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Bio gr 12 > Homeostasis 2 > Flashcards

Homeostasis 2 Flashcards

1
Q

Receptor (sensor)

A

detects change.. which sends a signal to a control centre

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2
Q

Control centre (integrator)

A

compares with normal level which sends a signal to an Effector

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3
Q

Effector

A

responds to change

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4
Q

a change in the bodys internal or external environment is detected by….

A

a recepter

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5
Q

A nerve impulse is sent along a ………… to the brain (control centre) then along a …….to the ……….

A

sensory neuron….. motor neuron … effector

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6
Q

…… are often glands which will respond by sending ……….. ….. called hormones into the blood

A

Effectors…. chemical messengers….

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7
Q

What are hormones?

A

Chemical messengers (signals) released by cells into the blood stream that are transported via the blood stream to act on distant target cells
60 + hormones identified by chemical structure

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8
Q

hormones are specific: (how/why)

A

only activate cells with tissues that posess the target receptor

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9
Q

What do target cells possess?

A

receptors that recognize the hormones, others do not possess this

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10
Q

Which two systems work together to control organs and tissues

A

Nervous system and Endocrine

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11
Q

Nervous system

A

responds quickly to environment changes

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12
Q

Endocrine system

A

takes longer but maintains control over long period of time

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13
Q

What is the endocrine system composed of (4)

A

-A system of ductless sensory organs
-endocrine glands secrete hormones directly into the blood
=blood transports hormones to target tissues
- hormones help the cells in the tissues to elicit a response to maintain homeostasis

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14
Q

Exocrine Glands

A

do notsecrete hormones into blood or extracellular fluid, into specific ducts that lead outside or into body cavities
ex. salivary glands sweat glands, mammary glands

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15
Q

protein hormones

A

are polar and water soluble range between 3-200 amino acids long
-cannot cross lipid bilayer, can combine with surface receptors
-causes a series of events and changes in cell
- insulin, growth hormone

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16
Q

Protein Hormone Pathway

A

-Protein hormones bind to cell membrane receptor molecules.
Receptor molecule changes shape.
-Signal activates and is sent inside the cell (through membrane)
-Signal calls for changes to occur (ie. enzyme release or activation, etc)

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17
Q

Glucagon

A

Hormone GLUCAGON binds to liver receptor cells → phosphate groups are added → enzyme activated → glycogen broken down to glucose

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18
Q

Steroid Hormones

A

Steroid hormones are made from a nonpolar cholesterol (lipid) precursor. They are not soluble in water, but are lipid soluble.

Can diffuse through phospholipid bilayer into target cells where they combine with receptor molecules in the cytosol

Then ‘hormone-receptor complex’ moves into nucleus and activates a gene to produce a specific protein

Ex. Testosterone and Estradiol

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19
Q

Steroid Hormone Pathway

A

-Steroid hormones cross membrane
-Bind to cell receptors (in cytosol or nucleus)
-Hormone-receptor complex binds to a gene control sequence
-Turns gene on/off
-Protein production is activated/deactivated and cell activity changes

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20
Q

Cells can only respond if they have…

A

receptors for hormones to bind to (in/out)

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21
Q

Hormone receptor complexes respond by…

A

turning them on and off

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22
Q

amplification

A

occurs when hormones bind to receptors. Proteins activated, activate other proteins

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23
Q

are hormone responses the same across species

A
  • hormone response different among species
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24
Q

Peptide synthesis

A

synthesized as prohormones- require further processing (e.g. cleavage ) to activate

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25
Q

Peptide storage

A

Stored in vesicles (regulatory secretion)

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26
Q

peptide solubility

A

most are polar and soluble, can travel freely in blood

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27
Q

Peptide receptors

A

-bind receptors on cell membrane and transduce signal via the use of second messanger systems

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28
Q

effects peptide

A

often fast onset transient changes in protein activity, though gene expresssion changes can occur

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29
Q

Steroid synthesis

A

synthesized in a series of reactions from cholesterol

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30
Q

steroid storage

A

released immediately (constitutive secretion)

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31
Q

Steroid solubility

A

general non-polar and require carrier proteins to travel blood

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32
Q

Steroid receptors

A

bind to intracellular receptors to change gene expression directly

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33
Q

Effects Steroids

A

alterations in gene expression, slower onset, longer duration than peptide hormones

