U2L3: Peripheral Nervous System and Neurons Flashcards
What two systems make up the Peripheral Nervous System?
The Autonomic system and the Somatic system.
What is the Somatic system?
Usually voluntary contractions of skeletal muscles (except shivering, reflexes etc.)
What is the Autonomic system and what 2 things is it divided into?
Controls mainly involuntary processes: digestion, sweat secretion, circulation of blood, smooth muscle contractions
Divided further into sympathetic & parasympathetic
Sympathetic: dominates in situations involving danger, stress, excitement, physical activity to increase heartbeat, raise bp, induce sweating, dilate pupils
Parasympathetic: dominates during quiet, low-stress situations to conserve energy so heartbeat is slowed, bp is lowered etc.
What is a Neuron?
A nerve cell capable of conducting nerve impulses
What do the Dendrites do?
They receive electrical stimulation from other neurons
What does the Axon do?
It carries nerve impulse away from cell body
What do the axon terminals do?
they transmit electrical stimulation to other neurons
What are Sensory Neurons?
E.g. Those in skin
they receive sensory information & transmit the information (as a nerve impulse) to the CNS (brain & spinal cord)
What are Motor Neurons?
Take information from CNS to effectors (e.g. Muscles, glands, other organs)
What are Interneurons?
Link sensory & motor neurons
What do Oligodendrocytes do (kind of non-neural cell)
they form the myelin sheaths of axons in CNS
What do Schwann cells do?
They form a myelin sheath around each axon in PNS
What is the Myelin Sheath (composition, function)?
Composed of 80% lipid + 20% protein Protects the axon and helps speed up the conduction of nerve impulses
How are nerve signals transmitted?
Neurons connect to one another and transmit signals or impulses via electrical and chemical messengers
What is Membrane potential?
Animal cells have a specific charge across the plasma membrane; -ve on inside and +ve on outside
Charge separation produces voltage (electrical potential diff) across membrane potential and the cell must expend ENERGY to keep this charge.
The inside of the neuron is negatively charged relative to the outside
What is the Na-K pump?
Na-K pump is responsible for maintaining the charge across the membrane (ATP is used for this process)
Naturally Na+ is in high concentration outside and K+ in high concentration inside
The pump will work against the [C] gradient by pumping out 3 Na+ while pumping in 2 K+
This causes the inside of the cell to become less positive and eventually more -ve
What is Action Potential?
Large stimulus reaches neuron cell and changes the membrane voltage. This causes a “domino” effect down the neuron where the electrical charge moves down the axon jumping from node to node. When the electrical charge reaches the axon terminals, chemicals called neurotransmitters are released to the next neuron, which initiates the action potential and so on…
