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Biology (Semester 2) > L19: Homeostasis > Flashcards

L19: Homeostasis Flashcards

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1
Q

What are the 3 components involved in homeostasis?

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

Which are examples of physical insults?

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

A

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

Changes to the external environment

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3
Q

Does the nervous system play an important role in homeostasis?

A

Yes

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4
Q

Does the endocrine system play an important role in homeostasis?

A

Yes

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5
Q

What is the role of the sympathetic nervous system?

A

Fight or flight

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6
Q

What is the role of the parasympathetic nervous system?

A

Rest and digest

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7
Q

What is negative feedback?

A

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

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8
Q

What is positive feedback?

A

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

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9
Q

What is the afferent pathway?

A

Path from receptor to the control centre

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10
Q

What is the efferent pathway?

A

Path from control centre to effector

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11
Q

What generates blood pressure?

A

Contraction of the ventricles

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12
Q

What determines BP?

A

Cardiac output, blood volume, and vascular resistance

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13
Q

What inputs lead to increased venous return?

A

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

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14
Q

What inputs lead to increased stroke volume?

A

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

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15
Q

What inputs lead to increased heart rate?

A

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

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16
Q

What inputs lead to increased cardiac output?

A
  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)
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17
Q

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
A

A. Increase blood volume

D. Venoconstriction

E. Adrenaline

F. Decreased parasympathetic impulse

G. Increased stroke volume

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18
Q

What factors increase systemic vascular resistance?

A
  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)
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19
Q

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

A

Hypertension

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20
Q

What effect does the parasympathetic system have on the heart?

A

Makes it beat at a slower rate

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21
Q

What effect does the sympathetic system have on the heart?

A

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

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22
Q

What effect does adrenaline have on the heart?

A

Makes it beat faster and harder

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23
Q

What effect does polycythemia have on blood pressure?

A

(Polycythemia = increased number of RBC’s)

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

24
Q

Fill in the gaps:

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

A
  1. rate
  2. volume
  3. resistance
  4. volume
25
Q

Which control centre is chiefly responsible for blood pressure?

A

Cardiovascular centre in medulla oblongata

26
Q

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

A

Higher brain centres:

  • cerebral cortex
  • limbic system
  • hypothalamus

Sensory receptors:

  • proprioceptors (movements)
  • chemoreceptors (blood chemistry)
  • baroreceptors (blood pressure)
27
Q

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

A

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

28
Q

What is the limbic system?

A

Control centre in the brain made up of the hypothalamus, amygdala, and hippocampus.

Involved in emotion, arousal, and memory

29
Q

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

A

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

30
Q

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

A

Heart rate

Stroke volume

Vessel diameter

Neural, hormonal and local negative feedback loops.

31
Q

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?

A

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.

32
Q

Where can you find baroreceptors that help regulate blood pressure?

A

Carotid sinuses, aortic arch

33
Q

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

A
  1. Medulla signals heart to increase rate, which increases cardiac output
  2. Medulla signal blood vessels to constrict (vasoconstriction)
34
Q

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

A

B. Cardioinhibitory centres

35
Q

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

A

A. Vasomotor centres

C. Carioacceleratory centres

36
Q

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

A

B. Cardioinhibitory centres

37
Q

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

A

A. Vasomotor centres

C. Cardioinhibitory centres

38
Q

What is the effect of inhibiting the cardioacceleratory centres?

A

Decreased cardiac output, blood pressure reduced

39
Q

What is the effect of stimulating the cardioinhibitory centres?

A

Decreased cardiac output, blood pressure reduced

40
Q

What is the effect of inhibiting the vasomotor centres?

A

Vasodilation occurs, blood pressure reduced

41
Q

What is the effect of stimulating the carioacceleratory centres?

A

Increases cardiac output, blood pressure increased

42
Q

What is the effect of inhibiting the cardioinhibitory centres?

A

Increased cardiac output, blood pressure increased

43
Q

What is the effect of stimulating the vasomotor centres?

A

Vasoconstriction occurs, blood pressure increased

44
Q

Where can you find chemoreceptors involved in BP regulation?

A

Carotids, aortic arch, medulla oblongata

45
Q

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

A

CO2 levels, O2 levels, pH

46
Q

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

A

Increased CO2, decreased O2, or decreased pH

47
Q

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

A

Acidosis

48
Q

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

A

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

49
Q

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

A

Both.

Nervous system via baroreceptors and chemoreceptors

Endorcine sytem via RAAS & ADH system

50
Q

True or false: BP is controlled by positive feedback

A

False. It is controlled by negative feedback

51
Q

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

A

Positive

52
Q

Pyrexia is an example of what type of feedback system?

A

Positive

53
Q

Give an overview of the clotting cascade

A

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.

54
Q

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

A

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

55
Q

What is the difference between signs and symptoms?

A

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

56
Q

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

A

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

Biology (Semester 2) (11 decks)

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