Neurons, Hormones, and the Brain

1. Neurons, Hormones, and the Brain Chapter 4

2. Neurons, Hormones, and the Brain • The central nervous system • The peripheral nervous system • Communication in the nervous system • Neurotransmitters • Mapping the brain • A walk through the brain • The two hemispheres of the brain • Where is the self? • Are there “his” and “hers” brains?

3. The Central Nervous System • Brain • Spinal cord • A collection of neurons and supportive tissue running from the base of the brain down the center of the back. • Protected by spinal column.

4. The Withdrawal Reflex

5. Peripheral Nervous System • Somatic • Includes the nerves that are connected to sensory receptors and skeletal muscles. • Autonomic • The sympathetic nervous system mobilizes bodily resources and increases the output of energy during emotion and stress. • The parasympathetic nervous system operates during relaxed states and that conserves energy.

6. Organization of the Nervous System

7. Communication in the Nervous System • The structure of the neuron • Different kinds of neurons • How neurons communicate • Action potential • Chemical messengers in the nervous system • Neurotransmitters • Major neurotransmitters • Endorphins • Endocrine system • Hormones

8. Structure of a Neuron • Dendrites • receive information from other neurons and transmit towards the cell body. • Cell body • keeps the neuron alive and determines whether it will fire. • Axon • extending fibre that conducts impulses away from the cell body and transmits to other cells.

9. Structure of a Neuron • Myelin Sheath • Fatty insulation that may surround the axon of a neuron.

10. Different Kinds of Neurons

11. Neurons in the News • Canadian research has provided evidence for neurogenesis: the production of new neurons from immature stem cells. • Stem cells are immature cells that renew themselves and have the potential to develop into mature cells; given encouraging environments, stem cells from early embryos can develop into any cell type.

12. How Neurons Communicate • Axon terminals release neurotransmitter. • Neurotransmitter enters synaptic gap. • Neurotransmitter binds to receptors that it fits.

13. Action Potential • A brief change in electrical voltage which occurs between the inside and outside of an axon when a neuron is stimulated. It produces an electrical impulse.

14. Neurotransmitter • A chemical substance that is released by a transmitting neuron at the synapse and that alters the activity of a receiving neuron.

15. Major Neurotransmitters • Serotonin • Dopamine • Acetylcholine (ACh) • Norepinephrine • Gamma amino butryic acid (GABA) • Glutamate • Endorphins

16. Opioids and Substance P

17. The Endocrine System • Endocrine glands release hormones into the bloodstream. • Hormones regulate growth, metabolism, sexual development and behaviour, and other functions.

18. Hormones: Long Distance Messengers • Melatonin • Adrenal Hormones • Cortisol, epinephrine, and norepinephrine. • Sex Hormones • Androgens, estrogens, and progesterone.

19. Mapping the Brain • Lesion method • Electroencephalogram (EEG) • Transcranial magnetic stimulation (TMS) • Positron-Emission tomography (PET) • Magnetic resonance imaging (MRI)

20. Mapping the Brain • Lesioning • Involves damaging and removing sections of brain in animals, then observing their effects. • Transcranial magnetic stimulated (TMS) • Stimulates brain cells using a powerful magnetic field produced by a wire coil placed on the head. • Can be used to temporarily inactivate neural circuits.

21. Electroencephalogram (EEG) • A recording of neural activity detected by electrodes.

22. Positron Emission Tomography (PET) • A method for analyzing biochemical activity in the brain, using injections of a glucose-like substance containing a radioactive element. • Active areas have increased blood flow. • Sensors detect radioactivity. • Different tasks show distinct activity patterns.

23. Magnetic Resonance Imaging (MRI) • Method for studying body and brain tissue. • Magnetic fields align certain ions and compounds. • When field is removed, these molecules release energy as radio waves. • Computer calculates tissue density from radio waves. • Provides clear, 3D images.

24. A Walk Through the Brain • The brain stem • The cerebellum • The thalamus • The hypothalamus and the pituitary gland • The amygdala • The hippocampus • The cerebrum and lobes of the cerebral cortex

25. The Brain Stem • Pons • involved in sleeping, waking and dreaming. • Medulla • responsible for certain automatic functions such as breathing and heart rate. • Reticular activating system (or formation) • arouses cortex and screens incoming information.

26. The Cerebellum • Regulates movement and balance. • Involved in remembering simple skills and acquired reflexes. • Plays a part in analyzing sensory information, solving problems and understanding words.

27. The Thalamus • Relays sensory messages to the cerebral cortex. • Includes all sensory messages except those from olfactory bulb.

28. Pituitary Gland Hypothalamus and Pituitary Gland • Involved in emotions and drives vital to survival including fear, hunger, thirst, and reproduction. • Also regulates autonomic nervous system. • The pituitary gland is a small endocrine gland which releases hormones and regulates other endocrine glands.

29. The Amygdala • Responsible for arousal and regulation of emotion and the initial emotional response to sensory information. • Plays important role in mediating anxiety and depression.

30. The Hippocampus • Responsible for the storage of new information in memory. • Compares information with what the brain has come to expect about the world. • “Gateway to memory” because it enables us to navigate through the environment.

31. The Cerebrum • Largest brain structure. • Consists of upper part of brain and divided into two cerebral hemispheres which are connected by the corpus callosum. • In charge of most sensory, motor and cognitive processes. • Surrounded by cerebral cortex, a collection of several thin layers of cells (gray matter).

32. Lobes of the Cerebral Cortex • Occipital lobes • Visual cortex. • Parietal lobes • Somatosensory cortex. • Temporal lobes • Memory, perception, emotion and auditory cortex. • Left lobe, Wernicke’s area. • Frontal lobes • Emotion, planning, creative thinking and motor cortex. • Left lobe, Broca’s area.

33. Lobes of the Cerebral Cortex

34. Phineas Gage • Gage was a railroad construction foreman • An 1848 explosion forced a steel tamping rod through his head • Others said he was “…no longer Gage…” • Lost his job, worked as a sideshow exhibit

35. The Corpus Callosum • Millions of myelinated axons connecting the brain’s hemispheres. • Provides a pathway for communication between the hemispheres. • If surgically severed for treatment of epilepsy, hemispheres cannot communicate directly.

36. Split-Brain Experiment

37. Split-Brain Experiment • Subjects were presented information to one or the other side of their brains. • Patients identified verbally the pictures to the right (i.e., boy). • When asked to point to the face seen, the patients pointed to the left picture.

38. Where Is the Self? • Most scientists assume that what we call “mind,” “consciousness,” self-awareness,” or “subjective experience” can be explained in physical terms as a product of the brain. • Some contend that the brain consists of independent modules and that the self is an illusion. • No one understands yet how subjective experience is linked to physical processes in the brain.

39. Are There “His” and “Hers” Brains? • After analyzing 49 studies of sex differences in brain anatomy, Canadian researchers found small differences between the two groups and larger differences within groups. • There does appear to be sex differences in lateralization of language. Males show left hemisphere activation only. Females, left and right. • There also appears to be differences in amounts of grey matter. Females have more.

40. 3 Ways to Interpret These Findings • These supposed differences are stereotypes. • A biological difference does not necessarily have implications for behaviour or performance. • Sex differences in the brain could be the result rather than the cause of behavioural differences.