Download Function

Physl important note
• Function of glial cells:
1. Astrocytes
• Functions
1.
2.
3.
4.
5.
6.
7.
Physical support to neurons
Help transfer nutrients to neurons
Take up and degrade released neurotransmitter
Enhance synapse formation & ↑ Synaptic transmission
Maintain normal Brain ECF ion concentration
Formation of blood – brain – barrier
Repair of brain injuries & formation of neural scar tissue
2. Oligodendrocytes
• Functions
1.
Forms myelin sheath in the CNS.
3.
Microglia
• Functions
1. Phagocytosis [defense cells of CNS]
2. Release nerve growth factor
4.
Ependymal Cells
• Functions
1. Line internal cavities of brain and spinal cord
2. Formation of Cerebrospinal fluid [CSF].
3. Work as Neural Stem Cell – to form new neurons and
glial cells
Basal Nuclei
• Functions:
– Co-ordination of movements
– Muscle tone regulation
– Posture maintenance
 Thalamus
• All sensory information passes.
• Crude awareness of sensation.
Cerebellum
 Functions:
– Balance of body.
– Muscle tone.
– Co-ordination and planning of skilled movements e.g. dance.
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SPINAL CORD
• Function:
– Conduit for Information passage To & fro Brain
– Center for some reflexes
REFLEXES
• Examples
a.
b.
c.
Reflexes carry out the automatic actions of swallowing,
sneezing, coughing, vomiting.
Reflexes maintain balance and posture; e.g., spinal reflexes
control trunk and limb muscles.
Brain reflexes involve reflex center in brainstem; e.g., reflexes
for eye movement.
 Polysynaptic reflex
 e.g. Withdrawal reflex, Abdominal reflex, Plantar reflex
 Stretch reflex:
 Sudden stretch to a muscle leads to contraction of that muscle is known
as stretch reflex.
 Stretch Reflex is a basic spinal reflex. Example Knee jerk
• The 5 components of Stretch Reflex
–
–
–
–
–
Sensory receptor – Muscle Spindle in skeletal muscle
Afferent pathway – 1a fibers
Center – spinal cord
Efferent fibers – α-motor neuron
Effector organ – skeletal muscle contraction
Types of muscle fibers
I. Extrafusal muscle fibers
– Takes part in muscle contraction
– Supplied by α - motor neuron
II. Intrafusal muscle fibers
– Also called as Muscle Spindle
– Receptors for stretch reflex
– supplied by γ - motor neuron
Types of Nerve Fibers
• Know only the major function
Types of motor neuron
• α - motor neuron
– Supply Extrafusal fibers
• γ - motor neuron
– Supply Intrafusal fibers
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Sensory receptor
• Every receptor is most sensitive to a particular
modality of stimuli. That specific form of
energy to which the receptor is most sensitive
is called as its Adequate Stimulus.
– e.g. rods & cones are stimulated by light not heat,
sound etc
• Know the type and the function only
Difference Between
•
Receptor potential





In the Receptor
Graded
Doesn’t obey all or none rule
Can be summated
Unpropagated
• Action potential





In the Sensory Nerve fiber
Not Graded
Obeys all or none rule
Not summated
Propagated
Adaptation or Desensitization
I. Phasic
Receptors:
Receptors
Rapidly
Adapting
– E.g. pacinian corpuscles, Meissners corpusle.
– For Touch, Pressure & Smell etc.
II. Tonic Receptors: Slow Adapting receptors
– E.g. Nociceptors, muscle spindles, Proprioceptors
– For Pain, Body position etc.
Receptor field
• Receptor field of a sensory unit is the area
from which a stimulus produces response
in that unit.
• Smaller the receptive field – More precise
the information e.g. Finger tips
• Larger the receptive field- less precise the
information e.g. Back, arms, legs.
Fiber type :
A
Number:
II
Origin:
Muscle spindle - flower-spray ending, touch,
pressure
• Primary afferent
sensations are
–
–
–
–
fibers which carry cutaneous
Large myelinated fiber Aα –
proprioception
Large myelinated fiber Aβ – touch, pressure.
Small myelinated fiber Aδ –
fast pain, Temp
Small unmyelinated C fibers – slow pain, Temp
Sensory pathway
•
•
Dorsal Column Medial Lemniscal system
• Also called as
• Posterior column Tract or
• Tracts of Goll & Burdach or
• Fasciculus Gracilis and Cuneatus
• Carries sensations of fine touch, position, vibration, two point
discrimination & stereognosis.
Anterolateral system
• Consists of …
1. Anterior (Ventral) spinothalamic tract
• carries crude touch and pressure,
2. Lateral spinothalamic tract
• carries pain and temperature.
