week 3 - sensory pathways & somatic nervous system

Receptor adaptation

When most receptors adapt to constant stimulus action → receptor potential magnitude ↓ over time

Tonic receptors

Receptors that adapt slowly, continue to respond to a stimulus (eg. pain receptors)

Phasic receptors

Receptors that adapt quickly, respond to changes in stimulus (eg. pressure receptors)

Labelled line

The specific area of the body (or environment) monitored by a single sensory neuron

Receptive field

Receptors for mechanical distortion, types:

• tactile (touch, pressure, vibration)

• Baroreceptors (pressure, eg. Blood vessels)

• Proprioceptors (position of joints & muscles)

Thermoreceptors

Receptors for temperature

• two types: warm & cold

• Temperature changes dented by hypothalamus

• Fast-adapting phasic receptors (respond strongly to changes in temp)

Nociceptors

Pain receptors.

• associated with behavioural & emotional responses (hypothalamus & limbic system)

• Fast pain → mechanical/thermal, sharp, localised, A-delta fibres

• Slow pain → polymodal, dull/aching, poorly localised, C fibres

Chemoreceptors

Receptors detecting specific chemical substances in body/environment, convert info into nerve impulses

How is stimulus intensity determined?

1. Frequency of action AC

2. Number of receptors activated

What are the three orders of sensory neurons?

1st order: PNS → CNS (afferent neuron)

2nd order: Spinal cord/brainstem → thalamus

3rd order: Thalamus → cerebral cortex

How is stimulus location identified?

By which receptive field is stimulated, smaller receptive field = more precise

How does neuron activity influence muscle contraction strength?

1. Motor unit recruitment

2. Frequency of AC (tetanus in muscle fibres)