Lecture 3 - Homeostasis

Question 1

A typical negative feedback loop

Answer 1

Change in variable to a level that is not ideal -> monitored by receptor cells -> signal travels down afferent pathways to the integrating centre (the centre that can counteract the issue) -> signal travels down efferent pathways to effectors (usually muscle cells or secretory cells) -> homeostasis obtained

Question 2

Blood levels in the brain are not ideal - the negative feedback loop

Answer 2

Blood levels not ideal -> baroreceptors in the carotid artery send signals to the Medulla oblongata in the brain -> sends signals through the autonomic system to the heart blood vessels -> blood vessels then take up the action to reverse the issue

Question 3

Nervous system’s two parts

Answer 3

Central nervous system (brain, spinal cord)
Peripheral nervous system (cranial nerves, spinal nerves)

Question 4

Peripheral nervous system’s two parts

Answer 4

Autonomic nervous system (cardiac muscle, smooth muscle, glands)
Somatic nervous system (voluntary skeletal)

Question 5

Autonomic nervous system’s two parts

Answer 5

Parasympathetic (relaxed)
Sympathetic (active)

Question 6

Negative feedback: what is it in the human body?

Answer 6

In the human body, this kind of feedback loop acts to resist or reverse the process when conditions go outside of the range.

Question 7

Positive feedback: what is it in the human body?

Answer 7

Instead of reversing it, positive feedback encourages and intensifies a change in the body’s physiological condition, actually driving it farther out of the normal range. This type of feedback is normal for the body, provided there is a definite endpoint.

Question 8

Blood clotting as a form of positive feedback

Answer 8

Damage to blood vessels causes clotting factors to be produced, this encourages the activation of thrombin which causes fibrinogen (soluble in blood) to form fibrin (insoluble) which produces a scab.

Positive feedback occurs as clotting factors cause thrombin to be produced which activates more clotting factors. This occurs until the clot is fully formed

Question 9

Nervous system speeds

Answer 9

Fast (reflexes)

Question 10

Endocrine system speeds

Answer 10

Slow (growth, metabolism)

Question 11

Parasympathetic and sympathetic nervous system similarities

Answer 11

Both have the same basic structure of a preganglionic fibre that has come from the CNS, which then interacts with a ganglion, and then the postganglionic fibre send the message to the target cell

Question 12

Ganglion

Answer 12

A structure containing a number of nerve cell bodies, typically linked by synapses, and often forming a swelling on a nerve fibre.

Question 13

The adrenal medulla

Answer 13

Functions similarly but a little different to the ANS

PreG fibre reaches the adrenal medulla and secretes acetylcholine. This, instead of causing a signal to be sent down a PostG fibre, causes the medulla to release epinephrine and this will circulate the blood stream until it reaches its target (adrenergic receptors in the heart)

Question 14

Parasympathetic nervous system:
* outflow from the CNS
* PreG nerve fibre
* ganglionic transmitter
* PostG nerve fibre
* neuroeffector transmitter

Answer 14

PNS:
* Cranial and sacral parts
* Long
* ACh (binding to nicotinic receptors)
* Short
* Noradrenaline (binding to adrenergic recepr)

Question 15

Sympathetic nervous system:
* outflow from the CNS
* PreG nerve fibre
* ganglionic transmitter
* PostG nerve fibre
* neuroeffector transmitter

Answer 15

SNS:
* Thoraic and lumbar parts
* Short
* ACh (binding to nicotinic receptors)
* Long
* ACh