Control and coordination

Control and Coordination

• As complexity increases in plants/animals, cells and organs become more distant.
• A system is needed for different parts of organisms to function as a single unit.
• Coordination among different parts is essential for performing particular functions.
• Picking up an object requires coordination: eyes focus, hands grasp, legs bend, backbone adjusts.
• Actions must be coordinated in a sequence for completion.
• Internal body functions require similar mechanisms.

Stimuli and Response

• Stimuli: Environmental changes that organisms respond and react to.
• Response: Organism's reaction to a stimulus, often involving body movement.
• Homeostasis: Maintaining constant internal body conditions, derived from 'homeo' (same) and 'stasis' (standing still).
• Both plants and animals must coordinate and control functions.

Plant Coordination

• Unlike animals, plants lack a nervous system.
• Plant hormones (phytohormones) facilitate control and coordination.
• Plant growth stages: cell division, cell enlargement, cell differentiation.
• Plant hormones regulate growth, dormancy, stomata, leaf fall, fruit ripening, and aging.
• Major plant hormones: auxins, gibberellins, cytokinins, abscisic acid, and ethylene gas.

Plant Hormones Functions

• Auxins, gibberellins, cytokinins: promote plant growth.
• Abscisic acid: inhibits (or prevents) growth.
• Auxins: Promote cell enlargement and cell differentiation and fruit growth; responsible for phototropic/geotropic movements.
• Auxins are produced at stem/root tips.
• Auxins move away from light and towards gravity.
• Auxins accelerate stem growth but slow root growth.
• Synthetic auxins (e.g., indole-3-acetic acid, 2,4-D) used in agriculture/horticulture.
• Gibberellins: Promote cell enlargement and cell differentiation (with auxins).
• Gibberellins aid stem elongation, break seed/bud dormancy, promote germination, promote fruit growth
• Gibberellic acid (GA3) induces parthenocarpy (seedless grapes).
• Cytokinins: Promote cell division, break seed/bud dormancy, delay leaf aging.
• Cytokinins promote stomata opening and fruit growth.
• Abscisic acid: A growth inhibitor that promotes seed/bud dormancy and stomata closure .
• ABA promotes wilting and leaf falling, and causes flower/fruit detachment.
• Ethylene gas: Stimulates fruit ripening.
• Ripe fruits release ethylene gas, speeding up ripening in nearby raw fruits.
• Calcium carbide reacting with water produces acetylene gas, used to quickly ripen fruits.

Plant Movements

• Two main types: tropic and nastic movements.
• Geotropic movement: Growth response to gravity.
• Roots show positive geotropism (grow with gravity), stems show negative geotropism (grow against gravity).
• Phototropic movement: Growth response to light.
• Stems show positive phototropism, roots show negative phototropism.
• Stems bend toward light due to increased cell division away from sunlight, influenced by auxin.
• Hydrotropic movement: Roots grow towards water, a positive hydrotropic movement.
• Thigmotropic movement: Growth response to touch.
  • Seen in climber tendrils.
  • Tendrils coil around supports due to differential cell division via auxin.
• Chemotropic movement: Response to chemical stimulus.
  • Positive chemotropism: Growth towards a chemical.
  • Negative chemotropism: Growth away from a chemical.
  • Pollen tube growth towards the ovule (fertilization) is positive chemotropism.

Nastic Movements

• Nastic Movements are movements independent of stimulus direction.
• Seismonastic/Thigmonastic: Movements due to mechanical stimuli such as contact.
  • Mimosa pudica (sensitive plant) leaves droop upon touch regardless of touch direction.
  • Drooping results from changing water balance; cells lose water, become flaccid.
  • Biophytum sensitivum and Neptunia show similar nastic movements.
• Photonastic: Movements induced by light intensity fluctuations exhibitied by flowers.
  • Flowers open with increasing light (day), close with decreasing light.
  • Cestrum nocturnum (Moon flower) opens at night, closes at dawn.
  • Dandelion blooms in the morning, closes at night.
• Thermonastic: Movements due to temperature changes.
  • Mirabilis jalapa blooms late afternoon/evening (temperature drop), closes mid-morning.
  • Tulip blooms as the temperature rises.
• Nyctinastic: 'Sleeping movements' due to light and temperature alternation.
  • Leaves of clover/oxalis (leguminous plants) droop and close toward evening, rise next morning.

Animal Coordination

• Nervous and endocrine (hormonal) systems mediate control and coordination.
• Nervous System:
  • Composed of nervous tissue.
  • The nerve cell (neuron) is the functional unit.
  • Responsible for control and coordination in complex animals.

