Difficulty: Introductory to Intermediate | Prerequisites: Chapter 1 notes (biopsychosocial model).
Chapter 2 is the anatomy and physiology backbone of the course. This first part covers the nervous system (how the brain and body communicate) and the endocrine system (how hormones regulate long-duration responses, especially stress). You need this material to understand later chapters on stress, coping and psychoneuroimmunology. If you are shaky on the difference between "central" and "peripheral" or between "sympathetic" and "parasympathetic," this is the chapter that sorts it out.
The nervous system is split into the CNS (brain and spinal cord) and the peripheral nervous system (somatic for voluntary movement, autonomic for involuntary). The autonomic branch divides again into sympathetic (fight-or-flight) and parasympathetic (rest-and-digest). The endocrine system works alongside the nervous system through hormones, with the adrenal glands playing a central role in the body's stress response.
Central nervous system (CNS)
The brain and spinal cord. It carries voluntary nerve impulses to skeletal muscles and skin and involuntary impulses to muscles and glands.
Peripheral nervous system (PNS)
All nerve tissue outside the brain and spinal cord. Divided into the somatic and autonomic nervous systems.
Somatic nervous system
Controls voluntary movement. Think of it as the part you use when you decide to pick up a cup.
Autonomic nervous system (ANS)
Controls organs that operate involuntarily (heart, lungs, digestive tract). You do not have to think about breathing; the ANS handles it.
Sympathetic nervous system
The "fight-or-flight" branch of the ANS. Mobilises the body for action: increases heart rate, dilates pupils, diverts blood to muscles.
Parasympathetic nervous system
The "rest-and-digest" branch. Maintains and restores equilibrium after sympathetic activation.
Medulla
Hindbrain structure that regulates heart rate, blood pressure and respiration. Also receives sensory information about CO2 and O2 levels.
Pons
Links the hindbrain and midbrain. Also helps control respiration.
Cerebellum
Coordinates voluntary muscle movement, balance, equilibrium, muscle tone and posture.
Thalamus
Forebrain relay station. Recognises sensory stimuli and sends them to the cerebral cortex for processing.
Hypothalamus
Regulates cardiac functioning, blood pressure, respiration, water balance, appetites, hunger and sexual desire. In simple terms, this small structure is the control centre for many survival-related functions.
Cerebral cortex
The largest portion of the brain. Handles higher-order intelligence, memory, personality and interpretation of sensory input. Divided into frontal, parietal, temporal and occipital lobes, each with its own memory storage area.
Limbic system
A network involved in stress and emotional responses. Key structures include the amygdala (threat detection), hippocampus (emotionally charged memories), cingulate gyrus and septum.
Chronic traumatic encephalopathy (CTE)
A degenerative brain disorder caused by repeated or serious head injuries. In simple terms, the long-term brain damage associated with contact sports and concussions.
Neurotransmitters
Chemical signals that allow neurons to communicate. Think of them as the molecular messengers that cross the gap between nerve cells.
Catecholamines (epinephrine and norepinephrine)
Neurotransmitters released when the sympathetic nervous system is activated. They drive the physical signs of the stress response (increased heart rate, higher blood pressure, dilated pupils).
Dementia
Literally "deprived of mind." A broad term for cognitive decline severe enough to interfere with daily life. Affects more than 55 million people worldwide.
Endocrine system
A system of glands that governs slow-acting responses of long duration through hormones released into the bloodstream.
Adrenal glands
Small glands on top of each kidney. The adrenal medulla secretes catecholamines (fast stress response); the adrenal cortex secretes corticosteroids (slower, sustained stress response).
Corticosteroids
Hormones from the adrenal cortex that increase protein and fat mobilisation, increase access to bodily energy stores, inhibit antibody formation and inflammation, and regulate sodium retention.
The nervous system is a network of interconnected nerve fibres. It divides into two main branches:
CNS (central nervous system): brain and spinal cord
PNS (peripheral nervous system): everything outside the CNS
Sensory nerve fibres carry input from receptors to the brain and spinal cord. Motor nerve fibres carry output from the CNS to muscles and organs, producing both voluntary and involuntary movement.
The PNS splits further:
Somatic nervous system: controls voluntary movement
Autonomic nervous system: controls involuntary organ function
Sympathetic: mobilises the body for action (fight or flight)
Parasympathetic: maintains and restores equilibrium (rest and digest)
Medulla: regulates heart rate, blood pressure, respiration. Receives sensory info about CO2 and O2 levels.
Pons: links hindbrain to midbrain; assists with respiration control.
Cerebellum: coordinates voluntary muscle movement, balance, equilibrium, muscle tone and posture.
Thalamus: recognises sensory stimuli and relays them to the cerebral cortex.
Hypothalamus: regulates cardiac functioning, blood pressure, respiration, water balance, appetites, hunger and sexual desire.
Cerebral cortex: the largest brain region. Handles higher-order intelligence, memory, personality and sensory interpretation. Four lobes (frontal, parietal, temporal, occipital), each with its own memory and association areas.
