Reflexes Flashcards Preview

Physiology and Neuroscience > Reflexes > Flashcards

Flashcards in Reflexes Deck (38):
1

What is a reflex?

An involuntary, stereotyped (same type of response is provoked with the same type of stimulus) response to a stimulus

2

What are reflex circuits?

Begin with receptors
End with effectors
Do not reach consciousness

3

What type of circuits are reflex circuits?

Simplest circuits in the nervous system

4

What are tendon jerk reflexes?

Muscle contractions produced by muscle stretch

5

What can tendon jerk reflexes be evoked from?

Many muscles where tendon is accessible

6

What does tapping a tendon do?

Stretches muscle to which it is attached

7

What does tapping a tendon elicit?

A monosynaptic reflex that produces contraction of the stretched muscle

8

What are the basic elements of a reflex circuit?

Element Example of tendon jerk reflex
1. adequate stimulus e.g. tendon tap (muscle stretch)
2. Receptor e.g. muscle spindle
3. Afferent (sensory) neurone) e.g. La primary afferent
4. Central synapses e.g. monosynaptic
5. Efferent (motor) neurone e.g. alpha- motorneurone
6. Effector e.g. skeletal muscle

9

What accompanies the tendon jerk reflex?

La reciprocal inhibition

10

What is simultaneously evoked with the tendon jerk reflex?

Inhibition of antagonist muscle

11

What is la reciprocal inhibition mediated by?

An interneurone- la inhibitory neurone

12

What type of pathway is the tendon jerk and la reciprocal inhibition?

Disynaptic (2 synapses)

13

How does la reciprocal inhibition operate?

In each direction between antagonistic muscles at a joint- hence reciprocal inhibition e.g. stretch of quadriceps muscle causes inhibition of hamstring muscle

14

What are excitation of muscle spindles responsible for?

Stretch reflex

15

What is the tendon jerk reflex useful for?

Clinically, but is a response to an artificial stimulus

16

What is the stretch reflex?

Normal function of the monosynaptic reflex circuit

17

What does prolonged stretch produce?

Prolonged contraction

18

What to stretch reflex act to maintain?

Constant muscle length

19

What is an example of a closed loop in the vestibulo-occular system?

Moving your finger but trying to concentrate on moving finger

20

What is an example of a open loop in the vestibulo-occular system?

Looking at finger while moving head

21

What do both the open and closed loop do in the vestibulo-occular system?

Stabilise the visual image

22

What is visual pursuit?

Movements of object relative to eyes

23

What is a control reflex?

Closed loop
Control some physiological variable e.g. stretch reflex control muscle length

24

What does a stimulus trigger in a control reflex?

Actions which feedback on stimulus e.g. stretch of muscle leads to a reflex response (muscle contraction) which returns the muscle to its original length

25

What is a protective reflex?

Open loop

26

What does a protective reflex not affect?

Stimulus e.g. flexion withdrawal reflex

27

What is a protective reflex accompanied by?

Crossed extensor reflex (both are polysynaptic)

28

What are flexor reflex and crossed extensor reflex mediated by?

Chains of interneurons- polysynaptic (many synapses)

29

What do excitatory and inhibitory interneurones produce?

Appropriate actions on different motoneurone pools

30

What is an example of pathways showing divergence?

Motoneurones with actions at hip

31

what is the carotid sinus baroreceptor reflex?

Autonomic reflex regulating blood pressure

32

What does the carotid sinus baroreceptor reflex control?

Heart rate and force of contraction (cardiac output)
Diameter of blood vessels (peripheral resistance)

33

What are the two ways to change blood pressure

BP= CO x TPR
I.e. Cardiac output or total peripheral resistance

34

What do reflexes involve?

Both somatic and autonomic nervous systems

35

What is the somatic nervous system involved in with regards to reflexes?

(Skeletal muscles)
Spinal cord/ brain stem- mainly control movement of limbs and eyes

36

What is the autonomic nervous system involved in with regards to reflexes?

(Smooth muscles)
Mainly control physiological system

37

Why does the responses being automatic and rapid well suit reflex responses?

Well suited to processes of continuous regulation e.g. baroreceptor
Suited to rapid protextice responses e.g. flexion withdrawal reflex

38

Why are reflex circuits used by higher centres?

Spinal reflex circuits are used descending systems to control movement