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Brain Structure & Function

Brain Structure & Function. Carl Sagan. Overview. Lobes of the brain (forebrain) Midbrain/ Hindbrain Protection and Blood Supply Structure and Functions of a Neuron Synaptic Transmission Neurotransmitters. Central Nervous System.

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Brain Structure & Function

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  1. Brain Structure & Function

  2. Carl Sagan

  3. Overview • Lobes of the brain (forebrain) • Midbrain/ Hindbrain • Protection and Blood Supply • Structure and Functions of a Neuron • Synaptic Transmission • Neurotransmitters

  4. Central Nervous System • The central nervous system consists of the brain and the spinal cord and is responsible for our basic functions, personality and behaviour.

  5. Forebrain • Cerebrum and Cerebral cortex • Left and Right Hemispheres • Left hemisphere for most people is the dominant hemisphere- responsible for production of language, mathematical ability, problem solving, logic • Right hemisphere thought to be responsible for creativity and spatial ability

  6. The Brain • Most complex organ in the body • Weighs 1,300 grams • Contains billions of neural networks that interact to create human behaviour

  7. The Lobes of the Brain • The major sections of the cerebral hemispheres are divided up into lobes. • The lobes are named after the bones of the skull that overlie them • Frontal Lobe • Temporal Lobe • Parietal Lobe • Occipital Lobe Barlow and Durand 2005

  8. Frontal Lobe • Located at the front of both cerebral hemispheres • Primary motor cortex • Pre-motor cortex • Broca’s Area- Motor Production of speech • Complex Functioning • Personality • judgement • Insight • Reasoning • problem solving, • abstract thinking • working memory

  9. Parietal Lobe • Located behind the temporal lobe • Sensory information • Temperature • Pain • Texture • Spatial orientation • Perception • Recognising object by touch • Links visual and sensory information together • Neglect

  10. Temporal Lobe • Auditory information • Higher order visual information • Complex memory • Memory of faces • Comprehension of language (Wernicke’s area)

  11. http://www.nidcd.nih.gov/health/voice/aphasia.asp)

  12. Occipital Lobes • Rearmost portion of the brain • Visual processing area • Corpus Callosum- Fibre bundle in the brain that connects the two hemispheres together.

  13. Other Important Structures • Hypothalamus • Thalamus • Cerebellum • Pons • Medulla Oblongata • Reticular formation • Basal Ganglia • Substantia Nigra • Amygdala • Hippocampus

  14. Diencephalon • Thalamus • filters sensory information, controls mood states and body movement associated with emotive states • Hypothalamus • Central control’ for pituitary gland. Regulates autonomic, emotional, endocrine and somatic function. Has a direct involvement in stress and mood states. (http://training.seer.cancer.gov/module_anatomy/unit5_3_nerve_org1_cns.html)

  15. Hindbrain • Cerebellum • regulates equilibrium, muscle tone, postural control, fine movement and coordination of voluntary muscle movement. • Pons • Relay station between cerebrum and cerebellum www.deryckthake.com/psychimages/hindbrain.

  16. Medulla oblongata • Conscious control of skeletal muscles, balance, co-ordination regulating sound impulses in the inner ear, regulation of automatic responses such as heart rate, swallowing, vomiting, coughing and sneezing • Reticular Formation- • Important in arousal and maintaining consciousness, alertness attention and Reticular Activating System which controls all cyclic functions i.e. respiration, circadian rhythm.

  17. Basal Ganglia Control of muscle tone, activity, posture, large muscle movements and inhibit unwanted muscle movements. • Substatia Nigra Produces dopamine, is connected to the basal ganglia – EPSE’s

  18. Limbic System • Amygdala • mediates and controls major affective mood states such as friendship , love, affection, fear, rage and aggression. • Hippocampus • Memory, particularly the ability to turn short term memory into long term memory. Alzheimer's disease.

