Physiology ch 9 lecture notes

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Physiology ch 9 lecture notes

  1. 1. CHAPTER 9: NERVOUS SYSTEM
  2. 2. 2 Main Divisions CNS - Central Nervous System  brain and spinal cord PNS - Peripheral Nervous System  all other nerves
  3. 3. Nerve Tissue 1. Neurons (nerve cell) - structural and functional cell of the nervous system - reacts to physical and chemical changes - neurons do not touch other neurons
  4. 4. cell body dendrites nucleus axon Schwann cell myelin Node of Ranvier
  5. 5. 2. Neuroglial cells 4 Types a) Astrocyte - connects neurons to blood vessels - provides support - remove cellular debris
  6. 6. b) Oligodendrocyte - arranged along nerve fibers - produces myelin c) Microglia - provide support - phagocytize bacteria d) Ependyma - covers part of the brain
  7. 7. astrocyte oligodendrocyte microglial cell ependymal cell
  8. 8. Types of Neurons and Nerves Classification 1. Multipolar neuron - only one axon, many dendrites - found only in brain and spinal cord dendrites axon
  9. 9. 2. Bipolar neuron - one dendrite, one axon - found in the eyes, nose, and ears dendrite axon 3. Unipolar neuron - 1 nerve fiber and then branches off axon dendrite - mass of these make up a ganglion - found outside the brain & spinal cord
  10. 10. Types of Nerves  A grouping of neurons 1. Sensory nerves - send impulses to the brain 2. Motor nerves - send impulses to muscles 3. Mixed nerves - contains both sensory & motor neurons
  11. 11. The Nerve Impulse  also called an Action Potential 1. Nerve cell gets excited 2. For a nerve impulse to get started, it must reach a threshold potential  minimal amt. of stimulus needed to start an impulse  summation - adding up of threshold stimuli
  12. 12. 3. Cell membrane permeability must be changed for a nerve impulse to travel down a neuron a) A cell is normally polarized - when a neuron is at rest - called it resting potential
  13. 13. b) A portion of the neuron becomes depolarized - Na + moves into the cell
  14. 14. c) Cell repolarization - K + moves out of the cell Nerve impulse - a nerve impulse is an all-or-none response - impulse will trigger or it won’t
  15. 15. Synapse - junction between 2 neurons - gap is called a synaptic cleft Synaptic Transmission - end of axon is synaptic knob which contains synaptic vesicles - these synaptic vesicles contain neurotransmitters
  16. 16. synaptic vesicle vesicle releasing neurotransmitter synaptic cleft synaptic knob Synaptic transmission
  17. 17. - After being released, neurotransmitters must be broken down to prevent continued stimulation - they are destroyed by: - cholinesterase - breaks down ACH - monoamine oxidase - breaks down monoamines
  18. 18. Types of Neurotransmitters 1. ACH - acetylcholine - used in skeletal muscle contractions 2. Monoamines - Norepinephrine – creates sense of “ feeling good”, too little - depression - Dopamine – creates a sense of “feeling good” – low amounts associated with Parkinson’s Disease - Serotonin – leads to sleepiness - Histamine – promotes alertness
  19. 19. 3. Neuropeptides - Substance P – pain perception - Endorphins – reduce pain
  20. 20. Nerve Pathways  the routes nerve impulses travel 1. Reflex arc sensory nerve impulse spinal cord interneuron motor nerve
  21. 21. Reflexes - automatic, unconscious responses to changes occurring within or outside the body - ex. knee jerk reflex - ex. withdrawl reflex
  22. 22. Coverings of the Central Nervous System - brain and spinal cord are protected by membranes called meninges 3 Layers a) dura mater - tough - attaches to the cranial cavity scalp skull dura mater
  23. 23. b) Arachnoid mater - subarachnoid space below contains cerebrospinal fluid arachnoid mater fluid c) pia mater - contains nerves and blood vessels pia mater
  24. 24. Spinal Cord Structure - 31 segments - each with a pair of spinal nerves - spinal nerve spinal nerve -
  25. 25. - central canal - central canal - contains CSF gray matter - - gray matter - mostly interneurons - white matter - white matter – comprised of the ascending and descending tracts
  26. 26. Functions - provides a 2-way communication system between brain and other body parts Ascending Tracts - carry sensory impulses to the brain Descending Tracts - carry motor impulses to muscle and glands
  27. 27. The Brain 3 Major Parts cerebrum cerebellum brain stem
  28. 29. Structure of the Cerebrum - 2 cerebral hemispheres - connected together by the corpus callosum - ridges are called convolutions or gyri - sulcus - shallow groove - fissure - deep groove
  29. 31. Lobes of the Cerebrum Insula - deep in brain Frontal Parietal Occipital Temporal
  30. 32. Functions of the Cerebrum Cerebral cortex - thin layer of gray matter that covers the cerebrum Areas of the Cortex 1. motor areas 2. sensory areas 3. association areas - memory, reasoning, judgment, & emotion - most people have a dominant hemisphere - left - more logical - right - more creative
  31. 33. The Diencephalon Thalamus - receives sensory impulses - sends them to appropriate areas of the brain Hypothalamus - important in homeostasis - secretes hormones
  32. 34. Limbic system - emotional experience or response Pineal gland - endocrine gland - involved in our daily biological clock
  33. 35. The Brain Stem  connects cerebrum to spinal cord 3 Parts 1. Midbrain - reflex center for the eyes and ears 2. Pons - place where the cranial nerves originate
  34. 36. 3. Medulla Oblongata - control center of various activities a. cardiac center b. vasomotor center c. respiratory center - contains the reticular formation - involved with activating the brain and waking up
  35. 37. The Cerebellum - consists of 2 hemispheres - divided by the vermis - cerebellar cortex is the outermost layer Functions 1. maintaining balance 2. coordinating motion
  36. 38. Peripheral Nervous System  everything but the brain & spinal cord Cranial Nerves - 12 pairs - originates in brain Spinal Nerves - 31 pairs - provide 2-way communication between spinal cord and parts of the body
  37. 39. The Autonomic Nervous System - part of the PNS - controls unconscious actions - heart beat - involuntary muscles - maintains homeostasis

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