Module 5 - Communication, Homeostasis, Energy

Define Homeostasis

The regulation of the body’s internal environment

Which is faster… Neuronal communication or hormonal communication?

Neuronal communication

What do neurons respond to ?

external changes

What is the role of neurons?

To transmit electrical impulses around the body

What is an effector? , give examples

Recieves impulse from motor neuron, muscle or gland

Name 3 types of neurons

sensory, relay, motor

What are 3 main features of a neuron?

Cell body, dendron, axon

What is the structure of the cell body in a neuron?

nucleus, surrounded by cytoplasm

In cytoplasm large amounts of endoplasmic reticulum and mitochondria

Why does the cell body of the neuron have many ER and mitochondria ?

to produce neurotransmitters

What do dendrons do?

Transmit nerve impulses towards the cell body

What do axons do?

Transmit nerve impulses away from the cell body

How many dendrons does a sensory neuron have?

1

What do sensory neurons do?

They transmit impulses from sensory receptor cells to a relay neuron

Where are relay neurons found?

In the CNS

What do relay neurons do?

Relay impulses from sensory neurons to motor neurons

What is the structure of a motor neuron?

Long axon, short dendrites

What is the structure of a relay neuron?

Short axon, Short dendrons

What do motor neurons do?

transmit impulses from a relay neuron to an effector/ gland

Which type of cell produces myelin?

Schwann Cells

Why are myelinated neurons better at transmitting impulses?

Because the electrical impulse ‘jumps’ to the next node of Ranvier

What is the name of the gap called between each Schwann cell?

Node of Ranvier

Why do non-myelinated neurons transmit impulses slower than myelinated neurons?

Because the impulse does not jump, it transmits continuously along the nerve fiber

What is a myelin sheath made of?

Layers of phospholipid bilayers

What does the myelin sheath act as?

insulator

Name 2 sense organs

ear, eye

What do sensory receptors do?

detect a stimulus, converts it into an electrical impulse

State 2 features of sensory receptors

* They are specific to a single type of stimulus
* They act as a transducer

How do sensory receptors act as transducers?

They detect the stimulus and convert it into a nerve impulse

What is the type of receptor that detects preassure?

Mechanoreceptor

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What is the type of receptor that detects chemical/ chemical changes?

Chemoreceptor

What is the type of receptor that detects heat?

thermoreceptor

What is the type of receptor that detects light?

Photoreceptor

Name an example of a mechanoreceptor …

Pacinian corpuscle

Name an example of a chemoreceptor …

end bulbs of Krause

Name an example of a photoreceptor

Cone Cell

What is the role of a sensory receptor as a transducer?

Detects different stimuli and converts it into a generator potential

What does the Pacinian corpuscle do?

Detects mechanical preassure

Where can a Pacinian corpuscle be found?

in the skin

What is the structure of the Pacinian corpuscle

Surrounds end of sensory neuron, layers of connective tissue separated by layers of gel

What type of sodium ion channels can be found in the Pacinian corpuscle?

Stretch mediated sodium ion channels

What happens when stretch mediated sodium ion channels in the Pacinian corpuscle change shape?

Their permeability to sodium ions changes

This is an image of the Pacinian corpuscle, what is the name of the missing label?

Neurone ending

This is an image of the Pacinian corpuscle, what is the name of the missing label?

Layers of connective tissue with viscous gel between

How does a Pacinian convert mechanical preassure into a nervous impulse? - (6)

* normal state= resting potential, Na+ channels too narrow to allow sodium ions to pass through them
* Mechanical preassure exerted on skin
* Pacinian corpuscle changes shape and strech mediated ion channels in neuronal membrane stretch and widen
* Sodium ions diffuse into membrane
* membrae depolarised
* Generator potential creates action potential and action potential transmitted along neuron to CNs

After the sensory receptor has detected a change in the environment, does the impulse that is sent along the neurone, permenantly change the voltage across the axons membrane?

No , temporarily

What are two states that the axon membrane switches between?

Resting potential, action potential

During resting potential is the neurone transmitting an impulse?

No

What is the rough potential difference of the axon during resting potential?

\-70mV

When the potential difference of a membrane is -70mV what is the membrane said to be?

Polarised

Why do sodium potassium ions need to be transported through channel proteins?

Because the phospholipid bilayer prevents the ions from diffusing across the membrane

During resting potential state what is actively transported out of the axon?

Sodium ions

During resting potential state what is actively trabsported into the axon?

Potassium ions

Fill In the gaps….

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The ……… protein called the sodium-potassium …… transports …… potassium ions …… the axon for every ……. Sodium ions …… of the axon

Intrinsic, pump, two, into, three, out

Fill in the gaps…..

Number of dots doesn't represent number of letters in missing word.

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For every …. Sodium ions that are pumped ……. , …… potassium ions are pumped …. .

