1. A.2.: The Human Brain

2. Development of the Brain
Cephalization: process in which the anterior part of the neural tube expands to form the brain.
Human brain contains about 86 billion neurons

3. Brain Cerebrum/ Cerebral Hemispheres Hypothalamus Pituitary Gland
Cerebellum
Medulla Oblongata

4. Medulla Oblongata
The medulla is part of the autonomic nervous system (controlling involuntary processes)
Controls automatic and homeostatic activities vital to life including
Swallowing
Digestion
Vomiting
Breathing
Heart activity

5. Brain coordination: Swallowing
When you first pass food from your mouth to the pharynx, that is a voluntary action and is controlled by the cerebral cortex.
Movement from the pharynx to the stomach via the esophagus is involuntary and coordinated by the medulla.

6. Brain Coordination: Breathing
2 separate centers in the medulla control breathing
One controls the timing of inspiration
The other controls the force of inspiration and active voluntary expiration
Chemoreceptors in the medulla monitor blood pH which will influence the breathing rate and/or depth of breath

7. Brain Coordination: Heart Rate
Blood pH and pressure are monitored by receptor cells in blood vessels and the medulla.
The cardiovascular centre of the medulla regulates heart rate and can increase or decrease heart rate by sending signals to the sinoatrial node of the heart (the pacemaker)

8. Cerebellum
Coordinates unconscious functions such as movement and balance and posture

9. 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)

10. 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

11. Cerebral Hemispheres The integrating center for high complex functions
Associated with:
Intelligence and learning
Memory
Emotions
Personality
Sensory impulses
Motor function
Organization
Problem solving

12. Voluntary movement; contains dopamine-sensitive neurons; reward; attention; short-term memory; planning; motivation
Integrates sensory info; important in spatial awareness and navigation
Visual processing center
Auditory perception; processing of speech; contains hippocampus= long term memory

14. Pons
Involved with sleep, respiration, swallowing, bladder control, hearing, taste, eye movement, facial expressions, facial sensations, posture

15. Corpus Callosum Connect the right and left hemisphere
(facilitates inter-hemispheric communication)

16. Thalamus Regulates consciousness, alertness and sleep
Relays sensory and motor signals

17. Cerebral Cortex
A sheet of neural tissue that covers the cerebrum and the cerebellum.
~2 -4mm thick.
It forms a large proportion of the brain and is more highly developed in humans than other animals (has many more neurons than other animals)
Throughout human evolution, the cerebral cortex has become enlarged
Most of the surface area is in the folds

18. Cerebral Cortex Involved in: Only mammals have a cerebral cortex.
Memory
Attention
Perceptual awareness
Thought
Language
Consciousness
Only mammals have a cerebral cortex.

19. Animations

20. 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

22. 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

23. Cerebral Hemispheres
The cerebral hemispheres receive sensory input from all the sense organs in the body.
Sensory impulses from the right side of the body are processed by the LEFT HEMISPHERE.
Sensory impulses from the left side of the body are processed by the RIGHT HEMISPHERE.

24. Cerebral Hemispheres -Visual Cortex
Found in both hemispheres.
This is where neural signals from rods and cones are processed
Images from the right visual field are processed in the left hemisphere, and images in the left visual field are processed in the right hemisphere because of the optical chiasma

25. Cerebral Hemispheres- Auditory Centre
The exception to this crossover: the ears!
Left ear  auditory center (in temporal lobe) of left hemisphere
Right ear  auditory center(in temporal lobe) of right hemisphere

26. Cerebral Hemispheres
The primary motor cortex in the left hemisphere controls the muscles in the right side of the body
The primary motor cortex in the right hemisphere controls the muscles in the left side of the body
That’s why someone who has experience brain damaged in the left side of the brain may experience paralysis in the right side of the body (and vice versa)

27. Left Hemisphere
Contains areas important for all forms of communication
Ex: Broca’s area: this region controls the production of speech
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.

28. 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

29. 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

30. 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 Broca’s left hemisphere)

31. 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

33. 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

34. 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!)

35. Video Severing the Corpus Callosum (10 min)

36. Nucleus Accumbens Found in each cerebral hemisphere
It is the pleasure/reward centre of the brain.
A variety of stimuli (ex: food, sex, completing patterns, cute kittens!) will cause the release of the neurotransmitter dopamine which cause the feelings of well-being, pleasure, and satisfaction.
Some drugs such as cocaine, Heroin, and nicotine are addictive because they artificially cause the release of dopamine from the nucleus accumbens

37. Homunculi
The sensory homunculus and motor homunculus are models to the relative space human body parts occupy on the somatosensory cortex and the motor cortex

38. Homunculi

39. Energy and the Brain
86 billion neurons means lots of oxygen and glucose required by the brain for cellular respiration for the ATP energy for all the work it needs to do.
In an adult human 20% of the total cellular respiration occurs in the brain.
Higher in infants and small children!

40. 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.

41. 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

42. 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

43. 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

44. When the circular muscle relaxes and the radial muscles contract, the pupil becomes larger (dilated)

45. 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

46. Brain Death
Brain death is different from a coma or a vegetative state – in which there is a measurable amount of brain activity

47. 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)

48. 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.

49. 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

50. 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

51. Videos How does your brain know where you are?
Patterns

52. Animations Parkinsons
Concussions
Alzheimer’s Disease