L19: Homeostasis

Question 1

What are the 3 components involved in homeostasis?

Answer 1

1. Receptor (e.g free nerve ending in the skin)
2. Integrator (e.g. the brain)
3. Effector (e.g. muscle or gland)

Question 2

Which are examples of physical insults?

A. Intense heat
B. Drop in glucose
C. Lack of oxygen
D. Stress from work

Answer 2

A. Intense heat; and,
C. Lack of oxygen

Changes to the external environment

Question 3

Does the nervous system play an important role in homeostasis?

Answer 3

Yes

Question 4

Does the endocrine system play an important role in homeostasis?

Answer 4

Yes

Question 5

What is the role of the sympathetic nervous system?

Answer 5

Fight or flight

Question 6

What is the role of the parasympathetic nervous system?

Answer 6

Rest and digest

Question 7

What is negative feedback?

Answer 7

A change occurs, the body tries to reverse its effects or stop it

Question 8

What is positive feedback?

Answer 8

A change occurs, the body tries to build on the change. E.g. clot formation, uterine contractions

Question 9

What is the afferent pathway?

Answer 9

Path from receptor to the control centre

Question 10

What is the efferent pathway?

Answer 10

Path from control centre to effector

Question 11

What generates blood pressure?

Answer 11

Contraction of the ventricles

Question 12

What determines BP?

Answer 12

Cardiac output, blood volume, and vascular resistance

Question 13

What inputs lead to increased venous return?

Answer 13

Increased blood volume, skeletal muscle pump, respiratory pump, venoconstriction

Question 14

What inputs lead to increased stroke volume?

Answer 14

Increased venous return, increased sympathetic impulses and hormones from adrenal medulla

Question 15

What inputs lead to increased heart rate?

Answer 15

Decreased parasympathetic impulses, increased sympathetic impulses and hormones from adrenal medulla

Question 16

What inputs lead to increased cardiac output?

Answer 16

1. Increased stroke volume (sympathetic impulses, adrenaline, venous return from venoconstriction, respiratory and skeletal muscle pump, and blood volume)
2. Increased heart rate (decreased parasympathetic impulses, increase sympathetic impulses, adrenaline)

Question 17

Which of the following lead to increased cardiac output?

A. Increase blood volume
B. Increased blood vessel length
C. Increased blood viscosity
D. Venoconstriction
E. Adrenaline
F. Decreased parasympathetic impulse
G. Increased stroke volume

Answer 17

A. Increase blood volume

D. Venoconstriction

E. Adrenaline

F. Decreased parasympathetic impulse

G. Increased stroke volume

Question 18

What factors increase systemic vascular resistance?

Answer 18

1. Increased number of red blood cells (increases blood viscosity)
2. Increased body size (increases total blood vessel length)
3. Decreased blood vessel radius (vasoconstriction)

Question 19

Increasing cardiac output and systemic vascular resistance may lead to what problem?

Answer 19

Hypertension

Question 20

What effect does the parasympathetic system have on the heart?

Answer 20

Makes it beat at a slower rate

Question 21

What effect does the sympathetic system have on the heart?

Answer 21

Makes it beat faster (increases HR) and harder (increases SV)

Question 22

What effect does adrenaline have on the heart?

Answer 22

Makes it beat faster and harder

Question 23

What effect does polycythemia have on blood pressure?

Answer 23

(Polycythemia = increased number of RBC’s)

It increases the viscosity of the blood, which increases systemic vascular resistance, which increases BP.

Question 24

Fill in the gaps:

Homeostasis can control BP by adjusting heart __1__, stroke __2__, vascular __3__ and blood __4__.

Answer 24

1. rate
2. volume
3. resistance
4. volume

Question 25

Which control centre is chiefly responsible for blood pressure?

Answer 25

Cardiovascular centre in medulla oblongata

Question 26

What inputs send nerve impulses to the cardiovascular centre in the medulla oblongata?

Answer 26

Higher brain centres: - cerebral cortex - limbic system - hypothalamus Sensory receptors: - proprioceptors (movements) - chemoreceptors (blood chemistry) - baroreceptors (blood pressure)

Question 27

Why does the cerebral cortex send signals to the medulla oblongata?

Answer 27

Sometimes we are conscious of a situation in which we will need more blood pumped. This allows the CV centre to get ready before a physical stimulus

Question 28

What is the limbic system?

Answer 28

Control centre in the brain made up of the hypothalamus, amygdala, and hippocampus. Involved in emotion, arousal, and memory

Question 29

Why can a memory bring about a response from the cardiovascular centre?

Answer 29

The limbic system (responsible for some types of memory) is connected to the cardiovascular system

Question 30

What adjustments can be made by the cardiovascular centre in medulla oblongata in order to control BP?

