This summary contains most of pearson's Human physiology; an integrated approach. It will describe almost every part of physiology that jis needed in the first year of biology. Including a lot of pictures and schematic overviews, it will help you get a good grade.
Physiology
Lecture 1 – 14/10/2024: introduction
Physiology means knowledge of nature
Physiology is the study of the normal functioning of a living organism and its component
parts, including all its chemical and physical processes.
Survival of the individual
1. Stay alive
2. Growth
Survival of the species
3. Reproduction
4. Care
Physiology covers from molecular level to organ level to interactions between organisms and
their environment. This is called the integration of function across many levels of
organization.
All organs work together, and their greater complexity cannot be predicted from knowing the
individual properties, but the emergent properties that are greater than the individual parts
→ integrative physiology
The organ systems
1. Circulatory
2. Digestive
3. Endocrine
4. Immune
5. Integumentary
6. Musculoskeletal
7. Nervous
8. Reproductive
9. Respiratory
10. Urinary
Function tells us why the system or event is happening; we use a teleological approach.
Mechanism tells us how the body accomplishes this; we use translational research.
Perception of a stress stimulus in the brain (visual or auditive etc.) causes activation of the
fight-flight response. It activates areas of the brain involved in the release of energy
substrates and stimulation of the cardiovascular system.
Communication between the brain and body happens through chemical messengers
called neurotransmitters and hormones
,The diving reflex
It is believed to aid in the conservation of oxygen stores during aquatic immersion. If you get
trapped under the ice, the body responds in a way that is opposite of the usual reaction to
stress.
The wetting of nostrils and face which causes bradycardia, apnea, and increased peripheral
vascular resistance. Because you can’t breathe under water, the whole system gets shut
down. In cold water this effect is even larger than in warm water.
Pathological condition: if the body fails to maintain homeostasis. For example, no fight/flight
but a chronical elevated blood pressure. The study of body functions in a diseased state is
known as pathophysiology.
FFA = free fatty acids, buildup of FFA’s happens in a stress situation.
During a stress situation all organs that aren’t necessary are shut down to save
energy. Released glucose and FFA’s are utilized by active muscle.
Homeostasis (homeo- similar, stasis- condition). It
means there is steady state of materials, it does not
mean there is an equilibrium.
Claude Bernard wrote; The constancy of the internal
environment is the condition for a free and
independent life. Walter Cannon was the first to
propose a list of (accurate and complete) variables
that are under homeostatic control. Important is that
the body monitors its internal state and takes action
to correct disruptions.
Feedback mechanisms help to keep the values in an
acceptable range of motion, there needs to be a
setpoint (an optimum value) to get back to.
Negative feedback brings the value back to the setpoint. The
response counteracts the stimulus, shutting off the response
loop.
Response loop: stimulus → sensor → input signal → integrating
center → output signal → target → response
There is also positive feedback. This reinforces the stimulus,
rather than decreasing or removing it.
For example, with delivery when the fetus pushes on cervix
sensors, they send signals to the brain which in its turn
releases oxytocin by the pituitary. The oxytocin causes the
uterus to tract together, therefore increasing the release of
more oxytocin.
,Communication can be
- Autocrine (communication within one cell)
- Paracrine (neighboring cells)
- Endocrine (hormones released that travel to other
target organs that have receptors)
- Neuroendocrine (neurons released by the brain into
the blood)
- Neurotransmission (a neurocrine diffuses from a
neuron to a target cell and has rapid-onset effect)
Local communication
a. Gap junctions
They form direct cytoplasmic connections between
adjacent cells. Cytoplasmic bridges bind the two cells
together.
b. Contact-dependent signals
Require interaction between membrane molecules on two
cells. Cell adhesion molecules (CAMs) are a bridge between
the two cells.
c. Autocrine signals
Act on the same cell that secreted them
Paracrine signals
Are secreted by one cell and diffuse to adjacent cells
Long-distance communication
d. Hormones
They are secreted by endocrine glands or cells into the blood, so they can reach the whole
body. Only target cells with receptors for the hormone will respond to the signal.
e. Neurotransmitters
They are chemicals secreted by neurons that diffuse across a small gap to the target cell.
Neurons are also electrical signals.
f. Neurohormones
They are chemicals released by neurons into the blood for action at distant targets.
Cytokines
They are a different class: peptides for both long-distant and local signaling. They can be
secreted by all nucleated cells in response to stimuli.
Insulin is a hormone produced by the pancreatic islands that travels through the blood, it is
endocrine. In the alpha-cell there is a hormone that releases glucose: glucagon, this is
paracrine.
CCK is released in the gut after a meal. The release of digestive enzyme is a paracrine
process. The release of insulin by the pancreatic B-cell is endocrine. The stimulation of
afferent neurons of the parasympathetic nervous system is neural.
Pheromones are specialized ectohormones that act to elicit a physiological or behavioral
response. They regulate communication between individuals. The vomeronasal organ picks
up the pheromones. Androstenol is a pheromone that attracts females.
, Lecture 2 – 15/10/2024: PNS and cardiovascular
The central nervous system (CNS) consists of the brain and the spinal cord. The peripheral
nervous system (PNS) is everything outside of the brain and spinal cord.
The somatic nervous system
Afferent nerves are sensory nerves and are going
up. Efferent nerves are motor nerves, and these
are going down
Autonomic nervous system
Innervates those systems that cannot be
controlled by the conscious brain. It consists out
of the sympathetic and parasympathetic system,
which are both are efferent nerves. They are
antagonists of each other. The sympathetic system is used when the body is activated, the
fight/flight mode. The parasympathetic is the rest and digest mode and is used when the
body is at rest. Homeostasis is a dynamic balance between the autonomic branches.
Assimilators store energy and dissimilators release energy.
The parasympathetic and sympathetic system both have a different influence on every organ.
The parasympathetic system has 95% origin in the brainstem, where the sympathetic system
has origin in ganglions in the spinal cord.
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