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34
Q

what are many hormones used as signals for

A

Negative feedback loops

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35
Q

The Hypothalamus

A

The hypothalamus is the section of the brain that links the nervous and endocrine systems in order to maintain homeostasis

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36
Q

Hypothalamus function

A

-Receives information from nerves throughout the body and other parts of the brain and initiates endocrine responses
-Secretes certain neurochemicals (called releasing factors) into a portal system which stimulate or inhibit the pituitary gland
-Secretes certain hormones directly into the bloodstream via neurosecretory cells that extend into the pituitary gland

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37
Q

The Pituitary Gland

A

The “Master Gland”

Secretes hormones which affect most other endocrine glands and interacts with the nervous system (the hypothalamus)

Two parts: Anterior and Posterior Lobes

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38
Q

Pituitary Gland - Posterior Lobe

A

Stores and secretes hormones produced by the hypothalamus

ADH – acts on kidneys to reabsorb more water back into blood and causes vasoconstriction to increase blood pressure (aka vasopressin)

Oxytocin - causes uterine contractions during labour and milk production in Mammary glands (also associated with bonding)

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39
Q

Pituitary Gland - Anterior Lobe

A

Produces its own hormones however release is still regulated by the hypothalamus

Thyroid Stimulating Hormone
Reproductive Stimulating Hormones (LH and FSH)
Growth Hormones
Prolactin
Adrenocorticotropic Hormone (ACTH)

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40
Q

Growth Hormone (GH)

A

promotes protein synthesis by increasing the uptake of amino acids by cells

Too little GH – dwarfism
Too much GH - gigantism

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41
Q

Blood Sugar - The Pancreas

A

Alpha and beta cells are found in the Islets of Langerhans in the pancreas

They produce glucagon or insulin depending on blood sugar level of the body

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42
Q

Metabolism: The Thyroid

A

The Thyroid Gland produces mainly Thyroxine (T4) and Calcitonin

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43
Q

calcitonin

A

bones, lowers calcium conc. in blood

44
Q

Thyroxine (T4)

A

most cells, increase metabolic rate essential for body growth

45
Q

thyroxine importance

A

Thyroxine contains 4 iodine atoms in its structure.

A lack of iodine in the diet means thyroxine cannot be produced so the anterior pituitary continually sends signals (thyroid stimulating hormones) to your thyroid to produce it.

An overstimulation causes the thyroid to enlarge creating a swelling in the neck called a goiter

46
Q

Parathyroid Hormone and calcium

A

low conc. of clacium in blood leads torelease of parathyroid hormone, eillux of calcium from bone, decreased loss of calcium in urine, enhanced absorption in intenstine

47
Q

Stress & Cortisol

A

Stress hormones provide more blood glucose to cope with the elevated energy requirements brought on by stress.

48
Q

Epinephrine

A

aka adrenaline) is produced by the adrenal gland in response to stress.

It mobilizes (breaks down) stored energy which increase blood glucose which increase energy quickly!

Increases alertness/awareness
Accelerates heart rate
Increases activity of resp. system
Prepares body to do something fast like run from a bear, lift a car off your child, etc.

49
Q

Cortisol

A

Produced in the adrenal gland and released in response to stress and a low level of blood glucose. Its primary functions are to:

Increase blood glucose through gluconeogenesis
Suppress the immune system
Aid in fat, protein and carbohydrate metabolism

50
Q

2 Parts of the Nervous System

A

Central Nervous System (CNS)
Peripheral Nervous System (PNS)

51
Q

Peripheral Nervous System (PNS)

A

All the neurons that carry signals between the CNS and the rest of the body

52
Q

Central Nervous System (CNS)

A

Brain and spinal cord

53
Q

The CNS

A

The central nervous system (CNS) acts as the control centre in many negative feedback loops. The majority of this activity occurs in the brain, but certain responses can be mediated by the spinal cord (reflexes)

54
Q

The PNS

A

The peripheral nervous system (PNS) sends information from receptors to the CNS via afferent sensory neurons and activates effectors via efferent motor neurons

55
Q

What is the PNS divided into

A

The anatomy of the PNS is divided into the sensory (afferent) pathway and the motor (efferent) pathway

56
Q

The motor pathway

A

can be divided according to whether the response is voluntary (somatic) or involuntary (autonomic)

57
Q

autonomic division (involuntary motor pathway)

A

can be split into sympathetic (‘fight or flight’) or parasympathetic (‘rest and digest’) responses

58
Q

Glial Cells

A

non-conducting cells, used for structural support and metabolism for nerve cells

59
Q

Neurons

A

nerve cells that conduct nerve impulses
Three main types: sensory, inter, and motor

60
Q

what are the 3 main types of neurons:

A

sensory, inter and motor.

