Download anatomi sistem saraf dan indera a

ANATOMI SISTEM SARAF
DAN INDERA
BAMBANG SOEMANTRI
Anatomical Organization of the Nervous
system
• Central Nervous system :
– Brain
– Spinal cord
• Peripheral nervous system
– Ganglion
– Cranial nerves
– Spinal nerves
Nervous system includes all neural tissue
in body
• Central Nervous System
– Brain and spinal cord
• Peripheral Nervous System
– All neural tissue outside CNS
Cells in Nervous Tissue
• Neurons
• Neuroglia
Neuroglia (Neuroglial Cells)
Central Neuroglia
Astrocyte
protoplasmic astrocyte
fibrous astrocyte
Oligodendrocyte
perineuronal satellite cell
interfascicular cell
Microglia
Ependymal Cell
Peripheral Neuroglia
Schwann Cell
in peripheral nerve
and ganglion
Capsular (Satellite) Cell
in ganglion
Neurons
•what is the main defining characteristic of neurons?
•have the property of electrical excitability - ability to produce
action potentials or impulses in response to stimuli
Representative Neuron
1. cell body or soma
-single nucleus with prominent nucleolus
-Nissl bodies
-rough ER & free ribosomes for protein
synthesis
-proteins then replace neuronal cellular
components for growth
and repair of damaged axons in the PNS
-neurofilaments or neurofibrils
give cell shape and support bundles of
intermediate filaments
-microtubules move material
inside cell
-lipofuscin pigment clumps
(harmless aging) - yellowish
brown
Neurons
2. Cell processes =
dendrites (little trees)
- the receiving or input
portion of the neuron
-short, tapering and
highly branched
-surfaces specialized
for contact with other
neurons
-cytoplasm contains
Nissl bodies &
mitochondria
3. Cell processes = axons
•
•
•
•
•
•
•
•
•
•
•
Conduct impulses away from cell bodypropagates nerve impulses to another
neuron
Long, thin cylindrical process of cell
contains mitochondria, microtubules &
neurofibrils - NO ER/NO protein synth.
joins the soma at a cone-shaped elevation =
axon hillock
first part of the axon = initial segment
most impulses arise at the junction of the
axon hillock and initial segment = trigger
zone
cytoplasm = axoplasm
plasma membrane = axolemma
Side branches = collaterals arise from the
axon
axon and collaterals end in fine processes
called axon terminals
Swollen tips called synaptic end bulbs
contain vesicles filled with neurotransmitters
Functional Classification of Neurons
• Sensory (afferent) neurons
– transport sensory information from skin, muscles,
joints, sense organs & viscera to CNS
• Motor (efferent) neurons
– send motor nerve impulses to muscles & glands
• Interneurons (association) neurons
– connect sensory to motor neurons
– 90% of neurons in the body
Sensory Neurons
• Afferent division of PNS
• Deliver sensory information from sensory receptors to CNS
– free nerve endings: bare dendrites associated with pain, itching, tickling,
heat and some touch sensations
– Exteroceptors: located near or at body surface, provide information about
external environment
– Proprioceptors: located in inner ear, joints, tendons and muscles, provide
information about body position, muscle length and tension, position of
joints
– Interoceptors: located in blood vessels, visceral organs and NS
-provide information about internal environment
-most impulses are not perceived – those that are,
are interpreted as pain or pressure
Motor Neurons
• Efferent pathways
• Stimulate peripheral structures
– Somatic motor neurons
• Innervate skeletal muscle
– Visceral motor neurons
• Innervate all other peripheral effectors
• Preganglionic and postganglionic neurons
-both divisions
-first neuron h
(Pre-ganglioni
-second neuro
ganglion (Post
-parasy
-crani
-prega
of the
-short
Motor Units
• Each skeletal fiber has only ONE NMJ
• MU = Somatic neuron + all the skeletal
muscle fibers it innervates
• Number and size indicate precision of
muscle control
• Muscle twitch
– Single momentary contraction
– Response to a single stimulus
• All-or-none theory
– Either contracts completely or not at
all
• Motor units in a whole muscle fire asynchronously
some fibers are active others are relaxed
delays muscle fatigue so contraction can be sustained
•
Muscle fibers of different motor units are intermingled so that net distribution of force
applied to the tendon remains constant even when individual muscle groups cycle
between contraction and relaxation.
