FISIOLOGI REFLEX Textbooks Guyton AC amp Hall JE 2006 Textbook of Medical Physiology The 11 th edition Philadelphia ElsevierSaunders 945960 749760 Brooks GA amp Fahey TD 1985 ID: 774999
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Slide1
Dr. Bernhard Arianto Purba, M.Kes., AIFO
FISIOLOGI REFLEX
Slide2Textbooks
Guyton, A.C & Hall, J.E. 2006.
Textbook of Medical Physiology
. The 11
th
edition. Philadelphia:
Elsevier-Saunders: 945-960, 749-760.
Brooks, G.A. & Fahey, T.D. 1985.
Exercise Physiology
. Human Bioenergetics and Sts
Aplications
. New York : Mac
Millan
Publishing
Company: 122-143.
Foss, M.L. & Keteyian, S.J. 1998.
Fox’s Physiological Basis for Exercise and Sport
. 4th ed. New York : W.B. Saunders
Company: 471-491.
Astrand
, P.O. and
Rodahl
, K. 1986.
Textbook of Work
Pysiology
, Physiological Bases of Exercise. New York : McGraw—Hill
.
Ganong, M. Wiliiam. 2003.
Review of Medical Physiology
. The 21st edition. USA:
McGraw—Hill
Companies.
Slide3Reacting to Changes
You need to keep the conditions inside your body constant. Doing this is called homeostasis. Small changes inside your body can cause its cells to be damaged or destroyed. Yet, there are big changes going on outside your body.
You need to detect a change in the environment (a
stimulus) and react to the change (a response) in a way that maintains homeostasis. When you do this without thinking, it is called a reflex.
Slide4Reacting to Changes
It can get very hot or very cold outside, but the temperature inside your body stays the same. How?
When it gets cold outside (stimulus) you shiver (response) and keep the temperature inside your body from dropping.
When it gets hot outside (stimulus) you perspire (response) and keep the temperature inside your body from rising.
Slide5Posture
In order to maintain your posture (even bad posture - stop slouching) your muscles are constantly monitoring their shape. A change in shape of a muscle (the stimulus) causes the muscle to readjust its shape (the response) and maintain your posture.
The knee-jerk reflex is base on the hammer changing the shape of a muscle.
Slide6Revisiting the Knee-Jerk Response
What is the stimulus?
The hammer hits the tendon.
The muscle contracts, causing the foot to jerk upward.
What is the response
?
Slide7Other Reflexes
Stimulus
Response
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
Slide8Simplified Design of the Nervous System
Sensory neurons – located dorsally
Cell bodies outside the CNS in sensory ganglia
Central processes enter dorsal aspect of the spinal cord
Motor neurons – located ventrally
Axons exit the ventral aspect of the spinal cord
Interneurons – located centrally
Provide communication between sensory and motor neurons and between levels of the CNS
Slide9Example of Neuronal Organization: Reflexes
Reflex arcs – simple neural pathways
Responsible for
reflexes
Rapid, autonomic motor responses
Can be visceral or somatic
Slide10Five Essential Components to the Reflex Arc
Receptor – detects the stimulus
Afferent (sensory neuron) – transmits impulses to the CNS
Integration center – consists of one or more synapses in the CNS
Efferent (motor neuron) – conducts impulses from integration center to an effector
Effector – muscle or gland cell
Responds to efferent impulses
Contraction or secretion
Slide11The reflex arc
An automatic, rapid response to an adverse stimulus.
Action is involuntary the brain is not involved in the event but may be informed of it
Many reflex actions are protective
Some complex actions (swallowing, coughing and blinking) are coordinated by reflexes.
