Review structure and function of brain, limbic system, ubnormal neurotransmission

REVIEW OF STRUCTURE AND FUNCTION OF BRAIN, LIMBIC SYSTEM, ABNORMAL NEUROTRANSMISSION

1. WELCOME JINTO PHILIP ASST. PROFESSOR MSc in Psychiatric Nursing

2. REVIEW OF STRUCTURE AND FUNCTION OF BRAIN, LIMBIC SYSTEM, ABNORMAL NEUROTRANSMISSION COMPONENTS OF THE NERVOUS SYSTEM Central Nervous System (CNS) Peripheral Nervous System (PNS) Psychobiology: Study of biological foundations of cognitive, emotional and behavioral processes.

3. CENTRAL NERVOUS SYSTEM Brain Nerve tissue Spinal cord Forebrain Hindbrain Neurons Synapses Neurotransmitters Fiber tracts Spinal nerves Midbrain

4. PERIPHERAL NERVOUS SYSTEM Afferent system Sensory neurons B. Efferent system Somatic Nervous System-somatic motor neurons Autonomic Nervous System Somatic Visceral Sympathetic nervous System (Visceral motor neurons) Parasympathetic nervous system (visceral motor neurons)

5. THE BRAIN Forebrain Hindbrain Midbrain -Mesencephalon Occipital lobe Cerebellum Medulla Cerebrum Diencephalon Pons Temporal lobe Parietal lobe Frontal lobe Thalamus Hypothalamus Limbic system

6. Frontal lobe Motor area Premotor area Visual association area Occipital lobe Parietal lobe Sensory association area General sensory area Visual area cerebellum Motor speech area Auditory association area Temporal lobe Auditory area The human brain: cerebral lobes, cerebellum and brainstem

7. The human brain: midsagittal surface Thalamus Corpus callosum Frontal lobe Parietal lobe Pons Medulla Spinal cord Cerebellum Midbrain Occipital lobe Hypothalamus Pituitary gland Temporal lobe

8. 1. CEREBRUM: T wo hemispheres separated by the corpus callosum. The outer shell is called the cortex. The left hemisphere appears to be dominant in most people. It controls speech, comprehension, rationality, and logic. The right hemisphere is nondominant in most people. Sometimes called the “ creative” brain , the right hemisphere is associated with affect, behavior, and spatial perceptual functions. Each hemisphere is divided into four lobes

9. Frontal lobes: -Controls voluntary body movement, including movements that permit speaking, thinking, and judgment formation. -Also play a role in the emotional experience, as evidenced by changes in mood and character after damage to this area (fear, aggressiveness, depression, rage, euphoria, irritability, and apathy).

10. Parietal lobes: - The parietal lobes control perception and interpretation of most sensory information (including touch, pain, taste, and body position). -Language interpretation is associated with the left hemisphere of the parietal lobe.

11. Temporal lobes: The upper anterior temporal lobe is concerned with auditory functions, while the lower part is dedicated to short-term memory. impulses carried by the olfactory nerves end in this area of the brain. play a role in the expression of emotions through an interconnection with the limbic system. The left temporal lobe, along with the left parietal lobe, is involved in language interpretation.

12. Occipital lobes: -Primary area of visual reception and interpretation. Visual perception, which gives individuals the ability to judge spatial relationships such as distance and to see in three dimensions, is also processed in this area. -Language interpretation is influenced by the occipital lobes through an association with the visual experience.

13. 2. DIENCEPHALON: The diencephalon connects the cerebrum with lower brain structures. Its major structures include the thalamus, hypothalamus, and limbic system. ● Thalamus: - I ntegrates all sensory input (except smell) on its way to the cortex. - some involvement with emotions and mood. Hypothalamus: - R egulates the anterior and posterior lobes of the pituitary gland. - exerts control over the actions of the autonomic nervous system, and regulates appetite and temperature .

14. ● Limbic system: The limbic system consists of medially placed cortical and subcortical structures and the fiber tracts connecting them with one another and with the hypothalamus. These structures include the hippocampus, mammillary body, amygdala, olfactory tract, hypothalamus, cingulate gyrus, septum pellucidum, thalamus, and fornix. The limbic system, which is sometimes called the “ emotional brain ,” is associated with fear and anxiety; anger and aggression; love, joy, and hope; and sexuality and social behavior.

15. Cingulate gyrus Septum pellucidum Thalamus Hypothalamus Olfactory tract Amygdala Mammillary body Fornix Hippocampus Structures of the limbic system

16. MIDBRAIN MESENCEPHALON : -Structures of major importance in the mesencephalon, or midbrain, include nuclei and fiber tracts . -Extend from the pons to the hypothalamus and are responsible for the integration of various reflexes . V isual reflexes (e.g., automatically turning away from a dangerous object when it comes into view), A uditory reflexes (e.g., automatically turning toward a sound that is heard), R ighting reflexes (e.g., automatically keeping the head upright and maintaining balance).

17. HINDBRAIN Its major structures include pons, medulla and cerebellum . PONS: The pons is the bulbous structure that lies between the midbrain and the medulla - composed of large bundles of fibers - forms a major connection between the cerebellum and the brainstem. -Regulation of respiration and skeletal muscle tone.