Handles stress and emotional responses. Key structures:
Amygdala: threat detection
Hippocampus: emotionally charged memories
Cingulate gyrus, septum and areas of the hypothalamus also contribute to emotional functioning
Chronic traumatic encephalopathy (CTE) is a degenerative brain disorder from repeated or serious head injuries.
CNS neurons communicate via electrical and chemical signals called neurotransmitters. When the sympathetic nervous system is activated, it prompts secretion of epinephrine and norepinephrine (collectively called catecholamines). These drive the physical stress response: increased heart rate, higher blood pressure, blood diverted to muscles, faster breathing, slowed digestion and dilated pupils.
The endocrine system governs slow-acting, long-duration responses through hormones. The adrenal glands (small glands on top of each kidney) are central to the stress response.
Under stress, two pathways activate simultaneously:
Sympathetic nervous system to adrenal medulla: secretes catecholamines (epinephrine and norepinephrine), producing rapid effects: heart rate increases, blood pressure rises via vasoconstriction, blood diverts to muscle tissue, breathing rate increases, digestion slows, pupils dilate.
Pituitary gland to adrenal cortex: secretes corticosteroids, producing slower, sustained effects: increased protein and fat mobilisation, increased access to bodily energy storage, inhibited antibody formation and inflammation, regulated sodium retention.
This dual pathway explains why stress produces both an immediate rush (catecholamines) and a prolonged physiological shift (corticosteroids).
Students often confuse the somatic and autonomic nervous systems. Somatic = voluntary (you choose to move your arm). Autonomic = involuntary (your heart beats without you deciding).
Students assume "sympathetic" means caring or compassionate. In this context, sympathetic means activating, mobilising the body for action. The parasympathetic system is the calming one.
Students think the adrenal glands produce only adrenaline. They produce both catecholamines (from the medulla) and corticosteroids (from the cortex), each on a different timeline and through a different pathway.
Students sometimes treat the limbic system and the cortex as separate. The limbic system includes parts of the hypothalamus, and the cortex interprets information the limbic system flags, so they work together.
⚠️ Know the full nervous system hierarchy: CNS vs. PNS, somatic vs. autonomic, sympathetic vs. parasympathetic. Diagram-style questions are common.
⚠️ Be able to name the three hindbrain structures and the three forebrain structures with their functions.
⚠️ The dual stress pathway (sympathetic to adrenal medulla for catecholamines; pituitary to adrenal cortex for corticosteroids) is heavily tested. Know which pathway is fast and which is slow.
⚠️ Amygdala = threat detection, hippocampus = emotional memory. These two limbic structures come up frequently.
True or False: The somatic nervous system controls involuntary organ function.
False. That is the autonomic nervous system.
Fill in the blank: The ______ links the hindbrain and midbrain and helps control respiration.
Pons.
True or False: Corticosteroids are secreted by the adrenal medulla.
False. Corticosteroids come from the adrenal cortex.
Fill in the blank: The ______ is the limbic structure responsible for threat detection.
Amygdala.
True or False: The parasympathetic nervous system mobilises the body for action.
False. That is the sympathetic nervous system. The parasympathetic restores equilibrium.
Q: Trace the path of the stress response through the sympathetic-adrenal medulla pathway. What hormones are released and what are their effects?
A: Stress activates the sympathetic nervous system, which stimulates the adrenal medulla to secrete catecholamines (epinephrine and norepinephrine). Effects include increased heart rate, elevated blood pressure via vasoconstriction, blood diverted to muscle tissue, increased breathing rate, slowed digestion and dilated pupils.
Q: How does the adrenal cortex pathway differ from the adrenal medulla pathway in the stress response?
A: The adrenal cortex pathway runs through the pituitary gland and produces corticosteroids rather than catecholamines. It is slower but longer-lasting, increasing protein and fat mobilisation, increasing access to energy stores, inhibiting antibody formation and inflammation, and regulating sodium retention.
Q: Name the three structures of the hindbrain and one function of each.
A: (1) Medulla: regulates heart rate, blood pressure and respiration. (2) Pons: links hindbrain and midbrain, helps control respiration. (3) Cerebellum: coordinates voluntary muscle movement, balance and posture.
Q: What is the difference between the sympathetic and parasympathetic nervous systems?
A: The sympathetic nervous system mobilises the body for action (fight or flight). The parasympathetic nervous system maintains and restores equilibrium (rest and digest). They are complementary branches of the autonomic nervous system.
Q: What is CTE and what causes it?
A: Chronic traumatic encephalopathy is a degenerative brain disorder caused by repeated or serious head injuries. It is associated with contact sports and repeated concussions.
The sympathetic-adrenal medulla and pituitary-adrenal cortex pathways are the physiological foundation for everything in later stress chapters. Understanding how catecholamines and corticosteroids work explains why chronic stress suppresses immune function (Chapter 2 Part 2, immune system section) and contributes to cardiovascular disease. The autonomic nervous system also connects to Chapter 3's discussion of health behaviour change, since stress-related arousal influences habits like eating, smoking and alcohol use.
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