SIVYER PSYCHOLOGY

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THE NERVOUS SYSTEM

Rebecca Sivyer

SPECIFICATION: THE DIVISIONS OF THE NERVOUS SYSTEM ARE CENTRAL AND PERIPHERAL - SOMATIC AND AUTONOMIC

  • The divisions of the human nervous system are central and peripheral (somatic and autonomic), and the basic functions of these divisions.

  • The autonomic nervous system and the fight or flight response. The James-Lange theory of emotion.

KEY TERMS

  • CNS (Central Nervous System): The central nervous system comprises the brain and spinal cord. It processes and integrates information, initiates responses, and controls most bodily functions.

  • Brain: The brain is the central control organ of the nervous system responsible for various cognitive, sensory, motor, and regulatory functions.

  • Spinal Cord: The spinal cord is a bundle of nerves that extends from the brain and runs down the back, serving as a communication pathway between the brain and the rest of the body.

  • PNS (Peripheral Nervous System): The peripheral nervous system comprises nerves and ganglia outside the central nervous system. It connects the CNS to the limbs and organs, facilitating communication between them.

  • Autonomic Nervous System (ANS): The autonomic nervous system regulates involuntary bodily functions such as heart rate, digestion, and respiration. It includes the sympathetic and parasympathetic divisions.

  • Somatic Nervous System (SNS): The somatic nervous system is responsible for voluntary muscle movements and sensory perception, allowing conscious control over actions like walking or talking.

  • Fight or Flight is a physiological response to stress or danger characterized by increased heart rate, heightened alertness, and other changes that prepare the body to confront or escape from a threat.

  • Adrenalin (Epinephrine): A hormone and neurotransmitter that plays a key role in the "fight or flight" response. It increases heart rate, dilates airways, mobilizes energy stores, and promotes glucose release.

  • Noradrenalin (Norepinephrine): Another neurotransmitter and hormone involved in the "fight or flight" response. It helps regulate heart rate, blood pressure, and the body's response to stress.

  • Glucose: A simple sugar and an essential source of energy for the body's cells. During the "fight or flight" response, the body releases glucose into the bloodstream to provide energy for immediate use.

THE NERVOUS SYSTEM

https://human.biodigital.com/gar/anatomy/female/nervous-system/

The human nervous system is an intricate web of nerve cells that transmit messages between the brain, spinal cord, and various body regions, facilitating seamless communication among all bodily components. At the helm of this intricate system is the brain, often described as the body's powerhouse despite comprising a mere 2% of its overall weight.

This remarkable organ is characterized by an astonishing network of billions of neural connections, intricately woven to enable the brain to govern the body's myriad functions. Notably, the brain assumes the role of a vigilant overseer, ensuring the smooth operation of bodily processes. Additionally, it houses higher functions that grant us consciousness and define our identities. In essence, the brain is the cornerstone of our existence, orchestrating the symphony of our biological and cognitive experiences.

DIVISIONS OF THE NERVOUS SYSTEM

The human nervous system is an intricate web of nerve cells that transmit messages between the brain, spinal cord, and various body regions, facilitating seamless communication among all bodily components. At the helm of this intricate system is the brain, often described as the body's powerhouse despite comprising a mere 2% of its overall weight.

This remarkable organ is characterized by an astonishing network of billions of neural connections, intricately woven to enable the brain to govern the body's myriad functions. Notably, the brain assumes the role of a vigilant overseer, ensuring the smooth operation of bodily processes. Additionally, it houses higher functions that grant us consciousness and define our identities. In essence, the brain is the cornerstone of our existence, orchestrating the symphony of our biological and cognitive experiences.

THE CENTRAL NERVOUS SYSTEM (CNS)

The central nervous system (CNS), consisting of the brain and spinal cord, serves two primary roles: governing behaviour and overseeing the body's physiological functions. To fulfil these functions effectively, the brain must receive sensory input from receptors like those in the eyes, ears, and skin, and it must transmit instructions to the muscles and glands throughout the body. This intricate process involves the spinal cord, a bundle of nerve cells intricately connected to the brain, extending along the length of the spinal column.

THE BRAIN

The brain is a highly complex and vital organ located within the skull. It acts as the body's control centre, overseeing and coordinating various functions and processes. Without delving into specific brain structures, here's a more detailed description:

The brain is composed of billions of nerve cells known as neurons, which communicate with each other through electrical and chemical signals. It plays a crucial role in processing sensory information from the environment, regulating bodily functions, and enabling conscious experiences.

