Homeostasis Flashcards
1
Q
What is homeostasis?
A
The ability to maintain a constant internal environemnt or “steady state” in response to external and internal environmental changes
2
Q
What is a tolerence limit?
A
The upper and lower limits to environemental factors that an organism can survive within
3
Q
What are 4 tolerence limit factors?
A
- Body temp
- water availability
- Blood glucose levels
- CO2 concentration
4
Q
Tissue fluids
A
- surrounds all body cells
- stays constant and allows cells to continue their functions
5
Q
Communication
A
- communication is found between (organs/systems) nerves and hormones
- achieves stability and helps organism detect and respond to changes in internal and external environment
6
Q
2 examples of organisms responding to change
A
- solute amd water balance in plants by active transport through roots and closing pores of stomata
- bacteria forming “spores” in response to lack of water
7
Q
describe the stimulus response model (6 parts) and give an example
A
- Stimulus: a variable/change in the internal or external environment environment that is detected by organism
- Receptor: cells/tissue detects the change
- transmission of Message: relay of info by nerves and/or hormones
- Effector: gland/muscle that brings response after recieiving info
- Response: action occured due to initial stimulus
- Feedback: impact of stimulus (+ or -)
Example: Stimulus = thirst, receptor = eyeball sees water, message = sends through sensory neuron -> relay neuron (in brain) -> motor neuron, effector = picking up glass, response = drinking water, feedback = not thirsty
8
Q
What are sensory receptors?Why are they important?
A
- detect stimuli and respond
- without sensory receptors, then changes can not be identified
- factors impacting organism can be abiotic and biotic
9
Q
What is the negative feedback model?
A
- if a change is triggered, a negative feedback response counteracts/reverses initial fluctuation
- inhibits initial stimulus
e.g., temp
10
Q
What is the positive feedback model?
A
- a response that amplifies rather than reverses initial fluctuation
e.g., child birth - oxytocin to speed up contractions
11
Q
What do sensory receptors do?
A
respond to intensity, duration and location of stimulus. Once stimulated, they send nerve impulse to CNS. CNS sends nerve impulse along nerve cells (motor neurons) signalling effector, such as muscle cells or glands to respond
12
Q
what is the role of the nervous system and what is it made up of?
A
- to detect stimuli, process info, and elicit a response
- is divided into the central nervous system and peripheral nervous system
- short term, short lasting, fast
13
Q
What is the CNS?
A
- Consists of the brain and spinal cord
- detects internal changes in the brain, recive stimuli from peripheral nerves, process info and send nerve impulses to relevent tissues and rgans to bring about response
14
Q
What is the PNS?
A
- Consists of nerves that lie outside of the brain and spinal cord
- connects CNS to all parts of the body
- Contains voluntary nerves ( automatic nervous system) and involuntary nerves (somatic nervous system)
15
Q
What is a neuron? What are the 3 types?
A
- nerve cells that sends and recieves messages.
1. Sensory neuron
2. interneuron
3. motor neuron
16
Q
what is a sensory neuron?
A
- detetcs stimuli by receptror and carries nerve impulses along sensory neurons towards interneurons in the CNS
- sensory organs -> CNS
- unipolar (one process)
17
Q
what is an interneuron?
A
- located in brain and spinal cord
- recieve signal from sensory neurons and transmit them to motor neurons
- CNS -> PNS
- multipolar (many processes)
- nerve impulse travals from dendrites along axon to axon terminals
18
Q
What is a motor neuron
A
- carry nerve impulses from CNS to effectors (muscles and glands) via PNS, resulting in response
- multipolar (many processes)
- nerve impulse travels from dendrites, along axon to axon terminals
19
Q
Describe the structure of a nerve pathway from receptor to effector
A
- receptor detects a stimulus that triggers a nerve impulse
- this travals along a sensory neuron towards spinal cord in CNS
- impulse is transmitted along nerve fibres (axons) in the spinal cord and brain
- this sends a nerve impulse down spinal cord along motor neuron
- motor neuron carries impulse to an effector (muscle or gland)
- this results in a response
20
Q
Describe the role of the synapses and neurotransmitters
A
- junction called a synapse with a gap caled a synaptic clef between the axon of one neuron and the dendrite of the next
- Transmission across the gap is by a chemmical called a neurotransmitter that is secreted from the axon terminal of the incoming neuron
-neuromuscular junciton is where the nerve reaches a muscle cell - following secretion. neurotransimitters are either destroeyd by enzyme, diffuse away, or are absorbed by cell
21
Q
What happens if neurotransmitters stay in the synaptic cleft?
