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Flashcards in Homeostasis Deck (20)
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0
Q

Is homeostasis usually achieved via negative or positive feedback?

A

Negative

1
Q

What is ‘a tendency towards stability of the internal environment of a healthy organism’?

A

Homeostasis

2
Q

What is mainly achieved by control measures through mainly negative feedback, involving the CONTINUOUS ACTIVITY of sensory receptors?

A

Homeostasis

3
Q

When trying to maintain homeostasis, is it the external or internal environment that is likely to have large fluctuations?

A

External is large (e.g. temp and light)

Internal is small (e.g. temp, pH, glucose, BP)

4
Q

Name 5 internal variables that require homeostatic control

A

Temp, blood glucose, blood volume, blood pressure, calcium, salt, potassium, bicarbonate, osmolarity of blood, oxygen, carbon dioxide etc.

5
Q

Name the following steps in homeostasis:

S……. - I……… C……….. - E………… - correction of the variable: Change in variable

A

SENSOR - INTEGRATING CENTRE - EFFECTOR - correction of the variable - CHANGE IN VARIABLE

6
Q

What type of pathway connects the sensor to the integrating centre in homeostasis?

A

Afferent Pathway

7
Q

What type of pathway connects the integrating centre to the effector in homeostasis?

A

Efferent Pathway

8
Q

In homeostasis, the sensor is sensory receptor cells, where is the integrating centre and the effector?

A

Parts of the CNS like the hypothalamus

Muscle/secretory cells like blood vessels/sweat glands

9
Q

Outline the negative feedback process if the external temperature was to become really cold

A

The receptors in the skin would pick up the change
The hypothalamus would detect this and send signals to the effectors
Blood vessels contract, skeletal muscle twitches, muscle around hair follicles contract
Body temp increases and tells sensor to stop the effects

10
Q

Body temperature and blood pressure are examples of what type of feedback in homeostasis?

A

Negative Feedback

11
Q

Blood clotting and contractions in child birth are examples of what type of feedback in homeostasis?

A

Positive Feedback

12
Q

How does positive feedback work in blood clotting?

A

Damage to blood vessel activates clotting factors
Clotting factors activate thrombin
Thrombin keeps activating clotting factors (as well as forming blood clot)

13
Q

How does positive feedback work in childbirth?

A

Head of fetus on cervix sends nerve impulses to brain
Brain stimulates pituitary gland to secrete oxytocin
Oxytocin goes to uterus to stimulate contractions and also pushes fetus against cervix again

14
Q

What type of feedback decreases the effect of the original stimulus in homeostasis?

A

Negative

15
Q

What type of feedback increases the effect of the original stimulus in homeostasis?

A

Positive feedback

16
Q

What is the key integrative centre in homeostasis that converts synaptic signals to humoral/hormonal signals?

A

Hypothalamus/Pituitary Axis

17
Q

What does the hypothalamus respond to in homeostasis?

A

The feedback from the system it controls

18
Q

What area of the brain controls hormone secretion from the pituitary gland? (which acts on many systems)

A

Hypothalamus

19
Q

Can the hypothalamus affect the feeling of stress?

A

Yes - as it can get the pituitary gland to secrete cortisol in stressful situations - this affects the heart, muscles, GI tract and blood vessels

But cortisol also has negative feedback as inhibits corticotrophin to stop constant stress