Chapter 13 - Neuronal communication Flashcards
What kind of response is admitted via neurones?
Electrical responses
What is homeostasis?
The coordination of all organ functions in order to maintain a relatively constant internal environment
What is cell signalling in animals?
Cellular communication via chemicals which target certain cells
How do cells signal?
- Locally, via neurones at the synapse (neurotransmitter)
- Across a large distance, via hormones
In what order does a nervous response occur?
Receptor > sensory neurones > relay neurone > motor neurone > effector cell
What is the role of a sensory neurone?
Moves an impulse from sensory receptor cells to a relay neurone, motor neurone or the brain
What is the role of a relay neurone?
Moves an impulse between neurones
What is the role of a motor neurone?
Moves an impulse from a relay neurone to an effector
What is the myelin sheath?
A layer of plasma membranes made by specialised schwann cells which surround the neurone which act as an insulating layer and allow electrical impulses to be conducted at a much faster speed
What are the gaps between the myelin sheaths and what do they do?
Nodes of Ranvier, assists the travel of an electrical impulse down a neurone at a faster speed
What are some features of a sensory neurone?
- They are specific to a single type of stimulus
- They act as a transducer
What is a mechanoreceptor?
A receptor that detects pressure and movement (eg. skin, pacinian corpuscle)
What is a chemoreceptor?
An olfactory receptor that detects chemicals/ scents (eg. nose)
What is a thermoreceptor?
A receptor that detects heat (eg. tongue)
What is a photoreceptor?
A receptor that detects light wavelengths (eg. eye)
What is the role of a transducer?
To convert one type of energy to another (eg. thermal stimulus into electric impulse for signalling)
What is a pacinian corpuscle?
A specific sensory receptor that detects mechanical pressure, located at the end of neurones
What ions are present in the neurone and corpuscle?
Na+ and K+
What type of channel is present in the corpuscle?
Stretch-mediated sodium channel
What is the resting potential in a neurone?
-70 mv (3Na+ exchanged for 2K+ at the sodium-potassium pumps)
What potential is needed to be reached to release an action potential?
-55 mv is the threshold value needed to be reached to fire an action potential
Describe the neurone in a resting potential state
- Sodium-potassium pumps actively transports Na+ and K+ out/into the axon
- More K+ ions present inside the axon than outside, so Na+ ions diffuse back into the axon down the electrochemical gradient and K+ ions diffuse out
- More positive charge outside the axon, causing the resting potential of -70 mv
Describe what is occuring during an action potential
