Nervous system Flashcards
What does the nervous system consist of?
-the central nervous system (CNS) = brain & spinal cord;
-the peripheral nervous system = all other parts of the nervous system.
What does the peripheral system consist of?
The afferent division: incoming sensory information from sensory receptors in the eyes, ears, etc.
The efferent division: outgoing motor information which travels to muscles and glands)
What does the efferent division consist of?
-the somatic nervous system (under voluntary control, such as the movement of leg muscles);
-the autonomic nervous system (under unconscious control, such as the movement of digestive muscles or glands).
What can the autonomic nervous system be split into?
Parasympathetic: rest and digest
Sympathetic: fight or flight
What are the three different neurons and their purpose?
sensory neurons (afferent neurons): sense and relay information to the CNS; e.g. thermoreceptors, photoreceptors, chemoreceptors; located in clusters called ganglia.
motor neurons (efferent neurons): relay information to effectors (muscles, organs, glands).
interneurons: link neurons within body; found in brain and spinal cord.
Function of dendrites, axon, myelin sheath, and the terminal branch
-receives messages from other cells
-passes messages away from the cell body to other neurons, muscles, or glands
-covers the axon of some neurons and helps speed neural impulses
-terminal branches: form junction of axon
What are glial cells?
the support cells of the nervous system. Glial cells nourish neurons, remove waste, provide immune defense, and support the nervous system. (Schwann cells)
Describe a reflex arc
A sensory receptor in the leg is connected to a sensory neuron. The sensory neuron relays a message to an interneuron in the spinal cord. The interneuron relays a message to a motor neuron. The motor neuron is connected to a muscle cell (effector) which contracts.
describe the characteristics of the polarized membrane/re-polarization
The interior of a nerve cell is negatively charged (-70mV).
This is called a resting membrane (polarized membrane).
Why?
- Negatively charged proteins inside the cell.
- K+ ions diffuse out faster than Na+ diffuse in via protein channels (gates).
- The Na+/K+ pump (a transport protein) moves 3 Na+ out for every 2 K+ in.
The depolarized membrane
-An action potential is triggered when the threshold potential is reached (for example when the nerve is stimulated).
-Na+ gates (transport proteins) open and Na+ ions rush into nerve cell by diffusion and charge attraction.
-This causes the membrane to be depolarized (charge reversal).
-Then K+ gates (transport proteins) open and K+ ions diffuse out of nerve cell.
-The action potential (voltage difference across nerve cell membrane) moves along the nerve membrane.
What are the specific steps of action potential?
Step 1. Na+ gates open when the nerve reaches its threshold. This causes charge reversal (depolarization).
Step 2. Na+ gates open farther along the axon and K+ gates open (repolarization).
Step 3. The action potential moves down the axon.
What is failed initiation?
Sometimes stimuli are not strong enough to produce an action potential.
What is hyperpolarization?
K+ gates open; extra + ions pumped out, making a larger electrical difference.
What is the refractory period and all or none response?
-the time during which the neuron cannot respond to a new signal.
-a neuron is either on or off; a stronger stimulus does not produce a stronger result, only the sending of more signals (higher frequency).
what is Saltatory Conduction:
Action potentials along myelinated axons travel faster because the action potential “jumps” from one node of Ranvier to the next node. The nodes of Ranvier are the gaps between the myelin sheath.
