Homeostasis Flashcards
What is a tolerance limit?
a limit of conditions in which an organism can effectively operate within, the survival of an organism can be threatened when these conditions fluctuate from tolerance limits
Name 4 factors for which organisms have tolerance limits.
Body temperature, water availability, carbon dioxide/pH levels in the brain, and blood sugar levels
How do organisms detect changes in the internal and external environment?
Via sensory receptors
What is the purpose of homeostasis?
To maintain a stable internal and external environment, enabling the survival of an organism
Compare the structure and function of sensory neurons, interneurons and motor neurons
Sensory neurons are unipolar, have cell body half way down its axon. Axon synapses with interneuron to transmit message to CNS, transmits signal from sensory receptors. only found in PNS
Interneurons are usually multipolar. Dendrite synapses with sensory neurons. Axon synapses with interneurons or motor neurons, transmitting signal.Only found in the CNS.
Motor neurons are usually multipolar. dendrite synapses with interneuron, axon synapses with effector, enabling a response to be carried out. only found in PNS
What 2 structures make up the central nervous system (CNS)? What types of neurons are in the CNS?
Brain and spinal cord
Interneurons
Describe the structure of a nerve pathway from receptor to effector
Receptor – sensory neuron – interneuron/s – motor neuron – effector
Receptor detects a stimulus, transmitting a nerve impulse that travels along the sensory neuron to the Central Nervous System (CNS). The nerve impulse is transmitted to the spinal cord to the brain, the brain processes the information (stores or relates to pre-existing information), the brain sends back down the spinal cord to a motor neuron, motor neuron transmits message to effector, leading to a response being carried out
Describe the role of a synapse
- It is a junction between neurons
- Specific, target method of controlling nerve transmission that can be inhibited
Where are neurotransmitters stored in a neuron?
vesicles
- How are neurotransmitters release from a neuron?
Exocytosis
What causes neurotransmitter release?
nerve impulse
How do neurotransmitters move across the synapse?
Diffusion
How do neurotransmitters create a signal in the post-synaptic neuron?
Nerve impulse stimulates vesicles containing neurotransmitters to migrate to the cell membrane (of pre-synaptic neuron) and neurotransmitters are released into the synaptic space
neurotransmitters move across the synaptic space via diffusion and bind to complementary receptors on post-synaptic neuron, this transmits the information, thus resulting in a nerve impulse/signal generation
What happens to neurotransmitters after the signal is sent in the post-synaptic membrane?
Released from receptors, re-uptake into pre-synaptic neuron via transporters
How can medications/drugs interfere with the transmission of signals to post-synaptic neuron via neurotransmitters?
Inhibit transporters, block receptors, prevent exocytosis
Why are reflex responses important?
For self-preservation – ensure the safety of an individual
- What is the pathway of a reflex response? and State how this response is fast and automatic.
- ## Sensory receptor – sensory neuron – interneuron – motor neuron – effector
- Fast: via nerves to the nearest part of the CNS
- Automatic: direct connection to one interneuron between sensory and motor neuron
Name 4 things that a hormone can be made of.
Amino acid derivatives, steroids, proteins, peptides
How are hormones transported around the body?
Via the bloodstream
State 2 things that can stimulate a hormonal response?
Nervous stimulation e.g., fight or flight response
Hormonal stimulation e.g., TSH stimulates thyroxine release
Describe the role of adrenaline in the flight or fight response
When an organism detects danger, the brain transmits a nerve impulse, via a motor neuron, to the adrenal gland, the adrenal gland secretes adrenaline, which is responsible for increasing breathing and heart rate, and blood flow to the brain and limbs, and for accessing energy stores via glucose within seconds
- What organ secretes adrenaline?
Adrenal gland
What stimulates adrenaline release?
Nervous signal from brain
Describe 3 or more effects of adrenaline on body functions
Increase breathing rate, increase heart rate, increase blood flow
What gland secretes TSH?
Pituitary gland
Where are the receptors of TSH?
Thyroid gland
What hormone is released when TSH binds to receptors?
Thyroxine (T4)
Where are the receptors for thyroxine?
All cells in the body
What is the effect of thyroxine on the body?
Increase metabolic rate
Describe the action of thyroid stimulating hormone and thyroxine in metabolism.
- hypothalamus in the brain releases thyroid-releasing hormone (TRH)
- TRH stimulates pituitary gland in the brain to release thyroid stimulating hormone (TSH)
- TSH binds to complementary receptors on the cell membrane of thyroid gland, stimulating the steroid to secrete thyroxine
- Thyroxine binds to complementary receptors on body cells, transmitting cell signal to increase metabolic rate
Describe the action of insulin in blood sugar regulation.
Release from:
Transported in:
Target cells:
Action:
Outcome:
Release from: Beta cells in pancreas
Transported in: Blood
Target cells: fat, muscle and liver cells
Action: Binds to complementary receptors on liver cells, transmitting cell signal to open glucose protein channels, (glucose is converted into glycogen for storage), initiates fat and muscles cells to uptake glucose
Outcome: Decreased blood sugar levels
Describe the action of glucagon in blood sugar regulation.
Release from:
Transported in:
Target cells:
Action:
Outcome:
Release from: Alpha cells in pancreas
Transported in: Blood
Target cells: Liver cells
Action:Binds to complementary receptors on liver cells, transmitting cell signalling to open glucose channels (glucose is converted into glycogen), initiating the release of glucose into the blood stream
Outcome: Increased blood sugar level
Describe how diabetes melitus can result from a hormonal imbalance.
