✅involuntary Movement

Question 1

What is a reflex?

Answer 1

Involuntary motor response mediated by a neural arc in response to a sensory input; can be generated in spinal cord segments with commands from higher brain centres.

Question 2

What is the reflex arc?

Answer 2

it is the neural pathway used in reflex action

Question 3

What does the reflex arc consist of?

Answer 3

The afferent nerve input to the nerve centre.

The nerve centre that produces activity in the efferent nerves to an effector organ.

Question 4

Where does the reflex arc begin?

Answer 4

A receptor

Question 5

Where does the reflex arc end?

Answer 5

Peripheral effector

Question 6

What are the three main points of neural reflexes?

Answer 6

• Rapid, automatic responses to specific stimuli
• Basic building blocks of neural function
• One neural reflex produces one motor response

Question 7

What happens at Step 1: Arrival of stimulus, activation of receptor

Answer 7

Physical or chemical changes

Question 8

What happens at Step 2: Activation of sensory neuron

Answer 8

Graded depolarization

Question 9

What happens at Step 3: Information processing by postsynaptic cell

Answer 9

Triggered by neurotransmitters

Question 10

What happens Step 4: Activation of motor neuron

Answer 10

Action potential

Question 11

What happens at Step 5: Response of peripheral effector

Answer 11

Triggered by neurotransmitters

Question 12

What are somatic reflexes?

Answer 12

-Involuntary control of muscle (posture and movement)
-Respond to afferent stimulation
(Eg. Knee-jerk)

Question 13

What are visceral reflexes?

Answer 13

Control systems other than muscular system

E.g( coughing, sneezing etc)

Question 14

What are cranial reflexes?

Answer 14

They occur in the brain

E.g. ( reflex movements in response to sudden loud noises, jumping when scared)

Question 15

What are spinal reflexes?

Answer 15

They occurs in the spinal cord

E.g. ( walking, running, typing)

Question 16

What reflexes range in complexity?

Answer 16

Spinal reflexes

Question 17

What happens with the Monosynaptic Reflex (stretch reflex)?

Answer 17

There is little delay between sensory input and motor output.

Question 18

What does muscle stretch lead to?

Answer 18

activation of Ia afferent

Question 19

What does La Afferent make?

Answer 19

monosynaptic excitation of motoneurones from same and agonist muscles

Question 20

How quickly does contraction in the spinal muscles occur?

Answer 20

20-40msec

Question 21

What is contraction of the muscle?

Answer 21

compensation to stretch

Question 22

What does reflex act to prevent?

Answer 22

Length change

Question 23

What are the 4 points of Reciprocal Inhibition?

Answer 23

• Stretch reflex excites motoneurones from agonists

* but inhibits antagonists
• Ia inhibitory interneurone
• disynaptic inhibitory pathway

Question 24

What does Afferent Inhibition prevents skeletal muscle from?

Answer 24

• Developing too much tension
• Tearing or breaking tendons

Question 25

Where does the Afferent inhibition arise from?

Answer 25

from activation of Golgi Tendon Organ

Question 26

How does the afferent inhibition act?

Answer 26

Acts via Ib inhibitory interneurone

Question 27

When does the Afferent inhibition act?

Answer 27

Only operates in posture not during walking

Question 28

What is the Polysynaptic Reflex (tendon reflex)?

Answer 28

A Complicated response (more than monosynaptic reflexes)

Question 29

What controls more than one muscle group?

Answer 29

Interneurons

Question 30

What can polysynaptic reflexes produce?

Answer 30

EPSPs or IPSPs

Question 31

What can polysnyaptic reflexes cause?

Answer 31

Many spinal segments

Question 32

What can polysynaptic reflexes do?

Answer 32

Move body part away from stimuli (pain or pressure)

Question 33

What is Flexion Withdrawal Reflex?

Answer 33

Action to move part of body away from painful or harmful stimulus

Question 34

What is the Crossed Extensor Reflex?

Answer 34

The stretch, tendon and withdrawal reflexes are ipsilateral reflex arcs (ipsi, same + lateral, side): sensory stimulus and motor response occur on the same side of the body. This is a contralateral reflex arc (motor response occurs on the side opposite the stimulus.

Question 35

What happens when Flexor reflex causes leg to pull up

Answer 35

Crossed extensor reflex straightens other leg to receive body weight and stop person falling over

Question 36

What is a flexor reflex?

Answer 36

The quick contraction of the flexor muscles resulting in the withdrawal of a limb from an injurious stimulus

Question 37

What needs to happen for a flexor reflex?

Answer 37

Contraction of the flexors and relaxation of the extensors in that limb

Question 38

What is a Polysynaptic reflexive arc

Answer 38

A pathway in which signals travel over many synapses on their way back to the muscle

Question 39

What are Five General Characteristics of Polysynaptic Reflexes?

Answer 39

1. Involve pools of interneurons
2. Are intersegmental in distribution
3. Involve reciprocal inhibition
4. Can be long lasting
5. Several reflexes cooperate
   – To produce coordinated, control response

Question 40

Reflexes adapt to the existing conditions and can be modified by sensory input at the spinal cord level
True or Flase?

Answer 40

True

Question 41

How can Higher Centres can alter Spinal Reflexes?

Answer 41

Can facilitate or inhibit reflex motor patterns based in the spinal cord
– Example: Suppression of flexion reflex during walking

Question 42

What is Spasticity?

Answer 42

Hyperactive stretch reflex leads to spasticity (long lasting uncontrolled
muscle contractions, sometimes rythmic – called clonus)

Question 43

The Brain can Alter Spinal Reflexes.

T or F

Answer 43

True

Question 44

What are Voluntary movements and reflex motor patterns?

Answer 44

• Higher centers of brain incoporate lower, reflexive motor patterns
• Automatic reflexes
– Can be activated by brain as needed
– Use few nerve impulses to control complex motor functions
• Examples: walking, running, jumping