basic organisation of the nervous system

Question 1

what are the divisions of the PNS?

Answer 1

• Somatic PNS
  Controls motor and sensory function of the body wall
• Autonomic nervous system
  Has Sympathetic and Parasympathetic arms

Question 2

what is the direction of afferent axons?

what is the direction of efferent axons?

Answer 2

• afferent is towards the CNS

- Efferent Axons - away from the CNS

Question 3

what are interneurones?

Answer 3

CNS neurons that synapse with other CNS neurons within the brain and spinal cord

Question 4

how are axons packaged into nerves?

Answer 4

• spinal nerves contain both afferent and efferent axons
• they are bundled into fascicles surrounded by the perineurium
• the whole nerve is in a tough epineurium capsule
• induvidual axons are also wrapped in myelin and endoneurium (some are not myelinated)

Question 5

which types of neurones are able to regenerate?

Answer 5

• Axons in the PERIPHERAL NERVES CAN REGENERATE after injury

Question 6

why is the regeneration of CNS neurones not useful?

why is this?

Answer 6

• they cannot regenerate over long distances
• There are inhibitory molecules in the CNS but not in the PNS
• there is an absence of guidance cues
• loss of intrinsic axon growth capabilities by the neurons

Question 7

what does the grey matter and white matter consist of?

Answer 7

grey matter = neuronal cell bodies

white matter = ascending and descending axon tracts to and from the brain

Question 8

what does a fast reflex consist of?

Answer 8

• Only need somatic input to the spinal cord and motor outputs from the spinal cord are required
• the brain is not involved
• thew sensory and motor neurones must be intact

Question 9

what happens in conscious registering?

Answer 9

• this is when the sensory inputs activate further sensory neurones in the grey matter of the spinal cord which transmit action potentials to the sensorimotor cortex of the brain

Question 10

so what does the white matter of the spinal cord and brainstem contain?

Answer 10

• ascending sensory axon from spinal cord to sensorimotor cortex of the brain
• descending motor axon tracts from the sensorimotor cortex of the brain to the spinal cord

Question 11

what does the central nervous system consist of?

Answer 11

composed of the brain and spinal cord.