Some key functions of the brain include:

  1. Cognition: The brain is responsible for various cognitive processes, including thinking, memory, problem-solving, decision-making, and language comprehension.

  2. Emotion: It regulates emotions, influencing how we feel and respond to different situations. Emotional centres in the brain help control mood and emotional reactions.

  3. Motor Control: The brain controls voluntary and involuntary muscle movements, allowing us to perform tasks, walk, talk, and engage in various activities.

  4. Sensory Processing: It receives, interprets, and processes sensory information from the environment, such as sight, sound, touch, taste, and smell.

  5. Homeostasis: The brain helps maintain the body's internal balance (homeostasis) by regulating functions like temperature, heart rate, blood pressure, and hormonal secretion.

  6. Consciousness: It is responsible for our awareness and consciousness, allowing us to perceive the world, experience emotions, and have self-awareness.

  7. Autonomic Functions: The brain controls vital autonomic functions, such as breathing, heart rate, digestion, and circulatory functions, often without conscious effort.

Overall, the brain is a multifaceted organ that plays a central role in our daily lives and is essential for our survival and well-being. It orchestrates an intricate symphony of activities that allow us to think, feel, move, and adapt to our ever-changing environment

THE SPINAL CORD

The primary role of the spinal cord is to serve as a vital communication pathway between the brain and the rest of the body. This critical function enables the brain to closely monitor and regulate various bodily processes, including essential functions such as digestion and breathing, as well as the coordination of voluntary movements.

The spinal cord achieves this by establishing connections with different body regions through pairs of spinal nerves. These spinal nerves extend from various segments of the spinal cord and establish links with specific muscles and glands. For instance, spinal nerves originating from the thoracic region of the spinal cord facilitate the transmission of messages to and from the chest and certain parts of the abdomen.

Moreover, the spinal cord contains specialized networks of nerve cells that facilitate the execution of rapid, automatic reflex actions, all without requiring direct input from the brain. For example, if you inadvertently touch something hot, these neural circuits enable you to instinctively withdraw your hand as a protective response.

In cases where the spinal cord sustains damage, the regions of the body served by spinal nerves below the site of injury may become disconnected from the brain's control, leading to impaired or halted functioning in those specific areas. This underscores the critical role the spinal cord plays in facilitating essential bodily functions and reflexes.

THE PERIPHERAL NERVOUS SYSTEM

When we talk about the 'peripheral' nervous system (PNS), we're basically referring to the parts on the outer edges of the larger nervous system. Imagine it as the outskirts of the spine The PNS includes all those nerves that extend from and go beyond the central nervous system (CNS), which includes the brain and spinal cord.

So, what does the peripheral nervous system do? Well, it acts like a communication hub, taking signals from the CNS and sending them to various organs, muscles, and body parts that aren't right next to the spine. It's like the middleman for nerve messages.

When you put the CNS and PNS together, they create a harmonious system that allows your body to communicate effectively and control all sorts of functions, helping you interact with the world around you and keeping your internal environment stable

Now, if we look at the PNS in a bigger picture, it can be split into two main parts:

  • THE SOMATIC NERVOUS SYSTEM (SNS): Often referred to as the "voluntary" nervous system.

  • THE AUTONOMIC NERVOUS SYSTEM (ANS): Often associated with "involuntary" functions of the body

THE AUTONOMIC NERVOUS SYSTEM (ANS): is divided into two parts .

STHE SYMPATHETIC NERVOUS SYSTEM (SNS) AND THE PARASYMPATHETIC NERVOUS SYSTEM (PNS) - SEE THE DIAGRAM BELOW

THE NERVOUS SYSTEM

THE SYMPATHETIC NERVOUS SYSTEM (SNS): Prepares the body for "fight or flight" responses in emergencies, increasing heart rate and other physiological responses.

THE PARASYMPATHETIC NERVOUS SYSTEM (PNS) : Parasympathetic NS promotes "rest and digest" activities, slowing heart rate and aiding in digestion

THE SOMATIC NERVOUS SYSTEM

The voluntary nervous system

The voluntary somatic nervous system, often referred to as the somatic nervous system (SNS), is a component of the peripheral nervous system (PNS) that controls voluntary muscle movements and sensory information. It is responsible for conscious and intentional actions, such as moving your limbs, talking, or walking. The somatic nervous system includes both sensory and motor neurons that allow you to perceive sensory stimuli from your environment and respond to them through purposeful muscle movements.