61
Q

Each neuron has:
???

A

-a cell body (contains nucleus & organelles)
-dendrites (receive signals from other cells)
-axons (carry impulses away from the cell body)

62
Q

Sensory (Afferent) Neurons

A

Sensory Neurons carry impulses from inside and outside the body to brain and spinal cord. One long dendrite carries nerve impulses from sensory receptor cells to the cell body. One short axon carries impulses away from the cell body to the CNS.

63
Q

Interneurons

A

Interneurons are found within brain and spinal cord, and process incoming impulses and pass them on to motor neurons. They have many short dendrites and many short axons.

64
Q

Motor (Efferent) Neurons

A

Motor neurons carry impulses away from the brain and spinal cord. Many short dendrites carry impulses from the CNS to the cell body. One long axon carries impulses away from the cell body to effector cells (muscles or glands).

65
Q

Axons

A

Axons are bundled together to form nerve fibres similar to the way small fibres are bundled together to form a fibre-optic cable

66
Q

Neuron Support

A

chwann Cells (a type of Glial Cell) form tightly wrapped layers around axons called Myelin Sheaths (electrical insulation).

Gaps between the Schwann Cells are called Nodes of Ranvier (ECF exposure)

These support cells allow for the rate of electrical impulses to be as high as it is

67
Q

Neural Circuits

A

A neural circuit is the pathway from a stimulus through the different neuron types in response to a stimulus

68
Q

Neural Circuit steps

A
  1. Receptors in the skin sense touch or other stimuli.
    2.Afferent/Sensory neurons transmit the touch message.
  2. Information is sorted and interpreted in the brain. A response in determined by interneurons.
  3. Efferent/Motor neurons transmit a response message to the shoulder muscles.
  4. The shoulder muscles are activated, causing the head to turn.
69
Q

Membrane Potential

A

Any animal cell will have a separation (outside is positive, inside is negative) of charges across a membrane. Membrane potential is this potential difference (voltage) across the membrane.

70
Q

Nerve Impulses

A

are small changes in electrical charge or potential being passed from cell to cell

71
Q

What are nerve impulses cause by

A

This is caused by K+ and Na+ ions moving in and out of the cell through ion channels.

72
Q

Electrochemical Potential

A

-electrochemical potential is changed and maintained by sodium-potassium pumps and potassium and sodium ion channels
-The K+-Na+ pumps move 3 sodium out for every 2 potassium in using active transport (net negative charge inside)
-The channels allow specific ions to diffuse through, but only at certain voltages

73
Q

Resting Potential

A

At rest (unstimulated) the inside of a neuron is negatively charged relative to the outside. This is called the resting potential and is about -70mV.

74
Q

What is Action Potential

A

An action potential is a temporary change in the membrane potential. This occurs when a neuron conducts an impulse.

75
Q

Neuron at Rest

A

At rest the K+-Na+ pump is working, and the sodium ions cannot diffuse back into the cell, so there are more positive ions outside the cell than in. This means the inside of the cell is negatively charged at -70 mV. The cell is polarized.

76
Q

Stimulation & Depolarization

A

When first stimulated, the membrane potential becomes less negative. Once it reaches its threshold potential (-55mV) the sodium channels open allowing some Na+ ions to diffuse into the cell.

77
Q

Depolarization

A

At -55 mV, more sodium channels open and Na+ ions flood into the cell making it positive. We can imagine this as the cell ‘firing’.

78
Q

Repolarization

A

At +30 mV, sodium channels close and potassium channels open. The K+ ions that were locked in the neuron the whole time diffuse out, bringing the potential back towards its resting level.

79
Q

Hyperpolarization

A

The potassium channels are slow to close, so the charge goes lower than the cell is at rest (below -70 mV)

80
Q

Back to Rest

A

The ion channels are closed and reset, and the sodium-potassium pump returns the membrane to its resting potential (-70 mV).

The time from when the sodium channels close to this stage is called the refractory period, after which the cell can be made to fire again.