Structural Classification of Neurons
• Based on number of processes found on cell body
– multipolar = several dendrites & one axon
• most common cell type in the brain and SC
– bipolar neurons = one main dendrite & one axon
• found in retina, inner ear & olfactory
– unipolar neurons = one process only, sensory only (touch, stretch)
• develops from a bipolar neuron in the embryo - axon and dendrite fuse and
then branch into 2 branches near the soma - both have the structure of axons
(propagate APs) - the axon that projects toward the periphery = dendrites
Structural Classification of Neurons
• Named for histologist that first described them or
their appearance
•Purkinje = cerebellum
•Renshaw = spinal cord
• others are named for shapes
e.g. pyramidal cells
Classification of neurons by cell size
• 1. golgi type I :
– Neurons have a long axon and large soma
• 2. Golgy type II :
– Neurons have short axon undergoes extensive
terminal aeborization and small soma
Synaptic Communication
Synapses
• Are the sites of impulse transmission between
the presynaptic and post synaptic
• Impuls transmission at synapse can occur:
– Electrically
– chemically
Electrical synapse
• Uncommon in mammals
• They are present in the brain stem, retina and
cerebral cortex
• Electrical synapses are usually represented by
gap junction that permit free movement of
ion from one cell to another
• Impulse transmission is much faster across
electrical synapse than across chemical
synapse
Chemical synapse
• Most common mode of communication between two
nerve cells
• Presynaptic membrane release one or more
neurotransmitters into synaptic cleft
• Neurotransmitter diffuses across the synaptic cleft to
ion-channel receptor on the postsynaptic membrane
• Binding of the neurotransmitter to the receptors
initiates the opening ion channels, which permits the
passage of certain ions, altering the permeability of the
postsynaptic membrane and reversing its membrane
potentials
Tipes of synapses
• Axodendritic:
– Between an axon and a dendrite
• Axosomatic:
– Between an axon and a soma
• Axoaxonic:
– Between two axon
• Dendrodendritic:
– between two dendrites
Synaptic morphology
• Presynaptic membrane:
– Contains metochondria, a few elements of SER,
and an abundance of synaptic vesicles.
• Synaptic cleft
• Postsynaptic membrane:
– Contains neorotransmitter receptors
Nerve ending – nerve terminal
• Two structural type :
– 1. Motor ending ( terminal of axon )
• Transmit impulses from the CNS to skeletal &
smooth muscle & to glands ( secretory ending)
– 2. sensory ending = sensory receptor =
terminal of dendrites :
• Perceive various stimuli and transmit this input to
the CNS
continued
• These sensory receptor are classified into
three type depending on the source of the
stimulus, and are components of the
general or special somatic and visceral
afferent pathway :
– Exteroceptors
– Proprioceptors
– interoceptors
Exteroceptors
• Location : near the body surface
• Specialized to perceive stimuli from the external
environment
• These receptors sensitive to :
–
–
–
–
Temperature
Touch
Pressure and
Pain
• Are component of the general somatic afferent
continued
• Special somatic afferent :
– Specialized for light ( sense of vision) and
sound (sense of hearing)
• Special visceral afferent modality :
– Specialized for smell and taste
Proprioceptors
• Are specialized receptor located in joint
capsules, tendon and intrafusal fibers
within muscle.
• These general somatic afferent receptors
transmit sensory input to the CNS, which
translated into information that relates to
an awareness of the body in space and
movement
continued
• Vestibular (balance) mechanism, located
within the inner ear, are specialized for
receiving stimuli related to motion vectors
within the head.
Interoceptors
• Are specialized receptors that perceive
sensory information from within organs of
the body.
Mechanoreceptors
• Mechanoreceptors respond to mechanical
stimuli that may deform the receptor or the
tissue surrounding the receptor.
