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Human Body - I: Control and Coordination

Page 1 - The study topic: Human Body - I: Control and Coordination - Key ideas introduced:

  • All living organisms sense changes in the environment and respond to them. A change in the environment to which an organism responds is called a stimulus. This coordination is crucial for survival and allows organisms to adapt to their surroundings.
  • Organisms react to changes in light, sound, physical contact, taste, and smell.
    • Main topics or sections highlighted: Nervous system, Endocrine system, Nerve cell, Parts of the nervous system, Reflex action, Adolescence.
    • The nervous and endocrine systems coordinate to maintain the body's internal environment (homeostasis).
    • Components mentioned (from the diagram references):
  • Brain, Spinal cord, Nerves (Cranial nerves, Spinal nerves)
  • Hypothalamus, Pituitary gland
  • Thyroid gland, Adrenal glands, Pancreas
  • Ovaries (in females), Testes (in males)
    • System classifications:
  • Central nervous system (CNS)
  • Peripheral nervous system (PNS)
    • Notes on structure and function (in brief):
  • The nervous system serves as a control system that sends electrical messages called nerve impulses throughout the body.
  • The endocrine system is composed of glands that secrete hormones directly into the bloodstream, traveling to target organs to induce effects.
    • Key terminology:
  • Stimulus: A change in the environment that elicits a response.
  • Nerve impulses: Electrical messages carried by neurons.
  • Hormones: Chemical messengers released into the bloodstream by endocrine glands.
    • Concepts introduced for subsequent detail (to be elaborated on in later pages):
  • Nerve cell (Neuron)
  • Parts of the nervous and endocrine systems
  • Reflex action
  • Adolescence

Page 2 - Nerve cell (Neuron): structural and functional unit of the nervous system.

  • Parts of a neuron (Fig. 4.2):
    • Cell body (cyton): central portion containing cytoplasm and nucleus.
    • Dendrites: short, branched extensions from the cell body; receive nerve impulses and transmit them toward the cell body.
    • Axon: single long fibre that transmits impulses away from the cell body. Ends in axon terminals; terminals contain synaptic bulbs with neurotransmitters.
    • Synapse: junction between two neurons where chemical neurotransmitters are released to propagate the impulse to the next neuron; impulse transmission is directional (one-way).
    • Myelin sheath: fatty covering around long axons, providing insulation and significantly increasing the speed of nerve impulse transmission.
  • Types of neurons (Fig. 4.3):
    • Sensory neuron: carries impulses from sense organs to brain/spinal cord.
    • Motor neuron: carries impulses from brain/spinal cord to muscles and glands to produce a response.
    • Association (mixed) neuron: located in brain/spinal cord; relays impulses between sensory and motor neurons.
      ► Parts of the Nervous System
  • The human nervous system has three parts: CNS, PNS, and ANS.
  • Central Nervous System (CNS): Brain and spinal cord; connected to the body via nerves.
  • Peripheral Nervous System (PNS): Nerves extending from CNS to other parts of the body. Two types:
    • Cranial nerves ( originate from the brain ). There are 12 pairs; they carry sensory and motor signals (e.g., Optic nerve, Auditory nerve).
    • Spinal nerves ( originate from the spinal cord ). There are 31 pairs; they are mixed nerves (sensory + motor).
  • Autonomic Nervous System (ANS): Controls involuntary bodily functions to maintain homeostasis; composed of sympathetic and parasympathetic divisions. They often act in opposition to regulate internal organs.
    • Sympathetic nervous system prepares the body for action (fight/flight): increases heart rate, redirects blood flow to muscles, etc.
    • Parasympathetic nervous system works to restore and re-establish normal conditions (rest/digest).
    • Both systems can be active simultaneously and balance each other depending on the situation.

Page 3 - The cerebrum, cerebellum, and medulla oblongata are the three main parts of the brain (Fig. 4.4(a)).

  • Functions described:
    • Cerebrum: The largest part; responsible for memory, speech, thought, sight, smell, taste, hearing, and all voluntary actions. It is highly folded (surface area increases due to ridges and furrows) to accommodate more neurons and support complex cognitive functions.
    • Cerebellum: Located at the back under the cerebrum; maintains body balance and coordinates muscular activity.
    • Medulla oblongata (brain stem): The lowest part of the brain; controls involuntary actions of internal organs (e.g., breathing, heartbeat, peristalsis).
  • Spinal cord: Cylindrical structure protected by the vertebral column; protected by meninges; continues from brain down the spine. It transmits sensory impulses from organs to brain and motor impulses from brain to muscles. It also acts as a control centre for many reflex actions.
  • Meninges: Three-layered protective membranes surrounding brain and spinal cord; cerebrospinal fluid cushions and protects the brain.
  • CSF (cerebrospinal fluid): Provides protection against mechanical shocks.
  • Meningitis: Inflammation of meninges, commonly due to bacterial infection in CSF; can be life-threatening; symptoms include headache, fever, stiff neck. (Fact File: not a disease diagnosis but a note of risk.)

