External stimuli final presentation by zahid bhatti
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External stimuli final presentation by zahid bhatti Presentation Transcript

  • 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 meissner’s 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:  Lippincott’s 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