The somatic system includes 12 pairs of cranial nerves that come straight from the brain and 31 pairs of spinal nerves that come from the spinal cord. These nerves do two main jobs:

  1. Sensory Neurons: They carry messages from your body to your brain, so your brain knows what's happening around you.

  2. Motor Neurons: These do the opposite. They take instructions from your brain and send them to different body parts, like telling your muscles to move when you want to walk or pick something up.

The cool thing about the somatic system is that it can also handle quick reflex actions without needing the brain to think about it. For example, when you touch something hot, your hand moves away super fast without you even deciding to do it. That's thanks to the somatic system.

THE AUTONOMIC NERVOUS SYSTEM

 When you are taking a drink or typing on a keyboard, you’re performing voluntary actions that you’re conscious of. However, your body also carries out actions without your conscious awareness. E.g. your heart beats and your intestines digest food. The ANS regulates involuntary actions like these. This system is necessary because the body wouldn’t work as efficiently if you had to think about it.

The ANS has two parts: the sympathetic and parasympathetic. Both of these divisions tend to regulate the same organs but have opposite effects. This is because of the neurotransmitters associated with each division. Generally, the sympathetic division uses the neurotransmitter noradrenaline, which has stimulating effects, and the parasympathetic division uses acetylcholine, which has inhibiting effects.  

QUIZ

Absolutely! Here's an expanded quiz with 20 questions for GCSE students to identify functions of the Somatic Nervous System (SNS) and the Autonomic Nervous System (ANS):

QUIZ: Somatic vs Autonomic Nervous System Functions

Indicate whether each function is primarily controlled by the Somatic Nervous System (S) or the Autonomic Nervous System (A).

  1. Chewing food: (S/A)

  2. Heart rate increasing during a stressful event: (S/A)

  3. Kicking a football: (S/A)

  4. Saliva production: (S/A)

  5. Adjusting the focus of the eye for clear vision: (S/A)

  6. Balancing while standing on one foot: (S/A)

  7. Production of stomach acid for digestion: (S/A)

  8. Shivering in cold temperatures: (S/A)

  9. Typing on a keyboard: (S/A)

  10. Blushing when embarrassed: (S/A)

  11. Breathing rate changing while sleeping: (S/A)

  12. Urinary bladder control: (S/A)

  13. Smiling or frowning: (S/A)

  14. Release of adrenaline during a fight-or-flight response: (S/A)

  15. Maintaining posture: (S/A)

  16. Regulation of blood glucose levels: (S/A)

  17. Constricting blood vessels to regulate body temperature: (S/A)

  18. Reacting to a sudden loud noise: (S/A)

  19. Yawning: (S/A)

  20. Blinking to keep the eyes moist: (S/A)

THE PARASYMPATHETIC NERVOUS SYSTEM (REST AND DIGEST MODE)

Think of the Autonomic Nervous System (ANS) as your body's automatic manager. It's like having a built-in system that keeps things running smoothly without you even thinking about it. The PNS is often associated with the "rest and digest" mode, which is when your body is at rest and working to maintain a stable internal environment. Here's how it helps with homeostasis and body temperature: Here's how it works:

  1. Balance Keeper: The ANS helps maintain balance and stability inside your body. Just like a thermostat keeps your room at a comfortable temperature, the ANS keeps your body's functions in check.

  2. Two Teams: The ANS has two teams: the "Sympathetic" team and the "Parasympathetic" team. They're like opposites.

  3. Sympathetic - Get Up and Go: When you need to get up and go, like when you're facing a challenge or need to react quickly, the Sympathetic team kicks in. It's your body's way of saying, "Let's go, we've got work to do!" It makes your heart beat faster, opens up your airways, and gives you a burst of energy. Think of it as the "active mode."

  4. Parasympathetic - Rest and Relax: On the other hand, when you're just chilling out, having a meal, or winding down, the Parasympathetic team takes over. It's like your body's way of saying, "Time to relax and recharge." It slows your heart rate, helps with digestion, and conserves energy. Think of it as the "resting mode."

