Chapter 15: The Brain! Lesson Objectives: To describe the gross structure of the brain and the functions of the cerebrum, cerebellum, medulla oblongata and hypothalamus

Brain teasers – what do you see?

Stare at the dot for a few seconds, then move your head closer to it! http://www.pennmedicine.org/encyclopedia/em_DisplayAnimation.aspx?gcid=000016&ptid=17

What does the brain ideally look like? Of course, really the brain is dynamic and individually variable… http://www.pbs.org/wnet/brain/3d/index.html - information on Brain Anatomy!

The brain is an expanded extension of the spinal cord Brain structure Cerebrum (left and right cerebral hemispheres) linked by corpus callosum The brain is an expanded extension of the spinal cord It contains ventricles containing CEREBRO-SPINAL FLUID (continuous with the spinal cord) Consists of myelinated (white areas) and unmyelinated (grey areas) neurones

Brain structure – annotate! Ventricle containing cerebro-spinal fluid (secreted by the meninges)

Right versus left Cerebrum Verbal Non-verbal

The cerebrum – highly folded area Parietal lobe Sensory area Motor area Frontal lobe Contains an area involved with planning actions and movements Occipital lobe Corpus callosum – links the two cerebral hemispheres A large association area in the parietal and occipital lobes is involved in determining body position NOT SHOWN – Temporal lobe!

The cerebrum – highly folded area NOT SHOWN – Amygdala (‘almonds’) - coordinates the action of the autonomic and endocrine systems as well as a role in emotions Hippocampus (‘seahorse’) – role in memory (making new memories) Limbic system (part of) – emotions and memory

Studying the brain … BRAIN SCANS CAT scan (computer assisted tomography) Uses X-rays to find out about the tissues in the brain Put many ‘slices’ of the brain together to create a 3D image!

Studying the brain … BRAIN SCANS CAT scan (computer assisted tomography)

Studying the brain … BRAIN SCANS PET Scan (positive emission tomography) •Inject radioactive material (labelled 2-deoxyglucose) Respiring cells take this up and use it in glycolysis (phosphorylate it) It cannot be metabolised further or removed from the cell •Scan to detect the decay of the material (half-life) More metabolically active regions of the brain take up more 2-deoxyglucose. Give patient injection and then give them a stimulation or get them to think about something

Studying the brain … BRAIN SCANS PET Scans

Studying the brain … BRAIN SCANS MRI (magnetic resonance imaging) Used to find out which parts of the brain are active at different times Computer-controlled equipment measures the magnetic field from Haemoglobin in different regions of the brain Oxyhaemoglobin has a smaller magnetic effect than deoxyhaemoglobin Areas with high activity have a greater level of oxyhaemoglobin

Two association areas in the left hemisphere - language Broca’s aphasia http://www.youtube.com/watch?v=gocIUW3E-go Wernicke’s aphasia http://www.youtube.com/watch?v=aVhYN7NTIKU

The Cerebellum Cerebellum – folded surface Controls movement and posture – responsible for balance, coordination, eye movement and fine manipulation Receives impulses from ears, eyes, stretch receptors in muscles and other parts of the brain Integrates information and uses it to coordinate skeletal muscle contraction

The Brain Stem Mesencephalon (midbrain) Medulla oblongata Links the brain and spinal cord Coordinates and controls involuntary movements (breathing, heartbeat etc.) Pons – conducts signals from the cerebrum to the cerebellum and medulla as well as sensory signals to the thalamus

Diencephalon - the interbrain Hypothalamus Links the nervous system to the endocrine system via the pituitary Size of an almond in humans! Controls body temperature, hunger, thirst, fatigue, anger and circadian cycles (autonomic nervous system) Thalamus (left and right) Believed to process and relay sensory info. selectively to cerebral cortex The links with the cortex may be linked with consciousness Regulates sleep and wakefulness (damage leads to a coma!)

Phineas Gage (1823-1860) was a railroad construction foreman Studying the brain … Frontal lobe damage: Phineas Gage (1823-1860) was a railroad construction foreman An 1848 explosion forced a steel tamping rod through his head Others said he was “…no longer Gage…” 3.2 cm diameter rod! Went through his head from bottom to top and landed approx. 30 metres behind him!