Chapter 05: The Central Nervous System

Question 1

• What is the CNS?
• What do the nerves of the PNS do?
• What are the 3 structures that protect the CNS?
• What are meninges and its functions?
• Describe the dura mater (outer meningeal layer)
• Describe the arachnoid layer (middle meningeal layer)
• Describe the pia mater (inner meningeal layer)
• Where is 3 locations of cerebrospinal fluid?
• What are the 3 functions of CSF in the CNS?
• What forms CSF?
• Describe the circulation of CSF.

Answer 1

• Part of the N.S consisting of the brain and spinal cord.
• Carry the messages in and out of the CNS.
• Bone, meninges and cerebrospinal fluid (CSF).
• Protective membranes covering the CNS between bones of skull and soft tissue of brain and bones of spinal column and spinal cord.
• Toughest layer and fits closely to the bones of the skull, but as close fitting inside the vertebral canal.
• Consist of a web of collagen fibres.
• Softest layer, contains blood vessels to nourish the CNS tissue and helps to maintain the shape of the CNS.
• Between the middle and inner meninges layers, brain ventricles and the central canal.
• Shock absorber, support and transportation of nutrients/waste.
• Produced by capillaries in the ventricles in the brain
• Circulates through the CNS, eventually re-entering the blood capillaries. During its circulation it takes nutrients to the cells of the CNS and carries away their wastes.

Question 2

• Describe the cerebrum.
• What is the longitudinal fissure?
• What is the corpus callosum?
• Each cerebral hemisphere can be subdivided into what lobes?
• What makes white matter white?
• What are bundles of nerve fibres called in and out of the CNS?
• What are the 3 types of tracts occurring in the brain?

Answer 2

• Biggest part of the brain. Consists 3 layers, an outer surface of grey matter (cerebral cortex), middle layer of white matter and inside layer of grey matter (basal ganglia). It contains convolutions to increase surface area (70% of CNS neurones). The convolutions are separated either by shallow downfolds called sulci or deep downfolds called fissures.
• A deep cleft that almost separates the cerebrum into half.
• A bundle of nerve fibres at base of longitudinal fissure linking the 2 hemispheres and is where communication of the hems occur.
• Frontal, temporal, occipital, parietal.
• Composed of myelinated nerve fibres which is white fatty material.
• Within the CNS they are tracts whereas outside they’re nerves
  1. Tracts connecting areas of the cortex of the same hemisphere.
  2. Tracts carrying impulses between the left and right hemispheres.
  3. Tracts connecting cortex to other parts of the brain or spinal cord.

Question 3

• What activities takes place in the cerebral cortex?
• Why is it difficult to label specific parts of the brain cortex?
• What are the 3 types of functional areas in the cortex?
• How is memory stored?
• What is the main function of the cerebellum.
• What will happen if the cerebellum is removed?
• Describe the hypothalamus.
• What 7 things does the hypothalamus regulate?

Answer 3

• It receives all sensory info and enables mental activities (thinking, learning, intelligence), awareness of input from sense organs and voluntary muscle contractions.
• No area of the brain functions alone and boundaries are indistinct.
  1. Sensory areas: receive and process nerve impulses.
  2. Motor areas: Sends impulses to muscles.
  3. Association areas: Concerns intellectual and emotional processes.
• New links between neurones are made or modified in cerebral cortex.
• Receives impulses from the inner ear and stretch receptors in muscles to control posture, balance and coordinate movement.
• Movement will be jerky as there won’t be any coordination.
• It controls body activities to maintain homeostasis.
• ANS, body temp, food and water intake, sleeping patterns, urinary bladder contractions, emotional responses and coordination of endocrine system

Question 4

• What is the medulla oblongata?
• What 3 centres are within the medulla oblongata ?
• If a cross-section of the spinal cord is examined, it is seen to consist of what 2 areas and what do these areas consist of?
• How is the grey and white matter in the spinal cord different to the brain?
• What are ascending tracts?
• What are descending tracts?
• What is the brain?
• What is a reflex?

Answer 4

-Part of the brain that controls breathing and heart rate via respiratory and cardiac centres. (Below pons varolii)
1. Cardiac centre: regulates rate and force of heartbeat
2. Respiratory centre: controls rate and depth of breathing
3. Vasomotor centre: regulates diameter of blood vessels.
-Grey matter: nerve cell bodies and unmyelinated nerve fibres.
White matter: myelinated fibres.
-In the brain, the grey matter is at the surface and in the spinal cord the grey matter is in the centre surrounded by white matter.
-Sensory axons that carry impulses upwards, towards the brain.
-Motor axons that conduct impulses downwards, away from the brain.
-A mass of nerve tissue that forms the major section of the CNS and is found in the cranial cavity.
-An unconscious, fast response to a change in the internal or external environment.

Question 5

-What are the 4 differences between a reflex and a voluntary action?

Answer 5

1. Reflex is unconscious and voluntary is conscious.
2. Reflex is rapid and voluntary is slower.
3. Reflex is predictable and voluntary has varied responses.
4. Reflex does not involve brain and voluntary does.