Page 4 - Autonomic Nervous System (ANS): Pair of nerve fibre chains located on either side of the backbone; regulate internal body functions; concept of opposing actions by the two branches.

  • Sympathetic nervous system: prepares the body for action (fight/flight) with increased heart rate and energy mobilization.
  • Parasympathetic nervous system: restores body to normal/rest conditions.
  • Example: Sympathetic increases heartbeat; Parasympathetic slows it down; both can be active to regulate organ function.
  • Reflex Action: A sudden, involuntary response to a stimulus that occurs without conscious thought. These actions are often protective, allowing rapid responses to potential harm. Examples include withdrawing a hand from a sharp pin or from a hot object.
    • Most reflexes are controlled by the spinal cord, resulting in very quick actions.
    • Reflex arc: The neural pathway for a reflex action; shortest path from receptor to effector (Fig. 4.5).
  • Components of the reflex arc:
    • Receptor: detects stimulus and creates an impulse (e.g., pain receptors in the skin).
    • Sensory neuron: transmits the impulse toward the spinal cord.
    • Association neuron (mixed neuron): located in the spinal cord; connects sensory to motor neuron; converts sensory impulse to motor impulse.
    • Motor neuron: carries impulse away from the spinal cord to the effector organs (muscles or glands).
    • Effector: the muscle or gland that responds to the stimulus.
  • Some reflexes become conditioned reflexes through learning and experience (e.g., reflexes that can be conditioned such as watering of the mouth on seeing smell of food, or applying brakes while driving).

Page 5 - Endocrine System overview:

  • It consists of glands that secrete chemical messengers called hormones directly into the bloodstream; hormones travel to target organs and elicit specific responses.
  • Endocrine glands are ductless (unlike exocrine glands).
  • Hormones act in very low concentrations and have long-lasting effects on target organs. Their secretion is often regulated by a negative feedback loop to maintain homeostasis.
  • Most hormones are proteins, and their secretion must be tightly regulated; excess or deficiency can cause disorders.
  • Glands typology:
    • Exocrine glands: secrete products through ducts to specific locations (e.g., sweat glands secrete sweat onto skin; salivary glands secreting saliva into the mouth).
    • Endocrine glands: secrete hormones directly into the bloodstream; target organs located away from the source. Example: adrenaline secreted by adrenal glands affecting the heart.
  • Important endocrine glands (Table 4.1 overview in text): pituitary, thyroid, adrenal, and pancreas with specific hormones and functions elaborated below.
  • Hormone concepts:
    • Pituitary gland (the master gland) secretes several hormones that stimulate other glands to release their hormones. Example: Thyroid-stimulating hormone (TSH) stimulates the thyroid to secrete thyroxine.
    • Other pituitary hormones include growth hormone, adrenocorticotropic hormone (ACTH), antidiuretic hormone (ADH), prolactin, and oxytocin.
    • Growth hormone-related conditions:
    • Gigantism: Oversecretion of growth hormone in childhood leads to abnormally tall stature (Fig. 4.6(c)).
    • Dwarfism: Undersecretion of growth hormone results in short stature (Fig. 4.6(d)).
    • Antidiuretic hormone (ADH) or vasopressin: Undersecretion causes Diabetes insipidus, characterized by excessive urination and thirst due to loss of water.
    • Thyroid gland: A bilobed gland located in front of the neck; secretes thyroxine (T4).
    • Thyroxine regulates basal metabolic rate, growth, and mental development.
    • Iodine is required for thyroxine synthesis; iodine deficiency can cause goitre (enlargement of thyroid).
    • Goitre: Visible neck swelling due to enlarged thyroid from iodine deficiency (Fig. 4.7(b)).
    • Cretinism: Iodine deficiency in infancy causes stunted growth and mental retardation.
    • Myxoedema: In adults, insufficient thyroxine reduces metabolic rate, increases body weight, and causes facial swelling due to fluid retention (Fig. 4.7(d)).
    • Adrenal glands: Pair of triangular glands atop each kidney; secrete adrenaline (epinephrine) and corticosteroids.
    • Adrenaline (emergency hormone) increases heart rate and blood flow to muscles to cope with stress or danger.
    • Corticosteroids help regulate metabolism of carbohydrates, fats, and proteins, and help regulate salt and water balance.
    • Pancreas: A gland with both exocrine and endocrine functions.
    • Exocrine: produces pancreatic juice to help digestion via the pancreatic duct into the duodenum.
    • Endocrine: produces insulin and glucagon to regulate blood sugar levels.
    • Hormones overview table (Table 4.1) provides location, hormones secreted, and functions for the glands discussed (pituitary, thyroid, adrenal, pancreas, ovaries, testes).
  • Endocrine glands: quick reference
    • Pituitary: base of the brain; hormones include Growth Hormone, TSH, Prolactin, Oxytocin, ADH; Functions include growth regulation, stimulating thyroid, milk production, uterine contraction, and water balance.
    • Thyroid: in front of the neck; Thyroxine; regulates growth and cellular oxidation leading to energy production.
    • Adrenal: above kidneys; Adrenaline, Corticosteroids; regulate stress response and metabolism.
    • Pancreas: below stomach; Insulin and Glucagon; regulate blood glucose.
    • Ovaries: estrogen and progesterone; regulate female sexual development and cycles.
    • Testes: testosterone; regulate male sexual development and sperm production.

