SEM 2B Flashcards
What are the two main routes that sensory information is delivered to the brain
Medial lemniscal tract Spinothalamic tract
Example of a polysynaptic reflex
Flexor withdrawl reflex
Which structures sense linear acceleration in the vestibular system
Utricle and saccule
Which type of nociceptive fibre is the fast,myelinated and carrys mechanosensitive and mechanothermal modalities
A(gamma)
What are the bodys proprioceptors
Sensory organs that monitor the position and movement of body parts in space
Which membrane separates the scala tympani from the scalar media
Basilar membrane
What are dermatomes derived from
Somites - each dorsal root ganglion is associated with a partciular somite
What is the cupula
Barrier of gelatinous membrane present in the ampullae that the endolymph acts on during anglular acceleration which causes bending of the stereocilis of the hair cells
What can be said about C nociceptive fibres
Slow Unmyelinated Carry polymodal information
Why is the patella refelx so important
It allows us to maintain body posture as part of the bodies proprioceptive system
Define the somatic nervous system
Division of the peripheral nervous system that innervates the skin, skeletal muscle and joints
What is an extensory muscle
Any muscle whose contraction leads to extension or straightening of the limb
Area of human olfactory epithelium
10 cm squared
What is meant my the parallel after discharge circuit
Many routes, each with different number of synpases )so will take differing ammounts of time. By arriving at different times the initial signal is sustained for longer
What is the role of the inferior colliculus
Attention reflexes, startle repsonses and learned reflexes
At which layer do most outputs leave the motor cortex
III V VI
How are afferents coming from the muscle classified
By roman numerals with I fastest - IV slowest
PLC, DAG and IP3 do what
Raise the intracellular levels of Ca
WHat is a flexor
Any muscle whose contraction leads to bending of the limb
Where to afferent neurons in the ear prject to
Spinal ganglion
Define what is meant by the term reflex
Rapid, involuntary, stereotypes response to sensory stimulus
What is meant by allodynia
Increased central pain sensitivity following a painful stimulus. Due to release of prostaglandins in dorsal horn neurones leading to the sensation of these and other non-nociceptive neurones beging painful to inoxious stimuli
Typically how many neurons does sensory information travel through to reach higher centres
first order - detect simuli transmit to spinal cord second order - relay signal to thalamus third - carry signal from thalamus to cortex
What role does the golgi tendon organ perform in proprioception
Detects a degree of muscle tenstion as a result of contraction. Innervated by Ib sensory afferents and activation of these fibers resulting in the inhibition of alpha motor neurons innervating the same muscle. Acts as a nergative feedback mechanism to prevent damage to muscle
Describe the reception of sour tastes
Ionotrophic H+ in Depol Opening of VGNC Opening of VGCC Vesicles released containing 5-HT, GABA, ATP
What differences may be seen between patients with upper MND and lower MND
Lower: Loss of muscle tone, severe muscle atrophy Upper: Spascitcity due to increased muscle tone resulting in loss of fine motor movement
What are the names of the three canals which measure angular acceleration
Superior, inferior and lateral
What is the role of the stria vascularis
Produces endolymph and actively transports ions in order to maintain the unusual ionic concentrations
Which of the lingual papillae do not contain taste buds
Filliform papillae
All skeletal muscle movements are initiated by which motor neurones
Lower
Which signalling molecule is used as a neurotransmitter it taste reception
ATP
true or false The primary motor cortex resides anterior to the central sulcus and the primary somatosensory cortex lies posterior to the central sulcus
True
Describe the process which occurs when an odorant binds to its specific odorant receptor
Activation of adenylate cyclase ATP –> cAMP Opening of cyclic nucleotide gated ion channel which allows influx of Na and Ca Causes depolarisation Opens ANO2 and chloride moves out (because IC conc of Cl is higher than in other cells) Graded receptor potential If it exceeds threshold at the axon initial segment then will result in action potential firing
Olfactory transduction uses (ALWAYS) which downstream signalling pathway
Golf
Descirbe reception of a bitter/sweet or umami taste
All use GPCR coupled Activation of PLCB Production of Ip3 Rise in intracellular Ca Ca acts on cation selective channel TrpM5 ion channel Deplolarisation Opening of VGNC Further depolarisation Opening of VGCC Release of ATP from vesicles onto afferent neurones
What is the roles of gamma motor neurons in proprioception
Gamma motor stimulates contraction of intrafusal muscles during contraction to ensure the spindle doesnt become slack
Describe the golmeruli of the olfactory bulb
Each glomerulus associated with one odorant receptor protein Basis for information coding
Do inner or outer hair cells show convergence
No
