FUNCTIOS OF BRAIN IN DETAIL AND BRAIN SR

Functions of brain in detail

1. FUNCTIONS OF BRAIN

2. PONS: The pons is located on the anterior surface of the cerebellum above the medulla oblongata and under the midbrain. It is made up of nerve fibres that join the two cerebellum halves. In the pons some nerve cells function as relay stations while others create cranial nerve nuclei. The pons, which is part of the brainstem, has multiple crucial functions:

3. Regulation of Breathing: The pons contains respiratory centers that help regulate breathing. It receives inputs from the respiratory centers in the medulla oblongata and helps control the rate and depth of breathing. Sleep Regulation: It plays a role in the regulation of sleep and arousal. The pons contains nuclei involved in the sleep-wake cycle, coordinating transitions between different stages of sleep.

4. Facial Movements: Cranial nerve nuclei within the pons are responsible for controlling various facial muscles. These nuclei help in facial expressions, chewing, and other voluntary movements of the face. Sensory and Motor Pathways: The pons serves as a relay station for sensory and motor pathways traveling between the cerebral cortex and the spinal cord. It helps in transmitting signals related to movement, sensation, and coordination.

5. Balance and Coordination: The pons, along with other brainstem structures, contributes to balance and coordination by integrating sensory information from the inner ear, visual system, and proprioceptive receptors. Pontine Reticular Formation: The pons contains the pontine reticular formation, which is involved in various functions such as consciousness, attention, and modulation of pain perception.

6. Overall, the pons plays a vital role in coordinating numerous essential functions, including breathing, sleep regulation, facial movements, sensory and motor integration, and maintaining overall consciousness and alertness.

7. MEDULLA OBLONGATA The medulla oblongata is a crucial part of the brainstem, located just above the spinal cord and below the pons. It's responsible for several vital autonomic functions necessary for survival, including regulating heart rate, blood pressure, breathing, and reflex actions such as swallowing, sneezing, and vomiting. Additionally, it serves as a relay station for nerve signals traveling between the brain and the spinal cord. The medulla oblongata plays a pivotal role in maintaining homeostasis within the body, ensuring that essential physiological processes operate smoothly.

8. FUNCTIONS: Cardiovascular Regulation: Controls heart rate and blood pressure through the cardiac and vasomotor centers. Respiratory Control: Regulates breathing rate and depth to maintain adequate oxygen and carbon dioxide levels in the blood. Reflex Actions: Coordinates reflexes such as coughing, sneezing, swallowing, and vomiting to protect the airway and digestive tract.

9. Sensory Relay: Acts as a relay station for sensory information between the spinal cord and higher brain centers, facilitating appropriate responses to stimuli. Sleep-Wake Regulation: Plays a role in regulating sleep-wake cycles and overall metabolic processes, contributing to homeostasis. In summary, the medulla oblongata plays a crucial role in controlling vital autonomic functions, coordinating reflex actions, relaying sensory information, and maintaining homeostasis within the body.

10. CEREBELLUM The cerebellum, often referred to as the "little brain," is a distinct structure located at the back of the brain, below the cerebral hemispheres. The cerebellum plays a crucial role in coordinating voluntary movements, balance, and posture. This structure receives sensory input from the spinal cord and various sensory systems, as well as input from the cerebral cortex, which is involved in planning and executing movements. It integrates this information to fine-tune motor commands, ensuring smooth and coordinated movements. In addition to motor coordination, the cerebellum is also involved in cognitive functions such as attention, language, and emotional regulation, although its exact role in these processes is still being explored. Overall, the cerebellum is essential for maintaining motor control and overall motor learning.

11. FUNCTIONS: Motor Coordination: It receives information from the sensory systems, spinal cord, and other parts of the brain to regulate motor movements, ensuring they are smooth, coordinated, and precise. Balance and Posture: The cerebellum integrates sensory input from the vestibular system (inner ear) to maintain balance and posture, adjusting muscle tone and limb movements accordingly.

12. Motor Learning: It plays a key role in motor learning and motor memory, allowing us to acquire new skills and refine movements through practice and repetition. Fine-Tuning Movements: The cerebellum fine-tunes motor commands initiated by the motor cortex, ensuring accuracy and efficiency in tasks such as reaching, grasping, and handwriting.