Receptors

• Specialized nerve fiber tips that collect information.
• Located in animal sense organs.
• Phono-receptors: Ears that function for hearing and balance.
• Photo-receptors: Eyes, responsible for visual stimuli.
• Thermo-receptors: Skin, detects pain, touch, and heat.
• Olfactory-receptors: Nose, receives smells.
• Gustatory-receptors: Tongue, detects tastes.
• Receptors receive stimuli, send messages via electrical impulses through sensory nerves to spinal cord/brain.
• Effector: Body part (muscle/gland) that responds to stimulus via instructions from nervous system.

Human Nervous System - Neuron

• Structural and functional unit.
• Parts: dendrites, cyton/soma/cell body, and axon.
• Dendrites: Receive impulses from other neurons.
• Cyton/soma: Processes impulses.
• Axon: Transmits impulse to another neuron, muscle, or gland.
• Axon may be myelinated or non-myelinated.
• Impulse transmission is faster in myelinated neurons.
• Schwann cells and Myelin sheaths insulate axons in the peripheral nervous system, increasing impulse speed.
• Nodes of Ranvier are gaps (1 micrometer in diameter) formed between myelin sheath cells along axons or nerve fibers.

Neuron Types

• Sensory neuron: Receives signals from a sense organ.
• Motor neuron: Sends signals to a muscle or gland.
• Association/relay neuron: Relays signals between sensory/motor neurons.
• Synapse: Contact point between axon terminal branches of one neuron and dendrite of another.
• Neuromuscular Junction (NMJ): Point where a muscle fiber meets a motor neuron carrying nerve impulse from the central nervous system.
• Impulses travel via: Dendrites → cell body → axon → nerve endings → synapse → dendrite of next neuron.
• Neurotransmitters (e.g., Acetylcholine) transmit chemical signals across synapses or neuromuscular junctions to reach cells.

Nervous System Organs

• Central Nervous System: Consists of brain and spinal cord.
  • The brain controls body functions.
  • Spinal cord relays signals between the brain/peripheral nervous system.
• Peripheral Nervous System:
  • Includes cranial nerves (12 pairs from the brain to head organs)
  • Spinal nerves (31 pairs from spinal cord to organs below head).
  • Visceral nerves connect internal body organs directly to spinal cord/brain.
• Autonomous Nervous System:
  • Composed of a chain of nerve ganglia alongside the spinal cord.
  • Controls involuntary human body actions.

Autonomous Nervous System Breakdown

• Sympathetic Nervous System: Controls 'fight or flight' response.
  • Prepares body to fight or flee.
  • Directs energy away from non-essential functions towards survival functions.
  • Adrenaline released from the adrenal gland causes physiological changes.

Key Effects of the Sympathetic Nervous System

• Adrenaline is released.
• Increased heart rate and blood pressure.
• Dilated bronchial tubes, allowing greater airflow.
• Dilated pupils for better vision.
• Glycogen converted to increased glucose.
• Muscles contract.
• Decreased saliva and mucus production.
• Decreased urine secretion.
• Activity in the stomach decreases and Motility of the large and small intestine decreases.
• Parasympathetic Nervous System: Slows organ activity causing a calming effect.
  • Breathing rate slows down during sleep.
  • Facilitates energy conservation, maintains steady heart rate/blood pressure.
  • Stimulates digestion and sexual function.

Key Effects of the Parasympathetic Nervous System

• Increased saliva and mucus production
• Increased motility of intestines
• Increased activity in the stomach
• Increased urine secretion
• Bronchial muscles contract and Pupils are constricted
• Decreased heart rate

Human Brain

• Complex organ mainly with nervous tissue.
• Tissues are folded for large surface area in small space.
• Covered by three-layered membranes (meninges).
• Cerebrospinal fluid (CSF) cushions against mechanical shocks.
• Three regions: Forebrain, midbrain, hindbrain.

Brain Parts:

• Forebrain:
  • Composed of olfactory lobes, cerebrum, diencephalon.
• Midbrain:
  • Composed of the hypothalamus.
• Hindbrain:
  • Composed of the cerebellum, pons, and medulla oblongata.

