Homeostasis Flashcards
How do body systems communicate?
Nerves and/or hormones
Human examples of homeostasis
Blood glucose levels, blood carbon dioxide levels, blood oxygen levels, water and solute balance, body temperature.
Organisms/cells are selective to their responses to stimuli
They only respond to ones that effect it in order to maintain balance/ systems
Abiotic factors that effect an environment or ecosystem
Mineral composition, light availability, oxygen levels, temperature, wind, pH.
What are optimum zones called?
Tolerance limits
Body of water with high nutrient level
Eutrophic
What is homeostasis?
The state of steady internal physical and chemical conditions maintained by living systems.
Nervous pathway
Direct via axons of nerve cells.
Nervous message
Electrochemical impulse.
Nervous site of action
Highly specific.
Nervous speed of action
Fast.
Nervous duration
Short term.
Hormonal pathway
Indirect via blood.
Hormonal message
Chemical.
Hormonal site of action
Target cells, can be widespread.
Hormonal speed of action
Slow.
Hormonal duration
Long term.
A stimulus is detected by a…
receptor.
The receptor conveys the message through to a…
control centre.
The control centre triggers a response by activating an…
effector.
What does an effector do?
An effector removes the stimulus or initiates an action that negates the stimulus.
Stimulus Response Model (Homeostasis)
Stimulus - receptor - control centre - effector
What is negative feedback?
Negative feedback is a response that results in the inhibition of a stimulus.
Excitatory neurotransmitter
Stimulates the next neuron in the pathway.
Inhibitory neurotransmitter
Blocks the nerve impulses from continuing.
What two systems compose the nervous system?
Central nervous system (CNS)
Peripheral nervous system (PNS)
CNS contains…
brain, spinal cord.
PNS consists of…
nerves outside the CNS.
Within the PNS there is the…
somatic nervous system (SNS) which is the voluntary nervous system.
The autonomic nervous system (ANS) contains involuntary nerves, which regulate…
all automatic functions like breathing and heart rate.
ANS is further broken down into what two systems?
Sympathetic nervous system (fight or flight and homeostasis)
Parasympathetic nervous system (rest and digest)
Sensory neurons functions
Carry information towards the CNS (afferent fibres)
Signals stimulate receptors which triggers action potentials towards the CNS.
Are generally unipolar.
Interneurons functions
Receive signals from sensory neurons and convey them to motor neurons.
Located in the CNS
Are multipolar.
Motor neurons functions
Carry signals from the CNS to the effectors
Are multipolar.
What are the three main types of neurons?
Sensory neurons, interneurons, and motor neurons.
What is the function of sensory neurons?
Sensory neurons transmit signals from sensory receptors to the central nervous system (CNS).
What is the structure of interneurons?
What is the structure of interneurons?
Describe the structure of a nerve pathway from receptor to effector.
The pathway involves the receptor detecting a stimulus, sensory neuron transmitting the signal to the CNS, interneurons processing the signal, motor neuron carrying the signal to the effector, and the effector responding.
What is the role of motor neurons?
Motor neurons carry signals from the CNS to effectors (muscles or glands) to elicit a response.
What is a synapse?
A synapse is a junction between two neurons or between a neuron and an effector cell.
What are neurotransmitters?
Neurotransmitters are chemical messengers that transmit signals across the synaptic cleft by binding to receptors on the postsynaptic membrane.
What is a reflex?
A reflex is an involuntary and nearly instantaneous movement in response to a stimulus.
Thermoreceptors
Detect changes in temperature.
Photoreceptors
Detect light.
Chemoreceptors
Detect chemical changes.
Mechanoreceptors
Detect physical changes, such as pressure or stretch.
Sensory receptors function
Sensory receptors are specialized cells or nerve endings that detect changes (stimuli) in the internal or external environment.
Effectors function
Effectors are muscles or glands that carry out the response to a stimulus, helping to restore the body to its optimal state.
Stimulus
A change in the internal or external environment is detected by sensory receptors.
Receptor
The sensory receptor processes the stimulus and sends a signal to the central nervous system (CNS).
Control Center
The CNS or endocrine system (e.g., brain, spinal cord, or glands) interprets the signal and determines the appropriate response.
Effector
The signal is sent to effectors (muscles or glands) to produce a response.
Response
The effectors carry out an action that counters the stimulus, bringing the body back to its optimal state.
Sensory Neurons structure
Sensory neurons have a cell body located in the middle of the axon, with dendrites connected to sensory receptors.
Sensory Neurons function
They transmit signals from sensory receptors (e.g., skin, eyes, ears) to the central nervous system (CNS).
Interneurons structure
Interneurons are found entirely within the CNS, having a short axon and highly branched dendrites.
Interneurons function
They process and integrate information received from sensory neurons and decide how the body should respond. They form connections between sensory and motor neurons, facilitating communication within the CNS.
Motor Neurons structure
Motor neurons have a cell body located at one end of the axon, with long axons extending to muscles or glands.
