CBSE · Class 10 · Biology · Chapter 6

Control and Coordination — Formula Sheet

Board Formulas

9 formulas

1.Reflex Arc Pathway★
$Stimulus \to Receptor \to Sensory neuron \to Spinal cord \to Motor neuron \to Effector \to Response$
Fast, involuntary response coordinated by the spinal cord (not the brain). Example: hand withdrawal from a hot object.
2.Neuron Structure Pathway
$Dendrite \to Cell body \to Axon \to Axon terminal \to Synapse$
Signal enters via dendrites, travels ELECTRICALLY along the axon, and crosses the synapse CHEMICALLY via neurotransmitters.
3.Divisions of the Human Nervous System
$Nervous System = CNS (Brain + Spinal Cord) + PNS (Nerves)$
PNS = somatic (voluntary skeletal muscle) + autonomic (involuntary; splits into sympathetic 'fight-or-flight' and parasympathetic 'rest-and-digest').
4.Three Parts of the Brain★
$Brain = Forebrain + Midbrain + Hindbrain$
Forebrain: thinking, memory, sensory. Midbrain: visual/auditory reflexes. Hindbrain: cerebellum (balance), medulla (heartbeat, breathing), pons (bridge).
5.Adrenaline (Stress Hormone)★
$Adrenaline (epinephrine): C_{9} H_{13} N O_{3}$
Secreted by the ADRENAL MEDULLA. Increases heart rate, BP and blood glucose — the fight-or-flight response.
6.Insulin (Blood-Sugar Regulator)
$Insulin: peptide, 51 amino acids, \sim 5.8 kDa$
Secreted by β-cells of the islets of Langerhans in the PANCREAS. LOWERS blood sugar by promoting cellular glucose uptake. Deficiency → diabetes mellitus.
7.Thyroxine (Metabolism Hormone)
$Thyroxine (T_{4}): C_{15} H_{11} I_{4} N O_{4}$
Secreted by thyroid gland; contains IODINE. Regulates metabolic rate. Iodine deficiency → goitre.
8.Auxin Redistribution (Phototropism)
$Light \Rightarrow auxin migrates to shaded side \Rightarrow cells elongate \Rightarrow shoot bends towards light$
Positive phototropism in shoots. Auxin is produced at the shoot tip.
9.Feedback Control of Hormones
$↑ Hormone \to target effect \to↓ gland activity (negative feedback)$
High thyroxine → pituitary secretes LESS TSH → thyroid slows down. Keeps hormone levels constant.