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BASICS OF NEUROBIOLOGY
NERVE ENDINGS
ZSOLT LIPOSITS
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Basics of Neurobiology: Nerve endings
11. előadás. Prof. Liposits Zsolt
NERVE ENDINGS I.
Effectors and receptors
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NERVE ENDINGS
NEURONS COMMUNICATE WITH NON-NEURONAL ELEMENTS VIA SPECIALIZED
NERVE ENDINGS BELONGING TO EFFECTOR AND RECEPTOR CATEGORIES
I. EFFECTORS
1. MOTOR END-PLATE
2. AUTONOMIC FIBER PLEXUS
II. RECEPTORS
1.
2.
3.
4.
5.
6.
MUSCLE RECEPTORS
SENSORY EPITHELIAL CELLS
MECHANORECEPTORS
THERMORECEPTORS
PAIN RECEPTORS
CHEMORECEPTORS
NEURONS COMMUNICATE WITH OTHER NEURONAL ELEMENTS VIA SPECIALIZED
STRUCTURAL AND FUNCTIONAL UNITS
I. SYNAPSES
1. CHEMICAL SYNAPSE
2. ELECTRICAL SYNAPSE
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Basics of Neurobiology: Nerve endings
EFFECTORS
I.
MOTOR ENDPLATE
II. AUTONOMIC FIBER PLEXUS
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MOTONEURON
Motor endplate
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MOTOR ENDPLATE V
IDEG
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IZOM
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Development of the motor endplate
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MOTOR ENDPLATE
AXONS OF SOMATIC MOTONEURONS INNERVATE SKELETAL MUSCLE FIBERS
THE JOINT UNITS OF THE NERVE TERMINALS AND MUSCLE FIBERS ARE CALLED
MOTOR END PLATES. SYNONYMS: MYONEURAL JUNCTION, NEUROMUSCULAR
JUNCTION
MOTONEURONS PROJECTING FROM THE BRAIN STEM AND SPINAL CORD SEND
AXONS TO THE STRIATED MUSCLE FIBERS FOR INNERVATION
THE TERMINAL AXON LOSES ITS MYELIN SHEATH AND THE TERMINAL BOUTONS
JUXTAPOSE TO THE SARCOLEMMA, THE MEMBRANE OF THE MUSCLE FIBER
THE AXON TERMINAL CONTAINS SYNAPTIC VESICLES FILLED WITH THE
NEUROTRANSMITTER ACETYLCHOLINE
ACTIVATION OF THE NERVE TERMINAL LEADS TO THE RELEASE OF THE
TRANSMITTER THAT BINDS TO ITS RECEPTORS EMBEDDED INTO THE MUSCLE
MEMBRANE. THE RECEPTOR ACTIVATION EVOKES CASCADE EVENTS RESULTING IN
THE CONTRACTION OF THE MUSCLE FIBERS
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MOTOR ENDPLATE
ULTRASTRUCTURAL SCHEME OF THE MOTOR END PLATE
SCHWANN CELL
MOTONEURON AXON TERMINAL
SYNAPTIC VESICLE
SARCOLEMMA
MITOCHONDRION
THE MECHANISM OF ACTIVATION OF THE NERVE TERMINAL
FEATURES OF ACETYLCHOLINE RELEASE AND ITS BINDING TO RECEPTORS
INACTIVATION OF THE TRANSMITTER
THE SARCOMERE
POSTSYNAPTIC EVENTS
THE CONTRACTION OF THE SARCOMERES
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THE SMALLEST FUNCTIONAL UNIT OF A MYOFIBRIL
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CELLULAR DETAILS OF THE MUSCLE INNERVATION
THE SILVER IMPREGNATED AXONS APPEAR IN BLACK. THEY SHOW A
REMARKABLE TERMINAL ARBORIZATION. THE THIN, INDIVIDUAL
AXON TERMINALS SPREAD OVER AND INNERVATE STRIATED MUSCLE
FIBERS SHOWN IN ORANGE. THE NERVES CAN TRANSMIT SENSORY
INFORMATION TO THE CNS AND ALSO CONVEY MOTOR COMMANDS
FROM THE CNS TO THE MUSCLE FIBERS
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Acetylcholine neurotransmission
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The Animation
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The Players
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MODEL OF MUSCLE CONTRACTION
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THE AUTONOMIC PLEXUS
POSTGANGLIONIC NERVE FIBERS OF THE SYMPATHETIC AND PARASYMPATHETIC
BRANCHES OF AUTONOMIC NERVOUS SYSTEM INNERVATE THE CARDIAC MUSCLE,
SMOOTH MUSCLE BUNDLES OF VISCERAL ORGANS AND GLANDS
THESE AXONS DO NOT ESTABLISH SYNAPSES WITH THE TARGET CELLS
THEY RELEASE THE TRANSMITTER INTO THE EXTRACELLULAR SPACE FROM THEIR
AXON VARICOSITIES
SPECIFIC RECEPTORS OF THE TARGET CELLS PICK UP THE TRANSMITTERS AND
INITIATE THE CELLULAR RESPONSES
INNERVATION OF SMOOTH MUSCLE CELLS
BY AN AUTONOMIC NERVE FIBER. SMOOTH
MUSCLE CELLS ARE COUPLED BY GAP
JUNCTION, ARROWS INDICATE THE OUTFLOW
OF THE TRANSMITTER.
