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The Nervous System - Michelle Llamas P.6 - Coggle Diagram
The Nervous System - Michelle Llamas P.6
Major Functions of the nervous system
sensory function
detects changes within body and outside body
integrative function
analyzes sensory information, stores some aspects, and makes decisions regarding inappropriate behavior
motor function
may respond to stimuli by initiating muscular contractions or glandular secretion
muscle glands are called - effectors-
Major divisions and subdivisions of the nervous system
Main divisions
Central nervous system (CNS)
brain and spinal cord
function
receive incoming sensory information
issue instructions
integration of information
thoughts and emotions generated
memories formed and stored
most nerve impulses that influence effector organs begin in CNS
Peripheral Nervous system ( PNS)
all nerves that extend from brain and spinal cord
functions
spinal nerves carry impulses to and from the spinal cord
cranial nerves carry impulses to and from cranium
Two divisions of PNS
Sensory afferent nerves
relay information from skin, muscles and glands to CNS
they are affected by the environment
interneuron: nerves that connect sensory nerves to motor neurons
Motor efferent nerves
carry impulses from CNS to organs, muscles
cause an effect or response
2 types:
Somatic Motor Neurons SNS
conscious voluntary control part of PNS
sense and respond to external environment
brings info from skin, special senses, body wall, and limbs to CNS, & motor neurons to skeletal muscles
Autonomic Motor neurons ANS
automatic, unconscious, involuntary control
respond to internal environment
bring info from receptors in internal organs to CNS and motor neurons to smooth muscle, cardiac muscle and glands
2 Divisions of ANS
sympathetic nervous system
2 more items...
parasympathetic nervous system
3 more items...
Tissues
two major cells make up nervous tissue
Neuroglia
cells that support neurons
do not relay electrical impulses
types of neuroglia :
PNS:
Shwann cells
supply myelin sheathes to axon in PNS
aid in regrowth of damaged peripheral axons
Satellite cells
flattened cells found around cell bodies of neurons in ganglia
protective cell that cushions cell body of neuron
ganglia= bunched up cell bodies in PNS
CNS:
Astrocytes
star shaped cells
protects neurons from harmful substances
maintain blood - brain barrier
control ion, nutrient and gas concentrations
anchor neurons close to blood vessels
Oligodendrocytes
insulate nerve fibers with the production of the myelin sheath
form for neurons of CNS. most common
Microglia
small with few processes
dispose of debris from inflammation in brain by phagocytosis
Ependymal Cells
form from cerebrospinal fluid
line cavities of brain and spinal cord to move CSF
do not lose ability to divide
act in support, guiding development, and stimulation and maintenance
astrocyte >>> rest stops
oligodendrocytes >>> tunnels
microglia >>> janitors, custodians
Neurons- nerve cells
relay electrical impulses throughout the body
cell body >>> train station
axon >>> railway
3 types of Neurons
1. Sensory afferent neurons
transmit impulses to CNS from all parts of the body
have specialized receptor ends at tips of dendrites , most unipolar
2. Motor efferent neurons
impulses away from CNS to effectors of tissue
muscle and glandular epithelial tissues
3. Interneurons
transmit impulses from sensory neurons to motor neurons
multipolar neurons in CNS
Classification of neurons and coverings
3 types of neuron structure :
Multipolar: many dendrites, one axon
Bipolar: one dendrite, one axon (sensory)
Unipolar: fused axon and dendrite (sensory)
3 types of Neurons:
Sensory afferent neurons
Motor efferent neurons
interneurons ( central or connecting) neurons
Nerve
nerves : bundle of peripheral axons in PNS
Tract: bundle of central axons in CNS
White matter: tissue composed primarily of myelinated axons
gray matter: tissue composed primarily of cell bodies and unmyelinated fibers
Nerve Coverings
made up of fibrous connective tissue
Endoneurium: surrounds individual fibers within a nerve
fascicle: a group of nerve fibers
perineurium: surrounds a group of nerve fibers
epineurium: surrounds the entire nerve
Major parts and functions of the spinal cord
two major functions
