Sensory and motor system Flashcards
Where in the body is somatosensation?
All over the body
What information does the somatosensory system give us?
Tells us what body is up to and what’s going on in environment by providing bodily sensations such as touch, temp, pain, position in space, movement of joints
What does an increased number of receptors mean?
Increased sensitivity to stimulation
Skin is the largest sensory organ. What are the two types of skin that humans have?
- Hairy skin - relatively low sensitivity
- Glabrous skin - doesn’t have hair follicles but contains large number of sensory receptors, sensitive to wide range of stimuli
What is the name of the test that reveals differences in skin sensitivity across the body?
Two point-discrimination test
Which part of the body is the most sensitive? Why is this?
Fingertips
Higher density of mechanoreceptors
Receptors with small receptive fields
Brain devotes a lot of resources
What are the three main types of somatosensory receptors and what do they perceive?
- Nocioception - perception of pain and temperature
- Napsis - perception of fine touch and pressure (e.g. grasp, manipulate)
- Proprioception - perception of the location and movement of the body
Fill in the gaps about nocioreceptors…
1.Free nerve ______
2. Sharp/____ pain and _____/cold
3. Damage to _____ or surrounding cells release ________ that stimulate dendrite and produces an action potential
- endings
- dull, heat
- dendrite, chemicals
Fill in the gaps about haptic receptors…
1. Dendrite attached to _____, connective tissue or dendrite encased in ______ of tissue
2. Distinguish _____, pull, vibration, flutter, ________
3. _______ stimulation produces action potential
4. Composition of ______ determines the type of _________ energy conducted
- hair, capsule
- touch, indentation
- Mechanical
- capsule, mechanical
Fill in the gaps about proprioceptors…
Movements _____the receptors to _______ stimulate dendrites and produces an action potential
stretch, mechanically
Somatosensory receptors tell us what two things about a sensory event?
- When it occurs
- Whether it is still occurring
What is a rapidly adapting receptor?
Body sensory receptor that responds briefly to the beginning and end of a stimulus on the body
What is a slowly adapting receptor?
Body sensory receptor that responds as long as a sensory stimulus is on the body
What stimulus do slow adapting receptors signal the presence of? Give an example.
Long sustained stimulus
e.g. pain, long pinch
What stimuli do rapid adapting receptors signal the presence of? Give an example.
Motions of object on skin, gives good response to repeated stimuli
e.g. vibration, tickle
Fill in the gaps about the Dorsal-Root Ganglion Neurons…
1. The ______ and _____ are continuous and carry ______ information from the skin to the CNS via the ______ ______
2. The tip of the ______ is responsive to ______ stimulation
3. Each spinal cord _____ has _____ dorsal-root ganglion on each side that contains many dorsal-root ganglion _______
4. In the spinal cord, the _____ of these neurons may _____ onto other neurons or _____ up to the brain
- dendrite, axon, sensory, spinal cord
- dendrite, sensory
- segment, one, neurons
- axons, synapse, continue
What different things do proprioceptive and haptic neurons carry info about? Describe their axons.
Location and movement (P) and touch and pressure (H)
Large, well-myelinated axons (fast)
What different things do nocioceptive neurons carry info about? Describe their axons.
Pain and temp info
Small axons with little or no myelination (slow)
The term deafferentiation means l____ of incoming s____ i____ usually due to damage to s____ f____, also loss of any a____ input to a structure
Loss of incoming sensory input usually due to damage to sensory fibres, also loss of any afferent input to a structure
Fill in the gaps about the dorsal spinothalamic tract (somatosensory pathway to the brain)…
1. Carries ______ and ________ information
2. Axons from the ______-______ _______ neurons enter the spinal cord and ascend ________ until they synapse in the dorsal column ______ (base of brain)
3. Axons from the dorsal column nuclei cross over to the ______ side of the brain and project up through the ________ as part of a pathway called the ______ _______
4. Axons synapse with neurons located in the ________ nucleus of the ______, which projects to the ________ cortex and ________ cortex
- haptic, proprioceptive
- dorsal-root ganglion, ipsilaterally, nuclei
- opposite, brainstem, medial, lemniscus
- ventrolateral, thalamus, somatosensory, motor
Fill in the gaps about the ventral (or anterior) spinothalamic tract (somatosensory pathway to the brain)…
1. Carries ________ information
2. Axons from the dorsal-root ganglion neurons enter the _____ ____ and _______ onto neurons in the ______ horn. These ‘___ order’ neurons, in turn send their axons to the contralateral side.
