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Nervous System

Nervous System. Chapter 7. The Nervous system is the master controlling and communicating system of the body. 3 step process Sensory -uses sensory receptors to monitor changes inside and outside of the body.

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Nervous System

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  1. Nervous System Chapter 7

  2. The Nervous system is the master controlling and communicating system of the body. • 3 step process • Sensory-uses sensory receptors to monitor changes inside and outside of the body. • Integration-processes and interprets the information and makes decision about what to do with the information (integration) • Motor-activation of muscles or glands in response to the stimuli

  3. NERVOUS SYSTEM

  4. All nervous system organs are separated into two classifications by structure. • Central Nervous System • Peripheral Nervous System Organization of the Nervous System

  5. Made up of the brain and spinal cord • Main purpose is to interpret the incoming sensory information and relay tissue instructions based on past experiences or conditions. Central Nervous System(CNS)

  6. Anything in the nervous system outside of the brain and the spinal cord. • Consists of mainly nerves • 2 types • Spinal Nerves- Carry impulses to and from the spinal cord. • Cranial Nerves- Carry impulses to and from the brain. Peripheral Nervous System(PNS)

  7. The functional classification is only concerned with the peripheral nervous system • Sensory/afferent- send information from the sensory receptors to the CNS. • Motor/efferent-carry impulses from the CNS to the muscles and glands and initiate a response. Functional Classifications

  8. Somatic nervous system • allows conscious, voluntary movement of skeletal muscles. • Not all muscular activity is voluntary • Skeletal muscle reflexes-stretch reflex • When a muscle spindle is stretched, it sends a message to the brain telling the brain to contract the muscle to prevent tearing. • Patellar-tendon reflex Motor Divisions

  9. Stretch Reflex

  10. Autonomic Nervous System • Regulates events that are automatic or involuntary • Activity of cardiac muscles and smooth muscle • Separated into two parts • Sympathetic-fight or flight, produce reactions under stress • Parasympathetic-rest and digest, all other autonomic functions, blood vessel dilation, pupil dilation. Motor Divisions

  11. Astrocytes- • Abundant, star-shaped cells • Brace neurons to their nutrient supply • Form barrier between capillaries and neurons • Control the chemical environment of the brain by picking up excess ions and recapturing released neurotransmitters. • Microglia- • Spiderlike phagocytes that dispose of debris (dead cells) • Ependymal • Line the cavities of the brain and spinal cord. • Their cilia help circulate CSF that fills those cavities • CSF forms a protective cushion for the CNS Nervous Tissues

  12. Oligodendrocytes- • Produce a myelin sheath around nerve fibers in the CNS • Insulation/protection for nerves

  13. Satellite cells • Protect neuron cell bodies by cushioning cells • Schwann cells • Form myelin sheath in the peripheral nervous system Nervous Tissue: Support Cells

  14. Structure of a Motor Neuron

  15. Neurons = nerve cells • Cells specialized to transmit messages • Major regions of neurons • Cell body – nucleus and metabolic center of the cell • Processes – fibers that extend from the cell body Neuron Anatomy

  16. Body of the Cell • Metabolic center of the neuron • Nissl substance – specialized rough endoplasmic reticulum • Neurofibrils – intermediate cytoskeleton that maintains cell shape Neuron Anatomy

  17. Extensions outside the cell body • Dendrites -carry messages toward the cell body • Axons –carry messages away from the cell body to another neuron Neuron Anatomy

  18. Axons transmit their information at their terminal ends. • All axons branch out at their end forming thousands of axonal terminals. • Once the impulse reaches the axonal terminal it stimulates the release of neurotransmitters into the extracellular space. Axons and Nerve Impulses

  19. In Between each axonal terminal is a small gap called a synapse. • Neurons never touch other neurons. Synapse

  20. Most long nerve fibers are covered with a fatty material called myelin. • It protects and insulates the fibers and increases the transmission rate. • Axons outside of the CNS are insulated (myelinated) by Schwann cells. • Wrap themselves around axons for insulation. • When it is wrapped around the axon, the myelin sheath encloses the axon. Neurons

