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The Nervous system

Learn about the three classes of neurons, anatomy of a neuron, how signals are transmitted between neurons, and the divisions of the nervous system. Discover the functions of the central nervous system, sensory and motor divisions, and the role of the autonomic nervous system. Explore the parts of the brain, memory formation, and disorders of the nervous system. Understand how sensory reception works and the different types of sensory receptors and pathways.

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The Nervous system

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  1. The Nervous system The nerve cell is the basic unit of communication in the vertebrate nervous system

  2. Three Classes of neurons • The Neural circuit consists of • Sensory neurons • receptor for stimulus • Interneuron • integrate signals • Motor neuron • transfer signal to effector (muscle)

  3. Anatomy of a Neuron • Cell body: functional portion • Dendrites: short extensions that receive signals • Axon: long extension that transmits impulses

  4. How does a neuron hold and move info? • A neuron at rest has a voltage difference across the plasma membrane called a resting voltage potential • An action potential is when this charge across the membrane is briefly switched • The action potential moves down the membrane at a rapid pace. • Ap can move faster over mylenated portions is called saltatory conduction

  5. How does a signal move from one neuron to another? • A synaptic cleft divides 2 neurons • The AP will not move across the synaptic cleft • Neuro transmitters are released by the signal cell to the receiver cell • Move by diffusion

  6. Types of chemical synapse • Acetylcholine: neuromuscular junctions, glands, brain and spinal cord • Norepinepherine: affects brain regions concerned with emotions, dreaming

  7. Signals between the brain and spinal cord move to the body regions by nerves Sensory nerves move a signal towards the brain and spinal cord Motor neurons move a signal from the brain or spinal cord to the body Paths of information flow

  8. Central nervous system CNS Is the brain and spinal cord Peripheral nervous system PNS all nerves that carry signals to and from the CNS Divisions of the nervous System

  9. Parts of the PNS • Sensory Division carries info to the brain and spinal cord. • Motor Division carries info from the brain to the bodies effectors (things that do the work)

  10. Somatic nerves relay commands to and from skeletal muscle Voluntary control Autonomic nerves send signals to and from smooth muscles Involuntary control Sympathetic Parasympathetic The Motor division of the PNS has 2 divisions

  11. Parasympathetic slow down the body activity when the body is not under stress Rest and digest Sympathetic increase overall body activity during times of stress, excitement or danger fight or flight response hormone epinephrine The autonomic divisions

  12. Sympathetic and Parasympathetic • Are Antagonistic • Work towards the automatic, subconscious maintenance of homeostasis.

  13. Spinal cord 31 pair of spinal nerves Grey matter White matter Controls some reflex actions like bladder emptying Brain parts Hindbrain medulla oblongata cerebellum pons Midbrain Forebrain cerebrum thalamus hypothalamus Components of the CNS

  14. Other parts of the CNS • The two cerebral hemispheres communicate through the corpus collosum • left verbal skills • right nonverbal skills such as music math, abstract • Brain cavities and Canals • cerebrospinal fluid surrounds and fills in cavities in the brain • Blood Brain barrier- controls what moves into the brain. Will prevent infections.

  15. Our state of consciousness • The CNS governs sleeping, dozing, daydreaming and full alertness • neurons of the reticular activating system control the changing levels of consciousness by releasing serotonin.

  16. Limbic system • Involved in both memory and emotion. • Is involved with behavior. • Odors pass through this system and may influence or behavior and emotions.

  17. Association is the linkage of information to structural and chemical changes short term- few bits lasts a couple of hours Long term- permanent and limitless The most important info goes rapidly into long term storage memory is stored in a form resistant to degradation Possibly caused by changes in synapses. Memory

  18. Tips on studying • Concentrate on what you study. • Minimize interference. • Study takes time. • Break material into smaller portions. • Rephrase materials in your own words. • Test yourself to see what you know.