Slide12A simplified reflex arc
stimulus
Slide13A simplified reflex arc
stimulus
receptor
Slide14A simplified reflex arc
stimulus
receptor
sensory neurone
Slide15A simplified reflex arc
stimulus
receptor
sensory neurone
spinal cord of central nervous system
Slide16A simplified reflex arc
stimulus
receptor
sensory neurone
spinal cord of central nervous system
relay neurone
Slide17A simplified reflex arc
stimulus
receptor
sensory neurone
spinal cord of central nervous system
relay neurone
motor neurone
Slide18A simplified reflex arc
stimulus
receptor
sensory neurone
spinal cord of central nervous system
relay neurone
motor neurone
effector
Slide19A simplified reflex arc
stimulus
receptor
sensory neurone
spinal cord of central nervous system
relay neurone
motor neurone
effector
response
Slide20Example of the Five Components to the Reflex Arc
Slide21Slide22Classification of Reflexes
By development Innate, acquiredWhere information is processedSpinal, cranialMotor responseSomatic, visceralComplexity of neural circuitMonosynaptic, polysynaptic
Slide23Reflex Classification
Monosynaptic or polysynaptic
Spinal or cranial
Somatic or autonomic
Innate or learned
Slide24Types of Reflexes: Number of Classes
Monosynaptic reflex – simplest of all reflexes
Just one synapse
The fastest of all reflexes
Example – knee-jerk reflex
Polysynaptic reflex – more common type of reflex
Most have a single interneuron between the sensory and motor neuron
Example – withdrawal reflexes
Slide25Monosynaptic Reflex
Slide2626
Monosynaptic reflex
1 synapse
b
c
e
d
g
Slide27How many neurons make up a monosynaptic reflex arc?a. 1 b. 2 c. 3 d. 4 or more
27
Neuron #1
Neuron #2
Slide28Polysynaptic Reflex
Slide2929
Polysynaptic reflex
2 synapses
b
c
e
d
Slide30A withdrawal reflex
Slide31A withdrawal reflex
The
stimulus
is the heat from the hot object
Slide32A withdrawal reflex
The
stimulus is the heat from the hot object
The stimulus is detected by
receptors
in the dermis of the skin. Since these sensory cells respond to temperature, they are called thermoreceptors.
Slide33A withdrawal reflex
The
stimulus is the heat from the hot object
The stimulus is detected by receptors in the dermis of the skin. Since these sensory cells respond to temperature they are called thermoreceptors.
The thermoreceptors initiate nerve impulses that pass to the spinal cord along a
sensory neurone
.
Slide34A withdrawal reflex
The
stimulus is the heat from the hot object
The stimulus is detected by receptors in the dermis of the skin. Since these sensory cells respond to temperature they are called thermoreceptors.
The thermoreceptors initiate nerve impulses that pass to the spinal cord along a sensory neurone.
sensory neurone cell body
Slide35A withdrawal reflex
The
stimulus is the heat from the hot object
The stimulus is detected by receptors in the dermis of the skin. Since these sensory cells respond to temperature they are called thermoreceptors.
The thermoreceptors initiate nerve impulses that pass to the spinal cord along a sensory neurone.
sensory neurone cell body
grey matter (neurone cell bodies)
Slide36A withdrawal reflex
The
stimulus is the heat from the hot object
The stimulus is detected by receptors in the dermis of the skin. Since these sensory cells respond to temperature they are called thermoreceptors.
The thermoreceptors initiate nerve impulses that pass to the spinal cord along a sensory neurone.
sensory neurone cell body
grey matter (neurone cell bodies)
spinal cord
Slide37A withdrawal reflex
The
stimulus is the heat from the hot object
The stimulus is detected by receptors in the dermis of the skin. Since these sensory cells respond to temperature they are called thermoreceptors.
The thermoreceptors initiate nerve impulses that pass to the spinal cord along a sensory neurone.
sensory neurone cell body
grey matter (neurone cell bodies)
spinal cord
white matter (neurone axons)
Slide38A withdrawal reflex
The
stimulus is the heat from the hot object
The stimulus is detected by receptors in the dermis of the skin. Since these sensory cells respond to temperature they are called thermoreceptors.
The thermoreceptors initiate nerve impulses that pass to the spinal cord along a sensory neurone.
sensory neurone cell body
grey matter (neurone cell bodies)
spinal cord
white matter (neurone axons)
The sensory neurone enters the spinal cord via the dorsal branch of the spinal nerve and forms a synapse with a
relay neurone
, inside the grey matter
Slide39A withdrawal reflex
The
stimulus is the heat from the hot object
The stimulus is detected by receptors in the dermis of the skin. Since these sensory cells respond to temperature they are called thermoreceptors.