Deferent between
DORSAL COLUMN PATHWAY
• Carries fine touch, position,
pressure, vibration, two point
discrimination, stereognosis
• Afferent sensory fibers aβ
type.
• Very fast velocity 30 – 70 m/s
• ANTEROLATERAL PATHWAY
• Carries pain & temperature
(lat. Sp.Th)
• Crude touch & pressure (vent,
sp. Th)
• Afferent sensory fibers aδ
• 6 – 30 m/s (myelinated) fast
pain
• C fibers – 0.5 – 2 m/s
(unmyelinated) slow pain
Temperature
• Afferent from cold receptors – Aδ & C fibers.
• Afferent from warm receptors – C fibers.
• Temperature sensation is carried via lateral
spinothalamic tract.
• Aδ (myelinated) : for fast pain”sharp loclized”
• C fibers (unmyelinated): slow pain “ dull,
diffuse”
Both Aδ & C fibers terminate in dorsal horn.
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Brain Analgesic System
• Brain has built in analgesic system.
• By sending message through descending
analgesic pathway to the inhibitory neuron in the
Dorsal horn cell of spinal cord.
• Brain descending pathways release Enkephalin
which bind with opiate receptors at afferent pain
fiber terminals in Dorsal horn of spinal cord and
work like Morphine (powerful analgesic).
• Endorphin, Enkephalin and Dynorphin are
endogenous or natural analgesic system. They
suppress release of substance P.
Somatosensory cortex (S1 area)
• It is located in post central gyrus of the cerebral
cortex.
• There is detailed localization of the fibers from
various parts of the body.
• Somatosensory cortex is a site of perception of
– Somasthetic sensation [touch, pain, temperature, pressure]
– Proprioception
• The arrangement of thalamic fibers in S1 is such that
parts of body are represented in order, along the
post central gyrus with the feet on the top & head at
the lower end of the gyrus.
Somatosensory cortex (S1 area)
• Here different body parts are not represented equally
• Size of cortical receiving area for impulses from a particular
part of the body is proportionate to the No. of receptors.
• Thus very large area is occupied by impulses coming from
lips, face, and hand (thumb) also parts of mouth concerned
with speech.
• Trunk & back has small area of presentation in sensory
cortex.
• Each side of the cortex receives information from opposite
side of the body.
• From here many of signals spread directly to motor cortex,
play a major role in controlling motor signals that activate
muscle contraction
Somatosensory area II
• SII is located in the superior wall of the sylvian fissure,
the fissure that separate the temporal lobe from the
frontal & the prietal lobe.
• Face is presented anteriorly, arms centrally & legs
posteriorly.
• The presentation of the body parts on sylvian fissure is
not as complete & detailed as in post central gyrus.
• Little is known about role of somatosensory area II
(SII).
• Signals enter into SII from brain stem, also SI area and
other areas of brain visual & auditory.
• Projection from SI are required for function of SII.
Somatosensory Association Area
•
•
Located in parietal lobe behind area SI.
It receives signals from ;
1.
2.
3.
4.
•
Somatosensory area I
Thalamus
Visual cortex
Auditory cortex
Effect of removing …
– Person looses the ability to recognize objects felt on the
opposite side of the body, he looses the sense of form of his
own body on the opposite side also. He forget it is there.
– This complex sensory deficit is called Amorphosynthesis.
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CORTICOSPINAL TRACTS:
• It is the most important motor pathway from
motor cortex
• Origin:
– 30% from Primary Motor Cortex
– 30% from Premotor and Supplementary Motor Area
– 40 % from Somatosensory Area
• Course:
– passes through posterior limb of internal capsule and downwards
through brainstem.
– Majority of fibers (80%) than cross in lower medulla to the opposite
side and descend as lateral Corticospinal tracts.
– 20% uncrossed continue as Anterior Corticospinal Tract. Eventually
most of them also cross before termination in Spinal Cord
CORTICOSPINAL TRACTS:
• Termination:
– Terminate principally on the Interneurons, in the
intermediate region of cord grey matter ,
– A few terminate on sensory relay neurons in dorsal horn
and
– A few terminate directly on Anterior Motor Neuron.
– direct innervation of alpha motor neurons by pyramidal
tract axons is mainly to distal muscles and is associated with
the ability to execute fine, precise movements
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RUBROSPINAL TRACT
• Functions - Involved in movements of distal
limbs (hand & feet) also regulates tone and
posture.
• It is excitatory to flexors and inhibitory to
extensor muscles.
VESTIBULOSPINAL TRACT
• Function - Excitatory to ipsilateral extensor.
Inhibitory to flexor muscles
• Regulates muscle tone for maintaining
balance in response to head movement
Difference between Pyramidal and
Extrapyramidal Tract
PYRAMIDAL TRACTS
4. 80 % of Corticospinal tracts
(lateral) cross in medulla
20 % of corticospinal tract
(ventral) cross in spinal cord
Because of crossing cerebral
cortex controls opposite side
of the body
5. Function:
- Lat. Corticospinal tract –
fine movement of fingers eg.
