Neurophysiology - spinal reflexes

Question 1

What is a reflex?

Answer 1

• A basic functional unit of the nervous system.
• It is a cognitive independent response of the nervous system to a stimulus and the reaction of the organism to receptor stimulation mediated by the CNS.

Question 2

What is a stimulus?

Answer 2

refers to any alteration in the environment that has some impact on neurons and is characterized by it’s quality, quantity and adequacy.

Question 3

What is a threshold?

Answer 3

The threshold refers to the intensity of the stimulus necessary to evoke a response

Question 4

How are reflexes differentiated?

Answer 4

• Receptors: exteroreceptive, interoreceptive, proprioreceptive
• The centre: extracentral (axonal, ganglial), central (brain, spinal cord)
• Effectors: somatic, autonomic
• conditions: conditioned, unconditioned

Question 5

Which axis is a reflex arc formed by?

Answer 5

receptor(sensoric neuron) –> afferent pathway–> the centre–>efferent pathway –> effector (motoric neuron)

Question 6

What is the difference between monosynaptic reflex arcand polysynaptic reflex arc?

Answer 6

Mono –> one synapse between neurons

Poly –> include interneurons

Question 7

What does a neurological examination involve?

Answer 7

A set of investigative methods which should be performed in a logical order

Question 8

How is a neurological examination performed?

Answer 8

• observation –> behaviour, posture, movement, cognition
• palpation–> of muscle tonus
• examination of spinal reflexes–> reaction testing, brain, nerves, perception

Question 9

Name 4 most common myotatic reflexes and their centre.

Answer 9

• Tibialis cranialis ( L6-S2)
• Flexor reflex (L4-S3 hind limbs)(C6-Th2 front limbs)
• Extensor carpi radialis reflex (C7-Th1)
• Triceps reflex (C6-Th1)

Question 10

What is proprioreception?

Answer 10

The cerebellum is largely responsible for coordinating the unconscious aspects of proprioception.
Proprioception, is the sense of the relative position of one’s own parts of the body and strength of effort being employed in movement.
In humans, it is provided by proprioceptors in skeletal striated muscles (muscle spindles) and tendons (Golgi tendon organ) and the fibrous membrane in joint capsules.

Question 11

What is hyporeflexia?

Answer 11

low levels of reflex action

Question 12

What is areflexia?

Answer 12

No reflex action

Question 13

What can be used to distinguish between hyporeflexia and areflexia?

Answer 13

Enhancing maneouvers –> crossed knee on a seat, closed eyes, kneeling on a chair.
They Decrease muscle tension and enable a more distinguishable reflex reaction

Question 14

Name 5 reflexes that can be used in proprioreception?

Answer 14

• Nasopalpebral reflex (nn. V,VII)
• Triceps reflex (C7)
• Biceps reflex (C5)
• Achilles tendon reflex (L2-S2)
• Patelar reflex

Question 15

What is myotatic reflex?

Answer 15

is a muscle contraction in response to stretching within the muscle. It is a monosynaptic reflex which provides automatic regulation of skeletal muscle length.

Question 16

Name reflexes associated with the function of cranial nerves?

Answer 16

Olfactory
Pupillary
Corneal
Defence (fast hand movement towards face)
Cotton puff (on cornea)

Question 17

What is cross-extensor reflex?

Answer 17

How the spinal reflex action is not limited to motor responses only on one side of the body. If animal step on sharp object reflex arc is initiated to withdraw injured limb from stimulus, the opposite limb(s) simultaneously prepare to bear the weight so the animal does not loose balance. –>work on both sides

Question 18

Two functions of the spinal cord according to location?

Answer 18

• link of information between brain and body (afferent-efferent nerves)
• integrate reflex activity –> between afferent input and efferent input without involving the brain.