Extra Reading Notes P2

Extra Reading Notes P2

1. dendrites in brain has projections called dendritic spines. Each spine=contact between axon terminal&dendrite

   • axons give of side branches called collateral. They end in swelling where it meets target cell (axon terminal)
   • outermost layer of nerve trunk is loose aggregate of connective tissue called epineurium. Anchors trunk to adjacent tissue
     • inside axons run in fassicles, and each bundle is surrounded by hard connective tissue(perineurium)
       • inside are more connective tissue=endoneurium

2. symp postganglionic nerve fibres innervate blood vessels and sweat glands

3. Relative refractory period= reduced excitibility. comes after absolute refractory period

   • if sodium pumps are blocked by poison, nerve fibres can conduct impulses only until its ionic gradients are caused to dissapear
     • Sensory transduction activates particular receptors.

4. Larger axons have thicker myelin and so faster conduction

   • Stim nerve trunk through skin, and record summed AP(called compound AP)
     • Graded with stim strength
       • increase in intensity increase ap being larger and excites more axons, until all are excited

5. Axons with highest conduction velocity are Motor and sensory fibres

   • Demyelinating disease diagnose=conduction velocity test
     • 2 types of synaptic trans mission, slow and fast. Ligand gated ion channel =fast, and Glinked protein receptor =slow
       • Fast inhibitory synaptic transmission, NT release fromd presynaptic nerve and activates CL channels in postsynaptic membrane to be hyperpolarized.
         • Sucessive EPSP increase in amplitude known as frequency potentiation. Happens in presynaptic membrane
           • synapse between 2 neurons is inhibitory called ppresynaptic inhibition and doesnt alter excitability of post neuron

6. Muscles being stiff and losing plasticity=rigor mortis

   • Amount of force skeletal muscles exert depends on, no of active fibres, frequency of stimulation, rate of muscle shorten, initial resting length of muscle, cross sectional area
     • Single stimulus response=muscle twitch and the force developed= twitch tension
       • Abscence of stim, tension will increase slowly and muscle stretched beyond normal , called passive tension

7. Slow depolarisation before AP is pacemaker potential.

   • nerve and hormones can alter heart rate
     • Smooth muscles, have functional counterpart in dense bodiesand found through out cytoplasm and act as attachment for actin and iterim filaments. Both anchored into the plasma membrane at dense patches.
       • Smooth muscle fibre generates an AP, depends on influx of sodium and ca ions
       • Thin filament of smooth muscle do not have troponin
       • smooth muscles maintains steady level of contraction= TONE
       • Stress relaxation/Plasticity is when smooth muscles increased tension following stretch but progressive relaxation of tension towards initial value

8. Dura matter envelopes brain and spine and inner side has arachnoid membrane and that is linked to Pia matter and the space between the 2 is filled with Cerebrospinal fluid

   • Denticulates restrict movement of spinal cord in dura matter
   • Sensory info enters spinal cord via the dorsal root ganglion.
   • Nerves supplying body wall and skeletal muscles are somatic nerves

9. Motor systems control neural path controlling sequence and oatter of muscle contractions

   • Motor units in skeletal muscle fibres to contract
     • Goal directed movements need cerebral cortex but posture needs highher centres in brain
       • Proprioreceptors used to pass info about position of limbs and movements
         • Main ones are golgi tendon organ and muscle spindles
           • Golgi tendon found in tendon of muscles, respond to tension produced by bundle of fibres
     • Motor neurons occur in discrete motor nuclei
   • Some axons branch back into spinal cord and make excitatory contact w small interneurons called Renshaw Cells
     • have short synapse and are inhibitory
       • Muscle that flex limbs uncder control of neurons of dorsal, Muscles extend limbs lie in ventral
         • Muscle spindles stim in 2 ways, Stretching all skeletal muscle and intrafusal contracts while extrafusal same length.

10. Latency of reflex=time between stim and response

    • Monosynaptic reflexes, 2 neurons 1 synapse
      • 1 or more neuron between afferent and efferent neuron=interneuron
        • 1 interneuron and reflex has 2 synaptic relays= disynaptic reflex
    • Tonic stretch reflex helps stabilise length of muscles when under constant load
      • Flexion reflex, where remove limb from threat, Flexion reflex longer latency than stretch reflex as its disynaptic arc.

11. Recticular system important in startle reaction

    • Vestibuospinal tract, important for extensor muscles and posture
      • damage affects maintenance of posture
        • Postural muscles have lots of slow twitch (type1) fibres
      • Red nucleus, damage results in impairment of voluntary limb movements

12. Fibres from CNS to autonomic ganglia are preganglionic and from ganglia to target are postganglionic fibres

    • Pregang are myelinated and post gang unmyelinated
      • Males blood vessels innervated by sympathetic nerve and para symp only for iris control

13. Blood glucose levels usually 70-120mg/dl-1

    • Thyroid hormone increases rate of glucose uptake by cell.
      • Low conc of TH= reduced plasma glucose (anabolic). High conc=catabolic