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Nervous System
Content
o Introduction of nervous system
o Organization of nervous system
o Nervous tissue
o Neurons and its types
o Supporting cells
o Ascending tract and descending tract
o Reflex
Introduction
 Nervous system is:
 A physically connected network of cells, tissues and organs
that allow us to communicate with and react to the environment
and perform life activities.
 Master controlling and communicating system
 Has two main division
 Central nervous system
 Peripheral nervous system
FOUR PRIMARY FUNCTIONS OF
NERVOUS SYSTEM
 Sensing the world
 Vision, Hearing, Smell,
Taste, Touch
 Transmitting information
 Processing information
 Producing a response
Organization
A. Central Nervous System (CNS)
▫ Brain & spinal cord
▫ Integrative and control centers
-Receives, interprets and sends signals to PNS
B. Peripheral Nervous System (PNS)
▫ Nerves (31 pairs of spinal nerves,12 pairs of cranial nerves)
▫ Communication lines between CNS and rest of body
▫ Two Divisions:
1. Sensory (afferent) Division: Sensory receptors --
CNS
2. Motor (efferent) Division: CNS -- effectors (muscles &
glands)
Motor Division
 Somatic nervous system (voluntary)
- control skeletal muscles
 Autonomic nervous system (ANS) (involuntary)
– regulate smooth muscles, cardiac, glands
▫ Subdivisions:
o Sympathetic :
o “Fight or Flight”
o Activated during emergencies, exercise or vigorous physical activity
o Revs up body to respond to situations that upset homeostasis
o Parasympathetic:
o “Rest & Digest”
o Reduces energy use
o Promotes:
o Storage of energy
o Elimination of wastes
o Homeostasis
 The mammalian brain is
highly complex, containing
many specialized regions that
carry out specific functions.
 Generally, the brain is divided
into:
 Hindbrain
 Midbrain
 Forebrain
THE COMPLEX
BRAIN
Hindbrain
 Medulla:
 Controls autonomic functions.
 Pons:
 Controls sleep stages.
 Cerebellum:
 Coordinates movement,
stores some motor memory.
 Helps maintain posture,
muscle control, and balance
Midbrain
 Located between the hindbrain and forebrain.
 All sensory and motor information that travels
between the forebrain and the spinal cord
passes through the midbrain
 making it a relay station for the central nervous
system.
 the “traffic cops” of the brain.
 Filters sensory input, which allows us to
concentrate.
 Filtering can be affected by higher thoughts.
Forebrain
 Thalamus:
 relay station channeling
sensory information.
 Limbic system:
 basic emotions, drives, and
behaviors.
 Cortex:
 higher thought
Limbic system
 Hypothalamus:
 Master controller of the
endocrine system.
 Amygdala:
 sensations of pleasure or
fear, recognition of fear in
others.
 Hippocampus:
 formation of memories.
Damage to these areas can lead to
amnesia or emotional disturbances
“controls: emotions and memories”
Cortex
 Various areas :
 control
sensory
processing
 motor control,
 thought,
 memory.
Top layer of the brain
Stores: experiences and/or learning
behavior & emotion
Sensory info
concerning touch
vision
memory & emotion,
speech and hearing
Spinal cord
 Grey matter
 mostly made up of cell bodies of neuron
 White matter
 composed of nerve fibers ( ascending and descending tracts )
embedded in neuroglial cells
Nervous Tissue
1. Neurons (nerve cells)
• Functional unit of the nervous system
• Transmit message
Anatomy:
 Cell body – contains nucleus; metabolic center
 Dendrite – fiber that conveys messages toward cell body
 Axon – conduct nerve impulses away from the cell body
 Axon terminals – end of axon; contain neurotransmitters&
release them
 Synaptic cleft/synapse – gap between neurons
Nervous Tissue
2. Supporting cells (Neuroglia)
 CNS: astrocytes, microglia, ependymal cells,
oligodendrocytes
 barrier between capillaries and neurons protect
neurons
 immune/defense
 line brain and spinal cord cavities wrap nerve
fibers
 produces myelin sheaths (covering)
 PNS: Schwann cells, satellite cells
 surround large neurons protect & cushion
Myelin
 Whitish, fatty material that covers nerve fibers to
speed up nerve impulses
Schwann cells
 Surround axons and form myelin sheath
Myelin sheath
• Tight coil of wrapped membranes
Nodes of Ranvier
 Gaps between Schwann cells
• Ganglia: collections of cell bodies
• Bundles of nerve fibers = tracts (CNS) or nerves (PNS)
• White matter
• Dense collections of myelinated fibers
• Gray matter
• Unmyelinated fibers & cell bodies
• (nerve cell bodies, dendrites, axon terminals, bundles of
unmyelinated axons and neuroglia (gray color)
 Dendrites receive signals.
