Source: # Human Brain and Nervous System *Where mental health has an address in the body : A thought has an address. An address is not a destiny.* ## 3.1 Overview The brain and nervous system control thinking, emotions, memory, movement, senses, hormones, and automatic body functions like breathing and heartbeat. Understanding brain structure helps us understand mental health. #### In more depth This is why a new temper after a head injury is not only 'attitude,' and why a first week of no sleep is not only 'stress.' The organ that thinks can be tired, inflamed, concussed, or starved of thyroid hormone. Mental wellbeing lives in this wiring. It is not only a story. ## 3.2 Major brain regions **Figure 3.1** *Three regions you will meet often: thinking brain, alarm and memory.* **Figure 3.2** *The lobes of the brain and what each is mainly responsible for.* ### Frontal lobe (front of brain) - Planning and organisation. - Decision-making. - Self-control and impulse control. - Personality expression. - Speech production (Broca's area). - Problem-solving. - Judgment. working memory and social judgement. Clinic note. Damage or exhaustion here looks like poor planning, blunt speech, or a person who cannot stop a harmful impulse. That can be injury, mania, substance use, or sleep loss — not always 'bad character.' ### Parietal lobe (top-middle of brain) - Touch sensation. - Spatial awareness. - Body position (proprioception). - Navigation and movement coordination. - Processing sensory information. spatial attention. ### Temporal lobe (sides of brain, near ears) - Hearing and auditory processing. - Memory formation and retrieval. - Language comprehension (Wernicke's area). - Emotion processing. - Face recognition. The temporal lobe also helps us recognise objects and faces. A person who suddenly cannot name familiar faces needs a medical door, not a motivation speech. ### Occipital lobe (back of brain) - Vision and visual processing. - Color recognition. - Object recognition. - Visual memory. ### Limbic system (deep inside brain) - Emotions (fear, anger, pleasure). - Memory formation (hippocampus). - Motivation and reward (amygdala, nucleus accumbens). - Survival behaviours. - Emotional memories. The pieces are separate: hippocampus — new episodic memories and spatial maps; amygdala — salience and threat, emotional memory. Clinic note. Trauma and panic use this neighbourhood heavily. The alarm can fire after the danger has gone. Therapy and, when needed, medicine work here as well as in the frontal lobe that tries to talk the alarm down. ### Cerebellum (back-bottom of brain) - Balance and coordination. - Fine motor control. - Motor learning. - Some cognitive functions. timing and coordination. ### Brainstem (base of brain, connects to spinal cord) - Breathing control. - Heart rate regulation. - Sleep-wake cycles. - Consciousness. - Vital automatic functions. The brainstem keeps the basics running: breathing, heart rate and alertness. This is the landlord who does not negotiate. If consciousness or breathing is failing, this is casualty, not counselling. ## 3.3 The nervous system **Figure 3.3** *How the nervous system is organised.* ### Central nervous system (CNS) - Brain. - Spinal cord. - Processes and coordinates information. ### Peripheral nervous system (PNS) - Nerves throughout the body. - Carries information to and from the CNS. - Two divisions: - Somatic nervous system: voluntary movements. - Autonomic nervous system: automatic functions. In short, the central nervous system is the brain and spinal cord. Everything else is peripheral. Somatic nerves move the limbs you can point to. Autonomic nerves run the interior. ### Autonomic nervous system: two branches #### Sympathetic nervous system (fight-or-flight) - Activates during stress or danger. - Increases heart rate. - Dilates pupils. - Redirects blood to muscles. - Prepares body for action. #### Parasympathetic nervous system (rest-and-digest) - Activates during rest. - Slows heart rate. - Promotes digestion. - Supports healing and recovery. - Conserves energy. The two branches work as a balance, not a light switch. The hypothalamus sits on the border of neural and hormonal control and aims the pituitary at the rest of the endocrine system — including the HPA stress axis and cortisol. Clinic note. Anxiety often feels like a sympathetic system that will not