Plant and Animal Responses

• Complexity in organisms increases the distance between cells and organs; in plants and animals, a system is crucial for coordinating their functions as a single unit.
• Simple functions like picking up an object need coordinated actions from eyes, hands, legs, and the vertebral column.
• Environmental changes that organisms respond to are called stimuli.
• An organism's response to stimulus usually involves movement of a body part.
• Homeostasis maintains constant internal body conditions by managing the organism's physiology.
• 'Homeo' refers to the 'same', and 'stasis' is a meaning of 'standing still'.

Coordination in Plants

• Plants lack a nervous system, unlike animals.
• Plants use plant hormones or phytohormones for coordination and control.
• Plant growth includes cell division, enlargement, and differentiation.
• Plant hormones control growth aspects such as dormancy, breaking dormancy, stomata control, leaf fall, fruit growth, ripening, and aging.
• Four major types of plant hormones include auxins, gibberellins, cytokinins, abscisic acid, and ethylene gas.
• Auxins, gibberellins, and cytokinins promote plant growth, while abscisic acid inhibits it.

Key Plant Hormones

• Auxins:
  • Promote cell enlargement and differentiation.
  • Support fruit growth.
  • Enable phototropic and geotropic movements.
  • Found at stem and root tips, moving away from light and towards gravity.
  • They speed up stem growth but slow root growth.
  • Synthetic auxins, like indole-3-acetic acid and 2,4-D, are agricultural and horticultural applications.
• Gibberellins:
  • Boost cell enlargement and differentiation with auxins.
  • Help stem elongation and break seed/bud dormancy, promoting germination.
  • Boost fruit growth.
  • Gibberellic acid (GA3) is sprayed on grape vines to induce parthenocarpy (seedless grapes development).
• Cytokinins:
  • Stimulate cell division.
  • Break seed and bud dormancy.
  • Delay leaf aging.
  • Promote stomata opening and fruit growth.
• Abscisic Acid:
  • Functions mainly as a growth inhibitor.
  • Encourages seed and bud dormancy.
  • Helps close stomata.
  • ABA promotes wilting and leaf/fruit detachment.
• Ethylene Gas:
  • Facilitates fruit ripening.
  • Ripe fruits release it to hasten ripening in raw fruits nearby.
  • Calcium carbide meeting water produces acetylene gas, which helps ripen fruits quickly like ethylene.

Plant Movements

• Movements in plants are tropic or nastic.
• Geotropic Movement:
  • Plant's growth response to gravity.
  • Roots usually show positive geotropic movement, growing with gravity.
  • Stems usually show negative geotropic movement.
• Phototropic Movement:
  • Growth response to light.
  • Stems often show positive movement, while roots are usually negative.
  • Stems bend to light due to higher cell division away from sunlight, increased by auxin secretion.
• Hydrotropic Movement:
  • Roots typically grow toward water sources, indicating positive hydrotropic movement.
• Thigmotropic Movement:
  • Growth response to touch.
  • Seen in climber tendrils.
  • Tendrils coil around supports due to differential auxin-driven cell division.
• Chemotropic Movement:
  • Movement to chemical stimulus.
  • Positive if growth is toward the chemical.
  • Negative if growth is away.
  • Pollen tube growth toward the ovule during fertilization exemplifies positive chemotropism, drawn by sugary substances.
• Nastic Movement
  • Movements that do not rely on the stimulus's direction.
• Seismonastic/Thigmonastic Movements:
  • Caused by mechanical stimuli like contact.
  • Mimosa pudica leaves droop when touched, regardless of touch direction.
  • This occurs from cells losing water, causing leaves to become flaccid.
• Photonastic Movements:
  • Induced by light intensity fluctuations.
  • Many flowers open/close with light changes, like Cestrum nocturnum (moonflower) at night and Dandelion in morning.
• Thermonastic Movements:
  • Movements due to temperature changes.
  • Ex: Mirabilis jalapa blooms late afternoon in response to temperature drop.
• Nyctinastic Movements:
  • 'Sleeping movements’ are stimulated by light and temp.
  • Leaves droop/close toward evening and reopen next morning, seen in clover and oxalis.

Control and Coordination in Animals

• The nervous and endocrine systems control and coordinate animals.
• The nervous system uses nervous tissue, where nerve cells/neurons are the functional units.

The Neuron

• Neuron structure includes dendrites, cyton/soma (cell body), and axon.
• Dendrites receive impulses.
• Cyton/soma processes impulses.
• Axons transmit impulses to other neurons or muscles/glands.
• Axons can be myelinated or non-myelinated; myelinated neurons transmit impulses faster.
• Schwann cells and myelin sheaths insulate axons and increase impulse speed in the peripheral nervous system.
• Nodes of Ranvier are gaps (~1 micrometer) between myelin sheath cells along axons.

