Physiology Flashcards
Where are baroreceptors located?
Aortic arch
Carotid sinus
Process of baroreceptor activation?
- Sensitive to stretch
- Firing rate increases when MAP increases (decreases/STOP when MAP decreases)
What happens to baroreceptor firing if high blood pressure is sustained?
Firing decreases/STOP
They only respond to acute changes
Definition of blood pressure?
The outwards (hydrostatic) pressure exerted by the blood on blood vessel walls
Systolic pressure?
When the heart is contracting (normally <140mmHg)
Diastolic pressure?
When the heart is relaxed (normally <90mmHg)
MAP?
The average arterial blood pressure during a** single** cardiac cycle
What is the average MAP range?
70-105mmHg
MAP equations when you have diastolic and systolic?
MAP = [(2x diastolic) + systolic]/3
MAP = Diastolic + (pulse pressure/3)
MAP = DBP + 1/3 difference between SBP/DBP
MAP= [2x diastolic blood pressure (DBP)] + systolic blood pressure (SBP) /3
e.g if BP = 120/70 mmHg
DBP=70
SBP= 120
MAP equations?
MAP = Cardiac output (CO) x Total peripheral Resistance (TPR)
MAP = Diastolic + (pulse pressure/3)
CO equation?
CO = stroke volume (SV) x Heart rate (HR)
How can MAP be regulated?
By regulating
-HR
-SV
-TPR
Which vessels control resistance?
Arterioles
thus main site of systemic vscular reistnace becasue they distrubute blood into the capillary bed (smaller dimeters and so blood is sequeed more into the vessles )
Tissue?
Group of cells with similar structure and specialized function
General idea of how homeostasis works?
-Sense deviations from normal
-Integrate this information
-Make appropriate adjustments to restore controlled variable to a desired variable
Intrinsic controls?
**Local controls inherent in an organ.
**
e.g organ is capable of maintaining homeostasis within itself. For example, the heart can control its own heart rate.
Extrinsic controls?
Regulatory mechanisms initiated outside an organ
Accomplished by nervous and endocrine systems.
e.g controls of the cardiovascular system include neuronal, humoral, reflex, and chemical regulatory mechanisms
Feedforward?
Responses made in anticipation of change
Feedback?
A
Responses made after a change has occurred
What does positive feedback do?
Amplifies a change
What temperature is the body homeostatically maintained at?
37.8 celcius
What does having normothermia optimise?
Cellular metabolism
Cellular function
What is the term used to describe normal body temperature?
Normothermia نورموثيرميا
What can cause variations in body temperature?
Natural differences between individuals
Time of day (lower in mornings)
Physical activity or emotions
Exposure to extremes of temperature
Menstrual cycle
In which two ways can the body gain heat?
- Metabolic heat
2.Radiation from external environment
How can the body lose heat?
Convection
Conduction
Radiation
Evaporation
Which hormones can increase heat production and why?
Adrenaline, noradrenaline and thyroxine
These hormones can speed up metabolic rate, so more heat is produced
Besides hormonal/metabolic control, what is one mechanism utilised by the body to increase body temperature?
Shivering
(increases muscular activity)
The level of heat conduction is dependent on which two factors?
A
1. The temperature gradient
2. Thermal conductivity
Why does evaporation result in heat loss?
Energy require to convert water on the skin to vapor.
What are the two types of evaporation?
- Passive - this happens continuously, water molecules diffuse from bodility surfaces
- Active - the sympathetic nervous system is employed to increase sweating
Where can thermoreceptors be located?
- Central - hypothalamus, abdominal organs, other locations
- Peripheral locations - skin
Where is the control centre for body temperature located?
Hypothalamus
What are the effectors used by the body to control temperature?
Skeletal muscle (shivering)
Skin arterioles (dilatation/constriction)
Sweat glands
The posterior hypothalamus is activated by ______, whilst the anterior is activated by ______.
Cold
Warmth
When activated, what will the posterior hypothalamus cause?
- Vasoconstriction
- Increased muscle tone
-Shivering - Behavioural changes - voluntary movement/clothing changes
How is fever brought about?
A
Macrophages release pro-inflammatory mediators which act as endogenous pyrogens
They stimulate prostaglandin release which causes the hypothalamus to raise the baseline body temperature that is maintained
Shivering and vasoconstriction will be initiated by hypothalamus to raise body temperature
Why is it called when the body temperature exceeds 40 degrees?
Hyperthermia
What is hypothermia?
When the core body temperature decreases below 35 degrees
What is homeostasis?
the maintenance of steady states within our bodies by coordinated physiological mechanisms.
- in internal envirmonet
Active evaporation is called?
Sweating - controlled by sympathetic nervous system
What is the hypothalamus?
Small area in the brain
Body’s thermostat
what is the feature of Negative feedback control ?
Promotes stability by regulation of a controlled variable through the flow of information along a closed loop.
- happen oppose an initial change
system which amplyfie intial chnage is known as ?
Postive feedback
Feedforward
responses made in anticipation of a change
when will Thermostat reset to normal ?
if pyrogen release reduced/stopped
What effect does ATP hydrolysis have on the sodium potassium pump?
The ADP is released but the phosphate group phosphorylates the pump. causing Na+ to move outside the cell against the concentration gradient
ANP -
BNP -
- released in response to atrial distension.
- important for heart failure diagnosis.
ADH
Secretion stimulated by - reduced extracellular fluid volume or increased extracellular fluid osmolality. ADH acts in the kidney tubules to increase the reabsorption of water ie concentrate urine (anti-diuresis). ADH also acts on blood vessels to cause vasoconstriction.
Basal Metabolic Rate.(BMR)
is the minimum amount of energy required to sustain vital body function and lead to basic level of heat production
the steps of haemostasis
1) Constriction of the blood vessel
2) Formation of a platelet plug
3) Activation of the coagulation cascade
4) Formation of a fibrin plug
E. Pinocytosis
Pinocytosis is the internalisation of fluids (and particles contained within) into cells through invagination of the cell membrane.
