Sensory Physiology and motor function Flashcards
What do the senses do?
- Information on your surroundings
- Processed in the CNS
Mechanoreceptors
- ear
- muscle and joints
- skin and viscera
- cardiovascular
Thermoreceptors
skin and CNS
Nociceptors
Respond to stimuli that result in sensation of pain
Stages of sense and function
- Stimulus
- Receptor
- Change in membrane potential
- Generation of action potential
- Transmission to CNS
- Integration of information by CNS
Sensory unit
single afferent neuron and all of its
receptor endings
Receptors of sensory neurones may have
- Neuron with free nerve endings
- Neuron with encapsulated ending
- Specialised receptor cells closely associated
with neuron
Enviromental change impacting sensory receptors
- Cause a change in membrane potential in receptor
- Generated potential is greaded
- Reach threashold to cause action potential
- Goes to the brain via ascending fibres, afferent nerve fibres
Stimulus threshold
- Stronger stimulus larger graded receptor potential
- More frequent action potentials
- Therefore more neurotransmitter released
- AP not graded
Receptor field
- Region of space where the presence of a
stimulus will induce the production of a
signal in that neuron - Smaller the receptive fields, the more
accurate a representation of the stimulus - Brain cant differentiate between 2 stimulus in same receptive field
Somatic nervous system
- Perception of touch, temperature, body position,pain
- Received from receptors within the skin,
muscles, and joints - Responses voluntary AND involuntary
Free nerve endings
Temperature,
noxious stimuli, hair
movement
Somatosensory pathways
- Take the message
to the spinal cord and brain - Three neurones which synapse in the spinal cord and in thalamus
Dorsal column lemniscal
- Fine touch, vibration and
position
Spinothalamic
crude touch temperature, and
pain
Motor pathways
- 2 neurons which synapse with each
other in the spinal cord - Terminate at the neuromuscular
junction with skeletal muscle
Reflexes
- Sensors detect external stimuli and sensory neurons sends an impulse to the spinal cord
- Interneurons (spine) relay the information immediately back to the motor neurons which causes movement
Stretch Reflex
- Muscle fibres surrounded by a capsule
inside skeletal muscle causing contraction - Proprioceptors sense muscle length (stretch)
and activate sensory neurones
Stages of Streach reflex
1) Streaching of muscle stimulate muscle spindles
2) Activation of sensory neurone
3) Information processed by motor neurone
4) Activation of motor neurone
5) Contraction of muscle
Golgi tendon organs
- Axons synapse onto inhibitory spinal interneurons
- These inhibit α motorneurones (using GABA/glycine) and reduce muscle contraction
- Regulates muscle tension within a normal range
- Important for fine motor skills
Basal ganglia
Below cortex
- Important for initiation, sequencing of
behaviors - Starting and finishing movements
- Disorder is parkinson’s