Which tract is responsible for carrying pain and temp information to the thalamus
Spinothalamic tract
What are the four types of lingual paillae
Filliform (most abundant) Foliate (least abundant) Fungifrom (3 apical taste buds) Vallate (back of tounge)
Give an example of a monosynaptic refelc
Patellar
Give an example of a proprioceptor and explain how it works
Muscle spindles are found in most striated muscle and is innervated by type 1a sensory fibres and provide information as to the degree of streching
If which of the compartments would you find endolymph
Scala media
What varies between taste cells
Have different thresholds for different basic tastes
How does the basilar membrane lead to the sensation of sound
Movement of basilar membrane moves the hair cells, causes bending of the stereocilia against the tympanic membrane. Results in tip link streching, opening of K+ channels allowing K+ ions into the cell. Causes depolarisation of the hair cells opening of VGCC Ca in vesicle release
How many sensory epithelia are there in the ear
5 5 vestibular 1 auditory
Which are faster pain fibres or proprioceptive fibres
Proprioceptive fibres
Name given to the outer ear
Pinna
Fill in the blanks about the olfactory system receptor cells Tranduction machinery found ___________ Primary afferent neuron is _________ Axons are ______ and ________ Axons form the ____–
Within the cilia at end of a dendrite Olfactory receptor (axon of) Thin and unmyelinated Olfactory nerve
What is the name give to receptors which respond to noxious stimuli
Nociceptors - afferent nerves with free nerve endings
Describe the basal ganglias role in the initiation of movement
With no initiating cortical input the striatum is tonicallt activating the globus pallidus. Globus pallidus then in-turn inhibits the ventrolateral cortex leading to no signalling of the VLo to layer 6 of the motor cortex. When movement is to be initiated, activation of the striatum via cortical regions causes the inhibition of the globus pallidus. This in turn inhibits the inhibition (so activates) of the VLo which can then signal to the motor cortex to initiate movement
Human hearing range
20-2000Hz
What are the four features of spinal reflexes
Sensory input Fast Involuntary Stereotyped
How many odorant receptor proteins
350
By what three methods does the human ear use to localise sound
Intensity and time taken for sound entering each ear Pinna help localise in vertical plane
Which tract is responsible for carrying mechanoreceptive and proprioceptive information to the thalamus
Medial lemniscal tract
How many taste buds
2000-5000
All involuntary reflex arcs are controlled by which division of the nervous system
Somatic sensory system
Put into order 1) Ossicles move the membrane at the oval membrane 2) Sound waves move the tympanic membrane 3) Movement of the the fluid in the cochlear causes a response in the sensory neuron 4) Tympanic membrane moves the ossicles 5) Motion at the oval window moves fluid in the cochlear
2 4 1 5 3
What are the two cateogries of pain
Fast - A(gamma) fibers sharp and immediate Slow - C delayed longer lasting
Which membrane spearates the scala vestibuli from the scala media
Reissners membrane
What is unusual about the fluid that sits inside the scala media
Similar ion concentrations to intracellular fluid
To which hair cell does 95% of afferent inneration go to
Inner hair cells
During inflammation, mediators such as bradykinin and prostaglandins have what effect on nociception
Lower the threshold for pain reception at the TRPV1 receptors
In addition to the somatosensory cortex which regions of the brain does painful stimuli distinctly activate
Cingulate cortex Insula
How does the flexor (withdrawl) reflex work
Activation of nociceptors results in the activation of excitatory neurons leading to the contraction of flexor muscles Meanwhile inhibitory interneurons cause a relaxation of the extensor muscles
Which pathway carries the location, intensity and modality of painful stimlui to the brain
Sensory discriminative pathway (Spinothalamic tract)
What is the name of the structure involved in sound localusation
Superior olive
2nd order neurones
Cross the midline and ascend in the medial lemniscus
In which on the compartments would you find perilymph
Scala tympani Scala vestibuli
What is the role of the periaqueductal grey
Regualtes pain sensation Simulation of this region be endogenous opiates activates brainstem nuclei that modulate dorsal horn neurone activity
What is the name of the membrane that sits on top of the organ of cortici
Tectroial membrane
Name an example of a molecular pain receptor
Capsaicin TRPV1 receptors is activated by temperatures above 45 deg and by capsaicin
How many rows of inner and outer hair cells
3 outer 1 inner
Recall some of the evidence against the specificity of pain theory
Phantom limb pain Referred pain Placebo effect
What is the name given to the mammalian auditory sensory epithelium
Organ of cortici
Name 5 of the olfactory projections and the effect that they have at each are
Olfactory cortex - conscious smell Hippocampus - olfactory memory Amygdala - emotional responses Reticular formation - visceral responses Hypothalamus - sex and neuroendocrine
