Control and Coordination in Biology

Overview

• Discussion on the nervous system and hormonal responses in control and coordination.
• Nervous system: rapid communication through electrical impulses.
• Hormonal response: gradual changes using hormones like insulin, glucagon, etc.
• Endocrine system: ductless glands producing hormones.

Nervous System vs Endocrine System

• Nervous system: Mode of Communication - Electrical impulses, Speed - Rapid, Duration - Short.
• Endocrine system: Mode of Communication - Hormones, Speed - Slower, Duration - Long-lasting.
• Important to know comparisons in mode of communication, speed, target tissues, etc.

Neurons and Nervous System

• Types of neurons: Sensory, Relay, Motor.
• Neuron structure: Cell body, dendrons, axon.
• Myelinated neurons have Schwann cells forming a myelin sheath for insulation.
• Action potential jumps between nodes of Ranvier (Saltatory conduction).

Types of Neurons

• Sensory Neurons: Carry impulses from receptors to relay neurons or the brain.
• Relay Neurons: Transmit impulses between sensory and motor neurons.
• Motor Neurons: Carry impulses to effectors (muscles or glands).

Sensory Receptors

• Photo receptors: Rod and cone cells detect light.
• Thermo receptors: Detect temperature changes.
• Mechano receptors: Sense pressure, taste, smell, balance.

Action Potential

• Resting Potential: -70 mV, maintained by sodium-potassium pumps.
• Action Potential: Triggered by stimulus, depolarization when threshold (-55 mV) is reached.
• Repolarization: Occurs after action potential, includes hyperpolarization (refractory period).
• All or Nothing Principle: Action potential occurs only if threshold is reached.

Synapse

• Neurotransmitters transmit impulses across synapses.
• Synapse Process: Action potential at synaptic knob, calcium ions cause neurotransmitter release, neurotransmitter binds to receptors on postsynaptic neuron.
• Unidirectional Transmission: Ensures directionality of signal.

Neuromuscular Junction

• Similar to synapse, but between neuron and muscle fiber.
• Neurotransmission: Acetylcholine released, binds to muscle fiber receptors causing contraction.

Muscle Contraction

• Sliding Filament Theory: Actin and myosin interaction, triggered by calcium ions.
• T-Tubules and Sarcoplasmic Reticulum: Role in muscle contraction.

Plant Control and Coordination

• Venus Flytrap: Rapid response to touch using action potential similar to nervous signal in animals.
• Tropisms: Growth responses to stimuli like light (phototropism), gravity (gravitropism).

Plant Hormones

• Auxins: Control cell elongation.
• Gibberellins: Stimulate germination, growth processes.
• Ethylene: Ripening of fruits.

Summary

• The lecture covered both animal and plant control and coordination mechanisms.
• Importance of understanding neuron types, action potential, synapses, muscle contraction, and plant hormones in the context of biology.