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Nervous System Jessika Lee P.1 - Coggle Diagram
Nervous System Jessika Lee P.1
Major Functions of nervous system
the nervous system is the controlling and communicating system of body
cells communicate via electrical and chemical signals
has 3 overlapping functions:
Sensory input
, info gathered by sensory receptors about internal and external charges
Integration
, processing and interpretation of sensory input
3.
Motor output
, activation organs produces a response
nervous system is divided into two principal parts
central nervous system
- integration and control center, interpreting sensory input and dictates motor output
Peripheral nervous system- consists mainly of nerves that extend from brain and spinal cord: spinal nerves and cranial nerves
Tissues
neuron tissue consists of 2 principal cell types:
neuroglia (glial cells), small cells that surround and wrap delicate neurons
-neurons(nerve cells), excitable cells that transmit electrical signals
Neurologlia of the CNS
4 main neurological support CNS neurons
Astrocytes
: most abundant, versatile, and highly branched of glial cells
Microglial cells
: small cells within processes that touch and monitor neurons
migrate towards injure neurons
can transform to phagocyte microorganisms and neuro debris
oligodendrocytes
: branched cells
process warp CNS nerve fibers, forming insulating myelin sheath in thicker nerve fibers
2 major neuroglia seen in PNS
Satellite cells, surround neuron cell bodies in the PNS
-function similar to astrocytes of CNS
Schwann cells, surround all peripheral nerve fibers and form myelin sheath in thicker nerve fibers
vital to regeneration of damaged peripheral nerve fibers
neurons are structural units of nervous system
large highly specialized cells that conduct impulses
extreme longevity
high metabolic rate
Divisions and subdivisions of the nervous system
Central Nervous System
integration and control center
Interprets sensory input and dictates motor output
brain and spinal cord
located dorsal body cavity
Peripheral Nervous System
the portion of the nervous system outside CNS
consists mainly of nerves that extend from brain and spinal cord
nerves and ganglia
cranial and spinal nerves extend from the CNS to peripheral organs such as muscles and glands
divided into afferent and efferent division
Autonomic Nervous System
consists of motor neurons that:
make adjustments to ensure optimal support fro body activities
shunts blood to areas that need it
operate via subconscious control
Somatic Nervous System
motor fibers
innervates skeletal muscles
cell body in CNS single thick myelinated group A axon extends in spinal or cranial nerves directly to skeletal muscle
all somatic motor neurons release ACh
effect is always stimulatory
Classification of neurons
Structural Classification
-3 types grouped by # of processes
Multipolar
- 3 or more processes, most common and major neuron type in CNS
Bipolar
- 2 processes, rare
Unipolar
- one process, also called pseudounipolar
Functional Classification
-3 types of neurons grouped by direction in which impulse travels relative to CNS
Sensory
- transmit impulses, almost all unipolar, cell bodies located in ganglia in PNS
motor
- carry impulses , multipolar, most located in CNS
Interneurons
- also called association neurons, lie between motor and sensory, shuttle signals through CNS pathway, entirely within CNS
Connective tissue coverings
three layers of meninges
outer layer is dura mater, tough white fibrous connective tissue
middle layer is arachnoid, thin layer
under arachnoid is subarachnoid space, contains blood vessels
innermost layer is pia mater, thin and delicate tightly bound to surface of the brain and spinal cord
connective tissue covering
nerve, cordlike organ of PNS
bundle of myelinated and unmyelinated peripheral axons enclosed by connective tissue
connective tissue coverings include:
Endoneurium
: loose connective tissue that encloses axons and their myelin sheaths
Perineurium
: connective tissue that bundles fibers into fascicles
Epineurium
: tough fibrous sheath around all fascicles to form the nerve
most nerves are mixtures of afferent and
Major parts and function of brain
adult brains have 4 regions
Cerebral hemisphere
Diencephalon
Brain stem
cerebellum
Gray matter: short, nonmyelinated neurons and cell bodies
white matter: myelinated and nonmyelinated axons
basic pattern found in the CNS: central cavity surrounded by the gray matter, with white matter external to gray
Features: 1. spinal cord exhibits basic pattern yet pattern changes with ascent into brain stem
brain stem has additional gray matter nuclei, within white matter
cerebral hemispheres and cerebellum contain outer layer of gray matter called cortex
Major parts and function of spinal cord
the spinal cord relays sensory, motor, and automatic messages between the brain and rest of the body
myelinated nerves along pathways of spinal cord send electrical signals to each other
initiation of reflexes from ventral horn and lateral horn
gray matter pathways for sensory and motor functions between periphery and brain
divided into 5 sections, cervical, thoracic, lumbar, sacral, anf coccygeal regions
level of injury determine the extent of paralysis and or loss of sensation
contains sympathetic and parasympathetic pathways, response to danger and regulation of bodily functions
hormone release, movement of food, sensations, muscular control to internal organs
Action potential and nerve impulse
principal way neurons send signals
means of long distance neural communication
occur only in muscle cells and axons of neurons
brief reversal of membrane potential with change in voltage