Writing, needle work
- Ventral corticospinal tract –
Axial or Postural Movement
EXTRA PYRAMIDAL TRACTS
Major extra pyramidal tracts, some
cross and others are uncrossed
Function:
Control of body posture involving
involuntary movements of axial
and Proximal limb muscle
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BASAL NUCLEI - FUNCTIONS
• Modulation of motor activities through
neuronal circuits.
• Maintain purposeful motor activity while
• suppressing unwanted or useless movement.
• Change the Timing and Scale the Intensity of
Movements
• Basal ganglia function in association with the
corticospinal system to determine & control
complex patterns of motor activity.
BASAL NUCLEI - FUNCTIONS
• Regulate muscle tone - Inhibit muscle tone
throughout the body
• Monitor and coordinate slow, sustained
contractions related to posture and support.
• Prevent abnormal involuntary movements.
• Control group of movements for emotional
expression.
• Role in procedural learning, routine behaviors or
"habits" such as bruxism.
• Role in Memory, emotion, Reward Learning and
other cognitive functions.
BASAL NUCLEI - CONNECTIONS
• Main input:
Comes from the cerebral cortex (motor area)
and projects to the Striatum (Caudate
nucleus & Putamen)
• Main output:
Is from Globus Pallidus via the thalamus to the
cerebral cortex (motor area)
GLU
GABA
GABA
GLU
GLU
GABA
GABA
GLU
GLU
GABA
GLU
GLU
Parkinson’s Disease
• Clinical symptoms
• Rigidity – Cogwheel, Lead Pipe
• Tremor (Resting) – Pill rolling type
• Hypokinesia/Akinesia - poverty and slowness in
initiating and carrying out different motor movement.
• Face – expressionless, Mask like face
• Blinking of eyelid is reduced
• Writing becomes small – micrographic and spidery
• Changes in posture – Stoop is characteristic
• Gait – becomes hurrying, festinant, short and shuffling
with poor arm swinging
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CEREBELLAR FUNCTIONS
1) Maintenance of balance
2) Enhancement of muscle tone
3) Coordination and planning of skilled voluntary muscle
activity
4) Sequences the motor activities
5) Monitors and makes corrective adjustments in the activities
initiated by other parts of the brain
6) Compares the actual motor movements with the intended
movements and makes corrective changes.
7) The cerebellum does not initiate movement, but it
contributes to coordination, precision, and accurate timing.
8)
Functional imaging studies have shown cerebellar activation in relation to
language, attention, and other cognitive functions.
9) Correlation studies have shown interactions between the cerebellum and
non-motor areas of the cerebral cortex; and a variety of non-motor
symptoms have been recognized in people with damage that appears to be
confined to the cerebellum
10) functional MRI suggest that more than half of the cerebellar cortex is
interconnected with association zones of the cerebral cortex.
Functional Organization of the
Cerebellum
Functionally cerebellum can be divided into . . .
• The Floculonodular lobe – Vestibulocerebellum
– participates mainly in balance and spatial orientation
• Intermediate zone - Spinocerebellum
– Enhances muscle tone and coordinates skilled voluntary
movements
• Lateral zone - Cerebrocerebellum
– controls sequencing movements of the muscle. Important for
timing and coordination of movement.
– Plays role in planning and initiating voluntary activity
– Stores procedural memories
Neuronal Organization of the
Cerebellar Cortex
Cerebellar Cortex is organized in three layers
I. Granular layer
–
It is thick inner most layer and contains Granule cells, Golgi type II
cells and other interneurons
II. Purkinje cell layer
–
–
–
It is middle layer
Contains Purkinje cells
Output is always Inhibitory
III. Molecular layer
–
–
It is outermost layer
Contains stellate and basket cells, dendrites of Purkinje and Golgi
type II cells and parallel fibers (axons of granule cells)
Circuit of the Cerebellum
Output of the Cerebellar cortex
• Purkinje cells are the only output of the cerebellar
cortex which goes to Deep cerebellar Nuclei
• Output of the Purkinje cells is always inhibitory. the
neurotransmitter is γ- aminobutyrie acid (GABA)
• Output of the cerebellum regulates rate, range and
direction of movement.
Input to the Cerebellar cortex
• From Mossy fibers originating from brain stem and
spinal cord and
• From Climbing fibers originating from Inferior Olivary
Nucleus in Medulla
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Functions of Brainstem
• The nerve connections of the motor and sensory
systems between the main part of the brain to
the rest of the body pass through the brainstem.
