Neuronal Communication - Nerves, Synapses, and more Flashcards
What is sensitivity?
The ability to detect and respond to changes in one’s internal and external environment.
What are some examples of types of sensory receptors?
mechanoreceptor (pressure)
thermoreceptor (temperature)
photoreceptor (light)
How do sensory receptors work?
Resting potential - stretch-mediated Na channels too narrow to let Na enter. Pressure applied (stimulus) changes shape of Na channel, allowing Na to diffuse in. Depolarisation of Na going in causes an action potential.
What is a resting potential?
-70 mV, when a neurone is not transmitting a nerve impulse.
What is the difference between polarisation and depolarisation?
when polarised, the membrane potential is -70mV, meaning there is less positive charges inside than outside. when depolarised, the membrane potential is higher than -70, with more positive charge inside than outside.
What is hyperpolarisation?
Membrane potential lower than -70 mV (even less positive charges inside)
What is a voltage gated channel?
Channels that are open or shut temporarily depending on the membrane potential.
What is an action potential?
nerve impulse, temporary reversal of potential difference across axon membrane. -70 mV -> +40mV
What are the three types of neuron?
sensory
relay
motor
What is a myelin sheath?
Insulating layer covering the axon.
What is a myelinated neuron?
a neuron surrounded by myelin sheath, with a faster conduction time.
What produces the myelin sheath?
The schwann cells within the axon nodes.
What is a Sodium-Potassium (NaK) pump?
The mechanism that maintains a resting potential of -70mV
- 3 Na+ pumped out, 2 K+ pumped in
- K+ diffuses out
- Na+ closed out from cell by voltage-gates.
- Neuron membrane more negative inside than outside membrane
How is an action potential created?
Energy from stimulus causes Na+ voltage gates to open.
Na+ diffuses into neuron, positive feedback.
membrane becomes depolarised - depolarisation at +40mV.
K+ channels open
too many positive ions diffuse in - hyperpolarisation
K+ channels close, only Na+ can diffuse out.
How does a cholinergic synapse work?
Stimulus causes Ca2+ channels to open
Vesicles containing ACh (Acetylcholine) fuse w/ membrane
Release ACh by exocytocis
Action Potential at post synapse
Acetylcholinesterase breaks down ACh into choline + ethanoic acid
Process repeats
How is an action potential propagated?
Stimulus causes influx of Na+ at beginning of neuron - depolarisation
Na+ moves down negatively charged neuron, down electrochemical gradient.
In previous areas, Na+ channels close. K+ opens, repolarisation occurs.
What is the cerebrum?
Part of brain that controls voluntary response, and sensory information.
What is the Cerebellum?
Part of brain that controls muscular movement, balance, posture - coordinates movement. Controls all kinaesthetic sense.
What is the Hypothalamus?
Part of brain that controls autonomic nervous system, homeostasis, and uses endocrine gland.
What is the Medulla Oblongata?
Part of brain that controls autonomic nervous system for reflex actions, such as breathing, beating heart, coughing, swallowing, peristalsis.
What is the difference between the posterior and the anterior pituitary gland?
The anterior releases 6 different hormones, whereas the posterior releases just ADH (anti-diuret hormone).
How does sliding filament theory work?
Myosin heads can’t bind to actin due to tropomysosin blocking it.
AP causes Ca to be released - tropomysoin leaves
Myosin heads bind to actin binding site
Myosin head changes angle - ADP released
Phosphorylation of ATP - myosin head leaves
ATP hydrolysed back to ADP - ready to reattatch further along the actin filament.
What is a neuron?
A single nerve cell
What is a nerve?
A bundle of nerve fibres
What is a dendron?
The small extensions of the cell body that subdivide into dendrites
What are the nodes of Ranvier?
Gaps between adjacent schwann cells
What is an axon?
A cylindrical fibre which carries nerve impulses away from cell body
What is a transducer?
A converter of a stimulus into electrical energy (e.g. photoreceptors turning light stimulus into electrical energy)
What is a nerve impulse?
An electrical signal transmitted across a nerve fibre
What does the Central Nervous System (CNS) consist of?
Spinal cord and Brain
What is saltatory conduction?
The way an electrical impulse skips from node to node down the full length of an axon.
What is the refractory period for?
The recovery period for the resting potential to be re-achieved.
