Summary Human physiology including IP animations needed for the course from the online environment of the book. Covers all content for biology students of the RUG. It is also part of the course 'Anatomy & Physiology' for biomedical engineering students of the new cohord (see also anatomy summary on...
Integrative physiology
Requirement of survival.
- Survival of the individual
o Stay alive
o Growth
- Survival of the species
3. Reproduction
4. Care
Physiological mechanisms follow this rule.
Physiology studies the functioning of the body on different levels:
- Molecular (intracellular) level.
- Organ level.
- Interactions between organisms and the environment.
Physiology studies the functioning of the body: integrative physiology, homeostasis (feedback
mechanisms) and (patho)physiology.
Integrative physiology
The perception (=waarneming) of the stress stimulus in the brain (in the visual & auditive parts etc.)
leads to activation of the fight-flight response. The activation of the brain areas involved involved in
the release of energy substrates and the cardiovascular system gets stimulated. There is
communication between brain and body through chemical messengers: neurotransmitters and
hormones.
So when there is a signal of e.g. danger, this signal goes to the brain signal goes to the adrenal (on
kidney) adrenalin comes free from the adrenal adrenaline activates the sympathetic nervous
system, so the blood gets circulated faster (higher blood pressure), the heart frequency goes up /
other processes get activated in the body: pancreas reduces insulin syntheses and the liver releases
glucose, the white adipose tissue releases fatty acids there is an increased availability of energy
substrates and there are changes in blood distribution. These processes cost energy the hormone
ATCH & cortisol get released organs and processes which are not important/ are irrelevant at that
moment get shut off. E.g. the gut and the immune system (less energy used for these organs).
Fight flight when it is needed: released glucose and free fatty acids are utilized by the active muscle.
Stress (patho)physiology
Fight flight gets activated, but it is not needed to ‘fight or flight’ (stress etc.): pathological condition.
There is still glucose released, but it doesn’t get used. This leads to problems. A pathological
condition is when you get sick or something in pathology goes wrong.
When there is no fight flight and this happens more constantly, your blood pressure rises and there
will be storage of fat in the endothelium (inside of blood vessel). Also the immune system will get
shut off.
Homeostasis
Homeostasis: the stability of the body’s internal environment. Everything has a setpoint. E.g. your
blood pressure has a setpoint. This is a favourable situation. The body will always try to get back to
this setpoint when there are changes. The body does this by getting feedback from receptors e.g.
There are systems that react to this feedback to protect the homeostasis. When the organism
attempts to compensate, it can succeed or fail. If it fails, it leads to illness or a disease pathology.
So when the change results in loss of homeostasis there happens either compensation or pathology.
A system that protects homeostasis is negative feedback for example.
- Negative feedback: the response counteracts (=tegenwerken) the stimulus by shutting of the
response loop. So there is a stimulus, e.g. the water temperature is below setpoint, which
, stimulates a response to go back to homeostasis/setpoint. The response loop turns ons. With
negative feedback the signal gets removed ones the water has reached the upper limit of
acceptable change. The response loop shuts off, so the water will cool down.
Negative feedback loop: Stimulus (the water is below setpoint) sensor (senses the
temperature decrease)integrating centre (responds to a temperature below a certain
level) effector (tries to compensate the temperature) response (the water temperature
increases and turns back to setpoint). When it has reached setpoint, will stay rising, so the
negative feedback stops the response loop that ‘says’ the water temperature is too low.
- Positive feedback: the response reinforces the stimulus rather than decreasing or removing
it. It is not homeostatic the response sends the regulated variable even farther from its
normal value. For example, child birth. Baby puts pressure on the cervix hormone oxytocin
gets released uterus contracts baby’s head puts more pressure on cervix more oxytocin
released by the brain continues until baby gets born.
Homeostasis has circadian rhytm: regulated variables that change predictably and create repeating
patterns or cycles of change. E.g. body temperature peaks in the late afternoon and declines
dramatically in the early hours of the morning.
Glucose homeostasis:
eatingblood glucose islets of langerhans insulin cellular uptake of glucose blood
glucose----negative feedback loop--- (stops secretion of insulin).
With integrative physiology and homeostasis the bodily functions are integrated. This requires
communication. Ways of communication are the nervous system, blood, lymph, air, water.
Communication tools are neurotransmitters, hormones and pheromonen etc.
Communication: chemical messengers and regulatory factors.
- Autocrine: cell gives feedback to itself.
- Paracrine: cell releases activators for the cells next to it.
- Endocrine: cell signals through blood (by hormones) to other cells.
- Neurotransmission: neuron activates the neuron next to it.
- Neuroendocrine: neuron releases through blood a signal to a cell.
Signals between cells:
Gap junctions: form direct cytoplasmic connection between adjacent (=aangrenzend) cells.
Contact-dependent signals require interaction between membrane molecules (like receptors)
on two cells.
Autocrine signals: act on the same cell that secreted them.
Paracrine signals: are secreted by one cell and diffuse to adjacent cells.
Communication tools:
- Hormones: are secreted by endocrine glands or cells into the blood. Only target cells with
receptors for the hormone will respond to the signal
- Neurotransmitters: are chemicals secreted by neurons that diffuse across a small gap to the
target cell. Neurons use electrical signals as well.
- Neurohormones: are chemicals released by neurons into the blood for action at distant
targets (neuroendocrine).
Example: insulin from the B-cells (=insulin producing cell) in the islets of Langerhans. Insulin has an
endocrine function. Glucose and fat storage happens through an endocrine way. Insulin also
activates its neighbour cells, the A-cells, which produce glucagon (antagonist of insulin). This happens
paracrine. Insulin has an endocrine and paracrine function.
This is also the case with CCK in the gut. It gets released after a meal by the gut and it activates all
kinds of digestive enzymes (paracrine). As soon as there is food it needs to be stored and CCK
activates insulin (endocrine). Insulin gets released by the pancreatic B-cell. There are also neural
connections with CCK. The stimulation of the afferent neurons from the parasympathic nervous
system get activated by neurons. The neurons signal ‘there is food in the gut’ (satiation).
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