The thermoreceptors initiate nerve impulses that pass to the spinal cord along a sensory neurone.
sensory neurone cell body
grey matter (neurone cell bodies)
spinal cord
white matter (neurone axons)
The sensory neurone enters the spinal cord via the dorsal branch of the spinal nerve and forms a synapse with a relay neurone, inside the grey matter
The short relay neurone forms a synapse with a
motor neurone
that leaves the spinal cord via the ventral root of the spinal cord.
Slide40A withdrawal reflex
The
stimulus is the heat from the hot object
The stimulus is detected by receptors in the dermis of the skin. Since these sensory cells respond to temperature they are called thermoreceptors.
The thermoreceptors initiate nerve impulses that pass to the spinal cord along a sensory neurone.
sensory neurone cell body
grey matter (neurone cell bodies)
spinal cord
white matter (neurone axons)
The sensory neurone enters the spinal cord via the dorsal branch of the spinal nerve and forms a synapse with a relay neurone, inside the grey matter
The short relay neurone forms a synapse with a motor neurone that leaves the spinal cord via the ventral root of the spinal cord.
The motor neurone carries the impulse to an
effector
, in this case muscles in the arm, which contract to withdraw the hand from the hot object. This action is known as the
response
.
Slide41A withdrawal reflex
The
stimulus is the heat from the hot object
The stimulus is detected by receptors in the dermis of the skin. Since these sensory cells respond to temperature they are called thermoreceptors.
The thermoreceptors initiate nerve impulses that pass to the spinal cord along a sensory neurone.
sensory neurone cell body
grey matter (neurone cell bodies)
spinal cord
white matter (neurone axons)
The sensory neurone enters the spinal cord via the dorsal branch of the spinal nerve and forms a synapse with a relay neurone, inside the grey matter
The short relay neurone forms a synapse with a motor neurone that leaves the spinal cord via the ventral root of the spinal cord.
The motor neurone carries the impulse to an
effector
, in this case muscles in the arm, which contract to withdraw the hand from the hot object. This action is known as the
response
.
Slide42Flexor and Crossed Extensor Reflexes
The flexor reflex is initiated by a painful stimulus (actual or perceived) that causes automatic withdrawal of the threatened body part
The crossed extensor reflex has two parts
The stimulated side is withdrawn
The contralateral side is extended
Slide43Crossed Extensor Reflex
Slide44-Postural reflexes - maintain upright positione.g flexor (withdrawl) reflex - polysynapticsensory input -> interneuron -> motor neuron which contracts muscles and pulls limb awayPLUS synapses with motor neurons in adjacent SC segments -> contracts muscleknown as an intersegmental reflex arcIN ADDITION - the sensory input can cross to the other side of the SC (via the gray commisure) where it synapses with and interneuron and motor neuron to contract the antagonistic muscle group and maintains balance
withdrawl
crossed
extensor
Slide451
Withdrawal of right leg
(flexor reflex)
Stepping on a tack
stimulates SENSORY
RECEPTOR (dendrites ofpain-sensitive neuron) inright foot
1
SENSORY
NEURON
excited
Withdrawal of right leg
(flexor reflex)
Stepping on a tack
stimulates SENSORYRECEPTOR (dendrites ofpain-sensitive neuron) inright foot
2
+
1
+
Ascending
interneurons
SENSORY
NEURON
excited
Spinal
nerve
Within INTEGRATING CENTER
(spinal cord), sensory neuron
activates several interneurons
Descending
interneurons
Withdrawal of right leg
(flexor reflex)
Stepping on a tack
stimulates SENSORY
RECEPTOR (dendrites ofpain-sensitive neuron) inright foot
+
+
+
2
3
+
+
+
+
+
+
+
Interneuronsfrom other side
1
+
Ascending
interneurons
SENSORY
NEURON
excited
Spinal
nerve
Within INTEGRATING CENTER
(spinal cord), sensory neuron
activates several interneurons
MOTOR
NEURONS
excited
Descending
interneurons
Withdrawal of right leg
(flexor reflex)
Stepping on a tackstimulates SENSORYRECEPTOR (dendrites ofpain-sensitive neuron) inright foot
Extension of left leg(crossed extensor reflex)
MOTORNEURONSexcited
+
+
+
2
3
4
4
+
+
+
+
+
+
+
+
+
+
Interneurons
from other side
1
+
Ascending
interneurons
EFFECTORS
(extensor muscles)
contract, and extend
left
leg
SENSORY
NEURON
excited
Spinal
nerve
Within INTEGRATING CENTER
(spinal cord), sensory neuron
activates several interneurons
MOTOR
NEURONS
excited
Descending
interneurons
Withdrawal of right leg(flexor reflex)
Flexor musclescontract and with-drawright leg
Stepping on a tackstimulates SENSORYRECEPTOR (dendrites ofpain-sensitive neuron) inright foot
Extension of left leg(crossed extensor reflex)
MOTORNEURONSexcited
+
+
+
2
3
4
4
5
+
+
+
+
+
+
+
+
+
+
Interneurons
from other side
+
+
+
Slide46A few reminders!
