module 5.1.1 communication and homeostasis

What are the 2 systems of the nervous system?

Central Nervous System (CNS)

Peripheral Nervous System (PNS)

what is the CNS composed off

brain

spinal cord

what is the PNS composed off

neurones that connect the CNS to the rest of the body

structure of the nervous system ( image)

what are the two systems of the PNS

somatic nervous systems

autonomic nervous systems

function of somatic nervous system

consciously controls voluntary muscle movement

Function of the autonomic nervous system

unconsciously controls involuntary activities such as heartbeat and digestion

what systems can the autonomic nervous system be split into?

parasympathetic nervous system

sympathetic nervous system

what is the function of the sympathetic nervous system?

Activates your flight or fight response

what is the neurotransmitter involved in the sympathetic nervous system?

noradrenaline

adrenaline

what is the neurotransmitter involved in the parasympathetic nervous system?

Acetylcholine

what is the sympathetic system affect on activity levels

Increases

what is the parasympathetic system affect on activity levels

Decreases

what are the 5 structures of the brain

Cerebrum

cerebellum

Hypothalamus

Medulla oblongata

Pituitary gland

function of cerebrum

control Higher brain function ( decision making)

function of Hypothalamus

maintain homeostasis

maintains temperature, control Ψ of blood and hormone production

what is the pituitary gland controlled by

hypothalamus

function of the pituitary gland

produces hormones and stimulates other glands

function of cerebellum

Coordinate muscular movement and maintain balance

function of medulla oblongata

controls involuntary functions

heart rate, breathing rate and blood pressure

what are the three types of neurones?

Sensory,

relay

motor

what is the function of the Sensory neurones?

Transmit nerve impulses from receptors to the CNS

what is the function of the Motor neurones?

Transmit nerve impulse from the CNS to effectors

what is the function of the Relay neurones?

Transmit nerve impulse between sensory neurons and motor

Pathway of Nervous communication (image)

structure of neurons ( image)

Do neurones have all the normal cell organelles ?

YES

Functions of dendrites and dendrons ?

carry nerve impulses towards the cell body

functions of Axon

carry the nerve impulse away from the cell body

how to remember the functions of Axons and Dendrites

Axons → Away cell body

Dendrites → towarDs cell body

what type of impulses does the nervous system use?

electrical impulses

What is meant by resting potential?

Potential difference ( P.D) when a cell is at rest ( no stimulus)

what is the charges of a nervous system receptor at resting potential?

The inside is more negatively charged relative to the outside --> creates a P.D

what generates resting potential

ion pumps and ion channels

what is a generator potential?

Change in potential difference due to a stimulus

What happens to the membrane when a stimulus is detected ?

Cell membrane becomes more permeable

allows more ions to move in /out of cell

altering the P.D

creates a generator potential

Stimulus and generator potential relationship

Bigger the stimulus → Greater generator potential produced.

what is P.D measured in

millivolts (mV)

what is a action potential

nerve impulse along a neuron

what happens when the generator potential doesn't reach the threshold level ( value)

No Action potential ( stimulus is too weak)

what happens when the generator potential does reach the threshold level

Action potential is triggered

Describe the stimulation of the Pacinian corpuscle

gets stimulated ( tap on arm), lamellae is deformed and press on sensory nerve ending

deforms the stretch mediated Na channels in neurone cell membrane

Na⁺ channels open → Na⁺ diffuses into cell → creating a generator potential

if it reaches threshold level → triggers action potential

Where is the Pacinian corpuscle located?

Skin

What does the pacinian corpuscle detect?

mechanical stimuli ( vibrations and pressure)

Why is it important that organisms respond to stimuli

increase their chance of survival

how do sensory receptors act as transducer ?

convert the energy of a stimulus into electrical energy

Function of the cell body

releases neurotransmitters 

structure of mylein sheath

layers of plasma membrane ( lipids)

function of mylein sheath

acts as a insultating layer helps speed up rate of transmission

what maintains and creates the resting potential in n

sodium-potassium pumps

potassium ion channels

in neurones membrane

is the membrane polarised and how?

yes

inside membrane is more negatively charged then outside ( more cations outside)

Resting potential maintenance ( image)

SOPI → sodium out potassium in

How is the resting potential maintained

Sodium potassium pumps actively ( ATP) move 3 Na⁺ out of neurone for every 2K⁺ moved in

potassium ion channels allow facilitated diffusion of K⁺ out of neurone 

at rest which channels are open

potassium channels are open

sodium are closed

when do action potentials happen

when the neurone is stimulated

what is the voltage value of a neurone at resting potential

-70 mv

Action potential graph

Action potential graph

what are the 5 stages of a action potential 

stimulus 

depolarisation 

repolarisation 

hyperpolarisation 

resting potential

action potential ( stimulus)

 stimulus causes sodium ion channels to open

membrane becomes more permeable →  Na⁺ diffuses into neurone 

neurone membrane becomes less negative 

action potential ( Depolarisation )

