Reflexes (Struc Func. Bio)

Question 1

Reflex is a simple, involuntary reaction to a stimulus

Reflex arc includes:

? receptors
? neurons in the nerve
? of spinal cord
? neurons in the nerve
? junction
? or other end organ

Monosynaptic reflex – small segment of ?, tests a very ? area, ex – * ? *

Polysynaptic reflex – small or broad area?, multiple or single segments,? ex - ?

NOTE: dorsal branch AKA ramus (from the spinal cord to hand telling it to move from hot matchstick

sensory directly once to synapse to motor)

Answer 1

Reflex is a simple, involuntary reaction to a stimulus

Reflex arc includes:

sensory receptors
sensory neurons in the nerve
segment of spinal cord
motor neurons in the nerve
neuromuscular junction (synapse: a junction between a NEURON and the next CELL; the neuromuscular junction is a kind of synapse, one that occurs between MOTOR neurons and MUSCLE cells)
muscle or other end organ

Monosynaptic reflex – small segment of nervous system, tests a very specific area, ex – * PATELLA REFLEX *

Polysynaptic reflex – broad area, multiple or single segments, ex - withdrawal

Question 2

Stimulus – a change in the ?
Receptor – the end of a ? neuron that responds to a ?
Sensory (afferent) neuron – sends ? to the CNS

Interneuron – located in the ?, ? a sensory neuron to a motor neuron
Motor (efferent) neuron – carries an impulse (info) to an ?/?

Answer 2

Stimulus – a change in the environment
Receptor – the end of a sensory neuron that responds to a stimulus
Sensory (afferent) neuron – sends sensory impulses to the CNS

Interneuron – located in the spinal, connects a sensory neuron to a motor neuron
Motor (efferent) neuron – carries an impulse (info) to an muscle/organ

FOR PRE-GANGLIONIC/SYNAPTIC
- 2 cell bodies; 1 in interneuron and another one in dorsal root ganglion

Question 3

The MONOSYNAPTIC reflex

• Most ?, ?, slow or rapid?
  (* Also called stretch reflex)

1. The stretch on the ?
2. stimulates muscle ?
3. send information via the ?
   (sensory) neuron to the spinal cord.
4. The impulse is then transmitted
5. to the ? (motor) neuron
   whose axon innervates
6. The ? muscle (REFER TO PIC)

NO INTERNEURON IN MONOSYMAPTIC REFLEX!

• not v common

Answer 3

The MONOSYNAPTIC reflex

• Most simple, uncommon, rapid!
  (* Also called stretch reflex)

1. The stretch on the tendon
2. stimulates muscle spindles
3. send information via the afferent
   (sensory) neuron to the spinal cord.
4. The impulse is then transmitted
5. to the efferent (motor) neuron
   whose axon innervates
6. The quadriceps muscle (REFER TO PIC)

NO INTERNEURON IN MONOSYMAPTIC REFLEX!

• not v common

Question 4

MONOSYNAPTIC REFLEX

• A stretch reflex that tests the ? nerve.
• When the patellar ligament is struck, there should be a ? of the ? muscle.

(** REFER TO PIC! in this reflex, sensory ganglion and receptor present in the PNS

and synapse present in CNS

lower motor neuron and neuromuscular junction present in PNS **)

Answer 4

MONOSYNAPTIC REFLEX

• A stretch reflex that tests the femoral nerve.
• When the patellar ligament is struck, there should be a contraction of the quadricep muscle.

** REFER TO PIC! in this reflex, sensory ganglion and receptor present in the PNS

and synapse present in CNS

lower motor neuron and neuromuscular junction present in PNS **

Question 5

The Polysynaptic Reflex

• May involve motor neurons to ? muscles
• May involve ? of muscle contraction

1. ? receptor
2. ? neuron
3. ? on Interneuron
4. ? at motor neuron
5. Muscle
6. Spinal cord

Interneuron in the spinal cord

(cutaneous trunk - interneuron all the way to spinal cord place - MIDDLE MAN PRESENT)

Answer 5

The Polysynaptic Reflex

• May involve motor neurons to several muscles
• May involve inhibition of muscle contraction

1. skin receptor
2. sensory neuron
3. synapse on Interneuron
4. synapse at motor neuron
5. Muscle
6. Spinal cord

Interneuron in the spinal cord

(cutaneous trunk - interneuron all the way to spinal cord place - MIDDLE MAN PRESENT)

Question 6

Withdrawal Reflex = POLYsynaptic reflex

• Flexion of all joints of pinched limb
• ? contraction of many flexor muscles across ? joints
• Message to opposite leg to ? muscles
• The skin between the toes are pinched and there should be a ? of the joints.
• Use a MINIMUM amount of force to elicit a ? reflex.
• If too much force, then you are testing ? (reflex -> pain; in reflex no conscious perception/BRAIN NOT involved)

Answer 6

Withdrawal Reflex = POLYsynaptic reflex

• Flexion of all joints of the pinched limb
• coordinated contraction of many flexor muscles across several joints
• Message to opposite leg to extensor muscles
• The skin between the toes are pinched and there should be a flexion of the joints.
• Use a minimum amount of force to elicit a withdrawal reflex.
• If too much force, then you are testing PAIN

(reflex -> pain; in reflex no conscious perception/BRAIN NOT involved)

Question 7

Reflex vs Response

A reflex only involves the ?. It is an automatic reaction to a ? that does not involve ? thought. They will be present even if the spinal cord is severed cranial to the reflex.

