Transcript E4 Neurotransmitters and Synapses (and drugs!)

Brain
Cerebrum/
Cerebral
Hemispheres
Hypothalamus
Pituitary Gland
Cerebellum
Medulla
Oblongata
Medulla Oblongata
 Controls automatic and homeostatic activities vital to
life including
 Swallowing
 Digestion
 Vomiting
 Breathing
 Heart activity
Cerebellum
 Coordinates unconscious functions such as movement
and balance
Hypothalamus
 Maintains homeostasis by coordinating the nervous
and endocrine system
 Secretes hormones that are stored and released from
posterior pituitary
 Controls anterior pituitary by secreting releasing
factors (that control the release of anterior pituitary
hormones)
Pituitary Gland
 Posterior Pituitary Gland: Stores and releases
hormones produced by the hypothalamus
 Anterior Pituitary Gland: Produces and secretes
hormones that regulate many body functions
Cerebral Hemispheres
 The integrating center for high complex functions
 Associated with:
 Intelligence and learning
 Memory
 Emotions
 Personality
 Sensory impulses
 Motor function
 Organization
 Problem solving
Voluntary
movement;
contains
dopaminesensitive
neurons;
reward;
attention;
short-term
memory;
planning;
motivation
Auditory perception;
processing of speech
and vision; contains
hippocampus= long
term memory
Integrates sensory info;
important in spatial
awareness and navigation
Visual processing
center
Pons
 Involved with sleep, respiration, swallowing, bladder
control, hearing, taste, eye movement, facial
expressions, facial sensations, posture
Corpus Callosum
 Connect the right and left hemisphere
 (facilitates inter-hemispheric communication)
Thalamus
 Regulates consciousness, alertness and sleep
 Relays sensory and motor signals
Cerebral Cortex
 A sheet of neural tissue that covers the cerebrum and
the cerebellum
 Involved in:
 memory,
 Attention
 Perceptual awareness
 Thought
 Language
 consciousness
Animations
 http://www.pennmedicine.org/encyclopedia/em_Disp
layAnimation.aspx?gcid=000016&ptid=17
Brain Lesions
 Created when an individual suffers brain damage in a
particular area.
 Brain lesions can tell neurobiologists indirectly about
the function of those parts of the brain.
 Much about the functions of the left and right
hemisphere have been learned this way
Right and Left Hemispheres
 The brain is divided
into the left and
right hemispheres
 They are connected
by a thick band of
axons called the
corpus callosum
Left Hemisphere
 Contains areas important for all forms of
communication
 So, if a person has a stroke that result in damage to the
left hemisphere, they may have difficulty speaking or
doing complicated movements of the hands or arms.
Right Hemisphere
 Not involved in communication, however it does help
us understand words.
 Specializes in receiving and analyzing information
which comes in through all our senses
 When people have lesions in the right hemisphere,
they have problems identifying faces, and locating
objects, unable to identify melodies
 In the 1960, experiments were conducted on patients
who had surgeries to sever their corpus callosum (to
relieve symptoms of epilepsy) but keeping the optic
chiasma intact
 Scientists projected a picture of a spoon onto the right
side of a card with a dot in the middle.
 The spoon is in the right visual field but ends up on
the left hemisphere
 The person has no problem identifying the spoon
(language is in the left hemisphere)
 If the spoon is on the left side of the dot, therefore in
the left visual field, the information goes to the right
side of the brain where there is no language ability
 The person will not be able to identify the object as a
spoon
 If the patient is told to pick up the spoon with their left
hand, they can.
 The right hemisphere can understand it is a spoon
even though they cannot verbalize it
Chimerical Picture to test split
brains patients
 Figure that is a man’s face on the right, and a woman’s
on the left.
 Patients are to focus on a dot in the middle of the
forehead
 Image of woman goes to right hemisphere
 Image of man goes to left hemisphere
 If the patient then looks at complete pictures with
normal faces and is asked to point to the face they have
just seen, they will choose the picture of the woman
 (It went to the right hemisphere to be analytically
processed)
 However, if asked if the picture was of a man or a
woman, they will say it is a man (left hemisphere –
language!)
