THE NERVOUS SYSTEM

1
THE NERVOUS SYSTEM
http//www.youtube.com/watch?vYRwPMICvbT4
2
I. Introduction

• Functions of N.S.
• Sensory input
• Integration
• Homeostasis
• Mental activity
• Control of skeletal muscles

3
I. Introduction

1. Divisions of the N.S.

Central N.S.
Peripheral N.S.
Efferent
Afferent
Brain
Spinal Cord
Autonomic
Somatic
Parasympathetic
Sympathetic
4
I. Introduction

1. Divisions of the N.S.

Central N.S.
Peripheral N.S.
Brain
Spinal Cord
Made of 12 cranial nerves 31 spinal nerves
No potential for regeneration

5
PNS

1. Afferent (sensory) division carries messages
   toward CNS.
2. Efferent (motor) division carries messages away
   from CNS toward muscles glands (somatic).

6
Sympathetic NS

• Fight or Flight
• Dilates pupils
• Reduces saliva, mucus, peristalsis, intestinal
  motility, urine secretion
• Increases heart rate, glycogen to glucose
  conversion

7
Parasympathetic NS

• Digest Rest
• Constricts pupils
• Reduces heart rate
• Increases mucus production, gastric juice
  production, digestion, urine production,
  intestinal tract motility, peristalsis

8
II. Histology of the N.S.
2 types of cells neurons support cells
(neuroglia)

• Neurons
• 1. Are excitable, irritable, conductive.
• nerve cells
• functional unit of n.s.
• Neurons are not nerves!
• Nerves are bundles of PNS fibers held together by
  several layers of connective tissue

9
A. Neurons

• 2. Structure.  a. Cell body b. Dendrites
• receive incoming signals towards cell body

10
A. Neurons

• 2. Structure  c. Axons
• transmit signals away from cell body

11
(No Transcript)
12
2. Structure

• c. Axons
• Myelin Sheath - membrane "insulation" around
  axons
• Nodes of Ranvier - gaps between myelin

13
2. Structure

• c. Axons
• Nissil bodies - rough endoplasmic reticulum...
  Lots of protein synthesis
• Synaptic vesicles - stores neurotransmitter at
  axon terminal

14
(No Transcript)
15
Structural Classification of Neurons
16
Regeneration

• A. Neurons do not reproduce themselves, but they
  can regenerate new parts sometimes.
• B. If a neuron is cut through a myelinated axon,
  the proximal portion may survive if the cell body
  is not damaged.
• C. The distal portion will die (degenerate).
  Macrophages move into the area and remove debris.
  
• D. Neuron cell body reorganizes its Nissl bodies
  to provide proteins necessary for axon growth.
• E. The Schwann cells form a regeneration tube
  that helps guide the axon to its proper
  destination.

17
Regeneration

• F. New fiber will eventually fill the myelin
  sheath and innervate the muscle. Growth occurs at
  3-5 mm/day. (1 mm 0.04 inch)
• G. In the CNS, this repair is unlikely because
  the neurons lack the neurilemma necessary to form
  the regeneration tube. Also, the astrocytes
  quickly fill the damaged area forming scar
  tissue. Most CNS injuries cause permanent damage.
  

18
Regeneration

• H. Crushing and bruising can also damage nerve
  fibers resulting in paralysis. Inflammation of
  the injury site damages more fibers. Early
  treatment with methyprednisolone reduces
  inflammation and decreases severity of injury. It
  must be given within 8 hours to be effective.
• http//www.youtube.com/watch?vkxVMog4PkYo

19
II. Histology of the N.S.

• Neuroglia nonexcitable help support neurons
• OF THE CNS
• Astrocytes - "nurse" cells nourish protect
  neurons form blood brain barrier
• Oligodendrocytes - form myelin in CNS

20
II. Histology of the N.S.

• Neuroglia nonexcitable help support neurons
• OF THE CNS
• Microglia - provide immune protection in CNS.
• Ependymal cells circulate cerebrospinal fluid

21
II. Histology of the N.S.

• Neuroglia OF THE PNS
• Schwann Cells - form myelin in peripheral nerves
• Satellite Cells surround and support neurons of
  the ganglia

22
C. Nerves and Ganglia

• Nerves
• bundles of nerve cell axons and/or dendrites in
  periphery of body.
• Functional classification
• Sensory (afferent) nerves carry incoming signals
  from sense receptors towards CNS.

