Homeostasis & control systems Flashcards

1
Q

def of homeostasis

A

The maintenance of a constant internal environment

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2
Q

Mechanism of homeostatic regulation - Autoregulation

A

cell, tussue, organ or organ system adjusts in response to environmental change - e.g. dec O2 om tissue = cells release chemicals that dilate clood vessels = more blood gloe = more O2

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3
Q

Mechanism of homeostatic regulation - Extrinsic

A

Activities of nervous system or endorcrine system -
these organ systems detect change
either electrical signal or chemical signal tries to adjust it
e.g. excerise = nervous system increases heart rate, direccts blood flow to right places etc.

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4
Q

Diff between effects of nervous sysrems response and endrocrine systems response

A

Nervous - rapid, short term, specific
Endocrine - slower, longer lastin, affects organs/tissues throughout the body e.g. adustment of organ system during starvation

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5
Q

What does a homeostatic regulatory mechanism consist of?

A

Receptor - sensor for stimuli/environmental changes
Control centre - receives and processes info, sends out commands
Effector - cell or organ that respons to commands, activity opposes or enhances the stimuli

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6
Q

def of negative feedback

A

Aims to maintain a controlled variable at its set point
typically negates the original stimuli in order to minimise change

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7
Q

Thermoregulation as a process in -ve feedback

A

Receptor = skin
Control center = hypothalamus
if int temp rises above 37.2C
Two effectors are activated by CC: -muscle tissue lining of blood (relax, blood vess dilate, inc blood flow near skin suface vessels, - sweat glands (secrete sweat, evap cools)

When back to normal temp, all these processes are signalled to stop

Also remmeber set point for temp changes depending on time of day, individual differences etc.

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8
Q

regulation of BP

A
  • BP lowers
  • Sensor = baroreceptors
  • glosso pharyngeal nerve sends signal to
  • medulla oblongata in brain (CC) (at base connected to spinal cord)
  • autonomic nerves send signal to
  • Heart, blood vessels (effectors)
  • increase in cardiac output (heart rate)
  • inc vasoconstriction

raises BP
process stopped

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9
Q

def of positive feedback

A

initial stimulus produces a response that amplifies/enhances/reinforces itself (rahter than oposing it)

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10
Q

example of positive feedback - blood clotting

A

Damage to blood vessel
Activates clotting factors (chemicals released)
Activation of Thrombin - starts chain reaction
As clotting continues, each step releases chemicals that further accelerate process
When bleeding stops and clot is formed, the loop ends

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11
Q

Branches of the peripheral nervous system

A

Somatic:
Skeletal muscle = concious movement

Autonomic:
- Parasympathetic
- Sypathetic
=smooth & cardiac muscle, glands
(subconscious movement)

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12
Q

general mechanism of autonomic nervous system

A

CNS = Preganglionic neuron –>
Peripheral ganglion = postganglionic –>
target cell

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13
Q

Sympathetic

A
  • more active in stressful situations e.g. fight or flight
  • From CNS = Thoracic & Lumbar
  • preganglionic are SHORT - releases ACETYLCHOLINE to the NICOTINE receptor on the postganglionic
    Ganglionic trnasmitter = ACh (N2)
  • postganglionic are LONG - releases NORADRENALINE to alpha/beta adrenergic receptors (=Neuroeffector transmittor)
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14
Q

Parasympathetic

A
  • active during rest - e.g. digestion etc.
  • From CNS - Cranial & sacral
  • preganglionic fibre are LONG - releases ACETYLCHOLINE to NICOTINIC receptors on postganglionic
    Ganglionic trnasmitter = ACh (N2)
  • postganglionic fibre are SHORT - release ACETYLCHOLINE to muscarinic acetylecholine receptor (=Neuroeffector transmittor)
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15
Q

Adrenal Medulla

A

Instead of the regular sypathetic pathway, preganglionic fiber releases acetylcholine to Nicotinic receptor IN THE ADRENAL MEDULLA - contains chromaffin cell
this releases Adrenaline into circulation

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16
Q

Hormonal control in homeostasis features

A
  • Long term
    e.g. thyroid hormones promote metabolism
    groeth hormmone promote growth duh
    -ve and +ve feedback systems

Two main examples u need to know:
- Cortisol release
- Lactation

17
Q

Release of cortisol mechanism

A
  • CRH released by hypothalamus
  • triggers release of ACTH from anterior pituitary gland into bloodstream
  • travels down to adrenal glands - release of cortisol
  • when cortisol high = detected by hypothalamus = shuts off
    = -ve feedback
  • Happens daily, process starts ~4-5am
  • mobilises energy like glucose, triggers metabolism
  • prepares body to be active when waking up
18
Q

Lactation mechanism

A
  • Suckling from baby
  • triggers oxytocin + prolactin release from posterior pituitary gland
  • causes muscle contraction and dilation of milk ducts - milk is ejected
  • will continue until baby stops suckling
    +ve feedback amplifies the response until external force stops it