81
Q

Action Potentials- what kind of signal and why, how does it change depending on strength of stimulus

A

Because there is a refractory period after a cell fires, each action potential travels as a separate signal

All action potentials are the same size (+30 mV) no matter how strong the stimulus is (it is an ‘all or nothing’ response), but a stronger stimulus will cause neurons to fire more frequently

82
Q

How does action potential travel

A

The action potential travels down the axon as a wave of depolarisation as the sodium ion channels open/close in sequence like at sporting event when people do ‘The Wave’. The wave moves away from areas in the refractory period as they can’t fire.

83
Q

The Myelin Sheath is important for two reasons:

A
  1. Protects nerves from damage
  2. Speeds up transmission of an impulse
84
Q

The Nodes of Ranvier are useful for three reasons:

A
  1. Cause impulse to jump from node to node
  2. Speeds up transmission of impulse
  3. Sodium Channels for action potential (concentrated at no
85
Q

Myelin Sheath

A

The gaps between the Schwann cells are called nodes of Ranvier. The sodium channels are concentrated at these nodes. In a myelinated neuron, depolarisation only happens here, making the signal jump from node to node. This is faster than if it travelled along the whole length.

86
Q

What do neurons do at rest

A

Neurons at rest push Na+ ions out and keep K+ ions in giving them a negative charge (polarized)

87
Q

nerve impulses summary

A

Neurons at rest push Na+ ions out and keep K+ ions in giving them a negative charge (polarized)

Nerve impulses or action potentials are generated when Na+ ions enter the neuron causing the internal charge to rapidly increase for a millisecond (depolarization)

To repolarize the neuron will let the K+ ions out so the charge drops

There will be a short time (refractory period) where the cell is too negative to fire again, but stimulated neurons fire many times a second

88
Q

Synapses

A

Nerve impulses only travel in one direction in the neuron - away from the cell body along the axon. The connection between two neurons or neuron/effector is called a synapse.

89
Q

What is the neuron before the synapse is called?

A

presynaptic neuron

90
Q

What is the neuron being signalled called

A

Postsynaptic neuron

91
Q

Electrical Synapses

A

In electrical synapses the two membranes of the neurons (or effector) are in direct contact. When impulses arrive, a gap junction is made and ions can flow directly.

92
Q

What does the presynaptic neuron contain/ where/ when are they released

A

neurotransmitters which are released across a microscopic gap called a synaptic cleft, when there is an action potential.

The neurotransmitters diffuse across the synapse and bind to specific receptors on the postsynaptic membrane

If enough receptors are hit they can trigger a continued action potential in the postsynaptic neuron

When the action potential arrives at the presynaptic membrane, voltage gated calcium ion channels open and Ca2+ ions diffuse into the cell

This causes the vesicles containing neurotransmitters to move to the membrane and release them into the synaptic cleft by exocytosis

93
Q

Where are neurotransmitters found, how does it move?

A

Because the neurotransmitters are only in the presynaptic membrane, the signal can only travel in one direction: axon ➞ dendrite

94
Q

what happens once the neurotransmitters are released

A

Once released, the neurotransmitters diffuse across the synapse to hit postsynaptic receptors

95
Q

Neurotransmitters remaining in the cleft are ….. and called

A

absorbed back into the presynaptic neuron in a process called reuptake

96
Q

When neurotransmitters bind to specific receptors on the postsynaptic membrane they cause

A

sodium channels to open

97
Q

What happens If enough neurotransmitters hit receptors, the post-synaptic cell

A

reaches the threshold (-55mV), and the action potential will continue (fire) in the next neuron

Neurotransmitters are reabsorbed into the presynaptic membrane (reuptake) shortly after they are released and any remaining Ca2+ and Na+ ions are pumped out of the cell using active transport

98
Q

Synaptic Divergence

A

If one neuron’s axon synapses with many neurons’ dendrites, the action potential is weakened but can be dispersed to different pathways

99
Q

Synaptic Convergence

A

If many neurons’ axons synapse with one neuron’s dendrite, the action potential is amplified

This summation is called synaptic convergence

100
Q

Adrenaline

A

fight or flight nerotransmitter

101
Q

Noradrenaline

A

concentration enurtransmitter

102
Q

Dopamine

A

pleasure

103
Q

seratonin

A

mood

104
Q

GABA

A

calming

105
Q

acetylcholine

A

learning

106
Q

Gluamate

A

Memory

107
Q

Endorphines

A

euphoria

Bio gr 12 (3 decks)

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