21. Somatosensory system Flashcards
Where is somatosensation and what is it? (Somatosensory system B&B)
- Occurs all over the body
- Tells us what is happening in the body and what is happening in the environment
What does an increase in receptors lead to? (Somatosensory system B&B)
An increase in sensitivity to stimulation
What are the two types of skin humans have? (Somatosensory system B&B)
- Hairy skin = low sensitivity
- Glabrous skin = high sensitivity
What test can reveal the differences in skin sensitivity? (Somatosensory system B&B)
Two point discrimination test
What are the three types of somatosensory perception? (Somatosensory system B&B)
- Nocioception
- Hapsis
- Proprioception
What are nocioceptors? (Somatosensory system B&B)
- Free nerve endings
- Occurs due to dendrite activity
- Damage to dendrites releases chemicals that produce action potentials
What are haptic receptors? (Somatosensory system B&B)
- Dendrites attached to hair/connective tissue
- Mechanical stimulation leads to action potentials firing
What are proprioceptors? (Somatosensory system B&B)
Triggered by movement that stretch the receptor, stimulating dendrite activity, allowing an action potential to fire
What is the function of the rapidly adapting receptors? (Somatosensory system B&B)
Body sensory receptor that responds briefly to the beginning and end of a stimulus in the body
What is the function of the slowly adapting receptors? (Somatosensory system B&B)
Body sensory receptor that responds as long as the sensory stimulus is on the body
What is the dorsal root ganglion neuron? (Somatosensory system B&B)
A cluster of nerve cell bodies in the dorsal root of the spinal nerve
What does myelin allow for? (Somatosensory system B&B)
Natural impulses to travel faster as they jump from node to node
What was found through patient G.O? (Somatosensory system B&B)
- Lost sensation due to peripheral neuropathy
- Motor cortex was not lost
- Simple actions required visual feedback (almost like everything was numb)
What is differentiation? (Somatosensory system B&B)
The loss of incoming sensory input, usually due to damage to the sensory fibres
What are the two pathways to the brain? (Somatosensory system B&B)
- Dorsal spinothalamic tract
- Ventro spinothalamic tract
What is the dorsal spinothalamic tract route? (Somatosensory system B&B)
- Carries haptic and prophoceptive information
- Dorsal ganglion
- Spinal cord
- Dorsal column nuclei
- Cross over
- Project up the medial lemniscus pathway
- Project to somatosensory cortex
What is the ventral spinothalamic tract route? (Somatosensory system B&B)
- Carries nocioceptive information
- Dorsal root ganglion
- Spinal cord
- Cross over
- Axons from contralateral spinal cord = medial lemniscus
- Axons from thalamus = project to the somatosensory cortex
What is one form of spinal reflex? (Somatosensory system B&B)
Monosynaptic reflex e.g. kneww jerk reflex
What does the vestibular system contribute to? (Somatosensory system B&B)
Balance and spatial orientation
What does each ear have? (Somatosensory system B&B)
Vestibular organ (comprised of three semi-circular canals and otolith organs)
What happens when the head moves? (Somatosensory system B&B)
- Endolymph (fluid) pushes against hair cells
- Cilia bend
- Direction of cilia determines polarisation or hyperpolarisation
- Response to angular acceleration
What happens when the head is tilted? (Somatosensory system B&B)
- Gelatin and otoconia push against hair cells
- Action potential firing rate altered
- In response to linear acceleration
What does the primary somatosensory cortex do? (Somatosensory system B&B)
Receives projections from the thalamus and begins the process of constructing perceptions
What does the secondary somatosensory cortex do? (Somatosensory system B&B)
Continues the construction of perceptions and projects onto the frontal cortex
Why is reorganisational possible after damage to the somatosensory cortex? (Somatosensory system B&B)
- High levels of plasticity
- E.g. if there is damage to the arm, the face may be hyper sensitive
- Remapping process
