Lab 10: Biofeedback

Autonomic Nervous System (ANS)

The ANS is a component of the peripheral nervous system (PNS) that regulates involuntary physiological processes including heart rate, blood pressure, respiration, and digestion to maintain homeostasis and also sexual function.

Sympathetic nervous system (SNS)

Fight or flight

Parasympathetic nervous system (PNS)

Rest and digest

What do both SNS and PNS contain that they have in common?

They both contain both afferent and efferent neurons that provide sensory and motor output, respectively to the CNS.

Lets focus first on the efferent pathways of both SNS and PNS. What is the series that these two systems contain?

The first neuron series being the preganglionic neuron (or fiber) with a cell body in the CNS and a postganglionic neuron with a cell body in the periphery that innervates target tissues. SNS pathways have short preganglionic neurons and long postganglionic neurons, while PNS pathways have long preganglionic neurons and short postganglionic neurons.

Enteric Nervous System (ENS) 

Regulates the majority of the digestive processes.

List the physiological changes of the body when the SNS is activated. PNS?

SNS (fight or flight) increases blood pressure and heart rate. The process of breaking down glycogen to glucose in the muscle (glycogenolysis) occurs. And gastrointestinal peristalsis stops. In PNS (rest and digest), heart rate and blood pressure decreases. GI peristalsis starts up again, etc.

Do SNS and PNS neurons innervate the same organs?

Yes, even though ther are fewer PNS neurons than SNS neurons in the body and have opposing effects on their functions, they are both necessary in order to detect and respond correctly to each situation.

How about the neurotransmitters? What patterns do we see?

The preganglionic neurons in both sympathetic and parasympathetic nervous systems use acetylcholine as their neurotransmitter (ACh). Postganglionic sympathetic neurons usually produce norepinephrine. The exception here is that the postsynaptic parasympathetic neurons use ACh. NE from postganglionic SNS neurons bind to alpha- and beta-adrenergic receptors. While ACh from somatic motor neurons bind to nicotinic receptors.

Why does the SNS enable and disable certain systems of the body in order to enter “fight or flight” mode? What are the results of a successful activation of the SNS.

The most noticable thing that happens to a person is that they inhale and exhale much more intensly than normal. Increasing the rate of oxygen intake consequently increases muscle contraction and this generates heat that is dissipated via sweating. The function of blood shifts from normally absorbing nutrient from the food in our stomach to delivering oxygen to the skeletal muscles. The formal list of all the things that happen when SNS is activated is as follows:

• Heart rate increases, and increased cardiac muscle contractility.

• Increased sweat gland activity.

• Constriction of arterioles in the abdominal organs (redirects blood flow to muscles).

• General vasoconstriction (explains increased blood pressure)

• Dilation of bronchioles in the lungs (increases airflow and oxygen uptake).

• Dilation of pupils and ciliary muscles in the eye (allows more light to enter into the eye and improves viewing things that are at a distance)

• Glycogen and lipid breakdown (energy reserves for muscles)

• Peristalsis slows down in the GI system.

• Increased water reabsorption in the kidney.

• Relaxes bladder walls whilst contracting the urinary sphincter to prevent urination.

• Releases epinephrine and noepinephrine by the adrenal medulla.

Does the body switch between PNS and SNS completely?

No, The SNS is always active even during non-stressful situations. SNS is vital in regulating blood flow and pressure, the airflow during the normal respiratory cycle, and immune function.

Now onto PNS, what bodily functions does it regulate? What happens during activation of the PNS?

It regulates digestion and urinary function to conserve the energy and use this energy later. The list of things that happen are as follows:

• Heart rate decreases.

• Dilation of arterioles in abdominal organs (capillaries can work as normal again by absorbing substances between the blood and tissues)

• Vasodilation across the whole body.

• Constricts bronchioles in the lungs (less oxygen is needed)

• Pupils and ciliary muscles constrict and contract respectivelly (allowing us to see things near to us with more clarity)

• Contraction of the bladder and the relaxation of the urinary sphincter.

• Smooth muscles relax in reproductive organs (promotes sexual arousal).

Which nerve controls most of the functions of the PNS?

Vagus nerve (cranial nerve X). It is the longest cranial nerve in the body and contains both afferent (sensory) and efferent components. The majority, however, are afferent neurons that do a plethora of transmittance of sensory information (e.g. info from the throat, taste, visceral sensation of the heart and abdominal organs to the CNS). These afferent neurons also provide information to the central nervous system from baroreceptors in the aorta and carotid arteries to the medulla (baroreceptor reflex) which maintains the blood pressure.

Can the major physiological functions described in this flascard set be influenced by things other than the ANS?

Yes, conscious thoughts, emotional state, and psychological stress can all affect these functions as well. This is why biofeedback therapy exists.

How does biofeedback therapy work in general? What can it accomplish?

Biofeedback is a technique that trains people to exert conscious control over involuntary processes via increasing their awareness of these processes by monitoring these techiques in real time. People were able to lower heart rate, blood pressure, control migraines, and tension headaches, treat chronic pain, and reduce stress levels using this technique. 

How will we be utilizing the biofeedback technique in this lab?

We will measure heart rate (via ECG) and electrodermal activity (EDA). The EDA measures electrical conductance of the skin, which is influenced by the activity of the sweat glands, which these glands are controlled by the SNS. Thus, high EDA activity is a way to measure high SNS activity. To contrast this, when we are less stressed, PNS should dominate, leading to low EDA readings. 

What other form of measurement does the EDA provide?

It also provides the measurement of heart rate variability (HRV). HRV is just measuring the changes that occur in the R-R interval (the time interval in between heartbeats). Changes in SNS and PNS stimulation is what affects HRV levels. High levels of HRV is indicative of people that have better health, resilience, emotional regulation, and lower stress levels. TLDR: The longer the interval between each heart beat is (PNS dominance) the higher the HRV, and vice versa (SNS dominance).

During part one of this lab, where does everything go?

The black electrodes of EDA should be plugged into CH1 and the leads for 3 electrodes for ECG are plugged into CH2 of the biopac unit.

What are some general prerequisites when choosing the subject for this lab?

Ideally, it should be someone who has not excersied within the last hour and have not consumed caffiene or other stimulants. The index and the middle fingers of their left hand have to be warm for the EDA to work. Lastly, apply the EDA and ECG electrodes at least 5 minutes before we begin recording.