Homeostasis

Question 1

What is a set point?

Answer 1

A value at which a variable must be maintained to maintain homeostasis

Question 2

What is the set point for temperature?

Answer 2

37 degrees

Question 3

What is the set point for pH?

Answer 3

7.4

Question 4

What is the set point for plasma glucose?

Answer 4

5.5mM

Question 5

What is the set point for blood pressure?

Answer 5

120/80mmHg

Question 6

What is the set point for plasma osmolality?

Answer 6

300osmoles/kg

Question 7

What are the set points for PO2 and PCO2?

Answer 7

PO2 = 100mmHg
PCO2 = 40mmHg

Question 8

What happens when a variable deviates from the set point?

Answer 8

There is an error signal that activates a homeostatic mechanism to apply compensation

Question 9

What is a closed loop system?

Answer 9

When the change from the set point causes an error signal which activates a homeostatic mechanism which applies compensation and makes the variable back to set point and the changing of the variable back to set point then causes a negative feedback mechanism on the error signal and homeostatic mechanism

Question 10

What part of the brain is known as the homeostatic centre?

Answer 10

The hypothalamus

Question 11

What 4 things does the hypothalamus control?

Answer 11

1. Body temperature
2. Plasma osmolality
3. Appetite/thirst
4. Hormone release

Question 12

How does the ANS control homeostasis?

Answer 12

Through autonomic reflexes and hormones

Question 13

What two hormones are involved in regulating plasma glucose levels?

Answer 13

Insulin and glucagon

Question 14

What happens when plasma glucose exceeds 5.5mM?

Answer 14

Increased insulin secretion leads to an increased uptake of glucose into the tissue particullary by the liver in order to lower it back down to 5.5mM

Question 15

What happens when plasma glucose drops below 5.5mM?

Answer 15

Increase glucagon secretion leads to an increased release of glucose from the tissues espiecally the liver to raise plasma glucose back to 5.5mM

Question 16

What is low plasma glucose called?

Answer 16

Hypoglycemia

Question 17

What is high plasma glucose called?

Answer 17

Hyperglycemia

Question 18

Where are insulin and glucagon secreted from?

Answer 18

The pancreas

Question 19

What is absent in people with type one diabetes?

Answer 19

No insulin

Question 20

What does the absense of insulin mean for people with type 1 diabetes?

Answer 20

Means insulin is not causing the uptake of glucose into the tissues so in the fasted state there is no glucose to be release by glucagon so they need an injection of insulin

Question 21

How many spinal segments of the spinal chord are there and what regions are they in?

Answer 21

8 Cerivial
12 Thoracic
5 Lumbar
5 Sacral
30 in total

Question 22

What are baroreceptors?

Answer 22

Arterial stretch receptors in the walls of blood vessels

Question 23

What do baroreceptor detected?

Answer 23

Changes in arterial blood pressure

Question 24

What happens if arterial blood pressure falls?

Answer 24

Inhibition of the parasympathetic nervous system to stop the vagus never from inhibiting the heart and activation of the sympathetic nervous system which accelerates the heart beat and also causes vasoconstriction in order to raise the blood pressure back to normal

Question 25

What happens if arterial blood pressure rises?

Answer 25

Inhibition of the sympathetic nervous system to stop it accerlating the heart and to stop vasocontriction leading to vasodilitation as well are activation of the parasympathetic nervous system leads to increased firing of the vagus nerve to cause slowing of the heart to lower BP back to normal

Question 26

What is slowing of the heart otherwise known as?

Answer 26

Bradycardia

Question 27

How do the baroreceptor/arterial stretch receptors detect changes in blood pressure?

Answer 27

If blood pressure falls then the walls of the blood vessels containing the baroreceptor are stretched less and if blood pressure rises they are stretched more

Question 28

What cranial nucleus does the vagus nerve arises from?

Answer 28

The 10th cranial nucleus

Question 29

What is released by the pre-ganglionic fibres of the parasympathetic nervous system?

Answer 29

Acetylcholine

Question 30

Is the preganglionic fibre in the parasympathic nervous system long or short?

Answer 30

Long

Question 31

What is released by the post ganglionic fibres in the PNS?

Answer 31

Acetylcholine, nitric oxide and VIP

Question 32

Is the postganglionc fibre of the parasympathic nervous system long or short?

Answer 32

Short

Question 33

Where do the preganglionic and postganglionc fibres of the PNS meet?

Answer 33

A ganglion

Question 34

What is a ganglion?

Answer 34

A collection of nerve cells

Question 35

What is the action of the vagus nerve in the PNS?

Answer 35

- Slow heart rate - Constrict bronchii - Increase secretions

Question 36

What are the actions of the pelvic nerve in the PNS?

Answer 36

- Spinchter relaxation | - Colon and urinary contraction

Question 37

What do the preganglionic fibres of the sympathetic nervous system release?

Answer 37

Acetylcholine

Question 38

Are the preganglionic fibres of the sympathetic nervous system long or short?

Answer 38

Short

Question 39

Where do the preganglion fibres and the postganglion fibres synapse in the sympathetic nervous system?

Answer 39

The paravertebral ganglion/sympathetic chain ganglion

Question 40

Do all the preanglionic fibres go on to synapse at the ganglia?

Answer 40

No some extended to the adrenal medulla where they innverate it to produce adrenaline and noradrenaline

Question 41

What is the effect of adrenaline on skeletal muscle vasculature?

Answer 41

Vasodilitation

Question 42

What is the effect of noradrenaline on smooth muscle vasculature?

Answer 42

Vasoconstriction

Question 43

What are the actions of the sympathetic nervous system?

Answer 43

1. Increase heart rate 2. Relax bronchial smooth muscle 3. Inhibit secretions 4. Inhibit bladder and colon contraction 5. Inhibit sphincter relaxation 6. Sweating