Module 1- Communication and Homeostasis Flashcards
Ectotherms
Organisms that rely on external sources of heat and behavioural activities to regulate their body temperature.
Endotherms
Organisms that can control production and loss of heat to maintain their body temperature.
Homeostasis
The maintenance of a constant internal environment.
Autonomic nervous system
The system of motor neurones that controls the non-conscious actions of the body. The autonomic system controls the actions of involuntary muscles and glands.
Myelin
A fatty sheath around a neurone that consists of many layers of the plasma membranes of Schwann cells.
Negative feedback
A process in which any change in a parameter brings about the reversal o that change so the parameter is kept fairly constant.
Positive feedback
A process in which any change in a parameter brings about an increase in that change.
What are the stages of homeostasis?
Stimulus Receptor Control mechanism Effector Response
Stimulus
A change in the internal or external environment.
Receptor
A specialised nerve cell that detects a stimulus.
Control mechanism
An organ that responds to information and stimulates an effector.
Effector
A muscle or gland that brings about a change in the body.
Why is thermoregulation important?
Changes in body temperature can have an effect on enzymes in the body. The activity of enzymes is effected if they are not kept at, or close to, their optimum temperature. If body temperature changes dramatically, the enzymes will not function properly and this will effect the level of physical activity that can be achieved by the organism.
What is the function of a sensory neurone?
Transmits nervous impulses from the receptors to the central nervous system.
What is the function of a relay neurone?
Transmits nervous impulses between sensory neurones and motor neurones.
What is the function of a motor neurone?
Transmits nervous impulses between the central nervous system and the effectors.
What are structural similarities of sensory and motor neurones?
- Both have a cell body, dendrites, axon, nucleus, myelin sheath and nodes of Ranvier.
- Both have sodium/potassium pumps to maintain a potential difference across the plasma membrane.
What are structural differences between sensory and motor neurones?
- Motor neurones have their cell body at the end of the axon, whilst sensory neurones have their cell body in the middle of the axon.
- Only sensory neurones have dendrons.
- Sensory neurones have dendrites in the CNS, whilst motor neurones have their cell body in the CNS.
What are functional similarities between sensory and motor neurones?
- Both are used to transmit electrical pulses.
- Both use ATP to actively pump sodium/potassium ions across their cell surface membranes.
What are the functional differences of sensory and motor neurones?
The direction of nerve impulse is towards the cell body in sensory neurones, but away from the cell body in motor neurones.
Concentration gradient
This arises when there is a higher concentration gradient of a chemical in one area and a lower concentration of the same chemical in a another area. Chemicals move down the concentration gradient by diffusion.
Polarisation
This is when the inside of a neurone cell is negative in relation to the outside of the cell.
Depolarisation
This is when the inside of a neurone cell is positive in relation to outside of the cell.
Resting potential
This is -60mV. This is when the neurone is not responding to a stimulus. The neurone will still be pumping ions across its membrane.
Action potential
This is when an electrical impulse will be generated and passed along the neurone cell membrane. Action potentials are only generated when the potential difference of the cell reaches +40mV.
Threshold potential
This is -50mV. Depolarisation of the membrane must reach this value in order for an action potential to be generated.
Voltage-gated channel
Channels in the cell membrane that allow the passage of ions. they open and close in response to changes in the potential difference of the membrane.
What happens at every stage of the initiation?
The sodium/potassium pump actively transports 3 Na+ ions out and 2 K+ ions into the cell.
What is the order of stages in 1 action potential?
Resting membrane potential Depolarisation Action potential Repolarisation Hyperpolarisation Resting membrane potential
What happens to the speed of impulse when the temperature is increased?
This increases the rate at which ions can diffuse into and out of the axon.
What happens to the speed of impulse when the diameter of the axon increases?
An increase in this parameter decreases the volume of axoplasm that is in contact with the neurilemma, so this reduces the resistance experienced by the flow of charge.
Saltatory conduction
Propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials without needing to increase the diameter of an axon.
What are the 3 major roles of nerve junctions in the body?
- They transmit information between different neurones.
- They ensure information is transmitted in one direction only.
- They filter-out unimportant or low-level stimuli.
Synapse
A junction between two neurones (presynaptic neurone and posthypnotic neurone).
Synaptic Cleft
The gap between the presynaptic neurone and a postsynaptic neurone.
Cholinergic Synapse
A synapse that uses acetylcholine as a neurotransmitter.
Synaptic Knob
A swelling at the end of a presynaptic membrane.
Summation
This is when a series of small potential differences can combine to produce a larger potential difference, which may result in an action potential.
Endocrine gland
A gland that secretes hormones directly into the blood. They have no ducts.
Exocrine gland
A gland that secretes molecules into a duct that carriers the molecules to where they are used.
Hormones
Molecules that are released by endocrine glands directly into the blood. They act as messengers, carrying a signal from the endocrine gland to a specific target organ or tissue.