23
C. Nerves and Ganglia

• Nerves
• b. Functional classification
• Motor (efferent) nerves
• carry outgoing (away from CNS) signals to muscle
  glands.
• Interneurons nerves
• connect motor and sensory neurons

24
C. Nerves and Ganglia

• Ganglia.
• Ganglia are bundles of nerve cell bodies in
  periphery of body.

25
II. Histology of the N.S.

• Gray White Matter
• White Matter
• Made of mylinated processes
• Gray Matter
• Unmylinated processes and cell bodies

26
II. Histology of the N.S.

• Gray White Matter
• 3. Location

Spinal cord gray matter forms H in center
surrounded by white matter
27
II. Histology of the N.S.

• Gray White Matter
• 3. Location

Brain central white matter with a superficial
gray matter covering
28
III. Neurophysiology

• Membrane Properties
• Neurons must be able to transmit their excitable
  response that started either in the dendrites or
  the nerve cell body down through the axon.
• 2. When at rest, the neuron has more charges
  outside the cell membrane than inside.
• 3. This electric imbalance called the resting
  membrane potential or simply stated the Resting
  potential is the difference b/w the 2 sides of
  the neurons membrane when the cell is not
  conducting an impulse

29
Resting Potential
30
A. Membrane Properties

• 3. Resting Potential ion distribution
• Lg Na outside K inside

31
A. Membrane Properties

• Changes in ion distribution cause
• Stimulation of membrane
• Opens ion channels (pores)
• When this occurs it is called an Action Potential
  or simply stated an Action potential is the
  electrical signal that rapidly travels along the
  axon of neurons causing changes in ion
  distribution.

32
(No Transcript)
33
III. Neurophysiology

• Action Potentials
• Are a specialized kind of electric signal
  generated only by neurons and muscle cells
• are self-propagating
• are all-or-none events.

34
III. Neurophysiology

• Action Potentials have 3 Phases
• Depolarization
• Rapid (1 msec)
• sodium channels open, Na rush in

35
III. Neurophysiology

• Action Potentials have 3 Phases
• Depolarization

• Ends in an overshoot (i.e. brief period of
  time inside of cell is more positive than
  outside)

36
III. Neurophysiology

• Action Potentials have 3 Phases
• Repolarization
• Na channels close
• K channels open and K rushes out

37
III. Neurophysiology

• Action Potentials have 3 Phases
• Repolarization

• overshoots the resting point

38
III. Neurophysiology

• Action Potentials have 3 Phases
• Undershoot Phase
• Membrane is hyperpolarized back to the resting
  potential
• K channels close
• Na/K pump reestablishes the resting potential
• 3 Na moved for 2 K

39
Na / K Pump Reestablishes Resting Potential
40
(No Transcript)
41
III. Neurophysiology

• Nerve Impulse
• Impulse conduction
• Unmyelinated fibers conduct impulse over entire
  membrane surface.
• Myelinated fibers conduct impulse from node to
  node
• Action potential spreads down the fiber to
  adjacent areas of membrane

42
(No Transcript)
43
http//www.youtube.com/watch?vFR4S1BqdFG4 How
the neurons work with the brain
44
(No Transcript)
45
III. Neurophysiology

• All or None Response
• If the nerve fiber responds to the impulse, it
  responds completely
• Greater intensity of stimulation triggers more
  impulses per second, not stronger impulses

46
IV. The Synapse

• Defined
• The junction (cleft) between 2 neurons

47
IV. The Synapse

• Synaptic Transmission
• The process by which the impulse is transmitted
  across the synaptic cleft

48
IV. The Synapse

• Synaptic Transmission
• Steps
• Impulse reaches the synaptic knobs of axon
• synaptic vesicles release neurotransmitter into
  the cleft

