Download Central Nervous System (CNS)

Neurophysiology of
Sensations
Central
Nervous
System
(CNS)
Peripheral
Nervous
System
(PNS)
Cervical
Thoracic
Lumbar
Sacral
Cocygeal
Components of the Nervous
System
Figure 11.1
Principle Parts of Nervous
System
• Central Nervous System (CNS)
– Components: brain and spinal cord
– Functions: receives, processes, and transfers
information
• Peripheral Nervous System (PNS)
– Components: nerves outside CNS
– Sensory neurons: carry information toward the
CNS
– Motor neurons: carry information away from
CNS
Types of Neurons in the Nervous
System
1.
Sensory Neuron
2.
Interneuron
3.
Motor Neuron
Figure 11.2
Communication Cells of System
• Neurons: Actual Communication Cells
• Cell Body
• Axon (one – away)
• Dendrites (grow more with learning!)
• Neuroglia: Support Cells of the Nervous System
• Schwann Cells (PNS)
• Oligodendrocyte (CNS)
Neuroglia vs. Neurons
•
•
•
•
Neuroglia divide.
Neurons do not.
Most brain tumors are “gliomas.”
Most brain tumors involve the neuroglia
cells, not the neurons.
• Consider the role of cell division in
cancer!
How Neurons Function
(Physiology)
 Irritability – ability to respond to
stimuli
 Conductivity – ability to transmit
an impulse
 The plasma membrane at rest is
polarized
Fewer positive ions are inside the
cell than outside the cell
Slide 7.17
Transfer of Information from
Neuron to Target
• Synaptic transmission
–Release of neurotransmitter
• Effects of neurotransmitter:
– Electrical energy converted to chemical energy
– cell
–Role of postsynaptic neuron: integrate and
process information
–Role of postsynaptic muscle cell – must respond.
–Nervous system has final and absolute control
over skeletal muscle cells!
Peripheral Nervous System:
Relay Information between
Tissues and CNS
• Nerves: carry signals to and from CNS
– Cranial nerves: connect directly to brain
– Spinal nerves: connect to spinal cord
• Sensory neurons: provide information to
CNS
Autonomic Functioning
 Parasympathetic – housekeeping
activites
 Conserves energy
 Maintains daily necessary body functions
 Remember as the “D” division - digestion,
defecation, and diuresis
Slide
Central Nervous System: Brain &
Spinal Cord
• CNS protection
– Bone: skull and vertebrae
– Meninges: dura mater, arachnoid, and pia mater
– Cerebrospinal fluid: between arachnoid and pia
– Blood-brain barrier: carries nutrients and waste for
CNS
• Spinal cord: relays information through nerve
tracts in white matter
Ventricles of the Brain and
Circulation of Cerebrospinal Fluid
Figure 11.12
Brain: Major Divisions
• Hindbrain: coordinates basic, automatic, vital
functions
• Medulla oblongata: controls automatic
functions of internal organs
• Cerebellum: coordinates basic
movements
• Pons: aids flow of information
• Midbrain: coordinates muscles related to
vision & hearing
• Reticular Formation - Wakefulness
Brain: Processes and Acts on
Information
• Forebrain: receives and integrates
information concerning emotions and
conscious thought
• Hypothalamus: helps regulate
homeostasis
• Thalamus: receiving, processing, and
transfer center
• Limbic system: neuronal pathways
involved in emotions and memory
• Cerebrum/cerebral cortex: higher
Regions of the Brain
 Cerebral
hemispheres
 Diencephalon
 Brain stem
 Cerebellum
Figure 7.12
Slide 7.27
Cerebral Hemispheres (Cerebrum)
 The surface
is made of
ridges (gyri)
and grooves
(sulci)
Figure 7.13a
Slide
Lobes of the Cerebrum
Figure 7.15a
Slide
Specialized Areas of the Cerebrum
 Somatic sensory area – receives
impulses from the body’s sensory
receptors
 Primary motor area – sends impulses to
skeletal muscles
 Broca’s area – involved in our ability to
speak
Slide 7.30
Specialized Area of the Cerebrum
Figure 7.13c
Slide
Sensory and Motor Areas of the
Cerebral Cortex
Figure 7.14
Slide 7.31
Thalamus
-Surrounds the third ventricle
-The relay station for sensory impulses
-Transfers impulses to the correct part of
the cortex for localization and
interpretation
Slide 7.35
Hypothalamus
 Under the thalamus
 Important autonomic nervous system
center
 Helps regulate body temperature
 Controls water balance
 Regulates metabolism
Slide
Hypothalamus
 An important part of the limbic system
(emotions)
 The pituitary gland is attached to the
hypothalamus
Slide
Hind Brain: Pons
 The bulging center part of the brain
stem
 Mostly composed of fiber tracts
 Includes nuclei involved in the control of
breathing
Slide 7.40
Medulla Oblongata




The lowest part of the brain stem
Merges into the spinal cord
Includes important fiber tracts
Contains important control centers
 Heart rate control
 Blood pressure regulation
 Breathing
 Swallowing
 Vomiting
Slide 7.41
Sleep: Midbrain
Brain Activity continues during
sleep!