3. Axons from ________ spinal cord then ______ to the brain where they join with other axons forming the ______ lemniscus, eventually synapsing with neurons located in the ventrolateral nucleus of the ________
4. Neurons from the ______ then project to the ________ cortex
- nociceptive
- spinal cord, synapse, posterior, 2nd
- contralateral, ascend, medial, thalamus
- thalamus, somatosensory
What are the two separate pathways that convey somatosensory information?
What does this arrangement mean?
1. H____-p____
2. N____
U____ spinal-cord damage results in distinctive s____ losses to both s____ of the body b____ the site of injury
- Haptic-proprioceptive
- Nocioceptive
Unilateral spinal-cord damage results in distinctive sensory losses to both sides of the body below the site of injury
What is a monosynaptic reflex? Give an example
A reflex requiring one synapse between sensory input and movement
e.g. knee-jerk reflex
The vestibular system is a s____ system that comprises of a set of r____ in each i____ e____ that respond to body p____ and the m____ of the h____
Somatosensory system that comprises of a set of receptors in each inner ear that respond to body position and the movement of the head
Each vestibular organ is made up of what two groups of receptors?
1. T____ s____ c____
2. O____ o____
- Three semicircular canals (positioned at right angles to eachother)
- Otolith organs (utricle and saccule)
What are the two functions of vestibular organs?
1. Tells us the position of the b____ in relation to g____
2. Signals changes in the d____ and s____ of h____ m____
- Tells us the position of the body in relation to gravity
- Signals changes in the direction and speed of head movements
Fill in the gaps about the vestibular system and balance… (pt1)
1. When the head moves, ____ (endolymph) located within the _______ canals pushes against _____ cells, which causes bending of the _____ located on top of the hair cells
2. Responds to ‘_______ ________’
3. Bending of _____ leads to ________ potentials in the hair cells and ______ potentials in the cells forming the vestibular nerve
4. The direction in which the cilia are bent determines whether the hair cell becomes ________ or ________
- fluid, semicircular, hair, cilia
- angular acceleration
- cilia, receptor, action
- depolarised, hyperpolarised
Fill in the gaps about the vestibular system and balance… (pt2)
1. The u_____le and s_____le also contain h____ cells, which are embedded within a gelatin-like substance that contains small crystals of c______ carbonate called otoconia
2. Responds to ‘l_____ a________’
3. When the head is t_____, the gelatin and otoconia p____ against the hair cells, which alters the r____ of action potentials in cells that form the vestibular nerve
- utricle, saccule, hair, calcium
- linear acceleration
- tilted, push, rate
What does the somatosensory cortex do?
Integrates info from all over the body - temp, shape, texture, sense of space
What are the two main somatosensory areas in the cortex?
- Primary somatosensory cortex - receives projections from thalamus, begins process of constructing perceptions from somatosensory info
- Secondary somatosensory cortex - located behind PSC, continues construction of p-erceptions, projects to frontal cortex
Wilder Penfield (1930s) stimulated the cortical surface with large diameter electrodes and recorded patient responses. What did these original studies suggest?
There was a single ‘somatosensory homunculus’-representation of human body in cortex
What four separate somatosensory homunculi did Jon Kaas (1980s) find?
- Area 3a - muscles
- Area 3b - skin (slow)
- Area 1 - skin (fast)
- Area 2 - joints, pressure
What does damage to primary somatosensory cortex result in?
Impairment in pressure sensitivity, proprioception, hapsis, simple movements
What is the term for reorganisation following damage?
Plasticity (The ability of the brain to reorganize neural pathways following damage, new experiences, learning, memory formation, etc.)