  5. Energy Saver: Here's where the energy conservation part comes in. Most of the time, your body is in Parasympathetic mode because, well, we're not always in a fight-or-flight situation. This resting mode helps save energy for when you really need it.

  6. Temperature Regulation: The PNS helps regulate body temperature by promoting processes like sweating and blood vessel dilation. When your body temperature rises above the normal range, the PNS helps cool you down by activating sweat glands and causing blood vessels to expand near the skin's surface, allowing heat to dissipate.

  7. Digestion and Energy Conservation: As part of its "rest and digest" functions, the PNS promotes efficient digestion and nutrient absorption. This ensures that your body gets the energy and nutrients it needs to function properly.

  8. Heart Rate and Blood Pressure: The PNS helps maintain a stable heart rate and blood pressure by slowing down your heart rate and reducing the force of heart contractions when resting. This prevents unnecessary strain on your cardiovascular system.

So, the ANS is like the behind-the-scenes manager that keeps your body running smoothly, adapting to different situations, and making sure you have the energy you need when it counts. It's pretty amazing how our bodies care for us without us even noticing! If we think of the SNS as pushing an individual into action when faced with an emergency, then the parasympathetic nervous system (PNS) relaxes again once the emergency has passed. Whereas the SNS causes the heart to beat faster and the blood pressure to increase, the PNS slows the heartbeat down and reduces blood pressure. Another benefit is that digestion will begin again under PNS influence. Because the PNS involves energy, conservation and digestion, it’s sometimes called the body’s rest and digestion system.

THE SYMPATHETIC NERVOUS SYSTEM/FIGHT-FLIGHT RESPONSE

The SNS is primarily involved in responses that help us to deal with emergencies (fight or flight) such as increasing heart rate and blood pressure and dilating blood vessels in the muscles. Neurons from the SNS travel to virtually every organ and gland within the body, preparing the body for the rapid action necessary when the individual is under threat. 

E.g. The SNS causes the body to release stored energy, pupils to dilate and hair to stand on end. It slows bodily processes that are less important in emergencies such as digestion and urination.

A more detailed explanation of the various effects of sympathetic arousal on the body:

  • Blood Pressure Increase: Sympathetic arousal causes blood vessels to constrict, which raises blood pressure. This is because it helps push blood more forcefully through your arteries, ensuring that vital organs receive enough oxygen and nutrients during times of stress or danger.

  1. Heart Rate Increase: The sympathetic nervous system prompts your heart to beat faster and more forcefully. This ensures that your circulatory system can pump blood quickly to your muscles, brain, and other essential organs when needed for physical exertion or stress response.

  2. Digestion Suppression: Sympathetic arousal slows down or temporarily suspends digestive processes. In a "fight or flight" situation, your body prioritizes sending resources and energy to areas like your muscles and brain rather than to digestion.

  3. Saliva Suppression: Your mouth may become dry during sympathetic arousal because saliva production decreases. This helps conserve fluids in your body for other essential functions during stressful situations.

  4. Urinary Function: The sympathetic nervous system reduces urine production by constricting the bladder and relaxing the urinary sphincters. This conserves fluids and energy during the "fight or flight" response.

  5. Release of Bowels and Urine: In some cases of extreme stress, the sympathetic nervous system can trigger the release of bowels and urine. This is a natural response to make the body lighter for quick physical reactions.

  6. Pupil Dilation: The pupils of your eyes dilate (widen) during sympathetic arousal. This allows more light to enter the eyes, improving your ability to see clearly and react to potential threats.

  7. Secretion of Hormones: Sympathetic arousal prompts the adrenal glands to release hormones like adrenaline (epinephrine) and noradrenaline (norepinephrine). These hormones prepare your body for action by increasing alertness, energy, and focus.

  8. Glucose Release: The liver releases stored glucose (sugar) into the bloodstream. This extra energy source is readily available for the body to use during times of heightened activity or stress.

  9. Bronchial Dilation: The sympathetic nervous system causes the bronchioles in your lungs to dilate (expand), allowing for increased airflow. This ensures that your body receives enough oxygen to meet the demands of heightened physical activity.

These responses collectively prepare your body to respond effectively in high-stress situations, such as encountering a threat or needing to react quickly to a challenging situation.