The central
grey matter
contains the cell bodies of relay and motor neurones.
The outer
white matter
contains
myelinated
axons, which run up and down the spinal cord to and from the brain.
In the centre of the grey matter is the
spinal canal
, through which the nutritive
cerebrospinal fluid
cir
c
ulates
.
Slide47A few reminders!
Sensory neurones enter the spinal cord through the dorsal root and the concentration of their cell bodies forms a swelling called the
dorsal root ganglion
.
Motor neurones leave the spinal cord via the ventral root.
Slide48SPINAL CORD
general characteristics
length - 45 cm (18 in)
maximum width - 14 mm (0.55 in)
enlargements
cervical - C
4
to T
1
lumbar - T
9
to T
12
Slide49Gross Anatomy of Lower Spinal Cord
Slide50SPINAL CORD
general characteristics
conus medullaris
or
medullary cone
- 1st or 2nd lumbar
terminal filum
inferior tip of conus medullaris to 2nd sacral vertebra
cauda equina
appearance of horse’s tail from L
2
to S
5
Slide51SPINAL CORD - MENINGES
a. dura mater
continuous with dura mater of brain
between dura mater and wall of vertebral column is epidural space
filled with areolar connective tissue and blood vessels
b. arachnoid
subdural and subarachnoid spaces
Slide52Meninges
of Vertebra and Spinal Cord
Slide53SPINAL CORD - MENINGES
c. pia mater
adheres to surface of spinal cord and brain
contains rich amount of blood vessels
spinal cord is suspended in middle of dural sheath
suspended by extensions of pia mater called
denticulate ligaments
protects cord against shock and sudden displacement
Slide54Slide55SPINAL CORD - COMPOSITION
gray and white matter is reversed from brain
H of gray matter
gray commissure
central canal
posterior or dorsal horns
anterior or ventral horns
lateral horns (thoracic and lumbar regions)
dorsal root
ventral root
Slide56Slide57Gray Matter in the Spinal Cord
Pair of dorsal or posterior hornsdorsal root of spinal nerve is totally sensory fibersPair of ventral or anterior hornsventral root of spinal nerve is totally motor fibersConnected by gray commissure punctured by a central canal continuous above with 4th ventricle
Slide58White Matter in the Spinal Cord
White column = bundles of myelinated axons that carry signals up and down to and from brainstem3 pairs of columns or funiculidorsal, lateral, and anterior columnsEach column is filled with named tracts or fasciculi (fibers with a similar origin, destination and function)
Slide59Spinal Tracts
Ascending and descending tract head up or down while decussation means that the fibers cross sidesContralateral means origin and destination are on opposite sides while ipsilateral means on same side
Slide60Dorsal Column Ascending Pathway
Deep touch, visceral pain, vibration, and proprioceptionFasciculus gracilis and cuneatus carry signals from arm and leg Decussation of 2nd order neuron in medulla3rd order neuron in thalamus carries signal to cerebral cortex
13-60
Slide61Spinothalamic Pathway
Pain, pressure, temperature, light touch, tickle and itchDecussation of the second order neuron occurs in spinal cordThird order neurons arise in thalamus and continue to cerebral cortex
Slide62Spinoreticular Tract
Pain signals from tissue injury
Decussate in spinal cord and ascend with spinothalamic fibers
End in reticular formation (medulla and pons)
3
rd
and 4
th
order neurons continue to thalamus and cerebral cortex
Slide63Spinocerebellar Pathway
Proprioceptive signals from limbs and trunk travel up to the cerebellum
Second order nerves ascend in ipsilateral lateral column
Slide64Descending Motor Tracts
Tectospinal tract (tectum of midbrain)
reflex turning of head in response to sights and sounds
Reticulospinal tract (reticular formation)
controls limb movements important to maintain posture and balance