  21. The neurilemma is in between the myelin sheath and the Schwann cells. • The Myelin sheath is formed by many different Schwann cells, this leaves gaps of uncovered surface area that are called Nodes of Ranvier. Neurons

  22. Myelin sheaths around the fibers are gradually destroyed. • Once destroyed they harden and become “scleroses” • This decreases the persons ability to control their muscles and their mobility decreases. Multiple sclerosis

  23. Clusters of neuron cell bodies and collections of nerve fibers are named nuclei when in the CNS. • They are well protected in the body within the skull or the spinal column. • These cells do not go through cell division after birth. If a cell dies, it is not replaced. Thus the need for the bony protective coverings. Central Nervous System

  24. Ganglia- small collection of cell bodies in the CNS. • Tracts- bundles of nerves running through • White matter-dense collections of myelinated tracts (fibers) • Gray matter-unmyelinated fibers and cell bodies CNS anatomy

  25. Sensory Neurons • Afferent-go toward the brain/spinal cord for processing • Transmit information about outside stimuli to the CNS • Cutaneous receptors-skin • Proprioceptors- muscle/tendon • Nociceptors- pain impulses CNS

  26. Detect the amount of stretch or tension in skeletal muscles, tendons or joints. • Information is sent to the brain so that it can make adjustments for any changes in posture/balance. Proprioceptors

  27. Motor Neurons- • Efferent, carry impulses from the CNS to the muscles/glands for action. • Relay the action message to the muscles • Association Neurons- • Also known as interneurons. • They connect the motor and sensory neurons in neural pathways. CNS

  28. Naked Nerve Endings- pain and temperature • Messner’s Corpuscles- touch receptors • Pacinian Corpuscles-Deep Pressure • Golgi Tendon Organs (GTOs)-proprioception (contraction) • Muscle Spindle-proprioception (stretch) Sensory Receptors

  29. 2 major functions • Irritability- ability to respond to a stimuli and convert it into a nerve impulse • Conductivity-ability to transmit the impulse to other neurons, muscles or glands. Nerve Impulses-Phyisology

  30. When at rest, the plasma membrane is polarized, meaning there are fewer positive ions sitting on the inner face of the membrane than on the outside. • The major positive ions on the inside of the cell are potassium (K+), and the positive ions on the outside, are sodium (Na+) • If the inside is more negative than the outside, the neuron remains inactive. Physiology

  31. Many types of stimuli are used to excite the neurons, to activate and create an impulse. • Light excites eye receptors • Sound excited some ear receptors • Pressure for cutaneous receptors, etc. Physiology

  32. Regardless of the stimuli, the result is all the same, permeability of the cell membrane changes for a brief period. • Once the neuron is activated, the sodium gates of the plasma membrane open and allow the sodium (Na+) into the cell. • Law of diffusion- higher concentration of Na+ outside the membrane • Once inside the polarity of the inside of the cell changes, this process is called depolarization. Physiology-depolarization

  33. If the stimulus is strong enough, and the rush of sodium is great enough, the neuron is activated through depolarization. • Once depolarized the neuron will transmit the nerve impulse (action potential). • **This process is all or nothing**. The impulse will either be sent all the way through the neuron, or not sent at all. Depolarization cont.

  34. Almost immediately after the Na+ ions rush in, the membrane permeability changes • It returns to being impermeable to Na+, but permeable to K+, just as before. • Now the K+ ions are free to float back out into the tissue fluid. This happens rapidly, the quick outflow of these ions restores the electrical conditions of the cell. Returning to its resting (polarized) state.This process is called repolarization Repolarization

  35. Action potential

  36. Once an impulse is sent through the neuron and it reaches the axonal terminal, tiny vesicles containing the neurotransmitter chemical fuse with the axonal membrane, releasing the chemical transmitters. • These chemicals travel across the synapse and bind to the next neuron. • This will more often than not restart the action potential in that next neuron. Conductivity of Neurons

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