 The cell body integrates
signals.
 The axon transmits action
potential. The myelin
sheath makes the signal
travel faster.
 Synaptic terminals
transmit signals.
The Neuron
Neurons
 Neuron Function
 Irritability:
 ability to respond to stimulus & convert
to nerve impulse
 Conductivity:
 transmit impulse to other neurons,
muscles, or glands
 Classification of Neuron
 Functional Classification
 Structural Classification
1. Functional Classification:
Direction nerve impulse is traveling
Sensory
neurons
Motor
neurons
Interneurons
carry impulses from
sensory receptors to
CNS
carry impulses from
CNS to muscles &
glands
connect sensory &
motor neurons
Vision, hearing,
equilibrium, taste,
smell, pain,
pressure, heat
2. Structural Classification:
Processes extending from cell body
Multipolar Bipolar Unipolar
1 axon, several
dendrites
1 axon, 1 dendrite 1 process
Most common
(99%)
Rare
Short with 2
branches (sensory,
CNS)
Eg. Motor
neurons,
interneurons
Eg. retina, nose,
ear
Eg. PNS ganglia
Nerve Impulses
 Cell membrane at rest = polarized
 Na+outside cell, K+inside cell
 Inside is (-) compared to outside
 Stimulus ---excited neuron (Na+rushes in)--
becomes depolarized
 Depolarization activates neuron to transmit an
action potential (nerve impulse)
 All-or-none response
 Impulse conducts down entire axon
 K+ diffuses out ---repolarization of membrane
 Na+/K+ ion concentrations restored by sodium-
potassium pump (uses ATP)
Exciting a Neuron
Synapse
 Neurons usually do not connect
directly to one another. A gap
called a synapse controls the
transmission of signals.
 Depending on the site of the
synapse, they are often referred to
as axodendritic, axosomatic, or
axoaxonic
 Types of synapse
 Chemical
 Neurotransmitter
 Electrical
presynaptic
neuron
Post synaptic
neuron
Information Transfer Across Chemical
Synapse
 Action potential reaches
axon terminal ----
vesicles release
neurotransmitters (NT)
into synaptic cleft
 NT diffuse across
synapse
bind to receptors
of next neuron
 Transmission of a nerve
impulse =
electrochemical event
Segmental division of Spinal cord
Spinal cord
 Grey matter
 mostly made up of cell bodies of neuron
 White matter
 composed of nerve fibers ( ascending and descending tracts )
embedded in neuroglial cells
CENTRAL NERVOUS SYSTEM
integration / processing / modulating
stimulus
receptor neurone
motor / descending tracts
effector organ / response
PNS
transmission
lower motor neurone
sensory / ascending tracts
Ascending tract
1st
 The ascending tracts transmit sensory information from the sensory
receptors to higher levels of the CNS.
sensory information
 exteroceptive sensation
 origin:-outside the body e.g. temp, touch, light, sound, chemicals,
mechanical
 receptors:- surface layer of skin, mucosa
 proprioceptive sensation
 origin:-within the body e.g. muscles, joints, tendons
 receptors:- deeper layer of skin, tendons, joints, muscle spindles,
ligaments
Information
• conscious sensation
– reach the cerebral cortex
• unconscious sensation
– reach to the areas other than cortex
Ascending tract
VPL
1st
2nd
• cross the mid line
• in front of central canal
The pathways consist of thousands of sets of three
neurons: first-order neuron, second-order neuron, and a
third-order neuron.
