Physiology
Lecture 1, introduction:
All organisms exist to pass on genes to future generations, beyond the life of
individuals members of a species.
All physiological mechanisms follow the same list of priorities;
1. Survival (survival of the individual)
2. Growth (survival of the individual)
3. Reproduction (survival of the species)
4. Care (survival of the species)
Bushman example:
Man sits in the bush and sees a lion, through a cascade of mechanisms in the human
body the fight or flight response is activated.
The perception of the stress stimulant is deciphered in the brain, the brain
communicates a response to the body via hormones and neurotransmitters.
Adrenaline goes up, insulin goes down (because you don’t have time to eat if you are
being eaten), heart rate and blood pressure goes up. The blood distribution changes,
and the availability of energy supplies is increased.
Irrelevant processes are shut down, such as the gut and the immune system. Because
of this, chronic stress disorders inhibit the immune system to save energy and thus
connects this stress disorders to illnesses.
Pathological stress:
When no fight or flight response is necessary. Like when one exhibits stress for a
presentation. The blood pressure still goes up, which can in turn damage the blood
vessels, when exposed to chronic/ long term stress.
Homeostasis:
This is the state to which the internal, physical and chemical conditions always return
for the optimal functioning of an organism.
If through external (e.g food shortage) or internal (e.g fever) changes the homeostasis
is lost, the organism shall always attempt to compensate or restore this homeostasis.
If this is successful, the organism lives well, but if it fails the organism gets an illness
which can lead to death.
Negative feedback:
The homeostasis can be maintained through negative feedback. The response to the
stimulus, counteracts the stimulus and thus terminates the loop.
Things needed for negative feedback:
- Perturbing factor, something to cause a stimulus.
- Stimulus, something to alter the homeostasis.
- Sensor, something that constantly monitors the conditions in the internal
environment.
- Integrating center, something that the monitored conditions to the homeostatic
values.
- Effector, something to cause a change to compensate for the alternation to the
homeostasis.
- Response, the return to homeostatic values.
For example, when the body gets to hot it creates sweat and the blood vessels close
to the surface are dilated to get rid of the warmth, but it also causes behavioral
changes, such as eating ice cream to cool down.
,Positive feedback:
The response to the stimulus, reinforces the stimulus and thus sending the variable
only further from the set point. The most popular example is during childbirth, the
mother oxytocin when the baby pushes against the cervix, which causes the uterine to
contract and the baby to push against the cervix more. This only stops when the baby
is out.
Communication:
The communication in the body can go through; blood, lymph, air, water of the
nervous system.
The tools used for this are; hormones, neurotransmitters and pheromones.
Chemical communication from cells can be;
- Autocrine, when cells secrete hormones which then bind to the receptors of the
same cell.
- Paracrine, when cells secrete hormones which bind to neighboring cells without
transport. Other examples of this are gap junctions, they form direct cytoplasmic
connections between two neighboring cells. Or contact-dependent signals which
require interaction from the membrane molecule on two cells.
- Endocrine, when endocrine cells or glands secrete hormones which travel through
blood to another cell. The hormones only target cells with the right receptors.
- Neurocrine, when neurons secrete neurotransmitters which travel through the
neuron to the target cell.
- Neuroendocrine, when neurons secrete neurohormones which firstly travel
through neurons and then through the bloodstream to another cell.
- Neurotransmission, when neurons secrete neurotransmitters to another neuron.
Pheromones:
They travel through air and influence other organisms, mostly for reproductive
activities. They are perceived by the vomeronasal organ. The example for this is the
chairs at the dentist, of the synchronized menstrual cycle.
,Lecture 2, signal pathways:
All signals start with a signal molecule that binds to the transducer, which converts
the extracellular signal to a intercellular signal. They can have multiple targets.
In this system, the extracellular signal is the first messenger and the extracellular
signal is the second messenger.
The second messenger is amplified by amplifier proteins and can be used to, for
example, alter the gating of ion channels or change the enzyme activity.
Signal transduction happens in a lot of steps, called a cascade, to gain more control, to
get more amplified. Because more complexity equals more specificity.
Receptors;
The receptors to which ligands can bind can either be on the membrane, in the cytosol
or in the nucleus. Ligands that are hydrophobic and can pass through the membrane
on its own, bind to the cytosol- or nucleus receptors. Ligands that are hydrophilic and
cannot pass through the membrane need to bind to the membrane receptors to pass
through.