13. Cognitive Functions: While traditionally associated with motor control, the cerebellum also contributes to cognitive functions such as attention, language, working memory, and executive functions. It interacts with the cerebral cortex through extensive connections, influencing cognitive processes. Timing and Sequencing: It regulates the timing and sequencing of movements, ensuring that complex actions are executed in the correct order and at the appropriate speed.

14. Predictive Control: The cerebellum generates internal models of movement, allowing it to predict the consequences of motor commands and make anticipatory adjustments to movements in real-time. Emotional Regulation: Some research suggests that the cerebellum may play a role in emotional regulation and affective processing, influencing mood and emotional responses.

15. Overall, the cerebellum acts as a coordinator and integrator of motor and cognitive functions, contributing to smooth, coordinated movement and higher-order cognitive processes.

16. CEREBRUM The cerebrum is the largest and most prominent part of the human brain, occupying the majority of the brain's volume. It's divided into two hemispheres – the left and right cerebral hemispheres – and is responsible for higher cognitive functions such as thinking, perception, memory, and voluntary movement.

17. Higher Cognitive Functions: This includes processes like thinking, reasoning, problem-solving, decision-making, and creativity. Sensory Processing: The cerebrum interprets information from the senses (sight, hearing, touch, taste, smell) and integrates them to create our perception of the world.

18. Motor Function: It controls voluntary movements of skeletal muscles, allowing us to perform precise and coordinated movements. Memory Storage and Retrieval: The cerebrum plays a key role in forming and storing different types of memories, including short-term and long-term memories.

19. Emotional Processing: It helps regulate emotions and emotional responses, including fear, pleasure, and motivation. Language Processing: The cerebrum, especially the left hemisphere, is heavily involved in language comprehension, production, and expression. Attention and Concentration: It enables us to focus on specific tasks or stimuli while filtering out distractions.

20. Spatial Awareness and Navigation: It helps us understand our position in space and navigate through our environment. Executive Functions: This involves planning, organizing, and executing tasks, as well as controlling impulses and regulating behavior . Perception of Time: The cerebrum allows us to perceive and understand the passage of time.

21. These functions are distributed across different regions of the cerebrum, with complex interactions between various areas and networks within the brain.

22. PERIPHERAL NERVOUS SYSTEM The peripheral nervous system is composed of peripheral nerves and it is subdivided according functional and anatomical criteria.

23. Functional Subdivisions of PNS Functional subdivisions of PNS include the sensory and motor subdivision. Sensory Subdivision This is composed of nerves that arise from various receptors in the peripheral and visceral part of the body that move toward the CNS transmitting sensory impulse.

24. Motor Subdivision This is composed of motor nerves that arise from the CNS (either brain or spinal cord) and transmit motor signals to the effector organs located in the periphery as well as in the visceral parts of the body. Effectors organs include different types of muscles and glands.

25. The motor nerves supplying the voluntary muscles constitute the somatic subdivision while the motor nerves supplying the smooth muscles of viscera, cardiac muscles, and glands (all involuntary effectors) constitute the autonomic subdivision. Autonomic subdivision has two functional parts, the sympathetic and parasympathetic system. All visceral functions are maintained by the dual action of the parasympathetic and sympathetic systems. Some of the peripheral nerves carry both sensory and motor impulse, they are functionally classified as mixed nerves.

26. Anatomical Subdivisions of PNS Anatomical subdivisions of PNS include the cranial and spinal nerves. Spinal Subdivision This constitutes the spinal nerves that connect peripheral parts with the spinal cord. The spinal cord has 31 segments and a pair of spinal nerve arises from each segment. Therefore, there are total 31 pairs of spinal nerves.

27. All spinal nerves are mixed, containing both sensory and motor fibers. The sensory division of the spinal nerve enters into the spinal cord through the dorsal root of spinal cord. These sensory fibers are pseudo-unipolar neuron and their cell bodies form the dorsal root ganglia which lie close to the dorsal root. The motor part of the spinal cord exists from the spinal cord via the ventral root.

28. Functions of Spinal nerves C1-C4: Breathing C2: Head and neck movement C4-C6: Heart rate C6: Shoulder movement C5: Wrist and elbow movement C7-T1: Hand and finger movement T1-T2: sympathetic tone, including temperature regulation

29. T2-T12: Trunk stability L2: Hip motion L3: Knee motion S2-S3: Bowel and bladder activity S2-S4: Sexual function S5: Bowel and bladder activity CO: Innervating coccygeus and levator ani muscles and the skin over the coccух

30. Cranial Subdivision The cranial subdivision of the peripheral nerves are connected with the brainstem. They may be sensory, motor, or mixed. Sensory cranial nerves which arise from receptors in periphery and viscera and terminate in specific nuclei of brainstem. Motor cranial nerves arise from the cerebral cortex, subcortical regions or brainstem areas and connects with the effector organs.

