THE BRAIN
Learning Objectives
Human brain: gross anatomy
Did you know…
• Weighs 1.5Kg
• 85% water
• Takes over 20 years to mature fully
• Approx 1/5 of your body mass
Spinal meninges
Cerebral meninges
• Protected by cranium and cranial meninges
• Bathed in cerebrospinal fluid
• 12 pairs of cranial nerves (sensory and motor nerves for head/neck)
• Contains approx 100 billion neurones (80% are cells in the cerebellum)
• All vertebrates have 3 regions: Hindbrain, Midbrain, Forebrain
Hindbrain
• Medulla oblongata – autonomic nervous system control
centre (part of brainstem together with pons)
• Cerebellum – coordinated movements & balance
• Reticular Activating System – controls ascending and
descending systems, e.g. activity of noradrenalinereleasing neurones, and sleep/wake cycle
EEG (“brain waves”) during sleep/wake states
• Surely you would
expect “more
activity” during
wakefulness to
show up as “higher
amplitude”
signals?
• No. In deep sleep,
many neurons are
synchronized (fire
together), so the
person is less
sensitive to
external stimuli.
Mid- and Forebrain
• Midbrain – connects fore- and
hindbrain
• Forebrain:
– Cerebrum – outer layer for
conscious thought (higher mental
activities)
• Thalamus – relays signals from
sensory organs to cerebral cortex
(except smell!)
• Hypothalamus – coordinating
centre between nervous &
endocrine systems
Functions of major brain structures
• Cerebrum:
• Frontal lobe – attention, decisions, higher brain functions, movement (planning and execution)
• Parietal lobe – sensation (touch), interpretation e.g. facial recognition, numerical/logical (left
side) or creative/artistic abilities (right side)
• Temporal lobe – hearing, memory, emotional responses
• Occipital lobe – vision, colour vision, detecting of movement.
• Corpus callosum: thick sheet of axons connecting left and right hemispheres of
cerebrum
• Cerebellum (“little brain”) – coordination, balance, motor memory (a complex
“calculator” to calibrate muscle movements (for skilled motor movements, e.g.
tennis/piano).
• Hypothalamus – controls endocrine system (hormones), appetite, thirst, sex drive,
temperature regulation, etc
• Pituitary gland: releases hormones into the blood, under control of hypothalamus
• Medulla oblongata – controls autonomic nervous system, e.g. blood pressure, heart rate,
breathing rate/depth. Receives sensory fibres from inner organs e.g. heart, and sends
motor axons back (reflexes).
• Spinal cord – receives sensory axons and sends out motor axons. Also has major twoway communication with the brain (via axons/white matter)
Lesson 2: organisation of the nervous system
D…………………………………………………………………………………….
Hemispheric specialization: different roles of
left and right hemisphere.
Organisation of the mammalian nervous system
Next : sheep brain dissection
http://brains.anatomy.msu.edu/brains/sheep/index.html