• Stimuli that trigger the mechanoreceptors
are touch, stretch, vibration and pressure
Nonencapsulated mechanoreceptors
• Are simple unmyelinated receptors present
in the skin, connective tissues and
surrounding hair follicle
– Peritricial nerve ending, located in the
epidermis of the skin, especially in the face and
cornea of the eye
– Merckel’s disks, specialized for perceiving
discriminatory touch, located in non hairy skin
and regions of the body more sensitive to
touch.
Encapsulated mechanoreceptors
• Encapsulated Mechanoreceptors exhibit characteristic
structure and are present in specific location
– 1. Meissner’ corpuscles :
• Specialist for tactile
• Location : dermal papillae of the non hair portin of
the hand, eyelids, lip, tongue, nipples, skin of the
foot and forearm.
• Each corpuscle is formed by three or four nerve
terminals and their associated Schwann cells, all
which are encapsulated by connective tissue.
continued
– 2. Pacinian corpuscles
• Location : in the dermis and hypodermis in the
digits of the hand, breast, connective tissue of the
joint, periosteum and the mesentery
• Spezialied to perceive pressure, touch and fibration
• Morphology :
– ovoid & large receptor
– Single unmyelinated fiber as a core and its
Schwann cell
– Surrounded by approximately 60 layers of
modified fibroblast
– Each layer separated by a small fluid-filled space
– 3. Ruffini’s corpuscle
• Location : in the dermis of skin, nail beds,
periodontal ligament and joint capsules
• Composition :
– branched nonmyelinated terminals
interspersed with collagen fibers
– Surrounded by four to five layers of modified
fibroblast
– 4. Krause’s end bulb
• Morphology :
– Spheris
– Unmyelinated nerve ending
• Location : papilla dermis, joints,
conjunctiva, peritoneum, genital regions,
subendothelial c.t. of the oral and nasal
cavities
• Function : unknown, they were thought to
be receptors sensitive to cold
Muscle spindles and Golgi tendon organs
• Muscle spindles provide feedback concerning the
changes and the rate alteration of the muscle
length
• Golgi tendon organs monitor the tension and the
rate at which the tension is being produced
during movement
• Information from these two sensory structures is
processed at the unconscious level within the
spinal cord; the information also reaches the
cerebellum & cerebral cortex, so that individual
may sense muscle position.
ANATOMI SISTEM SARAF DAN
INDERA B
The Special Senses
BAMBANG SOEMANTRI
The Five Special Senses:
• Smell and taste: chemical senses
(chemical transduction)
• Sight: light sensation (light
transduction)
• Hearing: sound perception
(mechanical transduction)
• Equilibrium: static and dynamic
balance (mechanical transduction)
The Chemical Senses:
Taste and Smell
• The receptors for taste (gustation) and
smell (olfaction) are chemoreceptors
(respond to chemicals in an aqueous
solution)
• Chemoreception involves chemically gated
ion channels that bind to odorant or food
molecules
Taste
3 Types of Lingual Papillae
1. Filiform papillae:
– provide friction
– do not contain taste buds
2. Fungiform papillae:
– contain 5 taste buds each
3. Circumvallate papillae:
– contain 100 taste buds each
Location of Taste Buds
• Located mostly on
papillae of tongue
• Three of the types of
papillae:
– fungiform
– Circumvallate
– Filiform
Taste Buds
• Each papilla contains
numerous taste buds
• Each taste bud contains
many gustatory cells
• The microvilli of gustatory
cells have chemoreceptors
for tastes
The Five Basic Tastes
• Sweet: sugars, alcohols, some amino acids, lead salts
• Sour: H+ ions in acids
• Salty: Na+ and other metal ions
• Bitter: many substances including quinine, nicotine,
caffeine, morphine, strychnine, aspirin
• Umami: the amino acid glutamate (“beef” taste)
Gustatory pathway
• Facial nerve (anterior 2/3 of
tongue) & Glossopharyngeal
nerve (posterior 1/3 of
tongue)solitary nucleus of
medulla (initiate PsNS reflexes
to trigger saliva & gastric
secretion)thalamusgustator
y cortex of parietal lobes
– Fibers also project to the
hypothalamus & limbic system
(enjoyment)
Influence of Other Sensations on Taste
• Taste is 80% smell
• Thermoreceptors, mechanoreceptors,
nociceptors also influence tastes
• Temperature and texture enhance or detract
from taste
Smell
Both smell and taste use chemoreceptors.