Types of Neurons

• Sensory neurons receive signals from sense organs.
• Motor neurons send signals to muscles/glands.
• Association/relay neurons relay signals between sensory and motor neurons.
• Synapse refers to the point of contact between an axon's terminal branches and another neuron's dendrite.
• Neuromuscular Junction (NMJ) is where a muscle fibre meets a motor neuron, carrying nerve impulses from the central nervous system.

Nerve Impulse Transmission

• Nerve impulses pass from one neuron to the next: dendrites → cell body → axon → nerve endings → synapse → dendrites of next neuron.
• A chemical (ex: Acetylcholine) released from the axon tip crosses the synapse/neuromuscular junction to reach the next cell.

Human Nervous System Organs

• Central Nervous System:
  • Composed of the brain and the spinal cord.
  • The brain controls body functions.
  • The spinal cord relays signals between the brain and the peripheral nervous system.
• Peripheral Nervous System:
  • Composed of cranial and spinal nerves (12 cranial nerve pairs exist).
  • Cranial nerves originate from the brain.
  • 31 pairs of spinal nerves come from the spinal cord, connecting to organs below the head.
  • Visceral nerves connect internal organs to spinal cord/brain.
• Autonomous Nervous System:
  • Chain of nerve ganglion along the spinal cord.
  • Controls involuntary actions.
  • Includes sympathetic and parasympathetic systems.
• Sympathetic Nervous System:
  • Controls the 'fight or flight' response.
  • Redirects energy from inessential to survival functions during threats.
  • The adrenal gland releases adrenaline, causing physiological changes to prepare for action.
  • Heart rate and blood pressure are increased.
  • Bronchial tubes dilate.
  • Pupils dilate.
• Parasympathetic Nervous System:
  • Slows organ activity for calming effects.
  • Breathing and heart rates decrease during sleep.
  • Facilitates energy conservation.
  • Maintains steady heart rate and blood pressure.
  • Stimulates digestion and sexual function.

Human Brain

• Human brain, a complex organ mainly of nervous tissue, folds to maximize surface area.
• It has 3 membrane layers called meninges, with cerebrospinal fluid (CSF) in between for shock absorption.
• 3 regions of the human brain include: forebrain, midbrain, and hindbrain.

Parts of the Human Brain

• Forebrain, consists of the olfactory lobes, cerebrum, and diencephalon.
  • Olfactory lobes handle sense of smell.
  • Cerebrum:
    • The largest part of the human brain.
    • Divided into right and left hemispheres connected by the corpus callosum.
    • Each hemisphere controls the body's opposite side.
    • Cerebral hemispheres have an outer cortex of gray matter (cell bodies) and inner medulla of white matter (axons).
    • Each hemisphere includes:
      • Frontal lobe for reasoning, planning, speech, movement, emotions, and problem-solving.
      • Parietal lobe for movement, orientation, and recognition.
      • Occipital lobe for visual processing
      • Temporal lobe for auditory perception, memory, and speech.
  • Cerebrum functions include:
    • Controlling voluntary actions.
    • Sensory perceptions (tactile, auditory).
    • Learning and memory.
  • Diencephalon:
    • Located between cerebrum and midbrain, linking the nervous and endocrine systems.
    • Receives and interprets nerve signals.
    • The pituitary gland responds by secreting hormones.
    • Diencephalon parts:
      • Thalamus: relay centre for pain and pressure.
      • Hypothalamus: Controls sleep/wake cycles, eating/drinking urges, body temperature, the pituitary gland, and blood pressure; and it lies at cerebrum base.
• Midbrain: Connects forebrain and hindbrain, relay neuronal signals and integrates sensory data.
• Hindbrain: Includes the pons, medulla oblongata (medulla), and cerebellum and controls autonomic body systems.
  • Pons relays impulses, regulates respiration.
  • Medulla:
    • Forms brain stem with pons.
    • Controls involuntary functions like heartbeat, respiration, blood pressure, salivation, and vomiting.
  • Cerebellum:
    • Coordinates motor functions, posture, and balance.
    • Controls the precision of voluntary action.

