Summary
Physiology, Biology, RUG, 1st year, 2022/2023, summary
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Summary of all the information from the lectures with added information from the book Human Physiology - Dee Silverthorn.
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PhysiologyPhysiology
The organism exists and functions so that the genes can survive beyond the mortal life of individual
members of a species.
Physiological mechanisms follow this rule.
1. Stay alive → everything that threatens your life gets priority
2. Growth → you can only reproduce when you’re full grown
3. Reproduction
4. Care
physiology studies the functioning of the body
- Molecular (intracellular) level
- Organ level
- Interactions between organisms and the environment
- Integrative physiology
- Homeostasis
o Feedback mechanisms
- (patho)physiology
Bushman’s physiology
Perception of the stress stimulus in the brain (visual, auditive, etc) → activation of the fight-flight
response. Activation of brain areas involved in the release of energy substrates and stimulation of
the cardiovascular system. Communication between brain and body through chemical messengers:
neurotransmitters and hormones.
- Adrenalin ↑, sympathetic nervous system ↑
- Activation of several processes in the body
o Pancreas → insulin ↓, liver → glucose release
o White adipose tissue → release of fatty acids
o Heart rate ↑ and blood pressure ↑
- Increased availability of energy substrates and changes in blood distribution
- ACTH and cortisol ↑
- Inhibition of ‘irrelevant’ processes, a.o. the gut and the immune system
Fight/flight: released glucose and free fatty acids are utilized by the active muscle.
That’s functional. No fight/flight: pathological condition. There are less functional
moments like when you are nervous. Adrenalin response during an oral presentation →
Stress (patho)physiology
Stress situations associated with elevated adrenalin and noradrenalin levels,
increased heart rate and blood pressure, release of glucose and FFAs
- Speaking in public including lectures
- Parachute training
, - Erotic movies, thrillers, horror
- Exam
- Hypnosis (fear, exercise)
Fight/flight: released glucose and FFAs are utilized by the active muscle.
No need for fight/flight: chronic increased blood pressure, storage of fat in the
endothelium → pathology.
Homeostasis
Claude Bernard → internal environment
Walter Canon → concept of homeostasis → everything is regulated and is tried to keep in balance.
- Feedback
- Setpoint
- Failure of homeostasis: pathology
You need systems that inform you when something fails
→ feedback systems. If you want to keep everything in
balance you need a setpoint. The setpoint says what is
‘normal’. The effect of food deprivation and forced
overfeeding in this picture is compensated for example by a higher temperature
while you’re sleeping. There is a sort of setpoint for this group of animals. When
they stopped overfeeding the group, the body weight increased rapidly (at the arrow)
If the compensation fails there is pathology. If the compensation succeeds the
homeostasis will be set again.
Some setpoints are really fixed like blood pressure, glucose level etc. Some
change during the day like temperature of you body, that is still called a
setpoint.
Negative feedback loop
You start at the setpoint. We have a sensor
that continually measures a specific thing like
glucose level. When a stimulus changes the
sensor sends this to the integrating center. The
integrating center compares conditions to setpoint. This
sends it to the effector that causes changes to
compensate for deviation. The response is that it is
brought back to ‘normal’ again. When it’s normal again
the sensor gets negative feedback that it should stop
sending. The systems can be in conflict with each other. Eating to much can
be bad for the glucose homeostasis but you need it for your energy systems.
Positive feedback loop
For example while giving birth. When a fetus is full grown there
will be stretch receptors activated. The brain releases the
hormone oxytocin, that activates contraction in the uterus. The
more stretch there already is, the more the brain wants.
,Communication
Integrative physiology and homeostasis: bodily
functions are integrated. This requires
communication.
Ways of communications
- Nervous system
- Blood
- Lymph
- Air
- Water
Communication tools
- Neurotransmitters
- Hormones
- Pheromones etc.
Chemical messengers and regulatory factors
Autocrine → it activates or inhibits the release of the same cell
Paracrine → it activates or inhibits the release of a different cell
Endocrine → cells that produce products that are released into the blood stream and are going
through the whole body. Every cell with receptors of it will be influenced. → hormones
Neuroendocrine → Chemicals secreted by neurons → neurohormones
Neurotransmission → cells that communicate trough neurotransmitters
Insulin from the B-cells in de islets of Langerhans
- Paracrine: glucagon → in between the A and B cell → glucagon does
the opposite of glucose.
- Endocrine: glucose and fat storage
CCK is released in the gut after a meal
- Paracrine: release of digestive enzymes
- Endocrine: release of insulin by the pancreatic B-cell
- Neural: stimulation of the afferent neurons of the parasympathetic nervous system →
satiation
Pheromones
Signals between organisms. The sharks
let each other know that they are ready
for reproduction.
When the female rat is in the
reproductive phase and get the
pheromones of the male rat the female will get in this position so the ejaculation is easier.
Receptors
, Receptors are things that pick up the signals. Receptors have binding
sites for their ligands, different ligand molecules with similar structures
may be able to bind to the same receptor. One ligand may have multiple
receptors. Different cells may respond differently to a single kind of
signal molecule, the target cell response depends on its receptor or its
associated intracellular pathways, not on the ligand. The degree to which
a protein is attracted to a ligand is called the protein’s affinity for the
ligand. If a protein has a high affinity for a given ligand, the protein is
more likely to bind to that ligand than to a ligand for which the protein
has a lower affinity
When a ligand combines with a receptor, one of two events follows. Either the ligand activates the
receptor and elicits a response, or the ligand occupies the binding site and prevents the receptor
from responding. A competing ligand that binds and elicits a response is known as an agonist of the
primary ligand. Competing ligands that bind and block receptor activity are called antagonists of the
primary ligand.
Peripheral nervous system
The nervous system
- Central nervous system (CNS)
o Brain
o Spinal cord
- Peripheral nervous system (PNS)
o Located outside of the skull and spine
o Serves to bring information into the CNS (afferent) and carry signals out
of the CNS (efferent)
Peripheral nervous system
- Somatic nervous system → skeletal muscles
o Afferent nerves (sensory)
o Efferent nerves (motor)
- Autonomic nervous system → smooth muscle, cardiac
muscle, many glands, and some adipose tissue.
o Sympathetic and parasympathetic
o Both afferent and efferent nerves
The enteric nervous system is a network of neurons in the walls of the
digestive tract. It is frequently controlled by the autonomic division of
the nervous system, but it is also able to function autonomously as its
own integrating center.
Autonomic nervous system
- Innervates those systems that cannot be controlled by the conscious
brain such as heart, smooth muscle, blood vessels, most visceral organs
(liver, pancreas) and all endocrine glands.
- Nervous parasympathetic and sympathetic system
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