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PHYSIOLOGY STUDY - Minitest 2.docx

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Physiology 1021

Hypothalamic - Limbic integration o Memory, emotions, behaviour Amygdala emotions Hippocampus memory Hypothalamus behaviour Olfactory Stimuli - Smell, bypasses everything and goes straight to limbic system Olfactory System - Total area is approximately 2.5 cm/sq. inch in each nasal cavity - Life of sensory cells is approximately 30 days, and approximately 1% is lost yearly - 5 million receptors with 1000 different types - 3 characteristics of substance; volatile, water and lipid soluble Mucus made of water and fats Motor Systems - Functions: o Two most important Provide organism with the ability to move around the world it lives in The ability to move its own body - Movement : o To perform a movement we need to know: Which muscle to use learned The present length (muscle spindles) of the muscle it will move 1a afferent neuron The present tension (Golgi Tendon Organ) in the muscle it will move 1b afferent neuron - Proprioceptors: o Muscle spindle and Golgi tendon organ Muscle spindle parallel with fibres Tendon in series with muscle and tendon; information about tension within the muscle - Reflexes and Local Motor Circuits o Stretch helps in compensation for additional loads o GTO protective mechanism o Reflex; involuntary response to a stimulus which requires the integrity of the nervous system o Result of a reflex may either be a contraction or secretion o Reflex activity may involve skeletal, cardiac or smooth muscle o A reflex arc involves: A receptor specialized sensory nerve ending An afferent neuron propagate sensory impulses A synapse A motor neuron - innervates the effector organ An effector muscle or gland - Between the application of stimulus and the beginning of the response is a lapse of time, called reflex latency - Even the simplest of reflexes are influenced by the CNS - The coordination of bodily movements involve two or more sets of muscles Mono and Poly-synaptic Reflexes - A mono-synaptic reflex has a single synapse between the afferent and efferent neurons ( 1a afferent neuron) - A poly-synaptic reflex has two or more synapses (1b afferent neuron) Alpha-gamma Co-activation - Process by which alpha motor neurons and gamma neurons are activated simultaneously - If gamma motor axons are cut, the spindle loses activity when a muscle contracts: o Alpha motor neuron fires o Muscle contracts o Less stretch on centre of intrafusal fibres o Firing rate of spindle sensory neuron decreases - Alpha-gamma co-activation maintains spindle function when it contracts o Alpha motor neurons fires and gamma motor neuron fires o Muscle contracts o Stretch on centres of intrafusal fibres unchanged; firing rate of afferent neuron remains the constant Gamma controls muscle spindle Take Home Message: - Reflex arc afferent neuron synaptic contact in spinal cord (CNS) motor neuron effector - Mono-synaptic stretch reflex - Poly-synaptic GTO reflex - Alpha-gamma co-activation simultaneously activates skeletal fibre and muscle causing both to contract - Alpha-gamma co-activation increases sensitivity of muscle spindle and maintains afferent information to CSN about muscle lengthCorticospinal Tract - Primary pathway the leaves the area of the motor cortex to innervate motor neurons in the spinal cord - Starts in cortex ends in spinal cord - Major highway is lateral corticospinal tract Take Home Message: - Motor cortex frontal lobe (precentral gyrus) - Motor homunculus somatopically organized - Organization in motor cortex due to cerebral representation of body areas having dense and small motor neurons - Corticospinal tract lateral; crossed- used mainly for fine and gross motor movements, ventral; uncrossed; used for gross movements - direct pathways to alpha motor neurons - Babinski Sign (reflex) used to assess corticospinal tract damage - Planning movement (frontal lobe) integrate
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