18. MEDULLA: -P rovides a pathway for all ascending and descending fiber tracts. -Contains vital centers that regulate heart rate, blood pressure, and respiration, and reflex centers for swallowing, sneezing, coughing, and vomiting. The medulla, pons, and midbrain form the structure known as the brainstem.

19. CEREBELLUM: -Separated from the brainstem by the fourth ventricle, but it has connections to the brainstem through bundles of fiber tracts. -It is situated just below the occipital lobes of the cerebrum. - The functions of the cerebellum are concerned with involuntary movement , such as muscular tone and coordination and the maintenance of posture and equilibrium .

20. NEURONS: -Generate and transmit electrochemical impulses. -Structure  a cell body , an axon , and dendrites . - Cell body contains the nucleus -The dendrites are processes that transmit impulses toward the cell body, and the axon transmits impulses away from the cell body. -Cells called afferent (or sensory ) neurons carry impulses from the periphery to the CNS, where they are interpreted into various sensations. -The efferent (or motor ) neurons carry impulses from the CNS to the muscles and glands of the periphery.

21. SYNAPSES: The junction between two neurons is called a synapse. The small space between the axon terminals of one neuron and the cell body or dendrites of another is called the synaptic cleft . Neurons conducting impulses toward the synapse are called presynaptic neurons and those conducting impulses away are called postsynaptic neurons .

22. NEUROTRANSMITTERS -Chemicals called neurotransmitters are stored in the axon terminals of presynaptic neurons. - Electrical impulses cause the release of these chemicals into the synaptic cleft. - The neurotransmitter combines with receptor sites on the postsynaptic neuron, resulting in a determination of whether another electrical impulse is generated.

23. -Neurotransmitters are responsible for essential functions in the role of human emotion and behavior. -Target for the mechanism of action of many of the psychotropic medications. After a neurotransmitter has performed its function in the synaptic cleft, it either returns to the vesicles in the axon terminals to be stored and used again ( reuptake ), or it is inactivated and dissolved by enzymes.

24. Impulse transmission at a synapse Axon of presynaptic neuron Dendrite of postsynaptic neuron Vesicles of neurotransmitter Receptor site Inactivator (cholinesterase) Inactivated neurotransmitter Neurotransmitter (acetylcholine) Mitochondria

25. CHOLINERGICS ACETYLCHOLINE: Acetylcholine was the first chemical to be identified and proven as a neurotransmitter. ● Location : ANS sympathetic and parasympathetic presynaptic nerve terminals, parasympathetic postsynaptic nerve terminals. CNS cerebral cortex, hippocampus, limbic structures, and basal ganglia. ● Functions : Acetylcholine is implicated in sleep, arousal, pain perception, the modulation and coordination of movement, and memory acquisition and retention. ● Possible implications for mental illness: Increased levels- Depression Decreased level- Alzheimer’s disease, Huntington’s disease, Parkinson’s disease

26. MONOAMINES NOREPINEPHRINE : ● Location : ANS  sympathetic postsynaptic nerve terminals. CNS  cerebral cortex, hippocampus, limbic structures, thalamus, hypothalamus and cerebellum ● Functions : Mood, cognition, perception, locomotion, cardiovascular functioning, sleep and arousal. ● Possible implications for mental illness: Decreased levels- Depression Increased level- Mania, anxiety states, schizophrenia

27. MONOAMINES Dopamine: ● Location : ANS  frontal cortex, limbic structures, basal ganglia, thalamus, posterior pituitary, and spinal cord. ● Functions : Movement and coordination, emotions, voluntary judgment, release of prolactin. ● Possible implications for mental illness: Decreased levels- Parkinson’s disease and Depression Increased level- Mania and schizophrenia

28. MONOAMINES Serotonin : ● Location : ANS  hypothalamus , thalamus, limbic system, cerebral cortex, cerebellum, spinal cord. ● Functions : sleep and arousal, libido, appetite, mood, aggression, pain perception, coordination, judgment. ● Possible implications for mental illness: Decreased levels- Depression Increased level- Anxiety states

29. GAMMA-AMINOBUTYRIC ACID (GABA): Inhibitory amino acid ● Location: hypothalamus, hippocampus, cortex, cerebellum, and basal ganglia of the brain; spinal cord; and in the retina. ● Functions: GABA interrupts the progression of the electrical impulse at the synaptic junction, producing a significant slowdown of body activity. ● Possible implications for mental illness: Decreased levels: anxiety disorders, movement disorders such as Huntington’s disease, and various forms of epilepsy.

30. ABNORMAL NEUROTRANSMISSION Deficient neurotransmitter Excess neurotransmitter Deficient receptors Excess receptors Abnormal neurotransmission causes some mental disorders because of excess/deficient transmission or excess/deficient responsiveness of receptors.

31. NEUROENDOCRINOLOGY - Pituitary gland- under direction of hypothalamus. -Master gland -Two major lobes Anterior lobe (adenohypophysis) –Growth hormone, Thyroid stimulating hormone, Adrenocorticotropic hormone, prolactin, Gonadotropic hormone, Melanocyte stimulating hormone. Posterior lobe (neurohypophysis)- Antidiuretic hormone, Oxytocin

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