QUIZ

Certainly! Here's a quiz for GCSE students to identify whether the following functions are associated with Sympathetic Arousal (often linked to the "fight-or-flight" response) or Parasympathetic Arousal (often linked to "rest-and-digest" activities):

QUIZ: Sympathetic vs Parasympathetic Arousal

Indicate whether each function is primarily associated with Sympathetic Arousal (S) or Parasympathetic Arousal (P).

  1. Increased heart rate: (S/P)

  2. Stimulation of digestion: (S/P)

  3. Dilation of pupils: (S/P)

  4. Decreased heart rate: (S/P)

  5. Constriction of airways: (S/P)

  6. Stimulation of tear production: (S/P)

  7. Increased sweating: (S/P)

  8. Reduced urinary output: (S/P)

  9. Relaxation of bladder muscles: (S/P)

  10. Acceleration of metabolic rate: (S/P)

  11. Constriction of blood vessels: (S/P)

  12. Stimulation of saliva production: (S/P)

  13. Slowing down of intestinal activity: (S/P)

  14. Increased blood flow to muscles: (S/P)

  15. Stimulation of gallbladder: (S/P)

  16. Reduction of pupil size: (S/P)

  17. Enhancement of blood clotting: (S/P)

  18. Release of glucose from the liver: (S/P)

  19. Relaxation of gastrointestinal tract: (S/P)

  20. Promotion of genital arousal: (S/P)

QUESTION YOUR KNOWLEDGE

Put the components of the nervous system into the right boxes.

GCSE

  1. EITHER: (2 marks)

    Draw the diagram above and label it correctly

    Name and put the term in the correct box.

  2. Define the Central Nervous System (CNS). (2 marks)

  3. Explain the primary functions of the CNS. (4 marks)

  4. Describe the role of the spinal cord within the CNS. (3 marks)

  5. What are the main components of the Peripheral Nervous System (PNS)? (2 marks)

  6. Differentiate between the somatic nervous system and the autonomic nervous system within the PNS. (4 marks)

  7. Provide an example of a reflex action controlled by the PNS. (2 marks)

  8. Describe the structure and function of sensory neurons in the nervous system. (3 marks)

  9. Explain the role of motor neurons in transmitting signals within the nervous system. (3 marks)

  10. How does the somatic nervous system differ from the autonomic nervous system regarding neuron functions? (Additional 2 marks)

  11. Define the sympathetic nervous system and the parasympathetic nervous system. (4 marks)

  12. Compare and contrast the effects of the sympathetic and parasympathetic divisions on bodily functions during the "fight or flight" response and relaxation, respectively. (5 marks)

  13. Outline the key divisions of the human nervous system. (3 marks)

  14. Explain why the spinal cord is essential for reflex actions. (3 marks

A LEVEL

  1. What is the main function of the human nervous system? (2 marks)

  2. How does the nervous system facilitate communication between different parts of the body? (2 marks)

  3. What is the approximate percentage of the body's weight that the brain represents? (1 mark)

  4. Name the two main divisions of the human nervous system. (2 marks)

  5. What are the components of the central nervous system (CNS)? (marks)

  6. Explain the role of the spinal cord in the central nervous system. (2 marks)

  7. What are the primary functions of the spinal cord? (2 marks) b. How does the spinal cord contribute to the coordination of voluntary movements? (2 marks)

  8. What happens to bodily functions if the spinal cord is damaged below a certain point? (3 marks)

  9. Name the four main areas of the brain. (2 marks)

  10. Provide an example of a function associated with each of the four main areas of the brain. (4 marks) c. How do the two cerebral hemispheres communicate with each other? (2 marks)

  11. What does the peripheral nervous system (PNS) consist of? (2 marks)

  12. Differentiate between the somatic nervous system and the autonomic nervous system. (3 marks) c. What is the primary function of sensory neurons in the somatic nervous system? (2 marks)

  13. Explain why the autonomic nervous system (ANS) is necessary for the body. (2 marks)

  14. Name the two divisions of the ANS and describe their typical effects on bodily functions. (4 marks)

  15. How do the sympathetic and parasympathetic divisions of the ANS differ regarding neurotransmitters and their effects? (3 marks)

  16. Describe the primary functions of the sympathetic nervous system (SNS). (2 marks)

  17. How does the SNS prepare the body to respond to emergencies? (3 marks) c. Explain the role of the parasympathetic nervous system (PNS) in relaxing the body. (3 mark.