The Nervous System and the Brain Information in this presentation is taken from UCCP content

The Nervous System Our nervous system has three primary functions: 1. to gather and process information 2. produce responses to stimuli 3. coordinate the working of different cells It is divided into two parts: central nervous system (brain and spinal cord) and the peripheral nervous system.

Peripheral Nervous System The peripheral nervous system consists of neurons that transmit messages to and from the central nervous system. There are two types of neurons in this system: sensory neurons and motor neurons. Sensory, or afferent, neurons receive the information from muscles and glands and transmit the message to the brain and spinal cord. Motor, or efferent, neurons receive messages from the brain and spinal cord and transmit the information to muscles and glands. An easy way to remember what afferent and efferent neurons do is to remember the mnemonic, SAME. Sensory neurons (S) are Afferent neurons (A); Motor neurons are Efferent neurons (E).

Peripheral Nervous System There are two divisions of the peripheral nervous system: the somatic nervous system and the autonomic nervous system. The somatic nervous system connects the CNS to sensory receptors and muscles. Neurons in the somatic nervous system transmit messages about sights, sounds, smell, temperature, and body position to the CNS. It also transmits information from the brain to produce purposeful motor movements. The autonomic nervous system is “automatic”. It controls and regulates the glands and muscle of internal organs. For example, it controls activities such as heart rate, respiration (breathing), digestion, and pupil dilation. These activities occur automatically.

Autonomic Nervous System There are two branches of the autonomic nervous system: sympathetic and parasympathetic. The sympathetic nervous system is most active during processes that involve spending the body’s energy from stored reserves. It prepares the body to respond in times of danger or high emotion. Basically, it is arousing the body to take action. (example: if you see a mean dog running towards you, your body will prepare you to expend your energy and RUN!) The parasympathetic nervous system is most active during processes that replenish reserves of energy. It quiets the body and lowers its level of arousal. It is most active after high emotional states. It works to keep your heart rate and breathing at moderate levels.

The Nervous System The somatic and autonomic nervous systems work together to coordinate the inner world of the body with what is going on in the outside world. For example, if a large dog growls and lunges at you, your autonomic nervous system (sympathetic) increases your blood pressure and heart rate and prepares you to react. At the same time, the somatic nervous system is sending messages to your leg muscles allowing you to run. Sometimes people’s sympathetic nervous system overreacts. In the absence of external threats, their bodies still respond as if they were faced with danger, such as in anxiety or panic attacks.

The Central Nervous System The central nervous system consists of the brain and spinal cord. Its primary functions are to: 1) receive, process, interpret and store sensory input and 2) initiate motor outputs

The Central Nervous System The spinal cord is like an information highway. It is a column of nerves that transmits messages (1) from sensory receptors to the brain and (2) from the brain to muscles and glands. The most basic pattern of neural responses, however, does not even include the brain. Spinal reflexes are unlearned, automatic responses to stimuli that typically include only two neurons, a sensory neuron and a motor neuron. Sometimes interneurons will transmit the neural impulse from the sensory neuron through the spinal cord to the motor neuron.

The Central Nervous System The pain reflex illustrates this neural pathway. Imagine if your right hand touches the burner on the stove. The sensory neurons in your hand detects the pain and instantly fires off a message to your spinal cord. When the message reaches your spinal cord it connects with an interneuron that in turn activates a motor neuron. The motor neuron sends a message to cells in your arm muscles that are capable of muscle movement. Muscle cells in your right arm contract, causing you to lift your right hand off the stove. If this happened, would it require any brain activity or thinking on your part? However, the spinal cord will also send a message to the brain notifying it about what you have done. After you withdraw your hand, you will most likely feel the pain and shout, “Ouch!”

The Brain The brain consists of three major regions: 1) The hindbrain 2) The midbrain 3) The forebrain Our forebrain is most important in those aspects of life that are most relevant to psychology (e.g. perception, memory, thinking and social behavior).

The Hindbrain The hindbrain controls some basic functions such as breathing and heart rate. It is also important in attention, sleep, alertness, body movement, and balance. The primary structures of the hindbrain are the following: 1) The cerebellum coordinates motor behavior, muscle coordination, and balance. 2) The medulla regulates unconscious functions such as breathing and circulation. 3) The pons connects the brain stem to the cerebellum and is involved in sleep and arousal as well as transmits information about body movement. 4) The reticular formation controls arousal and attention.

The Midbrain The midbrain plays a role in vision, hearing, motor movements, attention, and sleep. For our purposes, the midbrain is a conduction and switch center that serves as a link between the hindbrain and the forebrain.

The Forebrain The primary structures of the forebrain are: 1) Thalamus – relay station that receives and relays sensory information to the appropriate area of the cerebral cortex (e.g. sensory info. from the eyes) 2) Hypothalamus – regulates autonomic nervous system, motivation and emotion. It also controls eating, drinking, sexual behaviors and aggression. 3) Limbic System – includes the amygdala, hippocampus and parts of the hypothalamus. The amygdala is involved in aggression and fear responses. The hippocampus is important in learning and memory.