Bio U4 Flashcards
Type 2 diabetes
Non-insulin dependent
Still produces insulin
With age, response to insulin declines
Level of insulin secreted by B cells decline
Diet in high sugars, obesity and family history
Different ways in which the pancreas acts as endo and exocrine functions
Exocrine function of the pancreas j’s manufacturing and releasing digestive enzymes into ducts (lipase/amylase)
Endocrine function is releasing hormones into the blood
Islets of lancer hand have a endocrine function and contains a and B cells. å cells secrete glucagon and B cells secrete insulin into the blood.
Enzymes found in cells surrounding small tubules are released during the exocrine functions of the pancreas. The tubules carry the enzymes to the small intestine
Medulla Oblongata
Found at the base if the brain
Coordinates the unconscious functions of the body - breathing and heart rate
Action potentials sent down the accelerator nerve …
Increase the heart rate
Action potentials sent down the vagus nerve …
Reduce the heart rate
Why do animals need to alter their heart rate
Respond to internal stimuli
Prevent fainting due to low blood pressure
Make sure heart rate is high enough to supply body with enough oxygen
Baroreceptors
Detect changes in blood pressure
Found in the aorta / vena cava
Chemoreceptors
Detect chemical changes
Found in aorta / Oblongata
What is the cardiovascular centre
Specific region in the medulla Oblongata that receives sensory inputs about the levels of physical activity/ old CO2 concentration and bloood pressure
Sends nerve impulses to the SAN in the heart to alter the frequency of the excitation waves
Heart response to exercise
CO2 levels increase when exercising
Reduces pH in blood
Detected by chemoreceptors
Impulses sent to medulla Oblongata which sends a signal down the accelerator nerve to the SAN for a increase in HR
Heart rate response to adrenaline
Adrenaline is secreted in response to stress/injury
Adrenaline binds to the receptors on cardiac muscles
Cardiac muscles contract more frequently and with greater force
HR increases
Heart rate in response to BP
Increase in blood pressure is detected by baroreceptors
Impulses are sent to the medulla Oblongata and then via the vagus nerve to the SAN to decrease HR
How do animals increase their chances if survival
By responding to changes in their external environment
What is a stimulus
A change in internal/external environment
Receptors
Detect stimuli (they are specific only detecting one particular stimulus
Sensory receptors
Specialised cells that can detect changes in our surroundings
Transducers that concert one form of energy to another
Whatever the stimulus the sensory receptors convert the energy into a form of electrical energy called a nerve impulse
Effectors
Cells that bring about a response to a stimulus in order to produce a effect
Effectors can be muscle cells and cells found in glands
Sensory Neurons
Transmit nerve impulses from receptors to the CNS
Has long dendrone that transmits the impulse to the cell body
Axon carries the impulse from the cell body to the axon terminal where the neurotransmitters are released
Motor Neurones
Transmit nerve impulses from the CNS to the effectors
Dendrites receive information from the CNS
The electrical impulse travels from the cell body along the axon terminal where the neurotransmitters are released
Relay neurones
Transmit nerve impulses between sensory and motor neurones
What creates and maintains a neurones resting potential
Sodium-potassium pump
Voltage gated potassium channels
IN THE NEURONES MEMBRANE
What is the potential difference across a neurone membrane
-60mV
What is a action potential
When a neurone is stimulated, other ion channels in the cell membrane called sodium ion channels open
What are the sequence of events that occur during the action potential
1 stimulus 2 depolarisation 3 repolarisation 4 hyperpolarisation 5 resting potential
Stimulus
Excites the neurone cell membrane causing Na+ ion channels to open
Membrane becomes more permeable to sodium so sodium ions diffuse into the neurone down the sodium ion electrochemical gradient
Inside of neurone turns less negative
Depolarisation
If potential difference reaches the threshold potential (-55mV) voltage gates sodium ion channels open and more sodium ions diffuse into the neurone
Repolarisation
At a potential difference of +40mV sodium channels close and potassium ion channels open
Membrane is more permeable to potassium so potassium ions diffuse out of the neurone down the potassium ion concentration gradient (membranes starts to get back to resting potential )
Hyperpolarisation
Potassium ion channels are slow to close resulting in a slight overshoot and too much potassium ions diffuse out of the neurone
Potential difference becomes more negative than the resting potential (-70mV)
Resting potential
Ion channels are reset
Sodium-potassium pump returns the membrane to it’s resting potential by pumping sodium ions out and potassium ions in
Maintains resting potential until the membrane is exited by another stimulus
What is the refractory period
During the refractory period
Ion channels are recovering and cannot be made to open
This is a time delay to ensure the action potentials do not overlap, ensuring they are unidirectional
What is the all or nothing principle
When the threshold potential is reached, the action potential is always generated.
Is threshold isn’t reached, the action potential will not fire.
How are local currents created in the cytoplasm if the neurone
Opening of sodium ion channels
Outline local currents
Following a stimulus sodium ions move into the neurone and trigger a action potential
They then diffuse along the axon and cause sodium channels further along the membrane to open
This causes a influx of na+ and another action potential is triggered
What is the myelin sheath
An insulating layer of fatty material
Axon diameter
Larger the axon diameter the faster the electrical impulse because there is less resistance
Temperature
Increase in temperature = increase in electrical impulses
This is because there is more kinetic energy so sodium ions can diffuse quicker into the neurone
If temp continues to increase the protein in the membrane will denature and tertiary structure would change and it wouldn’t be able to function
Synaptic Divergence
One neurone connects to many neurones
Allows information to be dispersed to many different parts of the body
Synaptic divergence
Many neurones connect to one neurone
Allows signal to be AMPLIFIED
Temporal summation
One action potential in the presynaptic neurone does not produce a AP in the post synaptic neurone
Require series of APs in presynaptic neurone
Spatial summation
Several presynaptic neurones may each contribute to producing an AP in the post synaptic neurone
What is SUMMATION
The way in which several small action potential changes can combine to produce in larger change in potential different across the membrane
Type 1 diabetes
Insulin dependent
Starts in childhood
Autoimmune response where the body’s own immune system attacks the B cells
Body cannot manufacture sufficient insulin
