WEEK 4 - The Central Nervous System

Question 1

function of CNS/PNS

Answer 1

CNS:
- integrate or control the control centre
- interpret sensory input and dictates the motor output
-nuclei: clusters of neuron cell bodies/soma
- the bundle of axons aka tracts

PNS:
- communicates between the brain and the rest of the body
- cranial nerves: carry impulses to and from the brain
- spinal nerves: carry impulses to and from the spinal cord
- ganglia: clusters of neuron cell bodies/soma
- the bundle of axons aka nerves

Question 2

structure of the brain

Answer 2

two cerebral hemispheres (L/R) make up the cerebrum

grey matter: made up of neuron cell bodies
- cortical grey matter interprets sensory input, processes intellect and emotions, controls voluntary and skeletal muscle activity
- basal grey matter: subcortical motor enters, helps control skeletal muscle movement

white matter: made up of myelinated axons

Question 3

control of involuntary movement

Answer 3

in the middle of the brain, a structure called substantial nigra is a basal nuclei, it is pigmented and makes a type of melanin called neuromelanin

• the substantia nigra has an enzyme called tyrosine hydroxylase, it will take the amino acid tyrosine and change it to an enzyme called L-dopa and then through another enzyme called DOPA decarboxylase, will then be changed into dopamine
• this dopamine reaches other basal nuclei aka striatum and controls movement

Question 4

parkinsons disease

Answer 4

• no DOPA, no inhibition, leads to tremors, slow movement, rigidity, not enough dopamine to control movement
• dopamine cannot cross the blood-brain barrier
• L DOPA can cross, but its problematic bec needs to keep giving/inc concentration, and it becomes toxic that destroys liver

Question 5

cerebral cortex contrains 3 types of functional areas

Answer 5

1. motor area: controls voluntary movement
   - broca’s area: directs muscles involved in speech production, located in the frontal lobe, controls muscles needed to make sound

broca’s aphasia: damage of the Broca’s area prevents muscles involved in speech to work

2. sensory area: conscious awareness of sensation
3. association area: integrates diverse information
   - wernicke’s area: involved in the understanding of written and spoken language, can still speak, but affects understanding

Question 6

organisation of grey matter of spinal cord

Answer 6

• dorsal side: receives sensory info, afferent
  information is going from somatic (skin/muscle)/visceral (organs) sensory neurons
  goes through the dorsal root ganglion and then to the brain
• ventral side: receives motor info, efferent thus exits the brain into the ventral horn, NO ganglion, out to visceral/somatic motor neuron

Question 7

white matter

Answer 7

• mostly myelinated nerve fibres aka axons that form tracts (bundles of axons) CNS, allow communication between parts of spinal cord, and spinal cord and brain

ascending (arriving to brain)
spinothalamic tract: transmits pain, temperature, coarse touch and pressure, chain of 3 neurons

1st neuron: conducts impulses from cutaneous receptors and proprioceptors to spinal cord
2nd neuron: interneuron, axons extend to thalamus (relay station in brain)
3rd neuron: axon extends to the somatosensory cortex, transmit information to sensory area

descending
corticospinal tract: transmits motor impulses from cerebrum to spinal cord motor neurons (activates skeletal muscle)

Question 8

hypothalamus

Answer 8

• regulates

Question 9

brain stem

Answer 9

• includes the midbrain, pons, and medulla oblongata
• controls visual and auditory reflexes
• respiratory centers
• cardiovascular centres