Bio U4 Flashcards by Simeon Edwards

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

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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

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Medulla Oblongata

Found at the base if the brain

Coordinates the unconscious functions of the body - breathing and heart rate

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Action potentials sent down the accelerator nerve …

Increase the heart rate

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Action potentials sent down the vagus nerve …

Reduce the heart rate

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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

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Baroreceptors

Detect changes in blood pressure

Found in the aorta / vena cava

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Chemoreceptors

Detect chemical changes

Found in aorta / Oblongata

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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

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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

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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

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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

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How do animals increase their chances if survival

By responding to changes in their external environment

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What is a stimulus

A change in internal/external environment

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Receptors

Detect stimuli (they are specific only detecting one particular stimulus

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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

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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