Describe how the electro-mechanical transduction works
Sound shifts the stereocilia to right depolarising. This makes hair cells shorter which brings the basilar membrane up. SHifting of sterocilia left causes hyperpolarisation and makes them longer again, left right movement leads to basilar membrane vibrating amplifying the sound
List some of the symptoms of NMS
Weakness Degeneration Paralysis Death usually within 5 years of diagnosis
What and the name given the the three bones which make up the ossicle of the middle ear
Malleus, incus, stapes
What is the motor pool
All of the motor neurones innervating a particular muscle
At which layer do most inputs arrive at the motor cortex
Layer IV
Taste cells are
Chemoreceptors
What is Menieres disease and how is it caused
Imbalance of fluid in the endolymphatic sac causing hearing problems as well as problems with balance
What is the meant by kinaesthesia
Awareness of the position and movements of the body in the space
Where the somatosensory cortex located and what is its role
Lateral postcentral gyrus in pareital lobe Main receptive area for the sense of touch
What is the name of the fluid filled cavity at the base of the canals which contain the sensory epithelium
Ampulla
Describe what happens during the strech/myotactic reflex
Sensory fibres detect muscles stretching Carries information to the spinal cord where it synpases with a motor neurone that sends a signal causing the contraction of the bicep Simult. another connection with an inhibitory interneurone causing the relaxation of the tricep muscle Known as reciprocal inhibition
What is meant by hyperalgesia
Following a painful stimulus - affected area becomes more sensitive to stimuli
Can reflexes be learnt
Yes - pavolivian conditioning
Which pathway signals unpleasantness and enables autonomic activation in response to pain
Affective motivational - no topographic mapping
What can be said about the location of distal muscle motor neurons in the dorsal horn
They will be located more laterally than the motor neurones that innervated proximal/axial muscles
Describe the response to a sensory stimulus just below the patella
Primary afferent nerve fiber relays signal to the spinal cord via the dorsal root ganglion. In the spinal cord it directly synapses with a motor neurone that causes the contraction of the extensor muscles of the leg
3rd order neurons do what
Reverse their topology so the lower body synapses with more medial cortical regions
Describe the pathology of HD
Cell death due to mutant huntingtin leads to degreneration of the striatum - reduces tonic activation of the GP which reduces the inhibition of the VLo leading to activation of the motor cortex. Manifests the initiation of inappropriate, jerky movements - hyperkinesis
How is linear acceleration sensed different to that of angular acceleration
Linear acceleration uses calcium carbonate crystals attached to the hair cells that move in response to changes in position. This relies of the movement of the endolymph to displace the hair cells
What are two types of mechanoreceptor response and how do they differ from each other
Rapidly adapting - Phasic, stop firing even if the stimulus persists Slowly adapting - tonic receptors give information on the persistence of a stimulus and continue to fire throughout
Would stimulation of A(alpha) and A(beta) fibres cause a sensation of pain
No because they are proprioceptive and mechanorecetpive fibres
What is the primary sensory cell in the auditory system
Inner hair cells
Features of the olfactor epithelium
Detects odorants
What are two theories of pain and how do they differ
Specificity - Pain is a distinct sensation detected and transmitted by specific receptors and pathways to distinct regions of the brain Convergence - pain is an integrated but plastic sense that is the result of multiple somatosensory inputs
What type of innervation is recieved by Golgi Tendon organ
Sensory Ib afferents
What does phantom limb pain indicate with regards to nociception
May be centrally represented based on our expectation
What is the otolithic membrane and how does it allow for sensation of angular acceleration
Otolithic membrane is present in the utricle and saccule and consists of a membrane made up of calcareous crystals whose inertial delay triggers the sensory hair cells
What are the two regions of the superior olive, what do they do
Medial SO - low frequency analysis, compares time differences in auditory information Lateral SO - high frequency analysis compares intensity differences
What is the potential between the scala tympani and media
+80Mv
How does the basilar membrane provide the tonotopic mapping of sound
Basilar membrane vibrates as a result of movement of endolymph. The lower the frequency the further yp the basilar membrane it will travel. Thus for different frequencies of sound different regions of the basilar membrane will be maximally dispalced
How are afferents from the skin classified
Letters (sub divided by greek letter) A - fastest C - slowest
Which cranial nerves innervate the tounge
Vagus Glossopharyyngeal Facial
Define the term dermatome
Specific region of skin innervated by each sensory root ganglion