• Has role in Regulation of muscle reflexes involved
with equilibrium and posture
• Control of many stereotyped movements of the
body such as suckling, yawn and stretch, cry and
laugh etc.
• Control of eye movements
Function of brainstem
• Origin of majority (10) of cranial nerves is in Brainstem
• Cranial nerves arising from brain stem
– Mid-brain
– III, IV
– Pons
– V, VI, VII, VIII
– Medulla – IX, X, XI, XII
• The brainstem provides the main motor and sensory
innervation to the face and neck via the cranial nerves.
•
Note only Cranial nerves I (Olfactory) & II (Optic) do not have any origin from
Brainstem
Function of brainstem
• It also regulates the central nervous system, and is
Important in . . .
– Arousal and Activation of cortex,
– Maintaining Consciousness and
– Regulating the Sleep cycle.
• Centers for Cardiovascular, Respiratory, and Digestive
control are located in Brainstem
• Thus basic functions controlled from Brainstem Include …
–
–
–
–
–
Heart Rate & Blood Pressure,
Breathing including Cough & Sneezing
Sleep, wakefulness, Consciousness
Digestive activities including swallowing, vomiting
Posture & Equilibrium
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PINEAL GLAND
• Pineal gland secret melatonin that have rule in
timing
• central role in control of diurnal rhythms while
In Humans, the pineal and melatonin do play
a limited role.
• Recent investigations have demonstrated a
role for melatonin in sleep, tumor reduction
and aging.
• And damage to it cause precocious puberty
THALAMUS
• In general, there are three basic types of thalamic nuclei:
– Relay nuclei
– Association nuclei
– Nonspecific nuclei.
• Relay nuclei receive very well defined inputs and project this
signal to functionally distinct areas of the cerebral cortex.
• The association nuclei receive most of their input from the
cerebral cortex and project back to the cerebral cortex in the
association areas where they appear to regulate activity.
• The nonspecific nuclei include many of the intralaminar and
midline thalamic nuclei that project quite broadly through the
cerebral cortex, may be involved in general functions such as
alerting.
• damage in thalamus cause coma
THALAMUS – Clinical Significance
• Cerebrovascular accident (stroke) can lead to the
Thalamic Syndrome which involves a one-sided
burning or aching sensation often accompanied
by mood swings.
• Damage to the thalamus can result in coma.
• Fatal Familial Insomnia is a hereditary prion
disease in which degeneration of the thalamus
occurs, causing the patient to gradually lose his
ability to sleep and progressing to a state of total
insomnia, which invariably leads to death.
• Korsakoff's Syndrome occurs from damage to the
medial thalamus & mammillary body due to
Thiamine deficiency.
Hypothalamus
• Have set point < diced what is the normal
temperature any change in it will change the
firing > autonomic nerve system < expose to
all everything
• Biological clock
• Hyperpaxia < set point not change
• Fever < set point change
FUNCTIONS OF HYPOTHALAMUS
Biological Functions
1. Controls body temperature
2. Controls thirst and urine output
3. Controls food intake Hunger and Satiety
center
4. Participates in the sleep – wake cycle.
5. Contains the “biological clock” that regulates
certain body functions that vary with time.
FUNCTIONS OF HYPOTHALAMUS
Endocrine Functions
1. Controls anterior pituitary hormone secretion
2. Produces posterior pituitary hormones ADH
and oxytocin
3. Controls uterine contraction and milk ejection
Autonomic Nervous System Function
1. Serves as major ANS coordinating center
FUNCTIONS OF HYPOTHALAMUS
Emotion & Behavior
1. Plays role in emotional responses and
behavioral pattern including rage, fear
pleasure etc.
2. Reward & Punishment center
3. Role in sexual behavior and reproduction
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Limbic system
• Limbic system is motivation
• Emotion > external or internal for benefit or
harmful
Amygdala
• Perform a primary role in the processing of memory,
decision-making, and emotional reactions.
• There are functional differences between the right and left
amygdala and also between Male and Female Amygdala.
• primary role in the formation and storage of memories
associated with emotional events. E.g. Fear Conditioning.
• Also involved in memory consolidation - Formation of Long
Term Memory.
• The amygdala plays a pivotal role in triggering a state of
fear.
• Amygdala is associated with Anxiety and panic attacks.
• Studies link amygdalae to the emotional reactions of PTSD
patients.
• Social behavior
• Stimulating the amygdala appears to increase both sexual
and aggressive behavior.
Hippocampus
• Has important role in formation of new
memory about experienced events (Episodic
Memory).
• Bilateral hippocampal damage results mainly
in Anterograde amnesia and often also
retrograde amnesia
• Believed to have role in spatial memory and
navigation.
Behavior and its Control
• Reward and punishment caused by the Limbic
system are important for behavior.
• Several limbic structures are concerned with sensory
experience – is it pleasant or unpleasant?
