Reflexes --> end of module 3

Question 1

Types of movement

Answer 1

Can be classified as reflex, rhythmic, or voluntary:

Reflex Movements:
Least complex
At the spinal cord or brain stem

Rhythmic Movements:
Intermediate complexity
In the spinal cord with input from the brain
Example: Walking, running

Voluntary Movements:
Most complex
In the cerebral cortex
Require coordination
Example: Playing tennis

Question 2

Types of neural reflexes

Answer 2

-Automatic responses to stimuli that don’t require conscious thought.
-Help maintain posture
-rapid
-Can be controlled by . the somatic motor system or ANS.
-Processed in the spinal cord (spinal reflexes) or the brain (cranial reflexes).

Question 3

Neural reflexes can be classified by:

Answer 3

1. Efferent division that controls the effector
2. Integrating region within the central nervous system
3. Time at which the reflex develops
4. The number of neurons in the reflex pathway

Question 4

Monosynaptic and polysynaptic reflexes

Answer 4

• The “wiring” for a reflex is called a reflex arc
• Reflex arcs consist of
  
  1. Receptor
  2. Sensory neuron
  3. Integration centre
  4. Motor neuron
  5. Effector
     Monosynaptic Reflexes:
     Have a single synapse between sensory (afferent) and motor (efferent) neurons. Very quick

Polysynaptic Reflexes:
Involve one or more interneurons between sensory and motor neurons.

Question 5

Reflex receptors

Answer 5

nerve endings, or groups of cells

Examples:
Pain receptors (nociceptors): Detect pain
Temperature receptors (thermoreceptors): Detect temperature changes
Light receptors (photoreceptors): Detect light
Chemical receptors (chemoreceptors): Detect chemicals
Stretch receptors (mechanoreceptors, proprioceptors): Detect muscle length

Question 6

Somatic (motor) reflexes
Muscle spindles detect muscle stretch

What are muscle spindles, and Golgi tendon organs

Answer 6

Muscle Spindles: Detect muscle stretch
-Contain their own small muscle fibres
-Sensory neurons wrap around the spindle to detect changes in muscle length
-Stretching the spindle increases sensory neuron firing
-Compressing the spindle decreases sensory neuron firing

Golgi Tendon Organs: Detect muscle tension in tendons

Question 7

The stretch reflex (most simple reflex we have in our bodies)

Answer 7

Stretch Reflex: A contraction response to muscle stretch
-Allows adjustment to posture in response to internal muscle stimuli
-Causes contraction of the same muscle (via extrafusal muscle fibres)

Question 8

The knee jerk reflex

Answer 8

1. Tapping the patellar ligament stretches the quadriceps and excites its muscle spindles.
2. Afferent impulses travel to the spinal cord, where they synapse with motor neurons and interneurons.
3. Responses:
   3a) Motor neurons send activating impulses to the quadriceps, causing it to contract and extend the knee.

3b) Interneurons inhibit the ventral horn neurons, preventing the antagonist muscles (hamstrings) from resisting the quadriceps contraction.

Question 9

Clinicians test reflexes and assess muscle tone, what happens when it is too small or too big (reflex)

Answer 9

• Too small -> problem with sensory nerve, spinal cord, motor nerve or muscle fibres
• Too big -> problem with motor signals

Question 10

The crossed extensor reflex

Answer 10

• Polysynaptic reflex pathway
• Causes a limb to be pulled away from a painful stimulus

Involves ipsilateral and contralateral responses

Question 11

Ipsilateral (same side as stimulus) -> withdrawal by:

Answer 11

lifting our leg to stop stepping on glass
-Activation of flexor muscle (hamstring)
-Relaxation of extensor muscle (quad)

Question 12

Contralateral (opposite side to stimulus)

Answer 12

-straightens to bear body weight
-Activation of extensor muscle (quad)
-Relaxation of flexor muscle (hamstring)
-In order to stabilise we need to contract, the extensor muscles relax the hamstring

Question 13

Somatic motor vs autonomic reflexes

Answer 13

• Somatic reflexes have one motor neuron in efferent pathway from CNS
• Autonomic NS has two efferent neurons
  –>Pre-ganglionic neuron
  –>Post-ganglionic neuron

Question 14

Autonomic NS reflexes

Answer 14

Visceral Sensory Neurons:
Send information about changes in chemicals, stretch, and temperature in internal organs.

Examples:
Need to urinate: Response to bladder stretching
GI smooth muscle contraction: Response to stretch from food
Changing blood pressure: Response to standing up

Question 15

Pupillary light reflex - cranial reflex

Answer 15

-Photoreceptors in the retina detect light.
-Send signals to the brainstem.

-In low light, sympathetic fibres dilate the pupil.
-In bright light, parasympathetic fibres constrict the pupil.

-Protects the eye and assists with focus.
-Checks brain damage: No response indicates potential brainstem damage