Ascending tract
 First order neuron :
 cell body in posterior root ganglion
 peripheral process connects with sensory receptor ending
 central process enter the spinal cord through the posterior root
 synapse with second order neuron in spinal gray matter
 Second order neuron:
 cell body in posterior gray column of spinal cord
 axon crosses the midline ( decussate )
 ascend & synapse with third order neuron in nucleus of thalamus
 Third order neuron:
 cell body in the thalamus
 give rise to projection fibres to the cerebral cortex, postcentral gyrus (
sensory area )
Ascending Tracts of the Spinal
Cord
 Lateral Spinothalamic Tract
 pain, temperature
 Anterior Spinothalamic Tract
 touch, pressure
 Posterior White Column: Fasciculus
Gracilis and Fasciculus Cuneatus
 conscious proprioceptive sense,
discriminative touch, vibratory sense
 Posterior Spinocerebellar Tract&Anterior
Spinocerebellar Tract
 unconscious information from muscle,
joints, skin, subcutaneous tissues
 Spinotectal Tract
 Spinoreticular Tract
 Spino-olivary Tract
Descending tracts
 The descending tracts originate from different cortical areas and
from brain stem nuclei.
 The descending pathway carry information associated with
maintenance of motor activities such as posture, balance, muscle
tone, and visceral and somatic reflex activity
The Descending Tracts
of the Spinal Cord
 Corticospinal Tracts
 for fine skilled movements
 Reticulospinal Tracts
 Inhibit or facilitate voluntary
movement; hypothalamus
controls sympathetic, para-
sympathetic outflows
 Rubrospinal Tract
 Vestibulospinal Tract
 Olivospinal Tract
 Tectospinal tract
 Reflex postural movements concerning sight
 Descending Autonomic Fibers
Corticospinal Tracts
Neuron Function
1. Irritability: ability to respond to stimulus &
convert to nerve impulse
2. Conductivity: transmit impulse to other
neurons, muscles, or glands
Reflex
 Reflex is an action that is performed without conscious thought
as a response to a stimulus.
 Rapid, predictable, involuntary responses to stimuli
1. Somatic Reflexes: stimulate skeletal muscles
 Eg. jerking away hand from hot object
2. Autonomic Reflexes: regulate smooth muscles, heart, glands
 Eg. salivation, digestion, blood pressure, sweating
 Reflex arc
 It is the nerve pathway involved in a reflex action, including at
its simplest a sensory nerve and a motor nerve with a
synapse between them.
Reflex Arc
1) Receptor - reacts to stimulus
2) Sensory Neurons - afferent impulses to CNS
3) Integration centers - synapses in CNS
4) Motor Neurons - efferent impulses from Integration centers to
effector
5) Effector - muscle or glands
ReflexActivities
Patellar (Knee-jerk)
Reflex
Pupillary Reflex
Gently tap your quadriceps tendon, which is located immediately
below your knee cap, with a reflex hammer
Optic nerve --brainstem--muscles
constrictpupil
• Useful for checking brain stem
function and drug use
Other Reflexes
Stimulus (receptors) Response (effector)
The aroma of your favorite
food
Salivation
A nasty odor Nausea
A bright light shining in your
eye
Pupils get smaller
An insect flying towards your
eye
Blinking
Voluntary Reactions
• More neurons and synapses are involved --
longer response times
Reflex = Involuntary Reaction Voluntary Reaction
References
 Elaine N. Marieb, Human Anatomy and Physiology 9th Edition .
 Dr. Henry Gray and Dr. Henry Vandyke Carter , Grays Anatomy
for Students 40th Edition.
 Various internet sources.