• Reward center located in
• the lateral and ventromedial hypothalamus,
• thalamus certain areas,
• Amygdala
• Punishment center located in
•
•
•
•
Hypothalamus
Thalamus
Amygdala and
Hippocampus
Neurotransmitters associated with
limbic system
• Norepinephrine
• Dopamine
• Serotonin
• Many drugs increase dopamine in pleasure
pathways in limbic system, therefore, cause
intense sensation of pleasure e.g. cocaine blocks
re-uptake of dopamine at synapses
• Amphetamine, used in depression, causes
increased release of dopamine from dopamine
secreting neurons
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SPEECH
Speech Centers:
– Broca’s area
• motor speech area
– Wernicke’s area
• sensory speech area. Analyzing hear or written word
• Understanding happen here and right response diced here.
• Both connected by Arcuate Fasciculus.
•
•
Both areas also interact with association areas.
Association area remember the sequence of muscle contraction to pronounce
the word
Broca’s area
• It is located in left frontal lobe just front of the
base of the Primary motor cortex.
• It is for Articulation – Word formation
• Broca’s area contains motor memories — in
particular, memories of the sequences of
muscular movements that are needed to
articulate words.
• Broca's area excites Motor area which controls
the muscles necessary for articulation.
Wernicke’s area
• It is located in the left cortex at Superior gyrus of
Temporal lobe at the juncture of parietal,
temporal and occipital lobes.
• It is concerned with language comprehension
(understanding).
• It plays important role in understanding of both
spoken and written messages.
• Wernicke’s area receives input from visual cortex
in the occipital lobe and also auditory cortex in
temporal lobe.
Not much important but remember is association area
Arcuate Fasciculus
• Is a axon pathway between Wernicke’s area and
Broca’s area
• Higher-Order Association Cortex
• Wernicke’s area has connections with various association
areas in …
• Left Frontal
• Left Temporal
• Left Parietal
• Are involved with mediating between concepts and
language
Lateralization:
• Speech area are located in one sphere (on one
side), usually the dominant hemisphere.
• Left hemisphere is therefore called
DOMINANT SPHERE.
• 90% of left handed people have left cerebral
hemisphere as dominant also.
• Right hemisphere for expression and narrative
selection.
SPEECH DISORDERS
• Thus Damage to the specific regions of brain
can result in selective disturbance of speech.
 Damage to Brocas’s area
 Damage to Wernicke’s area
 Damage to ARCUATE FACICULUS
 Speech Disorders of Articulation
(motor aphasia)
(sensory aphasia)
(Conduction aphasia)
(Dysarthria)
SPEECH DISORDERS
• It results in failure of word formation, but
patient can understand the spoken and
written words.
• Broca’s aphasia is much more than a deficit in
pronouncing words. In general, three major
speech deficits are produced by lesions in and
around Broca’s area: agrammatism, anomia,
and articulation difficulties.
SPEECH DISORDERS
Damage to Wernicke’s area: (sensory aphasia)
• These patients can not understand the words
they hear or see.
• what they say is full of jargon and neologisms
that make little sense.
SPEECH DISORDERS
Anomic aphasia (anomia):
• is a type of aphasia characterized by problems
recalling words, names, and numbers.
Conduction Aphasia:
• Patients may be able to understand speech as
well as produce meaningful speech, but have
difficulty repeating a spoken sentence.
SPEECH DISORDERS
Dyarthria in parkinson
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MEMORY
• Memory trace > change in the synapse in the particle
memory
• Memories are stored in the brain at synapses by changing the
basic sensitivity of synaptic transmission between neurons.
• The neural change at synapses which is responsible for retention
or storage of knowledge is known as memory trace.
• Once memory trace are established, they can be activated by
thinking mind to reproduce memory.
• Memory traces occur at many regions of brain at cortical and
subcortical regions.
• Important areas associated with memory are:
•
•
•
•
•
•
•
cerebral cortex (motor, sensory, visual & auditory)
prefrontal cortex
hippocampus & medial temporal lobe
Amygdala
limbic system
thalamus
Cerebellum+ basal ganglion > skill and movment
MEMORY - STAGES
MEMORY - TYPES
• Declarative (Explicit) memory:
• Memory of
experiences
factual
knowledge
&
personal
• Semantic Memory:
•
Impersonal facts and everyday knowledge
• Episodic Memory:
•
Personal experiences linked with specific times and places
• Procedural (Implicit) Memory:
• Long-term memories of conditioned responses and
learned skills, e.g., driving
MEMORY – IMP. REGIONS IN BRAIN
Major regions in brain which play role in a
particular type of memory include:
• Short Term Memory –
– Hippocampus, Medial Temporal Lobe
• Long Term Memory –
– Neocortex
• Declarative Or Explicit Memory –
– Hippocampus
• Skill Or Implicit Memory –
– Cerebellum, Basal Ganglia.
