Heat Stress Response Mechanisms

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Questions and Answers

List 2 mechanisms that can be activated during a response to heat stress

sweating (evaporative cooling)
Vasodilation (increased blood flow to the skin)

Which mechanisms of heat transport is most efficient?

Radiation
Conduction
Convection
evaporation/condesation Evaporation would be most efficient

List 3 mechanisms responsible for maintaining the resting potential

Sodium potassium pump
selective permeability
leak channels

Name the structures that produce cerebrospinal fluid in the brain

The choroid plexuses are the primary structures responsible for producing CSF in the brain, filtering plasma from blood and secreting it as CSF Signup and view all the answers

List 2 functions of cerebrospinal fluid

<ol> <li>Protection and Cushioning</li> <li>Nutrient delivery and waste removal</li> </ol> Signup and view all the answers

How is the sympathetic nervous system able to mount a coordinated response involving multiple body organisms/systems when activated during a response in stress?

<ol> <li>Divergence of neural pathways: a single preganglionic neuron in the SNS can synapse with multiple postganglionic neurons, which allows the signal to spread widely to different target organs</li> <li>Release of catecholamines: the SNS stimulates the adrenal medulla to release epinephrine and norepinephrine into the bloodstream</li> <li>Adrenergic receptors on target organs: different organs express alpha and beta-adrenergic receptors, this allows for vasodilation in skeletal muscles and vasoconstriction in the digestive tract</li> </ol> <ol start="4"> <li>Central control by the hypothalamus: integrates sensory inputs and coordinates the SNS activation to ensure accurate fight or flight response</li> </ol> Signup and view all the answers

What is the neurotransmitter used by the parasympathetic nervous system to control target organs?

Acetylcholine Signup and view all the answers

What is the neurotransmitter used by the somatic motor neuron to stimulate muscles to contract at the neuromuscular junction?

Acetylcholine which is then broken down by acetylcholinesterase in the synaptic cleft to ensure precise control of muscle activation and relaxation Signup and view all the answers

Why are contractile cells of the heart unable to generate another AP until the physical contraction is over and thus prevent a tetranic phase?

Due to the long absolute refractory period of cardiac muscle cells as well as the slow calcium influx, sustained contraction and the synchronization of electrical and mechanical activity Signup and view all the answers

Define the term afterload

Refers to the resistance or pressure the heart must overcome to eject blood during a contraction (systole) specifically it is the force that the left ventricle must work against to pump blood into the aorta and throughout the systemic circulation Signup and view all the answers

A severe blood loss following an injury, results in serious damage in blood pressure. This would trigger a reflex to restore normal blood flow a) where would the drop in blood pressure be detected in arterial systems? b) where would the information be integrated (location of the cardiovascular integration centres) c) what branch of the autonomic nervous system would be activated d) what would be the effect on the arterioles

a) baroreceptors located in the carotid sinus and the aortic arch detect the drop in arterial blood pressure b)Transmitted to the cardiovascular control center in the medulla oblongata of the brainstem c) The sympathetic nervous system (fight or flight) d) Vasoconstriction: the SNS causes arterioles to constrict, increasing vascular resistance and helping to elevate blood pressure Signup and view all the answers

During bulk flow movement of fluid in the capillaries: a) what are the two opposite forces (pressure) controlling filtration an reabsorption b) what would the effect of defective venous return be? like observed in cases of right heart failure

a) <ol> <li>hydrostatic pressure (this promotes filtration)</li> <li>colloid osmotic pressure (this promotes reabsorption) (Oncotic pressure OP) b)</li> <li>Increased capillary hydrostatic pressure</li> <li>edema formation</li> </ol> Signup and view all the answers

Study Notes

Heat Stress Response Mechanisms

Sweating: The body releases sweat, which evaporates and cools the skin.
Vasodilation: Blood vessels dilate, increasing blood flow to the skin to dissipate heat.

Mechanisms of Heat Transport

Conduction: Heat transfer through direct contact between objects or substances.

Resting Potential Maintenance

Sodium-Potassium Pump: Pumps 3 sodium ions out of the cell and 2 potassium ions into the cell, maintaining the concentration gradient.
Potassium Leak Channels: Allow potassium ions to leak out of the cell, contributing to the negative charge inside.
Negative Charge of Proteins: Large, negatively charged proteins inside the cell also contribute to the negative charge.

Cerebrospinal Fluid Production

Choroid Plexuses: Networks of capillaries located in the ventricles of the brain.

Cerebrospinal Fluid Functions

Protection: Cushions the brain and spinal cord.
Nutrient and Waste Transport: Delivers nutrients and removes waste products.

Coordinated Sympathetic Nerve Activation

The sympathetic nervous system uses norepinephrine as its primary neurotransmitter.
Norepinephrine acts on various organs and systems, triggering widespread responses including:
- Increased heart rate and contractility
- Vasoconstriction in most organs
- Dilation of bronchioles
- Increased sweating
- Pupil dilation

Parasympathetic Neurotransmitter

Acetylcholine: The parasympathetic nervous system uses acetylcholine to regulate target organs.

Somatic Motor Neuron Neurotransmitter

Acetylcholine: Somatic motor neurons release acetylcholine at the neuromuscular junction to stimulate muscle contraction.

Cardiac Contractile Cells and Refractory Period

The long refractory period in cardiac contractile cells is caused by the influx of calcium ions, which prolongs the depolarization phase.
This prevents tetanus and allows for efficient heart pumping.

Afterload

Afterload refers to the resistance the heart must overcome to eject blood into the aorta.

Blood Loss and Blood Pressure Regulation

a) Detection of Blood Pressure Drop: Baroreceptors in the carotid arteries and aortic arch detect the decrease in blood pressure.
b) Cardiovascular Integration Centres: The information is integrated in the medulla oblongata, specifically within the cardiovascular centers.
c) Autonomic Nervous System Activation: The sympathetic nervous system is activated.
d) Arteriole Effect: Sympathetic activation causes vasoconstriction of arterioles, increasing peripheral resistance and elevating blood pressure.

Bulk Flow Movement in Capillaries

a) Forces Controlling Filtration and Reabsorption: The two opposing forces are:
- Hydrostatic Pressure: Pressure exerted by the blood against the capillary wall.
- Osmotic Pressure: Pressure exerted by the concentration of solutes in the blood.
b) Effect of Defective Venous Return: Defective venous return, as seen in right heart failure, leads to reduced blood flow back to the heart. This increases capillary hydrostatic pressure, leading to edema (fluid accumulation) in the tissues.

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Description

This quiz explores the physiological mechanisms activated during heat stress responses. It challenges your understanding of how organisms adapt to increase their resilience against elevated temperatures.