49
IV. The Synapse

• Kinds of Neurotransmitters
• Acetylcholine (ACh)
• Made from acetic acid
• Biogenic Amines
• Made from amino acids
• Include
• dopamine,
• epinephrine (adrenaline),
• norepinephrine (noradrenaline),
• Serotonin and histamine

50
C. Kinds of Neurotransmitters

1. Amino Acids
2. Peptides (includes endorphins)
3. ATP
4. Nitric Oxide (NO)
5. Carbon monoxide (CO)

51
Nicotine mimics acetylcholine but can block
function by producing sustained depolarization
52
V. The Reflex Arc

• The Pathway
• Receptors
• Sensory Neuron
• CNS Integration Center
• Motor Neuron
• Effector
• Reflexes
• Are rapid, automatic responses to stimuli

1. A specific stimulus produces the same motor
   response

53
(No Transcript)
54
VI. The Brain

• The Cerebrum
• Function
• Thinking and consciousness
• Willed movements
• Memory
• Vision
• Hearing
• Sensory perception
• Emotions
• Speech

55
A. The Cerebrum

• 2. General Comments
• 83 of total weight of brain
• Paired cerebral hemispheres

56
A. The Cerebrum

• 3. Anatomy
• Lobes Named for bones over them
• Frontal
• Temporal
• Parietal
• Occipital
• Insula

(limbic) inside lateral sulcus
57
Occipital Lobe - Responsible for the processing
of visual information. Damage to this area
results in partial or complete blindness.
Parietal Lobe - Responsible for the sensation of
pain, touch, taste, temperature, pressure. It is
also related with mathematics and logics.
Frontal Lobe - Responsible for the elaboration of
thinking, planning, programming individual needs
and emotion.
Temporal Lobe - It is primarily related with
auditory sense, allowing the recognition of
specific tones and sound intensity. This area has
also a role in memory and emotion processing.
Limbic Lobe - It is involved in the emotional and
sexual aspects of behavior and in the processing
of memory.
58
A. The Cerebrum

• 3. Anatomy
• Fissures
• Deep grooves
• Longitudinal (median, between cerebral
  hemispheres)
• Transverse (between cerebrum and cerebellum)
• c.Sulci (sulcus singular)
• Shallow grooves
• Central between frontal/parietal
• Parieto-occipital
• Lateral between temporal/frontal/ parietal

59
(No Transcript)
60
(No Transcript)
61
A. The Cerebrum

• 3. Anatomy
• Gyri (gyrus singular)
• Elevated ridges of tissue
• Precentral (anterior to central sulcus)
• Postcentral (posterior to central sulcus)
• c.Basic Regions
• Cortex
• Outer layer
• Gray Matter
• White Matter internal
• Basal Nuclei
• Islands of gray matter inside white matter

62
Memorize parts of Brain Song

• http//www.youtube.com/watch?vvYwOtTMUz0c

63
VI. The Brain

• The Diencephalon
• Consists of
• Thalamus
• Hypothalamus
• Epithalamus

64
VI. The Brain

• The Diencephalon
• Thalamus
• Gateway of the Cerebral Cortex for afferent
  (sensory) fibers especially touch taste
• Relay station for sensory and motor impulses

65
VI. The Brain

• The Diencephalon
• Hypothalamus
• Autonomic control center
• Main visceral control center of the body
• Involved in regulation of
• Body temperature
• Water balance and thirst
• Food intake and metabolism
• Sleep and wake cycles

66
VI. The Brain

• The Diencephalon
• Hypothalamus
• Involved in regulation of

• Endocrine functions
• Regulates pituitary
• Produces releasing and inhibiting hormones
• Produces hormones
• Antidiuretic hormone (ADH)
• Oxytocin

67

• The Diencephalon
• Hypothalamus
• Involved in regulation of
• Endocrine functions

• Center for emotional response and behavior
• Thirst center
• Appetite center
• Sex (sexual arousal) center
• Pain center
• Pleasure center
• Fear Anger

68

• The Diencephalon
• Epithalamus

• Forms roof of 3rd ventricle
• Pineal Gland or Body
• Secretes melatonin
• Regulates sleep-wake cycles and moods