Membrane receptors lead to a rapid response, and cytosol- or nucleus receptors lead
to a slower response.
The four types of membrane receptors:
- Receptor channels, found mostly in nerve and muscles. The channel is only
opened when a ligand binds to it, and is closed when the ligand leaves or when an
antagonist binds to the channel. This is the most rapid way to get ions in or out of
the cell (electrical signaling)
- G protein, most signal transduction use a G-protein. The G-protein is also coupled
to a GPCR (G-protein coupled receptor), when a ligand binds to the GPCR the G-
protein is activated. G-proteins can either bind with adenylyl cyclase, this converts
ATP to three times cAMP. These cAMP activate kinase proteins that can
phosphorylate other proteins. G-proteins can also activate phospholipase C (PLC).
PLC converts membrane phospholipids into IP3 and diacylglycerol (DAG). DAG also
activates kinases to phosphates other proteins. And IP3 releases Ca2+ from
organelle which creates a Ca2+ signal, this signal is called the calcium spark.
- Receptor-enzyme, when a ligand binds to the receptor, the intercellular enzyme
attached is activated.
- Intergin-receptor, when a ligand binds to the receptor, the cytoskeleton it is
attached to alters.
Signal molecules:
Gases that are dissolvable and suitable for short-acting paracrines or autocrines;
- Nitric oxide (NO), acts as a neurotransmitter and a neuromodulator in the brain. And
activates guanylyl cyclase.
- Carbon monoxide (CO), also activates guanylyl cyclase.
- Hydrogen sulfide (H2S), targets the cardiovascular system to relax blood vessels.
One ligand can have different receptors and the receptors determine the result. So
can adrenaline bind to the alpha-receptor on a blood vessel to constrict the vessel en
thus increase the blood pressure. But when adrenaline binds to the beta-receptor in
the blood vessel, the vessel dilates and thus the blood pressure decreases.
Agonist: is a type of ligand that activates the receptor.
Antagonist: is a type of ligand that blocks the receptor from binding to a agonist.
, Tonic control: is the same signal, mostly electrical signals from neurons, but the
intensity increases or decreases which determines the response.
Lecture 1, introduction:
All organisms exist to pass on genes to future generations, beyond the life of
individuals members of a species.
All physiological mechanisms follow the same list of priorities;
1. Survival (survival of the individual)
2. Growth (survival of the individual)
3. Reproduction (survival of the species)
4. Care (survival of the species)
Bushman example:
Man sits in the bush and sees a lion, through a cascade of mechanisms in the human
body the fight or flight response is activated.
The perception of the stress stimulant is deciphered in the brain, the brain
communicates a response to the body via hormones and neurotransmitters.
Adrenaline goes up, insulin goes down (because you don’t have time to eat if you are
being eaten), heart rate and blood pressure goes up. The blood distribution changes,
and the availability of energy supplies is increased.
Irrelevant processes are shut down, such as the gut and the immune system. Because
of this, chronic stress disorders inhibit the immune system to save energy and thus
connects this stress disorders to illnesses.
Pathological stress:
When no fight or flight response is necessary. Like when one exhibits stress for a
presentation. The blood pressure still goes up, which can in turn damage the blood
vessels, when exposed to chronic/ long term stress.
Homeostasis:
This is the state to which the internal, physical and chemical conditions always return
for the optimal functioning of an organism.
If through external (e.g food shortage) or internal (e.g fever) changes the homeostasis
is lost, the organism shall always attempt to compensate or restore this homeostasis.
If this is successful, the organism lives well, but if it fails the organism gets an illness
which can lead to death.
Negative feedback:
The homeostasis can be maintained through negative feedback. The response to the
stimulus, counteracts the stimulus and thus terminates the loop.
Things needed for negative feedback:
- Perturbing factor, something to cause a stimulus.
- Stimulus, something to alter the homeostasis.
- Sensor, something that constantly monitors the conditions in the internal
environment.
- Integrating center, something that the monitored conditions to the homeostatic
values.
- Effector, something to cause a change to compensate for the alternation to the
homeostasis.
- Response, the return to homeostatic values.
For example, when the body gets to hot it creates sweat and the blood vessels close
to the surface are dilated to get rid of the warmth, but it also causes behavioral
changes, such as eating ice cream to cool down.
