AB THE NERVOUS SYSTEM . B. HELP THE BODY MAINTAIN HOMEOSTASIS. 1.THE GENERAL FUNCTIONS OF THE NERVOUS SYSTEM INCLUDE A. REGULATE AND CONTROL BODY FUNCTIONS . B. HELP THE BODY MAINTAIN HOMEOSTASIS. C. SENSES, INTERPRETS AND RESPONDS TO STIMULI. D. PROCESSES, STORES AND REMEMBERS INPUT.
2. STRUCTURAL DIVISIONS OF THE NERVOUS SYSTEM: A. CENTRAL NERVOUS SYSTEM (CNS)= BRAIN AND SPINAL CORD. B. PERIPHERAL NERVOUS SYSTEM (PNS) = RECEPTORS – SPECIALIZED NERVE ENDINGS THAT RESPOND TO STIMULI, NERVES – BUNDLES OF NEURON AXONS AND GANGLIA – COLLECTIONS OF NERVE CELL BODIES.
Sensory input Sensor Integration Motor output Effector Peripheral nervous system (PNS) Central nervous system (CNS)
CNS + PNS CNS
A. SENSORY DIVISION – CARRIES 3. DIVISIONS OF THE PNS A. SENSORY DIVISION – CARRIES IMPULSES TO THE CNS FROM SENSORY RECEPTORS. (AFFERENT=INCOMING NERVES) B. MOTOR DIVISION – CARRIES NERVE IMPULSES FROM THE CNS TO EFFECTOR ORGANS. (EFFERENT= OUT GOING NERVES) 1. SOMATIC MOTOR – INNER- VATES SKELETAL MUSCLE. 2. AUTONOMIC MOTOR – INNER- VATES SMOOTH & CARDIAC.
4. NERVE CELLS – NEURON – HAS CELL BODY WITH NUCLEUS, DENDRITES = ROOT-LIKE PROJECTIONS, AND THE AXON WHICH CAN DIVIDE AT THE END INTO THE AXON TREE. - THE AXON MAY BE MYELINATED = COATED WITH FATTY MATERIAL THAT ACTS AS AN INSULATOR. IT IS CREATED BY ROLLING FLATTENED SCHWANN CELLS AROUND THE AXON. SPACES BETWEEN = NODES
LE 48-5 Dendrites Cell body Nucleus Synapse Signal direction Axon hillock Axon Presynaptic cell Synaptic terminals Myelin sheath Postsynaptic cell
LE 48-8 Nodes of Ranvier Layers of myelin Axon Schwann cell Schwann Nucleus of Schwann cell Myelin sheath 0.1 µm
-Neurons also have “helper” cells called glia. Glia are essential for structural integrity of the nervous system and for functioning of neurons Types of glia: astrocytes, radial glia, oligodendrocytes, and Schwann cells
5. TYPES OF NEURONS: SENSORY, INTERNEURON AND MOTOR. Gray matter Cell body of sensory neuron in dorsal root ganglion Quadriceps muscle White matter Hamstring muscle Spinal cord (cross section) Sensory neuron Motor neuron Interneuron
Varieties of neurons LE 48-6 Dendrites Axon Cell body Sensory neuron Interneurons Motor neuron
6. MEMBRANE POTENTIAL = CHARGE DIFFERENCE BETWEEN THE INSIDE AND OUTSIDE OF THE MEMBRANE OF A NERVE CELL. Microelectrode –70 mV Voltage recorder Reference electrode
-MORE Na+ IN THE EXTRACELLULAR FLUID AND MORE K+ INSIDE. THE MEMBRANE IS MORE PERMEABLE TO K+ SO IT LEAKS OUT GIVING THE OUTSIDE A POSITIVE CHARGE.
-THE INSIDE OF THE NEURON HAS AN OVERALL NEGATIVE CHARGE BECAUSE IT HAS MANY, LARGE NEGATIVE PROTEINS INSIDE.
