Anatomy Exam 3 Part 4

Four cranial nerves involved with the parasympathetic nervous system

1) Oculomotor nerve (CN III) 2) Facial nerve (CN VII) 3) Glossopharyngeal nerve (CN IX) 4) Vagus nerve (CN X)

Two kinds of sympathetic ganglia

1) Paravertebral ganglia - Paravertebral ganglia, also called sympathetic chain ganglia, are found in a vertical row on either side of the vertebral column. 2) Prevertebral ganglia - Prevertebral ganglia are found anterior to the vertebral column near the large arteries that supply the abdominal aorta.

differences between the somatic and visceral, or autonomic, motor divisions

1) Somatic neurons can only activate skeletal muscles. -> In contrast, neurons in the autonomic motor division can either activate or inhibit smooth muscle, cardiac muscle, or glands 2) - In the somatic nervous system, impulses are sent from the spinal cord to the skeletal muscle via the neuron of a single axon. - The autonomic nervous system uses two neurons 1) a preganglionic neuron and a 2) postganglionic neuron.

parasympathetic vs. sympathetic nervous system - main differences

1) The neurotransmitter released onto an effector is different between the sympathetic and parasympathetic nervous systems. -> The sympathetic nervous system uses norepinephrine, while the parasympathetic nervous system uses acetylcholine. ----------- 2) Soma location - The somas of sympathetic preganglionic neurons exist in the lateral horn of the thoracolumbar spinal cord. - The somas of parasympathetic preganglionic neurons exist in the brainstem or the sacral spinal cord. 3) The autonomic ganglia that connect sympathetic preganglionic and postganglionic neurons are located close to the spinal cord -> while the autonomic ganglia that connect parasympathetic preganglionic and postganglionic neurons are located farther away from the spinal cord, commonly in the organ that is innervated. -> Therefore, these are called terminal ganglia. --------------- 3) - In the sympathetic nervous system, the preganglionic axon is shorter than the postganglionic axon -Whereas in the parasympathetic nervous system, the preganglionic axon is much longer than the postganglionic axon.

sympathetic nervous system - main overview

Is responsible for the body's "fight-or-flight" function. This system is also sometimes called the thoracolumbar outflow because the somas of the sympathetic preganglionic neurons exist in the lateral horn of the thoracolumbar spinal cord (T1 to L2). Most sympathetic ganglia are located near the spinal cord rather than near effector organs. -> As a result, sympathetic circuits tend to have short preganglionic axons (which extend from the spinal cord to the ganglia) and long postganglionic axons (which extend from the ganglia to the effector organs).

Cranial nerves and taste sensation

Note that the three cranial nerves that give you taste sensation are three of the four cranial nerves with parasympathetic function. (Recall that the facial nerve provides taste sensation for the anterior 2/3 of the tongue, the glossopharyngeal nerve provides taste sensation for the posterior 1/3 of the tongue, and the vagus nerve provides taste sensation for the back of the throat. )

parasympathetic organs and terminal ganglia

Parasympathetic ganglia are located far away from the spinal cord, near their effector organs. -> For this reason, they are sometimes called terminal ganglia because they terminate near the walls of effector organs. -> This arrangement of ganglia so far away from the spinal cord means that parasympathetic circuits have long preganglionic axons (which extend from the central nervous system to the ganglia) and short postganglionic axons (which extend from the ganglia to the effector organs).

preganglionic and postganglionic neurons

Preganglionic neurons in the parasympathetic nervous system begin in the brainstem or the sacral region of the spinal cord. -> (Note that the soma for preganglionic neurons is always in the CNS, while the soma for postganglionic neurons is always in the PNS.) 1) The preganglionic neuron then releases acetylcholine into the synaptic cleft, activating a second neuron in the peripheral nervous system called the postganglionic neuron. -> (This neuron has a cell body in a ganglion.) 2) The nervous signal is then sent to effector muscles or glands, where a second transmitter—either acetylcholine or norepinephrine—activates a response. -> (Acetylcholine is used by the parasympathetic nervous system, and norepinephrine is used by the sympathetic nervous system.)