• Working Memory –
– Prefrontal Cortex
Note took in lec
• Senile dementia > with old age
• Dementia > memory lose with some
intelligence and personality
• Learning > repeat the circle < that will make
the synapse strong
• Reticular > that keep you awake be
stimulation neural circle and aware of self,
thought and associated with emotion
• Consdilation memory > formation memory for
long time
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Electroencephalogram - EEG
• Based on frequency and amplitude waves of EEG can
be:
– Beta: >14 Hz, activated cortex
– Alpha: 8-13 Hz, quiet, waking state (eyes close)
– Theta: 4-7 Hz, some sleep states
– Delta: < 4 Hz, deep sleep
– Gamma: 30-70
• Deep Sleep
– High synchrony, high EEG amplitude
EEG
Alpha Waves:
• rhythmic, 8-13 Hz
• most common in adults.
• Most marked in the parieto-occipital area.
• Occur with closed eyes , relaxation, wondering
mind.
• Alpha block when you open your eye Also
called Desynchronization
EEG
Beta Waves:
• mostly on temporal and frontal lobe
• Recorded during mental activity, awake
person (eyes open).
EEG
Theta Waves:
• Stage II and Stage III sleep.
• Theta and delta waves are known collectively
as slow waves.
Delta waves:
• Children
• In adult abnormal
• In deep sleep
EEG
• Montage: pattern of 10/20% system of EEG
electrode placement
Sleep
• Sleep is a readily reversible state of reduced awareness
and responsiveness of a person to environment.
• Sleep is an active process, not just the absence of
wakefulness.
• Coma is a state of unconsciousness from which a subject
cannot be aroused
• It consist of two alternating periods of.
– Non-Rapid Eye Movement (NREM) sleep
– Rapid Eye Movement (REM) sleep
• Petimal : spike and dom pattern
Sleep stages
• Classified on the basis of EEG Features
1. NREM Sleep : Slow Wave Sleep
– It Is divided into 4 stages :
– Stage 1 NREM
• when a person is initially falling asleep .
• Characterized by low-amplitude, fast activity (α-waves).
– Stage 2 NREM
• Marked by appearance of Sleep Spindles.
• These are bursts of alpha-like 10-14 z , 50 uV waves .
– Stage 3 NREM
• Lower frequency (mainly theta) ,higher amplitude EEG waves.
– Stage 4 NREM
• Still slower frequency (mainly delta) & higher amplitude waves .
2. REM Sleep : Paradoxical Sleep
– Low-voltage , fast activity (β-waves)
Sleep sages
Non-REM Sleep (NREM): Slow-wave sleep
• 75% of sleep time.
• Further divided into four stages
• this is the deep, restful sleep .
• Decrease in vascular tone.
• Decrease in BP (10-30%)
• Decrease in Resp. rate.
• Decrease in BMR
• Not associated with rapid eye movement.
• EEG: Theta + delta waves.
• Dreams may occur but are not remembered
as they are not consolidated in memory.
Sleep stages
Stage N1: Stage 1 NREM Sleep
• It refers to the transition of the brain from
alpha waves (of Awake state) having a
frequency of 8–13 Hz to theta waves having a
frequency of 4–7 Hz.
• This stage is sometimes referred to as
somnolence or drowsy sleep.
• During N1, the subject loses some muscle
tone and most conscious awareness of the
external environment
• Sudden twitches and jerks, also known as
positive myoclonus, may be associated with
the onset of sleep during N1
Sleep stages
Stage N2: Stage 2 NREM Sleep
• Stage N2 is characterized by sleep spindles
ranging from 11–16 Hz and K-complexes.
• During this stage, muscular activity as
measured by EMG decreases, and conscious
awareness of the external environment
disappears.
• This stage occupies 45–55% of total sleep in
adults.
Sleep disorder **defention
I. Dyssomnias:
– Sleep disorders that are characterized by disturbances in the amount,
quality or timing of sleep.
– E.g.:
•
•
•
•
Insomnia
Hypersomnia
Sleep apnea
Narcolepsy
II. Parasomnias:
– Dysfunctions or episodic events occurring with sleep.
– E.g.:
•
•
•
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Sleep-walking (somnambulism)
Sleep-related enuresis (bedwetting)
Sleep-talking (somniloquy)
Sleep-terrors and nightmares
Sleep Disorders
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The eye
The Fibrous Tunic – Sclera/Cornea:
• Most External Layer of Eyeball
• White, opaque, tough, fibrous tissue covering
majority of the eyeball posteriorly is Sclera.