A
- if a neurotransmiiter remaines in the synaptic cleft, there would be continual stimulation of the next neuron in the pathway or effector
22
Q
What is the role and pathway of reflex response?
A
- automatic response
- bypass brain and goes: sensory neuron -> spinal cord -> interneuron -> motor neuron -> effector -> response
- protects organism by provding rapid response
e.g., removing hand from flame
23
Q
What is the endocrine system? what does it do?
A
- glands and organs that make hormones and secrete them directly into the blood to target several organs and tissues
releases hormones that are peptides, proteins or steroids - hormones can alter the matabolism of target cells, tissues and organs
- long lasting, long term, slow
24
Q
What are target cells?
A
- specalised cells on which hormones act
- membrane consists of specific protein recpetor molecules
- receptors detects presence of hormones outside of cell and carry message across cell trhough enzyme reactions]- hromones procude an effect when it reaches the target cell that they are tuned into
25
Describe the role of thyroid-stimulating hormone in the production of thyroxine.
The hypothalamus releases thyroid-relasing (TRH) hormone which causes the anterior pituitaory to secrete thyroid stimulating hormone (TSH). This in turn triggers the production and release of thyroxine by the thyroid gland. An increase in the level of thyroxine in the blood inhibits the hormones from the hypothlamus and the pituitary. Plays a role in temp control
26
Describe the action of thyroid stimulating hormone and thyroxine in metabolism
the regulatory rol eof the anterior pituitary is the release of thyroid stimulating hormone (TSH). TSH acts on the thyroid gland, causing it to release thyroxine which signals cells to increase their metabolic pridctuin rate and this increases body temp
27
Hormones can be either...
Steroids: lipid soluble and pas through cell and nucelar membranes - effecting receptor molecules within cell
Protein: cant pass through membranes, bind with protein recpetors on cell membrane
28
Describe the role of adrenaline in the ‘fight or flight’ response.
- sends message via sympathetic nervous system to adrenal glands to secrete adrenaline
- heart rate and cardiac output are increased, rasing blood pressure and flow
- smoth muscles around bronchi relax, increasing air flow to lungs so more oxygen is absorbed
-pancreas is stimulated by adrenaline ti increase glucagon secretion which initiates release of glucose from the liver into the blood
- increase of blood flow, oxygen and glucose level result in increase cell metabolism
- radical muscle movemebts of iris result in pupil dilation
- brain is put at heightened
29
Compare the action of the nervous and endocrine system
Nervous:
- pathway: direct
- message: electro-chemical impulse
- site of action; highly specific
- speed: fast
- duration: short term
Hormonal:
- pathway: indirect via blood
- message: chemical
- site of action: target cells can be widespread
- Speed: slow
- Duration: long term
30
What is the pituatry gland
- the secretion of hormones by endocrine glands is controlled by th secretion of other hormones by the pituitary gland (master gland)
- controlled by hypothalamus
- anterior and posterior pituaitory
31
What is ADH?
- is synthesied in the hypothalamus and stored in the posterior pituitary.
- Is secreted by the pituitary in response to an increase concetration of solutes in the blood
- ADH is releasesed into blood abd binds to receptro moleucles on cells of collecting ducts in the kidneys
- makes collecting duct wall s more permable and increase aquaporins to increase water reabsorbtion and thus reduce urine output and reduces concentraiton of solutes
32
What is metabolism?
- the sum of reactions occuring at any given time
- each reaction occurs in many intermediate steps - each step gives off small amounts of energy as heat
33
How is the blood temp controlled?
Fall and rise:
- body temp is monitored by the thermoregulatory centre in the hypothalamus of the brain
Fall:
A. thermoregulatory centre sends nerve message to the skeletal muscle to repeatedly relax and contract. This shivering requires the muscles to repire and heat is generated
B. send nerv messages to sphincter muscles around arterioles in the skin. The response is constriction of blodd vessals (vasoconstrction). This decreases blood flow of blood to the surface of the body, directing the blood flow mainly to essential core organs
C. release hormones via the pituitary that stimulates the thyroid gland to secrete the hormone thyrxine, This, in turn, stimulates general cell metabolism and causes an increase in temp
Rise:
A. thermerogulatroy centre sends nerves impulses to the sweat glands causing htme to secrete sweat onto the bodys surface. Evaporation of the sweat removes heat from the skin
B. send fewer nerve messages to the sphicnter muscles of the arterioles, casuing htme to relax. This is called vasodilation and it increases blood flow to the surface of the skin, increasing the rate of heat loss from the body
C. decrease the secretion of horomones to the thyroid. The thyroid lowers the amount of thyroxine releasd ans so cell metabolism decreases
34
How is osmoregulation enabled?
