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Elena Baechli - Period 5 The nervous system - Coggle Diagram
Elena Baechli - Period 5
The nervous system
Major functions of the nervous system
The nervous system is divided into two principal parts
central nervous system (CNS)
peripheral nervous system (PNS)
master controlling and communicationg system of body
Nervous system has three overlapping functions
sensory input
information about external and internal changes
integration
processing and interpretation of sensory input
Motor output
activation of effector organs produces a response
Cranial nerves
I(1): Olfactory nerves
sensory nerves of smell
fibers synapse in olfactory bulbs
II(2): Optic nerves
purely sensory (visual) function
optic radiation fibers run to occipital (visual) cortex
III(3): Oculomotor nerves
function in raising eyelid, directing eyeball, contracting iris (Parasympathetic), and controlling lens shape
VI(6): Abducens nerves
primarily a motor innervating lateral rectus muscle
VII(7): Facial nerves
motor functions include facial expression, parasympathetic impulses to lacrimal and salivary glands
sensory function (taste) from the anterior two-thirds of the tongue
VIII(8): Vestibulocochlear nerves
formerly auditory nerves
afferent fibers from hearing receptors
enters brain stem at pons-medulla border
IX(9): Grossharayngeal nerves
motor function innervates part of the tongue and pharynx for swallowing
sensory function fibers conduct taste and general sensory impulses
X(10): Vagus nerves
only cranial nerve that extends beyond the head and neck region
motor fibers are parasympathetic fibers that help regulate activities of the heart, lungs, and abdominal viscera
XI(11): Accessory nerves
formerly spinal accessory nerve
XII(12): Hypoglossal nerves
innervate extrinsic and intrinsic muscles of the tongue that contribute to swallowing and speech
IV(4): Trochlear nerves
primarily motor nerve that directs eyeball
V(5): Trigeminal nerves
largest cranial nerve fibers extend from pons to face
three divisions
ophthalmic (V1) passes through the superior orbital fissure
maxillary (V2) passes through foramen rotundum
Mandibular (V3) passes through the foramen ovale
Spinal nerves
31 paired of spinal nerves
8 pair of cervical nerves (C1 - C8)
12 pairs of thoracic nerves (T1 - T12)
5 pairs of lumbar nerves (L1 - L5)
5 pairs of sacral nerves (S1 - S5)
1 pair of tiny coccygeal nerves (Co)
classification of nueron
neurons (nerve cells) are structural units of the nervous system
all have cell body and one or more processes
structural classification
three types grouped by the number of processes
Multipolar: three or more processes (1 axon, others dendrites)
Bipolar: two processes (one axon, one dendrite)
Unipolar: one T-like process (two axons)
Functional classification of neurons
three types of neurons grouped by direction in which nerve impulse travels relative to CNS
Sensory
transmit impulses from sensory receptors toward the CNS
Motor
carry impulses from CNS to effectors
Interneurons
lie between motor and sensory neurons
major parts and functions of the brain
Cerebral hemispheres
Surface markings
Gyri: ridges
Sulci: shallow grooves
Fissures: deep grooves
longitudinal fissure
Transverse cerebral fissure
Several sulci divide each hemisphere into five lobes
frontal - parietal - temporal - occipital - insula
Each hemisphere has three basic regions
cerebral cortex of gray matter superficially
white matter internally
basal nuclei deep within white matter
Diencephalon
Consists of three paired gray-matter structures
Thalamus - Hypothalamus - Epithalamus
all three enclose the third ventricle
Brain stem
consists of three regions: midbrain, pons medulla oblongata
controls automatic behaviors necessary for survival
Cerebellum
cerebral hemispheres connected by wormlike vermis
contains a thin cortex of gray matter with a distinctive tree-like pattern of white matter called arbor vitae
functions
provide precise coordinated movements of skeletal muscles
plays role in thinking, language, and emotion
balance and coordination
grey matter: short, nonmyelinated neurons and cell bodies
White matter: myelinated and nonmyelinated axons
Ventricles
lateral ventricles are large, C-shaped
pair is separated by membranous septum pellucidum
each lateral ventricle is connected to the third ventricle via the interventricular foramen
the third ventricle is connected to the fourth ventricle via a cerebral aqueduct
major parts and functions of the spinal cord
the spinal cord is enclosed in the vertebral column
begins at the Foramen Magnum
ends at L1 or L2 vertebra
Functions