Target tissue
Tissue that contain cells that possess a specific receptor on their plasma membrane. The shape of the receptor is complementary to the shape of the hormone molecule.
First messenger
Hormone that transmits a signal around the body. (Adrenaline)
Second messenger
Transmits a signal inside the cell (cAMP).
Name the parts of the adrenal gland
Adrenal medulla
Adrenal cortex
What does the adrenal cortex do? Give examples.
Uses cholesterol to produce certain steroid hormones.
e.g Aldosterone and Cortisol
What is the role of the adrenal medulla?
Manufacture and release the hormone adrenaline in response to stress such as pain or shock.
What are the functions of the endocrine glands in the pancreas?
- Releases insulin to regulate blood glucose
- Releases glucagon
What are the functions of the exocrine glands in the pancreas?
Releases digestive enzymes.
What cells are found in the pancreas?
The islets of Langerhans which contain alpha and beta cells.
What do alpha cells secrete?
Glucagon
What do beta cells secrete?
Insulin
Definition of glucagon
A hormone released by alpha cells that triggers the conversion of glycogen into glucose. (Glycogenolysis)
Definition of glycogen
A storage molecule in the liver
Definition of glycogenesis
This is the conversion of of glucose into glycogen, caused by the hormone insulin.
Definition of Gluconeogenesis
This is the conversion of amino acids or fats into glucose.
What is the first step in a beta cell?
At rest, the beta cell has a potential difference of -70mv, caused by the effect of K+ ions.
What is the second step inside a beta cell?
A rise in glucose causes glucose to enter the beta cell by diffusion. Glucose is metabolised to produce ATP which is used to close K+ channels.
What is the third step inside a beta cell?
The potential difference becomes relatively positive, causing Ca2+ channels to open.
What is the final step inside a beta cell?
Ca2+ ions enter, causing the insulin vesicles to fuse with the membrane and insulin is released by exocytosis.
What are the similarities of hormonal and neuronal transmission? (6)
- The cell starts with a negative potential difference, relative to the outside.
- The cell contains K+ channels and Ca2+ channels.
- An increase in potential difference precedes the secretion of a protein molecule.
- Vesicles act as storage vessels for a protein molecule.
- Vesicles fuse with the cell surface membrane.
- Vesicles release their content by exocytosis.
What only happens in a hormonal response?
- An increase in glucose concentration initiates changes.
- Glucose in metabolised to close K+ channels.
- Vesicles contain insulin.
- A protein molecule is secreted into the bloodstream.
- This is an example of a homeostatic mechanism.
What only happens in a neuronal response?
- An action potential initiates changes to the cell.
- Vesicles contain a neurotransmitter.
- A protein molecule is secreted into the synaptic cleft.
What is Diabetes mellitus?
A disease in which blood glucose concentration cannot be controlled effectively, caused by an inability to produce or respond to insulin.
What are the causes of type 1 diabetes?
Result of an autoimmune response in which the body’s own immune system attack the beta cells and destroys them.
Who is at risk of getting type 1 diabetes?
Children
What is the treatment of type 1 diabetes?
Insulin injections everyday.
What is the cause of type 2 diabetes?
Glycoproteins on the surface of the liver and muscle cells decline and the cells lose their ability to respond to the insulin in the blood. Beta cells might stop producing insulin.
Who is at risk of developing type 2 diabetes?
People with:
- Obesity
- Diet in high sugars
- Asian or afro-caribbean
- family history
What is the treatment of type 2 diabetes?
- Careful monitoring and control of diet.
- Can be supplemented by insulin injections or use of other drugs which slow down the absorption of glucose from the digestive system.
What nutrients in a diet should someone with type 2 diabetes have?
Increased: Cellulose
Decrease: Sucrose/starch
Limit: Protein
List five advantages of using bacteria to synthesis insulin for diabetic patients.
- Lower risk of infection
- Less chance of developing an intolerance to the insulin.
- Cheaper to manufacture the insulin then to extract it from animals.
- Exact copy of human insulin, therefore it is more fast acting and more effective.
- The manufacturing process is more adaptable to demand.
Where is the cardiovascular control centre (CCC) located?
Medulla oblongata in the brain.
How does heart rate increase as a result of a neuronal response?
A motor neurone, called the accelerator neurone connects the CCC to the sion-atrial node of the heart. This increases heart rate. (sympathetic nervous system)
How does heart rate decrease as a result of a neuronal response?
A motor neurone called the vagus neurone connects the CCC to the sino-atrial node of the heart. This is part of the parasympathetic nervous system- so decrease.
Which hormone increases heart rate?
Adrenaline
What happens when the hormone adrenaline gets released?
- Binds to the receptors on the plasma membrane of the SAN.
- Triggers acetyl cyclase to convert ATP to cAMP.
- cAMP activates reactions, which make the plasma membrane more permeable to sodium ions.
- This causes depolarisation of the SAN, which triggers contractions of the heart muscle.