If insulin is not produced or cannot function properly
Cell signal cannot be transmitted to open glucose protein channels therefore, individual will have constant high blood sugar levels – this is diabetes
Describe the effect of antidiuretic hormone (ADH) on the nephron in osmoregulation.
Anti Diuretic hormone (ADH) binds to complementary receptors on nephron tubule, transmitting cell signalling to open aquaporins, this increases the permeability of the nephron tubule
This results in more water reabsorption into the blood stream, there will be less water content in urine, hence less volume of diluted urine is produced
Discuss links between osmoregulation, blood volume, and blood pressure.
ADH increases the permeability of nephrons, therefore more water is reabsorbed into blood stream, resulting in an increase in the volume of blood, increased blood volume results in increased blood pressure
Where are the body receptors that detect changes in external temperature?
Skin
Where is the receptor that detects internal temperature.
Hypothalamus
When temperature is too cold, state 3 effectors that are stimulated by nerves and describe their effect.
Skeletal muscles – muscles contract and relax rapidly to generate more heat (shivering)
Smooth muscles – decrease blood flow to skin surface, keeping warm deep within the body
Arrector pili muscles – muscles contract, hair stands up, trapping an insulating layer of air to reduce heat loss
State two hormones that are released when the temperature is too cold and describe their effect.
Adrenaline and thyroxine : both increase metabolic rate, increasing heat generation
Describe how sweat gland respond when they receive stimulating from a nerve and explain how this cools the body.
Nerve impulse stimulates sweat glands to produce sweat on skin surface
Body heat is used to evaporate sweat
Evaporation has a cooling effect
Body heat is lost into the environment, thus cooling the body
Explain how nervous stimulation of smooth muscle can help cool the body.
Nerve impulse stimulates smooth muscles in blood vessels to relax/dilate (vasodilation), this increases blood flow to skin surface
Heat is radiated from the body, thus resulting in heat loss, which cools the body
Describe how hormonal changes can help reduce body temperature
Decreased production of adrenaline and thyroxine will result in decreased metabolic rate, therefore less heat is generated
What is the meaning of the term osmoregulation?
Water balance
State the two stimuli for osmoregulation and describe where these stimuli are detected.
Hypothalamus detect changes in concentration of the blood – solute concentration
e.g., High solute concentration = low water content = low blood volume = low blood pressure
Stretch receptors in blood vessels detect blood volume
e.g., more stretch = high blood volume = high water content = high blood pressure
Describe the nervous transmission involved in osmoregulation.
Nervous transmission from stretch receptors to the pituitary gland when stimulus is detected
State the name of the hormone involved in osmoregulation.
Anti diuretic hormone (ADH)
State the name of the effector involved in osmoregulation
Nephron tubule
Explain the effect of ADH on the permeability of the nephron
The more ADH present, the more permeable the nephron tubule
ADH increases the permeability of the nephron by transmitting cell signal to open aquaporins, which allow water reabsorption into the blood stream
Describe the effect on blood volume, blood pressure and urine volume when ADH is secreted.
By increasing the permeability of the nephron tubule, ADH increases the reabsorption of water into blood stream, this results in an increase in blood volume (Stretch muscles are more stretched)
Increased blood volume increases blood pressure
Less water content in urine, hence less volume of diluted urine is produced
What organ contains the receptors for changes in blood sugar levels
pancreas
What is the hormone that is secreted when blood sugar is high (e.g. after a meal)
Insulin (from beta cells)
What is the hormone that is secreted when blood sugar is too low?
Glucagon (from alpha cells)
What types of cell will contain receptors for insulin?
Liver, muscle, fat cells
Describe the effect of insulin binding on the cell and blood sugar levels.
Decreased blood sugar levels
By binding to complementary receptors on liver cells, insulin transmits cell signalling to open glucose protein channels glucose moves from blood into cell
Insulin initiates the uptake of glucose of in fat and muscle cells
(Glucose is converted into glycogen for storage)
Thus, there is less glucose in bloodstream, resulting in decreased blood sugar levels
What cells contain receptors for glucagon?
Liver cells
Describe the effect of glucagon binding on the cell and blood sugar levels.
By binding to complementary receptors on liver cells, glucagon transmits cell signalling to open glucose protein channels (glycogen is converted into glucose), glucose is released into the blood stream, thus, resulting in increased blood sugar levels
What happens to pH level when CO2 is dissolved in blood?
Decrease in pH (more acidic)
When CO2 dissolves in water, carbonic acid is produces, thi
What is the name of the receptor that detects changes in blood pH and where is it located?
respiratory centre in the brain
What does rapid breathing do to the CO2 levels in the blood? And the blood pH?
Decrease carbon dioxide levels in the blood, more carbon dioxide is transported via the blood to the lungs where it is eventually expelled through exhalation, decreased carbon dioxide levels increases blood pH levels (as it is less acidic)
What will holding your breath do to CO2 levels in the blood? And the blood pH?
Decrease blood pH levels, increase carbon dioxide levels
What is the type transmission that occurs when maintaining blood CO2 homeostasis?
Nervous transmission
What two groups of muscles are the effectors for CO2 homeostasis?
Respiratory muscles (chest muscles and diaphragm) and cardiac muscles
What is the response when CO2 levers are too high?
Increase breathing rate: increases expel of carbon dioxide
increase heart rate : trains your body to move oxygen and blood to your muscles more efficiently
this decreases carbon dioxide levels in blood, thus, increases blood pH levels
What is the response when CO2 levels are too low?
Decrease carbon dioxide levels, increase blood pH levels
Decrease heart rate and decrease breathing rate: less carbon dioxide is expelled, thus, increasing acidic, resulting in a decrease in blood pH levels