Of all the senses, only smell and taste have
fibers that run to both cortical areas
And the limbic system.
Smell
• Olfactory epithelium =
primary sensory organ
– Found on roof of nasal
cavity
– Olfactory receptors are one
of the few neurons to
renew thru adult life
(replaced ~every 60 days)
– Covered w/mucus to
dissolve airborne odor
molecules
Location of Olfactory (Odor) Receptors
Odor Receptors
• Bipolar neurons
• Collectively constitute
cranial nerve I
• Unusual in that they
regenerate (on a ~60 day
replacement cycle)
Olfactory receptors
• Smell is difficult to
research
• At least 1000 ‘smell
genes’ active only in
the nose
• Extremely sensitive
• Nasal cavity also
contains pain
receptors (ammonia,
chili peppers,
menthol, etc)
Olfactory receptors are bipolar neurons.
•Are replaced throughout lifetime, but lost at the
rate of about 1 % per year.
•The cilia, or olfactory hairs are the sensitive portions
•Chemical must be dissolved in watery mucus to
stimulate the receptor.
•Combinations of primary scents allow us to recognize
thousands of different odors.
Olfactory pathway
• Olfactory nerve (axons of receptor cells)
synapse in olfactory bulb (on cribriform
plate)olfactory tract (w/in bulb)
– 1. Thalamusolfactory cortex (frontal lobe) where
smells consciously interpreted and identified
– 2. (subcortical) hypothalamus/amygdala/limbic
system to elicit emotional responses to odors
• Danger (fight or flight), appetizing (GI stimulation),
reflexes such as sneezing/choking/breathing (ammonia)
Odors
• Very complicated
• Humans can distinguish thousands
• More than a thousand different odorantbinding receptor molecules have been
identified
• Different combinations of specific
molecule-receptor interactions produce
different odor perceptions
Transduction of Smell
• Binding of an odorant molecule to a specific receptor
activates a G-protein and then a second messenger (cAMP)
• cAMP causes gated Na+ and Ca2+ channels to open, leading
to depolarization
•
Anosmia: absence of the sense of smell
– Trauma
– Colds or allergies producing excessive mucus
– Polyps causing blockage
– 1/3 are from zinc deficiency
68
Vision
Overview of the Eye
• Eye acts much like a camera
– Lens of eye adjusts to bring object into focus
– Pupil of eye constricts to allow less light to enter
in bright setting or dilates to allow more light to
enter in darker setting
– Through bending of light rays, image reaches
retina
• Sensitive nerve cell layer of eye
• Image is transmitted to brain for interpretation
Surface Anatomy of the Eye
• Eyebrows divert sweat from the eyes and contribute to
facial expressions
• Eyelids (palpebrae) blink to protect the eye from foreign
objects and lubricate their surface
• Eyelashes detect and deter foreign objects
Conjunctiva
• A mucous membrane lining the
inside of the eyelids and the
anterior surface of the eyes
– forms the conjunctival sac
between the eye and eyelid
• Forms a closed space when the
eyelids are closed
• Conjunctivitis (“pinkeye”):
inflammation of the conjunctival
sac
The Lacrimal Apparatus
• Lacrimal Apparatus:
– lacrimal gland
– lacrimal sac
– nasolacrimal duct
• Rinses and lubricates the
conjunctival sac
• Drains to the nasal cavity
where excess moisture is
evaporated
Internal Anatomy of the Eye--Tunics
• Fibrous tunic: sclera & cornea
• Vascular tunic: choroid layer
• Sensory tunic: retina
3 Layers of the Eye
Figure 17–4b
Internal Anatomy of the Eye
• Anterior Segment contains
the Aqueous Humor
–
–
–
–
Iris
Ciliary Body
Suspensory Ligament
Lens
• Posterior Segment contains
the Vitreous Humor
3 Layers of the Eye
Figure 17–4c
Autonomic Regulation of the Iris
Pupil
Constricts
Pupil
Dilates
The Two Layers of the Retina
• Outer pigmented layer has a
single layer of pigmented cells,
attached to the choroid tunic,
which absorbs light to prevent
light scattering inside
• Inner neural layer has the
photosensory cells and various
kinds of interneurons in three
layers
Neural Organization in the Retina