• The thin transparent anterior continuation is
eye
Internal Chambers and Fluids:
The lens & Suspensory Ligaments divide the eye
I. Anterior segment
– Further divided into
• Anterior chamber – between the cornea and iris
• Posterior chamber – between the iris and lens
– Filled with aqueous humor
II. Posterior segment
– Filled with vitreous humor
*lens can change due to muscle
OPTICS OF VISION
• Accommodation:
– It is the ability to adjust the refractory strength of
lens (curvature of the lens) to focus nearby objects
on retina
OPTICS OF VISION
• Astigmatism – Uneven curvature of Cornea
• Cataract – Decreased transparency of Lens
• Myopia – Better near vision than far vision
– Due to either the eyeball is too long or lens too strong
– Corrected by Concave lens
• Hyperopia – Better far vision than near vision
– Due to either the eyeball is too short or lens too weak
– Corrected by Convex lens
RETINA-FUNDOSCOPY
• Major function of eye is to focus light on Rods &
Cones of retina.
• Macula lutea – contains mostly cones
• Fovea centralis – contains only cones
– Region of highest visual acuity
• Optic disc – blind spot
• Retina receives blood from two sources
– Outer third of the retina – supplied by capillaries in
the choroid
– Inner two-thirds of the retina – supplied by central
artery and vein of the retina
– Outer most : photo reseptor
– Inner most: nerve and red and cons, nuclular
RETINAL LAYERS
RETINA
Major types of neurons/cells in retina:
I. Photoreceptors – Rods & Cones
II. Bipolar Cells
 Connect Photoreceptor cells with Ganglion cells
III. Horizontal cells
 Interconnect Photoreceptor cells
IV. Amacrine cells
 Interconnect Ganglion cells & also to Bipolar cells
V. Ganglion cells
 Are only output of retina, axons form optic nerve.
PHOTORECEPTORS
• Photopigment in Rods is called as Rhodopsin
• And cons called photospin
PHOTOTRANSDUCTION
• It is the process of converting light
stimuli into electrical signals.
• Rods and Cones on stimulation by
light respond by Hyperpolarization.
• Steps:
– The only light dependent step in entire process of
phototransduction is conversion of 11-cis retinal to all-trans
retinal on light exposure  This causes opsin activation 
activates transducin  activates Phosphodiesterase 
decreases cGMP which were keeping the Na leak channels
open in outer segments of Rods  Na channels close and
hyperpolarization occurs  decrease in secretion of
Glutamate by rods at synapse with bipolar cells.
– Further processing occur in subsequent layers of Retina
PROCESSING IN RETINA
• Axons of Ganglion cells form the optic nerve which
transmit information to brain as Action Potentials.
VISUAL PATHWAY
• Axons of ganglion cells exit eye as the optic nerve
• Fibers from the Nasal halves of Retina cross to opposte
side in the Optic Chiasma while the fibers from the
temporal side of retina do not cross.
• Thus together Nasal side fibers of opposite side and
Temporal side fibers of same side continue as Optic
Tract
• Optic tracts terminates in Lateral geniculate nucleus
(LGB) of the thalamus.
• From the LGB Fibers of the optic radiation reach the
primary visual cortex
Note took in lec
•
•
•
•
•
•
•
Analysis start at retina
sclera and cornea : visible
Choroid: cillary body and iris all called uvea
Choroid: blood vessels
Cillary: cillary muscle
Retina : 10 layers , there’s ant and post champers
Presbyopia : decrease in accommodation in old
age
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VISUAL PATHWAY
Branches at Subcortical level:
• Branch to midbrain
• Superior colliculi
• Pretectal nuclei
• Branch to SCN
(suprachiasmatic nucleus)
VISUAL PATHWAY LESIONS
A. Unilateral Blindness
B. Bitemporal Hemianopia
C. Homonymous Hemianopia
D. Homonymous Hemianopia
with Macular Sparing
LATERAL GENICULATE BODY
• The magnocellular pathway, from layers 1 and
2, carries signals for detection of movement,
depth, and flicker.
• The parvocellular pathway, from layers 3–6,
carries signals for color vision, texture, shape,
and fine detail.
VISUAL CORTEX
• Columns for Color are called BLOBS.
• Every type of visual info is processed
simultaneously by the vertical and horizontal
cortical systems.
COLOR VISION
Examples of Color
Perception:
• %Cone Stimulation:
R G B
Blue
0 0 100
yellow 83 83 0
• The extent to which each of the cone types is excited is coded and
transmitted in separate parallel pathways to the brain.
• These pathways project to the ‘color’ blobs and the deep portion of
layer 4C of V1 cortex.
• Distinct color vision center in the visual cortex combines and
processes these inputs to generate the perception of color.
• ^^ not important
COLOR BLINDNESS
Ishehara Chart
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sound
• Sound that is perceptible by humans has frequencies
from about 20 Hz to 20,000 Hz.