• Sleep center: reticular activating system
(RAS)
–Stages: based on electroencephalograms
(EEGs)
• Stage 1: transitional, random small waves on EEG
• Stage 2: skeletal muscles relax, little eye or body movement, EEG
shows sleep spindles
Sleep
• Stage 3: heart and respiration slower, EEG shows slow wave sleep
• Stage 4: difficult to awaken, heart and respiration slowest, body
temperature decreased
• REM (rapid eye movement) Sleep: dreaming, EEG same as awake.
Lack of REM = sleep deprivation
• Sleep cycles through these stages, REM occurring every 90 minutes of
so.
Memory: Storing and Retrieving
Information
• Short term: working memory, information
from previous few hours
• Occurs in the Limbic System
• Long term: information from previous days
to years
• Occurs in the Cerebral Cortex
• Permanent Change to Neurons
• “Builoding Dendrites
Alzheimer’s Disease
 Progressive degenerative brain disease
 Mostly seen in the elderly, but may
begin in middle age
 Structural changes in the brain include
abnormal protein deposits and twisted
fibers within neurons
 Victims experience memory loss,
irritability, confusion and ultimately,
hallucinations and death
Slide 7.51
Traumatic Brain Injuries
 Concussion
 Slight brain injury
 No permanent brain damage
 Contusion
 Nervous tissue destruction occurs
 Nervous tissue does not regenerate
 Cerebral edema
 Swelling from the inflammatory response
 May compress and kill brain tissue
Slide 7.49
Cerebrovascular Accident (CVA)
 Commonly called a stroke
 The result of a ruptured blood vessel
supplying a region of the brain
 Brain tissue supplied with oxygen from
that blood source dies
 Loss of some functions or death may
result
Slide 7.50
• NS has 3 main functional divisions;
a) Sensory division of NS:
• Detects changes in internal and external environments
and informs the CNS about them.
b) Motor division of NS:
• Initiates and controls the activities of skeletal muscles
• Controls the activities of plain muscles, cardiac muscles
and even glands.
c) Intellectual division of NS:
• Consciousness, memory, learning, thoughts, emotions
Centers
Tracts
Afferents
Receptors
1) Def.,
• Sensation is a conscious perception of particular feeling caused
by stimulation of certain type of receptor by its adequate
stimulus.
2) Classifications:
Sensations
General
Special
Organic
1) Special sensations:
• Vision, hearing, taste, smell and equilibrium
2) General sensations:
• Arise from receptors distributed allover the body
• Are classified into;
a) Somatic sensations: from somatic structures e.g. skin
b) Visceral sensations: from viscera
3) Organic senses: e.g. thirst, hunger and sexual desire
Def,
• These sensations arise from somatic structures of all
the body i.e. skin and deep tissues e.g. sk ms
Types:
• They include according to their adequate stimulus:
1. Mechanoceptive sensations: 2 types;
– Tactile e.g. touch, pressure, and vibration
sensations.