Vestibulospinal tract (brainstem nuclei)
postural muscle activity in response to inner ear signals
Slide65Corticospinal Tract
Precise, coordinated limb movementsTwo neuron pathwayupper motor neuron in cerebral cortexlower motor neuron in spinal cordDecussation in medulla
Slide66Spinal vs Cranial Reflexes
Spinal = spinal cord integration center
Ex. Knee-jerk reflex
Cranial = brain as integration center
Ex. Pupillary light reflex
Slide67Spinal & Cranial Reflex
Spinal reflex: spinal cord; Cranial reflex: brainInborn, stereotyped, rapid, automaticUnconscious & involuntary (not involve cerebrum)Cannot prevent nor modifyInstinctive behaviour & immediate protection
Slide68Table 14-9 (1 of 2)
Summary: Cranial Nerves
Slide69Table 14-9 (2 of 2)
Summary: Cranial Nerves
Slide70Cranial Reflexes
Monosynaptic and polysynaptic reflex arcs
Involve sensory and motor fibers of cranial nerves
Clinically useful to check cranial nervous system
Slide71Table 14-10
Examples of Cranial Reflexes
Slide72Muscle Sense Organs
Pain
exercising too vigorously (muscle
soarness
)
Proprioceptors
conduct sensory reports to CNS from:
muscles
tendons
ligaments
joints
Kinethesis
: unconsciously tells us where our body parts are in relation to our environment
Execute a smooth and coordinated movement
Maintain a normal body posture and muscle tonus
Slide73Muscle spindleIn musclesSense stretchGolgi tendon organNear tendonSense forceJoint receptorsSense pressurePosition
Types of Skeletal Muscle Reflex
Sensory Receptors: the Proprioceptors
Slide74Three muscle sense organs concerned with kinesthesis
Muscle spindles (stretch receptors) send information to the CNS concerning the degree of stretch of the muscle in which they are embedded.
Provide info: exact number motor units needed to contract to overcome a given
resistence
Control posture (with gamma system): in voluntary movements
Sensitive to length or stretch
Stretch reflexes initiated by muscle spindles must maintain healthy muscle tone
Golgi tendon organs
Joint receptors
Slide75Muscle Spindles
Are composed of 3-10
intrafusal
muscle fibers that lack
myofilaments
in their central regions, are
noncontractile
, and serve as receptive surfaces
but the two ends contain contractile fibers
Muscle spindles are wrapped with two types of afferent endings: primary sensory endings of type
Ia
fibers and secondary sensory endings of type II fibers
These regions are innervated by gamma (
) efferent
fibers (
fusimotor
nerves)
arise from ventral horn and maintain spindle sensitivity
Note
: contractile muscle fibers are
extrafusal
fibers and are innervated by alpha (
) efferent
fibers (alpha motor nerves)
Stimulate
extrafusal
muscle fibers to contract
Slide76Muscle Spindles
Slide77Operation of the Muscle Spindles
Spindle fibers lie parallel to the regular fibers
Stretching
the muscles activates the muscle
spindle (the center portion of the spindle is also stretch)
There is an increased rate of action potential in
Ia
fibers
Contracting the muscle reduces tension on the muscle spindle
There is a decreased rate of action potential on
Ia
fibers
Slide78Operation of the Muscle Spindles
Slide79Slide80Stretch Reflex
Stretching the muscle activates the muscle spindle
Excited
motor neurons of the spindle cause the stretched muscle to contract
Afferent impulses from the spindle result in inhibition of the antagonist
Example: patellar reflex
Tapping the patellar tendon stretches the quadriceps and starts the reflex action
The quadriceps contract and the antagonistic hamstrings relax
Slide81Stretch Reflex
Slide821
Stretching stimulates
SENSORY RECEPTOR
(muscle spindle)
Antagonistic
muscles relax
1
Stretching stimulates
SENSORY RECEPTOR
(muscle spindle)
SENSORY
NEURON
excited
To brain
SpinalNerve
+
+
2
1
