exam 3 - anaatomy

• nervous system has 3 over lapping function

  • sensory receptors
  • processes and interprets sensory input
  • dictates a response by activating effector organs
• sensory receptors

  monitor inside and outside body

  go from the PNS to the CNA

  ex. touch, warm vs cold, body temp, calcium
• Peripheral nervous system

  Nerves from the brain and spinal cord. Nerves by definition are an organ of the PNS.

  • periperal nerves link all regiones of the body to the CNS
• somatic body region

  body as a whole
• visceral body region

  internal organs
• Subdivisions of sensory input and motor output

  1. somatic sensory
  2. visceral sensory
  3. somatic motor
  4. visceral motor
• types of sensory and motor information 


  review

  
• sensory (afferent division)

  go from pns to cna

  • again, things we can touch
• visceral sensory

  internal organs. PNS to CNS.

  • stretching of organs . chemical changes, temprature changes
• motor (efferent)

  going away from the cns.. going to the pns

  • somatic motor ( skeletal muscles)
  • Visceral motor (involuntary so smooth muscle)
• cell body or soma

  control center for neuron
• dendrites

  recieving end

  • recieves signal from another neuron
• axon

  sends impulse and carries info to another cell body
• synapses

  are the sites at which neurons communicate, signals pass across the synapse in one direction.

  • the signal traveling down the axon is the electrical signal.
• presynaptic and post synaptic neuron

  • pre- sends the signal going towards synaps
  • post- receieves the signal. transmits electrical activity away from a synapse
• Plasma membranes of neurons conduct electrical signals

  resting neuron has a polarized membrane ( meaning seperation of charges)

  • inner side is negatively charges,
  • so stimulating the neuron causes it to depolorizze and making the inside less negative, or more positive
• stimulation of neuron cuases depolarization

  to keep axon at rest, keep neuron polarized.

  Seperation of charge = voltage can be measured

  • we burn energy trying to over come diffusion ( which would depolarize the synapse) to sit still. to stay polorized we require energy
• resting membrane has a negative inside its polorized

  depoloization - positive ions come in and make cell more positive, this triggers everything else to poloarize. all or nothing
• Strong stimulus applied to the axon triggers nerve impulses or action potential

  • impulse travels the length of the axon and if there's not enough + ions to move inside, no signal is sent
  • membrane can repolarize itself - signals becme neg again, or else another signal cannot be sent
• excitatory synapses

  • leads to an inflow of positive ions causes the action potential to occur. becomes depolorized.
• inhibitory synapses

  inside becomes more negative and an AP is less likely
• there is also a threshlold.

  needs that amount to overcome and create an AP
• Multipolar nueorns

  one axon, multiple dendrites.

  what you think of when you think of a neuron
• bipolar neuron

  rare- found in special sensory organs

  
• Unipolar neurons

  posses one short single process

  comes in on the posterior side of spinal cord?
• sensory neurons

  PNS->CNS

  ALL ARE UNIPOLAR NEURONS

  CELL BODIES IN GANGLIA IN PNS ( ganglia are bundles of cell bodies of sensory neurons)
• Motor neurons - MULTIPOLAR

  motor neurons are multipolar and have cell bodies within the CNS. not called ganglia, they are called the nucleus.

  go from CNS to PNS

  • form junctions with effector cells
• INterneurons

  between sensory and motor nuerons and most are unipolar

  confined to the CNA.
• • cell bodies of motor neurons are in the CNS -> Anterior Spinal cord. Anterior grey matter
  • Cell bodies of interneurons tend to be in POSTERIOR grey matter
  • sensory neuron cells bodies located in the ganglia
• 4 supporting cells in the CNS

  • provide supporitve functions. NON exciteable do not send AP. provide insulation. COver nonsynaptic regions
• Supporting cells in cns

  • astrocytes
  • microglia
  • ependymal cells
  • oligodendrocytes
• ependymal cells - supporting cell of cns

  line cavities of the brain, have projections that go into fluid filled cavity and move the fluid
• oligodendrocytes

  cells

  • provide insulation around axons in the CNS. wrap around axon multiple times. form a myelin sheath.
• Supporting cells in the PNS

  • satelite cells
  • shawann cells
• satallite cells

  surround neuron cell bodies within ganglia
• schwann cells

  • surround axons in the PNS
  • Form myelin sheath around axons of the PNS
• myelin prevent leakage of electrical current

  touch neurons could stimulate a pain neuron if leaked
• node of ranvier

  gaps between myelin sheaths on axons. Help the AP send faster becuase they jump node to node.
• Multiple sclerosis

  an autoimmune disease

  • immune system attacks the myelin around axons in the CNS.
  • difficulty controlling movement, sensory defecits
  • as we get older out myelin sheaths degrade
• Nerves - cordlike organs in the PNS

  consists of numerous acons wrapped in connective tissue

  axon is surrounded by schwann cells

  nerves also have blood vessels