provides two-way communication to and from the brain and body
Major reflex center: reflexes are initiated and completed at the spinal cord
Epidural space
cushion of fat and network of veins in space between vertebrae and spinal dura mater
spinal cord terminates in cone-shaped structure called conus medullaris
Film terminale extends to coccyx
denticulate ligaments
cervial and lumbar enlargements: areas where nerves servicing upper and lower limbs arise from spinal cord
spinal nerves
attach to spinal cord by 31 paired roots
cauda equina
collection of nerve roots at inferior end of vertebral canal
two lengthwise grooves that run length of cord partially divide it into right-and-left halves
ventral (anterior) median fissure
Dorsal (posterior) median sulcus
central canal runs length of cord
filled with cssf
Neurotransmitters
Language of nervous system
Most neurons make two or more neurotransmitters
classified by:
chemical structure
function
Classification of neurotransmitters by chemical structures
Acetylcholine (ACh)
released at neuromuscular junctions
degraded by enzyme acetylcholine (AchE)
Biogenic amines
Catecholamines
Indolamines
All widely used in the brain: play roles in emotional behaviors and biological clock
Imbalances are associated with mental illness
Amino acids
Peptides (neuropeptides)
Purines
Gases and lipids
Endocannabinoids
Functions can be grouped into two classifications
Effects: excitatory versus inhibitory
Effect determined by receptor to which it binds
Actions: direct versus indirect
Direct action: neurotransmitter binds directly to and opens ion channels
Indirect action: neurotransmitter acts through intracellular second messengers
Neural integration: neurons functioning together in groups
Reflex arc
Components of a reflex arc (Neural Path)
Receptor: site of stimulus action
Sensory neuron: transmits afferent impulses to CNS
Integraction center: either monosynaptic or polysynaptic region within CNS
Motor neuron: conducts efferent impulses from integration center to effector organ
Effector: muscle fiber or gland cell that responds to efferent impulses by
contracting or secreting
Reflexes are classified functionally as:
Somatic reflexes
activate skeletal muscle
Autonomic (visceral) reflexes
Activate visceral effectors (smooth or cardiac muscle or glands
Disorders / Diseases
Cerebrovascular Accident (stroke)
occurs when blood flow to a portion of the brain is halted
can be caused by diabetes and increasing age
Autism
a developmental disability caused by differences in the brain.
can be caused by family history and hereditary
mostly males are affected
Alzheimer's Disease
a form of dementia associated with age
can be caused by hereditary, family history
ages over 60
Spinal cord injury
damage to the spinal cord
direct injury or disease
most common in men age 15 - 35
assault, fall, accident
Meningitis
infection in the meninges surrounding the brain
caused by drug allergies, tumors, fungi or parasites
Multiple sclerosis
autoimmune disease that damages the myelin sheath
caused by hereditary, family history, and environmental factors
Drugs of abuse (Mouse Party)
Ecstasy
mimics serotonin
overstimulating the cell
affects mood, sleep, perception and appetite
Heroine
immediate feeling of sedation and well-being
used as painkiller
heroine mimics natural opiates
turning off dopamine inhibition
Marijuana
cannabinoid receptors turn off the release of the inhibitory neurotransmitter
slowing down the movement
feel relaxed and calm
Methamphetamine
keeps binding again to the receptor, overstimulating the cell
making users feel intense pressure and exhilaration
Cocaine
blocks the transporters leaving the dopamine trapped in the synaptic cleft
keeps binding to the receptors overstimulating the cell
abusers are fidgety and unable to stay still
LSD
excite the receptors
has complex sensory effects
the feeling of wakefulness
evoking a startling response
Alcohol
delivers a double sedative punch
binds glutamate receptors preventing glutamate from exiting the cell
affects area of the brain
involved in memory function
Decision-making and impulse control
connective tissue coverings
meninges
cover and protect CNS
contains cerebrospinlal fluis
Consists of three-layer (From external to internal): Dura mater, arachnoid mater, and pia mater
Dura mater
stongest meninx
Arachnoid mater
Middle layer with spiderweb-like extensions
Subarachnoid space contains CSF and largest blood vessels of brain
Separated from dura mater by subdural space
Pia mater
Delicate connective tissue that clings tightly to brain, following every convolution
Tissues (structure & function of neurons and neuroglia)
