Homeostasis and control systems

Question 1

In our internal environment (in the body) are fluctuations in factors large or small?

Answer 1

small

Question 2

in the external environment (outside the body) are fluctuations in factors large or small?

Answer 2

large

Question 3

What’s the purpose of homeostasis- with reference to internal and external environments?

Answer 3

to stop the large fluctuations in the external environments from having a large effect on the internal environment

Question 4

define homeostasis..

Answer 4

the maintenance of a constant internal environment (around a threshold/set point)

Question 5

What does a negative feedback system aim to do?

Answer 5

maintains a controlled variable at a set point

Question 6

what 2 variables are required for negative feedback control?

Answer 6

• controlled variable

- set point

Question 7

in terms of negative feedback control, what’s the controlled variable?

Answer 7

aspect of internal environment e.g. temperature

Question 8

in terms of negative feedback control, what’s the set point?

Answer 8

the value at which the variable should be e.g. 37 degrees celsius

Question 9

In negative feedback, what happens once the set point has been reached?

Answer 9

the negative feedback cycle is halted

Question 10

describe the blood pressure and its negative feedback cycle

Answer 10

There’s a change in a variable e.g. reduction in BP due to a haemorrhage.
A sensor detects this change e.g. baroreceptors
The information travels along the afferent pathways to an intergrating centre e.g. medulla oblongata of the brain
The intergrating centre sends information along the efferent pathways to an effector e.g. heart blood vessles
the effector changes in order to return the variable to within its threshold e.g. increased cardiac output and vasocontriction
once the threshold has been returned to, the negative feedback cycle stops

Question 11

How does positive feedback work?

Answer 11

an initial stimulus causes a response which reinforces itself

Question 12

Give an example of a positive feedback cycle

Answer 12

damage to a blood vessel
causes activation of clotting factors
which activates thrombin
thrombin activates more clotting factors until damage is covered with clot and the loop stops

Question 13

what are the 2 control systems?

Answer 13

nervous system

endocrine system

Question 14

What is the Central nervous system divided into?

Answer 14

somatic

autonomic

Question 15

what does the autonomic nervous system do?

Answer 15

controls involuntary processes e.g. heart rate

Question 16

what does the somatic nervous system do?

Answer 16

controls voluntary processes- skeletal muscle e.g. movement

Question 17

What’s the autonomic nervous system split into?

Answer 17

sympathetic

parasympathetic

Question 18

do parasympathetic nerves have long or short preganglionic neurons?

Answer 18

long

Question 19

do parasypathetic nerves have long or short postganglonic neurons?

Answer 19

short

Question 20

What areas of the spinal cord do parasympathetic nerves come from?

Answer 20

• cranial

- sacral

Question 21

what is the neurotransmitter of the parasympathetic nervous system?

Answer 21

acetyl choline

Question 22

what situations is the parasympathetic nervous system used in?

Answer 22

vegetative (rest and digest)

Question 23

do sympathetic nerves have long or short preganglionic neurons?

Answer 23

short

Question 24

do sympathetic nerves have long or short postganglionic neurons?

Answer 24

long

Question 25

what areas of the spinal cord do the nerves of the sympathetic nervous system come from?

Answer 25

lumbar

thoracic

Question 26

what’s the difference between noradrenaline and adrenaline?

Answer 26

noradrenaline comes from a nerve, adrenaline comes from an endocrine gland

Question 27

What are the neurotransmitters of the sympathetic nervous system?

Answer 27

• acetyl choline

- noradrenaline

Question 28

what situations activate the sympathetic nervous system?

Answer 28

stress (fight/flight)

Question 29

What’s the main difference between the effects of hormones and those of neurotransmitters?

Answer 29

hormones tend to have longer term effects

Question 30

what feedback system does most of the endocrine system use?

Answer 30

negative

Question 31

describe the negative feedback process of the release of cortisol

Answer 31

Hypothalamus releases the hormone CRH
this stimulates the release of ACTH by the pituitary gland into the blood stream
this stimulates the release of cortisol
the increase in cortisol turns off CRH release
turns off ACTH release
turns of cortisol release

Question 32

describe the positive feedback process of the release of milk during lactation

Answer 32

• suckling stimulates breasts
• oxytocin released in brain
• milk pushed out of breast
  this continues until baby stops suckling

Question 33

what condition is required for positive feedback?

Answer 33

something to stop the cycle