Vasoconstriction function
Vasoconstriction function: Vasoconstriction is one type of condition where the space or volume inside the afflicted blood vessels is decreased. Flow of blood is lowered when volume of blood vessel is contracted. At the very same period, resistance of flow of blood or force is elevated. Blood pressure rises because of this (bbc.uk 2021).
Vasodilation function: Vasodilation is the method of in elevating blood circulation to the body’s tissues. Cells can produce endogenous vasodilators in reaction to a need for oxygen or nutrients. As an outcome, vascular resistance is decreased as well as capillary perfusion is increased (bbc.uk 2021).
Vessel diameter contraction: The autonomic nervous system (ANS), which is made up of two main branches, parasympathetic and sympathetic, is responsible for controlling vascular wall contractility as well as tension.
Smooth muscles and Elastin: The tunica media surround the tunica intima and is composed of smooth muscle cells, flexible as well as connective tissues, which are organized in a circular pattern all around vessel. This layer is largely thicker in arteries, than that in veins. An endothelium with flattened endothelial cells lines the tunica intima. The tunica media, which is wedged between the IEL and the EEL, is largely a smooth muscle layer with certain elastin and collagen.
The skeletal-muscle pump’s action assists in the flow of blood to the heart. When muscles contract, they compress the veins that run through them. Blood is driven through the valves while veins are squeezed, and the valves shut to restrict return.
Key feature 1: The first structural feature of vein is that: Vein has thin walls and have less muscular tissues than the artery.
Key feature 2: The lumen is wide in vein where the lumen is narrow in artery (bbc.uk 2021).
The structural and functional differences between veins, arteries and capillaries are:
|
|
Arteries |
Veins |
Capillaries |
|
Pressure of blood flow |
High |
Low |
Low |
|
Thickness of Wall |
Thick |
Thin |
Very thin. |
|
Lumen Diameter |
Narrow |
Wide |
Extremely narrow |
|
Wall Layers |
Tunica Adventitia Tunica media Tunica intima |
Tunica Adventitia Tunica media Tunica intima |
Tunica intima |
|
Muscle and fibers |
Large amount |
Small amount |
Absent |
|
Valves |
No |
Yes |
No |
|
Function |
Send blood to the tissues from heart |
Carry blood to the heart from body tissues |
Material exchange of tissues. |
Baroreceptors are type of mechanoreceptors present in blood arteries around the heart that sense the amount of stretching on vascular walls as well as send stimulus to the brain about blood pressure and volume. With the elevation of blood volume, vessels expand and baroreceptor firing rates elevate (Armstrong, Kerndt and Moore 2021). When arterial pressure rises, the baroreceptors are engaged, expanding the blood vessel walls. These baroreceptors send information to the autonomic nervous system. The ANS subsequently lowers the heart rate by using the efferent parasympathetic fibres (vagus nerve). This aids in the reduction of blood pressure.
12-A (Fill in the blanks)
- Increases,
- Increases
- decrease
12- B
Conduction Pathway:
The cardiac conduction network is a system of specialized cardiac muscle cells that initiates and transmits the electric signals that cause each cardiac cycle’s synchronized contractions (medlineplus.gov 2021).
Functions of Sinoatrial (SA) and Atrioventricular (AV) node
- An electrical impulse is transmitted by the sinoatrial node (SA node). The atria (upper chamber of heart) then contract.
- An impulse is transferred into the ventricular by the Atrioventricular (AV) node. The bottom chambers of the heart (ventricles) then contract or pump blood (uofmhealth.org 2021).
Bundle of his:
The His bundle conducts signals from the atrioventricular node, which is positioned at the anterior-inferior region of the interatrial septum, to the heart’s ventricles, and is a crucial portion of the heart’s electrical conduction system (medlineplus.gov 2021).
References
Armstrong, M., Kerndt, C.C. and Moore, R.A., 2021. Physiology, baroreceptors. StatPearls [Internet].
BBC Bitesize, 2022. Structure and function of blood vessels – Structure and function of arteries, capillaries and veins – Higher Human Biology Revision – BBC Bitesize. [online] BBC Bitesize. Available at: <https://www.bbc.co.uk/bitesize/guides/zvjkbdm/revision/1> [Accessed 30 January 2022].
BBC Bitesize, 2022. Vasoconstriction, vasodilation, shivering and sweating – Homeostasis – WJEC – GCSE Biology (Single Science) Revision – WJEC – BBC Bitesize. [online] BBC Bitesize. Available at: <https://www.bbc.co.uk/bitesize/guides/zqgfv4j/revision/4> [Accessed 30 January 2022].
Medlineplus.gov, 2022. Cardiac conduction system – Health Video: MedlinePlus Medical Encyclopedia. [online] Medlineplus.gov. Available at: <https://medlineplus.gov/ency/anatomyvideos/000021.htm> [Accessed 30 January 2022].
Uofmhealth.org, 2022. Electrical System of the Heart | Michigan Medicine. [online] Uofmhealth.org. Available at: <https://www.uofmhealth.org/health-library/te7147abc> [Accessed 30 January 2022].
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