Movement Circuits

Question 1

The physiological functions of the spinal cord are

Answer 1

Initial processing of somatosensory (afferent) input by CNS

Final processing of motor (efferent) output by CNS

Question 2

Neurons in sensory systems signal events by a combination of

Answer 2

Rate- frequency of APs

Spatial- arrangement

Temporal- timing of AP

Codes

Question 3

When high spatial resolution required

Answer 3

Low convergence

Eg cones and bipolar cells in retina

Question 4

Detection of weak signals required

Answer 4

High convergence

Eg Rods and bipolar cells

Question 5

When input is used for complex/multiple functions

Answer 5

High divergence

Eg. Vestibular-ocular reflex

Question 6

1st order sensory receptors

Answer 6

Transduce energy from the environment

Two types: one found in most body parts, one in sense organs (taste, equilibrium and hearing)

Question 7

Adequate stimulus

Answer 7

Lowest response threshold

Question 8

Mechanisms of sensory stimulus discrimination

Answer 8

1) Different types of receptors for the same modality

Eg. Cutaneous mechanosensory receptors
Contact: merkels disc
Deep pressure/vibration: pacinian corpuscle

2) spatial distribution of receptors
Density of mechanoreceptors greater on hands and face
Two point discrimination test

3)windows if response intensity
Old receptors have diff range to hit with little overlap

4) lateral inhibition eg in visual system
Allows brain to extract specific information about object e.g. Edges, exact position
Based on activation pattern of neurons in distributed network of excitatory neurons

Question 9

Lateral inhibition

Answer 9

Excitation passes on to inhibitory neurons which feedback to the first group of neurons to inhibit/reduce firing

Question 10

In the spinal cord, cell bodies are in the _________ and axons project into_____________
These can directly contact ____________ or ______________________

Answer 10

Dorsal root ganglia
Grey matter
Motor neurons
Inhibitory interneurons which can inhibit other types of neuron

Question 11

Mechanosensory information reaches the brain by

Answer 11

A three neuron relay

Dorsal column medial lemniscus pathway

Question 12

Information about pain and temperature reaches the brain by

Answer 12

3 neuron relay

Anterolateral pathway

Question 13

Motor system

Answer 13

Muscles and the neurons that command them

Gives rise to behaviour

Question 14

Lower motor neurons

Answer 14

Motor neurons in the spinal cord

Evidenced by cat in treadmill

Collected in longitudinally organised columns that extend through 1+ segments of the spinal cord

Question 15

Each LMN column contains

Answer 15

The larger, alpha motor neurons: thick axon, high conductance velocity

Smaller, gamma motor neurons: thin axons low conductance velocity

Question 16

Why does destruction of a single ventral root/single spinal nerve not produce paralysis? What does it produce?

Answer 16

Each LMN column extends through more than one segment: each muscle receives motor fibers through more than one ventral root and spinal nerve

Produces paresis (weakness)

Question 17

Motor unit

Answer 17

A single alpha motor neuron and muscle fibres it innervates

Question 18

The simplest reflex responses are based on an interaction between a______________ and _____________.

Examples of ___________ sensory organs:

Answer 18

Motor unit
Proprioceptive sensory input

Muscle spindles: negative feedback, regulation of muscle length

Golgi tendon: negative feedback, regulation of muscle tension

Question 19

Motor neurons innervating _____________ (eg. Postural trunk muscles) are located most _____________, those innervating ________________ (eg. Hands) are located most _________________.

Answer 19

Axial musculature
Medically
Distal musculature
Laterally

Question 20

Golgi tendon organs

Answer 20

Encapsulated afferent nerve endings located at the junction between a muscle and a tendon

Each is innervated by a single group of Ib sensory axons

Regulate muscle tension