Week 3 (MC) - Sensory Systems

Question 1

What is the Golgi Tendon Organ?

Answer 1

Is a Mechanical Pressure Detector
Sensory receptors located at the junctions between muscles and tendons. They detect changes in muscle TENSION rather than length. When tension in the muscle increases (due to contraction), the GTOs are activated, sending signals to the central nervous system to inhibit further contraction, preventing excessive force that could damage the muscle or bone

Question 2

How does the Golgi tendon organ fire?

Answer 2

The Afferent Nerve Fibres (bulbs) inside the network of collagen fibres, become squished and activate to detect pressure within the tendon –> sensitising the nerve

Question 3

What is the role of an interneuron in a protective reflex?

Think about golgi tendon organs and what role they play?

Answer 3

1. The neuron of the golgi tendon organ fires
2. The interneuron (within the spinal cord) releases neurotransmitter to the block the motor unit causing it to relax
3. Muscle relaxes
4. Tension/load is dropped

This occurs to prevent injury as the Golgi tendon organ has sensed a large degree of tension and thus activates the interneuron to inhibit the muscular contraction.

Question 4

Where are joint receptors located?
What is their role?

Answer 4

Anywhere that there is synovial joints will have joint receptors
Located in the articular surfaces of the joint and around the joint capsule

The main role is to provide sensory awareness of the joint position in space
It also informs about potential injury risks –> potential extremes of flexion or extension

Question 5

What are the 4 types of joint receptors?
Describe them

Answer 5

Golgi-Mazzoni Corpuscles
- Located on the edge surfaces of synovial joints
- Active at onset and termination of stretch and signal velocity and acceleration
- Fast adapting

Pacinian Corpuscles:
Located on periosteum near articular attachments. Active at onset & termination of movement, signal velocity & acceleration (fast adapting).

Ruffini endings:
Located on the inner surfaces of joint capsule, activated by stretch & tactile stimulation. Active when joint is at rest & in motion. Helps signal speed of movement (slow adapting)
Detects INTERNAL FLUID PRESSURE

Golgi type endings:
Located in joint ligaments, axon endings intertwined with ligament collagen fibres, physically deforming when ligament is stretched. Active at extreme range of joint position. Force detection (slow adapting)

Question 6

Where are free nerve endings located?
What activates them?

Answer 6

Located in joint capsule and connective tissue

Activated by mechanical or chemical irritation

SLOW ADAPTING

Question 7

What is Efference Copy?

Answer 7

Internal copy of a motor command, movement prediction and its resulting sensations
–> Estimation of the expected or predicted sensory consequence based on past experience

Provides Feedforward sensory information

Enables the CNS brain areas to alter, suppress or change subsequent responses in movement