nervous control

• Nervous system

  • Sensory
  • Motor:

  Enteric

  Autonomic - Sympathetic, Parasympathetic

  Somatic
• what is the Central Nervous System made up of?

  • Brain
  • Spinal cord
• what are the types of Motor neurons?

  • Upper motor neurons
  • Lower motor neurons
• describe Upper motor neurons

  • Located in the motor cortex of the brain or the brainstem
  • initiate voluntary movement throughout the body
  • connect the cerebral cortex to the brain stem and spinal cord
  • travel down nerve tracts and synapse with lower motor neurons in the spinal cord
• Describe lower motor neurons

  • Located in the spinal cord
  • synapse with skeletal muscles, organs, and glands
  • extending to their appropriate destinations
• Autonomic - sympathetic and parasympathetic

  • Have pre- and post- ganglionic neurons
  • Sympathetic: Fright, fight and flight
  • Parasympathetic: Rest and digest
• Sympathetic and Parasympathetic Anatomical Differences

  Sympathetic:

  • Short preganglionic neuron
  • long post ganglionic neuron to target organ

  Parasympathetic:

  • Long ganglionic neuron
  • Short post ganglionic
• what do Somatic motors not have

  A ganglion
• Chemical synapse

  1. Vesicles undergo docking on the membrane prior to release

  2. Docked vesicles form a readily releasable vesicle pool

  3. Docking requires vSNARES, tSNARES and SNAP proteins
• vSNAREs

  On the vesicle, include Synaptobrevin 2 and Synaptotagmin
• tSNAREs

  Target proteins on the presynaptic membrane, include Syntaxin and SNAP25
• Synaptic release

  1. Membrane depolarises

  2. Voltage gated calcium channels open, Ca2+ ions flood in

  3. Bind to the C2A and C2B site on Synaptotagmin

  4. Binding to C2B causes it to move down and fuse with the membrane

  5. Vesicle fuses with presynaptic membrane and release their contents by exocytosis
• Electrical synapses

  • Found in the brain and spinal cord
  • direct ionic and small molecule communication
  • composed of gap junction channels
  • allow two-way transmission
  • no physical separation between cells so no synaptic cleft
• Neurotransmitters

  • Autonomic:

  1. Preganglionic sympathetic and parasympathetic neurons use acetylcholine
  2. Sympathetic postganglionic neurons use noradrenaline
  3. Parasympathetic postganglionic neurons use acetylcholine

  • somatic:

  1. Acetylcholine is used by lower motor neurons, is excitatory, causes muscles to contract
  2. Glutamate is used by the upper motor neurons, within the central nervous system, is excitatory, used in every major excitatory function in the brain, and accounts for over 90% of synaptic connections in the brain
• Enteric nervous system

  • Controls the gut
  • is an autonomous (independent) nervous system
  • has two nerve plexuses (networks) that regulate gastrointestinal (GI) activity: the myenteric plexus (Auerbach's) regulates motor activity (peristalsis), the submucosal plexus (Meissner's) regulates secretomotor activity
• Enteric nervous system controls

  Peristalsis, segmentation and other patterns of contraction of the smooth muscle of the gut
• The gut has its own pacemaker

  Interstitial cells of Cajal which gives a basal level of smooth muscle activity (tone)
• Gut is regulated by the autonomic nervous system


  Sympathetic and parasympathetic NS alter rate and force of contraction
• The heart

  • The conduction system is not nervous tissue but specialized cardiac myocytes whose primary function is impulse propagation rather than contraction and relaxation
  • Sympathetic and parasympathetic NS innervate and modify the heart
• Heart is myogenic

  The heart has its own pacemaker and can contract without nervous input
• Sensory Neurons

  • Activated by sensory input from the environment, carry impulse into the CNS, cell body is outside of the spinal cord in the Dorsal Root Ganglion and roots of sensory cranial nerves
• Receptors - eye

  • Rods and Cones
• Bipolar neurone in the eye

  Neurotransmitter released from rod is glutamate, this is inhibitory and stops bipolar neurone depolarising, bipolar neurone synapses to ganglion cell of optic nerve
• Seeing with both eyes

  Relay is in the brain, unusual
• Receptors - hearing

  • Organ of Corti made up of inner and outer hair cells embedded in the basilar membrane, has scala media, scala vestibuli, and scala tympani
• Organ of Corti

  The 'hearing' organ
• Frequency detection in the cochlea

  Changes along the cochlear, changes with age
• How the organ of Corti works

  Stereocilia are moved and bend towards the tall edge of bundle, stereocilia are joined by tip links, sound vibrations cause movement of endolymph, tension in tip links opens the 'trap door', K+ moves in and depolarises the cell, voltage-gated calcium (Ca2+) channels open, influx of Ca2+ triggers glutamate (neurotransmitter) release at the synapse via exocytosis, causes an action potential in the cochlear branch of the vestibulocochlear nerve, impulse sent to brain - we can hear
• Receptors - taste

  • Tongue has papillae, papillae contain taste buds, arranged in different areas across tongue but all respond to all just more sensitive to some, what is umami?
• Taste buds

  Found in the walls of papillae, each taste bud contains 50-150 taste receptor cells, have gustatory hairs protruding from the top, come into contact with taste molecules within the pore at the top in a fluid filled funnel, this causes ion channels to open and depolarisation of the cell and release of NT, causes associated sensory neurones to depolarise and the impulse travels back to the gustatory cortex, taste is determined by interaction between gustatory and olfactory input
• Olfaction

  • Olfaction is the sensation of smell that results from the detection of aerosols in the environment, this system is made up of the olfactory epithelium, olfactory nerves, olfactory bulb and tract, and olfactory cortex, odour detection occurs at the top of the nasal cavity, odour molecules reach the olfactory epithelium from the nose and via the mouth
• Detecting smell

  Odour molecules dissolve in a layer of mucus over the olfactory epithelium, olfactory epithelium contains millions of receptor cells, each cell has a single dendrite that extends to the outermost layer of the epithelium and has cilia extending over the epithelium, odorant molecules bind with the cilia and cause depolarisation, the generated action potential travels along the receptor cell axon to the olfactory bulb, in the olfactory bulb these axons synapse with olfactory bulb dendrites, clusters of mitral cells (neurons) and tufted relay neurons, these carry the wave of depolarisation along the olfactory tract to the olfactory cortex
• Motor – somatic  

  • a single neuron system with the cell body inside the brainstem or spinal cord
  • Spinal nerves are:
  • Cervical - 8 pairs: neck, shoulders, arms and hands
  • Thoracic - 12 pairs: Arms, chest, and upper abdomen
  • Lumbar - 5 pairs: Lower abdomen, hips and legs
  • Sacral - 5 pairs: Legs, foot and lower digestive tract
  • Coccygeal - 1 pair: Muscles of the pelvic region

  
• chemical synapse

  • For rapid release of NT, vesicles undergo docking on the membrane before release
  • Docked vesicles form a readily releasable vesicle pool 
  • Docking requires vSNARES, tSNARES  and SNAP proteins 

  
• chemical synapse drawing

  .