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ANS221 Animal Structure and Function > Lecture 2 - Circulatory 2 > Flashcards

Lecture 2 - Circulatory 2 Flashcards

1
Q

Describe the origin of the heartbeat and the nervous control of the heart rate

A
  • Is initiated by the sinoarterial (SA) node
  • SA node pacemaker cells generate an electrical impulse (action potential)
  • Spreads across atria causing contraction
  • Pauses at AV node before spreading down conducting fibres to ventricles causing contraction
  • HR modified by autonomic nerves and hormones
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2
Q

Describe the origin of the heartbeat and the nervous control of the heart rate
- SNS

A

• SNS – somatic nervous system

  • Fight or flight
  • EEE (excitement, exercise and emergency)
  • Increase HR
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3
Q

Describe the origin of the heartbeat and the nervous control of the heart rate
- PNS

A

• PNS – parasympathetic nervous system

  • Rest or digest
  • DDD (digestion, defecation and diuresis)
  • Decreased HR
  • Diuresis = increased or excessive production of urine
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4
Q

Have an understanding of the normal heart rate of domestic animals and normal variations in heart rate

A 
Species	Age	      HR (beats/min)
Cattle	Adult	60-70
	         Calf	100-140
Sheep	Adult	70-80
	         Lamb	120-160
Goat	Adult	70-80
	          Kid	        120-160
Horse	Adult	28-44
	         Foal	60-80

Pig Adult 60-80
Dog Adult 70-120
Chicken Adult 200-400

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5
Q

Define tachycardia and bradycardia and list some common causes of each
• Tachycardia

A
  • Abnormally elevated resting HR

- Causes can include: stress, heat, fever, drugs and many formal of heart and vascular disease

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6
Q

Define tachycardia and bradycardia and list some common causes of each
• Bradycardia

A
  • Abnormally low resting HR
  • Less common than tachycardia
  • Causes can include: electrolyte imbalance, drugs and some heart disease
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7
Q

List the major components of blood and describe their major functions
• Transportation

A 
•	Transportation
-	Gases (O2 and CO2)
-	Nutrients and wastes
-	Hormones
•	Osmotic pressure 
-	H2O
•	Onconic pressure
-	Proteins
•	Heat
•	Immune cells and antibodies
•	Haemostasis
-	Platelets and clotting factors
•	Buffers
-	Regulate pH
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8
Q

List the major components of blood and describe their major functions
• Plasma

A

• Plasma = 55 – 70% of total blood volume
- Water 92%
- Proteins 7%
- Other 1%
• Plasma proteins generate colloid osmotic (onconic) pressure, important in balancing fluid movement in & out of capillaries

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9
Q

List the major components of blood and describe their major functions
• pH

A

Maintains pH, specific functions (lipoproteins), immunity (immunoglobins/antibodies), coagulation (clotting)

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10
Q

List the major components of blood and describe their major functions
• Red Blood Cells

A 
•	Cells = 30 – 45% of blood volume
-	RBC
-	WBC
-	Platelets
•	RBC >90% of all blood cells, required for O2 transport, contains haemoglobin (readily binds to O2), biconcave disk for gas diffusion, mature cells have no nucleus
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11
Q

List the major components of blood and describe their major functions
• White Blood Cells

A

• WBC (leukocytes) body defence against pathogens (bacteria, parasites and viruses)

  • Granulocytes – neutrophils, eosinophil’s and basophils
  • Monocytes
  • Lymphocytes
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12
Q

List the major components of blood and describe their major functions
• Platelets

A

• Platelets (thrombocytes)

  • Small cytoplasmic fragments, prevents blood loss (haemostasis)
  • Binds damaged cells, swells, stick together = platelet plug
  • Platelet plug is reinforced by polymerized proteins (coagulation factors) to form final blood clot
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13
Q

Be able to calculate packed cell volume (PCV)

A
  • RBC/total volume x 100% = PCV

* % Of RBC in blood

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14
Q

Describe what happens to packed cell volume and protein when hydration changes

A

• When dehydration occurs, normal plasma volume decreased, and protein concentration increased. RBC concentration is increased.