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nervous system ppt pptx anatomy system of nerves

  • 2. Content o Introduction of nervous system o Organization of nervous system o Nervous tissue o Neurons and its types o Supporting cells o Ascending tract and descending tract o Reflex
  • 3. Introduction  Nervous system is:  A physically connected network of cells, tissues and organs that allow us to communicate with and react to the environment and perform life activities.  Master controlling and communicating system  Has two main division  Central nervous system  Peripheral nervous system
  • 4. FOUR PRIMARY FUNCTIONS OF NERVOUS SYSTEM  Sensing the world  Vision, Hearing, Smell, Taste, Touch  Transmitting information  Processing information  Producing a response
  • 5. Organization A. Central Nervous System (CNS) ▫ Brain & spinal cord ▫ Integrative and control centers -Receives, interprets and sends signals to PNS B. Peripheral Nervous System (PNS) ▫ Nerves (31 pairs of spinal nerves,12 pairs of cranial nerves) ▫ Communication lines between CNS and rest of body ▫ Two Divisions: 1. Sensory (afferent) Division: Sensory receptors -- CNS 2. Motor (efferent) Division: CNS -- effectors (muscles & glands)
  • 6. Motor Division  Somatic nervous system (voluntary) - control skeletal muscles  Autonomic nervous system (ANS) (involuntary) – regulate smooth muscles, cardiac, glands ▫ Subdivisions: o Sympathetic : o “Fight or Flight” o Activated during emergencies, exercise or vigorous physical activity o Revs up body to respond to situations that upset homeostasis o Parasympathetic: o “Rest & Digest” o Reduces energy use o Promotes: o Storage of energy o Elimination of wastes o Homeostasis
  • 7.
  • 8.
  • 9.
  • 10.  The mammalian brain is highly complex, containing many specialized regions that carry out specific functions.  Generally, the brain is divided into:  Hindbrain  Midbrain  Forebrain THE COMPLEX BRAIN
  • 11. Hindbrain  Medulla:  Controls autonomic functions.  Pons:  Controls sleep stages.  Cerebellum:  Coordinates movement, stores some motor memory.  Helps maintain posture, muscle control, and balance
  • 12. Midbrain  Located between the hindbrain and forebrain.  All sensory and motor information that travels between the forebrain and the spinal cord passes through the midbrain  making it a relay station for the central nervous system.  the “traffic cops” of the brain.  Filters sensory input, which allows us to concentrate.  Filtering can be affected by higher thoughts.
  • 13. Forebrain  Thalamus:  relay station channeling sensory information.  Limbic system:  basic emotions, drives, and behaviors.  Cortex:  higher thought
  • 14. Limbic system  Hypothalamus:  Master controller of the endocrine system.  Amygdala:  sensations of pleasure or fear, recognition of fear in others.  Hippocampus:  formation of memories. Damage to these areas can lead to amnesia or emotional disturbances “controls: emotions and memories”
  • 15. Cortex  Various areas :  control sensory processing  motor control,  thought,  memory. Top layer of the brain Stores: experiences and/or learning behavior & emotion Sensory info concerning touch vision memory & emotion, speech and hearing
  • 16. Spinal cord  Grey matter  mostly made up of cell bodies of neuron  White matter  composed of nerve fibers ( ascending and descending tracts ) embedded in neuroglial cells
  • 17.
  • 18. Nervous Tissue 1. Neurons (nerve cells) • Functional unit of the nervous system • Transmit message Anatomy:  Cell body – contains nucleus; metabolic center  Dendrite – fiber that conveys messages toward cell body  Axon – conduct nerve impulses away from the cell body  Axon terminals – end of axon; contain neurotransmitters& release them  Synaptic cleft/synapse – gap between neurons
  • 19.
  • 20. Nervous Tissue 2. Supporting cells (Neuroglia)  CNS: astrocytes, microglia, ependymal cells, oligodendrocytes  barrier between capillaries and neurons protect neurons  immune/defense  line brain and spinal cord cavities wrap nerve fibers  produces myelin sheaths (covering)  PNS: Schwann cells, satellite cells  surround large neurons protect & cushion
  • 21.