7. TYPICALLY THE CHARGE DIFFERENCE BETWEEN INSIDE AND OUTSIDE IS –70 mv AT RESTING POTENTIAL.
[Na+] 150 mM [K+] 150 mM [Cl–] 120 mM [A–] 100 mM LE 48-10 CYTOSOL EXTRACELLULAR FLUID [Na+] 15 mM [Na+] 150 mM [K+] 150 mM [K+] 5 mM [Cl–] 120 mM [Cl–] 10 mM [A–] 100 mM Plasma membrane
8. ACTION POTENTIAL (NERVE IMPULSE)= A CHANGE IN THE POLARITY ACROSS THE MEMBRANE BROUGHT ABOUT BY A STIMULUS.
Gated ion channels open or close in response to one of three stimuli: -Stretch-gated ion channels open when the membrane is mechanically deformed. -Ligand-gated ion channels open or close when a specific chemical binds to the channel. -Voltage-gated ion channels respond to a change in membrane potential.
-IN RESPONSE, Na+ GATES OPEN, Na+ RUSHES INTO THE CELL. THEN INSIDE IS POSITIVE AND THE OUTSIDE IS NEGATIVE = REVERSAL OF CHARGE CALLED DEPOLARIZATION. NEXT: K+ GATES OPEN, K+ OUT OF THE CELL = REPOLARIZATION.
-WAVE OF POLARIZATION AND DEPOLARIZATION TRAVELS THE AXON AND IS CALLED AN ACTION POTENTIAL. 9. DURING DEPOLARIZATION, THE CHARGE SHIFTS FROM –70MV TO +30MV. 10. REFRACTORY PERIOD – PERIOD OF REST BEFORE A NEURON CAN BE STIMULATED TO FIRE AGAIN.
LE 48-13_5 Na+ Na+ Na+ Na+ K+ Rising phase of the action potential K+ Falling phase of the action potential +50 Action potential Na+ Na+ Membrane potential (mV) –50 Threshold K+ Resting potential –100 Depolarization Time Na+ Na+ Extracellular fluid Potassium channel Activation gates Na+ K+ Plasma membrane Undershoot Cytosol Sodium channel K+ Inactivation gate Resting state
LE 48-14c Axon Action potential An action potential is generated as Na+ flows inward across the membrane at one location. Action potential K+ Na+ K+ The depolarization of the action potential spreads to the neighboring region of the membrane, re-initiating the action potential there. To the left of this region, the membrane is repolarizing as K+ flows outward. Action potential K+ Na+ K+ The depolarization-repolarization process is repeated in the next region of the membrane. In this way, local currents of ions across the plasma membrane cause the action potential to be propagated along the length of the axon.
11. IN MYELINATED NEURONS, THE ACTION POTENTIALS ONLY OCCUR AT THE NODES. THE NEURAL IMPULSE JUMPS FROM ONE NODE TO THE NEXT. THIS INCREASES THE SPEED AND IS CALLED SALTATORY PROPAGATION.
12. SYNAPSE – WHERE 2 NEURONS MEET OR WHERE A NEURON CONTACTS MUSCLE OR GLAND TISSUE. THE AP IS RELAYED FROM ONE TO THE NEXT. Synaptic terminals of pre- synaptic neurons Postsynaptic neuron 5 µm
13. REVIEW PARTS OF A SYNAPSE – PRESYNAPTIC TERMINAL, VESICLES CLEFT, RECEPTOR PROTEINS, AND POSTSYNAPTIC TERMINAL.
14. THE SPINAL CORD A. COMMUNICATION LINK BETWEEN THE BRAIN AND THE BODY. B. INTEGRATES SOME INFO. CONTROLLING SPINAL REFLEXES. C. EXTENDS FROM BASE OF BRAIN (FORAMEN MAGNUM) TO SECOND LUMBAR VERTEBRAE.
15. THERE ARE 31 SPINAL NERVES THAT BRANCH OFF THE SPINAL CORD. 16. GRAY MATTER- INTERIOR OF SPINAL CORD - COMPRISED OF NERVE CELL BODIES. ORGANIZED INTO HORNS: DORSAL HORNS= SENSORY NEURONS SYNAPSE WITH ASSOCIATION NEURONS. VENTRAL HORNS= CELL BODIES OF MOTOR NEURONS. 17. WHITE MATTER - SURROUNDS GRAY MATTER AND CONTAINS TRACKS.
