Notes in 4- Sensory R & R

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Published	02/10/2024	{{c1::Sensory Receptors}} are receptors that inform the brain about the internal and external environment, they are nerve ending with specialized non-…
Published	02/10/2024	{{c1::Sensory modality}} is the stimulus type that activates a particular receptore.g. touch, pressure, joint angle, pain.An {{c1::adequate stimulus}}…
Published	02/10/2024	Sensory receptor transduction involves opening or closing ion channels.An adequate stimulus causes a graded membrane potential change which is called …
Published	02/10/2024	The receptor potential is graded by {{c1::stimulus intensity}}Stimulus → ion flow (ligand-gated) → hit threshold → depolarisation (voltage-gated) → ac…
Published	02/10/2024	A larger stimulus → larger receptor potential → higher frequency of action potentialsThis is called {{c1::frequency coding of stimulus intensity}}
Published	02/10/2024	In some mechanoreceptors that are going through continuous mechanical stimulation, you see a drop off in AP frequency.This process is called {{c1::Ada…
Published	02/10/2024	Mechanoreceptors are divided into two types based on their adapting capabilities:1- {{c1::Rapidly/Moderately-adapting receptors}}e.g. Pacinian corpusc…
Published	02/10/2024	Why are sensory neurons like Nociceptor not able to adapt?
Published	02/10/2024	The {{c1::Pacinian corpuscle}} is the best understood mechanoreceptor:• It comprises of a myelinated nerve with a naked nerve ending, enclosed by a co…
Published	02/10/2024	Explain how a Pacinian corpuscle responds to a mechanical stimulus? and what happens as the stimulus is withdrawn?
Published	02/10/2024	The function of a Pacinian corpuscle depends on a non-neural accessory structure called a capsule lamellaeExplain why?
Published	02/10/2024	A {{c1::receptive field}} is a specific area where a somatic sensory neuron is activated by a stimuli.Touch-sensitive neurons have a more defined area…
Published	02/10/2024	The {{c1::Two point discrimination test}} is a test to measure our ability to tell two points apart on the skin.You increase distance between points a…
Published	02/10/2024	Sensory neurons with neighbouring receptive fields may exhibit {{c1::neuronal convergence}}This allows the sub-threshold stimuli coming from the diffe…
Published	02/10/2024	High neuronal converge + large secondary receptive field → {{c1::insensitive area}}e.g. back and limbs → 2 point threshold → 2 cmLow neuronal con…
Published	02/10/2024	{{c1::Acuity}} is the ability to locate a stimulus on the skin and differentiate it from another nearby stimulus.It is inversely proportional to the l…
Published	02/10/2024	{{c1::Lateral inhibition}} helps you locate the area of stimulus precisely e.g. pin on your fingerPathway closest to the stimulus inhibits n…
Published	02/10/2024	Why is lateral inhibition widespread in the spinal cord and pathways with high precision information? e.g. touch and skin movement
Published	02/10/2024	All the sensory info from the body goes to the brain:Spinal Cord → Thalamus → Somatosensory cortexIn the somatosensory cortex, there is a distorted bo…
Published	02/10/2024	{{c1::Proprioceptors}} are mechanoreceptors that signal body or limb position.They include:1- {{c2::Muscle spindles}} → muscle length & rate …
Published	02/10/2024	How do proprioceptors work?
Published	02/10/2024	{{c1::Kinaesthesia}} is awareness of the position and movement of the parts of the body by means of sensory organs (proprioceptors) in the muscles and…
Published	02/10/2024	Most Skeletal muscle fibers are {{c1::extrafusal}} muscle fibres, but some specialized few have their own sensory and motor innervation and are called…
Published	02/10/2024	Muscle spindles have {{c1::sensory neurons}} in the middle of the intrafusal fiber and {{c1::gamma motor neurons}} on the ends of the intrafusal fiber…
Published	02/10/2024	Two types of intrafusal fibre make up the muscle spindle:1- {{c1::Nuclear bag fibres}} - bag of nuclei collected together2- {{c1::Nuclear chain fibres…
Published	02/10/2024	Alpha motor neurons vs Gamma motor neuronsWhat are the differences?
Published	02/10/2024	Describe this graph and tell me:What happens to spindle AP discharge if a muscle lengthens from L0 to L1 ?
Published	02/10/2024	How does muscle length indicate the spindle AP discharge?i.e. agonist contracting, antagonist relaxing, joint moving
Published	02/10/2024	Information from {{c1::Spindle}} and {{c1::joint}} receptors inform the brain about joint position.