Page 6 - The endocrine system continued:

  • The pituitary gland acts as a master gland, secreting hormones that stimulate other endocrine glands to release their hormones (e.g., TSH stimulates the thyroid to produce thyroxine). This system often operates through negative feedback loops, where the product inhibits its own production.
  • Growth hormone (GH) influences body growth; excess leads to gigantism; deficiency leads to dwarfism.
  • Antidiuretic hormone (ADH) regulates water balance by controlling how much water kidneys reabsorb.
  • Endocrine glands and hormones (Table 4.1 content, summarized):
    • Gland: Pituitary; Location: Base of the brain; Hormones: Growth hormone, TSH, Prolactin, Oxytocin, ADH; Functions: Growth regulation, stimulates thyroid, stimulates milk production, uterine contraction/lactation, water balance.
    • Gland: Thyroid; Location: Front of the neck; Hormone: Thyroxine; Function: Regulates body growth and cellular oxidation for energy production.
    • Gland: Pancreas; Location: Below the stomach; Hormone: Insulin, Glucagon; Function: Regulates blood glucose levels.
    • Gland: Adrenal; Location: Above the kidneys; Hormones: Adrenaline, Corticosteroids; Function: Fight/flight response, metabolism regulation.
    • Gland: Ovaries; Location: On both sides of the uterus; Hormones: Estrogen, Progesterone; Function: Female sexual development/ovarian functions.
    • Gland: Testes; Location: In scrotal sacs; Hormone: Testosterone; Function: Male sexual development and sperm production.
  • Key clinical notes:
    • Simple goitre results from iodine deficiency.
    • Cretinism arises from iodine deficiency in infancy, causing stunted growth and mental retardation.
    • Myxoedema results from insufficient thyroxine in adults, with reduced metabolic rate and edema of face/hands.
    • Diabetes mellitus relates to insulin deficiency or resistance, with symptoms like polyuria (excess urination), polydipsia (thirst), polyphagia with weight loss and fatigue.

Page 7 - Thyroid gland details (recap):

  • Location and function summarized; iodine is essential for thyroxine synthesis; goitre is a visible sign of iodine deficiency; cretinism results from deficiency in infancy; myxoedema results from adult thyroxine deficiency.
  • Adrenal gland details (recap):
  • Produces adrenaline for rapid stress response; corticosteroids regulate metabolism and salt/water balance.
  • Pancreas specifics (recap):
  • Contains both exocrine and endocrine components; endocrine part releases insulin and glucagon to regulate blood sugar.
  • Images and figures referenced:
    • Fig. 4.8: Adrenal gland anatomy.
    • Fig. 4.9: The pancreas gland arrangement.
  • Quick clinical notes:
    • Diabetes mellitus due to insulin deficiency or ineffective insulin use leads to high blood glucose; manage via regulation of diet, insulin therapy, and monitoring.