18. ASCENDING TRACKS- CARRY SENSORY INFO. TO THE BRAIN. 19. DESCENDING TRACKS - CARRY MOTOR COMMANDS FROM THE BRAIN TO THE BODY. 20. REFLEXES ARE AUTONOMIC RESPON- SES TRIGGERED BY SPECIFIC STIMULI. A. SENSORY RECEPTOR STIMULATED. B. SENSORY NEURON CARRIES IMPULSE TO THE CNS. C. ASSOCIATION NEURON CONNECTS SENSORY NEU. TO MOTOR NEURON
D. MOTOR NEURON EXTENDS FROM SPINAL CORD TO EFFECTOR. E. EFFECTOR ORGAN (MUSCLE OR GLAND) RESPONDS.
21. AUTONOMIC NERVOUS SYSTEM A. RESPONSIBLE FOR INVOLUNTARY ORGAN CONTROL. B. MOTOR NEURONS TO GLANDS CARDIAC AND SMOOTH MUSCLE. 22. SYMPATHETIC DIVISION - FIGHT OR FLIGHT SYSTEM. INC. HEARTRATE, RELEASE EPINEPHRINE, SWEAT ETC.
23. PARASYMPATHETIC DIVISION - OPPOSITE OF SYMPATHETIC. BRINGS BODY BACK TO NORMAL RANGE AFTER FIGHT OR FLIGHT RESPONSE IS OVER.
LE 48-22 Parasympathetic division Sympathetic division Action on target organs: Action on target organs: Constricts pupil of eye Dilates pupil of eye Location of preganglionic neurons: brainstem and sacral segments of spinal cord Location of preganglionic neurons: thoracic and lumbar segments of spinal cord Stimulates salivary gland secretion Inhibits salivary gland secretion Sympathetic ganglia Constricts bronchi in lungs Relaxes bronchi in lungs Cervical Neurotransmitter released by preganglionic neurons: acetylcholine Neurotransmitter released by preganglionic neurons: acetylcholine Slows heart Accelerates heart Inhibits activity of stomach and intestines Location of postganglionic neurons: in ganglia close to or within target organs Stimulates activity of stomach and intestines Thoracic Location of postganglionic neurons: some in ganglia close to target organs; others in a chain of ganglia near spinal cord Inhibits activity of pancreas Stimulates activity of pancreas Stimulates glucose release from liver; inhibits gallbladder Stimulates gallbladder Lumbar Neurotransmitter released by postganglionic neurons: acetylcholine Stimulates adrenal medulla Neurotransmitter released by postganglionic neurons: norepinephrine Promotes emptying of bladder Inhibits emptying of bladder Promotes erection of genitalia Sacral Promotes ejaculation and vaginal contractions Synapse
LE 48-22 Parasympathetic division Sympathetic division Action on target organs: Action on target organs: Constricts pupil of eye Dilates pupil of eye Location of preganglionic neurons: brainstem and sacral segments of spinal cord Location of preganglionic neurons: thoracic and lumbar segments of spinal cord Stimulates salivary gland secretion Inhibits salivary gland secretion Sympathetic ganglia Constricts bronchi in lungs Relaxes bronchi in lungs Cervical Neurotransmitter released by preganglionic neurons: acetylcholine Neurotransmitter released by preganglionic neurons: acetylcholine Slows heart Accelerates heart Inhibits activity of stomach and intestines Location of postganglionic neurons: in ganglia close to or within target organs Stimulates activity of stomach and intestines Thoracic Location of postganglionic neurons: some in ganglia close to target organs; others in a chain of ganglia near spinal cord Inhibits activity of pancreas Stimulates activity of pancreas Stimulates glucose release from liver; inhibits gallbladder Stimulates gallbladder Lumbar Neurotransmitter released by postganglionic neurons: acetylcholine Stimulates adrenal medulla Neurotransmitter released by postganglionic neurons: norepinephrine Promotes emptying of bladder Inhibits emptying of bladder Promotes erection of genitalia Sacral Promotes ejaculation and vaginal contractions Synapse