Nakamura Human Anatomy Ch 12 Flashcards
(39 cards)
Central nervous system
Brain and spinal cord
Integrating and command center
Peripheral nervous system
- outside the the CNS
- consists of nerves extending from brain and spinal cord
- cranial nerves
- spinal nerves
- peripheral nerves link all regions of the body to the CNS
Sensory input
Sensory (afferent) signals picked up by sensory receptors
-carried by nerve fibers away from PNS to the CNS
Motor output
Motor (efferent) signals are carried away from the CNS
Inner ate all 3 types of muscles and glands (visceral motor)
-visceral meaning internal
Nervous tissue cells
Neurons: transmit electrical signals
Supporting cells (neuroglial cells) nonexcitable
-surround and wrap neurons
-certain types make myelin sheaths
Neuron
The human body contains billions of neurons
–Basic structural unit of the nervous system
•Specialized cells conduct electrical impulses along the plasma membrane
–Nerve impulse
–Action potential
•make electricity too
-large cell, three parts: axon, cell body, and dendrites
Neuron processes
Dendrites
Axon
Dendrites
-Transmit electrical signals toward the cell body
–Function as receptive sites
-project from the cell body
Axons
-Neuron has only one
–Impulse generator and conductor
–Transmits impulses away from the cell body
Also called nerve fiber (refers only to axon, not entire nerve cell)
-contains many branches
Axon hillock
Initial section of axon
Makes electrical impulse
Schwan cells
Surround axon
Form myelin sheath on axon (which acts as insulation)
Nerve impulse
-Generated at the initial segment(axon hillock) of the axon
–Conducted along the axon
–Releases neurotransmitters at axon terminals (send electricity from one neuron to another)
–Neurotransmitters – excite or inhibit neurons
–Neuron receives and sends signals
•“Conversation” with other neuron
Nervous system is divided into two basic divisions
Central nervous system (CNS)
Peripheral nervous system (PNS)
Synapses
•Site at which neurons communicate
•Signals pass across synapse in one direction (not reversible in chemical synapses)
•Presynaptic neuron
–Conducts signal toward a synapse (releases neurotransmitters)
•Postsynaptic neuron
–Transmits electrical activity away from a synapse
Types of synapses
-name based on location of synapse
Cell body: soma
-Axosomatic: an axon with a nerve cell body
-Axoaxonic: synaptic contact between the axon of one nerve cell and that of another
-Axodendritic: an axon with a dendrite of another neuron.
Exocytosis
A form of active transport where the cell transports molecules outside the cell
Used when sending neurotransmitters from one neuron to another
Microtubules contract and push synaptic vesicles
Signals carried by Neurons
- Signals (aka impulse, action potential)
- resting neuron: aka resting potential. No stimulation. membrane is polarized.
- polarized: intracellular is negatively charged, extracellular is positive
- once the neuron is stimulated results in depolarization (becomes less positive)
Cell membrane and its role in polarization
- phospholipid bilayer: selectively permeable
- bcuz of this DNA, ions, and proteins carry negative charge and are contained inside cell
Action potentials on Axons
Strong stimulus applied to the axon triggers
–Nerve impulse or action potential (starts at axon hillock)
•Membrane becomes negative externally
•Impulse travels the length of the axon (this process of depolarization is called conduction)
•Membrane repolarizes itself and returns to resting
Neurons classified by structure
- multipolar neuron: cell body has many dendrites extending from it, and an axon extending from it.
- bipolar neuron: contains a cell body with two long axons extending from either side p, with dendrites at the end of one of the axons
- unipolar neuron: cell body with a short single process and two branches extending from the process. Dendrites at one end of branch
Neurons classified by function
Sensory ((afferent)
Motor (efferent)
Variety of interneurons
-main difference is shape
-Purkinje cell, stellate cell, granule cell, and basket cell
–Located in the cerebellum
-Pyramidal cell – located in the cerebral cortex
Cerebrum
The largest portion of the brain, including practically all parts within the skull except the medulla, pons, and cerebellum.
Cerebrum now usually refers only to the parts derived from the telencephalon and includes mainly the cerebral hemispheres (cerebral cortex and basal ganglia
Supporting cells in the CNS
- 4 supporting cells of the CNS are called neuroglia or glial cells
- oligodendrocytes or oligodendroglia cells
- astrocytes
- ependymal cells
- microglia cells