Epinephrine and norepinephrine

Similar hormones involved in the sympathetic nervous system's response to stress. -> These hormones are sometimes called adrenaline and noradrenaline. -> If you see a bear in the woods, you will get an adrenaline rush, which leads to all of the characteristic sympathetic responses (increased heart rate, increased blood pressure, etc. ).

anaphylactic shocks.

Some individuals have severe allergic reactions called anaphylactic shocks. When an individual has an anaphylactic shock, his or her bronchioles constrict, leading to a lifethreatening shortage of air. Anaphylactic shock can be treated with a shot of epinephrine, which triggers a sympathetic response and causes dilation of the bronchioles.

adrenal medulla and sympathetic nervous system

The adrenal glands sit on top of the kidneys, and they contain an inside portion called the medulla and an outside portion called the cortex. The adrenal medulla contains specialized sympathetic ganglia (chromaffin cells) responsible for the production of epinephrine (adrenaline) and norepinephrine (noradrenaline). 1) A preganglionic neuron emerges from the ventral root of the spinal cord and goes to the adrenal medulla, where it synapses with specialized neurons that don't have processes (axons or dendrites). 2) Their sole function is to secrete epinephrine and norepinephrine into the bloodstream. In this sense, the adrenal medulla is essentially one large sympathetic ganglion that produces hormones. The difference between this circuit and the circuit made by a preganglionic and postganglionic axon its that the adrenal medulla dumps hormones into a blood vessel, which has an impact on an effector organ.

parasympathetic nervous system - Facial nerve (CN VII)

The facial nerve stimulates the flow of saliva by activating salivary glands below the tongue (the sublingual and submandibular salivary glands). -> It also stimulates the production of tears from the lacrimal gland at the top of the eyes.

parasympathetic vs. sympathetic nervous system

The functions of the sympathetic and parasympathetic nervous systems oppose one another. -> For the most part, activation of one of these systems inhibits the functioning of the other. 1) The skin is one major exception -> it is only innervated by the sympathetic nervous system. 2) The reproductive system is another exception because there are times that these two systems work together.

parasympathetic nervous system - Glossopharyngeal nerve (CN IX)

The glossopharyngeal nerve stimulates another salivary gland called the parotid gland.

Heartbeat and autonomic control

The heartbeat is under autonomic control. The heart is myogenic, meaning it can beat on its own, but the myogenic heartbeat is much faster than the heartbeat under autonomic regulation. ' -> If the heart were left to beat on its own, it would beat at about 110 beats per minute. A "normal" resting heartbeat in humans, on the other hand, is somewhere between 60 and 72 beats per minute.

parasympathetic nervous system - Oculomotor nerve (CN III)

The oculomotor nerve is involved in eye movement, eyeball regulation, and the constriction of the pupils. -> If you're in the woods and see a bear, your sympathetic nervous system will act to cause dilation of the pupils, which will increase the amount of light that enters your eye and increase your visual acuity.. You don't need this much light or visual acuity at rest, so your parasympathetic nervous system constricts the pupils and limits the amount of light that enters the eye.

parasympathetic nervous system - main overview

The parasympathetic nervous system is responsible for the body's "rest-and-digest" function. -> This system is also sometimes called the craniosacral outflow because the soma of the parasympathetic preganglionic neurons exist in the brainstem (cranium) or the sacral spinal cord. -> The following diagram shows each of the major components of the parasympathetic nervous system and some representative impacts on the body:

parasympathetic nervous system

The parasympathetic nervous system is responsible for the body's "rest-and-digest" response. -> When the body is at rest, the parasympathetic nervous system acts to conserve and restore body energy. It inhibits body functions that support physical activity and promotes such things as digestive and urinary function.

