General physiology
-
Upload
medicalphysiologyajims -
Category
Technology
-
view
1.920 -
download
0
Transcript of General physiology
GENERAL PHYSIOLOGY
Dr. Pavithran.PAssistant Professor in PhysiologyA J Institute of Medical Sciences, Mangalore
2
What is PhysiologyPhysiology is the study of
life, specifically, how cells, tissues, and organisms function.
Pronounced “fizzy-aw-low-jee”
3
Q: Why do we shiver, when we feel cold?
A. To help us warm up, as shivering
increases body temp
How does this happen – not answeredWhat is the cause – not answeredWhat will be its effect - answered
4
Temperature sensitive nerve cells detects fall in
temperatureImpulses transmitted to
brain Hypothalamus
Brain areas gets activated
Involuntary, oscillating muscle contraction
(Shivering)
Increases body temperature
5
INTERNAL ENVIRONMENT&
HOMEOSTASIS
6
External environment –
surrounding environment.
Amoeba- Unicellular Organism
Takes nutrients and expels waste –
external environment
7
Cells in human body – all does not
have contact with external
environment.
How do they support their vital
activities?
Extra cellular fluid-the internal
environment.
8
Majority inside the cells –
intracellular fluid (ICF).
1/3rd – out side the cells-
Extracellular fluid (ECF).
ECF contains ions and nutrients
ECF – internal environment for the
cells – Milieu Intérieur
9
(1813-1878)
Milieu Interieur
Milieu- Environment
Interieur – Internal
19th French Physiologist.
Concept of the internal
environment of an
organism.
Blood- as the internal
environment.
10
11
Homeostasis:Homeo: same; stasis: stayThe word does not imply something set and immobile, a stagnation. It means a condition — a condition which may vary, but which is relatively constantWalter Cannon
Homeostasis: maintenance of a constant internal environment. An extension of Claude Bernard idea
(1871–1945)
12
13
Homeostatic mechanismThree part mechanism
1. Receptor
2. Control center
3. Effector
14
15
The internal state of the body - dynamic
equilibrium (balanced change).
There is a certain set point or average
value for a given variable (such as 37°C for
body temperature).
Conditions fluctuate slightly around this
point.
16
Regulatory Mechanism
18
Negative feedback mechanismPositive feedback mechanisms
Feedforward mechanism
NEGATIVE FEEDBACK MECHANISM
20
Most of the control mechanisms in human
body
The body senses an internal change and
activates mechanisms that reverse, or
negate, that change.
Arterial blood pressure regulation
Increase in BP is detected by various
mechanism that lead to a decrease in BP
21
• Increase in Co2 – increases
ventilation- decreases Co2
22
•B
OD
Y T
EM
PER
ATU
RE R
EG
ULATIO
N
POSITIVE FEEDBACK MECHANISM
24
A process in which the body senses a change and activates mechanisms that accelerate or increase that change.
Child birth (Parturition reflex)◦Uterine contractions due to Oxytocin◦Baby’s head pushes against the cervix -
stretch◦Sends impulse to the uterus◦Stimulates further contractions of the
uterus◦Pushing the baby out.
Milk ejection reflex
25
FEEDFORWARD MECHANISM
27
Body responds in anticipation of a change in
regulated variable.
In GIT- insulin secretion is increased
Insulin increases cellular uptake and storage of
ingested nutrients after they are absorbed.
This limits the rise in blood sugar/nutrients
after absorption
28
Disruption
System malfunction
Homeostasis not maintained
Pathophysiology
Severe - death