2. Reflex
• Reflex is the mechanism by which sensory
impulse is automatically converted into a
motor effect thru the involvement of CNS.
3. Reflex arc
• Pathway for any reflex action is known as
reflex arc. it consists of:
• Afferent limb: receptor and afferent nerve.
• Efferent limb: efferent nerve and effector
organ.
• Centre: part of CNS where afferent limb ends
and either synapses directly with efferent
motor neuron or establish connection with
efferent neuron thru intercalated neurons.
5. Clinical classification
• Superficial: initiated by stimulating
appropriate receptors of skin or mucous
membrane.
• Are usually multisynaptic .
• Are usually involving moving away from
stimulus
• E.g. plantar response, corneal and conjunctival
reflexes.
6. Deep reflexes
• Are elicited on stroking the tendon.
• Are basically stretch reflexes
• Are also called tendon reflexes
• E.g. knee jerk, ankle jerk etc.
7. Visceral reflexes
• Are the reflexes where at least one part of the
reflex arc is autonomic nerve
• E.g, pupillary reflex, carotid sinus reflex.
8. Pathological reflexes
• Are not found normally
• Presence indicates pathological condition
within the body
• E.g, Babiniski’s sign.
9. Anatomical classification of reflexes
• Segmental reflexes: in these end of afferent
neuron and beginning of efferent neuron are
in the same segment of spinal cord.
• Intersegmental reflexes: end of afferent
neuron and beginning of efferent neuron are
in the spinal cord but in different segments.
• Suprasegmental: centre for such reflex lies
above the spinal cord.
10. Physiological classification
• Flexor reflexes: are produced when
nociceptive stimulus is applied.
• Stimulus causes flexion of joint.
• E.g thorn prick to a sole causes flexion of
knee, hip joints.
• Extensor reflexes: stretch reflexes are extensor
reflexes which are the basis of tone and
posture.
11. Depending upon inborn or acquired
reflexes
• Unconditioned reflexes: are inborn reflexes.
• E.g pulling the hand away from a burning hot
object.
• Conditioned reflexes: are reflexes that develop
after birth, are result of practice and learning.
12. Spinal cord integrates many basic
reflexes
• Serve as a link for transmission of information
b/w the brain and the remainder of body.
• Integrate reflex activity b/w afferent input and
efferent output without involving the brain.
This type of reflex activity is called a spinal
reflex.
13. Stretch reflex
• Is simplest reflex.
• Is monosynaptic.
• In which an afferent neuron originating at a
stretch detecting receptor in a skeletal muscle
terminates directly on the efferent neuron
supplying the same skeletal muscle to cause it
to contract and counteract the stretch.
14.
15.
16.
17.
18.
19. Withdrawal reflex
• When a person receives any painful stimulus, a
withdrawal reflex is initiated to withdraw from
painful stimulus.
• Afferent neuron stimulates excitatory
interneurons that stimulate the efferent motor
neurons supplying the muscle, that flexes and
pulls away from painful stimulus.
• The afferent neuron also stimulates inhibitory
interneurons that inhibit the efferent neurons
supplying the antagonistic muscle to prevent it
from contracting.
20.
21.
22. Reciprocal inhibition
• The type of connection involving stimulation
of nerve supply to one muscle and
simultaneous inhibition of the nerves to its
antagonistic muscle is known as reciprocal
innervation.
23. Withdrawal reflex
• Afferent neuron also stimulates interneurons
that carry signal up the spinal cord to brain via
an ascending pathway.
• When impulse reaches sensory area of cortex
person becomes aware of pain, its location
and type of stimulus.
• The activity at the conscious level is above and
beyond the basic reflex.
24. Crossed extensor reflex
• Reflex arc initiate to withdraw injured limb from painful
stimulus, while opposite limb prepares to suddenly
bear all the weight so that the person does not lose
balance or fall.
• Bending of injured extremity’s knee is accomplished by
concurrent reflex stimulation of muscles that flex the
knee and inhibition of muscles that extend the knee.
• Extension of opposite limb’s knee is accomplished by
activation of pathways that cross over to the opposite
side of the spinal cord to reflexly stimulate extensors
and inhibit flexors.
25.
26. Spinal reflexes
• All spinal reflexes can be voluntarily
overridden at least by higher brain centers.
