chapter 5 - central nervous system

Question 1

what is the CNS

Answer 1

• consist of the brain and spinal chord

- where incoming messages are processed and outgoing messages are initiated

Question 2

how is the CNS protected

Answer 2

• bone: outermost protective layer (cranium / skull protects brain), spinal chord runs through the middle of the vertebral canal
• meninges: cover entire CNS, connective tissue (membranes), outer layer (tough and fibrous, sticks close to skull, not as close to vertebral column), middle layer (loose mesh work of fibres) and inner layer (more delicate, contains BV, sticks close to brain / spinal chord)
• CSF: occupies space in middle layer of meninges, brain cavities and centre of spinal chord, clear watery fluid (some cells, glucose, protein, urea, salts), supports (floats in fluid), protects (shock absorber) and transport (of nutrients and wastes), formed from blood (circulates CNS, re-enters blood, comes from tissue fluid forced out of capillaries)

Question 3

list the parts and lobes of the brain

Answer 3

• parts: cerebrum (folded into convolutions), medulla oblongata (joins brain and spinal chord), cerebellum (underneath rear, folds are less prominent), hypothalamus (deep inside brain)
• lobes: frontal, parietal, occipital, temporal, insula (deep inside brain)

Question 4

what is the cerebrum

Answer 4

• S: biggest part of brain, cerebral cortex (outer surface, grey matter, 2-4mm thick), white matter (myelinated nerve fibres), basal ganglia (deep inside, grey matter, cell body of myelinated fibres)
• F: memory (association areas), memories are not stored in cells, rather pathways of nerve cell am new memory = new links between neurons / existing links are modified

Question 5

what is the structure of cerebral cortex (cerebrum)

Answer 5

• contains 70% of all neurons in CNS, folding produces ridges (convolutions / gyri = increased SA), separated by sulci (shallow) and fissures (deep)
• longitudinal fissure: separates brain into left / right hemisphere, further separated into lobes
• tracts: bundles of nerve fibres in CNS, connects areas of cortex within same hemisphere carries impulses between hemispheres and connects cerebral cortex to other parts of CNS

Question 6

what is the function of the cerebral cortex (cerebrum)

Answer 6

• involved in mental activities (thinking, reasoning, learning, memory, intelligence, sense of responsibility), perception of senses / initiation of control of voluntary muscle contraction
• sensory areas: receive and process nerve impulses from the senses
• motor areas: send impulses to muscles (voluntary movement)
• association areas: interpret information from senses and make it useful (intellectual / emotional processes)

Question 7

what is the basal ganglia (cerebrum)

Answer 7

• S: masses of grey matter, groups of nerve cell bodies (associated with control of skeletal muscles)

Question 8

different functions of the two hemispheres

Answer 8

• L: language ability

- R: musical / artistic ability

Question 9

what is the corpus callosum

Answer 9

• S: wide band of nerve fibres, lies underneath cerebrum, base of longitudinal fissure
• F: nerve fibres cross over hemispheres, allowing communication

Question 10

what is the cerebellum

Answer 10

• S: 2nd largest part of brain, folded outer surface grey matter outside / white matter inside (branches to all grey parts)
• F: coordination of fine contractions of muscles (smooth movements), maintenance of posture and balance (receives from inner ear, unconsciously)

Question 11

what is the hypothalamus

Answer 11

• F: controls many body activities and maintains homeostasis
• > regulation of: ANS (heart rate, BP, digestive juice secretion, movement along alimentary canal, pupil diameter), body temp, food / water intake, patterns of waking / sleeping, urination, emotional responses
• > secretion of: hormones, coordinates with endocrine system and pituitary gland (regulates metabolism, growth, reproduction, response to stress)

Question 12

what is the medulla oblongata

Answer 12

• S: continuation of spinal chord, nerve fibres pass through to / from brain
• F: regulates ANS functions - cardiac cycle ( rate / force of HB), respiratory centre (depth / rate of breathing), vasomotor centre (diameter of BV)
• > other: reflexes of coughing sneezing, swallowing, vomiting, all controlled by higher centres (hypothalamus)

Question 13

what is the spinal chord

Answer 13

• S: 44cm, protected, most layer not connected to bone (fat / connective tissue / BV = padding / bending
• > white (myelinated fibres) and grey (inside, nerve cell bodies + unmyelinated fibres - interneurons)
• F: ascending tracts (sensory axons take impulses to brain) and descending tracts (motor axons take impulses from brain
• > pathway for communication (muscles / glands / brain), integration of automatic and protective reflexes