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A.2 The human brain
Most of the neural tube becomes the spinal cord but the anterior end expands and
develops into the brain in the process called cephalisation (the development of a head).
Brain as the central control center: directly — from cranial nerves, indirectly — spinal
cord and signal molecules in blood. The advantage of having a brain is that
communication between the bilions of neurons can be more rapid than it would be if
control centers were more dispersed.
Nervous system:
Peripheral (PNS) — nerves and sensory receptors that belong to two parts: the
voluntary and autonomic nervous systems. *nerves and sensory receptors in the
autonomic nervous system use centers located in the medulla oblongata (which is
located in the brainstem so it is the CNS)
Central (CNS) — the brain (anterior part of the neural tube) and the spinal cord (the
rest of the neural tube that thickens)
Cell proliferation continues in the neural tube because much more neurons are needed
than there are present initially.
Parts of the brain
Function
Medulla oblongata (covered
with cranial nerves)
Autonomic control of the gut muscles, breathing, blood vessels
and heart muscle (sympathetic & parasympathetic nerve fibres);
*the pupil reflex and brain damage
Cerebellum
Coordinates unconscious functions such as posture, nonvoluntary movement, balance
Hypothalamus
Interface between the brain and the pituitary gland, controlling the
secretion of the pituitary hormones
Pituitary gland
Secretes at least ten hormones that regulate many body functions
Cerebral hemispheres
(include frontal lobe, parietal
Act as integrating center for higher order functions such as
learning, memory, emotions. Structure: somatosensory cortex;
motor cortex; visual cortex; Broca’s area; nucleus accumbens
A.2 The human brain
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lobe, occipital lobe, temporal
lobe)
Somatosensory
cortex
Receives sensory inputs
Motor cortex
Controls voluntary muscle contractions by striated muscles
Visual cortex
Processes visual stimuli detected by light-sensitive rod and cone cells in the
retina
Broca’s area
A part of the left cerebral hemisphere that controls the production of speech
Nucleus
accumbens
Pleasure or reward centers which receive dopamine released in responce to
a variety of stimuli
Methods of brain research:
Lesions and autopsy
Dissection of an animal or a human after death to relate positions of
lesions to observed changes in behaviour or capabilities
Animal experiments
Carried out by removing parts of the skull to allow access to the brain
and study the effects of local simulation on specific parts of the brain
Functional MRI
(Magnetic resonance
imaging)
Helps to investigate the internal structure of the body, including looking
for tumours or other abnormalities
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The left cerebral hemisphere controls muscle activity in the right side of the
body and vice versa for the right hemisphere.
Brain metabolism requires large energy inputs — 10-20% of the energy consumed by
basal metabolism.
A.2 The human brain
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