COORDINATION AND RESPONSE NOTES (PART 2)
Parts of the Brain and Their Functions
The brain is the body's control center, responsible for processing information and coordinating responses. The
major parts of the brain include the Cerebrum, Cerebellum, and brain stem.
A) Cerebrum
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Largest part of the brain, divided into two hemispheres. It has an outermost layer called the cerebral
cortex. The cerebrum comprises four lobes: frontal, parietal, temporal, and occipital.
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Controls voluntary movements, intelligence, memory, reasoning, and sensory perception.
B) Cerebellum
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Located at the back of the brain.
Responsible for coordination, balance, and fine motor control.
C) Brain stem
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Regulates breathing, sleep cycle, and other involuntary functions
Other parts of the brain include:
1. Medulla Oblongata
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Connects the brain to the spinal cord.
Controls involuntary actions such as breathing, heartbeat, and digestion.
2. Hypothalamus
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Regulates homeostasis, including body temperature, hunger, and water balance.
Controls the pituitary gland and links the nervous and endocrine systems.
3. Pituitary Gland
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Known as the "master gland" because it secretes hormones that regulate other endocrine glands.
Neuron Structure:
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Dendrites: Receive signals.
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Cell Body (Soma): Contains the nucleus.
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Axon: Carries impulses away.
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Myelin Sheath: Insulates the axon and speeds up impulses.
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Synaptic Terminals: Pass the signal to the next neuron or effector.
How Neurotransmitters Move Signals Across Neurons
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Electrical impulses travel along the axon to the synaptic terminal.
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The impulse triggers the release of neurotransmitters (e.g., dopamine, acetylcholine) into the synapse
(the gap between neurons).
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Neurotransmitters diffuse across the synapse and bind to receptors on the next neuron.
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This triggers a new electrical impulse in the receiving neuron.
ENDOCRINE SYSTEM
A hormone is a chemical messenger secreted by endocrine glands that travels in the bloodstream to regulate
body functions.
Endocrine Gland
Hormone Secreted
Function
Pituitary Gland
Growth Hormone (GH)
Stimulates body growth.
Thyroid Gland
Thyroxine
Regulates metabolism.
Pancreas
Insulin, Glucagon
Regulates blood sugar.
Adrenal Gland
Adrenaline
Prepares the body for "fight or flight".
Ovaries
Estrogen, Progesterone
Controls female reproductive functions.
Testes
Testosterone
Controls male reproductive functions.
Role of Adrenaline in Metabolic Activity
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Increases blood glucose by stimulating glycogen breakdown in the liver.
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Raises heart rate and breathing rate to provide more oxygen and energy.
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Dilates airways for better oxygen intake.
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Redirects blood to muscles and brain for quick responses.
Homeostasis is the process of maintaining stable internal conditions within a set range, despite external
changes.
Maintenance of Body Temperature (Vasodilation and Vasoconstriction)
The body regulates temperature through blood vessels near the skin
a) When Too Hot – Vasodilation
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Blood vessels widen (dilate), increasing blood flow to the skin.
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More heat is lost through radiation.
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Sweating helps cool the body as sweat evaporates.
b) When Too Cold – Vasoconstriction
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Blood vessels narrow, reducing blood flow to the skin.
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Less heat is lost, conserving body warmth.
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Shivering generates heat through muscle activity.