– Proprioceptive sensations e.g. sense of position
and movement
2. Pain sensation.
3. Thermal sensation; cold and warm.
Def.,
• Feeling produced by application of light
mechanical pressure to the skin
Types:
• They include 2 types :
1. Crude touch
2. Fine touch
Def.,
• Poorly localized touch sensation produced by touching
the skin with diffuse ill defined object e.g. a piece of
cotton or the touch of clothes.
Receptors:
• Free nerve endings
• Hair end organs
Pathway:
• Ventral or anterior
spinothalamic tract
Def.,
• Highly localized touch sensation produced by
application of a well localized object to the skin e.g. a
tip of a pencil or a head of a pin or teeth of a comb.
Receptors:
• Meissner's corpuscles
• Merkel's discs
Pathway:
• Dorsal column medial
leminiscal system or
gracile and cuneate
tracts
Types:
• It includes :
1. Tactile localization: is the ability to localize the point
of touch with eyes closed
2. Tactile discrimination : is the ability to perceive 2
points of touch with eyes closed as 2 separate
points of touch
3. Stereognosis: is the ability to recognize a familiar
object e.g. key with eyes closed
Pressure:
• It is a feeling produced by the application of heavy
mechanical stimuli to the skin
Vibration :
It is a feeling of rhythmic pressure changes produced by
the rapid repetitive stimulation of certain
mechanoreceptors e.g. Pacinian and Meissner's
corpuscles
It is tested by use of tuning fork
Pathway: both sensations are carried by Gracile and
Cuneate tract
Def :
• Feeling produced by stimulation of proprioceptors in
skeletal muscle and joints
• Or It is the conscious perception of the position and
movements of the different parts of the body,
particularly the limbs and joints.
• Types:
a) Static or sense of position
b) Dynamic or sense of movement of joints
Pathway: Dorsal column medial leminiscal
system or Gracile and Cuneate tract
Significance:
• The brain and other motor centers e.g. basal ganglia,
cerebellum use this information in the control of
posture and movements
N.B.
• Maintaining the body equilibrium or balance needs
discharge from 3 kinds of receptors;
1. Proprioceptors of foot
2. Visual receptors
3. Vestibular receptors (Crista in semicircular canals
and macula in utricle and saccule) in inner ear
Crista
Amuplaris
Macula
Def :
•Unpleasant sensory and emotional experience
associated with actual tissue damage.
Significance:
•Pain is a protective mechanism for the body.
•It occurs whenever the tissues are damaged and it
initiates protective reflex for removing the injurious
stimulus
Receptors:
•Free nerve endings
Pathway: lateral spinothalamic tract
Types:
• According to its source;
1. Cutaneous pain: pain comes from skin
2. Deep pain: pain comes from deep tissues e.g.
skeletal muscle, joints, ligaments, and tendons and
bone
3. Visceral pain: pain comes from viscera e.g. stomach
• According to its characters;
1. Fast pricking pain
2. Slow burning pain
Sensation
Pain
Crude touch
Fine touch
Deep pressure
Vibration
Proprioception
Tool used
Pin
Receptors
Free nerve endings
Pathway or
tract
Lateral
spinothalamic
tract
Cotton wool Free nerve endings Ventral
and hair end organs spinothalamic
tract
compass or Meissner's
Dorsal column
pencil or coin corpuscles
(gracile and
Merkels disc
cuneate tract)
Different
•Pacinian
Dorsal column
weights
•Ruffini endings
(gracile and
cuneate tract)
Tuning fork
•Pacinian
Dorsal column
•Meissner’s
(gracile and
corpuscles
cuneate tract)
Finger or toe •Muscle spindle
Dorsal column
of the patient •Pacinian corpuscles (gracile and
•Golgi tendon organs cuneate tract)
Def.
• Is the impairment of nerve functions due to high blood
glucose
Manifestations:
Sensory Neuropathy - Symptoms
Motor Neuropathy Symptoms
Autonomic Neuropathy Symptoms
Neuropathy - Signs
Glove and stock Hypoesthesia
Painless nature of diabetic
foot disease
CNS DEFINITIONS
• Nucleus-collection of nerve cells inside the
CNS
• Ganglion-collection of nerve cell bodies
outside the CNS
• Centers- collections of cell bodies and
dendrites in the CNS
• Tracts-bundles of axons within the CNS
Sensory nerve damage
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