Stretching stimulates
SENSORY RECEPTOR
(muscle spindle)
SENSORY
NEURON
excited
Within INTEGRATING
CENTER (spinal cord),sensory neuron activatesmotor neuron
Inhibitoryinterneuron
To brain
SpinalNerve
+
–
+
2
3
1
Stretching stimulates
SENSORY RECEPTOR
(muscle spindle)
SENSORY
NEURON
excited
MOTOR
NEURON
excited
Antagonistic
muscles relax
Motor neuron to
antagonistic musclesis inhibited
Within INTEGRATINGCENTER (spinal cord),sensory neuron activatesmotor neuron
Inhibitoryinterneuron
To brain
SpinalNerve
+
–
+
+
2
3
4
1
Stretching stimulates
SENSORY RECEPTOR
(muscle spindle)
SENSORY
NEURON
excited
MOTOR
NEURON
excited
EFFECTOR
(same muscle)
contracts and
relieves thestretching
Antagonisticmuscles relax
Motor neuron toantagonistic musclesis inhibited
Within INTEGRATINGCENTER (spinal cord),sensory neuron activatesmotor neuron
Inhibitoryinterneuron
To brain
SpinalNerve
+
–
+
+
2
3
4
5
Slide83How is the Hammer Tap Detected?
The muscles in your leg have stretch receptors. They react to a change in length of the muscle. When the hammer hits the tendon at the knee, it makes a muscle in the front of your thigh longer (stretches it). That stimulates the stretch receptors in that muscle.
Slide84The Knee-Jerk Response
When the stretch receptors are stimulated, they send a message to the muscles of your thigh.
The muscles in the front of your thigh contract.
The muscles in the back of your thigh relax.
Your foot jerks.
Slide85After stretching an intrafusal muscle fiber, the next event isa. an increase in action potentials along the associated sensory neuron.b. a decrease in muscle tension. c. a decrease in muscle tone.d. decreased sensitivity to stretching.e. an increase in action potentials along the associated alpha motoneuron.
Slide86Response characteristics of the stretch receptor—another example of
frequency coding
.
Slide87The normal, contractile fibers of skeletal muscle are called _____ fibers.a. intrafusal b. extrafusal c. alpha d. stretched
Slide88Which statement is true about muscle spindles?a. They are found in smooth muscle b. They do not contain muscle fibers.c. They help prevent muscle damage that would result from overstretching d. They are regulated by alpha motoneurons.
Slide89Change in Muscle Length
Here is a similar reflex in the arm, showing muscle length.
The weight dropping into the hand is the stimulus. Like the hammer tapping the knee, it stretches a muscle.
The response is the muscle contracting, jerking the arm up.
Tonic stretch
Concerned with the final length of muscle fibers
If the load is light, the stretch moderate
Slide90a Motor neurons Ia sensory Interneurons
Phasic stretch
The spindle is responding to the rate or velocity of the change in length
Unexpected increase in the load being held the muscle stretch and forearm will be lowered
Overcompensation: the contraction will be greater than needed
Slide91Muscle Spindle Reflex
Phasic
stretch
The spindle is responding to the rate or velocity of the change in length
Unexpected increase in the load being held the muscle stretch and forearm will be lowered
Overcompensation: the contraction will be greater than needed
Slide92The Gamma System
Gamma neurons can be stimulated directly by motors centers on cerebral cortex (self activated): gamma system/ gamma loop
When stimulated
ends spindle contract stretching the center portion stimulating the sensory nerve
For the execution of smooth and voluntary movements
Gamma neurons have recruitment the same as alpha motor neurons
This
combined stimulation of the alpha and gamma efferent neurons sets up a situation in which there will automatically be an increase in tension of the muscle if the load is too heavy. This combined stimulation of the two neuron types is called
alpha-gamma co-activation
.