Nervous tissue consists of two principle cell types
– Neuroglia (glial cells): small cells that surround and wrap delicate neurons
Four main neuroglia suppoet CNS neurons
Astrocytes
Most abundant, versatile, and highly branched of glial cells
Functions include:
Control the chemical environment around neurons
Respond to nerve impulses and neurotransmitters
Participate in information processing in the brain
Microglial cells
Small, ovoid cells with thorny processes that touch and monitor neurons
Migrate toward injured neurons
Ependymal cells
Range in shape from squamous to columnar
Form a permeable barrier between cerebrospinal fluid (CSF) in cavities and tissue fluid bathing CNS cells
Oligodendrocytes
Processes wrap CNS nerve fibers, forming insulating myelin sheaths in thicker nerve fibers
branched cells
Two major neuroglia seen in PNS
Satellite cells
Surround neuron cell bodies in PNS
Schwann cells (neurolemmocytes)
Surround all peripheral nerve fibers and form myelin sheaths in thicker nerve
fibers
– Neurons (nerve cells): excitable cells that transmit electrical signals
Neurons (nerve cells) are structural units of nervous system
All have a cell body and one or more processes
Most neuron cell bodies are located in the CNS
Nuclei: clusters of neuron cell bodies in CNS
Ganglia: clusters of neuron cell bodies in PNS
Action potential & the Nerve Impulse
Action potentials (APs) do not decay over distance as graded potentials do
In neurons, aka nerve impulse
Involves opening of specific voltage-gated channels
Generating an Action Potential
Four main steps
Resting-state: All gated Na+ and K+ channels are closed
Depolarization: Na+ channels open
Repolarization: Na+ channels are inactivating, and K+ channels open
Repolarization: membrane returns to resting membrane potential
Hyperpolarization: Some K+ channels remain open, and Na+ channels reset
Compare & contrast the autonomic nervous system
Automatic nervous system (ANS) consists of motor neurons that:
Innervate smooth muscles, cardiac muscle, and glands
Make adjustments to ensure optimal support for body activities
Shunts blood to areas that need it and adjusts heart rate, blood
pressure, digestive processes, etc
Also called involuntary nervous system or general visceral motor
system
Two arms of ANS:
Parasympathetic division: promotes maintenance functions,
conserves energy
Sympathetic division: mobilizes body during activity
Dual innervation: all visceral organs are served by both divisions, but
these divisions cause opposite effects
Role of the Parasympathetic Division
Keeps body energy use as low as possible, even while carrying out
maintenance activities
Referred to as a “rest-and-digest” system
Example: person relaxing and reading after a meal
Also called craniosacral division because fibers originate from the brain
stem and sacral regions or cord
Long preganglionic fibers extend from CNS almost to target organs
Role of the Sympathetic Division
Mobilizes body during activity
Referred to as “fight-or-flight” system
Exercise, excitement, emergency, embarrassment activates
sympathetic syste
Sympathetic is more complex and innervates more organs than
parasympathetic
-Sympathetic also called thoracolumbar division
Major divisions and subdivisions of the nervous system
The nervous system is divided into two principal parts:
Central nervous system (CNS)
Peripheral nervous system (PNS)
Peripheral nervous system (PNS)
The portion of the nervous system outside the CNS
Consists mainly of nerves that extend from the brain and spinal cord
Spinal nerves to and from the spinal cord
Cranial nerves to and from the brain
Central nervous system (CNS)
Brain and spinal cord of dorsal body cavity
Integration and control center: Interprets sensory input and dictates motor output
ventricles
cerebral hemisphere
primary (somatic) motor cortex
Premotor cortex
broca's area
motor speech area that directs muscles of speech production
frontal eye field
Brain stem
medulla oblongata
pons
midbrain
cerebral aqueduct: channel running though the midbrain that connects third and fourth ventricle
Peripheral nervous system (PNS) has two functional divisions:
Sensory (afferent) division
Somatic sensory fibers: convey impulses from skin, skeletal muscles, and joints to CNS
Visceral sensory fibers: convey impulses from visceral organs to CNS
Motor (efferent) division
Transmits impulses from CNS to effector organs (Muscles and glands)
Two divisions:
Somatic nervous system (voluntary)
Conscious control of skeletal muscles
Autonomic nervous system (involuntary)
Regulates smooth muscle, cardiac muscle, and glands
Two functional subdivisions
Sympathetic
Parasympathetic