the cell body
-1 dendrite and 1 axons
-Found in special sense, i.e eyes, nose, ears.
Unipolar Neurons:
-1 process extending from the cell body
-Outside the cell body, it splits into 2 parts that function as 1 axon
-The peripheral proces has dendrites near a peripheral body part
-The central process runs into the CNS
-The cell bodies are found in ganglia outside the CNS (sensory neurons)
Functional Classification:
Sensory (afferent) neurons:
-Conduct impulses from peripheral receptors to the CNS, usually unipolar, although some are bipolar
Interneurons (association or internuncial neurons):
-Multipolar neurons lying within the CNS that form links between other neurons
-The cell bodies of some interneurons aggregate in speacialized masses called
nuclei
Motor (efferent) nuerons:
-Multipolar neurons that conduct impulses from the CNS to peripheral effectors (muscle or glands)
Sensory receptor
Sensory neuron
Interneuron
interneuron
Motor neuron
Effector (muscle or gland)
Connective Tissue Coverings:
Epineurium:
covering around fascicles (bundles) of nerve fibers
Perineurium:
covering around individual nerve fibers (axons)
Endoneurium:
outer covering of a nerve
Major parts and functions of the spinal cord:
Functions of the spinal cord:
-Major functions:
transmit impulses to and from the brain, and to house spinal reflexes.
-Ascending tracts:
carry sensory information to the brain;
descending tracts
carry motor information from brain to muscles or glands.
-Spinal reflexes:
controlled by reflex arcs that pass through the spinal cord
Major parts:
Spinal cord:
Begins at the base of the brain
Cervical enlargement:
-A thickened area near top of spinal cord
-Provides nerves to upper limbs
Lumbar enlargement:
-A thickened region near the bottom of the spinal cord
-Gives rise to nerves that serve the lower limbs
Cauda Equina (horse´s tail):
-Structure formed where spinal cord tapers to a point inferiorly
-Consists of spinal nerves in the lumbar & sacral areas
Action potential & the Nerve Impulse:
Action potential:
-All-or-none response
-Action potential either occurs or does not
-Action potentials of a neuron are all of the same strength
Nerve Impulse:
Polarized: Resting neuron
-
Inside
membrane is slightly -
-
Outside
membrane is slightly+
-Most membrane channels are closed
Depolarization: Active Neuron:
-Sodium (Na+) channels open allowing Na+ to diffuse into the cell quickly
-This causes the
inside
to become
+ (outside-)
Repolarize: Normalizing
-K+ gates open in order to allow K+ to diffuse out of the cell - this restores the membrane
(+ outside, - inside)
Cranial Nerves:
Twelve pairs of cranial nerves
arise from the underside of the brain.
-Most mixed nerves, containing sensory & motor nerve fibers, but some are only
sensory
, and others are
primarily motor
I Olfactory:
-
Type:
Sensory
-
Function:
Sensory fibers conduct impulses associated with the sense of smell
II Optic:
-
Type:
Sensory
-
Function:
Sensory fibers conduct impulses associated with the sense of vision
III Oculomotor:
-
Type:
Primarily motor
-
Function:
Motor fibers conduct impulses to muscles that raise eyelids, move eyes, adjust
the amount of light entering the eyes, and focus lenses
IV Trochlear:
-
Type:
Primarily motor
-
Function:
Motor fibers conduct impulses to muscles that move the eyes.
V Trigeminal:
Type:
Mixed
Ophthalmic Division:
-Function:
Sensory fibers conduct impulses from the surface of the eyes, tear glands, scalp, forehead, and upper eyelids
Maxillary division:
-Function:
Sensory fibers conduct impulses from the upper teeth, upper gum, upper lip, lining of palate, and skin of the face.
Mandibular division:
-Function:
-Sensory fibers conduct impulses from the skin of the jaw, lower teeth, lower gum, and lower lip
-Motor fibers conduct impulses to muscles of mastication and to muscles in the floor of the mouth.
VI Abducens:
-Type:
Primarily motor
-Function:
-Motor fibers conduct impulses to muscles that move the eyes.
-Some sensory fibers conduct impulses associated with the condition of muscles
VII Facial:
-
Type:
Mixed
-
Function:
Sensory fibers conduct impulses associated with taste receptors of the anterior tongue. Motor fibers conduct impulses to muscles of facial expressions, tear glands, and salivary glands.
VIII Vestibulocochlear:
-
Type:
Sensory
-
Vestibular Branch:
-
Function:
Sensory fibers conduct impulses associated with the sense of equilibrium.