Published	02/10/2024	{{c1::Golgi tendon organ (GTO)}} are proprioceptors that monitor muscle tension.They initiate APs in Group Ib afferentsNerve endings of GTO …
Published	02/10/2024	How does the Golgi tendon organ (GTO) work?
Published	02/10/2024	Why do GTOs fire APs in an isometric contraction but muscle spindles do not fire APs?
Published	02/10/2024	{{c1::Alpha-Gamma coactivation}} is the process of excitation of gamma motor neurons and alpha motor neurons at the same time.Alpha motor neurons fire…
Published	02/10/2024	What happens when alpha motor neurons fire without gamma motor neurons?
Published	02/10/2024	What happens when alpha motor neurons and gamma motor neurons fire together?
Published	02/10/2024	{{c1::Annulospiral endings}} are Ia afferent nerves or primary endings that wrap around the centre in the muscle spindle.{{c1::Flower-s…
Published	02/10/2024	{{c1::Spindle 1a afferents}} are neurons that report muscle shortening to the brain in the muscle spindle. {{c1::Gamma motor neurons}} are neuron…
Published	02/10/2024	A {{c1::monosynaptic reflex}} is a reflex that has a single synapse between the afferent and efferent neuronsA {{c1::polysynaptic reflex}} is a reflex…
Published	02/10/2024	{{c1::Spinal reflexes}} are simple building blocks integrated into the voluntary control of movements, they can occur without brain input.The simplest…
Published	02/10/2024	{{c1::Spindles}} are tonically active and firing even when muscle is relaxed, So alpha neurons receive tonic input from muscle spindle and fire c…
Published	02/10/2024	Stretch reflex:e.g. patellar tendonSharp tap to patella → stretches muscle spindle → fires AP through Ia afferent neuron→ Alpha motor neuron receives …
Published	02/10/2024	Explain a stretch reflexi.e. in the arm or patellar tendon
Published	02/10/2024	Spindle sensory afferents make 3 types of connections: (two in spinal cord & one in brain)What are they?
Published	02/10/2024	{{c1::Reciprocal Inhibition}} is when spindle afferents activate interneurons in the spinal cord which inhibits alpha motor neurons&nbs…
Published	02/10/2024	The {{c1::inverse stretch reflex or Golgi-tendon organ reflex or Clasp-knife reflex}} is a reflex caused by 1b afferent from the Golgi Tendon Organs (…
Published	02/10/2024	Describe how GTO reflex works
Published	02/10/2024	{{c1::Flexor/Withdrawal reflexes}} are reflexes that use info from nociceptors (pain receptors) in skin, muscles and joints.They are polysynaptic and …
Published	02/10/2024	Explain the process of flexor/withdrawal reflex when you step on a lego
Published	02/10/2024	Why is the flexor and crossed extensor reflex slower than the stretch reflex?
Published	02/10/2024	Each alpha motor neuron is connected to more than {{c1::10,000}} synapses, many from the thalamus and cortex, causing EPSPs and IPSPsThey have to inte…
Published	02/10/2024	Reflexes can be over-ridden by voluntary input from the CNS e.g. if you're holding a child you can override Golgi tendon reflexHow does that work…
Published	02/10/2024	Stretch reflex can be overridden.e.g. patellar reflex can be hard to evoke in anxious patients because :strong descending inhibition hyperpolarizes al…
Published	02/10/2024	Why do neurologists use a technique called Jendrassik manoevure, where you interlock your fingers in front of your chest and pull hard, to test the&nb…
Published	02/10/2024	Why does the absence of a stretch reflex need not be evidence of any nerve damage?
Published	02/10/2024	Withdrawal reflex can be overriddene.g. holding on hot soup for brief amount of time to move leg away so you don't burn your legActivating neurons vol…
Published	02/10/2024	What is the clinical relevance of reflexes?
Published	02/10/2024	In the {{c1::Stretch reflex}}, spindle input is highly localised and affects alpha motor neurons at one or two spinal segments.In the {{c1::Withdrawal…
Published	02/10/2024	{{c1::Facilitation}} is a process through which a more powerful pain stimuli, causes greater segmental spread, more muscles are recruited and the resp…
Published	02/10/2024	Why would the biceps stretch reflex become greatly exaggerated after you burn your hand on a hot plate?
Published	02/10/2024	How does facilitation work?
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