BEADED AXON
TRANSMITTER-CONTAINING VESICLES
SMOOTH MUSCLE CELLS
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Non-synaptic transmitter release
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Smooth
muscle
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Salivary gland
Innervation
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RECEPTORS
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MUSCLE RECEPTORS
THE ACTUAL STRETCHING STATE OF MUSCLE AND TENDON FIBERS IS
CONTINUOUSLY MONITORED BY THE CNS USING THE MUSCLE SPINDLE AND
GOLGI TENDON RECEPTORS
MUSCLE SPINDLE IS A CAPSULATED RECEPTOR COMPOSED
OF SPECIAL, THIN STRIATED MUSCLE FIBERS. THE STRUCTURE
IS EMBEDDED AMONG EXTRAFUSAL MUSCLE FIBERS.
THE STRETCHING OF THE EXTRAFUSAL MUSCLE FIBERS
ACTIVATES THE RECEPTOR THAT INFORMS THE CNS AND
EVOKES THE COMPENSATORY ACTION, THE CONTRACTION
GAMMA MOTONEURON
NERVE FIBERS
SENSORY TYPE Ia
NERVE FIBERS
SENSORY TYPE II
NERVE FIBERS
NUCLEAR BAG
MUSCLE FIBER
THE MUSCLE SPINDLE CONSISTS OF NUCLEAR
BAG AND NUCLEAR CHAIN MUSCLE FIBERS.
BOTH FIBER TYPES RECEIVE MOTOR (GAMMA)
AND SENSORY (Ia and II) NERVES
NUCLEAR CHAIN
MUSCLE FIBER
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The stretch reflex
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SCHEME OF THE SPINAL STRETCH REFLEX
A
B
g
a
C
MUSCLE SPINDLES ARE THE RECEPTORS OF THE
SPINAL STRETCH REFLEX. IT RECEIVES MOTOR
AND SENSORY INNERVATIONS . THE EXTRAFUSAL
MUSCLE FIBERS ARE INNERVATED BY ALPHA
MOTONEURONS
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IT IS A MONOSYNAPTIC REFLEX PROVIDING
AUTOMATIC REGULATION OF SKELETAL
MUSCLE LENGTH
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SENSORY EPITHELIAL CELLS
SENSORY EPITHELIAL CELLS ARE CAPABLE OF SENSING SPECIAL STIMULI (ODOR,
FLAVOR, LIQUID MOVEMENT). THEY ARE RELATED TO THE SPECIAL SENSE ORGAN
SYSTEM. PRIMARY SENSORY CELLS CONVEY THE INFORMATION TO THE CNS BY
THEIR OWN PROCESSES, SECONDARY SENSORY CELLS FORWARD THE INFORMATION BY THE PERIPHERAL PROCESSES OF SENSORY GANGLION NEURONS
MECHANORECEPTORS
THEY ARE SENSORY RECEPTORS THAT RESPOND TO PRESSURE AND
DISTORTION. MECHANORECEPTORS ARE NUMEROUS IN THE SUPERFICIAL
AND DEEP LAYERS OF THE SKIN. THEY ARE EITHER FREE OR ENCAPSULATED
NERVE ENDINGS. CHARACTERISTIC MEMBERS INCLUDE: FREE NERVE ENDINGS,
MEISSNER’S-, KRAUSE’S- , PACININIAN CORPUSCULES, AND RUFFINI BODIES
FEATURES OF RECEPTOR POTENTIALS
AMPLITUDE
SIGNAL INTENSITY
ADAPTATION
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CNS
RECEPTOR
STIMULUS
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THERMORECEPTORS
SENSORY RECEPTORS THAT CODE ABSOLUTE AND RELATIVE CHANGES IN
TEMPERATURE. THEY ARE FREE-NERVE ENDINGS OF UNMYELINATED AND THIN
MYELINATED FIBERS. THERE ARE COLD AND WARM SENSITIVE TYPES
THE COLD RECEPTOR: TRANSIENT RECEPTOR POTENTIAL ION CHANNELS (TRPM8)
PAIN RECEPTORS
SENSORY RECEPTORS THAT RESPOND TO TISSUE DAMAGING NOXIOUS STIMULI.
THEY ARE ALSO ADDRESSED AS NOCICEPTORS. THEY PLAY A PIVOTAL ROLE IN
AVOIDING THE HARMFUL INSULTS OF THE ENVIRONMENT AND HELP TO PRESERVE
THE INTEGRITY OF THE BODY. THE ACTIVATION OF NOCICEPTORS ALARMS THE
BODY. THEY HAVE FAST AND SLOW CONDUCTING SYSTEMS. THEY ARE
INTEGRATED WITHIN THE NOCICEPTOR REFLEX ARC
CHEMORECEPTORS
SENSORY RECEPTORS THAT MONITOR CHANGES IN THE CHEMICAL COMPOSITION
OF THE CIRCULATING BLOOD. THEY SENSE OXYGEN, CARBON DIOXIDE
SATURATION AND pH. THEY CONTRIBUTE TO THE REGULATION OF RESPIRATION
AND CIRCULATION
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Receptors in the skin
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Baroreceptors and chemoreceptors
Carotid body
Aortic arch
Wall of heart
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