P.D reaches Threshold → voltage- gated sodium ion channels open → more Na⁺ diffuse into the neurone ( postive feedback)

action potential ( Repolarisation)

sodium ion channel closes, voltage-gated potassium ion channels open

K⁺ diffuses out of the neuron → membrane starts to go back to resting potential ( negative feedback)

action potential ( Hyperpolarisation)

potassium ion channels are slow to close → many K⁺ ions to diffuse out of the neurone

P.D becomes more negative then resting potential ( less then -70 mv)

action potential ( Resting potential)

ion channels are reset

sodium-potassium pump moves 3Na⁺ out and 2K⁺ in returning membrane to resting potential.

what is the retractory period?

time delay between action potentials as the ion channels are recovering.

neurone cell membrane cant be stimulated

what is the function of the retractory period 

ensures action potentials dont overlap

action potentials travel in one direction

what is the result of a bigger stimulus

larger stimulus = more frequent action potentials 

factors that affect the rate of conduction of action potentials

Myelination

Axon diameter

Temperature

myelination effect on rate of conduction of action potential

 myelination leads to faster rate as depolarisation only happens at the nodes of Ranvier 

impulse transmitted from node to node ( this is called saltarory conduction)

non myleinated → impulse travels as a wave along length of axon membrane

Axon diameter effect on rate of conduction of action potential

larger diameter = faster 

less resistance to flow of ions than in cytoplasm of smaller axon

depolarisation reaches other parts of neurone membrane faster

Temperature effect on rate of conduction of action potential

temperature increases = rate increases

ions diffuse faster

past 40°C protein pumps and channels denature and speed decreases

what is the cholinergic synapse neurotransmitter ?

acetylcholine (ACh)

what does ACh bind to

cholinergic receptors

How are neurotransmitters removed from the cleft

Broken down by enzymes

Take back into the presynaptic neurone

Which neurotransmitter uses cholinergic synapses

Acetylcholine (ACh)

Cholinergic synaptic transmission process?

Action potential arrives at the synaptic knob of the presynaptic neurone → calcium ion channel open Ca²⁺ diffuses in to synaptic knob

Influx of Ca²⁺ → vesicles to fuse with presynaptic membrane and exocytosis ( releases ACh)

ACh diffuses across synaptic cleft binds to Cholinergic receptors on post synaptic membrane → Na⁺ channels to open

Influx of Na⁺ → depolarisation

Creates a action potential in post synaptic membrane if threshold is met

How is ACh removed from synaptic cleft

Broken down by enzyme ( acetylcholinesterase)

Products are re-absorbed by the presynpatic neurone

What are agonists

Chemicals with the same shape of neurotransmitter that bind to the same receptors

Example of a agonist

Nicotine (mimics acetylcholine) binds to Cholinergic receptors in the brain

Function/ action of curare

Curare → blocks the effects acetylcholine by blocking certain cholinergic receptors

Muscles can’t be stimulated

Function/ action of nerve gases

Prevents acetylcholine from being broken down in synaptic cleft

Leads to loss of muscle control

Function/ action of Opioids

Blocks calcium ion channels in presynpatic neurone → fewer vesicles → less neurotransmitters released

What are the two types of synapses

Excitatory

Inhibitory

What is a excitatory synapse

A synapse where excitatory neurotransmitters are released

What is a inhibitory synapse

A synapse whre inhibitory neurotransmitters are released

What is meant by a excitatory neurotransmitters

result in the Depolarisation of the postsynaptic membrane → action potential

What is meant by inhibitory synapse

Where a inhibitory neurotransmitters are released is an inhibitory synpase

What is synaptic divergence

One neurone connects ( releases neurotransmitters) to many neurones

What is synaptic convergence?

Many neurones connect to one neurone

Difference between synaptic convergence and divergence

Convergence → many neurones connect to one neurone / information is stronger ( Con = neurones come together)

Divergence → one neurone connects to many neurones

Synaptic divergence ( image)

Synaptic convergence ( image)

Wha are the two types of summation

Spatial summation

Temporal summation

What is summation

Stimulus is too weak

Total sum of lots of smaller impulses trigger an action potential

What is spatial summation

Two or more presynaptic neurones converge and release their neurotransmitters simultaneously on same postsynaptic membranes

Effect on inhibitory neurotransmitters on action potential

No action potential

What is temporal summation

Neurone impulse arrives in quick succession from same presynaptic neurone

Higher chance of action potential

Temporal summation ( image)

Spatial summation ( image)

What is the direction of a synapse impulse

Unidirectional ( travel in one direction)