Answer 30

Heart rate Stroke volume Vessel diameter Neural, hormonal and local negative feedback loops.

Question 31

The CV centre can change the frequency of nerve impulses fired along the cardiac accelerator nerves (sympathetic) to make homeostatic adjustments. What effects can this have?

Answer 31

Increased rate of spontaneous depolarisation in SA node (and AV node) increases heart rate. Increased contractility of atria and ventricles increases stroke volume. Decreased rate of spontaneous depolarisation in SA node (and AV node) decreases heart rate.

Question 32

Where can you find baroreceptors that help regulate blood pressure?

Answer 32

Carotid sinuses, aortic arch

Question 33

A drop in blood pressure leads the baroreceptors to signal the medulla oblongata (CV centre). What does the medulla do in response?

Answer 33

1. Medulla signals heart to increase rate, which increases cardiac output 2. Medulla signal blood vessels to constrict (vasoconstriction)

Question 34

Which of the following is/are inhibited in response to blood pressure drop? A. Vasomotor centres B. Cardioinhibitory centres C. Cardioacceleratory centres D. All of the above

Answer 34

B. Cardioinhibitory centres

Question 35

Which of the following is/are stimulated in response to blood pressure drop? A. Vasomotor centres B. Cardioinhibitory centres C. Cardioacceleratory centres D. All of the above

Answer 35

A. Vasomotor centres | C. Carioacceleratory centres

Question 36

Which of the following is/are stimulated in response to blood pressure rise? A. Vasomotor centres B. Cardioinhibitory centres C. Cardioacceleratory centres D. All of the above

Answer 36

B. Cardioinhibitory centres

Question 37

Which of the following is/are inhibited in response to blood pressure rise? A. Vasomotor centres B. Cardioinhibitory centres C. Cardioacceleratory centres D. All of the above

Answer 37

A. Vasomotor centres | C. Cardioinhibitory centres

Question 38

What is the effect of inhibiting the cardioacceleratory centres?

Answer 38

Decreased cardiac output, blood pressure reduced

Question 39

What is the effect of stimulating the cardioinhibitory centres?

Answer 39

Decreased cardiac output, blood pressure reduced

Question 40

What is the effect of inhibiting the vasomotor centres?

Answer 40

Vasodilation occurs, blood pressure reduced

Question 41

What is the effect of stimulating the carioacceleratory centres?

Answer 41

Increases cardiac output, blood pressure increased

Question 42

What is the effect of inhibiting the cardioinhibitory centres?

Answer 42

Increased cardiac output, blood pressure increased

Question 43

What is the effect of stimulating the vasomotor centres?

Answer 43

Vasoconstriction occurs, blood pressure increased

Question 44

Where can you find chemoreceptors involved in BP regulation?

Answer 44

Carotids, aortic arch, medulla oblongata

Question 45

What are the key things being monitored by the chemoreceptors in the carotid and aortic bodies?

Answer 45

CO2 levels, O2 levels, pH

Question 46

What changes, as detected by peripheral chemoreceptors, would lead to an increase in the action potential firing rate in afferent nerves?

Answer 46

Increased CO2, decreased O2, or decreased pH

Question 47

What makes central chemoreceptors (found in regions of the medulla) increase their firing rate?

Answer 47

Acidosis

Question 48

When afferent nerves from peripheral chemoreceptors activate the vasomotor centre in the medulla, what happens?

Answer 48

Increase in efferent activity to arteries and veins. Increased vasoconstriction, peripheral resistance and cardiac output. Cardiac centre in medulla is also activated, causing increase in heart rate and contractile force

Question 49

Is BP controlled by the nervous system or the endocrine system?

Answer 49

Both. Nervous system via baroreceptors and chemoreceptors Endorcine sytem via RAAS & ADH system

Question 50

True or false: BP is controlled by positive feedback

Answer 50

False. It is controlled by negative feedback

Question 51

Generation of nerve impulses is an example of what type of feedback system?

Answer 51

Positive

Question 52

Pyrexia is an example of what type of feedback system?

Answer 52

Positive

Question 53

Give an overview of the clotting cascade

Answer 53

Damage to vessel wall releases tissue factor, platelets activated, thrombin produced, thrombin triggers more of itself to be produced, fibrin formed, clots grows and grows until a separate system intervenes.

Question 54

What happens if a positive feedback system is allowed to continue without intervention.

Answer 54

The system will continue to run and run, likely causing life-threatening conditions

Question 55

What is the difference between signs and symptoms?

Answer 55

Signs are observable and objective, while symptoms are subjective and reported by the patient

Question 56

Myasthenia gravis is a neuromuscular disease that presents with fluctuating muscle weakness and fatigue. What causes the muscle weakness?

Answer 56

Antibodies block the Ach receptors at the postsynaptic junction, inhibiting the excitatory effects of Ach on the nicotinic receptors