The Autonomic nervous system

Aims: The aim of this session is to provide you with a short talk about the Autonomic Nervous System Objective: By the end of this session, students should have a better understanding of the Autonomic nervous system. By the end of this session, students will feel more confident about their knowledge of the Autonomic Nervous System.

The Autonomic Nervous System The Autonomic Nervous System maintains constant conditions within the Body, a process known as HOMEOSTASIS. Most of this activity is independent (AUTONOMIC) of the conscious mind.

Autonomic Nervous System Responsible for control of involuntary or visceral bodily functions. Cardiovascular Respiration Digestive Urinary Reproductive functions Key role in body’s response to stress

The Autonomic Nervous System Is responsible for: Making sure that all the automatic things your body needs to do to keep you going, like breathing, digesting , sweating , shivering etc continue working smoothly without you having to think about them. How hard would it be to have to keep thinking ‘breathe in, breathe out’ or ‘start digesting the food stomach’

The Autonomic nervous system (ANS) directs all of the activities of the body that occur without a person’s conscious control, such as breathing and digestion

The Autonomic Nervous System is divided into two parts: SYMPATHETIC : Which is most active during times of stress PARASYMPATHETIC : Which controls maintenance activities and helps conserve the body’s energy.

The sympathetic division is considered the ‘fight or flight ’, fear system. The parasympathetic is connected to the ‘relaxation response’. Much of the interaction between body and mind takes place through the ANS activity. The concept of yin and yang are reflected in the ANS, with the parasympathetic function relating to the yin and the sympathetic function relating to the yang.

Sympathetic Nervous System The sympathetic system prepares the body for emergency actions by reducing non-essential activities such as digestion. It prepares the body for sudden stress, like if you see a robbery taking place. When something frightening happens, the sympathetic nervous system makes the heart beat faster, so that it sends blood more quickly to different parts that might need it. It also causes the adrenal glands at the top of the kidneys to release adrenaline, a hormone that helps give extra power to the muscles for a quick get away. This process is known as the body’s ‘fight or flight’ response.

Fight or flight This causes the heart to beat more quickly and Strongly, increases blood supply to the muscles, raises blood pressure, dilates the bronchi and increases the breathing rate, raises the blood sugar level for increased energy, speeds up mental activity, increases tension in the muscles, dilates pupils and increases sweating. Non-emergency functions, such as digestion are lessened or suspended.

Parasympathetic nervous system This does the exact opposite: it prepares the body for rest. It also helps the digestive tract move along so our bodies can efficiently take in nutrients from the food we eat. After ‘fight or flight’ when we have realised we are now safe, this part of the nervous system kicks in. The heart rate and blood pressure now goes down and the breathing normalises, it stimulates the production of digestive enzymes. Because we feel safe, all our chemical and hormonal secretions can function optimally again keeping us in balance and harmony. The parasympathetic division functions with actions that do not require immediate reaction.( rest and digest)

Comparison of the Sympathetic and Parasympathetic Nervous System

stress When a person perceives stress ( stimulus over the individuals threshold - and the threshold can vary enormously), including feelings , thoughts, fear , noise, light, drugs, chemicals- caffeine. Activity becomes centred in the sympathetic nervous system which prepares the body using the fight or flight reaction. This is a sense of physical, mental and chemical reactions that are triggered if the person feels endangered or threatened.

The standard physiological model of the Autonomic nervous system is of reciprocal tension – with the two parts keeping each mode in check – when the sympathetic goes up the parasympathetic goes down, and vice versa. A good example of optimal autonomic balance can be seen in cats who respond alertly to certain sounds and movement , but as soon as the situation is assessed as safe, return immediately to a relaxed state.

The Sympathetic The sympathetic Nervous System begins in the spinal cord, where the neurons exit between the level T1 and L2.Because of the location its often referred to as the thoracolumbar division.

Ganglia- a mass of nerve cells serving as a centre from which nerve impulses are transmitted The sympathetic nerve signals are relayed from the sympathetic ganglia which form a chain along either side of the spine. Stimulation of these nerves leads to an increase in heart and breathing rates, of supply to muscles, and the dilation of the pupils of the eyes. Meanwhile, salivation, urine production, and digestive activity is reduced.

The Parasympathetic The preganglionic cell bodies of the parasympathetic system are located in the brain stem and sacral portion of the spinal cord.

T he Parasympathetic system is consistently active at low levels, but levels of activity increase when it is necessary to bring the body back to a balanced state of elevated Sympathetic activity. The primary parasympathetic nerve is the vagus nerve, also known as cranial nerve X. When active the parasympathetic system slows down the heart rate, dilates blood vesseles, activates digestion and stores energy. The ganglia of the parasympathetic Autonomic system are inside organs. Only skin and blood vessels receive nerve messages from all positions on the cord. The parasympathetic system is referred to as the craniosacral division because of the location of its nerves

Phew, The End!

By Alys Glover