• Impedance : resistance
• Impedance: matching intensity of sounds
• Amplitude: 10 micro sec
Sound Transmission
External Ear:
• Air transmitted sound waves are directed
toward the Tympanic Membrane
• Functions of External Air:
– Sound collection
– Increasing pressure on the tympanic membrane in a
frequency sensitive way.
– Sound localization
• Function of middle ear:
• Trans sound from external to internal
– Maintains resting air pressure on both sides of TM equal
– Transfers movements of the tympanic membrane to the
inner ear
– Impedance matching
– Attenuation
• Protect ear from large sounds
Attenuation Reflex
• Function:
– To protect the cochlea from damaging vibrations caused
by excessive sound
– To mask background noise in loud environments.
Sound Transmission
Inner Ear:
• Motion along the basilar membrane excites frequency
specific areas of the Organ of Corti, which in turn
stimulates a series of nerve endings.
• Basilar membrane have apex and base
• Apex: low frequency, Base: high frequency
• Organ of hearing is corti body
• Receptor of hearing : hair cell
• Hair cell is 2 A-inner: actual receptor of hearing
• B-outer: increase or decrease sensitivity of hearing
Place Principle
• The method used by nervous system to detect
different sound frequencies is to determine
the position along the basilar membrane that
are most stimulated. This is called the “place
principle
Different between them
• Fluid in perlymph : no cell
• Endolymph : rich in K+
• Specialty of basilar membrane ?
• For frequency
Function of Inner & Outer Hair cells
• Inner Hair Cells:
• They transform the mechanical forces of
sound into electrical impulses.
• Outer Hair cell:
• Increases the sensitivity of inner hair cells for
different frequency and intensity.
• Hair cell generate action potinal > transmit it
by cerebral ganglion > then to superior olivary
from opposite side > to inferior coccli in
medbrain > MGN > auditory cortex in
temporal
• Tonotopic map : different frequency
Sound Ananlysis
Perceiving Pitch (Frequency):
• location of vibration on the basilar membrane
Appreciation Of Loudness Of Sound: by ampitude
If increase in action potinal increase in loudness
• Intensity or loudness of sound correlates with two
factors:
1. Rate of discharge from the individual fibers of auditory nerve
2. Total number of nerve fibers discharging.
Pathophysiology of hearing
•
Conduction deafness
–
–
•
That caused by impairment of the physical
structures of the ear that conduct sound to cochlea
like outer ear and middle ear.
Ex: wax, osteosclrosis
Sensorineural deafness
–
–
–
It is the deafness caused from impairment of the
Hair cells, auditory nerve etc.
Ex: presbyacusis < old age “ damage in higher
frequency fiber”
Meneres disease
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Taste (Gustation)
• Taste receptors have life span of about 10 days
Anatomy of Taste Buds.
• 10,000 taste buds found on tongue, soft palate & pharynx
• Taste buds consist of:
– ~50 receptor cells
– Basal cells
cells
(type 3)
(type 1 &2)
surrounded by supporting cells
develop into supporting cells then receptor
• Gustatory hairs project through the taste pore
• Life span of 10 days
Taste
– Salty
• Stimulated by chemical salts, especially NaCl
– Sour
• Caused by acids which contain a free hydrogen ion, H+
Sensation of Taste
Discrimination of intensity of
taste:
Discrimination in intensity of taste:
– Poor (like smell)
– Requires 30% change to allow
discrimination of intensity
Clinical considerations
•
•
•
•
Ageusia: Absence of sense of taste
Dysgeusia: Disturbed sense of taste
Hypogeusia: Diminshed sense of taste
Hypergeusia: increased sense of taste
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Smell (Olfaction)
Olfactory mucosa contains 3 cell types
• Olfactory receptor cell
• Supporting cells
– Secrete mucus
• Basal cells
– Precursors of new olfactory receptor cells
(replaced about every two months)
Physiology of Olfaction
only important in red
• Odorant binds to the receptor of an olfactory
hair→ G-protein activation→ activation of
adenylate cyclase→ production of cAMP→
opening of Na+ channels→ inflow of Na+
→generator potential→ nerve impulse
through olfactory nerves→ olfactory bulbs→
olfactory tract→ primary olfactory area of the
cerebral cortex.
Olfactory pathway
• Fibers originating in olfactory bulb travel in
two different routes
– Subcortical route, to limbic system – close
coordination between smell and behavioral
reactions, associated with eating , etc.
– Route to primary olfactory cortex (piriform cortex)
Abnormalities
Anosmia (absence of sense of smell),
Hyposmia (diminished olfactory sensitivity)
dysosmia (distorted sense of smell)
Several dozens different anosmias have been
detected in humans. They are presumably due
to absence or disrupted functions of one of the
many members of odorant receptor family