Slide93Motor neuron to muscle relations
alpha-gamma co-activation
Slide94Motor neuron to muscle relations
Slide95Slide96Slide97Golgi Tendon Reflex
Golgi tendon organs are
proprioceptors
encapsulated in tendon fibers (
musculotendinous
junction)
The
opposite of the stretch reflex
Contracting the muscle activates the Golgi tendon organs
therefore sensitive to stretch but require a strong stretch
Afferent Golgi tendon neurons are stimulated, neurons inhibit the contracting muscle, and the antagonistic muscle is
activated
This can be interpreted as a protective function during lifting extremely heavy loads that could cause injury
As a result, the contracting muscle relaxes and the antagonist contracts
Slide98Golgi Tendon Reflex
Slide99Force pulls collagen fibers which squeeze sensorsOverload causes inhibition of contraction
Golgi Tendon Reflex: Response to Excessive Force
This is a disynaptic inhibitory reflex arc!
Slide100Inhibition
of alpha neuron
Slide101Golgi Tendon Reflex
Slide102The receptor located at the junction of tendons and skeletal muscle fibers is thea. muscle spindle. b. Golgi tendon organ c. neither d. both
Slide103Joint Receptors
Found in tendons, ligaments,
periosteum
, muscle, and joint capsules
Supply info to CNS concerning the joint angle, the acceleration of the joint, and the degree of deformation brought about by pressure
The names of some of the joint receptors are the end bulbs of
krause
, the
pacinian
corpuscles, and
ruffini
end organs
+ other receptors (e.g., sight, touch, and sound) is used to give us a sense of awareness of body and limb position, as well as to provide us with automatic reflexes concerned with posture
Slide104Somatic vs Autonomic Reflexes
Somatic = motor neurons to skeletal muscles
Ex. Knee-jerk reflex
Autonomic = autonomic neurons to smooth muscle and glands
Ex.
Pupillary
light reflex
Slide105Autonomic Reflexes (visceral reflex0
May be spinal (e.g., urination and defecation) or modified by higher brain structures.The thalamus, hypothalamus and brain stem are in charge of multiple reflexes – HR, BP, breathing, eating, osmotic balance, temperature, vomiting, gagging, sneezing.All are polysynaptic.
Slide10616-106
Autonomic Reflexes
Slide10716-107
Influence of Brain on Autonomic Functions
Slide108Slide109Autonomic Reflex Arc
Slide110Slide111Disorders of the Autonomic Nervous System: Raynaud’s Disease
Raynaud’s disease – characterized by constriction of blood vesselsProvoked by exposure to cold or by emotional stress
Slide112Disorders of the Autonomic Nervous System: Hypertension
Hypertension – high blood pressureCan result from overactive sympathetic vasoconstriction
Slide113Disorders of the Autonomic Nervous System: Achalasia of the Cardia
Achalasia of the cardia Defect in the autonomic innervation of the esophagus
Slide114Slide115Innate vs Learned Reflexes
Innate = born-withKnee-jerk reflex, pupillary reflexLearned = develops based on experiencesPavlov’s dogs salivation in response to bell
Ivan Pavlov (1849 – 1936), a Russian physiologist, developed the technique of Classical Conditioning
Slide116Conditional Reflex
Acquired
(not inherited) through
training
or
learning
.
Replace a normal stimulus by a
unrelated
stimulus to give same response
.
Initial skills by voluntary; then become unconscious (conditional reflex)
Enable animal to
modify behaviour
to adapt the environment (i.e.
avoid danger
)
Slide117117
Conditioned Reflex in Dog
Slide118salivation to meat powder is an unconditional reflexan inborn reflex – not learnedFood – unconditioned stimulus (US)Salivation – unconditioned response (UR)Bell (neutral stimulus) –conditioned stimulus (CS)Salvation to bell – conditioned response (CR)
If a flavor is followed by an illness experience, we will not consume the flavor in the futureCS + UCS ----------> UCRTaste Toxic event Nausea CS -----> CRFlavor Nausea
Applications of conditioning
phobias
less serve fear responses
Systematic
desensitisation
Pleasant emotional responses
Slide119Slide120Clinical Reflex Classification
Superficial reflex ( Cutis / mucosa )Deep Tendon reflex( Myotatic )Visceral reflex ( Organic )Pathologic Reflex ( Abnormal )
Classification according to its center (nucleus):
Spinal,
Bulbar,
Midbrain,
Cerebellar
reflex
Slide121Superficial Reflexes
Initiated by gentle cutaneous stimulation
Example:
Plantar reflex is initiated by stimulating the lateral aspect of the sole of the foot
The response is downward flexion of the toes
Indirectly tests for proper corticospinal tract functioning
Babinski’s sign: abnormal plantar reflex indicating corticospinal damage where the great toe dorsiflexes and the smaller toes fan laterally
Slide122122
Voluntary Action
Intentional & conscious by thinking & reasoningReceptor Spinal cord sensory area (cerebrum)
3.