  19. Disorders of the nervous system • Trauma • Infections • Transmission and synaptic defects. • Abnormal growth

  20. Sensory Reception If a tree falls in the woods with no one to listen does it make a sound?

  21. Receptors • Are the actual structures that respond to our environment. • Each receptor will respond to a different signal. • Essentially translators, they translate an energy into one that can be perceived by the brain.

  22. Sensory systems consist of • Each system has 3 parts • 1) sensory receptors. • 2) pathway to the brain. • 3) region of the brain that recognizes this section.

  23. Chemoreceptors Mechanoreceptors Thermoreceptors Nociceptors Photoreceptors olfaction and taste touch, stretch, hearing, equilibrium radiant energy, infared pain receptors light Types of sensory Receptors

  24. Sensory Pathways • If a receptor is stimulated enough it results in an action potential. • The action potential reaches the brain. • The stronger the stimulus the greater number of action potentials reach the brain. • Sensory adaptation is when the action potentials are reduced by a constant stimulus. • Certain receptors will not adapt.

  25. Touch & Pressure Temperature Pain Muscle sense Mechanoreceptors that respond to changes or constant pressure Increase in temperature causes and increase in AP Respond to intense stimulus on other receptors, cannot be ignored Mechanoreceptors give measurement as to the location of all the muscles and bones in a given moment. Somatic sensations

  26. Limb position, length and tension • How do we know where we are at?

  27. Referred pain

  28. Gustation: Taste Receptors located on tongue, roof of mouth, throat and palate Four tastes sweet sour bitter salty Olfaction: smell detect chemicals olfactory bulbs in brain interpret smell smell is often combined with emotion Taste and Smell

  29. Taste • Taste Bud 25 cells • Taste hairs project into mouth • Hairs contain receptors • Categories • Sweet • Sour • Salty • bitter

  30. Hearing • Acoustical receptors detect vibrations • The ear • In the organ of corti loudness is determined by The total number of cells that are stimulated • Pitch depends on frequency of vibration

  31. Vestibular apparatus Closed system of fluid filled sacs Contain otoliths that detect changes in orientation as well as acceleration Overstimulation of the hair cells of the vestibular apparatus results in motion sickness Balance

  32. Vestibular apparatus

  33. The Eye

  34. Outer sclera (white) (is all the way around) Cornea (clear) Pupil (opening to the back) Lens (transparent) Retina (back side has photoreceptors and support material) Fovea has highest concentration of photoreceptors. Structure of the eye

  35. Regulating light amount • The iris adjusts to amount of light entering the eye. • The lens goes through accommodation to adjust lens curvature (as we age the lens cannot buldge enough to focus on a close object)

  36. Light must reach the sensors by going through neurons. • Outermost layer is pigmented to absorb light not absorbed by the sensors • Photoreceptors are in middle layer • Translucent neurons and ganglions are on top of the photoreceptors.

  37. Production of Action Potentials by Rods and Cones • Within these cells flattened disks contain photopigment • When this protein absorbs light it changes conformation, if enough are activated they cause an action potential. • Rods contain rhodopsin and are most sensitive to dim light • Cones contain different pigments

  38. Rods and Cones • Bright light tends to use more cones, 300x more sensitive • Dim light uses Rods and Rhodopsin, it is broken apart by light and must be remade (hence the 5-10 minute wait to see in darker areas)

  39. Photoreceptors are in the retina When rods or cones are stimulated they send a signal to the brains visual cortex. In the brain the final interpretation makes sense of sight Signaling to visual perception

  40. Problems with the Eyes • Retinal detachment: retina separates form choroid • Cataracts: lens becomes opaque • Color blindness: Inability to distinguish colors, is a genetic disease, lacks specific types of cones

  41. The Endocrine system The oldest method of control is using a signal molecule that moves from one part of the body to the other

  42. The Endocrine System Regulates • Salt and water balance • Blood pressure • Stress responses • Digestion • Cellular metabolism • Production of RBC’s • Growth and development

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