Basics and Cells of the Nervous System

Franklin College A & P 1, Powerpoint 1 Basics, Neurons, and Glial Cells

Nervous system functions

maintains homeostasis and communicates via electrical and chemical signals

Sensory divison

receptors detect stimuli

Motor division

Effectors carry out responses

Somatic Motor Division

Skeletal muscles

Visceral Motor Division

Also called autonomic nervous system

Sympathetic Divison

Fight or flight; apart of the visceral motor division

Parasympathetic Division

Rest and digest; apart of the visceral motor division

Enteric Nervous System

within the GI tract; apart of the visceral motor division

Receptors sense stimuli, and then

PNS afferent neurons to interneurons in the CNS

CNS functions

processes info, relates it to past experiences, and determines the appropriate response

CNS sends

PNS efferent neurons to glands/muscles

Neurons

functional units

Dendrites

pick up signals

Neurosoma

cell body

Axon

carries signals to terminal

Synapse

converts electrical signals to chemical signals using neurotransmitters

Nodes of Ranvier

unmyelinated areas allowing for faster electrical signal conduction

Neurons are

structurally classified based on how processes emerge from the neurosoma

Multipolar

one axon, many dendrites

Bipolar

one axon, one dendrite

Unipolar

one process leading away from the neurosoma

Neurons are functionally classified as 

Sensory/afferent neurons, interneurons, and motor/efferent neurons

Neuromodulators

alter the strength of transmission between neurons by affecting how much neurotransmitter is produced and released

Neuromodulators examples

Dopamine, serotonin, acetylcholine, histamine, and norepinephrine

Neurohormones

Hormones produced by neurons that are secreted into circulation

Neurohormones examples

the releasing hormones produced by the hypothalamus, oxytocin, and vasopressin

Neurotransmitters are heavily involved in

early development

Excitatory neurotransmitters

increase electrical excitability by helping to instigate action potentials

Inhibitory Neurotransmitters

decrease electrical excitability to prevent the propagation of action potentials

Monoamines

one amino group connected to an aromatic ring via a 2 carbon chain

Catecholamines

Have a benzene ring, 2 hydroxyl groups, an intermediate ethyl chain, and a terminal amine group

Synaptic Cleft has

enzymes for breaking down neurotransmitters & has helper cells to take up excess neurotransmitter

Action Potentials

trigger chain reactions that create a nerve signal

Unmyelinated neurons have

continuous conduction of action potential

Myelinated neurons have

saltatory conduction of action potentials

Presynaptic neurons releases

Neurotransmitters into synaptic cleft which are picked up by receptors on postsynaptic neurons which depolarizes the cell and generates action potential

Neuroglia

support nervous system functions

PNS Neuroglia include

Satellite cells and schwann cells

Satellite Cells

insulate neurons and regulate PNS environment 

Schwann Cells

create myelin sheaths for neurons and are critical in regeneration and healing of damaged nerve fibers

CNS Neuroglia include

Astrocytes, ependymal cells, microglia, and oligodendrocytes

Astrocytes function

Scaffolding for nervous tissue, maintain BBB and adjust blood flow, secrete growth factors for neuron growth and synapse formation, maintain extracellular environment, supply nutrients for neurons, and glial scarring

Ependymal Cells

Produce/circulate cerebrospinal fluid

Microglia

phagocytic cells; immune-like functions

Oligodendrocytes

Create myelin sheaths for neurons