  • 22. Myelin  Whitish, fatty material that covers nerve fibers to speed up nerve impulses Schwann cells  Surround axons and form myelin sheath Myelin sheath • Tight coil of wrapped membranes Nodes of Ranvier  Gaps between Schwann cells
  • 23. • Ganglia: collections of cell bodies • Bundles of nerve fibers = tracts (CNS) or nerves (PNS) • White matter • Dense collections of myelinated fibers • Gray matter • Unmyelinated fibers & cell bodies • (nerve cell bodies, dendrites, axon terminals, bundles of unmyelinated axons and neuroglia (gray color)
  • 24.  Dendrites receive signals.  The cell body integrates signals.  The axon transmits action potential. The myelin sheath makes the signal travel faster.  Synaptic terminals transmit signals. The Neuron
  • 25. Neurons  Neuron Function  Irritability:  ability to respond to stimulus & convert to nerve impulse  Conductivity:  transmit impulse to other neurons, muscles, or glands  Classification of Neuron  Functional Classification  Structural Classification
  • 26. 1. Functional Classification: Direction nerve impulse is traveling Sensory neurons Motor neurons Interneurons carry impulses from sensory receptors to CNS carry impulses from CNS to muscles & glands connect sensory & motor neurons Vision, hearing, equilibrium, taste, smell, pain, pressure, heat
  • 27. 2. Structural Classification: Processes extending from cell body Multipolar Bipolar Unipolar 1 axon, several dendrites 1 axon, 1 dendrite 1 process Most common (99%) Rare Short with 2 branches (sensory, CNS) Eg. Motor neurons, interneurons Eg. retina, nose, ear Eg. PNS ganglia
  • 28.
  • 29. Nerve Impulses  Cell membrane at rest = polarized  Na+outside cell, K+inside cell  Inside is (-) compared to outside  Stimulus ---excited neuron (Na+rushes in)-- becomes depolarized  Depolarization activates neuron to transmit an action potential (nerve impulse)  All-or-none response  Impulse conducts down entire axon  K+ diffuses out ---repolarization of membrane  Na+/K+ ion concentrations restored by sodium- potassium pump (uses ATP) Exciting a Neuron
  • 30. Synapse  Neurons usually do not connect directly to one another. A gap called a synapse controls the transmission of signals.  Depending on the site of the synapse, they are often referred to as axodendritic, axosomatic, or axoaxonic  Types of synapse  Chemical  Neurotransmitter  Electrical presynaptic neuron Post synaptic neuron
  • 31.
  • 32. Information Transfer Across Chemical Synapse  Action potential reaches axon terminal ---- vesicles release neurotransmitters (NT) into synaptic cleft  NT diffuse across synapse bind to receptors of next neuron  Transmission of a nerve impulse = electrochemical event
  • 33. Segmental division of Spinal cord
  • 34. Spinal cord  Grey matter  mostly made up of cell bodies of neuron  White matter  composed of nerve fibers ( ascending and descending tracts ) embedded in neuroglial cells
  • 35. CENTRAL NERVOUS SYSTEM integration / processing / modulating stimulus receptor neurone motor / descending tracts effector organ / response PNS transmission lower motor neurone sensory / ascending tracts
  • 36. Ascending tract 1st  The ascending tracts transmit sensory information from the sensory receptors to higher levels of the CNS. sensory information  exteroceptive sensation  origin:-outside the body e.g. temp, touch, light, sound, chemicals, mechanical  receptors:- surface layer of skin, mucosa  proprioceptive sensation  origin:-within the body e.g. muscles, joints, tendons  receptors:- deeper layer of skin, tendons, joints, muscle spindles, ligaments Information • conscious sensation – reach the cerebral cortex • unconscious sensation – reach to the areas other than cortex
  • 37. Ascending tract VPL 1st 2nd • cross the mid line • in front of central canal The pathways consist of thousands of sets of three neurons: first-order neuron, second-order neuron, and a third-order neuron.