,Positive feedback:
The response to the stimulus, reinforces the stimulus and thus sending the variable
only further from the set point. The most popular example is during childbirth, the
mother oxytocin when the baby pushes against the cervix, which causes the uterine to
contract and the baby to push against the cervix more. This only stops when the baby
is out.
Communication:
The communication in the body can go through; blood, lymph, air, water of the
nervous system.
The tools used for this are; hormones, neurotransmitters and pheromones.
Chemical communication from cells can be;
- Autocrine, when cells secrete hormones which then bind to the receptors of the
same cell.
- Paracrine, when cells secrete hormones which bind to neighboring cells without
transport. Other examples of this are gap junctions, they form direct cytoplasmic
connections between two neighboring cells. Or contact-dependent signals which
require interaction from the membrane molecule on two cells.
- Endocrine, when endocrine cells or glands secrete hormones which travel through
blood to another cell. The hormones only target cells with the right receptors.
- Neurocrine, when neurons secrete neurotransmitters which travel through the
neuron to the target cell.
- Neuroendocrine, when neurons secrete neurohormones which firstly travel
through neurons and then through the bloodstream to another cell.
- Neurotransmission, when neurons secrete neurotransmitters to another neuron.
Pheromones:
They travel through air and influence other organisms, mostly for reproductive
activities. They are perceived by the vomeronasal organ. The example for this is the
chairs at the dentist, of the synchronized menstrual cycle.
,Lecture 2, signal pathways:
All signals start with a signal molecule that binds to the transducer, which converts
the extracellular signal to a intercellular signal. They can have multiple targets.
In this system, the extracellular signal is the first messenger and the extracellular
signal is the second messenger.
The second messenger is amplified by amplifier proteins and can be used to, for
example, alter the gating of ion channels or change the enzyme activity.
Signal transduction happens in a lot of steps, called a cascade, to gain more control, to
get more amplified. Because more complexity equals more specificity.
Receptors;
The receptors to which ligands can bind can either be on the membrane, in the cytosol
or in the nucleus. Ligands that are hydrophobic and can pass through the membrane
on its own, bind to the cytosol- or nucleus receptors. Ligands that are hydrophilic and
cannot pass through the membrane need to bind to the membrane receptors to pass
through.
Membrane receptors lead to a rapid response, and cytosol- or nucleus receptors lead
to a slower response.
The four types of membrane receptors:
- Receptor channels, found mostly in nerve and muscles. The channel is only
opened when a ligand binds to it, and is closed when the ligand leaves or when an
antagonist binds to the channel. This is the most rapid way to get ions in or out of
the cell (electrical signaling)
- G protein, most signal transduction use a G-protein. The G-protein is also coupled
to a GPCR (G-protein coupled receptor), when a ligand binds to the GPCR the G-
protein is activated. G-proteins can either bind with adenylyl cyclase, this converts
ATP to three times cAMP. These cAMP activate kinase proteins that can
phosphorylate other proteins. G-proteins can also activate phospholipase C (PLC).
PLC converts membrane phospholipids into IP3 and diacylglycerol (DAG). DAG also
activates kinases to phosphates other proteins. And IP3 releases Ca2+ from
organelle which creates a Ca2+ signal, this signal is called the calcium spark.
- Receptor-enzyme, when a ligand binds to the receptor, the intercellular enzyme
attached is activated.
- Intergin-receptor, when a ligand binds to the receptor, the cytoskeleton it is
attached to alters.
Signal molecules:
Gases that are dissolvable and suitable for short-acting paracrines or autocrines;
- Nitric oxide (NO), acts as a neurotransmitter and a neuromodulator in the brain. And
activates guanylyl cyclase.
- Carbon monoxide (CO), also activates guanylyl cyclase.
- Hydrogen sulfide (H2S), targets the cardiovascular system to relax blood vessels.
One ligand can have different receptors and the receptors determine the result. So
can adrenaline bind to the alpha-receptor on a blood vessel to constrict the vessel en
thus increase the blood pressure. But when adrenaline binds to the beta-receptor in
the blood vessel, the vessel dilates and thus the blood pressure decreases.
Agonist: is a type of ligand that activates the receptor.
Antagonist: is a type of ligand that blocks the receptor from binding to a agonist.
, Tonic control: is the same signal, mostly electrical signals from neurons, but the
intensity increases or decreases which determines the response.