Association area (cerebrum) for
integration
& decision.4. Motor area (cerebrum) Motor neurone Relay Effector
b
c
d
d
Slide123Reflexes VS voluntary action
Reflex Action
Conditional reflex
Voluntary Action
(1)
Inborn
, instinctive
Acquired
via experience / learning
Acquired
via thinking / reasoning
(2)
Cerebrum
not
involved
Cerebrum
involved
Cerebrum
involved
(3)
Involuntary
&
unconscious
Voluntary
& less
conscious
Voluntary
&
conscious
(4)
Fast
action
Slow
action
Slow
action
(5)
Same stimulus
same
response
Unrelated stimulus
same
response
Same stimulus
different
response
Slide124Other reflexes you might want to know about
sneeze reflex
a sneeze is a very complicated thing, involving many areas of the brain
a sneeze is a
reflex
triggered by sensory stimulation of the membranes in the nose, resulting in a coordinated and forceful expulsion of air through the mouth and nose.
why do some people sneeze when they look at the sun?
don’t know
involves the "pupillary light reflex". If you shine a light in your eyes, your pupils get smaller, or constrict.
in the pupillary light reflex, shining a light in the eye causes nerve signals to go from the eye to the brain and then back the eye again, telling the pupil to constrict.
in the usual sneeze reflex, tickling the nose causes nerve signals to go from the nose to the brain and then back out to the nose, mouth, chest muscles
these nerve signals take complicated routes through the brain
but usually the pupillary light reflex and sneeze reflex take different routes.
in 25% of the population - shining a bright enough light in the eye ALSO sends nerves signals from the eye to the brain and then back out to the nose, mouth and chest!
the wires are “crossed a little bit” in some people - so shining a light in the eye "accidentally" activates two different outgoing pathways.
gag reflex
- reflex contraction of the back of the throat that prevents something from entering the throat except as part of normal swallowing
helps prevent choking
also known as a pharyngeal reflex.
touching the soft palate evokes a strong gag reflex in most people,
most people can train themselves to resist the gag reflex,
the afferent limb of the reflex is supplied by the glossopharyngeal nerve (cranial nerve IX) and the efferent limb is supplied by the vagus nerve (cranial nerve X).
absence of the gag reflex is a symptom of a number of severe medical conditions, such as damage to the glossopharyngeal nerve, or the vagus nerve
Slide125-reflexes and clinical significance
1. plantar flexion
- stroke the outer lateral margin of the sole
-curling of toes normal response
-damage to descending motor pathways
alters this reflex
2. Babinski reflex
- stroke the middle of the sole
-great toe extends and the other toes may
or may not fan out - due to incomplete
myelination of of axons in the corticospinal
tract
-in children under 18 months reflex is normal
-older than this - results in the plantar flexion
reflex
- Newborn babies have a number of other reflexes which are not seen in adults, including:
1. suckling
2. hand-to-mouth reflex
3. Grasp reflex
4. Moro reflex, also known as the startle reflex
–may be observed in incomplete form in premature birth after the 28th week of gestation
-normally lost by the 6th month of life postpartum
- a response to unexpected loud noise or when the infant feels like it is falling
- it is believed to be the only unlearned fear in human newborn
- origin of this reflex can be found in that fact that primate infants of our ancestors clung to their mother's fur soon after birth
-if human babies are falling backward - innate reflex will be to stretch out the arms to grab and cling to their mother
-the primary significance of this reflex is in evaluating integration of the central nervous system (CNS), since the reflex involves 4 distinct components:
1. Startle
2. abduction of arms – spreading out of arms
3. unspreading the arms
4. Crying (usually)
Slide126TERIMAKASIH