A ? carries sensory information to the brain for ?.

Answer 7

Reflex vs Response

A reflex only involves the spinal cord. It is an automatic reaction to a stimulus that does not involve conscious thought. They will be present even if the spinal cord is severed cranial to the reflex.

A response carries sensory information to the brain for interpretation.

(polysnaptic still a reflex just a couple of passing of batons within spinal cord (STILL NOT BRAIN INVOLVED); - just a response that becomes brain invovled; nerves to spinal cord and back out a..)

Question 8

LMN and UMN

LMN = motor neuron in the peripheral nervous system that connects directly to the ?; originates in the ? matter of the spinal cord in the ? area

TV cord

LMN damage more likely to be ?
Flaccid muscle tone, loose and floppy; reflexes ? to ?

UMN = located totally in the ?; a neuron that communicates with the LMN to initiate ? movement; originates in the ? and travels within the ? to communicate with the LMN in the ? matter

Electrical outlet

UMN damage more or less likely to recover? Need to find a ? neuron connection. Some tone in muscles, muscle tone may be exaggerated

Answer 8

LMN and UMN

LMN = motor neuron in the peripheral nervous system that connects directly to the muscle; originates in the gray matter of the spinal cord in the reflex arc area

TV cord

LMN damage more likely to be permanent
Flaccid muscle tone, loose and floppy; reflexes weak to absent

UMN = located totally in the CNS; a neuron that communicates with the LMN to initiate motor movement; originates in the CNS and travels within the spinal cord to communicate with the LMN in the gray matter

Electrical outlet

UMN damage MORE likely to recover! Need to find a new neuron connection (note: lots of them so if one gets damaged another one can alway be used) Some tone in muscles, muscle tone may be exaggerated

Question 9

Spinal Functional Segments

(if no limb then bypass to the more caudal area; if limbs then cell body near it somewhere)

Higher Cervical C1-C5 – UMN

Lower Cervical C6-T2 – LMN to front and UMN to the rear

Thoracolumbar T3-L3 – UMN to the rear

Lumbosacral L4-S3 – LMN to the rear legs

Sacrocaudal S1 – caudal – LMN to the bladder, anus, and tail

Answer 9

Question 10

Menace Response

• ? in response to a potentially harmful object advancing toward the one eye
• The ? eye must be covered
• Positive response is ?
• Not seen in puppies/kittens under 16 wks old
• ? response (so little puppies and kittens don’t have that)
• Travels up the spinal cord to the cerebrum or cerebellum?

Answer 10

Menace Response

• blinking in response to a potentially harmful object advancing toward the one eye
• The opposite eye must be covered
• Positive response is blinking
• Not seen in puppies/kittens under 16 wks old
• learned response (so little puppies and kittens don’t have that)
• Travels up the spinal cord to the cerebrum.

Question 11

Pupillary Light Reflex

• Involves CN ? (optic nerve) and CN ? (oculomotor nerve)
• Does not assess ?
• With bright light, pupil will ?

Panniculus Reflex
* Patient is lightly touched along the ? surface of the back.
* The muscle along the back is the cutaneous ?.

• A stimulus to the lateral trunk causes the
  cutaneous trunci muscle to ?.
• Ascending sensory tracts extend up the spinal cord to the cell body of the ? in spinal cord segment C8.
• The lateral thoracic nerve supplies ?
  innervation to the cutaneous trunci.
• This response is not found over the ? or ? areas.

Answer 11

Pupillary Light Reflex

• Involves CN II (optic nerve) and CN III (oculomotor nerve)
• Does not assess vision
• With bright light, pupil will constrict

PANNICULUS Reflex (Panni”cu”lus)
* Patient is lightly touched along the dorsal surface of the back.

• The muscle along the back is the “cu”taneous trunci.
• A stimulus to the lateral trunk causes the
  cutaneous trunci muscle to twitch.
• Ascending sensory tracts extend up the spinal cord to the cell body of the lateral thoracic nerve in spinal cord segment C8
• The lateral thoracic nerve supplies motor
  innervation to the cutaneous trunci.
• This response is not found over the sacral or cervical areas.

Question 12

Palpebral Reflex
* Touching the eyelid sends sensory information over the ? nerve to synapse with the facial nerve in the ?
* Motor fibers of the facial nerve cause the ? muscle to contract.
* Often used to evaluate depth of anesthesia.

Perineal Reflex
* Tested by touching the ? of the perineal area
* Positive test causes ? of the anal sphincter and ? of the tail
* Mediated by the ? nerve, with roots from S#?-S#?

Answer 12

Palpebral Reflex
* Touching the eyelid sends sensory information over the trigeminal nerve to synapse with the facial nerve in the brain stem

• Motor fibers of the facial nerve cause the orbicularis oculi muscle to contract.
• Often used to evaluate the depth of anesthesia.

Perineal Reflex
* Tested by touching the sides of the perineal area
* Positive test causes contraction of the anal sphincter and flexion of the tail
* Mediated by the pudendal nerve, with roots from S1-S3

menace response: reacting to it (more alert and awake than menace response)

if not then more palpebral reflex as not interpreting it