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15
Q
  1. Describe the five types of blood vessels, including how their function relates to their structure.
    • Arteries and arterioles
A
  • Takes blood away from the heart
    • Arteries - large branching vessels, thick walled, muscular and highly elastic, pressure reservoirs, recoil of elastic walls during diastole ensures continuous blood flow, important to maintain pressure during diastole
    • Arterioles – small branching vessels, carries blood away from heart to capillaries, very little elastic tissue but not a lot of smooth muscle, high resistance, muscle permits change in diameter to alter resistance and blood flow (vasoconstriction/dilation). Important to maintain arterial BP and flow through organs.
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16
Q
  1. Describe the five types of blood vessels, including how their function relates to their structure.
    • Venules and veins
A
  • Takes blood back to the heart
    • Venules – capillaries come together to form venules, venules contain little or no smooth muscle, carry blood to veins (to heart), some exchange can occur here
    • Veins – approx. same size as arteries but thinner walls, little or no elastic tissue, thin muscle layer, expand easily and act as a site for blood storage, 60% of blood volume is in the systemic veins, vasoconstriction pushes stored blood back to heart, pressure in veins low
    • Blood flow maintained by
  • Low resistance
  • One-way valves
  • Skeletal muscle pumps
17
Q
  1. Describe the five types of blood vessels, including how their function relates to their structure.
    • Capillaries
A
  • Connect arterial and venous sides
    • Capillaries – smallest vessels in the body, primary site of gas, nutrient, and waste exchange, most cells are 1mm of a capillary, thin walled and porous, don’t exist on its own but in capillary beds or networks, extensive branching increases surface area
    • Regulated by:
  • Pre-capillary sphincters: smooth muscle surrounding capillaries at atriole end
  • Metarterioles: a shunt between arteriole and venule
    • Not just passive pipes – they have difference structures and functional roles
18
Q

Describe the two factors that determine blood flow

- Pressure Gradient

A

• Pressure gradient (ΔP) and resistance to flow (R)
• Pressure gradient
- Blood flows from high pressure in arteries to low pressure in the veins
- Blood is under pressure from contraction of the heart
• Resistance
- Pressure falls along a vascular circuit (resistance)

19
Q

Describe the two factors that determine blood flow

- Resistance

A

• Pressure gradient (ΔP) and resistance to flow (R)
• Resistance
- Pressure falls along a vascular circuit (resistance)

20
Q

List the three features which influence resistance to flow in a vessel

A
  • Radius of vessel
  • Length of vessel
  • Viscosity of fluid
  • As radius increases, resistance decreases = flow rate increases
21
Q

Describe the role of vasodilation and vasoconstriction in regulating blood flow, and list the factors that influence these processes
- Vasoconstriction

A

• Vasoconstriction leads to increased TPR (total peripheral resistance) and decreased flow
- Increased SNS input
- Increased adrenaline in blood
- Local factors reduced metabolism in tissues (low CO2)
- Medications
• Vasodilation leads to decreased TPR and increased flow
- Decreased SNS input
- Decreased adrenalin in blood
- Local factors as increased metabolic activity (increased CO2)
- Medications

22
Q

Describe the role of vasodilation and vasoconstriction in regulating blood flow, and list the factors that influence these processes
- Vasodilation

A

• Vasodilation leads to decreased TPR and increased flow

  • Decreased SNS input
  • Decreased adrenalin in blood
  • Local factors as increased metabolic activity (increased CO2)
  • Medications
23
Q

Define the cardiac output, stroke volume and heart rate and give the relationship between these variables

A
  • Cardiac output (CO): the amount of blood pumped out of the heart each minute (CO = SV x HR)
  • Stroke volume (SV): the amount of blood pumped out of the ventricle each ‘stroke’ (L/beat)
  • Heart rate (HR): represents the number of beats per minute
  • Increased cardiac output = increased stroke volume or HR (or both)
24
Q

List the factors that affect heart rate and stroke volume

• Heart Rate

A
  • HR increased by SNS and circulating adrenalin
  • HR decreased by PNS
  • Changes in HR are seen in age, activity, fitness, fear, anxiety, excitement, response to blood volume drop/pressure, disease status
25
Q
  1. List the factors that affect heart rate and stroke volume
    • Stroke Volume
A

• SV by strength of heart contraction – SNS increases
• SV venous return (volume of blood)
- Blood volume (preload)
- Veinoconstriction by SNS
- Respiratory pump
• SV afterload
- Pressure of blood in aorta opposes ejection of blood from ventricle and reduces stoke volume

26
Q

Define systolic, diastolic, pulse and mean arterial blood pressure

A
  • Systolic BP (SBP): maximum pressure in arteries – during systole
  • Diastolic BP (DBP): minimum pressure in arteries – during diastole
  • Mean arterial pressure (MAP): average pressure in arteries
  • Pulse Pressure (PP): PP = SBP - DBP
27
Q

Describe the relationship between MAP, CO, and TPR

A
  • MAP: Mean arterial pressure
  • CO: cardiac output
  • TPR: total peripheral resistance
  • Long term regulation by regulating blood volume (kidneys & hormones)
28
Q

Explain how arterial BP is regulated in the short-term

A
  • Changes in SNS and PNS to increase/decrease MAP

* Changes in MAP detected by baroreceptors (stretch receptors) in major arteries

29
Q

Explain how arterial BP is regulated in the short-term

- If MAP Fails

A

• If MAP falls, baroreceptor reflex leads to

  • Increase HR
  • Increase strength of ventricular contraction
  • Increase vasoconstriction (arterioles)
  • Increase Veinoconstriction (veins)

ANS221 Animal Structure and Function (7 decks)

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