Video
 Severing the Corpus Callosum (10 min)
 https://www.youtube.com/watch?v=lfGwsAdS9Dc
fMRI: functional magnetic
resonance imaging
 When a particular part of the brain is active, it requires
more oxygen
 Oxyhemoglobin responds different to a magnetic field
than de-oxyhemoglobin
 Scientists can ask a patient to perform tasks or expose
them to stimuli and then observe which areas blood
flow increases in.
Animal Experiments?
 Ethical issues?
 “Con” side say that human brains are quite different
from animal brains and thus, needless animal cruelty.
 “Pro” side do not agree and claim that primate brain
research has provided important information.
Sympathetic and Parasympathetic
Control
 Autonomic nervous system: involuntary control
 Divided into the sympathetic and parasympathetic
 Sympathetic: involved in action
 Fight or flight
 Impulses will increase heart rate, dilate irises, redistrubute
blood flow to muscles…
 Parasympathetic: involved in process that occur at rest
 Reduce heart rate
 Constrict pupils
 Redistribute blood to gut to facilitate in digestion
Pupil Reflex
 Enough light must fall on the retina so that the
individual can see properly.
 Too much light can cause damage to the retina.
 The pupil will be dilated in dim light – allowing more
light into the eye, and constrict in bright light
Pupil Reflex
 The size of the pupil is controlled by the iris which
surrounds it.
 The iris is made of circular and radial muscles
 When bright light is precieved by the retina, an
impulse is sent to the midbrain, and then back to the
eye causing the circular muscle to contract and the
radial muscles to relax  constricting pupils
 When the circular muscle relaxes and the radial
muscles contract, the pupil becomes larger (dilated)
Brain Death
 The permanent absence of measurable brain activity
 It is possible to maintain processes such as cardiac
function and respiratory function for a long time
without the patient responding to signals
 fMRI may be used to determine brain activity
 When it is presumed that there is no longer any form
of consciousness, doctors are allowed to declare the
patient dead and turn off life support equipment
Brain Death
 Brain death is different from a coma or a vegetative
state – in which there is a measurable amount of brain
activity
Brain Death – ways to confrim
 Absence of a pupillary reflex is an indication that
cranial reflexes are absent and the patient is brain
dead.
 Absence of gag reflex
 Absence of respiratory response
 Absence of corneal reflex
 Injection of radioisotopes and us of an
electroencephalogram (EEG)
Endorphins
 Pain informs us that there is a problem somewhere
and alerts us so we can help fix the problem and
reduce damage.
 Pain receptors are nerve endings in the skin and other
organs.
 They response to chemicals released by blood vessels
when they become damaged.
Endorphins
 Pain receptors cause sensory neurons to initiate and action
potential that is sent through the spinal cord to the
cerebral cortex where pain is experienced.
 The experience of pain is closely related to emotional
factors and the severity of the trauma
 After the brain has been altered of the situation, pain can
be reduced so it doesn’t take up too much attention by the
individual.
 The brain produces ENDORPHINS
Endorphins
 Natural pain killers
 Ex: Encephalins
 Small proteins that inhibit the neurons sending the pain
signal to the brain.
 Does this by blocking calcium ion channels
 This prevents calcium from entering the pre-synaptic
knobs, and therefore the releasing neurotransmitters to
initiate an action potential in the next neuron.
 Morphine and heroine mimic endorphins
Videos
 How does your brain know where you are?
 https://www.ted.com/talks/neil_burgess_how_your_b
rain_tells_you_where_you_are
Animations
 Parkinsons
 http://www.pennmedicine.org/encyclopedia/em_Disp
layAnimation.aspx?gcid=000095&ptid=17
 Concussions
 http://www.pennmedicine.org/encyclopedia/em_Disp
layAnimation.aspx?gcid=000034&ptid=17
 Alzheimer’s Disease
 http://www.pennmedicine.org/encyclopedia/em_Disp
layAnimation.aspx?gcid=000003&ptid=17