peripheral system of nervous system ..pdf
- 1. The 9th lecture In Anatomy and Physiology For the 1st Class By Dr. Ala’a Hassan Mirza Hussain
- 2. Nervous System (Part III) The Peripheral Nervous System (PNS)
- 3. Peripheral Nervous System (PNS) • All neuronal structures outside the central nervous system (the brain and the spinal cord) is called PNS. • The main function of the PNS is to connect the CNS to the limbs and organs, by receiving data (such as sight or sounds) and sending it to the CNS for processing. The CNS in response to this data sends commends to respond to the input.
- 5. The stimulus conducts to the spinal cords by sensory neuron. In the spinal cord the stimulus is processed and transmitted to the skeletal muscle.
- 6. • The afferent division of the peripheral nerve fiber delivers information to the CNS and the efferent division carries the motor commands to the organs systems and muscles of the body. • The PNS not protected by bone of spine and skull or by blood brain barrier.
- 7. • PNS consists of the; 1. Sensory Receptors. 2. Peripheral nerve fibers. 3. Ganglia. 4. Effector organ (skeletal muscle, gland, smooth muscle, cardiac muscle).
- 8. Sensory Receptors • These are specialized receptors. Their function is to respond to stimuli (changes in their environment). • Examples on sensory receptors are; 1. Mechanoreceptors – respond to touch, pressure, itch ….ect. 2. Thermoreceptors – sensitive to changes into temperature. 3. Photoreceptors – respond to light. 4. chemoreceptors – respond to changes in blood chemistry, smell.
- 9. Nerve • A nerve is a cord composed of numerous nerve fibers (axons) bound together by connective tissue. • Most nerves are mixtures of afferent and efferent fibers. • Pure sensory (afferent) and pure motor (efferent) nerves are rare. • Peripheral nerves classified as cranial or spinal nerves. .
- 10. Nerve fiber
- 11. Nerve fiber
- 12. Ganglia • Synapse between nerve cells outside the CNS is called ganglion
- 13. Synapse between two neurons
- 14. Parts of PNS Peripheral Nervous System (PNS) Somatic Nervous System (SNS) Autonomic Nervous System (ANS) Sympathetic Nervous System Parasympathetic Nervous System
- 15. Somatic Nervous System (SNS) • Mediate bodily movement. • The somatic system is under conscious control with signal that originate in the cortex. • Innervate skeletal muscles. • Also called voluntary nervous system, the somatic system includes many involuntary functions such as sensation and reflexes. • Motor somatic neurons have No intermediate synapses outside of CNS (one neuron pathway i.e. there is No ganglia).
- 16. • Localized synapses are formed at specific neuromuscular junction. • Activation of motor somatic nerve leads to muscle contraction (i.e. has excitation effect only). • One type of neurotransmitter (acetylcholine “Ach”) releases at neuromuscular junction
- 17. Autonomic Nervous System (ANS) • Mediates control of the internal organs. • The autonomic system is largely involuntary, its control originates in the brainstem and hypothalamus. • Autonomic nervous system innervates the heart, smooth muscles, organs and glands. • The autonomic system makes one ganglion after leaving the CNS. The post ganglionic cell then makes contact with target organ (two neuron pathway). • Stimulation can cause either excitation or inhibition of the target tissue. • Use several types of neurotransmitter like norepinephrine (NE) and Ach.
- 18. Somatic nervous system Parasympathetic system
- 21. Differences between parts of PNS
- 22. Divisions of ANS 1. Sympathetic division 2. Parasympathetic division • Almost, all visceral organs are innervated by both divisions but they cause opposite effect.
- 23. ANS Anatomy • The origin of sympathetic fibers is thorocolumber region of the spinal cord while parasympathetic fibers are originated from brain and sacral spinal cord (craniosacral). • The length of pre-ganglionic sympathatic fibers are short, but post-ganglionic sympathetic fibers are long. • In contrast pre-ganglionic parasympathetic fibers are long and post ganglionic parasympathetic fibers are short. • The ganglia in sympathetic system are located close to the to the spinal cord, but in parasympathetic system the ganglia located near the viscera (organ).
- 24. ANS anatomy • The origin of sympathetic fibers is thoracolumber region of the spinal cord. While parasympathetic fibers are originated from brain and sacral spinal cord (craniosacral). • The preganglionic sympathetic fibers are short but post ganglionic sympathetic fibers are long. While preganglionic parasympathetic fibers are long and post ganglionic parasympathetic fibers are short. • The ganglia lie close to spinal cord in case of sympathetic system but in the parasympathetic system the ganglia lie near the target organ.
- 25. Neurotransmitters in the ANS • ANS preganglionic axons release Ach (cholinergic fibers). • All parasympathatic postganglionic axons release Ach. • Sympathetic postganglionic axons norepinephrine (adrenergic fibers). • Sympathetic nervous system has an excitatory effect while parasympathetic nervous system has an inhibitory
- 28. Role of sympathetic system • Mobilizes the body during activity; is the “fight or flight” system. • Promotes adjustments during exercise or when threatened: 1. Blood flow is shunted to the skeletal muscles and heart. 2. Bronchioles dilate. 3. Liver releases glucose.
- 29. Role of parasympathetic division • It promotes maintenance activities and conserve body energy. • Its activity is illustrated in a person who relaxes or at rest, and after meal; 1. Blood pressure, heart rate, and respiratory rates are low. 2. GIT activity is high. 3. Pupils are constricted and lenses are accommondated for close vision.