31. Mixed cranial nerves that are composed of both sensory and motor fibers. There are 12 pairs of cranial nerves. These nerves have different names and are numbered in roman from I to XII. Different cranial nerves and their functions are presented in the Table.

32. AUTONOMIC NERVOUS SYSTEM Autonomic nervous system is the second subdivision of the motor part of nervous system which is concerned with the regulation of involuntary activities of the body. It regulates the actions of visceral muscles, cardiac muscle and secretions from the exocrine and endocrine glands. Subdivision and Organization of ANS The two main subdivisions of autonomic nervous system are as follow: Sympathetic nervous system Parasympathetic nervous system

33. Sympathetic nervous system The sympathetic nervous system (SNS) is one of the two main branches of the autonomic nervous system (ANS), responsible for mobilizing the body's resources during times of stress, danger, or excitement.

34. Fight or Flight Response: Activation of the sympathetic nervous system triggers the "fight or flight" response, preparing the body for action in response to perceived threats. Physiological changes include: Increased heart rate and contractility: Beta-adrenergic receptors in the heart increase the rate and force of cardiac contractions, leading to elevated heart rate and cardiac output. Dilation of airways: Beta-adrenergic receptors in the lungs cause bronchodilation, increasing airflow to facilitate oxygen intake.

35. Pupil dilation: Alpha-adrenergic receptors in the iris dilate the pupils, improving vision to detect potential threats. Increased blood flow to skeletal muscles: Blood vessels in skeletal muscles dilate, while those in non-essential organs constrict, redirecting blood flow to muscles for increased strength and agility. Inhibition of digestive and urinary functions: Sympathetic activation suppresses non-essential functions such as digestion and urination to conserve energy for immediate needs.

36. Stress Response: The sympathetic nervous system is closely involved in the body's response to stress, whether physical or psychological. Chronic or excessive activation of the sympathetic system due to prolonged stress can have negative effects on health, contributing to conditions such as hypertension, cardiovascular disease, and gastrointestinal disorders.

37. Parasympathetic nervous system The parasympathetic nervous system (PNS) is the other major branch of the autonomic nervous system (ANS), working in opposition to the sympathetic nervous system to promote relaxation, digestion, and restoration.

38. Rest and Digest Response: Activation of the parasympathetic nervous system promotes a "rest and digest" response, facilitating processes that conserve energy, promote digestion, and support recovery. Physiological changes include: Slowing of heart rate: Parasympathetic stimulation via the vagus nerve (cranial nerve X) decreases heart rate by reducing the firing rate of the sinoatrial node, the heart's natural pacemaker. Constriction of airways: Parasympathetic activation causes bronchoconstriction, reducing airflow to conserve energy during rest.

39. Pupil constriction: Parasympathetic fibers innervating the iris cause pupillary constriction (miosis), which improves near vision and reduces the amount of light entering the eye. Stimulation of digestive functions: Parasympathetic activity enhances gastrointestinal motility and secretion, promoting digestion and absorption of nutrients. It also stimulates the production of saliva and pancreatic enzymes. Relaxation of urinary bladder: Parasympathetic stimulation promotes the contraction of the detrusor muscle and relaxation of the internal urethral sphincter, facilitating urination.

40. Calming Response: The parasympathetic nervous system helps the body conserve energy and restore balance after periods of activity or stress. Activation of the PNS promotes feelings of calmness and relaxation, helping to counterbalance the effects of sympathetic activation.

41. NEUROTRANSMITTER AND NEUROTRANSMISSION IN CNS In the autonomic nervous system (ANS), neurotransmitters play a fundamental role in transmitting signals between neurons and their target cells, such as muscles, glands, and other neurons. The two primary neurotransmitters used in the ANS are acetylcholine ( ACh ) and norepinephrine (NE), also known as noradrenaline. Let's delve into their roles and how neurotransmission occurs in the ANS: (A neurotransmitter is the body's chemical messenger. They are molecules that transmit signals from neurons to muscles, or between different neurons. ) neurotransmitter and neurotransmission in ANS

42. Acetylcholine ( ACh ) : ACh is the primary neurotransmitter released by the preganglionic neurons of both the sympathetic and parasympathetic divisions of the ANS. In the parasympathetic nervous system, ACh is also released by postganglionic neurons to communicate with target cells. At the neuromuscular junction, ACh is released by motor neurons to stimulate skeletal muscle contraction.