Page 8 - Additional endocrine gland details and table continuation (Table 4.1):

  • Insulin: produced by the pancreas; lowers blood glucose by promoting uptake of glucose into cells and promoting glycogen synthesis in the liver.
  • Glucagon: produced by the pancreas; raises blood glucose by promoting glycogen breakdown to glucose in the liver.
  • Adrenaline (epinephrine): produced by adrenal glands; part of the acute stress response; increases heart rate and energy supplies.
  • Corticosteroids: produced by adrenal cortex; regulate metabolism of carbohydrates, fats, and proteins; help regulate salt and water balance.
  • Additional notes:
    • The pancreas has both exocrine and endocrine functions; exocrine secretion is pancreatic juice delivered to the duodenum via the pancreatic duct; endocrine function involves regulating blood sugar through insulin and glucagon.
    • Ovaries produce estrogen and progesterone; testes produce testosterone.
  • Questions section (Practice): A. Technical terms
    1. The master gland: the

      answer: Pituitary gland
    2. A condition due to insufficient iodine intake in the diet:

      answer: Simple goitre
    3. Emergency hormone:

      answer: Adrenaline
    4. The gland that secretes hormone regulating the blood sugar level:

      answer: Pancreas
    5. A condition due to undersecretion of antidiuretic hormone:

      answer: Diabetes insipidus
    • B. True/False practice (correct the false statements by changing the first/last word):
    1. Hormones are released into the bloodstream directly. (True)
    2. Thyroid-stimulating hormones are secreted by the thyroid gland. (False; they are secreted by the pituitary gland; correct statement: Thyroid-stimulating hormone is secreted by the pituitary gland.)
    3. Iron is required for the production of thyroxine. (False; iodine is required.)
    4. The exocrine secretion of pancreas is insulin. (False; exocrine secretion is pancreatic juice; endocrine secretion includes insulin.)
    5. Adrenal glands are located above the stomach. (False; above the kidneys.)

Page 9 - Adolescence and puberty (definition and context):

  • Adolescence is the period between 11 and 19 years of age, marking the transition from childhood to adulthood.
  • Puberty is the period during which sexual development takes place; puberty marks the beginning of the path to becoming an adult.
  • Hormones involved in puberty include sex hormones and growth hormones.
  • Physical changes during adolescence (highlights):
    • Reproductive organs mature and become functional.
    • In females: pituitary releases follicle-stimulating hormone (FSH) and luteinizing hormone (LH) which enable ovaries to function; ovaries enlarge; female sex hormones (estrogen and progesterone) are produced; egg maturation and release (ovulation).
    • In males: testes enlarge; testosterone produced; penis growth; vocal changes with growth of larynx and Adam's apple; voice deepens as length of vocal cords increases.
    • Hair growth in pubic region, arms, legs, and armpits; facial hair in males.
    • Breasts develop in females; menstrual cycle begins; pelvis widens.
    • Physical changes in males include broader chest and shoulders and increased muscle mass.
    • Skin changes: oil and sweat glands activate; acne and pimples may occur.
    • Height and weight increase during adolescence.
  • Emotional changes during adolescence (psychosocial):
    • Mood swings due to hormonal changes; peers influence behavior, risk-taking, and possible unhealthy habits (alcohol, drugs, smoking).
    • Desire for greater control over life and future planning; family support is important.
    • Self-consciousness and anxiety, particularly around peers and the opposite sex; emphasis on appearance affecting self-esteem.
    • Encouragement to accept physical identity and maintain confidence.

Page 10 - Health and personal hygiene during adolescence (practical guidance):

  • Eat regular, healthy meals; exercise; ensure adequate rest.
  • Maintain personal hygiene: daily bath, use deodorant/antiperspirant to control body odor.
  • Wash face twice daily with mild cleansers to reduce acne; avoid picking or squeezing pimples to prevent scars.
  • Genital hygiene; use sanitary napkins during menstruation and proper disposal methods.
  • Stress management and mental well-being:
    • Stress triggers adrenal adrenaline release; manage stress with strategies such as:
    • Yoga and meditation to reduce stress and promote calmness; yoga also improves flexibility, muscle tone, and circulation.
    • Time management: plan tasks in advance and allocate sufficient time to prevent last-minute panic; include rest and recreation.
    • Physical activity: walking, jogging, swimming, cycling, and aerobic dancing improve cardiovascular fitness and energy levels.
    • Hobbies: engage in activities like sketching, painting, listening to music, reading to maintain balance and reduce stress.
    • Rational thinking: practical, well-reasoned decision-making for coping with stress.
  • Fill-in-the-blank practice (Page 10 exercise):
    1. Puberty/Adolescence distinction: Puberty is the period between 11 to 19 years and marks transition to adulthood. (Answer: Puberty/Adolescence - appropriate term was Puberty in the prompt.)
    2. The testes secrete testosterone.
    3. Adam's apple develops due to enlargement