Module 5.1.1 - Neuronal communication Flashcards
What is homeostasis?
Maintenance of relatively constant conditions inside the body
What are some external changes to the environment?
- temp
- soil pH
- light intensity
- loud noises
What are some internal changes to the environment?
- pH in blood
- blood glucose
- temp
- water potential
Do plants have a nervous system?
No but can still respond to changes in environment to survive
How to animals react to change?
Electrical responses via neurones and chemical responses via hormones
How do plants react to change?
Chemical responses via hormones
What is the nervous system?
Electrical impulses that detect changes/stimuli
What is a motor neurone?
Transmits impulses from relay or sensory neurones to an effector
What is a relay neurone?
Transmits impulses between neurones
What are parts of a relay neurone?
Cell body, dendrons, axons, nucleus, dendrites
What are parts of a motor neurone?
Cell body, dendrites, cytoplasm, nucleus, myelin sheath, axon, node of Ranvier, axon terminals
What is a sensory neurone?
Neurone that transmits impulses from receptor cell to relay or motor neurone or brain
What are parts of a sensory neurone?
Dendrites, dendron, myelin sheath, nucleus, cytoplasm, neurotransmitters, cell body, axon, node of Ranvier, axon terminal
What is the process from stimuli to response?
Stimuli, receptor, sensory neurone, relay neurone, motor neurone, effector, response
What are Schwann cells?
Produce large layers of plasma membrane around an axon, called myelin sheath
- type of glia cells
What is saltatory conduction?
Impulse jumping from each node of Ranvier (small gap in between each myelin sheath) to the next
What is multiple sclerosis?
Impaired Schwann cells, brain detects myelin as foreign so breaks it down, own immune system damages you
- results in loss of muscle control, vision and balance
What are sensory receptors?
Allow body to detect changes in environment, often located in sense organs, specific to 1 type of stimulus
What do sensory receptors act as?
Transducers
What are transducers?
Sensory receptors convert stimulus into nerve impulses called generated potential, this is then passed through nervous system to brin a response by sending out impulse to an effector - action potential
What are Pacinian corpuscle?
Specific sensory receptors that detect mechanical pressure
- located deep within the skin, most abundant in fingers and soles of feet
How does depolarization in Pacinian corpuscles happen?
Pressure is applied/ stimulated which widens the stretch median sodium channels, allowing sodium ions to enter which makes the cell positive
- generated potential is created
- a nerve impulse/action potential is then generated
What is resting potential?
Outside of membrane is more positive than outside, is polarized, around -70mV
What is action potential?
Stimulus detected by sensory receptor, energy of stimulus temporarily reverses charge on axon membrane, potential difference across membrane is +40mV, depolarized, when impulse passes is repolarizes neurone back to resting potential
What is the refractory period?
After action potential, short period of time when axon cannot be excited again, voltage gated sodium ion channels remain closed
Why is the refractory period importnat?
Make sure action potential travels in 1 direction and they don’t overlap
How can action potential be sped up?
- myelination
- axon diameter, less resistance to flow of ions in cytoplasm if large axon diameter
- temperature, diffuse faster at high temp but will denature if too high
What is the all or nothing principle?
Nerve impulses said to be all-or-nothing response, threshold value must be reached to trigger a response, no matter the stimulus the same sized action potential will be triggered
What is a synapse?
Junction between 2 neurones or a neurone and effector
What do synapses do?
- ensure impulse is unidirectional
- impulse from 1 neurone to be transmitted to many
- impulses from many neurones to be transmitted to 1
How do synapses work?
- action potential causes voltage gated calcium channels to open, influx calcium ions down electrochem gradient
- vesicles fuse with pre synaptic membrane, voltage gated sodium channels on post synaptic membrane
- neurotransmitters bind to receptors on v-g Na+ channels and they open
- influx Na+ ions down electrochem gradient, +ve charge causes depolarisation , generate action potential
What is ACH and ACHE?
ACH - acetylcholine is a neurotransmitter
ACHE - acetylcholinesterase is an enzyme that breaks down ACH that’s binded to receptors