hypothalamus and sympathetic/parasympathetic nervous system

The sympathetic and parasympathetic systems are continually active; the relative expression of each of these systems depends on the extent to which the opposing system balances it out. The hypothalamus regulates the balance of sympathetic and parasympathetic activity, which is sometimes referred to as autonomic tone. 1) Heartbeat 2) Breathing

sympathetic nerves and cardiac accelerator

The sympathetic nerves that control the heart are called cardiac accelerator nerves because they make the heart beat faster and harder. They innervate three locations on the heart: 1) the sinoatrial (SA) node 2) the atrioventricular (AV) node 3) the cardiac myocytes themselves.

sympathetic nervous system

The sympathetic nervous system is responsible for the body's "fight-or-flight" response, which is activated by physical and emotional stress. -> In stressful situations, your body automatically stimulates body functions critical for survival and immediate physical activity and inhibits body functions that are not critical. So, for example, if you encounter a bear in the woods, your heart will pound, your respiratory rate will increase, your blood pressure will increase, and your pupils will dilate. -> Meanwhile, blood will be diverted away from your urinary and digestive systems because these systems are relatively unimportant in a time of short-term stress.

parasympathetic nervous system - Vagus nerve (CN X)

The vagus nerve is a major supplier of the visceral organs. It supplies 90% of the preganglionic parasympathetic fibers for the body. This nerve is purely parasympathetic; it has no sympathetic function. It can either activate or inhibit a visceral organ, depending on the appropriate response. -> For example, it activates the stomach and stimulates peristalsis, but it inhibits the heartbeat. This is consistent with the general parasympathetic, "rest-and-digest" response: if you are resting, you need to bring your heartbeat down and devote more energy and blood flow to digestion.

Autonomic nervous system

The visceral nervous system of the peripheral nervous system. The autonomic nervous system consists of motor neurons that innervate effectors, including smooth muscle, cardiac muscle, and glands. As we will discuss below, the motor division of the autonomic nervous system is further split into two divisions: 1) the sympathetic nervous system and the 2) parasympathetic nervous system. -> It functions in the autonomic activation or inhibition of body systems. The autonomic nervous system is purely a motor system; it is not a sensory system. -> Although we will primarily focus on the autonomic motor functions in this section, you should note that the general visceral sensory system works in tandem with the visceral motor system, providing continuous sensory input about the activities of the visceral organs.

Major function of autonomic nervous system

To maintain homeostasis, in terms of heart rate, breathing, blood glucose levels, and the like. -> It should, therefore, be unsurprising that the autonomic nervous system works in close coordination with the hypothalamus and the medulla.

EpiPen

When Dr. Ahlgren was young, her mom had an asthma attack triggered by glue that had been used to lay down carpet in her church. -> Her mom had to quickly dig through her purse to find an EpiPen (a type of portable epinephrine injector) so that she could quickly inject epinephrine into her system and dilate her bronchioles.

Breathing and Autonomic control

Your breathing is under autonomic control as well. The bronchioles are smooth muscle sphincters associated with the tubes leading in and out of your lungs. When they contract, these tubes get smaller and air flow is reduced. The sympathetic nervous system dilates your bronchioles, allowing you to get more air when you are undergoing a strenuous physical activity, such as running away from a bear. -> It does this by inhibiting contractions of the smooth muscle around the bronchioles. The parasympathetic nervous system causes the contraction of your bronchioles, somewhat restricting air flow.

vagus nerve and heartbeat in relation to sympathetic/parasympathetic nervous system

the parasympathetic nerve that controls the heartbeat. -> It slows the heart down and reduces the rate at which the heart pumps blood. So, suppose you have a heart rate of 72 beats per minute at rest, during a normal activity like talking. -> If you stop talking, freeze, and meditate, you might be able to bring your heart rate down to 60 beats per minute, tilting the balance toward the parasympathetic nervous system. -> If you start doing jumping jacks, you might reduce your parasympathetic function and speed up the heart. -> If you continue doing strenuous activities and bring your heart rate to about 110 beats per minute, your sympathetic nervous system will be heavily involved. -> This shows how the vagus nerve and the sympathetic cardiac accelerator nerves impact the intrinsic heart rate.