• Photoreceptors: rods (for
dim light) and cones (3
colors: blue, green and
red, for bright light)
• Bipolar cells are
connecting interneurons
• Ganglion cells’ axons
become the Optic Nerve
Neural Organization in the Retina
• Horizontal Cells enhance
contrast (light versus dark
boundaries) and help
differentiate colors
• Amacrine cells detect
changes in the level of
illumination
The Optic Disc
• Axons of ganglion cells exit
to form the optic nerve
• Blood vessels enter to
serve the retina by running
on top of the neural layer
• The location of the “blind
spot” in our vision
Micrograph of the Retina
• Light must cross
through the
capillaries and the
two layers of
interneurons to reach
the photoreceptors,
the rods and cones
Light
Opthalmoscope Image of the Retina
• The Macula Lutea (“yellow
spot”) is the center of the visual
image
• The Fovea Centralis is a central
depression where light falls
more directly on cones providing
for the sharpest image
discrimination
• Light bouncing off RBCs’
hemoglobin causes “red eye” in
flash photos
Auditory sensations and Equilibrium
Hearing and equilibrium rely on mechanoreceptors
The ear is divided into three parts:
• Outer ear
• Middle ear
• Inner ear
Anatomy of Ear
HEARING
ONLY
HEARING
&
BALANCE
Hearing
Sound waves > eardrum > ossicles >
oval window > set fluid in motion >
vibrations stimulate “hair
cells”
> cochlear
Within
Cochlear
duct,
membranous
labyrinth
nerve transmits impulse
to midbrain
> is
Spiral
Organ of
Corti –
auditory cortex of
temporal
lobe
hearing receptors or “hair
cells”
Figure 8.15
•The ossicles (malleus, incus, and stapes)transmit the vibratory
motion from the eardrum to the oval window. The auditory tube
allows pressure to be equalized on both sides of the eardrum.
These structures are also involved with sound transmission only.
INNER EAR : Bony chambers
• Cochlea –
hearing
• Vestibule – static equilibrium
• Semicircular canals – dynamic equilibrium
•The bony labyrinth contains perilymph and membranous sacs
filled with endolymph. Within the membranous sacs of the
vestibule and semicircular canals are equilibrium receptors.
Hearing receptors are found within the membranes of the cochlea.
• Hair cells of the organ of Corti (the receptor for hearing
within the cochlea) are stimulated by sound vibrations
transmitted through air, membranes, and fluids
• Deafness is any degree of hearing loss. Conduction deafness
results when the transmission of sound vibrations through
the external and middle ears is hindered. Sensorineural
deafness occurs when there is damage to the nervous
system structures involved in hearing.
• Receptors of the semicircular canals (cristae) are dynamic
equilibrium receptors, which respond to angular or
rotational body movements. Receptors of the vestibule
(maculae) are static equilibrium receptors, which respond to
the pull of gravity and report on head position. Visual and
proprioceptor input are also necessary for normal balance.
• Symptoms of equilibrium apparatus problems include
involuntary rolling of the eyes, nausea, vertigo, and an
inability to stand erect.
Equilibrium – Balance
Static equilibrium – maintenance of body
posture relative to gravity while the body
is still.
Dynamic equilibrium – maintenance of
the body posture (mainly the head) in
response to sudden movements. Tracking
a moving object.
Static Equilibrium
•Inside the vestibule are two chambers : utricle
and saccule.
•Regions of hair cells and supporting cells called
maculae.
•Otoliths – “ear rocks”
Dynamic Equilibrium
•Semicircular canals
•In ampulla is the crista ampullaris – contains
hair cells and supporting cells covered by a
gelatinous mass called the cupula.
•Neurological connections between eyes and
semicircular canals – for tracking
•Nystagmus
Dynamic Equilibrium
•
•
•
•
•
Receptors found in semicircular canals
Respond to angular or rotatory movements
Oriented in 3 planes
Ampulla, Crista Ampullaris, Cupula
Movement constant rate, adapts
Figure 8.14