• Choroid Plexus
• Forms cerebral spinal fluid

69
VI. The Brain

• The Brain Stem
• Midbrain
• Pons
• Medulla Oblongata

70
VI. The Brain

• The Brain Stem
• Midbrain

1. Conduction pathway between higher and lower brain
   centers
2. Cranial Nerves III IV

Oculomotor Trochlear (eye movement)
71
VI. The Brain

• The Brain Stem
• Pons

1. Conduction pathway between higher and lower brain
   centers
2. Regulates breathing

• Cranial Nerves V VII
• Trigeminal, Abducens, Facial
• Face sensory chewing rolls eye laterally
  facial expression taste

72

• The Brain Stem
• Medulla

• Autonomic reflex center for body homeostasis
• Centers
• Cardiac
• Vasomotor
• Respiratory
• Vomiting
• Hiccupping
• Swallowing
• Coughing
• Sneezing

• Cranial Nerves VIII XII
• Vestibulocochlear, Glossopharyngeal,Vagus,Accessor
  y,Hypoglossal
• Hearing swallow taste GI activity Heart
  activity acts on sternocleidomastoid trapezius
  muscles control tong movement sensory
  impulses

73
VI. The Brain

• Cerebellum
• Assists in maintaining
• Balance
• Posture
• Equilibrium
• Coordinates skeletal muscle

74
VI. The Brain

• Functional Brain Systems
• Limbic System
• Our emotional or affective (feelings) brain
• Includes hypothalamus and parts of the cerebrum

75
VI. The Brain

• Functional Brain Systems
• The Reticular Formation
• Involved in arousal of the brain
• Filters the flood of sensory input (99 filtered
  out)
• Filters out repetitive, familiar or weak signals
• Passes on unussual, strong, or significant signals

76
VI. The Brain

• Functional Brain Systems
• The Reticular Formation
• Involved in arousal of the brain
• Filters the flood of sensory input (99 filtered
  out)
• Filters out repetitive, familiar or weak signals
• Passes on unussual, strong, or significant signals

77
VI. Parts of the Brain How they work

• http//education-portal.com/academy/lesson/parts-o
  f-the-brain.html

78
VI. The Brain

• Functional Brain Systems
• The Ventricles

Cavities within the brain through which
cerebral-spinal fluid flows
79
Demo of Sheep Brain Dissection Id its parts

• http//www.youtube.com/watch?vy7gEWzPqm94

80
VII. The Spinal Cord

1. Function involved with

1. Sensory pathways to brain
2. Motor pathways to body
3. Spinal cord reflexes

81
VII. The Spinal Cord

1. Gray Matter at center of cord

1. Dorsal (posterior) horns cell bodies of the
   sensory neurons
2. Ventral (anterior) horns cell bodies of the
   motor neurons

82
VII. The Spinal Cord

1. Gray Matter at center of cord

1. Lateral horns cell bodies of preganglionic
   neurons of the autonomic nervous system

83
VII. The Spinal Cord

• B. Gray Matter at center of cord

1. Gray commisure connects the lateral halves of
   gray matter

84
VII. The Spinal Cord

• C. Spinal Cord Injuries

• Flaccid Paralysis
• occurs when there is damage to lower motor
  neurons (i.e. anterior horns of gray
  matter)                    
• results in a total loss of muscle tone and
  atrophy of the muscle tissue

85
VII. The Spinal Cord

• C. Spinal Cord Injuries

• Spastic Paralysis
• occurs when there is damage to upper motor
  neurons    
• results in increased muscle tone, due to reduced
  inhibition of, but no voluntary control
  over, skeletal muscle

86
VIII. CNS Protective Structures

1. Skull and Vertebral Column

1. Cranial Bones (8)
2. Vertebral Column (33)

87
VIII. CNS Protective Structures

• Meninges
• three, thin membranes that completely cover the
  brain and the spinal cord.

