Ch 11.1 Structures and Processes of the Nervous System Flashcards
What is homeostasis?
A state of relative stability, maintaining the body with a narrow range of conditions
Describe the central nervous sytem
The CNS consists of the brain and spinal cord, and integrates and processes information sent by nerves
Describe the peripheral nervous system
The PNS includes nerves that carry sensory messages to the CNS and nerves that send information from the CNS to the muscles and glands
What type of muscle(s) does the somatic system control?
Voluntary muscles- skeletal muscles
What kind of muscle(s) does the autonomic system control?
Involuntary muscles- smooth and cardiac muscles
What types of cells is the nervous system composed of?
Neurons and cells that support the Neurons which are called glial cells
What are glial cells?
Non conductive cells which nourish the neurons, removes their wastes, and defend against infection
What are nerves?
Individual neurons organized into tissues
Describe the structure of the neuron
Dendrites, cell body, axon, and branching ends
Define a dendrite
Short branching terminals that receive nerve impulses from other neurons or sensory receptors and relay the nerve impulse to the cell body
What is a cell body?
Contains the nucleus and is the site of the cell’s metabolic reactions
What does the axon do?
It conducts impulses away from the cell body
What does the myelin sheath do?
It protects the neurons and speeds the rate of nerve transmission. PROTECTS AGAINST THE LOSS OF IONS
What is the function of the neurilemma?
Promotes the repair and regeneration of axons
What is a simple reflex?
UNCONDITIONED response to stimuli
What is a conditioned reflex?
A learned and practiced reflex
What is a ganglion?
A cluster of sensory cell bodies found along the spinal cord
What is a nerve impulse and what steps does it involve?
An electrochemical event that uses cellular energy to generate a series of action potentials. It involves resting potential, depolarization, and repolarization
Describe the resting membrane potential
An unequal distribution of ions across neural membrane. When not stimulated, it is more positive on the outside
3 factors
- na K pump moves 3 sodiums out and 2 K in using ATP. High Na outside, high k inside
- negative proteins and Cl remain inside
- the membrane is more permeable to K( k diffuses out faster than Na diffuses in)
Describe depolarization
Stimulus causes na gates to open and na rapidly diffuses into cell. Membrane has reverse polarity due to excessive + ions inside (40mV). Depol causes na gates to close and K gates to open
Define threshold
Min level of stimulus required to produce an action potential
Describe repolarization
K leaves cell by diffusion
Restores original polarity (+ outside, -inside)
What is hyperpolarization
When the intracellular fluid becomes more negative than before (-90mV)
What is a refractory period
Time it takes to repolarize after an action potential
No new impulse can be initiated until after the original resting is re-established
What is a saltatory conduction?
When actions potentials are forced to “jump” from one mode of ranvier to the next due to the myelin sheath
What is a synapse?
Where the axon of one neuron meets the
dendrite of another neuron/effector
Describe the process of synaptic transmission
- Nerve impulse arrives at the axon terminal
- Impulse causes synaptic vesicles to move to the membrane and fuse with it releasing neurotransmitter to the synapse (exocytosis) 3.neurotransmitters defuse across to the dendrite
- Neurotransmitters bind to the receptors and initiate a nerve impulse
Describe excitatory and inhibitory
Excitatory- opens na gates (depolarize)
Inhibitory- opens k gates (hyperpolarize)
Define neuromuscular junction
Modified synapse where a motor neuron meets a muscle cell
What is summation?
When 2+ neurons must both fire in order to depolarize the same postsynaptic neuron
What is acetylcholine?
Is a neurotransmitter that crosses a neuromuscular junction. It excites the muscle cell membrane, causing depolarization and contraction of the muscle fibre
What enzyme breaks down acetylcholine?
Cholinesterase
