Sensory and Motor Systems Flashcards
Define sensation (1)
Sensation is the conscious or subconscious awareness of changes in the external or internal environment
Name the Sensory modalities (2)
- General senses
▪ Somatic senses
▪ Visceral sensations - Special senses
▪ Taste
▪ Smell
▪ Hearing and Equilibrium
▪ Vision
- Special senses receptors are located within sensory organs
Explain the series of events that leads to sensation (4)
- Stimulation of the sensory receptor (PNS)
- Transduction of the stimulus into neural signals
- Generation of nerve impulses and propagation to the CNS
- Integration by the CNS
Describe the neuron organisation of the sensory systems (order neurons) (3)
1st order neuron: from sensory receptor to spinal cord - 1st synapse
2nd order neuron: from spinal cord to thalamus
3rd order neuron: from thalamus to cerebral cortex(sensory)
Explain the differnet types of sensory receptors (3)
1st order sensory neuron w/ free nerve endings: detects stimuli (eg cold) -> nerve impulse -> propagated along axon to CNS
1st order sensory neuron w/ encapsulated nerve endings: detects stimuli (eg vibration)nerve impulse -> propagated along axon to CNS
Sensory receptor synapses w/ 1st order sensory neuron: detects stimuli/receptor potential -> excretes neurotransmitters-> nerve impulse -> propagated along axon to CNS
Where are somatosensory receptors and what do they do? (2)
▪ Somatosensory receptors are embedded in the skin, mucous membranes, skeletal muscles, tendons and joints
▪ They detect touch, pressure, stretching, temperature, pain, and vibrations.
Name + explain the some types of somatosensory receptors (5)
types:
- Tactile disc (type1): continuous touch
- Meissner corpuscle - touch onset low freq vibration
-Ruiffini corpuscle (type2) - skin stretch + pressure
-hair root plexus - hair disturbance
- pacinian corpuscle - high freq vibration
Where are propioceptors receptors and what do they do? (3)
-type of somatosensory r’s
▪ Proprioceptors are embedded in muscles and tendons
▪ They inform about muscle contraction, tension at tendons, the position of joints
▪ They include muscle spindles and tendon organs
Explain the Somatosensory pathways (4)
Somatosensory impulses ascend to the somatosensory cortex via three tracts:
1. Dorsal columns tract
2. Spinothalamic tract
3. Trigeminothalamic tract
Proprioceptive information reaches the cerebellum via the spinocerebellar tracts (not consciously perceived)
Describe the dorsal columns tract (4)
- transmit info about touch, pressure, vibration + proprioception from limbs, trunk, neck and posterior part of the head
- 1st order projects from sensory receptor to dorsal column nuclei (nucleus gracilis and cuneatus)
- 2nd order neuron decussates + project from dorsal column nuclei to ventral posterior thalamus (CROSSING OVER -> to transmit info)
-3rd order neuron projects from thalamus to primary somatosensory cortex
Describe the spinothalamic tract (4)
Transmits information about pain, temperature, itch, and tickle from the limbs, truck, neck, and posterior part of the head
- 1st order neuron projects from sensory r to dorsal horn of the spinal cord
-2nd order neuron decussates and projects from dorsal horn to VPN the thalamus
-3rd order neuron projects from the thalamus to the primary somatosensory cortex
Describe the Trigeminothalamic tract (4)
Transmit somatosensory information from the face, oral and nasal cavities and teeth.
-1st neuron projects from the sensory receptor to either the pons or the medulla.
-2nd order neurons decussate and project to VPN of the thalamus
-3rd neurons project from the thalamus to the primary somatosensory cortex
Explain the Sensory homunculus (4)
▪ The primary somatosensory cortex is located in the postcentral gyrus of the parietal lobe
▪ Each area receives sensory inputs from a different part of the body
▪ This differential representation is directly related to the density of sensory receptors in each body part
▪ It creates a distorted representation of the body known as the sensory homunculus.
What is neurosyphilis? (5)
▪ Syphilis is a sexually transmitted disease
▪ It is caused by the bacterium Treponema pallidum
▪ In third stage: affects the CNS
▪ Causes progressive degeneration of the posterior portions of the spinal cord
▪ Somatic sensations are lost.
Explain the Olfactory epithelium components (3) + formation of cranial nerve 1 (3) -CONFUSED
Smell:
- olfactory receptor cells = bipolar, meaning -> that they have two projections from their cell body:
1) dendrite extends to the surface of olfactory epithelium + expands at the epithelial surface = becomes olfactory bulb (dendrite surface)
- bulb contains cilia r’s for odour
- each r has axon extending from its basal surface to the basal surface of the olfactory cells
-located directly inferior of the cribiform plate + ethmoid bone (makes up roofy component of the nasal cavity)
2) whilst projecting to the cell body, the axon combine w/receptor cell axons = nerve bundle fibre/ olfactory nerve/cranial nerve 1
3) where it synapses, = glomeruli
-generally mitral cells responsible for processing info from the glomerular unit into the olfactory tract which will then spread along to go to the olfactory nerve
Walk through the Olfactory pathway - CONFUSED (10/11)
1) axons projecting from olfactory r’s
2) olfactory nerve
3) terminate at the olfactory bulb (main relay station for this pathway)
4) glomeruli
5) mitral relay cells
6) 2nd order neuron
7) olfactory tract
8) olfactory cortex
9) medial frontal lobe sulk - olfactory groove
10) medial dorsal nucleus (thalamus) from the olfactory tubercle -> to orbitofrontal cortex
Explain the 3 order olfactory pathway (3)
1) olfactory r synapses with olfactory bulb
2) olfactory tubercle-> thalamus MDN
3) thalamus -> orbitofrontal cortex
What is hyposmia? (3)
▪ Reduced ability to smell
Caused by aging:
▪ 50% over 65yo
▪ 75% over 80yo
Neurological changes:
▪ Head injury
▪ Alzheimer’s disease
▪ Parkinson’s disease
▪ Drugs (antihistamines, analgesics, steroids)
▪ Smoking
- COVID
What is the anatomy of taste papillae and buds? (5)
- surface of the tongue covered by a load of visible small bumps = papillae (vallate, foliate, fungiform) -TASTEBUDS on them
each tastebud:
- made-up of taste receptors cells
- supporting + basal cells = eventually taste receptor
-taste cells = lifespan of approx 2wks + the basal cells replace dying taste cells
- taste cells have microvilli = open into the taste pool -> where chemicals from the food interacts w/receptors + the taste cells
What are the 5 gustatory sensations? (5)
sweet
salty
sour
bitter
umami
Walk through the Gustatory Pathway (4) - CONFUSED
3 order neurons:
-tongue innervated by 3 cranial nerves (facial, vagal, glossopharyngeal)
1) all 3 nerves enter at the medulla
2) then sent to VPM - this is in thalamus
3) VPM - gustatory cortex
Gustatory cortex
I
VPM
I
Gustatory nucleus
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Anterior Tongue, Posterior tongue, Epiglottis