3, out , 2 , in

What is the name given to a concentration gradient of ions?

Electrochemical gradient

Define/ state what resting potential is..

When there are more positively charged ions outside the axon membrane than inside the axon cytoplasm, causing the inside to be negative relative to the outside

What is depolarisation?

Change in potential difference of axon from negative to positive

What is the potential difference of the axon membrane during repolarisation?

\+40 mV

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X5 flashcards

When does an action potential occur?

When protein channels in the axon membrane change shape

What is a voltage gated ion channel?

The opening/closing of a change in voltage across the axon membrane

How does hyperpolarisation happen?

Both Na+ and K+ voltage gated channels close,so inside membrane becomes very negative relative to outside

Why does hyperpolarisation happen?

To prevent new action potential from being created

What is the refractory period?

A short period of time when the axon cannot be excited again

What happens during the refractory period?

Voltage gated sodium ion channels remain closed, to prevent sodium ions into the axon

Why is the refractory period important? (2)

* To ensure that action potentials are unidirectional
* To ensure action potentials don't overplap

What is propagation?

Movement of the action potential along the length of the axon.

What is saltatory conduction?

Depolarisation of axon in the nodes of Ranvier

Why do myelinated neurones transmit impulses faster than non-myelinated neurones?

Because the action potential ‘jumps’ from one node of Ranvier to the next, because depolarisation can only happen in nodes of Ranvier, which is faster than depolarising whole length of axon.

Why is saltatory conduction conduction faster?

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What are the 3 factors that can affect speed at which action potential travel?

Myelin, axon diameter, temperature

Why do impulses travel faster in axons with bigger diameters?

Because less resistance for flow of ions in cytoplasm compared to in axon with smaller diameter

Do impulses travel faster in smaller or larger axon diameters? Why?

Larger, less resistance to flow of ions

Why do impulses travel faster at higher impulses ?

Because ions diffuse faster

Why mustn't temperature get too high in neurons?(above 40⁰C)

Because the protein channels denature

Describe the All-or-nothing principle …

Threshold value must be reached I order to trigger response / action potential

Would a response / action potential be triggered if the threshold value isn't reached?

No

What is the effect of stimulus intensity on impulse frequency?

The more intense a stimulus the more frequent the action potentials

What device can be used to measure frequency of action potentials?

Oscilloscope

Whatisthe name of the junction between two neurones?

Synapse

What are the chemicals called that transmit a nervous impulse across a synapse ?

Neurotransmitter

What are the 6 key features of a synapse ?

Synaptic cleft, presynaptic neurone, post synaptic neurone, synaptic bulb, synaptic vesicles, neurotransmitter receptor

What are two types of neurotransmitter?

Excitatory and inhibitory

What is the synaptic cleft?

The gap which separates the axon of one neurone from the dendrite of the next neuron

What is the presynaptic neuron?

Neurone which impulse has arrived along

Whatisthe synaptic knob/bulb?

Swollen end of the presynaptic neurone which contains the neurotransmitter

What does the presynaptic bulb have a lot of (organelles )

Endoplasmic reticulum, Mitochondria

Why does the presynaptic bulb/knob have many ER's and Mitochondria?

To manufacture neurotransmitters

What are synaptic vesicles?

Vesicles containing neurotransmitters

How do neurotransmitters get to the post synaptic membrane?

Vesicles containing neurotransmitters fuse with pre synaptic membrane

contents released into synaptic cleft

Neurotransmitter binds to receptors in post synaptic membrane

What are neurotransmitter receptors?

Receptors which the neurotransmitter binds to

Where are neurotransmitters found?

In presynaptic bulb/knob

Where are neurotransmitter receptors found?

In post synaptic neurone membrane

What are excitatory neurotransmitters ?

Neurotransmitters which result in depolaristation in the post synaptic neurone, action potential is triggered only if threshold value is reached in the postsynaptic neurone

When is an action potential triggered in the post synaptic neurone?

If the threshold is reached

Name an example of an excitory neurotransmitter…

Acetylcholine

What is a cholinergic synapse ?

A synapse that uses acetylcholine as the neurotransmitter

What is an inhibitory neurotransmitter?

A neurotransmitter that results in hyperpolarisation of the postsynaptic neurones membrane , prevents action potential being triggered

What is an example of an inhibitory neurotransmitter?

GABA

What are the steps in synaptic transmission? (7)

* action potential reaches end of presynaptic neurone


* Depolarisation of presynaptic membrane causes calcium ions channels to open and calcium ions diffuse into presynaptic bulb
* This causes synaptic vesicles containing neurotransmitters to fuse with presynaptic membrane and neurotransmitters released into synaptic cleft via exocytosis
* Neurotransmitter diffuses across synaptic cleft and binds with specific receptor molecule in post synaptic membrane
* This causes sodium ion channels to open
* Sodium ions diffuse intopost synaptic neurone triggering an action potential