Homeostasis, Nervous system Flashcards
What is homeostasis?
The dynamic constancy of the internal environment despite constant changes in the external environment.
Set point
The optimum value that you want to maintain
Controlled variable
The aspect you want to maintain
What is the feedback mechanism
Detect change in sensor cells/receptors. Signal to integrating centre. Signal back in response to an effector. Action to change the variable. Change is detected and feed back.
What is negative feedback
Where deviation away from the set point value causes a return to the optimum.
What is positive feedback?
Where deviation away from the set point value causes a further deviation.
What is the process when the blood pressure changes?
1) Baroreceptor found in Carotid artery and aorta.
2) Signals through Glossopharyngeal nerve to Medulla oblongata
3) Impulses back through the autonomic nerve system
4) Vasoconstriction or vasodilution
What is the process when the temperature changes.
1) Thermorecpetors in skin and in hypothalamus.
2) Integrator- Hypothalamus activates effectors
3) Effectors for warming up occur
Give examples of effectors for warming up
Pili muscles contract so hair can rise, vasoconstriction and skeletal muscle contacts (shivering).
Give examples of positive feedbacks
Action potential in nerves, ovulation, in birth labour, lactation (baby milk) and blood clotting.
How does positive feedback end?
It can be self-terminating E.g baby stops suckling, baby is born. Or other feedback loops can activate them to shut them down.
Peripheral Nervous system
Composed of the somatic and autonomic nerves (voluntary and involuntary)
CNS
Is composed of the Brain and the spinal cord. (The body’s master control unit)
What sets of neurones are found in the Autonomic system?
Preganglionic neurons and postganglionic neurons.
Where is the preganglionic neurons found?
Starting from the spinal cord.
Where is the postganglionic neurons found?
Outside the CNS, after passing the ganglion. (2nd part, like motor neurone)
What is a ganglion?
A nerve cluster or group of nerve cell bodies located in the autonomic nervous system and sensory system.
What is Autonomic Nervous System?
Involuntary bodily processes.
What is the Sympathetic system?
Part of the Autonomic nervous system. When stressed and release adrenaline/ epinephrine. Makes an excitatory reaction. Speeds up
What is Parasympathetic system
In the Autonomic NS, more active in calm states and slow things down.
Give the order in which the vertebrae is ordered top to bottom: lumbar, sacral, cervical, thoracic.
Cervical, thoracic, lumbar, sacral, coccygeal.
What is cranial neurons?
Nerves coming out of the brain and brain stem
What are peripheral neurons?
Nerves coming out of the spinal cord (cervical to coccygeal).
Where does the sympathetic neurons outflow from?
Come out from the Thoracic and Lumbar in the vertebrae.
Where does the parasympathetic outflow from
From the cranial (brain) and sacral.
What length is the preganglionic fibre in para and sympa
Sympa= Short Para = long
What neurotransmitter is released in the ganglion in para and sympa?
Acetylcholine
What is a neuroeffector transmitter?
A transmitter that acts on the effector and gets released from a motor neurone.
What neuroeffector transmitter does sympa and para have?
Sympa secrete Noradrenaline (alpha or Beta). Para secrete acetlycholine.
What does Noradrenaline do?
Increases the heart rate and sweat and decreases digestion, vasoconstriction.
What does acetylcholine do?
Decreases the heart rate and sweat. Increases digestion and vasodilation.
What is the endocrine system?
The hormone system
What are steroids?
A hormone that is made of lipids. So it can pass through the membrane and bind to receptors in the nucleus to change gene expression
What can hormones be made of?
Protein or lipids (steroid)
What is Cortisol?
A steroid hormone that is released when stressed and controls the glucose blood levels.
How is cortisol released?
CRH is released and this causes ACTH to be released. Then cortisol is released. An increase in cortisol results in decrease in CRH secretion. NEGATIVE FEEDBACK
Give an example of a Positive feedback?
1) Baby suckles at the mother nipple.
2) Signals go to the brain
3) Oxytocin is released into the blood
4) Oxytocin contracts the ducts in the breasts, increasing pressure and releasing milk
5) The more suckling, the more oxytocin is released.
6) No suckling stops further secretion of oxytocin.
Give the equation linking pH and H+ ions?
pH= -log10 [H+] [H+] = 10^-pH
What is the pH buffer system
CO2 + H20 = H2CO3 = H+ + HCO3-
