A&P 1 chapter 11 (summer)

Sensory input

information gathered by sensory receptors about internal and external changes

Integration

Processing and interpretation of sensory input

Motor output

Activation of effector organs (muscles and glands) produces a response

Central nervous system (CNS)

Brain and spinal cord of dorsal body cavity

Peripheral nervous system (PNS)

Spinal nerves to and from spinal cord, cranial nerves to and from the brain

Sensory (afferent) division: Somatic sensory fibers

Convey impulses from skin, skeletal muscles, and joints to CNS

Sensory (afferent) division: Visceral sensory fibers

Convey impulses from visceral organs to CNS

Motor (efferent) division

Transmits impulses from CNS to effector organs (e.g., muscle and glands)

Motor (efferent): Somatic nervous system (voluntary)

conduct impulses from the CNS to skeletal muscle

Motor (efferent): Autonomic nervous system (involuntary)

Consists of visceral motor nerve fibers Regulates smooth muscle, cardiac muscle, and glands (sympathetic and parasympathetic)

CNS

Integrative and control centers

PNS

communication lines between the CNS and the rest of the body

Sensory (afferent) division

Conducts impulses from receptors to the CNS

Motor (efferent) division

Conducts impulses from the CNS to effectors (muscles and glands)

Somatic nervous system

Conducts impulses from the CNS to skeletal muscles

Autonomic nervous system

Conducts impulses from the CNS to cardiac muscle, smooth muscle, and glands

Sympathetic division

Mobilizes body systems during activity

Parasympathetic division

Conserves energy, promotes housekeeping functions during rest

Neurons (nerve cells)

Excitable cells that transmit electrical signals

Neuroglia (glial cells)

Small cells that surround and wrap delicate neurons

Astrocytes

Maintain the blood-brain barrier, regulate extracellular ion balance, recycle neurotransmitters

Microglial cells

Immune surveillance, phagocytosis, and inflammatory response

Ependymal cells

Circulate CSF, Form a barrier, Support neurogenesis

Oligodendrocytes

Forms CNS myelin sheaths (in thicker nerve fibers), increases conduction speed, and supports and stabilizes axons.

Satellite cells

Surround neuron cell bodies in the PNS, protection, and regulation

Schawnn cells

Forms the PNS myelin sheath (thicker nerve fibers) increases conduction speed and assists in nerve regeneration.

Nuclei

Clusters of neuron cell bodies in CNS

Ganglia

Clusters of neuron cell bodies in PNS

Tracts

bundles of Neuron processes in CNS

Nerves

bundles of neuron processes n PNS

Dendrites

Receive signals, conduct graded potentials, and increase communication surface area

Axons

Transmit action potentials, send information to targets, enable rapid communication

Myelin sheath

Protect and electrically insulate the axon, increasing the speed of nerve impulse transmission.

Myelinated fibers

A segmented sheath that surrounds most long or large-diameter axons.

Nonmyelinated fibers

Do not contain a sheath, conduct impulses more slowly

Myelination in the PNS

Formed by Schwann cells, wraps around the axon in a jelly roll fashion, one cell forms one segment of the myelin sheath.

Myelin sheath gaps (nodes of Ranvier)

Gaps between adjacent Schwann cells, sites where axon collaterals can emerge.

Myelin sheaths in the CNS

Formed by processes of oligodendrocytes, not whole cells,

White matter in CNS

Regions of the brain and spinal cord with dense collections of myelinated fibers

Gray matter

Mostly neuron cell bodies and nonmyelinated fibers.

Multipolar neurons

Three or more processes (one axon, others dendrites). Most common and major neuron type in CNS.

Bipolar

Two processes (one axon, one dendrite) Rare (ex: retina and olfactory mucosa)

Unipolar

One T-like process (two axons)

Unipolar (peripheral/distal) process:

associated with sensory receptor

unipolar (Proximal/central) process:

enters CNS

Sensory (almost all unipolar)

Transmit impulses from sensory receptors toward CNS, cell bodies are located in ganglia in PNS

Motor (multipolar)

Carry impulses from the CNS to effectors. Most cell bodies are located in the CNS (except some autonomic neurons)

Interneurons

Also called association neurons, lie between motor and sensory neurons, shuttle signals through CNS pathways. 99% of the boy’s neurons are interneurons.

Chemically gated (ligand-gated) channels

Open only with the binding of a specific chemical (ex: neurotransmitter)

Voltage-gated channels

Open and close in response to changes in membrane potential

Mechanically gated channels

Open and close in response to physical deformation of receptors, as in sensory receptors.

Resting membrane potential

-70mV

Depolarization

decrease in membrane potential, the inside of the membrane becomes less negative than the resting membrane potential

Hyperpolarization

increase in membrane potential, the inside of the membrane becomes more negative than the resting membrane potential.

continuous conduction

slow conduction that occurs in nonmyelinated axons

Saltatory conduction

occurs only in myelinated axons and is about 30x faster

Presynaptic neuron

neuron conducting impulses toward a synapse (send information)

Postsynaptic neuron

Neuron transmitting an electrical signal away from a synapse (receives information).

direct action

neurotransmitter binds directly to and opens ion channels

Indirect action

Neurotransmitter acts through intracellular second messengers.