1. Spinal fluid flows in the space between two of
   the membranes.
2. Include the dura, arachnoid, pia

88
VIII. CNS Protective Structures

1. Meninges

• Dura Matter
• Outer layer    
• In the skull,
• a double
• layered                     
• outer layer periosteal layer attached to
  periosteium of skull
• inner layer meningeal layer is outermost brain
  covering

89
Meninges in the Brain
90
VIII. CNS Protective Structures

1. Skull and Vertebral Column
2. Meninges

• Dura Mater
• In vertebral column             

• Only a single layer
• Arachnoid mater- middle layer 
• Pia mater - inner layer

91
VIII. CNS Protective Structures

• Skull and Vertebral Column
• Meninges
• C.Spaces between the meninges

1.Epidural Above the dura Only in spinal column
2.Subdural Between dura and arachanoid 3.Subara
chnoid Between arachanoid and pia
92
(No Transcript)
93
VIII. CNS Protective Structures

• D. Ventricles
• 1.fluid filled cavities in the brain
• 2.Include

• 1st 2nd or Lateral Ventricle in the cerebral
  hemispheres, just above the epithalmus.
• Third ventricle in diencephalon
• 4th ventricle between the Pons Cerebellum
• Cerebral Aquaduct connects the 3rd to the 4th
  ventricles.

94
(No Transcript)
95
VIII. CNS Protective Structures

• D. Ventricles
• 3. Contain tufts of vascular tissue called
  the choroid plexus which

• Produce cerebral spinal fluid
• b.Allows CSF to flow from ventricles to surface
  of brain and then is return to the blood.

96
(No Transcript)
97
VIII. CNS Protective Structures

1. Cerebral Spinal Fluid

• Nourishes brain and spinal cord
• Gives buoyancy to brain
• Prevents brain from being crushed by its own
  weight
• Produced in choroid plexuses
• volume 150 mL (1/2 cup)
• Replaced every 3-4 hrs
• arachanoid            

98

1. Blood Brain Barrier

1. Is the relative impermeability of brain
   capillaries           

Due to tight junctions, and endothelial lining
of blood vessels in brain
99

1. Blood Brain Barrier

Prevents passage of proteins, blood borne
metabolic wastes (urea, creatine), some toxins,
most drugs
Allows passage of nutrients glucose, essential
amino acids, some electrolytes
100
VIII. CNS Protective Structures

1. Blood Brain Barrier

• Protects brain against fluctuations in
• Hormones
• Ions
• Nutrients
• Toxic substances

101
HIV
102
VIII. CNS Disorders

1. Meningitis

• 1.Infection of the CSF
• Viral less dangerous
• Bacterial can lead to brain
  damage, hearing loss, learning disabilities,
  death          

• 2.Infection of the CSF
• Causes inflamation of the meninges

103
VIII. CNS Protective Structures

1. Meningitis

• 3.Symptoms
• High fever
• Stiff neck
• Intolerance for light          

104
VIII. CNS Protective Structures

1. Encephalitis

• Inflamation of brain tissue and surrounding
  meninges
• Cause viral infections
• Outcome
• Destruction of gray matter
• Can be fatal         

• Alzheimer Disease
• Accumulation of plaque and tangles in brain
• Cause unknown

105
VIII. CNS Protective Structures

1. Parkinson

1. characterized by a decrease in spontaneous
   movements, gait difficulty, postural instability,
   rigidity and tremor
2. Cause the degeneration of the neurons producing
   dopamine

106
Dissecting a Human Brain
http//www.youtube.com/watch?vOMqWRlxo1oQ
107
IX. CRANIAL AND SPINAL NERVES

1. Cranial Nerves

1. Visible on ventral surface
2. 12 pair

108
IX. CRANIAL AND SPINAL NERVES

1. Cranial Nerves

• 12 Pair
• Olfactory smell
• Optic vision
• Oculomotor eye movement pupil dilation
• Trochlear eye movement
• Trigeminal chewing somatosensory (pain
  touch) for head

109
A. Cranial Nerves

• 2. 12 pair

1. Abducens eye movement-lateral
2. Facial Nerve taste, facial expressions,
   somatosensory from ear
3. Vestibulocochlear hearing and balance
4. Glossopharyngeal taste, swallowing,
   sematosensory from tongue

110
A. Cranial Nerves

• 2. 12 pair

1. Vegas GI Heart activity sensory, motor,
   autonomic functions of viscera
2. Spinal Accessory head movement
3. Hypoglossal tongue muscles