  19. Pituitary and Pineal Glands

  20. Protection and Blood Supply • Meninges • Dura mater • Arachnoid Mater • Subarachnoid space • Pia mater • CSF • 2 main functions; shock absorption and mediation of blood's vessels and brain tissue in exchange of nutrients. • Circle of Willis • carotid arteries and baliser arteries • Blood Brain Barrier • Protect the brain from chemicals in the blood. Made up of tightly packed endothelial cells/capillaries making it difficult to penetrate. http://training.seer.cancer.gov/module_anatomy/unit5_3_nerve_org1_cns.html

  21. Neurons

  22. Structure of a Neuron

  23. RestingPotential

  24. Function of a Neuron • Resting potential • Positive/negative charge • Voltage • Gated channels • Sodium/ potassium pump • Action potential • Threshold • Depolarisation

  25. Action Potential

  26. Action Potential

  27. Synaptic Transmission • Calcium ion channels stimulate the release of neurotransmitters • Vesicles fuse to the cell membrane and release into the synapse • Lock and key effect • Reuptake of neurotransmitters into the cell or broken down by enzymes in the synaptic cleft

  28. Neurotransmitters

  29. There are two kinds of neurotransmitters – INHIBITORY and EXCITATORY. • stimulate the brain • calm the brain

  30. Neurotransmitters • Neurotransmitter is a chemical • Its released from the synaptic cleft • Another term for neurotransmitter is a ligand • Three main groups of neurotransmitters • Amines • Amino Acids • Peptides • Others

  31. Amines • Dopamine • Noradrenaline • Adrenaline • Serotonin • Amino Acids • Glutamate and GABA • Aspartate and glycine • Peptides • Cholecystrokinin • Neuropetide Y • Vasoactive intestinal Peptide • Substance P & Substance K • Somatosatin • Others • Acetylcholine • Histamine

  32. Neurotransmitters

  33. Neural Communication

  34. AMINES

  35. Dopamine (DA) • Almost a million nerve cells in the brain contain dopamine. • Role in • complex movement • cognition • motor control • emotional responses such as euphoria or pleasure. • Newer antipsychotic medication focus on particular dopaminergic pathways in the brain. Lessening EPSE’s.

  36. Dopamine Theory • The dopamine hypothesis of psychosis – overactivity of dopamine neurons in the mesolimbic pathway of the brain may mediate the positive symptoms of psychosis • Mesolimbic pathway responsible for pleasure, effects of drugs and alcohol and hallucinations and delusions

  37. Dopamine Receptors • Five subtypes – D2 most important in terms of psychosis • Blockade of mesolimbic receptors leads to reduced psychotic symptoms • Blockade of the mesocortical pathway leads to increased negative symptoms

  38. Dopamine Receptors • Dopamine and acetylcholine have a reciprocal relationship- • Blockade of dopamine receptors increases the activity of acetylcholine • Over activity of acetylcholine causes EPSE • Blockade of dopamine causes movement disorders in the nigostriatal pathway • Long term blockade causes “upregulation” and leads to Tardive Dyskinesia

  39. D2 ANTAGONIST Tuberoinfundibular pathway hyperprolactinemia (lactation, infertility, sexual dysfunction) Nigrostriatal pathway extrapyramidal side effects (EPS) and tardivedyskinesia Mesocortical pathway enhanced negative and cognitive psychotic symptoms Mesolimbic pathway dramatic therapeutic action on positive psychotic symptoms

  40. Dopamine Receptors www.lundbeck.com.au

  41. Serotonin (5ht) • Believed to be one of the great influences on behaviour. • Complex neurotransmitter. • Surprisingly only 2% of serotonin is found in CNS. • Roles include • Vasoconstriction, gastrointestinal regulation. • Low serotonin associated with aggression, suicide, impulsive eating, anxiety and low mood. • Regulates general activity of the CNS, particularly sleep. • Delusions, hallucinations and some of the negative symptoms of schizophrenia. www.rodensor.com/images/site_graphics/Dopamineseratonin

  42. Serotonin Receptors www.lundbeck.com.au

  43. Amino Acids

  44. Glutamate • Glutamate is found in all cells of the body • control the opening of ion channels that allow calcium to pass into nerve cells producing impulses • Blocking of glutamate receptors produces psychotic symptoms ( eg. By PCP) schizophrenic like symptoms • Over exposure of neurons to glutamate cause cell death seen in stroke and Huntington’s disease (PN).

  45. GABA Gamma-aminobutyricacid • Inhibitory and its pathways are only found within the CNS. • control excitatory neurotransmitters in the brain and controlling spinal and cerebral reflexes. • anxiety disorders • decreased GABA can lead to seizure activity • Benzodiazepines and barbiturates sedative medication act on GABA Benzo.org.au

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