Question

5.

Activation of the sympathetic division of the autonomic nervous system produces _____ in heart rate, and activation of the parasympathetic division produces _____.

	a.	decreases, additional decreases in heart rate
	b.	increases, additional increases in heart rate
	c.	increases, decreases in heart rate
	d.	decreases, increases in blood pressure

Answer 1

Answer is option := C

PERIPHERAL NERVOUS SYSTEM

• Peripheral nervous system is the communication network between central nervous system and human body.
• It is divided in to somatic nervous system and autonomic nervous system.
• The somatic nervous system coordinates the body movements and receives external stimulus .
• The autonomic nervous system regulates the function of internal viscera,whole blood vessels,skin and glands.It is divided in to sympathetic and parasympathetic nervous systems.
• Sympathetic nervous system helps to cope up with stress full situations(Fight or flight response) and its activation results in elevation of heart rate and blood pressure where as parasympathetic division maintains the normal digestive and eliminatory processes and reduces the heart rate through dilating the blood vessels.

EFFECTS OF AUTONOMIC STIMULATION ON CARDIO VASCULAR SYSTEM

SYMPATHETIC STIMULATION

• It accelerates the firing of sinoatrial node in the heart and thus increases the rate and force of heart beat .
• By dilating the coronary arteries, it elevates the amount of blood to cardiac muscles.
• It also dilates the blood vessels supplying the skeletal muscles ,increases the supply of oxygen and other nutrients and removes metabolic waste products and thus increases the capacity of muscles.
• It even raises the peripheral resistance and blood pressure ,by constricting small arteries and arterioles in the skin.Through this the blood supply to highly active tissues such as heart,muscle and brain increases.
• It constrict the blood vessels in the secretory glands of digestive system.It accelerates the blood coagulation because of vasoconstriction.

Stimulation of sympathetic nervous system results in 3 effects on heart

• Positive chronotropic effect- Increase in heart rate
• Positive inotropic effect- increases the myocardial contractility
• Positive dromotrophic effect- Accelerates the electrical conductivity of heart

PARASYMPATHETIC STIMULATION

• It decreases the rate and force of heart rate.
• It constrict the coronary arteries by reducing the blood supply to the cardiac muscles.

Stimulation of parasympathetic nervous system results in 3 effects on heart

• Negative chronotropic effect- Decrease in heart rate
• Negative inotropic effect- Decreases the myocardial contractility
• Negative dromotrophic effect-Decreases the conduction velocity of heart