does not decay over distance as graded potential does
in neurons, aka nerve impulses
involves opening of specific voltage-gated channels
Generating an action potential
4 main steps
Resting state- all gated channels are closed
only maintaining resting membrane potential
2 Depolarization
depolarizing local currents open voltage gear Na channels and Na rushes into the cell
Re polarization
channels inactivation gates close
k+ exits cell down its elctrochemical gradient
Hyperpolarizaion
inside of the membrane becomes more negative than in resting state
causes hyper polarization of the membrane
repolarizatuion resets electrical conditions not ionic conditions
Cranial nerves
12 pairs of cranial nerves are associated with brain
2 attach to fore brain, rest with brain stem
most are mixed nerves, 2 pairs purely sensory
olfactory nerves
sensory nerves of smell
fibers synapse
pathway terminates in primary olfactory cortex
optic nerve
pass through optic canals, converge partially cross over at optic
3, oculomotor nerves
fibers extend from ventral mid brain through superior orbital fissures to innervate superior oblique muscle
Trochlear nerves
fibers form dorsal mid brain enter orbits via superior orbital fissures
primarily motor nerves that directs eyeball
Trigeminal nerves
largest cranial nerves, fibers extend from the pons to face
3 divisions
abductions nerves
fibers from inferior pons enter orbits via superior orbital fissure
facial nerves
fibers from pons travel through internal acoustic meatuses
vestibulocochlear nerves
-afferent fibers from hearing receptors and equilibrium receptors
glossophangynral ner
Spinal nerves
31 pairs
all are mixed nerves named for point of issue from spinal cord
supply all body parts except head and part of the neck
8 pairs of cervical nerves
12 pairs of thoracic nerves
5 pairs of lumbar nerves
each spinal nerve is connected to the spinal cord via two roots
ventral root
- contain motor fibers from ventral motor neurons that innervate skeletal muscles
Dorsal root
- contain sensory fibers from sensory neurons in dorsal root ganglia
Neurotransmitters
language of nervous system
50 or more have been identified
most make two or more neurotransmitters
usually released at different stimulate frequencies
classified by chemical structure, function
Exhibit a great diversity of functions
functions grouped into two classifications: effects and actions
Effects; excitatory versus inhibitory
neurotransmitter effects can be excitatory and ion inhibitory
Actions: direct versus indirect
Major neurotransmitters of ANS are acetylcholine and norepinephrine
ACh is released by cholinergic fibers at:
all ANS preganglionic axons
all parasympathetic postganglionic axons
NE released by adrenergic fibers at:
almost all sympathetic postganglionic axons, except those at sweat glands
effectors of neurotransmitter depends on whether it binds to cholinergic receptor or adrenergic receptor
Autonomic nervous system
consists of motor neurons that make adjustments to ensure optimal support for body activities
shunts blood to areas that need it, adjust heart rate
ANS and SNS
both have motor fibers, differ in effectors
somatic nervous system innervates skeletal muscles
ANS innervates cardiac muscle, smooth muscle, and glands
SNS cell body in CNS, single thick and myelinated
extends in spinal or cranial nerves directly to skeletal muscle
ANS
pathway uses two-neuron chain
ganglionic neuron and post ganglionic neuron
-
SNS
all somatic motor neurons release ACh
effect is always stimulatory
ANS
pre ganglionic fibers releas ACh
post release norepinephrine or ACh at effectors
Disorders associated with nervous system
ANS
Hypertension (high blood pressure)
overactive sympathetic vasoconstriction response to stress
-heart must work harder, artery walls are subject to increased wear and tear
Rarynauds disease
painful, exaggerated vasoconstriction in fingers and toes
treated with repudiators
Automatic dysreflexa
life threatening, uncontrolled activation of automatic neuron
Drugs
Drugs of abuse
opioids: cause rush of warmth and pleasure which is then followed by clouded thinking, can also cause itching, nausea, and vomiting
Inhalants: cam in pair coordination, speech, and judgement
MD-MA: can cause and increase in energy and distortions in perceptions.Raises feelings of euphoria
Nicotine: stimulant effects, increases heart rate, for regular uses it calms.highly addictive
Psychedelics: causes hallucination and other distortions. Can be found in nature while others are made in lab
Dissociative drug:causes hallucinations and distortions. Also cause one to loose touch with reality.
Mouse Party
Heroine- interferes with inhibitory neurotransmitter, and dopamine neurotransmitter. Dopamine floods the synapse which produces immediate feelings of sedation and well being
Ecstasy- interferes with serotonin neurotransmitters.Affects serotonin pathways which are responsible for mood, sleep, perception and appetite.
Marijuana- interferes with inhibitor neurotransmitters. Slows down movement which makes the user feel relaxed and calm
Methamphetamine- interferes with dopamine neurotransmitters. Works directly on the brains reward pathway, causes the user to feel pleasure and exhilaration
Alcohol- interferes with GADA inhibitory neurotransmitters and glutamate neurotransmitters. Affects lens of the brain which are involved in memory formation and decision making
Cocaine- interferes with dopamine neurotransmitters. Concentrates in the reward pathway.
LSD- Interfered with serotonin transmitters. Excites a region of the brain known as locus cue rules which can branch to many sensory areas of the brain. Responsible for feelings of wakefulness and evoking responses to unexpected stimuli.