1. TOPIC NERVE IMPULSES & EXTERNAL STIMULI VISUAL,SOUND & ELECTRICAL SENSORY ORGANS Subject PHYSIOLOGY By: ZAHID BHATTI PARIVISH JOKHIO SAJJAD ALI Course # 703 Faculty: Madam Zarina Shafi

2. 3 Ground Rules Time allocation: One hour. 50 minutes for presentation and 10 minutes are for Q/A. Questioning and answering are asked at the end of presentation. If you feel any problem or urgency you can leave the class without any disturbance. Turn off your mobile phone. 3. OBJECTIVES At the end of this presentation learner will be able to: Define Neuron and function of the parts of a neuron. Describe the term Nerve and Nerve Impulses. Explain how a Nerve Impulse passes a long a Neuron(axon). Discuss the Resting potential and role of Action potential in the transmission of a nerve impulse. Discuss the External stimuli & visual, sound and electrical sensory organs. 4. NEURON Nerve cell and its fibers are collectively called as Neuron Neurons are the basic building blocks of the nervous system. These specialized cells are responsible for receiving & transmitting information 5. FUNCTION OF THE PARTS OF A NEURON Dendrite receives information /message/ impulse from sensory receptors, then passed down to the cell body and to the axon. 6. FUNCTION OF THE PARTS OF A NEURON Axon is the long hair like fiber ,that extends from cell body to the terminal endings. 7. FUNCTION OF THE PARTS OF A NEURON Axon terminal, or Nerve endings are responsible for sending signals to other neurons. At the end of terminal button there is a gap known as synapse. 8. NEURON Axon terminal release a chemical called Neurotransmitter, (Acetylcholine) used to carry the signal across the synapse to other neuron. 9. NERVE Elongated cord like bundle of fibers made up of neurons, forming a network that transmits messages in the form of impulses between the brain or spinal cord & the other parts of the body. 10. NERVE IMPULSE Nerve impulse is a wave of electrical activity that passes from one end of a neuron to the other ,due to ions moving. 11. Explain How a Nerve Impulse Passes along a neuron(axon) The two important ions in a nerve cell (neuron) are sodium ions and Potassium ions. The concentration of Sodium ions is relatively greater outside, while the concentration of potassium is relatively greater inside a cell. 12. Explain How a Nerve Impulse Passes along a neuron(axon) When neuron is at rest a charge difference is maintained between the inside and out side of the cell . The over all result is that the exterior of the cell has a net positive charge and the interior has a net negative charge. 13. RESTING POTENTIAL When neuron is in active it is said to be at its resting potential. Sodium ions normally stay outside. It remains this way until a stimulus comes along. The difference in charge B/w the interior & exterior cell is called resting potential. 14. ROLE OF ACTION POTENTAL IN THE TRANSSMISSION OF A NERVE IMPULSE when a stimulus/or impulse disturbs the plasma membrane on a dendrite, causing sodium ion channel to open. Sodium ions flow into the axon, depolarizing the membrane. Localised electric currents are generated in the membrane 15. ROLE OF ACTION POTENTAL IN THE TRANSSMISSION OF A NERVE IMPULSE 16. ROLE OF ACTION POTENTAL IN THE TRANSSMISSION OF A NERVE IMPULSE The sodium ion channel close and potassium ion channel open. Potassium ions leave the axon,repolarizing the membrane. The exiting K+ ions causes the potential to decline and the membrane potential goes back to the original level 17. ROLE OF ACTION POTENTAL IN THE TRANSSMISSION OF A NERVE IMPULSE In this way local electric currents cause the nerve impulse to move along the axon. At the site of first action potential, potassium ions diffuse back into the axon, restoring the resting potential. This is called the refractory period. 18. ROLE OF ACTION POTENTAL IN THE TRANSSMISSION OF A NERVE IMPULSE 19. DIAGRAM SHOWING RESTING AND ACTION POTENTIAL 20. STIMULUS Any action, condition, that makes an organism to react or Any internal or external effect on the body is called stimulus An action taken as a result of a stimulus is called response E.g:- A dog feels hot so it goes to lay in the shade. 