transmit impulses to and from the brain
houses spinal reflexes
gray matter serves as information highway to and from the brain
gray matter receives and integrates info
Action potential
nerve impulse is transmitted during action potential , only axons are capable of action potential
strong enough stimulation / nerve impulse causes NA+ gates to open >> NA+ rush into cell causing depolarization
if strong enough, depolarization occurs, threshold potential is reached at +30 MV and the impulse is sent down the axon
k+ rushes out of the neuron after Na+ rushes in, causing repolarization of the membrane back to resting potential
Types of responses:
all or none
summation
graded response
refractory period
types of conduction
continuous conduction
unmyelinated axon conducts an impulse over its entire surface
saltatory conduction
myelinated axon "jump" from one node to the next
Cranial nerves and spinal nerves
12 pairs of cranial nerves are associated with brain
most are mixed nerves but two pairs - sensory-
each numbered 1- XII and named from front to back
I- Olfactory : sensory nerve that functions in sense of smell
II- Optic: arises from retina of the eye and function in vision
III-Oculomotor: mostly motor function, muscles of eye, eyelids, and pupillary construction
IV- Trochlear: superior oblique muscle of eye
V- Trigeminal: 3 branches, motor, sensory
VII- Facials: motor to muscles of facial expression, sensory taste
IX- Glossopharyngeal: motor, sensory
X- Vagus: motor, contraction, relaxation, secretion
XI- Accessory:motor, swallowing and movement of head
XII- Hypoglossal- motor- movement of tonque during speech and swallowing
Anatomy of the Spinal Cord
-connection between brain and brainstem to the body
begins at base of brain at the foramen magnum
extends as a slender cord to the level of the intervertebral disc between 1st and 2nd lumbar vertebrae
31 pairs
consist of 31 segments, each gives rise to a pair of spinal nerves
cervical enlargement gives rise to nears going to upper limbs
lumbar enlargement gives rise to innervating lower limbs
ventral roots : motor efferent dibers from ventral horn motor neurons
innervate skeletal muscles
Dorsal roots: sensory afferent fibers from sensory neurons in dorsal root ganglia
conduct impulses from peripheral receptors
Cross Section Anatomy:
two deep longitudinal grooves, anterior median fissure and posterior median sulcus
Neurotransmitters
binds with receptors on the postsynaptic neurons cell membrane
events leading to the release of a neurotransmitter
action potential passes along an axon over the surface of its synaptic knob
2 synaptic knob membrane becomes more permeable to calcium ions, and they diffuse inward
in the presence of calcium ions, synaptic vesicles fuse to synaptic knob membrane
synaptic vesicles release their neurotransmitter into synaptic cleft
30-50 different neurotransmitters identified
synaptic end bulbs contain two or three different neurotransmitters
need to be removed or will influence nerve ; some degraded by enzymes, some some reuptake into cells
Compare and contrast the autonomic nervous system
Somatic motor neuron
conscious, voluntary control
respond to external environment
bring info from skin, special senses, body wall, and limbs to CNS, and motor neurons to skeletal muscles
example: muscles/skin/ sense organs
Autonomic motor neuron ANS
Automatic , involuntary control
-respond to internal environment
bring info from receptors in internal organs to CNS and motor neurons to smooth muscle, cardiac muscle, and gland
example: digestion, blood flow, urination, defecation, glandular secretions, smooth muscle, cardiac muscle
VS.
Reflex arc
reflex: preprogrammed rapid predictable involuntary response to stimuli
functions to prevent damage to the body
may be learned
2 types: Spinal & Cranial
spinal: signal travels through spine
cranial: signals travels through brain stem
Reflex arc:
nerve pathway of a reflex response
5 parts
sensory receptor >> afferent nerve ending detects stimulus
sensory/ afferent neuron >> sends signal to CNS ( reflex center)
synapse/ interneuron integration center >> connection between sensory neuron and motor efferent neuron
Motor/ efferent neuron >> delivers response to target organ effector >> target organ responds to signal