Forebrain structures explained

• Forebrain:
  • Located in the anterior part of the brain.
  • Consists of olfactory lobes, cerebrum, and diencephalon.
• Olfactory lobes:
  • Part of the forebrain that is concerned wth the sense of smell.
• Cerebrum:
  • The largest part of the human brain and is divided into two hemispheres (right and left).
  • Corpus callosum (band of nerve fibers) connects and transmits messages between hemispheres.
  • Each hemisphere controls the opposite side of the body.
  • Outer cortex (grey matter - cell bodies), Inner medulla (white matter - axons of neurons).
  • Each hemisphere has four lobes: Frontal, parietal, occipital, temporal.
• Frontal lobe: -Part of cerebrum is associated with reasoning, planning, speech, movement, emotions, and problem-solving.
• Parietal lobe:
  • Part of cerebrum is associated with movement, orientation, and recognition. Occipital lobe:
  • Part of cerebrum is associated with visual processing.
• Temporal lobe:
  • Part of cerebrum associated with auditory perception, memory, and speech.

Functions of Cerebrum

• Controls voluntary motor actions.
• Sensory perceptions such as tactile and auditory.
• The seat of learning and memory.
• Diencephalon:
  • Located between cerebrum and midbrain.
  • Links nervous and endocrine systems.
  • Receives/interprets signals from nerves; pituitary gland responds via hormones.
  • Consists of thalamus and hypothalamus.

Thalamus and Hypothalamus

• Thalamus: Relay center for pain and pressure.
• Hypothalamus: Lies at the base of the cerebrum and controls various bodily functions. Functions:
  • Sleep-wake cycle (circadian rhythm) regulation.
  • Controls urges for eating and drinking.
  • Body temperature regulation.
  • Pituitary gland control.
  • Blood pressure regulation.
• Connects forebrain with hindbrain.

Midbrain and Hindbrain Functions

• Midbrain: Connects forebrain with hindbrain.
• A portion of the brainstem.
• Located above the pons, at the top of the brainstem, and underneath the cerebellum
• Relays messages between the peripheral and central nervous systems.
• Integrates sensory information from eyes/ears with muscle movements.
• Enables fine adjustments to movements.
• Hindbrain: Composed of the pons, medulla oblongata, and cerebellum.
  • Governs autonomic body systems.
  • Controls heartbeat, breathing, sleep patterns, bladder function, equilibrium, fine motor control.
• Pons: Relays impulses between cerebellum/spinal cord and cerebrum/midbrain.
  • Regulates respiration in the higher parts of the brain like the cerebrum and midbrain.
• Medulla: Part of the brain that forms the brain stem with the pons.
  • Lies at the base of the brain and continues into the spinal cord.
  • Controls involuntary actions like heartbeat and respiration.
  • Controls blood pressure, salivation, and vomiting.
• Cerebellum: Positioned behind the brainstem and midbrain, below the cerebral lobes.
  • Coordinates motor functions.
  • Controls posture, balance, and precision of voluntary action.

Spinal Cord

• Part of the central nervous system.
• Long, pipe-like structure from the medulla oblongata.
• Consists of nerve fibers and runs through the vertebral column.
• Segmented with nerve fiber roots that form spinal nerves.
• Butterfly shapes are in the cross-section has grey matter surrounded by white matter.
• The grey matter includes the central canal with cerebrospinal fluid (CSF).
• The white matter includes axons for communication between CNS layers.
• Functions:
  • Connects the brain and PNS.
  • Provides structural support, posture, and flexible movements.
  • Myelin acts as electrical insulation for the white matter.
  • Communicates messages and Coordinates reflexes..
  • Receives/sends sensory information to the brain for processing.

Reflex Action and Reflex Arc

• Reflex Action: Involuntary movement in response to a sudden danger. e.g touching a hot surface.
• Reflex Arc: Nerve signals path during a reflex.
  • Receptor → Sensory neuron → Relay neuron → Motor neuron → Effector (muscle).
  • Receptor detects danger as sensory neurons sends signals to the relay neuron which is present in the spinal cord.
  • The spinal cord sends signals to the effector through motor neurons.
  • Effector carries out action and removes the receptor away from danger.
• Reflex arc passes at the spinal cord level; signals do not directly travel to the brain.
• Spinal cord generally controls the reflexes.
• Protection of brain and spinal cord: Protected by fluid filled sac and the brain is enclosed in the cranium.
• Muscular Movements and Nervous Control: Muscle tissues have actin and myosin filaments.
  • A nerve signal triggers events, calcium ions enter cells.
  • Actin and myosin slide resulting in muscle contraction.
  • Contraction brings movement.