21. STIMULUS A stimulus may be tactile :skin (touch),pain,hot & cold. Visual :(light) & colour. Auditory (hearing)sound Olfactory:(smell) chemicals in the air. Gustatory :tongue (taste).chemicals in food & drink 22. HOW TO SENSE (or detect) A STIMULUS RECEPTORS: Information about your surrounding is collected by receptor cells. Living objects have sense organs that detects forms of energy . Human senses include the senses of touch, sight. smell, hearing, and taste. 23. EXTERNAL STIMULI A stimulus that comes from outside an organism. or Any external input which leads to sensation or reaction is called external stimuli Sensory receptors can detect changes or receive information from outside the body, through sensory receptors, and convert these stimulus into impulses. 24. HOW DO WE RESPOND TO STIMULI An action taken as a result of a stimulus is called response The response to a stimulus can be positive, negative, or ignored as not important. POSITVE: A positive response is when organism is attracted to. E.g:- A person laughs after hearing a funny joke 25. HOW DO WE RESPOND TO STIMULI NEGATIVE: When you want to avoid stimulus. E.g:- You make a face after smelling a bad odor 26. HOW DO WE RESPOND TO STIMULI IGNORED When stimulus is not important to you E.g:- You pay no attention when someone is shouting in front of you while listening to the music. 27. EYE (VISUAL ORGAN) Vision provides opportunity for the brain to perceive and respond to changes occurring around the body. 28. EYE (VISUAL ORGAN) Components: Cornea: where light enters the eye Lens: focuses the light rays on the retina Iris: colored ring of muscle, constricts or dilates via amount of light Pupil: regulates amount of light 29. EYE (VISUAL ORGAN) Information, or stimuli, in the form of light enters the retina Where Photoreceptor cells rods & cones convert light into Neural Impulses The impulse go to the brain stem via optic nerve Cerebral cortex /occipital lobe perceive the light & respond. 30. EAR (SOUND ORGAN) The ear is responsible for hearing, it consist of three regions 1)External Ear 2)Middle Ear 3)Inner Ear 31. EAR (SOUND ORGAN) TRANSMISSION OF SOUNDS THROUGH THE EAR: External Ear: Mostly through Air (external acoustic Meatus) Middle Ear: Through Solid medium- bone(ossicles) Inner Ear: Through fluid medium- endolymph(cochlea) 32. EAR (SOUND ORGAN) In inner Ear, the basilar membrane of cochlea contains the corti-receptor that translate/covert the vibrations to electric impulses, the impulses go to the brain stem via acoustic nerve (viii). Cerebral cortex- interprets the meaning of the sound and begins the appropriate response. 33. TONGUE(SENSORY ORGAN) Taste records flavoring of food and other materials that pass across the tongue and through the mouth. Gustatory cells are located on the surface of the tongue. 34. TONGUE(SENSORY ORGAN) 35Figure 4.49 The tongue and taste Receptor cells found in taste buds. Sweet and bitter, receptors are called gustducins Pathway: taste buds > neural impulse > thalamus > cortex Four primary tastes: sweet, sour, bitter, and salty 35. NOSE(SENSORY ORGAN) Smell allows the body to recognize chemical molecules in the air through inhalation. Olfactory receptors = olfactory cilia Pathway: Olfactory cilia -> neural impulse -> olfactory nerve -> (brain) 36. SKIN ( SENSORY ORGAN) Pain & touch is recorded by sensory receptors on the skin. Pain receptors are known as nociceptors. Touch receptors are known as meissners corpuscle. 37. SKIN ( SENSORY ORGAN) Pathway: Sensory receptors > the spinal column > brainstem > thalamus > (parietal lobe) if it is decided that a response must be made, a signal is sent back down to a muscle, which acts appropriately according to the stimulus. 38. REFERENCE: Lippincotts review series medical surgical nursing fourth edition Ray A. Hargrove-Huttle RN, phD. Anatomy & physiology for Nurses (16th edition) by Evelyn C.Pearce. Lynn S. Bickley, Bates (8th Edition): Guide to Physical Examination and History Taking. Anne Waugh. Allison Grant (10th Edition): Anatomy & Physiology in Health & Illness. www.ifeet.org/files/eppch_13ed.ppt