Anatomy & Physiology Nerves

The controlling system of the body with 3 functions

Sensory input

Integration

Motor output

gathering information from receptors

processing of info and decision making

signal to cause a response from an effector

the brain and spinal cord, the integration centers

outside the CNS, cranial nerves and spinal nerves. Lines of communication to and from CNS in 2 divisions:

Sensory (afferent) division

Motor (efferent) division

conveys info to the CNS from muscles and skin (somatic) and organs (visceral)

conveys impulses from the CNS to muscles and glands

Somatic Nervous System

Autonomic Nervous System

Sympathetic division

Parasympathetic division

motor neurons controlling skeletal muscle (voluntary)

motor neurons controlling smooth and cardiac muscles and glands (involuntary), in 2 divisions:

Sympathetic division

Parasympathetic division

Autonomic Nervous system

“fight or "flight” mobilization

Autonomic Nervous system “rest and digest” energy conservation Organization of the Nervous System

Neurons – excitable cells that carry nerve impulses

Neuroglia – the supporting cells

Astrocytes

Microglia

Ependymal cells

Oligodendrocytes

Satellite cells – surround neuron cell bodies, providing electoral insulation

Schwann cells (Neurolemmocytes) – form the myelin sheath insulations of PNS neurons

the functional units of nervous tissue, having the ability to conduct impulses

Longevity – last a lifetime

Amitotic – once mature, they cannot divide

High metabolic rate – consume large amounts of oxygen and nutrients

Soma (cell body)

Dendrites

Axon

Terminal branchesAxon terminalNucleus

Ganglion

Tract

Nerve

contains cytoplasm, nucleus, and organelles

many(100’s), short processes that relay input toward the soma

single process that relays impulses away from the soma

divisions at end of axon

bulbous ends of axons containing neurotransmitters

a cluster of neuron cell bodies in the CNS

a cluster of neuron cell bodies in the PNS

a cluster of axons in the CNS

a cluster of axons in the PNS

• A white, fatty wrapping of nerve fibers

• They insulate the fiber, increasing the speed of nerve impulses

Multipolar neurons – most common type, many dendrites and one axon

Bipolar neurons - very rare, one dendrite and one axon

Unipolar neurons – only one process (an axon) with receptive and secretory ends

Sensory (afferent) neurons – relay impulses to the CNS

Motor (efferent) neurons – relay impulses from the CNS to muscles and glands

Interneurons – found between sensory and motor, located within the CNS

relay impulses to the CNS

relay impulses from the CNS to muscles and glands

found between sensory and motor, located within the CNS

the potential energy generated by the separation of charges (Na+ and K+)

the flow of electrical charges from one point to another

(Na+ and K+ flowing across the cell membrane)

the hindrance to the flow of charges by a substance (cell membrane slows the flow of Na+ and K+)

membrane proteins whose hollow centers allow ions to diffuse across a cell membrane, creating electrical currents

those that are always open, allowing a leakage of ions

those that open in response to the binding of a specific chemical

those that open in response to changes in the membrane’s voltage (potential)

– the voltage measurement across a neuron’s cell membrane.• Membrane is Polarized - Cytoplasm shows negative charge of -70mV compared to outside of cell

a reduction in the membrane potential – the inside of the cell becomes less negative (or more positive)

an increase in the membrane potential – the inside of the cell becomes more negative

localized changes in membrane potential that travel and dissipate over short distances.

Large changes in membrane potential that travel over long distances and maintain their strength as they travel

Typically seen in the axons of neurons (called a nerve impulse) and in the sarcolemma of muscle fibers

1. Resting State

2.Depolarization

3.Repolarization

4.Hyperpolarization

5.Ion Redistribution

The movement of an action potential along the cell membrane (travels down the axon of a neuron, away from the soma)

the idea that an AP will either completely happen or not at all

– the voltage value that must be crossed to trigger an AP (typically near -55mV)

time during which an area of plasma membrane cannot generate, or is more difficult to generate, an action potential

Na+ and K+ channels are already open, making it impossible to generate a new AP

K+ channels are still open, making it more difficult to generate a newAP (higher threshold)

the junction between two neurons (or one neuron and a muscle/gland)

the information sender, releasing neurotransmitter from its axon terminal

the information receiver, receiving neurotransmitter, usually on its dendrites

the differing types of graded potentials seen in postsynaptic neurons

when the binding of neurotransmitter to the postsynaptic cell moves that cell’s membrane voltage toward threshold (encouraging an AP). Due to a net influx of Na+ ions.

when the binding of neurotransmitter to the postsynaptic cell moves that cell’s membrane voltage away from threshold (preventing an AP). Due to an influx of Cl- or efflux of K+.

the additive effect of many EPSP’s (since one EPSP cannot start an AP)

when EPSP’s occur in rapid sequence

when EPSP’s occur in close proximity

Neurotransmitter used at neuromuscular junctions and in the autonomic nervous system

group of neurotransmitters that regulate emotion and the biological clock, including dopamine, serotonin, norepinephrine, histamine

Excitatory – result in the depolarization of a neuron (EPSP)

Inhibitory – result in hyperpolarization(IPSP)

Some neurotransmitters are both, and depend on the receptor to which they bind