Cochlear Branch:
-
Function:
Sensory fibers conduct impulses associated with the sense of hearing
XI Glossopharyngeal:
-
Type:
Mixed
-
Functions:
-Sensory fibers conduct impulses from the pharynx, tonsils, posterior tongue, and carotid arteries
-Motor fibers conduct impulses to muscles of the pharynx used in swallowing and to salivary glands
X Vagus:
-
Type:
Mixed
-
Functions:
-Somatic motor fibers conduct impulses to muscles associated with speech and swallowing; autonomic motor fibers conduct impulses to the heart, smooth muscle, and glands in the thorax and abdomen.
-Sensory fibers conduct impulses from the pharynx, larynx, esophagus, and viscera of the thorax and abdomen.
XI Accessory:
-
Type:
Primarily Motor
Cranial Branch:
-
Function:
Motor fibers conduct impulses to muscles of the soft palate, pharynx and larynx.
Spinal Branch:
-Functions:
Motor fibers conduct impulses to muscles of the neck and back
XII Hypoglossal:
-Type:
Primarily motor
Function:
Motor fibers conduct impulses to muscles that move the tongue
Spinal Nerves:
31 pairs
arise from spinal cord
-All except the first pair are
mixed nerves
-Grouped according to the level from which they arise
-Each arises from two roots:
:check:
a sensory dorsal root
:check:
a motor ventral root
-Numbered in sequence:
:check:
8 pairs of cervical nerves
:check:
12 pairs of thoracic nerves
:check:
5 pairs of lumbar nerves
:check:
1 paid of coccygeal nerves
Neurotransmitters:
Acetylcholine:
Location:
CNS
Major Functions:
Controls skeletal muscle actions.
Location:
PNS
Major Functions:
Stimulates skeletal muscle contraction at neuromuscular junctions; may excite or inhibit autonomic nervous system actions, depending on receptors.
Dopamine:
Location:
CNS
Function:
Creates a sense of feeling good; deficiency in some brain areas is associated with Parkinson disease.
Location:
PNS
Major Functions:
Limited actions in autonomic nervous system; may excite or inhibit, depending on receptors
Monoamines:
Norepinephrine:
Location:
CNS
Function:
Creates a sense of feeling good; low levels may lead to depression.
Location:
PNS
Function:
May excite or inhibit autonomic nervous system actions, depending on receptors.
Serotonin:
Location:
CNS
Functions:
Primarily inhibitory; leads to sleepiness; action is blocked by LSD, enhanced by selective serotonin reuptake inhibitor drugs (SSRIs).
Histamine:
Location:
CNS
Major Functions:
Release in hypothalamus promotes alertness.
Compare & contrast the autonomic Nervous system
:
Sympathetic Division:
Active in conditions of stress or emergency
Ex)
Flight or Flight
Characteristics:
Short
preganglionic fibers
arise from neurons in the gray matter in the thoracic and lumbar regions of the spinal cord
Parasympathetic Division:
Active under normal, restful conditions.
Ex)
Rest and Digest
Characteristics:
Long
preganglionic fibers
arise from the brainstem and sacral region of the spinal cord
Reflex arc (major parts & functions):
Provides the basis for involuntary actions
:diamond_shape_with_a_dot_inside:Receptors:
Description:
Receptors end of a dendrite or a specialized receptor cell in a sensory organ
Function:
Senses specific type of internal or external change
:diamond_shape_with_a_dot_inside:Sensory neuron:
Description:
Dendrite,cell body, and axon of a sensory neuron
Function:
Carries information from receptor into brain or spinal cord
:diamond_shape_with_a_dot_inside: Interneuron
Description:
Dendrite, cell body, and axon of a neuron within the brain or spinal cord
Function:
Carries information from sensory neuron to motor neuron
Major parts and Functions of the brain:
Main parts:
Cerebrum:
-Largest portion
-associated with higher mental functions and sensory & motor functions
Diencephalon:
-Processes sensory input
-Controls many homeostatic processes
Cerebellum:
coordinates muscular activity
Brainstem:
-coordinates and regulates visceral activities
-connects different parts of the nervous system
Functions:
Cerebellum:
-Integrates sensory information about the position of body parts
-Coordinates skeletal muscle activity
-Maintains posture
-Ensures that movement occurs in the desired manner
Brainstem:
-Sends signal from your brain to the rest of your body.
-Controls many subconscious body functions e.i breathing and maintaining heart rate.
Diencephalon:
-Primary relay and processing center for sensory information and autonomic control
Cerebrum:
-Provides higher brain function, e.i Interpretation of sensory input, initiating voluntary muscular movements, stores information for memory, Integrates information for reasoning, intelligence, and personality .