CPT1: Spinal reflexes KC

Question 1

What are reflexes?

Answer 1

Involuntary movement in response to a stimulis occuring almost immediately after the stimulis

Question 2

What is an example of a simple spinal reflex?

What does this involve?

Answer 2

• Stretch reflex
• involeves 2 neurons and a single synpase. Sensory neuron axon synapses with moto neuron.
• sensory information also passed to higher centres but not necessary in reflex

Question 3

Where is the sensory axon cell body found?

Answer 3

Lies in the dorsal root ganglia of the lumbar region of the spinal cord

Question 4

What is an example of a protective reflex? Describe it

Answer 4

The flexion withdrawl reflex - the withdrawl of a limb from Painful stimulsis

Question 5

Why cant the flexion withdrawl reflex be used as a test for patients? what is used instead and why?

Answer 5

• Have to induce pain
• a hand reflex is svoked which has similar features to the withdrawl reflec

Question 6

What happens in the flexion withdrawl reflex?

Answer 6

• Stimulation of pain/ nociceptive neurons causes stimulation of the limb and withdrawl of it. At the same time there is inhibition of the extrusor muscles in the opposite limb

Question 7

What is an example of a plantar reflex?

Describe what it is and what happens?

Answer 7

• The babinski reflex
• When the soul of the foot is stroked the big toe undergoes a particular reflex
• Upper motor neuron lesion - dorsiflexs/ extends upwards. This indiates damage to Spinal cord/ brain
• Young infants - dorsiflexes/ extents upwards as coticospinal cord pathways not fully myleinated
• normal adults - flexes downwards. Cerebal cortex inhibits the babinski sign

Question 8

Where do lower and upper motor neuron liesions occur? what are the effects>

Answer 8

• Upper: the brain
• hyperreflexia, increase in muscle tone, resistance to movement, muscle weakness/ wasting (moderate), babinski sign
• Lower: the anterior horn of the SC
• hyporeflexia, atonia or hypotonia, muscle weakness/ wasting /(severe), no babinski sign, muscle paralsis, spontanious contraction of a set group of muscle fibres

Question 9

What is the corneal reflex?

Answer 9

blind reflex

closing of the eye to protect it from forgein objects or bright light

Question 10

What is the accomidation reflex?

Answer 10

constriction of the pupils to view near objects

Question 11

What is the pupilary light reflex?

Answer 11

The modification of pupil diamter in response to light

Question 12

What is the cross extensot reflex?

Answer 12

Occurs in conjuction with the flexion withdrawl reflex to help provide support

Question 13

What are the processes in a polysynaptic reflex?

Answer 13

1. Sensory neuron activated
2. information sent to CNS
3. information processed in CNS
4. Information passed to motor neurons
5. mortor neuron activated
6. Effector response

Question 14

The the knee jerk response, what does a stronger and weaker reflex mean?

Answer 14

1. Stronger - upper motor damage. Upper motor neurons can supress repsonse so damage leads to inhibition of this supression
2. weaker - damage to lower motor neurons

Question 15

What is used to measure the response from the knee jerk reflex?

What does this measure?

Answer 15

Electromyography - measures electrical activity of skeletal muscle

Question 16

What can be said about simple reflexs?

Answer 16

they are influecned by other neurones e.g. lower motor neurons of spinal cord

Question 17

What happens in the anklejerk?

Answer 17

1. Tendon hammer hits acchiles tendon
2. This causes gastocnemius muscle to stretch which is connected to calcaneus
3. This initates reflex mediated by tibil nerve via s1 nerve root
4. resulting in contraction of tricep surae muscle causing plantar flexion of foot

Question 18

What happens when light is shawn on the eye? what happens tothe other eye?

Answer 18

• Direct light response - light causes the circular muscle of the iris to contract which causes the iris to contract, which causes pupil diameter to decrease
• Consensual light response - the circular muscle in the opposite eye contracts, the iris contracts and pupil dimater decreases

Question 19

What happens to pupil diameter when focused on near objects?

Answer 19

it decreases. Parasympathetic fibres cause the ciliary muscles to contract. At the same time the circular muscles of the iris contract via parasympathetic innveration which reduces pupil diameter and prevents blurred vision

Question 20

What are the advantafes of the accomidation reflex?

Answer 20

• Protects the retina from too much light

Question 21

What is the babinski sign a sign of?

Answer 21

brain or spinal cord damage