stand down. Depression and exhaustion often feel like a system that will not stand up. ## 3.4 Brain plasticity Neuroplasticity is the brain's ability to change and adapt throughout life. This means: - New neural connections can form. - The brain can recover from injury. - Learning changes brain structure. - Therapy can rewire thought patterns. - Habits can be changed with practice. This is why treatment, therapy, and lifestyle changes can improve mental health. #### In more depth The brain can change, but it takes time and practice. Sleep, movement, practice, and sometimes medicine are how maps are redrawn. A stroke rehab plan and a CBT homework sheet are both plasticity projects. ## 3.5 Messengers A neuron receives on dendrites, sums in the soma, and sends an all-or-none action potential down the axon. At the synapse, chemicals speak. No single chemical is a mood. **Figure 3.4** *A neuron and its synapse.* - > Neuron structure: dendrites, soma, axon, synapse. - Action potential. - Glutamate (excitatory). - GABA (inhibitory). - Acetylcholine (movement, attention, memory). - Dopamine (movement, motivation, reward). - Serotonin (mood, sleep, appetite, impulse). - Norepinephrine (arousal, vigilance). They are listed here because they belong with the living brain. ## 3.6 Taking care of your brain You can look after your brain with ordinary, free habits: 1. **Move.** Regular physical activity increases blood flow, supports new connections, and lifts mood. 2. **Sleep.** Keep regular hours and protect your sleep. 3. **Eat well.** Fruits, vegetables, whole grains, nuts, fish, and plenty of water support brain health. 4. **Stay mentally active.** Reading, puzzles, learning new skills, and conversation keep the brain flexible. 5. **Stay connected.** Social contact is good for the brain at every age. 6. **Manage stress.** Relaxation, hobbies, and breaks lower the load. 7. **Protect your head.** Wear helmets and seat belts. 8. **Limit alcohol and avoid drugs.** They damage brain function. 9. **Get medical check-ups.** Blood pressure, blood sugar, and hearing all effect brain health. **TRY THIS: THE 4-6 BREATH** Sit comfortably. Breathe in gently through your nose for a count of four. Breathe out slowly through your mouth for a count of six. Repeat for two minutes. A longer outbreath activates the body’s calming system and settles the stress response. Practice daily when calm, so that it is easy to use when stressed. ## 3.7 One story A STORY FROM ORDINARY LIFE — THE STROKE THAT TAUGHT A FAMILY ANATOMY After a left-sided stroke, a grandmother lost speech but not song. Relatives said she was being stubborn. A doctor named Broca's area. Naming did not heal her. It stopped the insult. Rehab was slow. The family learned that language and song do not live in one drawer — and that a new 'personality' can be an injured lobe. A STORY FROM ORDINARY LIFE — THE HELMET ARGUMENT A teenager's new rudeness followed a scooter fall without a helmet. Uncles planned a lecture on respect. An emergency doctor planned a scan. The scan was respect for the frontal lobe. ## 3.8 One companion verse One old picture of the same chapter: body as chariot, mind as reins, intellect as driver. If the horses bolt, inspect the chariot — sleep, injury, thyroid — not only the rider's morals. SHLOKA / VERSE **Sanskrit Text:** आत्मानं रथिनं विद्धि शरीरं रथमेव च । बुद्धिं तु सारथिं विद्धि मनः प्रग्रहमेव च ॥ **Pronunciation:** *atmanam rathinam viddhi sariram ratham eva ca |* *buddhim tu sarathim viddhi manah pragraham eva ca ||* **Translation:** Know the self as the rider, the body as the chariot, the intellect as the driver, and the mind as the reins. **Practical Meaning for Daily Health:** Mental health work includes the chariot. A lecture to the rider is not enough if the axle is broken. *Reference — Katha Upanishad 1.3.3–4* **Figure 3.5** *The chariot of the Katha Upanishad: the self rides, the body is the chariot, the intellect drives, the mind is the reins and the senses are the horses.* ### Reflection 1. Which region in this chapter best matches a problem you have seen in a relative — impulse, memory, vision, alarm, or sleep? 2. When did someone in your house blame 'attitude' for what might have been a body event? 3. What one sleep or safety habit this week would help the chariot, not only the rider? 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