  • 38. Ascending tract  First order neuron :  cell body in posterior root ganglion  peripheral process connects with sensory receptor ending  central process enter the spinal cord through the posterior root  synapse with second order neuron in spinal gray matter  Second order neuron:  cell body in posterior gray column of spinal cord  axon crosses the midline ( decussate )  ascend & synapse with third order neuron in nucleus of thalamus  Third order neuron:  cell body in the thalamus  give rise to projection fibres to the cerebral cortex, postcentral gyrus ( sensory area )
  • 39.
  • 40. Ascending Tracts of the Spinal Cord  Lateral Spinothalamic Tract  pain, temperature  Anterior Spinothalamic Tract  touch, pressure  Posterior White Column: Fasciculus Gracilis and Fasciculus Cuneatus  conscious proprioceptive sense, discriminative touch, vibratory sense  Posterior Spinocerebellar Tract&Anterior Spinocerebellar Tract  unconscious information from muscle, joints, skin, subcutaneous tissues  Spinotectal Tract  Spinoreticular Tract  Spino-olivary Tract
  • 41. Descending tracts  The descending tracts originate from different cortical areas and from brain stem nuclei.  The descending pathway carry information associated with maintenance of motor activities such as posture, balance, muscle tone, and visceral and somatic reflex activity
  • 42. The Descending Tracts of the Spinal Cord  Corticospinal Tracts  for fine skilled movements  Reticulospinal Tracts  Inhibit or facilitate voluntary movement; hypothalamus controls sympathetic, para- sympathetic outflows  Rubrospinal Tract  Vestibulospinal Tract  Olivospinal Tract  Tectospinal tract  Reflex postural movements concerning sight  Descending Autonomic Fibers
  • 43.
  • 45. Neuron Function 1. Irritability: ability to respond to stimulus & convert to nerve impulse 2. Conductivity: transmit impulse to other neurons, muscles, or glands
  • 46.
  • 47. Reflex  Reflex is an action that is performed without conscious thought as a response to a stimulus.  Rapid, predictable, involuntary responses to stimuli 1. Somatic Reflexes: stimulate skeletal muscles  Eg. jerking away hand from hot object 2. Autonomic Reflexes: regulate smooth muscles, heart, glands  Eg. salivation, digestion, blood pressure, sweating  Reflex arc  It is the nerve pathway involved in a reflex action, including at its simplest a sensory nerve and a motor nerve with a synapse between them.
  • 48. Reflex Arc 1) Receptor - reacts to stimulus 2) Sensory Neurons - afferent impulses to CNS 3) Integration centers - synapses in CNS 4) Motor Neurons - efferent impulses from Integration centers to effector 5) Effector - muscle or glands
  • 49.
  • 50.
  • 51. ReflexActivities Patellar (Knee-jerk) Reflex Pupillary Reflex Gently tap your quadriceps tendon, which is located immediately below your knee cap, with a reflex hammer Optic nerve --brainstem--muscles constrictpupil • Useful for checking brain stem function and drug use
  • 52. Other Reflexes Stimulus (receptors) Response (effector) The aroma of your favorite food Salivation A nasty odor Nausea A bright light shining in your eye Pupils get smaller An insect flying towards your eye Blinking
  • 53. Voluntary Reactions • More neurons and synapses are involved -- longer response times Reflex = Involuntary Reaction Voluntary Reaction
  • 54.
  • 55. References  Elaine N. Marieb, Human Anatomy and Physiology 9th Edition .  Dr. Henry Gray and Dr. Henry Vandyke Carter , Grays Anatomy for Students 40th Edition.  Various internet sources.

Editor's Notes

  1. Glutamate -Sensory neurons and cerebral cortex
  2. Acetylcholine (ACh) is an excitatory neurotransmitter secreted by motor neurons that innervate muscle cells, basal ganglia, preganglionic neurons of the autonomic nervous system, and postganglionic neurons of the parasympathetic and sympathetic nervous systems. 
  3. Ventral posterolateral nucleus.- in thalamus of brain.
  4. Decussate in spinal cord or medulla oblongata
  5. Babinski Reflexes
  6. Babinski Reflexes