the human brain hl only. e.5.1. label, on a diagram of the human brain, the medulla oblongata,...
TRANSCRIPT
The Human BrainHL Only
• E.5.1. Label, on a diagram of the human brain, the medulla oblongata, cerebellum, hypothalamus, pituitary gland and cerebral hemisphere.
Label the brain
• E.5.2 Outline the functions of each of the parts of the brain listed in E.5.1
• The brain is the most complex organ in the body.• Weighs about 1.4 kg• Contains over 100 billion neurones with thousands of synapses• New connections made daily• Regulates & monitors unconscious body processes• Receives & interprets information from our senses• Controls voluntary movement
• E.5.3 Explain how animal experiments, lesions and fMRI (functional magnetic resonance imaging) scanning can be used in the identification of the brain part involved in specific functions.
Brain Lessions
• Accidents to the brain, stroke and tumours can damage specific parts of the brain, the damaged area is a lesion. From the position of the lesion, we can determine functions of that part of the brain by observing what the patient can no longer do.
Broca’s area
• The most famous study is of a region known as Broca’s area, in the 1860’s. One patient, Leborgne, could only speak one word. Lelong could only speak a few words.
Broca’s area
• When they died, Broca examined their brains• Lesions were found in the same area• Deduced this region was responsible for language
– Broca’s area – interferes with localization– Wernicke’s area – affects the ability to put words into sentences
• fMRIs have confirmed this• Brain divided into left & right hemispheres• Connected by the corpus callosum• Not the same functions
Right & Left Hemisperes
Right Hemisphere
• Specializes in receiving & analyzing information from all of our senses
• Problem identifying faces• Problems locating an object
correctly in space• can’t identify melodies
Left Hemisphere
• Important for all forms of communication
• Difficulty speaking• Difficulty doing complicated
movements of the hands/arms
• Deaf people with damage here – can’t use sign language
fMRI
How do we know about the functions of the brain?• “Brain Mapping” – uses radio waves & a strong magnetic field
(not Xrays)• Can see the blood flow in the brain as it occurs• Increased blood flow to regions of the brain is detected and
overlayed on a brain map• Allows us to see which sections of the brain are most active
during particular tasks
fMRI
• Studies have been used to discover the functions of various regions of the brain
• To show differences and similarities between groups of people and are a useful diagnostic tool in medicine
Animal Experiments
• Are often controversial• Have led to many advances in science• Key to 19th century discoveries
Animal Studies
Studies involved dissection of human brains (post-mortem) –compared to animal
specimens Removal of sections of animal brains - to observe impaired
function (Flouren – exp. on pigeons. Removal of the cerebellum led to its discovery as the movement centre of the brain)
Electrical stimulation of living primate and dog brains in order to observe movement and actions in the body
Animal Studies
• One type of animal experiments is to expose animal models to addictive substances in controlled situations.– Want more and more of the substance– Spend lots of time and energy getting it– Keep taking it despite adverse conditions– Have withdrawal symptoms on withdrawal of the substance– Go back to the substance when stressed– Go back to the substance with another exposure to that substance
To test if a chemical meets the criteria for addiction
1. An animal is trained to press a lever to get a reward2. The animal is given an injection of the addictive substance. The
lever must automatically give the injection if it is pushed by the animal. (self-administration)
3. In order for this to be a controlled experiment, 2 levers must be available, one which gives the substances & one that doesn’t
4. If the substance is ‘reinforcing’, the animal will seek to repeat the experience by pushing that lever much more frequently
Animal Experiments
• E. 5.4 Explain sympathetic and parasympathetic control of the heart rate, movements of the iris and flow of the blood to the gut
Sympathetic & Parasympathetic control
Cardiac muscleSmooth muscle
Antagonistic
Target Sympathetic Parasympathetic
Heart rate Increase heart rate Decrease in heart rate
Blood vessels Decreases diameter of major arteries therefore increasing blood pressure
Increases diameter of major arteries therefore decreasing blood pressure
Flow of blood to intestines (gut)
Decreased flow to intestines Increased flow to intestines
Iris movement Iris muscles cause pupil to dilate
Iris muscles cause pupil to constrict
Heart Rate
Gut Blood Flow
Iris Control
• E.5.5 Explain the pupil response
Pupil Reflex
Pupil Reflex
Cranial reflexCranial reflex
Not spinal cord reflex
Not spinal cord reflex
• E.5.6 Discuss the concept of brain death and the use of the pupil reflex in testing for this.
Determining Brain Death
• We can artificially maintain the body using ventilation & circulation
• Brain stem controls heart rate, breathing rate and blood flow
What is the definition of brain death?
What is the definition of brain death?
That time when a physician has
determined that the brain and brain
stem have irreversibly lost all
neurological function.
That time when a physician has
determined that the brain and brain
stem have irreversibly lost all
neurological function.
Coma vs Brain Death?
Coma• Profound or deep state of
unconsciousness• Still have neurological signs
– No eye-opening– Unable to follow instructions– No speech or other forms of
communication– No purposeful movement
Brain Death• Must perform a toxicology
test• Examination
– Movement of extremities– Eye movement– Corneal reflex– Pupil reflex– Gag reflex– Respiration response
Spinal reflexes may still function – knee jerk
Spinal reflexes may still function – knee jerk
• E.5.7 Outline how pain is perceived an dhow endorphins can act as painkillers.
Perception of Pain
• Stimulus: Pressure, heat or penetration (nocioreceptors)– Housed in the skin, muscles, bones, joints & membranes around
organs• Impulse: relayed to brain via spine• Perception: in cerebral cortex leads to feelings of pain• Function: pain acts as a ‘stop’ signal to prevent more damage to
the body– Muscles stop the action causing the pain stimulus– Alerts the autonomic nervous system if the pain requires change in
heart rate or breathing– Can direct other brain cells to release pain-suppressing endorphins
Pain is in the Brain!
Endorphins
• First discovered by scientists studying opium addiction• Found receptors for opiates, morphine & heroin in brain cells• Morphine & heroin bound to the brain receptors because they
were mimicking endorphins• Endorphins are CNS neurotransmitters with pain-relieving
properties• They are small peptides which bind to opiate receptors & block
the transmission of impulses at synapses involved in pain perception
Endorphins