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Nervous Systems

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Title: Nervous Systems


1
Nervous Systems
2
Nervous Systems
3
Evolution of the Nervous System
  • Nerve Net
  • Cnidarian, Ctenophora
  • Nerve Ring with radial nerves
  • Echinodermata
  • Bilateral Nervous Systems
  • Cephalization (ganglia or brain)
  • Nerve cord

4
Evolution of the Nervous System
  • Bilateral Nervous Systems
  • Ganglia and two or more longitudinal nerve cords
  • platyhelminthes, some mollusca
  • Ganglia (brain) and ventral nerve cord
  • annelida, arthropoda, some mollusca
  • Brain and dorsal nerve cord
  • chordata

5
Overview of a Nervous System
6
Overview of a Nervous System
  • Sensory Input
  • conduction of signals from sensory receptors
  • PNS
  • Integration
  • environmental information is interpreted
  • CNS (brain and spinal cord)
  • Motor Output
  • conduction of signals to effector cells
  • PNS

7
Neurons
8
Neurons
  • Cell body
  • nucleus and organelles
  • Dendrites
  • short and branched
  • toward cell body
  • Axons
  • long and unbranched
  • away from cell body

9
Axons
  • Myelin Sheath - insulating layer
  • Node of Ranvier - gaps between Schwann Cells
  • Synaptic Terminals - neuron ending

10
Clusters of Neurons
  • Ganglion
  • Cluster of nerve cell bodies in the PNS
  • Nuclei
  • Cluster of cells in the brain

11
Supporting Cells
  • Glia (glue)
  • Astrocytes (structural support)
  • Creates tight junctions and forms the blood-brain
    barrier
  • Radial Glia
  • Form tracks for new neurons formed in the neural
    tube
  • Oligodendrocytes
  • Form myelin sheath in brain
  • Schwann Cells
  • Form myelin sheath in the PNS

12
Reflex
  • Sensory neuron to a motor neuron

13
Neural Signals
  • Membrane Potential
  • Sodium-Potassium Pump

14
Threshold Potential
15
Resting State
  • Both sodium and potassium activation gates are
    closed
  • Interior of cell is negative

16
Depolarization State
  • Sodium activation gates are opened on some
    channels
  • Interior of cell becomes more positive

17
Rising Phase of Action Potential
  • Most sodium activation gates are opened
  • Potassium activation gates are still closed

18
Falling Phase of Action Potential
  • Inactivation gates on sodium channels are closing
  • Activation gates on potassium channels are opened
  • interior of cell becomes more negative

19
Undershoot
  • Both gates to sodium channels are closed
  • Potassium channels are closing
  • Membrane returns to its resting state

20
Propagation of the Action Potential
  • Localized event
  • First action potentials depolarization sets off
    second action potential
  • Travels in one direction due to refractory period

21
Salatory Conduction
  • Action Potential jumps from node to node
  • Speeds up signal from 5 m/sec to 150 m/sec

22
Communication Between Synapses
  • Electrical Synapses
  • gap junctions allow for direct transfer of action
    potential (used during escape responses)
  • Chemical Synapses
  • uses neurotransmitters

23
Chemical Synapse
24
Chemical Synapses
  • Action potential triggers an influx of calcium
  • Synaptic vesicles fuse with presynaptic membrane
  • Neurotransmitter released into synaptic cleft
  • Neurotransmitters bind to receptors and open ion
    channels on postsynaptic membrane which sets off
    new action potential
  • Neurotransmitters are degraded by enzymes or
    removed by a synaptic terminal

25
Neurotransmitters
26
Postsynaptic Potentials
27
Postsynaptic Potentials
  • Subthreshold
  • doesnt reach threshold
  • Temporal Summation
  • two signals do not reach threshold level but
    occur close enough to set off action potential
  • Spatial Summation
  • two signals are set off at the same time setting
    off an action potential
  • Spatial Summation with an inhibitor
  • doesnt reach threshold

28
Vertebrate Nervous System
29
Central Nervous System
  • Ventricles (4)
  • Cerebrospinal fluid
  • White Matter
  • Made up of axons
  • Gray Matter
  • Made up of dendrites

30
Peripheral Nervous System
31
Peripheral Nervous System
  • Autonomic Nervous System regulates the internal
    environment (usually involuntary)
  • Somatic Nervous System regulates the external
    environment (usually voluntary)

32
Autonomic Nervous System
33
Autonomic Nervous System
  • Sympathetic Division
  • Flight or fight response
  • Parasympathetic Division
  • Rest or digest response

34
Brain
35
The Brainstem
  • The Medulla Oblongata and the Pons controls
    breathing, heart rate, digestion
  • The Cerebellum controls coordination of movement
    and balance

36
The Midbrain
  • The Midbrain receives, integrates, and projects
    sensory information to the forebrain

37
The Diencepholon
  • Forebrain
  • Epithalamus
  • Includes the pineal gland and the choroid plexus
  • Thalamus
  • conducts information to specific areas of
    cerebrum
  • Hypothalamus
  • produces hormones and regulates body temperature,
    hunger, thirst, sexual response, circadian
    rhythms

38
The Telencepholon
  • Cerebrum
  • with cortex and corpus callosum
  • higher thinking

39
Cerebrum
40
Cerebrum
41
Cerebrum
42
Limbic System
  • Regulates emotions
  • Association with different situations is done
    mostly in the prefrontal lobe