The Spinal Cord

• Spinal cord is a central nervous system part.
• Arising from medulla oblongata, it contains a nerve fibre collection running through the vertebral column.
• It is segmented, and has nerve fibres that form spinal nerves.
• The spinal cord displays grey matter shaped like a butterfly surrounded by white matter.
  • Grey matter is composed of the central canal, and it is filled with cerebrospinal fluid (CSF).
  • White matter contains axons to permit communication between different CNS layers.
• Functions:
  • Connects the brain and the PNS.
  • Provides structural support.
  • Facilitates movement.
  • White matter's myelin insulates electrically.
  • Communicates messages from the brain.
  • Coordinates reflexes.
  • Processes sensory data.
• Reflex Action:
  • Involuntary, automatic response to danger.
  • Reflex Arc:
    • Path of nerve signals in reflex action.
    • Sequence: Receptor → Sensory neuron → Relay neuron → Motor neuron → Effector (muscle).
    • The signal bypasses the brain for quick action.
• Brain/Spinal Cord Protection
  • The brain, protected by fluid-filled cranium.
  • The spinal cord, enclosed in the vertebral column.

Muscular Movements

• Muscle tissues, containing actin and myosin filaments.
• Muscular Movements and Nervous Control is triggered in muscle tissues.
• Calcium ions enter for muscle contractions.
• Contractions result from actin/myosin filaments sliding.
• A contraction results in muscle movement.

Endocrine System

• A ductless gland called endocrine gland.
• A system composed of endocrine glands.
• Endocrine gland secreted product into blood.
• Hormones are its products.
• Protein hormones coordinate body function, growth, metabolism, reproduction, etc.
• Hormones aid but are slower than the nervous system.

Hormones

• Chemical messengers secrete into the blood by specialised tissue.
• In animals, hormones reach targets to stimulate/inhibit processes; they act on cells via receptors.
• Receptor's protein picks hormones for cell action.
• About 20 major animal hormones in the blood influence physiology.
• Hormone levels dependent on stress and minerals.
• A cell, tissue, or organ that secretes chemicals for particular purposes is called a gland.
• Types of Glands:
  • Endocrine are ductless, secreting hormones such as the Pituitary, Thyroid, Adrenal, etc.
  • Exocrine release secretions via ducts (e.g., salivary).
  • Heterocrine have both glands (e.g., pancreas)

Hypothalamus

• A center portion of the human brain located near the pituitary.
• It is a key link connecting the nervous system with the pituitary gland.
• Critical for maintaining internal body homeostasis.
• Connects the endocrine and nervous with the hypothalamus.
• Controls the release of 8 pituitary hormones.
• Regulates body temperature, sleep, appetite, and weight.
• Regulates heart rate, blood pressure, circadian rhythm, and sexual behaviors.

Pituitary Gland

• A pea sized gland at the brain's base, is the 'master gland'.
• This is because it controls other endocrine glands.
• Growth Hormone:
  • GH controls Dwarfism (under-secretion)
  • Gigantism in children and ‘Acromegaly' in adults (over-secretion).
• Releases Thyroid stimulating hormone, MSL, LH, FSH, etc.

Thyroid Gland

• Butterfly-shaped gland in the throat.
• It secretes Thyroxine for regulating metabolism and development.
• Iodine is needed to synthesize thyroxine.
• Iodine deficiency can cause goitre in adults and cretinism in children.

Parathyroid Gland

• It releases parathormone for calcium and phosphorus regulation in bones.

Pineal Gland

• Produces melatonin to regulate sleep patterns.

Pancreas

• Endocrine/exocrine gland behind the stomach.
• It products Insulin/glucagon counteract each other to regulate blood sugar.
• Enzymes break sugar, lipids in food in the pancreas.
• Lack of insulin leads to diabetes.

Adrenal Gland

• Pair of gland above kidneys.
• Decreases in size with age.
• Produces adrenaline or epinephrine.
• It helps regulate metabolism through hormones.
• Cortisol is an anti-inflammatory cortisol.
• Epinephrine increases heart rate and blood glucose when stressed.

Norepinephrine

• Functions with epinephrine to react to stress.
• Mobilizes for action with brain.

Thymus

• Gland between breastbone and lungs.
• Thymosin aids immune system, then reduces post-puberty and replaces cells with fat.

Gonads

• Organs for gamete production (testes/ovaries).
• Make hormones (testosterone/oestrogen).
• Help produce gametes/responsible for sex.

Feedback Mechanism in Hormones

• It should be precise quantity control.
• Body timing hormone.
• Response:
  • Rise in blood sugar stimulates insulin.
  • The levels return to normal.
  • Fall in levels stimulates glucagon.
  • Glucagon stimulates glycogen breakdown.

Test your knowledge of plant and animal responses. Questions cover nastic movements in plants, including thermonastic and photonastic movements and nyctinastic movement. Also included are questions on animal control and coordination, receptors, and hormones such as insulin and glucagon.