The nervous system
Specification: The divisions of the nervous system: central and peripheral (somatic and autonomic).
The nervous system
The nervous system is divided into the two main components: 1) the central nervous system (CNS) and 2) the peripheral nervous system (PNS). The nervous system has the following structure:
The CNS – brain and spinal cord
The CNS consists of the brain and the spinal cord. The brain provides conscious awareness and is involved in all psychological processes. The brain consists of many regions, which are responsible for different functions.
For example, the brain consists of four main lobes: frontal lobe, parietal lobe, temporal lobe and occipital lobe.
The occipital lobe processes visual information; the temporal lobe processes auditory information; the parietal lobe integrates information from the different senses and therefore plays an important role in spatial navigation; the frontal lobe is associated with higher-order functions, including planning, abstract reasoning and logic.
The brain stem connects the brain and spinal cord and controls involuntary processes, including our heartbeat, breathing and consciousness.
The role of the spinal cord is to transfer messages to and from the brain, and the rest of the body. The spinal cord is also responsible for simple reflex actions that do not involve the brain, for example jumping out of your chair if you sit on a drawing pin.
The PNS – somatic and autonomic nervous systems
The role of the peripheral nervous system (PNS) is to relay messages (nerve impulses) from the CNS (brain and spinal cord) to the rest of the body. The PNS consists of two main components: 1) the somatic nervous system and 2) the autonomic nervous system.
The somatic nervous system facilitates communication between the CNS and the outside world. The somatic nervous system is made up of sensory receptors that carry information to the spinal cord and brain, and motor pathways that allow the brain to control movement. Therefore, the role of the somatic nervous system is to carry sensory information from the outside world to the brain and provide muscle responses via the motor pathways.
The autonomic nervous system plays an important role in homeostasis, which maintains internal processes like body temperature, heart rate and blood pressure. The autonomic nervous system only consists of motor pathways and has two components: 1) the sympathetic nervous system and 2) the parasympathetic nervous system.
The sympathetic nervous system is typically involved in responses that prepare the body for fight or flight. Impulses travel from the sympathetic nervous system to organs in the body to help us prepare for action when we are faced with a dangerous situation. For example, our heart rate, blood pressure and breathing rate increase, while less important functions like digestion, salivation and the desire to urinate are suppressed.
The role of the parasympathetic nervous system is to relax the body, and return us to our ‘normal’ resting state. Consequently, the parasympathetic nervous system slows down our heart rate and breathing rate, and reduces our blood pressure. Furthermore, any functions that were previously slowed down during a fight or flight reaction are started again (e.g. digestion).
Possible exam questions
Which of the following statements is false?
The autonomic nervous system:
A comprises of two subsystems;
B controls communication between the CNS and the environment;
C plays an important role in homeostasis;
D maintains internal processes like blood pressure. (1 mark)
Joline has just been to the cinema with her friend to watch a new horror movie. While she is walking home alone she believes that she can hear footsteps following her and starts to panic. Without thinking she starts sprinting and gets home as fast as she can. She bursts through the front door, heart pounding, dripping with sweat and shaking.
Outline the role of the autonomic nervous system and central nervous system, referring to Joline’s experience in your answer. (4 marks)
Outline the role of the central nervous system/somatic nervous system/autonomic nervous system. (4 marks each)
Outline two differences in the organisation/function of the somatic nervous system and autonomic nervous system. (4 marks)