43
Memory
  • Short Term
  • Done in the frontal lobe
  • Long Term
  • Frontal lobes interact with the hippocampus and
    the amygdala to consolidate

44
Sensory Receptors
  • Mechanoreceptors
  • Pain Receptors
  • Thermoreceptors
  • Chemoreceptors
  • Electromagnetic Receptors

45
Sensory Receptors
  • Mechanoreceptors
  • Pain Receptors
  • Thermoreceptors

46
Sensory Receptors
  • Chemoreceptors

47
Sensory Receptors
  • Electromagnetic receptors

48
Evolution of the Eye
  • Complex eyes have developed many times

49
Evolution of the Eye
  • All light-sensitive organs rely on photoreceptor
    systems employing a family of proteins called
    opsins. Further, the genetic toolkit for
    positioning eyes is common to all animals the
    PAX6 gene controls where the eye develops in
    organisms ranging from mice to humans to fruit
    flies

50
Photoreceptors
  • Eye cups (ocelli) - light detection
  • Genetic basis that started as a light detector
    600 mya
  • During the Cambrian explosion around 540 mya two
    types of eyes arose

51
Photoreceptors
  • Compound Eyes - made up of ommatidia that helps
    detect movement

52
Photoreceptors
  • Camera Type Eyes Evolved several times
  • Hagfish eye
  • Lamprey eye
  • Jawed vertebrate eyes

53
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54
Single Lens Eye
  • Sclera (white)
  • Cornea (clear)
  • Choroid (pigmented)
  • Iris (color of eye)
  • Retina (rods and cones)
  • Pupil
  • Fovea (focal point)
  • Blind spot

55
Photoreceptors
  • Scars of Evolution
  • 1. inside out retina that forces light to pass
    through the cell bodies and nerves before hitting
    the retina
  • 2. blood vessels across the retina that cause
    shadows
  • 3. nerve fibers that exit causing a blind spot

56
Focusing
  • Near vision
  • ciliary muscle contracted
  • lens becomes more spherical
  • Distance vision
  • ciliary muscle relaxed
  • lens becomes flatter

57
Visual Problems
  • Near-sightedness (myopia)
  • eyeball too long / focal point in front of fovea
  • Far-sightedness (hyperopia)
  • eyeball too short / focal point behind fovea
  • Astigmatism (blurred vision)
  • misshapen lens or cornea

58
Hearing and Equilibrium
59
Hearing Organ
  • Outer Ear
  • pinna and the auditory canal
  • tympanic membrane
  • Middle Ear
  • malleus, incus and stapes
  • oval window
  • Inner Ear
  • cochlea with the Organ of Corti
  • with a basilar membrane and hair cells
  • Eustachian Tube

60
Sound
  • Volume
  • amplitude of sound wave
  • vibrates fluid in ear and bend hair cells which
    generates more action potentials
  • Pitch
  • frequency of sound wave

61
Equilibrium
  • Utricle and Saccule
  • Semicircular Canals
  • used to detect body position and movement

62
Lateral Line System
  • Similar to inner ear
  • detects movement of current, moving objects

63
Statocysts
  • Equilibrium
  • contain statoliths

64
Sound Systems in Invertebrates
  • Body hairs that vibrate
  • mosquitoes
  • Tympanic Membranes
  • crickets

65
Chemoreception
  • Taste Buds
  • sweet (tip), salty (behind), sour (sides), bitter
    (back of tongue)

66
Chemoreception
  • Olfactory receptors cells
  • upper portion of nasal cavity

67
The Cost of Locomotion
68
The Cost of Locomotion
  • Locomotion must overcome two forces
  • gravity
  • friction
  • Swimming is more efficient than running
  • runner must overcome gravity
  • Larger animals travel more efficiently than
    smaller animals
  • Flight is the most costly (per minute)

69
Skeletal Structures
  • Hydrostatic Skeleton
  • (cnidaria, ctenophora, platyhelminthes, nematoda,
    annelida)
  • Exoskeletons
  • mollusca, arthropoda
  • Endoskeletons
  • chordata

70
Cooperation of Muscles and Skeletons
  • Muscles always contract
  • Muscles attached in antagonistic pairs

71
Skeletal Muscles
  • Muscles are made up of muscle fibers
  • Fibers are made up of myofibrils
  • Myofibrils are made up of myofilaments
  • thin filaments (actin)
  • thick filaments (myosin)

72
Sliding Filament Model
  • Sacromeres (basic functioning unit)
  • Z lines (border of sacromeres)
  • H zone (center of sacromere)
  • I band (only thin filaments)
  • A band (length of thick filaments)

73
Sliding Filament Model
  • During contraction, thin and thick filaments
    slide past each other
  • I band and H zone decreases in size
  • Caused by myosin head creating cross bridge with
    actin fiber and then moves by using ATP

74
Muscle Control
  • Tropomyosin blocks myosin binding sites
  • Calcium ions allow cross bridges to form

75
Muscle Fibers
  • Fast Muscle Fibers
  • rapid, powerful contractions
  • flight muscle
  • Slow Muscle Fibers
  • sustain, long contractions
  • adductor muscles

76
Invertebrate Muscles
  • Flight muscles in insects are capable of
    independent contractions
  • wings beat faster than action potentials
  • Clam muscles contain paramyosin that allows them
    to remain contracted with little energy
  • Nematodes only have longitudinal muscle that
    gives them their characteristic movements
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