Endocrine System

• Composed of endocrine glands.
• A ductless gland secretes product directly into bloodstream.
• Hormones (mainly protein) are special messengers controlling body functions (hunger, temperature, mood, growth, reproduction).
• Hormones coordinate with the nervous system.
• Compared to nerves hormones are somewhat slower.
• Chemical messengers are secreted by endocrine tissues directly into the blood.
• Hormones in animals stimulate/inhibit physiological processes by reaching target sites.
• Target cells have receptors that recognize specific hormones action in the cell.
• About 20 major hormones in animals influence physiological processes.
• Hormone levels are influenced by stress, infection, and minerals presence.
• Gland: Cell, tissue, or organ secretes chemical compounds for a particular function.

Types of Glands

• Endocrine Glands: Secrete hormones directly into the bloodstream.
  • Examples: Pituitary, thyroid, adrenal, parathyroid.
• Exocrine Glands: Secrete on surface via ducts.
  • Examples: Salivary glands, releasing saliva via ducts into the mouth, sweat and gastric glands.
• Heterocrine Glands: Have both endocrine and exocrine functions.
  • Example: Pancreas (islets of Langerhans secrete glucagon/insulin)

Hypothalamus

• Tiny region near the pituitary gland in the brain.
• Links the nervous system with pituitary gland.
• Maintains homeostasis.
• Controls endocrine/nervous systems.
• Releases 8 major hormones by the pituitary gland.
• Influences activities to maintain homeostasis (temperature, sleep, appetite, weight, heart rate, blood pressure) .
• Controls circadian rhythm, sexual behavior, and reproduction.

Pituitary Gland & Thyroid Gland

• Pituitary gland: Pea-sized gland at the brain base.
  • A master gland that controls endocrine glands secretions.
  • Under-secretion causes pituitary dwarfism and Over-secretion of GH causes Gigantism children, and Acromegaly adults.
• Thyroid stimulating hormone, Melanocyte Stimulating hormone, Luteinizing hormone, and Follicle stimulating hormone are released by the thyroid gland.
• Thyroid gland: Butterfly-shaped gland in the throat.
  • Secretes thyroxine (reg metabolism., bone growth development, brain function).
  • Iodine is required to synthesize thyroxine.
  • Iodine deficiency causes goiter (thyroid enlargement i)n adults and cretinism (mental/physical growth stoppage) in children.

Parathyroid, Pineal, Pancreas, and Andrenal Glands

• Parathyroid gland: Releases parathormone (regulates calcium/phosphorus in bones).
• Pineal gland: Produces melatonin (regulates sleep patterns).
• Pancreas: Leaf-like gland behind the stomach.
  • Both an endocrine and exocrine gland.
  • Endocrine: Produces insulin and glucagon which regulates sugar levels.
  • Exocrine: Secretes enzymes (breaks down proteins, lipids, carbohydrates nucleic acids).
• and Insulin deficiency leads to diabetes.
• Adrenal gland: Occurs as pairs above kidneys and decreases in size as we age.
  • Secretes adrenaline/epinephrine (aids fight response).
  • Secretes glucocorticoids, mineralocorticoids, and cortisol (anti-inflammatory, aids immune system).
• Regulates metabolism and blood pressure.
• Epinephrine/adrenaline increases heart rate, breathing rate, cardiac muscle contractions and raises blood glucose, accelerates glucose breakdown in skeletal muscles/stored fats.

Norepinephrine, Thymus, and Gonads

• Norepinephrine/noradrenaline works w/ epinephrine to react to stress.
  • Mobilizes the body/brain.
  • Both epinephrine and norepinephrine release stimulated sympathetic nervous system neural impulses.
• Thymus gland: Located between lungs behind breastbone.
  • Produces thymosin (immune system).
  • Decreases in size after puberty replaced by fat.
• Gonads include testes in males and ovaries in females to produces gamete.
  • Testes produces testosterone and the testosterone ovaries produce estrogen and progesterone.
• Testosterone and estrogen aid gamete production, responsible for respective sexual characteristics, where progesterone is the pregnancy hormone.

Feedback Mechanism in the Human Body

• Hormone secretion must be precise with timing and amount released by glands that are built into in the body for regulatory functions.
  • If the blood sugar rises, this is detected by the pancreatic cells in the pancreas that will secrete and produce more insulin in the blood.
  • It is brought back where the increase of blood in the blood sugar levels the secretion of insulin so the blood levels maintained.
  • If the sugar levels fall by then it will stimulate the secretion of secretion glucagon that will breakdown glycogen to to maintain the sugar levels.