Rise and fall
- refers to mainteance of water and solute balance in the body
- kidney is the main organ involved
Rise:
too much water - hypothalamus detetcs toom uch water in blood - pituitary gland releases less ADH - kidney reduces blood watr level - more water reaches bladder (urine more dilute) - water content of blood is normal
Fall:
too little water- hypothalamus detects too little water - pituaitry gland releases ADH - kidney maintains blood water levels - less water is lost in urine (urine more concentrated)
35
process of maintainging BSL
Rise:
Beta cells of pancreas release insulin in blood -> insulin then gets liver to convert glucose glycogon or put away into tissue cells -> decreases BSL
Fall:
Alpha cells of pancrease stimulate release if glucagon into blood -> glucagon then binds to glucagon recptros on liver cells causing cells to convert glycogon to glucose into the blood -> increases BSL
36
Regulate CO2 in blood
- Aurobic respiration produces CO2
-CO2 reacts with water to from carbonic acid
-carbonic acid increas hydrocarbonate ions and hydrogen ions -. into blood
- the increases hydrogen ions lowers pH of blood
e.g.,
- decrease in pH9 due to increased level of carbon diosxide) results in more nerve impulses from brain to spiroty uscles -> increases breathing rate
-lower CO@ concnetraiton in blood and increase pH
- increase in pH detected in respitory centre results in fewer nerve impulses to the chest adn dipahram -> results in decreased breathing rate
37
Compare the action of insulin and glucagon in blood sugar regulation
Insulin stimulates the liver to pack glucose into glycogon or store in tissue cells - reduces BSL
Glucagon stimulates the breaking down of glycagon and release of glucose into the blood - increase BSL
38
Describe how diabetes can result from a hormonal imbalance
- refers to the inibility to maintain BSL in normal range
- in type 1: inbility to prodce insulin due to auto-immune disease that destorys insulin-producing cells of the pancreaase. Also unable to produce glucagon.
- in type 2: results from body becoming resistant to insulin and/or being unable to make anough insulin
39
Discuss links between osmoregulation, blood volume, and blood pressure
ADH regulates water and solute balance, adn this affects blood volume and blood pressure. Osmotic pressure in th eblood and tissue fluid is determines by the water and solute balance. Somoregulation involves controlling the relative concnetrations.
An increase in the water content of the blood will increase the volume of the blood and resulin in an increase in blood pressure.
A decrease in water content of the blood will decrease the volume of blood and result in an increase in a decrease in blood pressure.
Increasing the water content of the blood will decrease its solute concentration, and decreasing the water content od the blood will increase its solute concentration
40
Filtration
1. blood traval to nephrons through small arteries (afferent arteriole)
2. blood from different arteriole enters glomerulus
3. Fluid (filtrate) is passively filtered out into bowemans capsule
3. rate of filtration is determined by blood pressure
41
Nephron process
Bowmans: iltrate contains water, salts, glucose, urea, vit and AA - proteins, W or R BC stay in capillery as they are too large - small molecules are reabsorbe into cpappileries surrounding tubule of nephrons - tubules lined with microfillus to increase SA/V ratio
Proximal convulated tubule: close to bowemans capsule - reabsorbes salts, glcose and AA into capillaries via diffusiona nd AT - water reabsorbed via osmosis
Descending loopvof henle:
reabsorotipn of water via osmosis - filtarte becomes more concetrted with leftever salt
ascending loop of henle: reabsopriton of salt in capillaires
Distal convulated tubule: distant to bowmans capsule - regulates pH of blood
Collecting duct: remaining unwanted waste (urea) is collected - drains into bladdefr rvia urea to wait excretion via bladder
42
what influences rate of reabsorption?
- influenced by hormone ADH
- ADH controls reabsorption of water (presence allows tubules to be permable)
-alcaholdecreases prodctuon of ADH -> more urine -> water not absorbed -> leads to dehydration
43
What is a nephron?
-regulates composition of blood concnetration through combination of filtration and reabsorption to transfer materials between renal tubukes and capillaires
- are the structioral and functional region of the kidneys
