Afferent Neurons

Neurons going toward the CNS

(sensory)

Efferent Neurons

Neurons going away from the CNS

(motor)

Central Nervous System (CNS)

Contains the brain and the spinal cord

Peripheral Nervous System (PNS)

Includes everything not included in the CNS (nerves that connect--cranial and spinal nerves.)

Somatic Nervous System

Have conscious control over; contains nerve fibers that send sensory information to the CNS, and motor nerve fibers that project to skeletal muscle.

Autonomic Nervous System

  No conscious control over; divided into three parts: Sympathetic NS, Parasympathetic NS and *Enteric NS.

Dermatome

Sensory distribution of nerve fibers in the skin.

Sensory nerves

conveys input from the external environment (touch, vision, etc.) and from the internal environment (blood pressure) to the CNS.

Motor nerves

           stimulates movement of muscles and makes glands secrete.

Sympathetic NS

controls fight or flight, emergencies;  increases HR and conrtactility, constricts blood vessels, stimulates adrenal medulla to secrete epinephrine... 

Parasympathetic NS

Keeps everything quiet and orderly; homeostasis.  Decreases HR and contractility, stimulates bladder emptying and defecation, constricts pupils and adjusts lenses.

Nerves

Bundles of neurons

Sympathetic neurons originate:

           in the thoracic and upper lumbar part of the spinal cord

Autonomic ganglion is close to spine, close to aorta

Parasympathetic neurons originate:

in the brain stem, sacral part of spinal cord

Autonomic ganglion is close to organ it supplies.

Dorsal roots

    contain the axons of sensory neurons and enter the spinal cord from the back.

ventral roots

         contain axons of motor neurons and leave the spinal cord from the front.

gray matter

nerve cell bodies

white matter

axons

Nissl body

     a structure visible in the cell body of a neuron by light microscopy that is composed of masses of ribosomes. 

protein synthesis occurs here.

somatic and autonomic reflexes

   Are involuntary, and only involve peripheral  nerves and the spinal cord, not the brain.

Myelin sheath

the cell membrane of a Schwann cell wrapped around and around an axon.

synapse

 where an axon of one neuron comes so close to the dendrites of the next neuron that it can send a signal across the space to reach it.

ligand

 a chemical that binds to a receptor on a cell membrane and causes some reaction in the cell.

Neurotransmitter used by somatic motor neurons and all pre-ganglionic autonomic neurons

Acetylcholine

    Neurotransmitter used by post-ganglionic autonomic neurons

Acetylcholine in parasympathetic neurons

Norepinephrine in sympathetic neurons

cauda equina

the dorsal and ventral roots of lumbar and sacral spinal nerves that remain inside the vertebral canalfor a long distance before the dorsal and ventral roots join and exit the vertebral canal as single nerves.

location of cell bodies of somatic motor neurons that leave the spinal cord

          in the anterior horns of the gray matter in the spinal cord

internal capsule

connects the motor cortex to the spinal cord

corpus callosum

connects the two cerebral hemispheres

Wernike's area

      where all somatosensory stimuli are interpreted so that you can understand what is happening around you.

two functions of astrocytes

recycle glutamate from synapse in the brain

 keep a store of glycogen to provide neurons glucose between meals

associative fibers

 located in the cerebral cortex; connect parts of the same hemisphere

action potential

          depolarization of the cell membrane followed by repolarization

oligodendrocytes

provide myelin sheaths for brain neurons

endorphin

neuropeptide that supresses pain

signal transduction

process by which binding stimulates the cells