Reflexes

Question 1

What are spinal reflexes?

Answer 1

Simple building blocks for movement.

Question 2

What reflex is found is all muscles?

Answer 2

Stretch reflex.

Question 3

Give an example of a stretch reflex.

Answer 3

Knee jerk or patella nedon as uses muscles which monitors muscle length.

Question 4

Muscle stretch stimulates muscle spindles whcih causes…?

Answer 4

Reflex mucle contraction which causes the muslce to shorten to previous lenght.

Question 5

Describe the stretch reflex of the knee jerk in detail.

Answer 5

-Follows a sharp tap to an inelastic tendon, in this case, the knee.
-Force is transmitted to muscle fibres. They are more elastic than tendons so can stretch.
-Stretch activates 1a afferent sensory nerves in the muscle spindle.
-This increases the number of active potentials projecting through the dorsal horn onto the spinal cord.

Question 6

Spindle afferent spindles divide to make how many connections?

Answer 6

3

-one in the brain, two in the spinal cord.

Question 7

Describe a monosynaptic reflex.

Answer 7

One synapse, no interneurons involved.
Directly contacts alpha motorneurons in the stretched muscle causinf rapid contaction of the agonist muscle.

Question 8

Define agonist muscles.

Answer 8

Muscle thaat is conracting.

Question 9

Define antagonsit muscles.

Answer 9

Muscles relaxing and lengthening.

Question 10

Define reciprocal inhibition.

Answer 10

The agonsit muscle contracts and th antagonist muscle stretches in response.
This occurs because spindle afferents connect ad activate inhibitory interneurons which decrease the activation of alpha motorneurons to the agonist muscle which then relaxes.

Question 11

How does spindle afferent firing take messages to the brain and what messages do they take?

Answer 11

Travels up dorsal column to the thalamous and somatosensory cortex to tell the brain about the length of muscles.

Question 12

What do afferent nerves do?

Answer 12

Carry info from sensory receptors (skin, organs) to the CNS

Question 13

What do efferent nerves do?

Answer 13

Carry motor info away from the CNS to the muscles and other glands of the body

Question 14

State the other two names for the inverse stretch reflex

Answer 14

Golgi tendon organ or knife clasp reflex

Question 15

What is the inverse stretch reflex/golgi tendon-organ/knife clasp reflex caused by?

Answer 15

Caused by 1b afferent nerves from the Golgi Tendon Organs (GTO) – which monitor muscle tension

Question 16

What is the inverse stretch reflex/golgi tendon-organ/knife clasp reflex caused by?

Answer 16

Caused by 1b afferent nerves from the Golgi Tendon Organs (GTO) – which monitor muscle tension

Question 17

What happens in the inverse stretch reflex?

Answer 17

Muscle contracts and shortens – this pulls on the tendon and the sensory 1b afferent nerves from the GTO’s increase in the firing of APs.

This causes-
1. Activation of inhibitory interneurons to the agonist muscle.
2. Activation of excitatory interneurones to antagonist muscles.
3. Information about muscle tension ascends in the dorsal columns to the somatosensory cortex

Question 18

Why is it known as a clasp knife reflex?

Answer 18

Because greatly increasing tension in tendon leads to a collapse of resistance
like a spring-loaded knife opening up

It is a protective mechanism to prevent muscle damage

Question 19

What kind of info do flexor/withdrawal reflexes use?

Answer 19

Info from pain receptors (nociceptors) in skin, muscle and joints.

Question 20

What does polysynaptic mean?

Answer 20

Involving two or more synapses in the CNS.

Question 21

Flexor/withdrawal reflexes are…

Answer 21

Polysynaptic and protective.

Question 22

How do flexor/withdrawal reflexes withdraw part of the body away from the painful stimulus and in towards the body?

Answer 22

Increased active potential of nociceptors.

Question 23

Describe the five things that increased active potential of nociceptors does.

Would recommend writing this out a few times if strugglig b

Answer 23

1. Increased activity in flexor muscles.
2. The antigonistic extendors are inhibited.
   3.Excitatory interneurones cross the spinal cord and excite the contralateral extensors
3. Other interneurones cross the spinal cord, synapse with inhibitory neurones and they inhibit the contralateral flexors helping to miantain the body’s upright posture.
4. Sensory information ascends to the brain in the contralateral spinothalamic tract.

Question 24

what does the flexor receptor cause in response to pain?

Answer 24

Ipsilateral flexion.

Question 25

Describe the diameter of nociceptive sensory fibres nd how this impacts function

Answer 25

Small diameter so conducts slowly

Question 26

Which reflex is slower?

Flexor and crossed extensor reflex or the stretch reflex?

Answer 26

Flexor and crossed extensor reflex as diamter is smaller.

Question 27

How can we carry an increasing load in our hands?

Answer 27

The load stretches the muscle and its spindles, causing reflex contraction to restore the arm position (the stretch reflex).

Muscle and muslce spindles stretch as arm drops.
Reflex contarction initiated by

Question 27

How can we carry an increasing load in our hands?

Answer 27

The load stretches the muscle and its spindles, causing reflex contraction to restore the arm position (the stretch reflex).

Muscle and muslce spindles stretch as arm drops.
Reflex contarction initiated by uscle spindles restores the arm position.

Question 28

What happens if exessive load is placed on a muscle?

Answer 28

GTO reflex is activated ausing relaxation hence protecting the muscle.

Question 29

How can the GTO reflex be over ridden?

Answer 29

By voluuntary input from the CNS.

The neuron from the GTO fires but the motor neuron is inhibited so msucle relaxes and the load drops.

Question 30

An alpha motorneuron can recieve 10,000 synapses.

Where are they from and what do they cause?

Answer 30

From the thalamous and cortex.

Cause excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs).

Question 31

While some synpases make direct contact to an alpha motorneuron, how do most interact?

Answer 31

Through interneurons.

Question 32

What effect does the distance between the dentride and the cell body have on the membrane potential?

Answer 32

The more distant a dentrite, the less effect it has on the membrane potetial

Question 33

If you don’t want to drop something, what might happen?

Answer 33

Descending voluntary excitation of alpha motoneurones overrides the inhibition from the GTOs and maintains muscle contraction – so preventing the GTO reflex

Question 34

How can the stretch reflex be overridden?

Answer 34

High activity in upper motor neurones spreads to and depolarises lower level motorneurones and this overcomes the descending inhibition.

Question 35

Can the withdrawal reflex be overridden?

Answer 35

Yes but briefly.

Imagine carrying a bowl of soup which is very hot. You can stop yourself from spilling it immediatly all over yourself as more damage will be done so essentiallu you have enough tie to put it down quickly but safely.

Question 36

Describe breifly how facilitation occurs.

Answer 36

Firing of neurons can cause action potential in motorneurons.
can also cause the partial depolarisation of neurons nearby but not to threshold.

??btw hun idk this is just what i took from the slides, ik im useless xox

Question 37

What is the Jendrassik manoeuvre?

Answer 37

The knee jerk reflex i.e.tendon below knee is hit to see if the patellar reflex is functioning.