Motor Neurons function
They carry signals from the CNS to effectors (muscles or glands) to elicit a response, such as muscle contraction or secretion of hormones.
What is a synapse?
A synapse is a junction between two neurons or between a neuron and an effector cell.
What is the presynaptic terminal?
The end of the neuron sending the signal.
What is the synaptic cleft?
The gap between the neurons.
What is the post synaptic membrane?
On the receiving neuron or effector.
What are neurotransmitters?
Chemical messengers released by the presynaptic neuron into the synaptic cleft.
They bind to receptors on the postsynaptic membrane, leading to the continuation of the nerve impulse or the triggering of a response in an effector.
What system do hormones belong to?
The endocrine system.
What is the endocrine system responsible for?
The production and use of hormones.
What are hormones?
Hormones are chemicals secreted by endocrine glands located in various places around the body.
Where are hormones released?
Directly into the bloodstream.
What does the circulatory system consist of?
The heart, blood and blood vessels.
Blood transports the hormones all around the body but the hormone will only act upon…
the cells that have the specific receptors for these hormones (target cells).
What receptors do water- soluble hormones act upon?
Membrane receptors.
What receptors do lipid-soluble hormones act upon?
Cytoplasmic receptors.
Hormones are involved in long term regulation such as:
Growth
Reproduction
Blood glucose levels
What are hormones?
Hormones are chemicals that travel through the blood stream, take longer to act but have longer lasting effects.
What are the two main classifications of hormones?
Lipid and steroid
Hormones derived from amino acids.
What are the hormone receptors?
Proteins on the cell’s membrane or in the cytoplasm.
What is diabetes?
Diabetes is a disorder that means the body’s ability to produce and/or respond to the hormone insulin is impaired.
What does insulin do?
Insulin enables all cells (except brain cells) to uptake glucose.
What does the Islet of Langerhans cells in the pancreas secrete?
The peptide hormone glucagon
The hormone insulin.
What does glucagon do?
Glucagon causes glucose to be released from glycogen stores into the blood stream.
Type 1 Diabetes mellitus (insulin dependent diabetes)
An auto immune disorder where the immune system attacks the cells of the pancreas.
Type 2 diabetes mellitus (non-insulin dependent diabetes)
Caused either by a deficiency of insulin or, more commonly by a reduced responsiveness by target cells to insulin caused by changes to the insulin receptors.
What is hormonal imbalance?
The body responds to stimulus an over or under response, not achieving homeostasis.
What does insulin do to blood sugar levels?
Insulin decreases blood sugar levels.
What does glucagon do to blood sugar levels?
Glucagon increases blood sugar levels.
How is glucose transported across the cell membrane?
Glucose is transported across the cell membrane by glucose transporter proteins called GLUTs.
What are organisms that generate their own heat through metabolic processes called?
Endotherms.
What are organisms that require heat from external sources called?
Ectotherms.
What is blood temperature regulated by?
The thermoregulatory centre in the hypothalamus (receptor).
What is construction of the blood vessels called?
Vasoconstriction.
What does thyroxine do?
Thyroxine causes the body to burn more sugar (glucose) by increasing the metabolic rate. It enhances the breakdown of glucose and other nutrients to produce energy.
What is vasodilation?
Reduces nerve impulses to the blood vessels, increasing blood flow to the skin.
What is osmoregulation?
The maintenance of water and solutes in the body.
Where does osmoregulation occur?
The nephron.
Where does filtration occur and why?
The glomerulus due to the pressure.
What materials are filtered in the glomerulus and into the Bowman’s capsule?
Ions
Water
Urea
Amino acids
Glucose
What does not filter into the nephron as they are too big?
Proteins
Blood cells
Microvilli line the epithelial layer of the nephron along the…
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
What is Antidiuretic hormone (ADH)?
A hormone produced by the hypothalamus and released by the pituitary gland. ADH helps regulate the body’s water balance by controlling how much water the kidneys reabsorb.
What detects an increase in solute concentration?
Osmoreceptors in the hypothalamus.
What does ADH stimulate?
Vasoconstriction and reabsorption of water.
How does ADH allow reabsorption of water from the filtrate into the bloodstream through osmosis?
ADH makes the walls of the distal convoluted tubule and collecting duct more permeable to water by increasing the number of water channels (aquaporins) in their membranes.
What is osmosis?
Osmosis is the movement of water through a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.
What is the nephron?
The nephron is the basic functional unit of the kidney, responsible for filtering blood and forming urine.
How does osmosis occur in the nephron?
Osmosis in the nephron allows water to move from the filtrate back into the bloodstream, especially in the loop of Henle and collecting duct.
What is the role of ADH in the nephron?
ADH increases the permeability of the distal convoluted tubule and collecting duct, allowing more water to be reabsorbed through osmosis.
What triggers the release of ADH?
ADH is released when the body needs to conserve water.
What does adrenalin do?
Kicks of flight or fight response.
What is the fight or flight response?
The body’s response to an acute stress situation when a threat is perceived.
What releases adrenalin?
The adrenal medulla, located at the top of the kidney’s.