43. 2. Norepinephrine (NE) : NE is the primary neurotransmitter released by postganglionic neurons of the sympathetic division of the ANS. NE is also released by the adrenal medulla into the bloodstream as a hormone, where it acts on target tissues throughout the body.

44. RECEPTORS IN ANS The autonomic nervous system (ANS) primarily operates through a series of receptors located on the surfaces of target cells throughout the body. These receptors respond to neurotransmitters released by autonomic neurons, modulating cellular activity and influencing physiological functions. The two main types of receptors in the ANS are cholinergic receptors and adrenergic receptors. (Receptors are biological transducers that convert energy from both external and internal environments into electrical impulses. )

45. 1. Cholinergic Receptors: Cholinergic receptors are activated by the neurotransmitter acetylcholine ( ACh ), which is released by both sympathetic and parasympathetic preganglionic neurons, as well as parasympathetic postganglionic neurons. There are two main types of cholinergic receptors: Nicotinic Receptors: Nicotinic receptors are ligand-gated ion channels found in the autonomic ganglia (both sympathetic and parasympathetic) and at the neuromuscular junction of skeletal muscle fibers. Activation of nicotinic receptors by ACh leads to depolarization of the postsynaptic membrane.

46. Muscarinic Receptors: Muscarinic receptors are G protein-coupled receptors found on the surfaces of target cells innervated by parasympathetic postganglionic neurons. There are several subtypes of muscarinic receptors (M1 to M5), each with different tissue distributions and physiological effects. Activation of muscarinic receptors can lead to a variety of responses depending on the tissue type, including smooth muscle contraction, glandular secretion, and modulation of heart rate.

47. Adrenergic Receptors: Adrenergic receptors are activated by the neurotransmitter norepinephrine (NE), which is released by sympathetic postganglionic neurons. There are two main classes of adrenergic receptors: Alpha Adrenergic Receptors: Alpha receptors are G protein-coupled receptors found on the surfaces of target cells in various organs and tissues, including blood vessels, smooth muscles, and certain glands. There are two subtypes of alpha receptors, alpha-1 and alpha-2, each with distinct physiological effects. Activation of alpha receptors can lead to smooth muscle contraction, vasoconstriction, and inhibition of insulin secretion, among other effects.

48. Beta Adrenergic Receptors: Beta receptors are also G protein-coupled receptors found on the surfaces of target cells. There are three subtypes of beta receptors, beta-1, beta-2, and beta-3, each with different tissue distributions and physiological effects. Activation of beta receptors can lead to increased heart rate and contractility, bronchodilation, vasodilation, and lipolysis, among other effects.

49. Neurotransmission in the ANS : The transfer of information between neurons is called neurotransmission. Sympathetic Nervous System (SNS) : In the sympathetic nervous system, neurotransmission involves a two-step process. First, preganglionic neurons release ACh , which binds to nicotinic acetylcholine receptors ( nAChRs ) on postganglionic neurons in sympathetic ganglia. This stimulates the release of NE from postganglionic neurons. NE then binds to adrenergic receptors (alpha and beta receptors) on target tissues, initiating physiological responses.

50. 2.Parasympathetic Nervous System (PNS) : In the parasympathetic nervous system, neurotransmission also involves a two-step process. Preganglionic neurons release ACh , which binds to nAChRs on postganglionic neurons located in ganglia close to or within target organs. Postganglionic neurons then release ACh , which binds to muscarinic acetylcholine receptors ( mAChRs ) on target tissues, eliciting responses.

51. Neurotransmitter Function: Acetylcholine mediates fast synaptic transmission in both the sympathetic and parasympathetic nervous systems. It plays a key role in initiating signals between neurons and their target cells. Norepinephrine acts as a neurotransmitter in sympathetic postganglionic neurons, facilitating the transmission of signals to target tissues. It modulates various physiological processes, including heart rate, blood pressure, and metabolism.

