Sympathetic Nervous System Flashcards
What is the function of the sympathetic nervous system?
Its responsible for flight or fight responses takes over body responses when in a stressful or dangerous situation. The sympathetic system enables the body to be prepared for fear, flight or fight response.
These include dilatation of blood vessels, increase in blood pressure, contract muscles, sweat secretions, contract cardiac muscle and dilate the bronchi
Sympathetic responses include an increase in heart rate, blood pressure and cardiac output
Diversion of blood flow from the skin and splanchnic vessels to those supplying skeletal muscle
Increased pupil size, bronchiolar dilation, contraction of sphincters and metabolic changes such as the mobilisation of fat and glycogen
What are the features of the sympathetic nervous system?
Outline the pathway of the sympathetic nervous system
There are different regions on the paravertebral ganglion chain that allow the preganglionic fibers to synapse with the postganglionic fibers and exit to effector organs:
Superior cervical ganglia
The fibers move up to the top of the chain and synapse with the postganglionic fibers. These innervate the eye and some glands and the heart
T5-T9
These don’t synapse in the paravertebral ganglia
The preganglionic fibers join to form the greater splanchnic nerve and the lesser splanchnic nerve. These then synapse at the celiac ganglion and the superior mesenteric ganglion. Innervation is to the stomach, small intestine adrenal glands in the celiac ganglia and large intestine in the superior mesenteric ganglia
T11-L2
They do not synapse in the chain
These fibers travel downwards and synapse at the inferior mesenteric ganglion. These innervate the colon, urinary bladder and vas deferens
How does the fight or flight response work?
When someone experiences a stressful event, the amygdala, an area of the brain that contributes to emotional processing, sends a distress signal to the hypothalamus. This area of the brain functions like a command center, communicating with the rest of the body through the nervous system so that the person has the energy to fight or flee
After the amygdala sends a distress signal, the hypothalamus activates the sympathetic nervous system by sending signals through the autonomic nerves to the adrenal glands. These glands respond by pumping the hormone epinephrine (also known as adrenaline) into the bloodstream. As epinephrine circulates through the body, it brings on a number of physiological changes. The heart beats faster than normal, pushing blood to the muscles, heart, and other vital organs. Pulse rate and blood pressure go up. The person undergoing these changes also starts to breathe more rapidly. Small airways in the lungs open wide. This way, the lungs can take in as much oxygen as possible with each breath. Extra oxygen is sent to the brain, increasing alertness. Sight, hearing, and other senses become sharper. Meanwhile, epinephrine triggers the release of blood sugar (glucose) and fats from temporary storage sites in the body. These nutrients flood into the bloodstream, supplying energy to all parts of the body
What are the neurotransmitters used in the sympathetic nervous system?
Neurotransmitters used by the sympathetic nervous system are acetylcholine, epinephrine and norepinephrine.
1. Acetylcholine: this is a neurotransmitter that plays a role in regulating heart rate, blood flow and digestion.
2. Epinephrine: also known as adrenaline, is both a hormone and a neurotransmitter. Released by the nerves in small amounts and plays a role in metabolism, excitement and panic.
3. Norepinephrine: also known as noradrenaline is also a hormone and a neurotransmitter made from nerve cells out of dopamine. norepinephrine increases your alertness and attention, constrict blood vessels to maintain blood pressure during stressful situations etc.
What are the problems associated with the sympathetic nervous system?
When the sympathetic nervous system is stimulated too often, it can lead to chronic stress which may raise blood pressure causing hypertension and increase risk of heart attack or strokes.
On the other hand, an under-functioning sympathetic nervous system can cause problems if you do find yourself in a life threatening situation.
Symptoms associated with autonomic (sympathetic) dysfunction include:
1. digestive problems
2. Dizziness or fainting
3. Blurry vision
Explain the correlation between hyperhidrosis and the sympathetic nervous system
Hyperhidrosis: This condition involves excessive sweating, which can be localized or generalized and is often due to overactivity of the sympathetic nerves that control sweat glands
Explain the correlation between pheochromocytoma and the sympathetic nervous system
Pheochromocytoma: This is a rare tumor of the adrenal gland that can cause excessive release of catecholamines (epinephrine and norepinephrine), leading to symptoms like hypertension, sweating, and palpitations
Explain the correlation between Postural Orthostatic Tachycardia Syndrome and the sympathetic nervous system
Postural Orthostatic Tachycardia Syndrome (POTS): This is characterized by an abnormal increase in heart rate when moving from lying down to standing up. Dysautonomia, including sympathetic dysfunction, is thought to play a role
