Chemical and Nervous Control: Plants and Animals

• Chemical and Nervous Control in Plants and Animals are vital for survival

Objectives

• The aim is to explain the process of chemical and nervous systems
• The presentation compares and contrasts processes in both plants and animals
• It also identifies involved key structures
• The study will describe how these processes contribute to survival

Nervous System

• The nervous system gathers information and elicits responses to stimuli
• It has a complex nerve network with specialized cells, called neurons
• Neurons control and send information inside and outside the body in response to stimuli
• The nervous system regulates breathing, movement, thought, sight and other functions
• The two main divisions of nervous system are the Central Nervous System (CNS), and the Peripheral Nervous System (PNS)

CNS and PNS

• The Central Nervous System (CNS) includes the brain and spinal cord
• The brain is the control center
• The spinal cord connects the brain to other nerves
• The Peripheral Nervous System (PNS) includes nerves branching from the brain and spinal cord to specific body parts
• The PNS is divided into the somatic nervous system (voluntary movements) and the autonomic nervous system (involuntary actions)

Neuron

• The neuron is the nervous system's basic structural and functional unit
• Neurons transmit electrical signals (action potentials or impulses) allowing body parts to respond when stimulated
• Neurons cannot function without essential parts

Parts of a Neuron

• Dendrites are extensions of the cell body that receive chemical signals from other neurons
• Signals are converted into electric impulses, which are then transported to the cell body
• The Soma is the neuron's cell body, containing the nucleus and other organelles
• In vertebrates, the Axon is a slender nerve cell projection that transports electrical impulses (action potentials) away from the cell body
• Most axons are encased in a myelin sheath which speeds up impulse transmission
• Some large axons can transmit impulses at speeds up to 90 meters (300 feet) per second
• Myelin Sheaths protect and electrically insulate nerve cells, made of fatty tissue sleeves
• The Axon Terminal refers to the action endings that make synaptic connections with another nerve or effector cell
• Electrical disturbances in the dendrites or axon create a new wave of impulse down the axon
• Neurons connect through a junction, called the synapse
• When action potential reaches the axon terminal, a series of events stimulate the next neuron
• Neurotransmitters are released to facilitate the transmission of an impulse across a synapse

Synaptic Transmission

• Action potential depolarizes the axon terminal
• Depolarization opens voltage gated Ca2+ channels and Ca2+ enters neuron
• Calcium entry triggers exocytosis of synaptic vesicle contents
• Then neurotransmitters diffuse across the synaptic cleft and binds with receptors on the postsynaptic cell

Categories of Neurons

• Sensory Neurons receive sensory input like touch, temperature, pain, and chemicals
• Interneurons process information and send responses
• Motor Neurons control muscle contractions and movements

Peripheral Nervous System

• The sensory-somatic nervous system voluntarily controls skeletal muscles and provides consciousness of movement
• The autonomic nervous system involuntarily controls bodily functions without conscious control

Automatic Nervous System

• The sympathetic nervous system is active in stress and emergencies, known as "Fight or Flight"
• The parasympathetic nervous system is active in relaxation, known as "Rest and Digest”

Endocrine System

• The endocrine system involves a network of glands that produce and release hormones
• Hormones regulate metabolism, growth, reproduction, mood and other body functions
• The endocrine system maintains homeostasis (balance) in the body alongside the nervous system
• The endocrine and nervous systems coordinate through feedback mechanisms

Feedback Mechanism

• A feedback mechanism either initiates (accelerates) or inhibits (slows down) a process
• Negative feedback counteracts changes to restore normal conditions
• Positive feedback enhances a process until completion

Major Endocrine Glands and Their Functions

• Hypothalamus- It links the neurological and endocrine systems, keeping the body in homeostasis
• Anterior Pituitary- The primary regulator of signals from hypothalamus and other endocrine organs
• Parathyroid Gland- Four tiny glands behind the thyroid that regulate calcium levels in blood, bones, and throughout the body
• Adrenal Gland- Small, triangular glands on top of the kidneys that regulate metabolism, the immunological system, blood pressure, stress response, and other vital activities
• Pancreas- Located behind the stomach, transforms ingested food into energy
• Kidney- Eliminates waste and excess fluid from the body
• Ovaries- Generate and release eggs (oocytes) into the female reproductive canal
• Testes- Produce sperm and testosterone

Coordination Between the Nervous System and Endocrine System

• The nervous and endocrine systems coordinate body functions to maintain homeostasis
• In a stress response ("Fight or Flight"), the nervous system detects danger and signals the adrenal glands
• The endocrine system releases adrenaline (epinephrine) to increase heart rate, breathing, and energy supply
• In regulating blood sugar, the nervous system detects increased blood sugar after eating and signals the pancreas
• The pancreas (endocrine system) releases insulin to lower blood sugar levels

Key Takeaways of Nervous and Endocrine Systems

• The nervous system sends fast, short-term signals through nerves
• The endocrine system sends slow, long-lasting signals through hormones
• Together, these systems regulate stress response, growth, metabolism, and reproduction

Plants: Nervous and Endocrine-Like System

• The nervous and endocrine systems of animals and plants are distinct
• Plants lack a nervous system; however, they exhibit a nervous system-like behavior through chemical substances

Plant Response

• Stationary plants respond to external stimuli like wind, water, and touch
• Responses help attain nutrients
• Plant responses are ways to survive in extreme conditions
• This also helps adapt a defense mechanism for predators, and reproduction

Plant Responses

• The Sensitive Plant (Mimosa Pudica) closes leaflets when touched
• Sunflowers move toward the sun
• Stomata close in response to rapid water loss
• Some plant seeds need a trigger for germination
• Some plants release chemicals as defense mechanisms and warn nearby plants of impending danger

Tropism

• TROPISM is a biological mechanism which enables a plant to move toward (positive tropism) or against (negative tropism) a stimulus
• Roots grow underground moving towards water and gravity
• Leaves usually grow above ground, where they absorb sunlight
• Geotropism/Gravitropism - Plants response / growth due to gravity, may be positive or negative
• Hydrotropism - Plants response / growth in the direction of water
• Thigmotropism - Plants response / growth due to touch
• Phototropism - Plants response / growth in the direction of light

More on Tropism

• Hormones are chemical messengers in plants
• Hormones regulate biochemical and physiological responses, including seed germination, flowering, photosynthesis, fruit ripening, and shoot/root development

Plant Hormones

• Auxin (IAA) is found in the embryo of seeds, meristems of apical buds, and young leaves
• It stimulates stem elongation, root growth, cell differentiation, and branching
• Cytokinins are synthesized in roots and they affect the root growth, cell division, and germination
• Gibberellins are in meristems of apical buds/roots, young leaves, and embryos
• They promote seed/bud germination, stem elongation, and leaf growth
• Brassinosteroids are found in seeds, fruits, shoots, leaves, and floral buds
• They inhibit root growth and retard leaf abscission
• Abscisic Acid is found in leaves, stems, roots, and green fruit that inhibits growth and closes stomata
• Ethylene is found in ripening fruits, nodes of stems, aging leaves, and flowers and promotes fruit ripening