Understanding the nervous system
From the book – Chapter 3: Human Brain and Nervous System
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.
Read the full chapter – Chapter 3: Human Brain and Nervous System
Stories from real life
- The Alarm That Would Not Switch Off – Priya was seventeen and preparing for her board exams in Jaipur. Whenever she opened her Physics paper, her heart hammered, her palms turned cold and wet,…
- After the Bike Fall – Arjun, twenty-two, rode his motorbike to a call centre in Hyderabad. One rainy night he skidded and hit his head. He had no helmet on. He…
- Learning to Paint at Seventy – Haridas, seventy-one, retired from the railways in Kolkata and found the days strangely empty. He began forgetting where he had put his glasses and worried that…
- Midnight Scrolling and the Growing Brain – Fifteen-year-old Chloe lived in Manchester and was known at school for her sharp wit. Lately she had been dozing in class and saying things she regretted.…
Shloks
- Katha Upanishad 1.3.3–4 – Know the self as the rider, the body as the chariot, the intellect as the driver, and the mind as the reins.
More on this topic: The brain, hormones and body chemistry behind your moods
More questions
- Peripheral nervous system (PNS) – the nervous system
- Autonomic nervous system: two branches – the nervous system
- Parasympathetic nervous system (rest-and-digest) – the nervous system
- Understanding brain plasticity – the brain and nervous system
- Understanding messengers – the brain and nervous system
- Understanding taking care of your brain – the brain and nervous system
- Which brain region is mainly responsible for planning, decision-making and self-control?
- What is true: the limbic system is primarily involved in…?
- The "fight-or-flight" response is controlled by which part of the nervous system?
- What is true: the occipital lobe is primarily responsible for…?