Here is a mnemonic On Old Olympus Towering Top
A Famous Vocal German Viewed Some Hops.
111
IX. CRANIAL AND SPINAL NERVES

• B. Spinal Nerves 31 pair

• (1) Cervical
• Thoracic
• Lumbar
• Sacral
• Coccygeal
• Sciatic
• Lumbar plexus
• Intercostal
• Brachial plexus
• Cervical plexus

112
IX. CRANIAL AND SPINAL NERVES

• B. Spinal Nerves 31 pair

A nerve plexus is a network of interwoven nerves.
113
Recall
Divisions of the N.S.
Central N.S.
Peripheral N.S.
Efferent
Afferent
Spinal Cord
Brain
Autonomic
Somatic
Parasympathetic
Sympathetic
114
X. THE PERIPHERAL NS
CNS PNS
115
X. THE PERIPHERAL NS
A. Afferent vs Efferent
116
X. THE PERIPHERAL NS

• A. Afferent vs Efferent

• Afferent NS
• Sensory neurons.
• Proprioceptors sensitive to position and
  movement
• Pick up stimulus and carry it toward the CNS

117
X. THE PERIPHERAL NS

• A. Afferent vs Efferent

• 2.Efferent NS
• Motor neurons
• Carry response impulses from the CNS to the
  effector

118
X. THE PERIPHERAL NS

• A. Afferent vs Efferent

• 3. Disorders of Afferent Efferent systems
• Myasthenia Gravis immune system attacks Ach
  leads to muscle weakness and fatigue
• Multiple sclerosis loss of myelin sheath of
  motor and sensory neurons leads to limb
  weakness, tremors, vision disorders, vertigo

119
X. THE PERIPHERAL NS

• B. Somatic vs Autonomic NS

• Somatic
• Controls skeletal muscles.
• Can be conscious or subconscious
• Has a single neuron between CNS and effector

120
X. THE PERIPHERAL NS

• B. Divisions of the Efferent NS

• 2. Autonomic
• Controls smooth muscles of viscera and glands
• Is subconscious
• Has 2 neurons b/w CNS effector

121
X. THE PERIPHERAL NS

• B. Divisions of the Efferent NS

• 2. Autonomic
• c.Has two neurons between CNS and effector
• Preganglionic neurons
• Originate in spinal cord
• Ganglion neurons
• Nerve cell bodies
• Neurons in effector

122
X. THE PERIPHERAL NS

• C. Sympathetic and Parasympathetic

• 1. Sympathetic
• Fight or Flight
• Consists of
• Preganglionic neurons
• 2 Ganglionic neurons
• Specialized neurons in adrenal gland (secretes
  hormone controlling production of Ach)

123
(No Transcript)
124
XI. Pain Perception

• A. Gate Control Theory

1. Without any stimulation, both large and small
   nerve fibers are quiet and the inhibitory
   interneuron (I) blocks the signal in the
   projection neuron (P) that connects to the brain.
   The "gate is closed" and therefore NO PAIN

125
XI. Pain Perception

• A. Gate Control Theory

2.With non-painful stimulation, large nerve
fibers are activated primarily. This activates
the projection neuron (P), BUT it ALSO activates
the inhibitory interneuron (I) which then BLOCKS
the signal in the projection neuron (P) that
connects to the brain. The "gate is closed" and
therefore NO PAIN.
126
XI. Pain Perception

• A. Gate Control Theory

3.With pain stimulation, small nerve fibers
become active. They activate the projection
neurons (P) and BLOCK the inhibitory interneuron
(I). Because activity of the inhibitory
interneuron is blocked, it CANNOT block the
output of the projection neuron that connects
with the brain. The "gate is open", therefore,
PAIN!!
127
I "Inhibitory Interneuron" P "Projection
Neuron"- inhibition (blocking) excitation
(activation)
128
XI. Pain Perception

• B. Controlling Pain

1.Aspirin acts mostly in PNS reduces
inflammation 2.Morphine acts in CNS to block
pain messages 3.Acupuncture stimulates large
diameter fibers that inhibit pain
(closes the gate)
129
(No Transcript)
130
Sheep Brain Dissection
http//www.youtube.com/watch?vhHl1PslMc8M