52. NEURAL PATHWAYS IN ANS The autonomic nervous system (ANS) consists of complex neural pathways that regulate involuntary functions of the body, such as heart rate, digestion, and respiratory rate. These pathways involve intricate connections between different regions of the central nervous system (CNS) and various target organs. Here's an overview of the neural pathways in the ANS:

53. Sympathetic Nervous System (SNS) Pathways: Preganglionic Neurons: Sympathetic preganglionic neurons originate in the thoracic and lumbar regions of the spinal cord (specifically, the intermediolateral cell column). Axons from these neurons exit the spinal cord via the ventral roots and enter the sympathetic chain or trunk, where they synapse with postganglionic neurons. Sympathetic Chain: The sympathetic chain is a series of ganglia running parallel to the spinal cord on each side. Preganglionic neurons synapse with postganglionic neurons either at the same level, a higher level, or a lower level within the sympathetic chain.

54. Postganglionic Neurons: Axons of sympathetic postganglionic neurons extend from the sympathetic chain to target organs throughout the body, including smooth muscles, cardiac muscles, and glands. These neurons release norepinephrine (noradrenaline) as the primary neurotransmitter.

55. Parasympathetic Nervous System (PNS) Pathways: Cranial Nerves: Several cranial nerves, including the vagus nerve (CN X), glossopharyngeal nerve (CN IX), and oculomotor nerve (CN III), contain parasympathetic fibers. These fibers originate from specific nuclei in the brainstem, such as the dorsal motor nucleus of the vagus. Sacral Region of the Spinal Cord: Parasympathetic preganglionic neurons originating in the sacral region (S2-S4) of the spinal cord form part of the pelvic splanchnic nerves. These nerves innervate pelvic organs, including the urinary bladder, reproductive organs, and parts of the large intestine.

56. Ganglia: Parasympathetic ganglia are located close to or within target organs. Preganglionic fibers synapse with postganglionic neurons in these ganglia. Postganglionic Neurons: Parasympathetic postganglionic neurons release acetylcholine as the primary neurotransmitter. They innervate target organs, promoting relaxation, digestion, and other restorative functions.

57. Adrenal Medulla : The adrenal medulla, part of the adrenal glands located on top of the kidneys, is considered an integral component of the sympathetic nervous system. Preganglionic sympathetic fibers directly innervate chromaffin cells in the adrenal medulla. Upon stimulation, these cells release adrenaline (epinephrine) and norepinephrine into the bloodstream, which act as hormones to produce widespread sympathetic effects on target tissues.

58. FUNCTIONS The autonomic nervous system (ANS) is responsible for regulating involuntary physiological processes necessary for maintaining internal homeostasis and responding to environmental stimuli. Its primary functions include: Regulation of Heart Rate and Blood Pressure: The ANS controls heart rate and blood pressure to ensure adequate blood flow to organs and tissues. Sympathetic stimulation increases heart rate and constricts blood vessels, while parasympathetic activity slows heart rate and dilates blood vessels.

59. Respiratory Control: The ANS influences respiratory rate and depth to maintain appropriate levels of oxygen and carbon dioxide in the blood. Sympathetic activation can increase respiratory rate, while parasympathetic activation tends to decrease it. Digestive Processes: The ANS regulates digestion by controlling gastrointestinal motility, secretion of digestive enzymes, and blood flow to the digestive organs. Parasympathetic stimulation enhances digestive functions, promoting activities such as peristalsis and nutrient absorption, while sympathetic activity inhibits these processes.

60. Urinary Function: The ANS controls bladder function and urinary continence. Parasympathetic activation stimulates bladder contraction and relaxation of the internal urethral sphincter, promoting urination. Sympathetic activation relaxes the bladder and contracts the internal urethral sphincter to inhibit urination. Thermoregulation: The ANS helps regulate body temperature by controlling blood flow to the skin and sweat gland activity. During heat regulation, sympathetic activation causes vasodilation and sweating to dissipate heat, while in cold conditions, sympathetic activation leads to vasoconstriction and shivering to conserve heat.

61. Pupillary Response: The ANS controls the diameter of the pupils to regulate the amount of light entering the eyes. Sympathetic stimulation causes pupil dilation (mydriasis) to improve vision in low light conditions, while parasympathetic stimulation causes constriction (miosis) to reduce the amount of light entering the eyes. Sexual Function: The ANS plays a role in sexual arousal and reproductive functions. Parasympathetic activation is involved in erectile responses in males and lubrication in females, while sympathetic activation is associated with ejaculation and orgasm.

62. Emotional Responses: The ANS contributes to emotional responses by regulating physiological changes associated with emotional states. For example, sympathetic activation can lead to increased heart rate and sweating in response to stress or excitement.