The Neuron Flashcards
(24 cards)
Homeostasis
A process by which a constant internal environment is maintained despite changes in the external environment
Nervous System (quick short term response)
Endocrine System (slow & long term response)
Nervous system
~Involves reception, transmission, interpretation and response
~Two main subsystems: CNS (which consists of the brain and spinal cord) & PNS (somatic voluntary) & (autonomic involuntary) nervous system.
Neurons
Specialized to conduct an electrical impulse
Sensory neurons
Carry an impulse away from the receptors to the spinal cord or directly to the brain
Motor neurons
Carry an impulse away from the brain to the muscles or glands and organs
Interneurons
Carry impulses across the spinal cord into the brain
- It links sensory and motor neurons
- Found in only the CNS
- shorter and slower than sensory and motor neurons (unmyelinated)
Dendrites
Receive stimuli either from the environment or other neurons
Cell body
- Contains the nucleus
* Receive info from dendrites and relays info to the axons
Axon
- carries nerve impulses away from the cell body
* Terminates in the synaptic junction
Myelinated fibre
- Myelin is a fatty protein sheath that covers the axons
- composed of Schwann Cells
- speeds up nerve impulses
Nodes of Ranvier
- Are the gaps between the myelin on the axon
- Nerve transmission occurs at the node’s only and skip over the insulated proportion of the axon
- Nerve impulse moves faster as the current jump from node to node
Neurilemma
- Found on myelinated neurons
* Neurilemma heals damaged neurons and works with the Schwan cells to regenerate damaged nerves
Resting potential (Polarized membrane)
- Nerve impulse cannot occur along a neuron unless it is polarized
- Ion pump transports 3 Na+ out for every 2 K+ that flows back in
- The inside is negative and outside is positive
- resting membrane potential is -70 mV
Depolarization
- Occurs when there is an influx of sodium flowing into the cell causing inside to be more positive and the outside now negative
- Na+ diffuses into the cell
Repolarization
- Open immediately after the sodium gates close
- Potassium will rush out because there’s a high concentration of potassium inside the cell and a low concentration outside the cell
- this process restores the membrane to resting
Hyperpolarization
•overshoot of potassium ions leaving the cell. Too much potassium flows out so to restore Na and Potassium pumps ions against their gradient to restore polarity
Threshold potential
•The minimum level of potential difference that is required to cause depolarization (-55 mV)
Synapse
•Movement of the impulse from the axon of one neuron to the dendrite of another neuron or a membrane of a gland or muscle
Synaptic cleft
•Is a space between the axon of one neuron (presynaptic neuron) and the dendrite of another neuron (postsynaptic neuron)
Excitatory synapse
•Cause depolarization of the next neuron (sodium influx)
Inhibitory synapses
- To prevent an action potential or depolarization of the next neuron
- Makes the postsynaptic membrane to become more permeable to Potassium resulting in hyperpolarization
- inhibitor or depressant
Summation
- Is accumulation of transmitter chemicals from two or more neurons
- Whether or not a postsynaptic neuron will fire depends on the effects of more than one presynaptic neuron
The reflex arc
- Spinal cord is responsible for reflexes
* Reflexes are quick involuntary, not learned, responses or actions that the body takes to protect itself from danger.
Neurotransmitters
• are chemical messengers that bind onto neurotransmitter receptors on postsynaptic neuron and alters the permeability of the membrane.
